JP2017134997A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary battery excellent in charge/discharge characteristics under high load while maintaining a high energy density, having a positive electrode, a negative electrode, a separator and a non-aqueous electrolytic solution, and the positive electrode. Uses a positive electrode material in which a positive electrode mixture layer containing a positive electrode active material is coated on a positive electrode current collector, and the surface of the particles of the positive electrode active material is coated with an Al-containing oxide. The Al-containing oxide has an average coating thickness of 5 to 50 nm, the positive electrode and the negative electrode each have a positive electrode current collecting tab and a negative electrode current collecting tab, and are laminated with the separator interposed therebetween and are spirally wound. The positive electrode current collecting tab is arranged at a position of 30 to 70% of the distance between one end of the positive electrode mixture layer and the other end thereof, and the negative electrode current collecting tab is disposed at the negative electrode. A non-aqueous electrolyte secondary battery is provided which is arranged at an end portion in the length direction of the non-aqueous electrolyte secondary battery. [Selection diagram] Figure 1

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  Non-aqueous electrolyte secondary batteries have been widely deployed not only for consumer devices such as mobile phones and laptop computers but also for industrial applications such as electric bicycles and power storage because of their high energy density. In recent years, the demand for drones and robots has been greatly increasing. In applications related to these drones and robots, not only high energy density but also high input / output performance is required. In particular, it is necessary to improve energy density per weight and load characteristics during discharge. ing. Furthermore, suppression of heat generation during large current discharge is also an important issue.

  Patent Document 1 discloses that the negative electrode has two or more current collecting tabs to improve the load characteristics of the battery. In Patent Document 2, an uncoated portion of the positive electrode active material is provided in the central portion of the positive electrode plate in the long direction, and the current collecting resistance of the positive electrode plate can be lowered by connecting the positive electrode lead to the uncoated portion. It is disclosed.

JP 2014-132516 A JP 2008-234855 A

However, when a plurality of electrode tabs are provided as in Patent Document 1, the weight energy density is lowered and the working efficiency is lowered. Moreover, by making it like patent document 1 and 2, the load characteristic of a battery is improved and the heat_generation | fever at the time of large current discharge is also suppressed to some extent. However, it is difficult to completely suppress the temperature rise of the electrode due to a large current flowing at a time with high load charge / discharge, and the electrode is damaged at high temperatures and deteriorates.
Therefore, the present invention has been made to solve such a problem, and an object thereof is to provide a nonaqueous electrolyte secondary battery excellent in charge / discharge characteristics under a high load while maintaining a high energy density. It is.

  According to an embodiment of the present invention, a non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The positive electrode includes a positive electrode composite containing a positive electrode active material on a positive electrode current collector. An agent layer is applied, and a positive electrode material in which surfaces of the positive electrode active material particles are coated with an Al-containing oxide is used, and an average coating thickness of the Al-containing oxide is 5 to 50 nm, The positive electrode and the negative electrode have a positive electrode current collecting tab and a negative electrode current collecting tab, respectively, and are stacked via the separator and wound in a spiral shape, and the positive electrode current collecting tab is in the length direction of the positive electrode The positive electrode mixture layer is disposed at a position of 30 to 70% of the distance from one end to the other end of the positive electrode mixture layer, and the negative electrode current collecting tab is disposed at an end portion in the length direction of the negative electrode It is characterized by being.

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte secondary battery excellent in the high load charge / discharge characteristic can be provided, maintaining a high energy density.

The positive electrode which is an example of the embodiment of this invention is represented. The negative electrode which is an example of the embodiment of this invention is represented. The nonaqueous electrolyte secondary battery which is an example of the embodiment of this invention is represented. The positive electrode which is a comparative example of this invention is represented. The negative electrode which is a comparative example of this invention is represented.

  In an electrode body in which a long positive electrode and negative electrode are wound in a spiral shape, the current concentrates on the current collecting tab via the current collector during charging and discharging, but at this time, the longer the electron travel distance, the higher the resistance. , Easy to fever. In the present invention, the positive electrode current collecting tab is disposed at substantially the center of the positive electrode in the length direction (perpendicular to the winding axis direction), thereby shortening the electron moving distance to reduce resistance and suppressing heat generation. Thereby, the temperature rise in the battery due to charging / discharging at a high load can be suppressed.

  Further, the positive electrode uses a positive electrode material in which the surface of the positive electrode active material particles is coated with an Al-containing oxide. Even if the positive electrode current collector tab is arranged in the center in the length direction, it is difficult to completely suppress the temperature rise of the electrode due to a large current flowing at a time with high load charge / discharge. Charging / discharging characteristics under high load are reduced. Therefore, when the particle surface of the positive electrode active material is coated with an Al-containing oxide, it is possible to suppress these characteristic deteriorations.

[Positive electrode]
The non-aqueous secondary battery of the present invention has a positive electrode and a negative electrode that are stacked via a separator and wound in a spiral shape. Therefore, both the positive electrode and the negative electrode and separator described later are elongated in the direction perpendicular to the winding axis direction. Is used.

  FIG. 1 shows a positive electrode according to an example of the present invention. In the positive electrode 1 of the present invention, a positive electrode mixture layer 12 is provided on one or both sides of a long positive electrode current collector 11, and the positive electrode mixture layer 12 uses a positive electrode active material, a binder, a conductive auxiliary agent and the like as a solvent. The positive electrode mixture slurry dispersed in is coated on the positive electrode current collector 11 and dried. At this time, a portion without the positive electrode mixture layer for arranging the positive electrode current collecting tab 13, that is, an uncoated portion N is provided in the central portion C in the length direction of at least one surface of the positive electrode current collector 11. In the uncoated portion N, the positive electrode current collector tab 13 is disposed by means such as ultrasonic welding or resistance welding so as to be electrically connected to the positive electrode current collector 11. In FIG. 1, a positive electrode mixture layer is provided on both surfaces, and a positive electrode current collecting tab is disposed on one uncoated portion of the uncoated portions on both surfaces.

  In the case of a positive electrode in which the length of the positive electrode mixture layer is the same and the positive electrode current collecting tab is provided only at one end in the length direction, the maximum electron moving distance is from one end of the positive electrode mixture layer in the length direction. The distance to the other end. On the other hand, in the embodiment of the present invention, the maximum electron movement distance is about half the total length of the positive electrode mixture layer. That is, according to the aspect of the present invention, the resistance can be reduced by shortening the moving distance of electrons. Therefore, it is possible to suppress heat generation even when charging / discharging with a large current.

The position T of the positive electrode current collecting tab 13 is a distance from one end of the positive electrode mixture layer to the other end of the positive electrode current collector in the length direction of the positive electrode (the coating length of the positive electrode mixture layer is different on both sides) In this case, the longer distance is adopted, which is arranged between 30% and 70% of the distance from S to E in FIG. More preferably, it is 40 to 60%.
The uncoated portion may be provided at the center so that the positive electrode current collecting tab 13 can be disposed at the above position.

  Only one positive electrode current collecting tab or a plurality of positive electrode current collecting tabs may be arranged at the center in the length direction. Since the weight energy density can be improved by reducing the weight of the member that does not contribute to charging / discharging in the battery, it is preferable to arrange only one member.

Cross-sectional area per one positive electrode current collector tabs is preferably 0.1 to 1.5 mm ^2, in particular 0.15～1.0Mm ² is preferred. This is because if it is smaller than 0.15 mm ² , the resistance derived from the positive electrode current collecting tab increases, and it is difficult to obtain high load characteristics even if the current collecting tab is increased. This is because if it exceeds 1.0 mm ^2, the width and thickness of the current collecting tab become too large, which causes problems in productivity such as weldability.

<Positive electrode active material>
The positive electrode active material of the present invention uses a positive electrode material in which the surface of the positive electrode active material particles is coated with an Al-containing oxide.

  By arranging the positive electrode current collecting tab at the above-mentioned position, it is possible to suppress the heat generation of the positive electrode, but it is difficult to completely suppress the heat generation when repeated charging and discharging under high load, the temperature inside the battery Rises to about 80 ° C. Under such a temperature, the side reaction between the non-aqueous electrolyte and the particle surface of the positive electrode active material, that is, gas generation and deposition of reaction products are accelerated. Due to gas generation, the facing distance between the positive electrode and the negative electrode becomes non-uniform, which deteriorates the charge / discharge characteristics under high load. In addition, when a large amount of reaction product is deposited on the positive electrode active material, the charge / discharge reaction on the surface of the active material is remarkably inhibited, and the high input / output performance is lowered.

  Therefore, in the present invention, by using a positive electrode material in which the particle surface of the positive electrode active material is coated with an Al-containing oxide, gas is generated by a side reaction between the particle surface and the electrolyte when the temperature in the battery rises. And the deposition of reaction products can be suppressed, and deterioration of high input / output performance can be suppressed even when used repeatedly.

In the present invention, the positive electrode active material whose surface is coated with an Al-containing oxide can solve the problems of the present application as long as it is a positive electrode active material that causes a side reaction with a non-aqueous electrolyte at a high temperature. For example, there are lithium cobaltate, lithium nickelate, nickel cobalt aluminum-containing composite oxide, nickel manganese cobalt-containing composite oxide, and the like.
Among them, it is preferable to employ lithium cobaltate that is general-purpose as a lithium ion battery and capable of increasing the capacity.

When lithium cobaltate is used as the positive electrode active material contained in the positive electrode material, the lithium cobaltate includes Co and Mg, at least one element M selected from the group consisting of Ni, Mn, Ti and Al, and further When other elements that may be contained are grouped into the element group Mm, it is preferable to use those represented by the composition formula Li _{1 + n} MmO ₂ (−0.05 ≦ n ≦ 0.05).

  When the positive electrode material has a specific particle size distribution by combining particles having a specific average particle size, a side reaction with the electrolyte due to cracking of the positive electrode material particles in the manufacturing process of the positive electrode using the positive electrode material This is preferable because the effect of coating with the Al-containing oxide can be more satisfactorily exhibited. In particular, it is preferable to include the positive electrode material (a) and the positive electrode material (b) having an average particle diameter smaller than that of the positive electrode material (a) because a specific particle size distribution is easily obtained.

  The positive electrode active material of the positive electrode material (a) having a specific average particle size is lithium cobaltate (A), and the positive electrode active material of the positive electrode material (b) having a smaller average particle size than the positive electrode material (a) is lithium cobaltate ( B) will be described below.

Lithium cobaltate (A) is composed of Co, Mg, Zr, element M ¹ , and other elements that may be further contained in element group Ma to form a composition formula Li _{1 + x} MaO ₂ (−0. 05 ≦ x ≦ 0.05). The lithium cobalt oxide (B) has a composition formula Li _{1 + y} MbO ₂ (−0...) When Co, Mg, the element M ² , and other elements that may further be contained are combined into an element group Mb. It is preferable to use one represented by 05 ≦ y ≦ 0.05).

In the lithium cobalt oxide (A) and lithium cobaltate (B), Mg, elements M ¹ and the element M ² increases the stability in the high voltage region of the lithium cobalt oxide (A) and lithium cobaltate (B), It has an action of suppressing elution of Co ions, and also has an action of improving the thermal stability of lithium cobaltate (A) and lithium cobaltate (B). Furthermore, the element M ¹ and the element M ² also have an effect of improving the continuous charge characteristics of the battery (characteristics in which a minute short circuit is generated for a very long time even if the battery is continuously charged).

  In lithium cobaltate (A) and lithium cobaltate (B), the amount of Mg is such that the atomic ratio Mg / Co with Co is 0.002 or more from the viewpoint of more effectively exerting the above-described action. Preferably, it is 0.005 or more. Further, in the lithium cobaltate (A), the amount of the element M1 is preferably such that the atomic ratio M1 / Co with Co is 0.001 or more from the viewpoint of more effectively exerting the above-described action. More preferably, it is 003 or more. In the lithium cobaltate (B), the amount of the element M2 is preferably such that the atomic ratio M2 / Co with Co is 0.001 or more from the viewpoint of more effectively exerting the above action. More preferably, it is 003 or more.

  However, if the amounts of Mg, element M1, and element M2 in lithium cobaltate (A) and lithium cobaltate (B) are too large, the amount of Zr (in the case of lithium cobaltate (A)) and Co will be too small. Therefore, there is a possibility that the effects of these cannot be sufficiently secured. Therefore, in lithium cobaltate (A) and lithium cobaltate (B), the amount of Mg is preferably such that the atomic ratio Mg / Co with Co is 0.03 or less, and 0.015 or less. More preferred. Further, in the lithium cobaltate (A), the amount of the element M1 is such that the atomic ratio M1 / Co with Co is preferably 0.03 or less, and more preferably 0.015 or less. Further, in the lithium cobaltate (B), the amount of the element M2 is such that the atomic ratio M2 / Co with Co is preferably 0.03 or less, and more preferably 0.015 or less.

In lithium cobaltate (A), Zr adsorbs hydrogen fluoride which can be generated due to F-containing lithium salt (for example, LiPF ₆ ) contained in the non-aqueous electrolyte, and lithium cobaltate (A) It has the effect | action which suppresses deterioration.

If some water is inevitably mixed in the non-aqueous electrolyte used in the non-aqueous secondary battery, or if moisture is adsorbed to other battery materials, the non-aqueous electrolyte contains F. It reacts with a lithium salt (for example, LiPF ₆ ) to produce hydrogen fluoride. When hydrogen fluoride is generated in the battery, the action causes deterioration of the positive electrode active material.

  However, when lithium cobalt oxide (A) is synthesized so as to also contain Zr, Zr oxide is deposited on the surface of the particles, and this Zr oxide adsorbs hydrogen fluoride. Therefore, deterioration of lithium cobalt oxide (A) due to hydrogen fluoride can be suppressed.

  In addition, when Zr is included in the positive electrode active material, the load characteristics of the battery are improved. The lithium cobaltate (A) contained in the positive electrode material has an average particle size larger than that of the lithium cobaltate (B), but generally, when a positive electrode active material having a large particle size is used, the load characteristics of the battery tend to deteriorate. . Therefore, among the positive electrode active materials constituting the positive electrode material according to the present invention, lithium cobaltate (A) having a larger average particle diameter contains Zr. On the other hand, lithium cobaltate (B) may contain Zr or may not contain it.

  In the lithium cobaltate (A), the amount of Zr is preferably such that the atomic ratio Zr / Co with Co is 0.0002 or more, and 0.0003 or more from the viewpoint of better exerting the above-described action. More preferably. However, if the amount of Zr in the lithium cobalt oxide (A) is too large, the amount of other elements decreases, and there is a possibility that the effects of these cannot be sufficiently ensured. Therefore, the amount of Zr in lithium cobaltate (A) is preferably such that the atomic ratio Zr / Co with Co is 0.005 or less, and more preferably 0.001 or less.

Lithium cobaltate (A) and lithium cobaltate (B) include Li-containing compounds (lithium hydroxide, lithium carbonate, etc.), Co-containing compounds (cobalt oxide, cobalt sulfate, etc.), Mg-containing compounds (magnesium sulfate, etc.), Zr containing compounds (such as zirconium oxide) and the element M ¹ and the element M ² which contained compound (oxide, hydroxide, sulfate, etc.) can be mixed, synthesized, for example, by firing the raw material mixture. In order to synthesize lithium cobaltate (A) and lithium cobaltate (B) with higher purity, a composite compound (hydroxide, oxide) containing Co, Mg, and Zr, and further, element M1 and element M2 Etc.) and a Li-containing compound or the like are mixed, and this raw material mixture is preferably fired.

  The firing conditions of the raw material mixture for synthesizing lithium cobaltate (A) and lithium cobaltate (B) can be, for example, 800 to 1050 ° C. for 1 to 24 hours, but once lower than the firing temperature. It is preferable to carry out preliminary heating by heating to (for example, 250 to 850 ° C.) and holding at that temperature, and then raising the temperature to the firing temperature to advance the reaction. Although there is no restriction | limiting in particular about the time of preheating, Usually, what is necessary is just to be about 0.5 to 30 hours. The atmosphere during firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (such as argon, helium, or nitrogen) and oxygen gas, or an oxygen gas atmosphere. The oxygen concentration (volume basis) is preferably 15% or more, and more preferably 18% or more.

In the positive electrode material, the surface of lithium cobalt oxide (A) particles is coated with an Al-containing oxide, and the surface of lithium cobalt oxide (B) particles is coated with an Al-containing oxide. The positive electrode material (b) is preferably contained. [For example, Al-containing oxide is present in 90 to 100% or more of the total area of the surface of lithium cobaltate (A) and lithium cobaltate (B) particles]. Examples of Al-containing oxides covering the surfaces of lithium cobaltate (A) and lithium cobaltate (B) particles include Al ₂ O 3, AlOOH, LiAlO ₂ , LiCo _1-w Al _w O 2 (provided that 0.5 < w <1) etc. are mentioned, Only 1 type of these may be used and 2 or more types may be used together. Incidentally, for example, when the surface of the lithium cobalt oxide (A) or lithium cobalt oxide (B) were coated with _Al 2 _{O 3} in the later-described method, in _Al 2 _{O 3,} lithium cobalt oxide (A) or lithium cobalt oxide ( B), a coating is formed in which a part of the Al-containing oxide containing elements such as Co, Li, and Al is mixed, but the lithium cobalt oxide (A) according to the positive electrode material (a) constituting the positive electrode material A film formed of an Al-containing oxide covering the surface and a film formed of an Al-containing oxide covering the surface of the lithium cobalt oxide (B) according to the positive electrode material (b) are films containing such components. There may be.

  The average coating thickness of the Al-containing oxide in the particles constituting the positive electrode material is 5 nm or more and 15 nm or more from the viewpoint of satisfactorily suppressing the reaction between the positive electrode active material related to the positive electrode material and the nonaqueous electrolytic solution. Is preferred. In addition, from the viewpoint of suppressing deterioration in load characteristics of the battery due to the Al-containing oxide inhibiting lithium ions from entering and exiting the positive electrode active material during charge and discharge of the battery, Al in the particles constituting the positive electrode material according to the present invention The average coating thickness of the contained oxide is 50 nm or less, and more preferably 35 nm or less.

  The “average coating thickness of the Al-containing oxide in the particles constituting the positive electrode material” as used herein refers to a cross section of the positive electrode material obtained by processing by the focused ion beam method using a transmission electron microscope. Among positive electrode material particles observed at a magnification of 500 × 500 nm, a particle whose cross-sectional size is within the average particle diameter (d50) ± 5 μm of the positive electrode material is arbitrarily selected for 10 visual fields, Mean thickness value (number average value) calculated for all thicknesses (thickness at 100 locations) obtained by measuring the thickness of the Al-containing oxide film at any 10 locations for each field of view. doing.

In the positive electrode material according to the present invention, the specific surface area (specific surface area of the entire positive electrode material) is preferably 0.4 m ² / g or less from the viewpoint of satisfactorily suppressing the reaction between the positive electrode active material and the non-aqueous electrolyte, Preferably it is 0.3 m ² / g or less. Further, from the viewpoint of suppressing the deterioration of load characteristics of the battery without inhibiting the lithium ion in and out of the positive electrode active material during charging and discharging of the battery, the specific surface area of the particles constituting the positive electrode material according to the present invention is 0.1 m. ^It is preferably ² / g or more, more preferably 0.2 m ² / g or more.

  When the surface of the positive electrode active material particles constituting the positive electrode material is coated with an Al-containing oxide or the Zr oxide is deposited on the surface of the positive electrode active material particles, the surface of the positive electrode material is usually used. When the properties of the Al-containing oxide film covering the surface of the positive electrode active material particles are good, in addition to making the positive electrode material have a relatively large particle size, the specific surface area increases. It is possible to realize such a small specific surface area.

  The positive electrode material is formed by coating the surface of lithium cobalt oxide (A) particles with an Al-containing oxide and having an average particle diameter of 1 to 40 μm and lithium cobalt oxide (B) particles. When the surface is coated with an Al-containing oxide, the average particle diameter is 1 to 40 μm, and at least the positive electrode material (b) having an average particle diameter smaller than that of the positive electrode material (a), the positive electrode The material will have two or more peaks in a particle size range of 1-40 μm in a volume-based particle size distribution. As used herein, “having two or more peaks in the particle size range of 1 to 40 μm” means that the particle size of the peak top of two or more peaks is in the range of 1 to 40 μm. Meaning that, for example, two or more peaks are completely separated, or two or more peaks are combined into one or more peaks, and the peak top is separated into two or more. And the tail of each peak may exist outside the particle size range of 1 to 40 μm.

This is because, in all particles of the positive electrode material, in the particle size distribution, particles belonging to a larger particle size side peak, particles belonging to a smaller particle size side peak, that is, a group of particles having a relatively large particle size This means that a particle group having a smaller particle size than these particle groups is included.
When the positive electrode material has the above particle size distribution, when the positive electrode mixture layer or the positive electrode mixture pellet is formed, the positive electrode material with a small particle diameter enters the gap between the large particle diameter positive electrode material, In the press treatment, the stress applied to the positive electrode mixture layer and the positive electrode mixture pellet can be dispersed throughout. Thereby, excessive stress is not easily applied to the individual positive electrode material particles during the press treatment, and the positive electrode material particles are favorably suppressed from cracking. Therefore, during the production of the positive electrode, the generation of a new surface due to cracking of the positive electrode material particles (occurrence of a portion not coated with the Al-containing oxide) is suppressed. It can be exhibited well and is preferable.

  As the particle size distribution of the positive electrode material, the volume-based particle size distribution has one or more peaks in the particle size range of 1 to 15 μm and one or more peaks in the particle size range of 15 to 40 μm. And at least one peak among the peaks existing in the particle size range of 15 to 40 μm is at least one peak among the peaks existing in the particle size range of 1 to 15 μm. It is preferable that it is larger than the particle size of the top. When the positive electrode material has such a particle size distribution, the effect of suppressing the cracking of the positive electrode material particles in the production process of the positive electrode becomes better, and the specific surface area of the positive electrode material can be easily adjusted to the above value. It becomes.

  The positive electrode material is composed of large particles [positive electrode material (a)] having an average particle diameter of 24 to 30 μm and small particles [positive electrode material (b)] having an average particle diameter of 4 to 8 μm. It is preferable that the ratio of the said large particle is 75-90 mass%. If the positive electrode material has such a configuration, the particle size distribution of the entire positive electrode material can be adjusted as described above.

  The particle size distribution of the positive electrode material in the present specification means a particle size distribution obtained by a method for obtaining an integrated volume from particles having a small particle size distribution using a microtrack particle size distribution measuring apparatus “HRA9320” manufactured by Nikkiso Co., Ltd. . In addition, the average particle diameter of the positive electrode material and other particles in the present specification is a value of 50% diameter in the volume-based integrated fraction when the integrated volume is obtained from particles having a small particle size distribution using the above-described apparatus. (D50) is meant.

  The positive electrode material is, for example, a surface of a positive electrode active material having the same composition as lithium cobalt oxide (A) or lithium cobalt oxide (B) is coated with an Al-containing oxide, and the average particle size is positive electrode material (a). 1 type, or 2 or more types of positive electrode materials which are the values between and positive electrode material (b) may be included.

In order to coat the surface of positive electrode active material particles such as lithium cobaltate (A) and lithium cobaltate (B) with an Al-containing oxide to form the positive electrode material, for example, the following method can be employed. pH and 9-11, in aqueous solution of lithium hydroxide a temperature of 60-80 ° C., and stirred to put a positive electrode active material particles are dispersed, wherein the Al _{(NO 3)} and 3 · 9H ₂ O, pH Ammonia water is added dropwise to suppress fluctuations in the amount of Al (OH) ₃ coprecipitate, which is deposited on the surface of the positive electrode active material particles. Thereafter, the positive electrode active material particles having the Al (OH) ₃ coprecipitate adhered thereto are taken out from the reaction solution, washed, dried, and then heat-treated to coat the surface of the positive electrode active material particles with an Al-containing oxide. To form the positive electrode material. The heat treatment of the positive electrode active material particles to which the Al (OH) ₃ coprecipitate is adhered is preferably performed in the atmosphere, and the heat treatment temperature is preferably 200 to 800 ° C. and the heat treatment time is preferably 5 to 15 hours. . When the surface of the positive electrode active material particles is coated with an Al-containing oxide by this method, the Al-containing oxide as a main component constituting the coating is changed to Al ₂ O ₃ or AlOOH by adjusting the heat treatment temperature. Or LiAlO ₂ or LiCo _1-w Al _w O ₂ (where 0.5 <w <1).

  The positive electrode according to the non-aqueous secondary battery of the present invention has, for example, a structure having a positive electrode mixture layer containing a positive electrode active material (the positive electrode material), a conductive additive and a binder on one side or both sides of a current collector. Things. Further, depending on the form of the battery, a pellet (positive electrode mixture pellet) obtained by molding a positive electrode mixture containing a positive electrode active material (the positive electrode material), a conductive additive, a binder, and the like can be used as the positive electrode.

  As the positive electrode active material, other positive electrode active materials may be used in combination with the positive electrode material. Other positive electrode active materials that can be used in combination with the positive electrode material include those conventionally used in non-aqueous secondary batteries such as lithium ion secondary batteries (lithium-containing composite oxides that can occlude and release lithium ions). However, since the continuous charging characteristics of the battery are further improved, and the charge / discharge cycle characteristics and storage characteristics of the nonaqueous secondary battery at a high temperature by the positive electrode material are not impaired, Ni and Co, Mg, Lithium nickelate (C) containing an element M3 selected from the group consisting of Mn, Ba, W, Ti, Zr, Mo and Al is preferred.

Lithium nickelate (C) has the chemical formula Li _{1 + z} McO 2 (−0.05 ≦ z ≦ 2) when Ni, Co, the element M ³ , and other elements that may further be contained are grouped into an element group Mc. 0.05), and the amounts of Ni, Co, and element M3 in the total number of atoms of 100 mol% of the element group Mc are s (mol%), t (mol%), and u (mol), respectively. %), It is preferable that 30 ≦ s ≦ 97, 0.5 ≦ t ≦ 40, 0.5 ≦ u ≦ 40, 70 ≦ s ≦ 97, 0.5 ≦ t ≦ 30, 0. More preferably, 5 ≦ u ≦ 5.

Lithium nickelate (C) includes a Li-containing compound (such as lithium hydroxide and lithium carbonate), a Ni-containing compound (such as nickel sulfate), a Co-containing compound (such as cobalt sulfate and cobalt oxide), and a compound containing the element M3 ( Oxides, hydroxides, sulfates, etc.) and the raw material mixture is fired. In order to synthesize lithium nickelate (C) with higher purity, a composite compound (hydroxide, oxide, etc.) containing a plurality of elements of Ni, Co and element M ³ and other raw material compounds It is preferable to mix (Li-containing compound etc.) and to fire this raw material mixture.

  The firing conditions of the raw material mixture for synthesizing lithium nickelate (C) are, for example, 800 to 1050 ° C. for 1 to 24 hours, as in the case of lithium cobaltate (A) and lithium cobaltate (B). Can be heated to a temperature lower than the firing temperature (for example, 250 to 850 ° C.), held at that temperature, preheated, and then heated to the firing temperature to advance the reaction. Is preferred. Although there is no restriction | limiting in particular about the time of preheating, Usually, what is necessary is just to be about 0.5 to 30 hours. The atmosphere during firing can be an atmosphere containing oxygen (that is, in the air), a mixed atmosphere of an inert gas (such as argon, helium, or nitrogen) and oxygen gas, or an oxygen gas atmosphere. The oxygen concentration (volume basis) is preferably 15% or more, and more preferably 18% or more.

  In the nonaqueous secondary battery of the present invention, when the positive electrode material and another positive electrode active material [for example, lithium nickelate (C)] are used, the total amount of the positive electrode material and the other positive electrode active material is 100 mass. % Of the positive electrode material is preferably 50% by mass or more, more preferably 80% by mass or more (that is, the amount of the other positive electrode active material used together with the positive electrode material is It is preferably 50% by mass or less and more preferably 20% by mass or less in a total of 100% by mass of the positive electrode material and the other positive electrode active material). As described above, in the non-aqueous secondary battery of the present invention, since only the positive electrode material may be used without using a positive electrode active material other than the positive electrode material, the positive electrode material and other positive electrode active materials The preferable upper limit of the amount of the positive electrode material in the total of 100% by mass is 100% by mass. However, in order to secure a better effect of improving the continuous charge characteristics of the battery by using lithium nickelate (C), lithium nickelate (100% by mass) in total of 100% by mass of the positive electrode material and lithium nickelate (C). The amount of C) is preferably 5% by mass or more, and more preferably 10% by mass or more.

<Binder>
As the binder used for the positive electrode, any of a thermoplastic resin and a thermosetting resin can be used as long as it is chemically stable in the battery. For example, polyvinylidene fluoride (PVDF), polyethylene, polypropylene, polytetrafluoroethylene (PTFE), polyhexafluoropropylene (PHFP), styrene-butadiene rubber (SBR), tetrafluoroethylene-hexafluoroethylene copolymer, tetrafluoro Ethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), propylene- Tetrafluoroethylene copolymer, ethylene-chlorotrifluoroethylene copolymer (ECTFE), ethylene-acrylic acid copolymer, ethylene-methacrylic acid copolymer, Len - methyl acrylate copolymer, ethylene - one or more Na ion crosslinked body and the like of the methyl methacrylate copolymer and their copolymers can be used.

<Conductive aid>
As a conductive support agent used for the said positive electrode, what is chemically stable should just be in a battery. For example, graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black (trade name), channel black, furnace black, lamp black and thermal black; conductive fiber such as carbon fiber and metal fiber; aluminum Metal powders such as powders; Fluorinated carbon; Zinc oxide; Conductive whiskers made of potassium titanate; Conductive metal oxides such as titanium oxide; Organic conductive materials such as polyphenylene derivatives, etc. You may use independently and may use 2 or more types together. Among these, highly conductive graphite and carbon black excellent in liquid absorption are preferable. Further, the form of the conductive auxiliary agent is not limited to primary particles, and secondary aggregates and aggregated forms such as chain structures can also be used. Such an assembly is easier to handle and has better productivity.

<Current collector>
The current collector used for the positive electrode can be the same as that used for the positive electrode of conventionally known non-aqueous electrolyte secondary batteries. For example, an aluminum foil having a thickness of 10 to 30 μm can be used. preferable. When the thickness of the entire positive electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is preferably 10 μm in order to ensure conductivity and mechanical strength.

<Method for producing positive electrode>
The positive electrode is prepared, for example, as a paste-like or slurry-like positive electrode mixture-containing composition in which the above-described positive electrode active material, conductive additive and binder are dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP). (However, the binder may be dissolved in a solvent.) After applying this to one or both sides of the current collector and drying, it can be produced through a process of calendering if necessary. . The manufacturing method of a positive electrode is not necessarily restricted to said method, It can also manufacture with another manufacturing method.

<Positive electrode mixture layer>
In the positive electrode mixture layer, it is preferable that the total amount of the positive electrode active material is 92 to 98% by weight, the amount of the conductive auxiliary agent is 1 to 5% by weight, and the amount of the binder is 1 to 3% by weight.
In order to improve discharge characteristics under high load, the thickness of the positive electrode mixture layer is preferably 20 to 70 μm per side.
In addition, when the positive electrode mixture layer is thinned, the maximum distance along which lithium ions move during charge / discharge can be further shortened, so that the internal resistance can be kept low.

Further, the total area of the positive electrode mixture layer on the positive electrode current collector (the total area of the area occupied by the positive electrode mixture layer on one surface of the positive electrode current collector and the area occupied by the positive electrode mixture layer on the other surface) ) is preferably a 300~2000cm ^2, especially 500～1600Cm ² is preferred. This is because when the electrode area is smaller than 300 cm ^{2, the} capacity is lowered from the balance with the electrode thickness described above, and the flowing current value is also reduced. This is because if the total area of the positive electrode mixture layer is larger than 2000 cm ² , the energy density becomes too low due to the balance between the positive electrode mixture layer thickness and the capacity described above, and it becomes difficult to achieve both energy density.

  The value obtained by dividing the battery capacity by the total area of the positive electrode mixture layer (referred to herein as current density) is preferably 1.5 to 3.5. If the current density is less than 1.5, the energy density is too low, and if it is more than 3.5, the polarization resistance at the time of high-load charge / discharge increases and the deterioration of the active material tends to proceed.

[Negative electrode]
The negative electrode used in the non-aqueous electrolyte secondary battery of the present invention has a structure having, for example, a negative electrode active material, a binder, and a negative electrode mixture layer containing a conductive auxiliary agent, if necessary, on one side or both sides of the current collector. Things can be used.

  FIG. 2 shows an example of the negative electrode. The negative electrode 2 is provided with a negative electrode mixture layer 22 on one or both sides of a long negative electrode current collector 21, and the negative electrode mixture layer 22 contains a negative electrode active material, a binder, and a conductive auxiliary agent if necessary. The negative electrode mixture slurry dispersed in a solvent is formed on the negative electrode current collector 21 by coating and drying. At least one surface of the negative electrode current collector 21 is provided with a portion without the negative electrode mixture layer for disposing the negative electrode current collector tab 23, that is, an uncoated portion N. In the uncoated portion N, the negative electrode current collector tab 23 is disposed by means such as ultrasonic welding or resistance welding so as to be electrically connected to the negative electrode current collector 21.

  In the negative electrode as well, it seems that if the negative electrode tab is arranged in the uncoated part provided in the central part like the positive electrode, it contributes to lowering the resistance. However, an opposing negative electrode mixture layer is always required in the portion where the positive electrode mixture layer exists. This is because, if there is no receiving side of lithium ions separated from the positive electrode mixture layer during charging, lithium is deposited on the negative electrode and lithium dendrites are formed. Therefore, the opposing negative electrode mixture layer is disposed with a margin in area with respect to the location where the positive electrode mixture layer exists.

  In other words, if an uncoated part in which the negative electrode mixture layer does not exist in the negative electrode is provided in the central part in the longitudinal direction of the negative electrode, it is not coated on the positive electrode in a larger area than the uncoated part of the negative electrode Part (that is, the range in which the positive electrode mixture layer cannot be arranged becomes wider), the ratio of the active material contributing to the capacity with respect to the total battery weight is reduced, and the energy density per weight is reduced. Connected. Therefore, the negative electrode current collecting tab in the negative electrode is preferably disposed at the end portion in the length direction of the negative electrode.

  Only one negative electrode current collecting tab or a plurality of negative electrode current collecting tabs may be arranged. Since the weight energy density can be improved by reducing the weight of the member that does not contribute to charging / discharging in the battery, it is preferable to arrange only one member.

<Negative electrode active material>
The negative electrode active material is not particularly limited as long as it is a negative electrode active material used in conventionally known non-aqueous electrolyte secondary batteries, that is, a material capable of inserting and extracting lithium ions. For example, carbon-based materials that can occlude and release lithium ions, such as graphite, pyrolytic carbons, cokes, glassy carbons, fired organic polymer compounds, mesocarbon microbeads (MCMB), and carbon fibers. One kind or a mixture of two or more kinds is used as the negative electrode active material. In addition, elements such as silicon (Si), tin (Sn), germanium (Ge), bismuth (Bi), antimony (Sb), indium (In) and alloys thereof, lithium such as lithium-containing nitride or lithium-containing oxide A compound that can be charged and discharged at a low voltage close to that of a metal, or a lithium metal or lithium / aluminum alloy can also be used as the negative electrode active material. Among these, as the negative electrode active material, graphite or a mixture of graphite and a material represented by SiO _x containing silicon and oxygen as constituent elements is preferable.

The SiO _x may contain Si microcrystal or amorphous phase. In this case, the atomic ratio of Si and O is a ratio including Si microcrystal or amorphous phase Si. That is, the SiO _x to SiO ₂ matrix of amorphous Si (e.g., microcrystalline Si) is include the dispersed structure, the SiO ₂ of the amorphous, dispersed therein It is only necessary that the atomic ratio x satisfies 0.5 ≦ x ≦ 1.5. For example, in the case of a material in which Si is dispersed in an amorphous SiO ₂ matrix and the material has a molar ratio of SiO ₂ to Si of 1: 1, x = 1, so that the structural formula is represented by SiO. The In the case of a material having such a structure, for example, in X-ray diffraction analysis, a peak due to the presence of Si (microcrystalline Si) may not be observed, but when observed with a transmission electron microscope, the presence of fine Si Can be confirmed.

The SiO _x is preferably a composite that is combined with a carbon material. For example, the surface of the SiO _x is preferably covered with the carbon material. Usually, since SiO _x has poor conductivity, when using it as a negative electrode active material, from the viewpoint of ensuring good battery characteristics, a conductive material (conductive aid) is used, and SiO _x in the negative electrode is electrically conductive. It is necessary to form an excellent conductive network by making good mixing and dispersion with the conductive material. If it is a composite in which SiO _x is combined with a carbon material, for example, a conductive network in the negative electrode is better than when a material obtained by simply mixing SiO _x and a conductive material such as a carbon material is used. Formed.

<Binder>
Examples of the binder include polysaccharides such as starch, polyvinyl alcohol, polyacrylic acid, carboxymethyl cellulose (CMC), hydroxypropyl cellulose, regenerated cellulose, and diacetyl cellulose, and modified products thereof; polyvinyl chloride, polyvinyl pyrrolidone (PVP), Thermoplastic resins such as polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyamide, and their modified products; polyimide; ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber ( SBR), butadiene rubber, polybutadiene, fluororubber, polyethylene oxide and other polymers having rubber-like elasticity and their modifications; It can be used or two or more. "

<Conductive aid>
A conductive material may be further added to the negative electrode mixture layer as a conductive aid. Such a conductive material is not particularly limited as long as it does not cause a chemical change in the battery. For example, carbon black (thermal black, furnace black, channel black, ketjen black, acetylene black, etc.), carbon It is possible to use one or more materials such as fiber, metal powder (powder of copper, nickel, aluminum, silver, etc.), metal fiber, polyphenylene derivative (described in JP-A-59-20971). it can. Among these, carbon black is preferably used, and ketjen black and acetylene black are more preferable.

<Current collector>
As the current collector, a copper or nickel foil, a punching metal, a net, an expanded metal, or the like can be used, but a copper foil is usually used. In the negative electrode current collector, when the thickness of the whole negative electrode is reduced in order to obtain a battery having a high energy density, the upper limit of the thickness is preferably 30 μm, and the lower limit is 5 μm in order to ensure conductivity and mechanical strength. It is desirable that

<Method for producing negative electrode>
The negative electrode is, for example, a paste or slurry in which the above-described negative electrode active material and binder and, if necessary, a conductive assistant are dispersed in a solvent such as N-methyl-2-pyrrolidone (NMP) or water. A negative electrode mixture-containing composition is prepared, applied to one or both sides of a current collector, dried, and then subjected to a calendering process as necessary. The manufacturing method of a negative electrode is not necessarily restricted to said manufacturing method, It can also manufacture with another manufacturing method.

<Negative electrode mixture layer>
In the said negative mix layer, it is preferable that the total amount of a negative electrode active material shall be 80-99 mass%, and the quantity of a binder shall be 1-20 mass%. In addition, when a conductive material is separately used as a conductive auxiliary agent, these conductive materials in the negative electrode mixture layer are used in such a range that the total amount of the negative electrode active material and the binder amount satisfy the above-described preferable values. It is preferable.

In order to improve discharge characteristics under high load, the thickness of the negative electrode mixture layer is preferably 20 to 70 μm per side.
This is because, if the negative electrode mixture layer is thinned, the maximum distance along which lithium ions move during charge / discharge can be shortened, so that the internal resistance can be kept low. The material represented by SiO _x can have a higher capacity than graphite, which is the most common negative electrode active material. Therefore, when the material represented by SiO _x is contained in the negative electrode active material, the total amount of the negative electrode active material can be reduced, so that the negative electrode mixture layer can be easily thinned.

[Non-aqueous electrolyte]
As the non-aqueous electrolyte according to the non-aqueous electrolyte secondary battery of the present invention, a non-aqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent can be used.

The lithium salt used in the non-aqueous electrolyte is not particularly limited as long as it dissociates in a solvent to form lithium ions and does not easily cause a side reaction such as decomposition in a voltage range used as a battery. For example, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiSbF _{6 and} other inorganic lithium salts, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (2 ≦ n ≦ 7), LiN (RfOSO ₂ ) ₂ [where Rf is a fluoroalkyl group] or the like is used. be able to.

  The concentration of the lithium salt in the non-aqueous electrolyte is preferably 0.5 to 1.5 mol / L, and more preferably 0.9 to 1.25 mol / L.

  The organic solvent used for the non-aqueous electrolyte is not particularly limited as long as it dissolves the lithium salt and does not cause a side reaction such as decomposition in a voltage range used as a battery. For example, cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate; chain carbonates such as dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate; chain esters such as methyl propionate; cyclic esters such as γ-butyrolactone; dimethoxyethane, Chain ethers such as diethyl ether, 1,3-dioxolane, diglyme, triglyme and tetraglyme; cyclic ethers such as dioxane, tetrahydrofuran and 2-methyltetrahydrofuran; nitriles such as acetonitrile, propionitrile and methoxypropionitrile; ethylene Examples thereof include sulfites such as glycol sulfite, and these may be used as a mixture of two or more. In order to obtain a battery with better characteristics, it is desirable to use a combination that can obtain high conductivity, such as a mixed solvent of ethylene carbonate and chain carbonate.

[Separator]
The separator according to the present invention has a property (that is, a shutdown function) that the pores are blocked at 80 ° C. or higher (more preferably 100 ° C. or higher) and 170 ° C. or lower (more preferably 150 ° C. or lower). Preferably, a separator used in a normal lithium secondary battery, for example, a microporous film made of polyolefin such as polyethylene (PE) or polypropylene (PP) can be used. The microporous film constituting the separator may be, for example, one using only PE or one using PP, or a laminate of a PE microporous film and a PP microporous film. There may be.

  The separator of the present invention preferably has a thickness of more than 6 μm and less than 20 μm. From the viewpoint of reducing the distance between the counter electrodes of the positive and negative electrodes and improving the charge / discharge performance at high load, it is further preferably smaller than 16 μm, more preferably smaller than 14 μm.

  The separator according to the present invention mainly includes a porous layer (I) mainly composed of a resin having a melting point of 140 ° C. or lower and a resin that does not melt at a temperature of 150 ° C. or lower or an inorganic filler having a heat resistant temperature of 150 ° C. or higher. It is preferable to use a laminated separator having a porous layer (II). Here, the “melting point” means a melting temperature measured using a differential scanning calorimeter (DSC) in accordance with JIS K 7121. In addition, “does not melt at a temperature of 150 ° C. or lower” means that the melting temperature measured using DSC exceeds 150 ° C. according to the provisions of JIS K 7121. This means that the melting behavior is not exhibited at the temperature. Furthermore, “the heat resistant temperature is 150 ° C. or higher” means that deformation such as softening is not observed at least at 150 ° C.

  The porous layer (I) according to the laminated separator is mainly for ensuring a shutdown function, and the melting point of the resin, which is a component in which the lithium secondary battery is the main component of the porous layer (I) When the temperature reaches the value, the resin related to the porous layer (I) melts and closes the pores of the separator, thereby causing a shutdown that suppresses the progress of the electrochemical reaction.

  Examples of the resin having a melting point of 140 ° C. or lower, which is the main component of the porous layer (I), include PE, and the form thereof is a substrate such as a microporous film used in the above-described lithium secondary battery or a nonwoven fabric. And a dispersion obtained by applying a dispersion containing PE particles and drying. Here, in all the constituent components of the porous layer (I), the volume of the resin having a main melting point of 140 ° C. or less is 50% by volume or more, and more preferably 70% by volume or more. For example, when the porous layer (I) is formed of the microporous film of PE, the volume of the resin having a melting point of 140 ° C. or lower is 100% by volume.

  The porous layer (II) according to the multilayer separator has a function of preventing a short circuit due to direct contact between the positive electrode and the negative electrode even when the internal temperature of the lithium secondary battery is increased. The function is secured by a resin that does not melt at a temperature of ℃ or less or an inorganic filler with a heat resistant temperature of 150 ℃ or more. That is, when the battery becomes high temperature, even if the porous layer (I) shrinks, the porous layer (II) which does not easily shrink can directly generate positive and negative electrodes that can be generated when the separator is thermally contracted. It is possible to prevent a short circuit due to the contact. Moreover, since this heat-resistant porous layer (II) acts as a skeleton of the separator, the thermal contraction of the porous layer (I), that is, the thermal contraction of the entire separator itself can be suppressed.

  When the porous layer (II) is formed mainly of a resin having a melting point of 150 ° C. or higher, for example, a microporous film formed of a resin that does not melt at a temperature of 150 ° C. or lower (for example, the above-mentioned PP micro battery cell The porous layer (I) is laminated on the porous layer (I), or a dispersion liquid containing resin particles that do not melt at a temperature of 150 ° C. or lower is applied to the porous layer (I) and dried to form a porous layer ( Examples thereof include a coating lamination type form in which the porous layer (II) is formed on the surface of I).

  Examples of resins that do not melt at a temperature of 150 ° C. or less include PP; crosslinked polymethyl methacrylate, crosslinked polystyrene, crosslinked polydivinylbenzene, styrene-divinylbenzene copolymer crosslinked product, polyimide, melamine resin, phenol resin, benzoguanamine-formaldehyde condensation And various crosslinked polymer fine particles; polysulfone; polyether sulfone; polyphenylene sulfide; polytetrafluoroethylene; polyacrylonitrile; aramid; polyacetal and the like.

  When using resin particles that do not melt at a temperature of 150 ° C. or lower, the average particle size is, for example, preferably 0.01 μm or more, more preferably 0.1 μm or more, It is preferably 10 μm or less, and more preferably 2 μm or less. As described above, the average particle diameter of the various particles referred to in the present specification is measured by dispersing these fine particles in a medium in which the resin is not dissolved, using a laser scattering particle size distribution analyzer “LA-920” manufactured by Horiba, Ltd. The average particle diameter D is 50%.

  When the porous layer (II) is mainly formed of an inorganic filler having a heat resistant temperature of 150 ° C. or higher, for example, a dispersion containing an inorganic filler having a heat resistant temperature of 150 ° C. or higher is applied to the porous layer (I). Examples of the coating-laminated type in which the porous layer (II) is formed by drying.

  The inorganic filler related to the porous layer (II) has a heat resistant temperature of 150 ° C. or higher, is stable to the non-aqueous electrolyte of the battery, and is electrochemically stable to be hardly oxidized or reduced in the battery operating voltage range. However, fine particles are preferable from the viewpoint of dispersion, and alumina, silica, and boehmite are preferable. Alumina, silica, and boehmite have high oxidation resistance, and the particle size and shape can be adjusted to the desired numerical values, making it easy to control the porosity of the porous layer (II) with high accuracy. It becomes. As the inorganic filler having a heat resistant temperature of 150 ° C. or higher, for example, one of the above-mentioned examples may be used alone, or two or more may be used in combination. Further, an inorganic filler having a heat resistant temperature of 150 ° C. or higher may be used in combination with a resin that does not melt at a temperature of 150 ° C. or lower.

  There is no restriction | limiting in particular about the shape of the inorganic filler whose heat resistant temperature which concerns on porous layer (II) is 150 degreeC or more, A substantially spherical shape (a true spherical shape is included), a substantially ellipsoid shape (an ellipsoid shape is included), a board Various shapes such as shapes can be used.

  Further, the average particle diameter of the inorganic filler having a heat resistant temperature of 150 ° C. or higher related to the porous layer (II) is preferably 0.3 μm or more because the ion permeability is lowered if it is too small. More preferably, it is 5 μm or more. In addition, if the inorganic filler having a heat resistant temperature of 150 ° C. or higher is too large, the electrical characteristics are likely to be deteriorated. Therefore, the average particle diameter is preferably 5 μm or less, and more preferably 2 μm or less.

  In the porous layer (II), the resin that does not melt at a temperature of 150 ° C. or lower and the inorganic filler having a heat resistant temperature of 150 ° C. or higher are mainly contained in the porous layer (II). Amount in (II) [when the porous layer (II) contains only one of a resin that does not melt at a temperature of 150 ° C. or less and an inorganic filler that has a heat resistant temperature of 150 ° C. or more, is the amount, If both are included, the total amount. The same applies hereinafter in the porous layer (II) of the resin that does not melt at a temperature of 150 ° C. or lower and the inorganic filler having a heat resistant temperature of 150 ° C. or higher. ] Is 50% by volume or more in the total volume of the constituent components of the porous layer (II), preferably 70% by volume or more, more preferably 80% by volume or more, and 90% by volume or more. More preferably it is. By making the heat-resistant material in the porous layer (II) high as described above, even when the lithium secondary battery becomes high temperature, it is possible to satisfactorily suppress the thermal contraction of the entire separator, Generation | occurrence | production of the short circuit by the direct contact of a positive electrode and a negative electrode can be suppressed more favorably.

  As will be described later, since it is preferable that the porous layer (II) also contains an organic binder, in the porous layer (II) of a resin that does not melt at a temperature of 150 ° C. or less and an inorganic filler having a heat resistant temperature of 150 ° C. or more. The amount is preferably 99.5% by volume or less in the total volume of the constituent components of the porous layer (II).

  In the porous layer (II), a resin that does not melt at a temperature of 150 ° C. or less or an inorganic filler having a heat resistant temperature of 150 ° C. or higher is bound, or the porous layer (II) and the porous layer (I) For integration or the like, it is preferable to contain an organic binder. Examples of organic binders include ethylene-vinyl acetate copolymers (EVA, those having a structural unit derived from vinyl acetate of 20 to 35 mol%), ethylene-acrylic acid copolymers such as ethylene-ethyl acrylate copolymers, and fluorine-based binders. Examples include rubber, SBR, CMC, hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), cross-linked acrylic resin, polyurethane, and epoxy resin. A heat-resistant binder having a heat-resistant temperature is preferably used. As the organic binder, those exemplified above may be used singly or in combination of two or more.

  Among the organic binders exemplified above, highly flexible binders such as EVA, ethylene-acrylic acid copolymer, fluorine-based rubber, and SBR are preferable. Specific examples of such highly flexible organic binders include EVA “Evaflex Series” from Mitsui DuPont Polychemical Co., Ltd., EVA from Nippon Unicar Co., Ltd. -EEA Series ", Nippon Unicar Company's EEA, Daikin Industries' fluoro rubber" Daiel Latex Series ", JSR's SBR" TRD-2001 ", Zeon Corporation's SBR" BM-400B "and the like.

  When the organic binder is used in the porous layer (II), it may be used in the form of an emulsion dissolved or dispersed in a solvent of a composition for forming the porous layer (II) described later.

  The coating-laminated separator is, for example, a composition for forming a porous layer (II) containing a resin particle that does not melt at a temperature of 150 ° C. or lower, an inorganic filler having a heat resistant temperature of 150 ° C. or higher (liquid such as slurry). The composition etc.) can be applied to the surface of the microporous membrane for constituting the porous layer (I) and dried at a predetermined temperature to form the porous layer (II).

  The composition for forming the porous layer (II) contains resin particles that do not melt at a temperature of 150 ° C. or lower and / or an inorganic filler having a heat resistant temperature of 150 ° C. or higher, and an organic binder as necessary. Is dispersed in a solvent (including a dispersion medium; the same shall apply hereinafter). The organic binder can be dissolved in a solvent. The solvent used in the composition for forming the porous layer (II) can uniformly disperse resin particles and inorganic filler that do not melt at a temperature of 150 ° C. or lower, and can dissolve or disperse the organic binder uniformly. Common organic solvents such as aromatic hydrocarbons such as toluene; furans such as tetrahydrofuran; ketones such as methyl ethyl ketone and methyl isobutyl ketone; are preferably used. For the purpose of controlling the interfacial tension, alcohols (ethylene glycol, propylene glycol, etc.) or various propylene oxide glycol ethers such as monomethyl acetate may be appropriately added to these solvents. In addition, when the organic binder is water-soluble or used as an emulsion, water may be used as a solvent. In this case, alcohols (methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, etc.) are appropriately added. It is also possible to control the interfacial tension.

  The composition for forming the porous layer (II) has a solid content containing, for example, a resin particle that does not melt at a temperature of 150 ° C. or lower and / or an inorganic filler having a heat resistant temperature of 150 ° C. or higher, and an organic binder. It is preferable to set it as -80 mass%.

In the laminated separator, the porous layer (I) and the porous layer (II) do not have to be one each, and a plurality of layers may be present in the separator. For example, the porous layer (I) may be arranged on both sides of the porous layer (II), or the porous layer (II) may be arranged on both sides of the porous layer (I). However, increasing the number of layers may increase the thickness of the separator and increase the internal resistance of the battery or decrease the energy density. Therefore, it is not preferable to increase the number of layers. The total number of layers of the porous layer (I) and the porous layer (II) is preferably 5 or less.
As described above, the thickness of the entire separator can be reduced according to the present invention. However, when the laminated separator is used, the effect of suppressing thermal shrinkage is extremely high, and therefore the thickness of the separator is further reduced. It becomes possible.

Specifically, the thickness of the porous layer (I) can be 5 to 14 μm, the thickness of the porous layer (II) can be 1 to 5 μm, and the total thickness can be 6 to 15 μm.
As a result, the thickness of the separator can be further reduced, and the distance between the positive and negative electrodes can be shortened, so that the internal resistance of the battery can be kept low.

  The porosity of the separator as a whole is preferably 30% or more in a dried state in order to secure the amount of electrolyte solution retained and to improve ion permeability. On the other hand, from the viewpoint of securing separator strength and preventing internal short circuit, the separator porosity is preferably 70% or less in a dry state. The porosity of the separator: P (%) can be calculated by obtaining the sum for each component i from the thickness of the separator, the mass per area, and the density of the constituent components using the following formula (1).

P = {1-m / (Σaiρi × t)} × 100 (1)
Here, in the formula (1), ai: the ratio of the component i expressed in mass%, ρi: the density of the component i (g / cm ³ ), m: mass per unit area of the separator (g / cm ² ) , T is the thickness (cm) of the separator.

In the case of the multilayer separator, in the formula (1), m is the mass per unit area (g / cm ² ) of the porous layer (I), and t is the thickness of the porous layer (I) ( cm), the porosity: P (%) of the porous layer (I) can also be obtained using the formula (1). The porosity of the porous layer (I) determined by this method is preferably 30 to 70%.

Further, in the case of the laminated separator, in the formula (1), m is the mass per unit area (g / cm ² ) of the porous layer (II), and t is the thickness of the porous layer (II) ( cm), the porosity: P (%) of the porous layer (II) can also be obtained using the formula (1). The porosity of the porous layer (II) obtained by this method is preferably 20 to 60%.

The separator preferably has high mechanical strength. For example, the puncture strength is preferably 3N or more. For example, when SiO _x having a large volume change due to charge / discharge is used as the negative electrode active material, mechanical damage is also applied to the facing separator due to expansion / contraction of the entire negative electrode by repeating charge / discharge. If the piercing strength of the separator is 3N or more, good mechanical strength is ensured, and mechanical damage to the separator can be reduced.

  Examples of the separator having a puncture strength of 3N or more include the above-described laminated separator, and in particular, an inorganic filler having a heat resistant temperature of 150 ° C. or higher in the porous layer (I) mainly composed of a resin having a melting point of 140 ° C. or lower. A separator in which a porous layer (II) containing as a main component is laminated is preferable. This is presumably because the mechanical strength of the separator can be increased by supplementing the mechanical strength of the porous layer (I) because the inorganic filler has high mechanical strength.

  The puncture strength can be measured by the following method. A separator is fixed on a plate having a hole with a diameter of 2 inches so as not to be wrinkled or bent, and a semicircular metal pin having a tip diameter of 1.0 mm is lowered onto a measurement sample at a speed of 120 mm / min. Measure the force when making a hole in the separator 5 times. And an average value is calculated | required about the measurement of 3 times except the maximum value and the minimum value among the said measurement values of 5 times, and this is made into the piercing strength of a separator.

  The positive electrode, the negative electrode, and the separator are formed in the form of a laminated electrode body in which a separator is interposed between the positive electrode and the negative electrode, or a wound electrode body in which the separator is wound in a spiral shape. It can be used for the first lithium secondary battery of the invention.

  In the laminated electrode body and the wound electrode body, the laminated separator, particularly the porous layer (I) mainly composed of a resin having a melting point of 140 ° C. or lower, mainly composed of an inorganic filler having a heat resistant temperature of 150 ° C. or higher. When using the separator which laminated | stacked porous layer (II) included as, it is preferable to arrange | position so that porous layer (II) may face a positive electrode at least. In this case, since the porous layer (II) that includes an inorganic filler having a heat resistant temperature of 150 ° C. or more as a main component and more excellent in oxidation resistance faces the positive electrode, oxidation of the separator by the positive electrode can be better suppressed, It is also possible to improve the storage characteristics and charge / discharge cycle characteristics of the battery at high temperatures. Further, when an additive such as VC or cyclohexylbenzene is added to the non-aqueous electrolyte, a film is formed on the positive electrode side to clog the pores of the separator, which may cause deterioration of battery characteristics. Therefore, an effect of suppressing clogging of pores can be expected by causing the relatively porous porous layer (II) to face the positive electrode.

  The non-aqueous electrolyte secondary battery of the present invention can be used with the upper limit voltage of charging being about 4.2 V as in the case of the conventional non-aqueous electrolyte secondary battery, but the upper limit voltage of charging is higher than this. It is also possible to use it by setting it to 3 V or more, so that it is possible to stably exhibit excellent characteristics even if it is repeatedly used over a long period of time while increasing the capacity. In addition, it is preferable that the upper limit voltage of charge of a nonaqueous electrolyte secondary battery is 4.7V or less.

  The non-aqueous electrolyte secondary battery of the present invention can be applied to the same applications as conventionally known non-aqueous electrolyte secondary batteries. In particular, the present invention is preferably applied to applications that require both high energy density and charge / discharge characteristics at high loads, such as industrial robots and drones, which are used at high loads.

Example 1
<Preparation of positive electrode>
Li ₂ CO ₃ that is a Li-containing compound, Co ₃ O ₄ that is a Co-containing compound, Mg (OH) ₂ that is a Mg-containing compound, ZrO ₂ that is a Zr compound, and Al (OH that is an Al-containing compound ₃ ) was mixed in a mortar at an appropriate mixing ratio, then solidified into a pellet, and baked in an air atmosphere (under atmospheric pressure) at 950 ° C. for 24 hours using an muffle furnace, and ICP (Inductive Coupled) Lithium cobaltate (A1) having a composition formula determined by the Plasma) method of LiCo _0.9795 Mg _0.011 Zr _0.0005 Al _0.009 O ₂ was synthesized.

Next, 10 g of the lithium cobaltate (A1) is added to 200 g of a lithium hydroxide aqueous solution having a pH of 10 and a temperature of 70 ° C., and the mixture is stirred and dispersed. Then, Al (NO ₃ ) is added thereto. ) ₃ · _9H 2 O: and 0.0154G, and ammonia water to suppress variation in pH, was added dropwise over 5 hours, to produce a Al _{(OH) 3} coprecipitate, the lithium cobalt oxide (A1 ). Thereafter, the lithium cobalt oxide (A1) to which the Al (OH) ₃ coprecipitate is adhered is taken out from the reaction solution, washed, dried, and then heat-treated at 400 ° C. for 10 hours in an air atmosphere. Thus, an Al-containing oxide film was formed on the surface of the lithium cobalt oxide (A1) to obtain a positive electrode material (a1).

  With respect to the positive electrode material (a1) obtained, its average particle diameter was measured by means of the method as described before, thereby finding that it was 27 μm.

Li ₂ CO ₃ that is a Li-containing compound, Co ₃ O ₄ that is a Co-containing compound, Mg (OH) ₂ that is an Mg-containing compound, and Al (OH) ₃ that is an Al-containing compound are appropriately mixed. After mixing in a mortar, the mixture was hardened into pellets, baked at 950 ° C. for 4 hours in an atmospheric atmosphere (under atmospheric pressure) using a muffle furnace, and the composition formula obtained by ICP method was LiCo _0.97. Mg _0.012 Al _0.009 O ₂ lithium cobaltate (B1) was synthesized.

Next, 10 g of the lithium cobalt oxide (B1) is added to 200 g of lithium hydroxide aqueous solution: 200 having a pH of 10 and a temperature of 70 ° C., and dispersed by stirring. _{3) 3} · _9H 2 O: and 0.077 g, and ammonia water to suppress variation in pH, was added dropwise over 5 hours, to produce a Al _{(OH) 3} coprecipitate, the lithium cobaltate ( It was made to adhere to the surface of B1). Thereafter, the lithium cobaltate (B1) to which the Al (OH) ₃ coprecipitate is adhered is taken out from the reaction solution, washed, dried, and then heat-treated at 400 ° C. for 10 hours in an air atmosphere. Then, an Al-containing oxide film was formed on the surface of the lithium cobalt oxide (B1) to obtain a positive electrode material (b1).

  With respect to the positive electrode material (b1) obtained, its average particle diameter was measured by means of the method as described before, thereby finding that it was 7 μm.

Then, the positive electrode material (a1) and the positive electrode material (b1) were mixed at a mass ratio of 85:15 to obtain a positive electrode material (1) for battery preparation. When the average coating thickness of the Al-containing oxide on the surface of the obtained positive electrode material (1) was measured by the above method, it was 30 nm. Moreover, when the composition of the film was confirmed by element mapping when measuring the average coating thickness, the main component was Al ₂ O ₃ . Furthermore, when the volume-based particle size distribution of the positive electrode material (1) was confirmed by the above method, the average particle diameter was 25 μm, and peak tops were observed at the respective average particle diameters of the positive electrode material (a1) and the positive electrode material (b1). Two peaks were observed with

  100 parts by mass of the positive electrode material produced as described above, 20 parts by mass of an NMP solution containing PVDF as a binder at a concentration of 10% by mass, 1 part by mass of artificial graphite and 1 part by mass of ketjen black as a conductive aid Was kneaded using a biaxial kneader, and NMP was further added to adjust the viscosity to prepare a positive electrode mixture-containing paste.

As shown in FIG. 1, the paste containing the positive electrode mixture is applied to both surfaces and part of one surface of an aluminum foil (positive electrode current collector) having a thickness of 12 μm, and then vacuum-dried at 120 ° C. for 12 hours to obtain aluminum. A positive electrode mixture layer was formed on both sides of the foil. Then, the press process was performed and the thickness and density of the positive mix layer were adjusted. The positive electrode mixture layer in the positive electrode obtained had a thickness of 79 μm on both sides. As shown in FIG. 1, by welding a positive electrode current collector tab made of aluminum (width 5 mm, thickness 0.08 mm, cross-sectional area 0.4 mm ² ) to an aluminum foil exposed part (uncoated part) in the center part, A strip-like positive electrode having a length of 1000 mm and a width of 52 mm having a positive electrode current collecting tab was produced. The positive electrode current collecting tab position at this time was a distance of S to E of 960 mm and a distance of S to T of 512 mm (53% of the distance of S to E).

<Production of negative electrode>
Graphite with an average particle diameter D50% of 16 μm as a negative electrode active material: 97.5 parts by mass, SBR as a binder: 1.5 parts by mass, and CMC as a thickener: 1 part by mass In addition, the mixture was mixed to prepare a negative electrode mixture-containing paste.

  As shown in FIG. 2, the negative electrode mixture-containing paste was applied to both sides of a copper foil (negative electrode current collector) having a thickness of 8 μm, and then vacuum-dried at 120 ° C. for 12 hours to obtain both sides of the copper foil and A negative electrode mixture layer was formed on a part of one side. Thereafter, press treatment is performed to adjust the thickness and density of the negative electrode mixture layer, and a nickel negative electrode current collecting tab is welded to the exposed portion of the copper foil as shown in FIG. A 53 mm strip-shaped negative electrode was produced. The negative electrode mixture layer in the obtained negative electrode had a thickness of 92 μm on both sides.

<Preparation of non-aqueous electrolyte>
LiPF ₆ was dissolved at a concentration of 1.1 mol / L in a mixed solvent of ethylene carbonate and diethyl carbonate in a volume ratio of 3: 7, and 2% by mass of vinylene carbonate and 2% by mass of fluoroethylene carbonate were added to each other to form non-water. An electrolyte was prepared.

<Preparation of separator>
To 5 kg of plate boehmite (average particle diameter 1 μm, aspect ratio 10), 5 kg of ion-exchanged water and 0.5 kg of a dispersant (aqueous polycarboxylic acid ammonium salt, solid content concentration 40% by mass) are added, and the internal volume is 20 L. Dispersion was prepared by crushing for 10 hours with a ball mill with 40 rotations / minute. When a part of the treated dispersion was vacuum dried at 120 ° C. and observed with a scanning electron microscope (SEM), the shape of boehmite was almost plate-like. The average particle size of the boehmite after the treatment was 1 μm.

  To 500 g of the above dispersion, 0.5 g of xanthan gum as a thickener and 17 g of a resin binder dispersion (modified polybutyl acrylate, solid content 45% by mass) as a binder are added and stirred with a three-one motor for 3 hours to obtain uniform porosity. A slurry for forming a quality layer (II) (solid content ratio 50 mass%) was prepared.

Corona discharge treatment (discharge amount 40 W · min / m) on one side of the porous layer (I) made of PE microporous membrane (thickness 10 μm, porosity 40%, average pore diameter 0.08 μm, PE melting point 135 ° C.) ² ), the porous layer (II) forming slurry is applied to the treated surface by a micro gravure coater, and dried to form a porous layer (II) having a thickness of 2 μm on one side of the separator. A laminated separator was produced.

<Battery assembly>
The strip-shaped positive electrode was overlapped with the strip-shaped negative electrode via the laminated separator (porosity: 42%), and wound in a spiral shape so that the negative electrode current collecting tab was on the inner peripheral side of the wound body. Then, it pressed so that it might become flat shape, it was set as the winding electrode body of a flat winding structure, and this electrode winding body was fixed with the insulating tape made from a polypropylene. The wide surface dimensions of the electrode body at this time were 45 mm in the width direction (direction perpendicular to the winding axis direction) and 56 mm in the height direction (direction parallel to the winding axis direction).
Next, the wound electrode body is inserted into a square can made of aluminum alloy having an outer dimension of thickness 5.1 mm, width 47 mm, and height 58 mm, and the current collecting tabs are welded to each other, and an aluminum alloy lid The plate was welded to the open end of the square can. Thereafter, the non-aqueous electrolyte was injected from an inlet provided in the cover plate, and the inlet was sealed to obtain a non-aqueous electrolyte secondary battery 100 having the appearance shown in FIG.

  The nonaqueous electrolyte secondary battery 100 includes an outer can 111 and a cover plate 121, which also serve as a positive electrode terminal. The outer can 111 includes a pair of side surface portions 112, a pair of wide surfaces 113, and a bottom surface. The wide surface 113 has a cleavage groove 114 that operates as an explosion-proof mechanism when the internal pressure of the battery increases. The lid 121 is inserted into the opening of the outer can 111, and the joint of the two is welded to seal the opening of the outer can 111 and seal the inside of the battery. The lid 121 is provided with a non-aqueous electrolyte inlet, and the non-aqueous electrolyte inlet is welded and sealed by, for example, laser welding in a state where the sealing member 122 is inserted. Airtightness is ensured. A stainless steel terminal 123 is attached to the lid 121 via an insulating packing 124 made of PP, and a lead plate is attached to the terminal 123 via an insulator inside the battery.

  Although not shown, the positive electrode current collecting tab is directly welded to the lid body 121 so that the outer can 111 and the lid body 121 function as a positive electrode terminal, and the negative electrode current collecting tab is welded to a lead plate inside the battery. The terminal 123 functions as a negative electrode terminal by conducting with the terminal 123 through the lead plate.

Example 2
Except for changing Al _{(NO 3)} the amount of 3 · 9H ₂ O to 0.0026g was prepare a positive electrode material in the same manner as the positive electrode material (a1) (a2). With respect to the positive electrode material (a2) obtained, its average particle diameter was measured by means of the method as described before, thereby finding that it was 27 μm.

Also, except for changing the Al _{(NO 3)} the amount of 3 · 9H ₂ O in 0.013g is to prepare a positive electrode material (b2) in the same manner as the positive electrode material (b1). With respect to the positive electrode material (b2) obtained, its average particle diameter was measured by means of the method as described before, thereby finding that it was 7 μm.

Next, the positive electrode material (a2) and the positive electrode material (b2) were mixed at a mass ratio of 85:15 to obtain a positive electrode material (2) for battery production. When the average coating thickness of the Al-containing oxide on the surface of the obtained positive electrode material (2) was measured by the above method, it was 5 nm. Moreover, when the composition of the film was confirmed by element mapping when measuring the average coating thickness, the main component was Al ₂ O ₃ . Further, when the volume-based particle size distribution of the positive electrode material (2) was confirmed by the above method, the average particle diameter was 25 μm, and peak tops were observed at the respective average particle diameters of the positive electrode material (a2) and the positive electrode material (b2). Two peaks were observed with

  Then, a positive electrode was produced in the same manner as in Example 1 except that the positive electrode material (2) was used instead of the positive electrode material (1), and the nonaqueous electrolyte 2 was prepared in the same manner as in Example 1 except that this positive electrode was used. A secondary battery was produced.

Example 3
Except for changing Al _{(NO 3)} the amount of 3 · 9H ₂ O to 0.0256g was prepare a positive electrode material in the same manner as the positive electrode material (a1) (a3). With respect to the positive electrode material (a3) obtained, its average particle diameter was measured by means of the method as described before, thereby finding that it was 27 μm.

Also, except for changing the Al _{(NO 3)} the amount of 3 · 9H ₂ O in 0.128g is to prepare a positive electrode material (b3) in the same manner as the positive electrode material (b1). With respect to the positive electrode material (b3) obtained, its average particle diameter was measured by means of the method as described before, thereby finding that it was 7 μm.

Next, the positive electrode material (a3) and the positive electrode material (b3) were mixed at a mass ratio of 85:15 to obtain a positive electrode material (3) for battery preparation. When the average coating thickness of the Al-containing oxide on the surface of the obtained positive electrode material (3) was measured by the above method, it was 50 nm. Moreover, when the composition of the film was confirmed by element mapping when measuring the average coating thickness, the main component was Al ₂ O ₃ . Furthermore, when the volume-based particle size distribution of the positive electrode material (3) was confirmed by the above method, the average particle diameter was 25 μm, and peak tops were observed at the respective average particle diameters of the positive electrode material (a3) and the positive electrode material (b3). Two peaks were observed with

  Then, a positive electrode was produced in the same manner as in Example 1 except that the positive electrode material (3) was used instead of the positive electrode material (1), and the non-aqueous electrolyte 2 was prepared in the same manner as in Example 1 except that this positive electrode was used. A secondary battery was produced.

Example 4
Mixture of 80:20 mass ratio of positive electrode material (1) and lithium nickelate (composition formula LiNi _0.85 Co _0.120 Mg _0.01 Al _0.02 O ₂ ): 96.5 parts by mass, An NMP solution containing a certain PVDF at a concentration of 10% by mass: 20 parts by mass and acetylene black as a conductive auxiliary agent: 1.5 parts by mass are kneaded using a biaxial kneader, and NMP is further added to increase the viscosity. Was adjusted to prepare a positive electrode mixture-containing paste.

  A positive electrode was produced in the same manner as in Example 1 except that the above positive electrode mixture-containing paste was used, and a nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

Example 5
The thickness of both surfaces of the positive electrode mixture layer was 65 μm, and the positive electrode length was 1175 mm. The positive electrode current collecting tab position at this time was a distance of S to E of 1135 mm and a distance of S to T of 591 mm (52% of the distance of S to E). A positive electrode was produced in the same manner as Example 1 except for these.
The thickness of both surfaces of the negative electrode mixture layer was 75 μm, and the negative electrode length was 1150 mm. A negative electrode was produced in the same manner as Example 1 except for these.
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode and negative electrode were used.

Example 6
The thickness of both surfaces of the positive electrode mixture layer was 114 μm, and the positive electrode length was 735 mm. The positive electrode current collecting tab position at this time was 693 mm in the distance from S to E and 340 mm in the distance from S to T (49% of the distance from S to E). A positive electrode was produced in the same manner as Example 1 except for these.
The thickness of both surfaces of the negative electrode mixture layer was 135 μm, and the negative electrode length was 710 mm. A negative electrode was produced in the same manner as Example 1 except for these.
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode and negative electrode were used.

Example 7
<Preparation of separator>
Corona discharge treatment (discharge amount 40 W · min / m) on one side of the porous layer (I) PE microporous film (thickness 12 μm, porosity 40%, average pore size 0.08 μm, PE melting point 135 ° C.) ² ) and applying the slurry for forming the porous layer (II) to the treated surface with a microgravure coater and drying to form a porous layer (II) having a thickness of 4 μm on one side of the separator, A laminated separator was produced.
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this separator was used.

Comparative Example 1
A positive electrode material (c1) was produced in the same manner as the positive electrode material (a1) except that the coating with the Al-containing oxide was not performed. Further, a positive electrode material (d1) was produced in the same manner as the positive electrode material (b1) except that the coating with the Al-containing oxide was not performed. The average particle diameters of the positive electrode material (c1) and the positive electrode material (d1) were 27 μm and 7 μm, respectively.

  Next, the positive electrode material (c1) and the positive electrode material (d1) were mixed at a mass ratio of 85:15 to obtain a positive electrode material (4) for battery production. When the volume-based particle size distribution of the obtained positive electrode material (4) was confirmed by the above method, the average particle diameter was 25 μm, and it peaked at each of the average particle diameters of the positive electrode material (c1) and the positive electrode material (d1). Two peaks with a top were observed.

  Then, a positive electrode was produced in the same manner as in Example 1 except that the positive electrode material (4) was used instead of the positive electrode material (1), and the nonaqueous electrolyte 2 was prepared in the same manner as in Example 1 except that this positive electrode was used. A secondary battery was produced.

Comparative Example 2
Except for changing Al _{(NO 3)} the amount of 3 · 9H ₂ O to 0.0513g was prepare a positive electrode material in the same manner as the positive electrode material (a1) (c2). With respect to the positive electrode material (c2) obtained, its average particle diameter was measured by means of the method as described before, thereby finding that it was 27 μm.

Also, except for changing the Al _{(NO 3)} the amount of 3 · 9H ₂ O in 0.257g is to prepare a positive electrode material (d2) in the same manner as the positive electrode material (b1). With respect to the positive electrode material (d2) obtained, its average particle diameter was measured by means of the method as described before, thereby finding that it was 7 μm.

Next, the positive electrode material (c2) and the positive electrode material (d2) were mixed at a mass ratio of 85:15 to obtain a positive electrode material (5) for battery production. When the average coating thickness of the Al-containing oxide on the surface of the obtained positive electrode material (5) was measured by the above method, it was 100 nm. Moreover, when the composition of the film was confirmed by element mapping when measuring the average coating thickness, the main component was Al ₂ O ₃ . Furthermore, when the volume-based particle size distribution of the positive electrode material (5) was confirmed by the above method, the average particle diameter was 25 μm, and peak tops were observed at the respective average particle diameters of the positive electrode material (c2) and the positive electrode material (d2). Two peaks were observed with

  Then, a positive electrode was produced in the same manner as in Example 1 except that the positive electrode material (5) was used instead of the positive electrode material (1). A secondary battery was produced.

Comparative Example 3
The positive electrode mixture-containing paste prepared in the same manner as in Example 1 was applied to both surfaces and a part of one surface of an aluminum foil (positive electrode current collector) having a thickness of 12 μm as shown in FIG. The positive electrode mixture layer was formed on both surfaces of the aluminum foil. Then, the press process was performed and the thickness and density of the positive mix layer were adjusted. The positive electrode mixture layer in the obtained positive electrode had a thickness of both sides of 79 μm. As shown in FIG. 4, an aluminum positive electrode current collecting tab (width 5 mm, thickness 0.08 mm, cross-sectional area 0.4 mm) on the aluminum foil exposed portion (uncoated portion) at the end in the length direction of the current collector ² ) was welded to produce a strip-like positive electrode having a length of 1000 mm and a width of 52 mm having a positive electrode current collecting tab.
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode was used.

Comparative Example 4
The negative electrode mixture-containing paste produced in the same manner as in Example 1 was applied to both sides of a copper foil (negative electrode current collector) having a thickness of 8 μm as shown in FIG. 5 and then vacuum-dried at 120 ° C. for 12 hours. It went and formed the negative mix layer on both surfaces and one part single side | surface of copper foil. Thereafter, press treatment is performed to adjust the thickness and density of the negative electrode mixture layer, and as shown in FIG. 5, the exposed portion of copper foil (uncoated portion) at the center in the length direction of the negative electrode current collector A negative electrode current collector tab made of nickel was welded to a belt-shaped negative electrode having a length of 980 mm and a width of 53 mm. The negative electrode mixture layer in the obtained negative electrode had a thickness of 92 μm on both sides. In addition, the positive electrode mixture-containing paste produced in the same manner as in Example 1 was disposed so that the negative electrode mixture layer opposed to the portion where the positive electrode mixture layer was present with an area margin was disposed. An uncoated portion of the negative electrode is provided in the central portion in the longitudinal direction of the electric body, and an uncoated portion of the positive electrode in which a positive electrode mixture layer does not exist in a portion facing the negative electrode is provided wider than the uncoated portion of the negative electrode, After apply | coating to both surfaces and one part single side | surface of the aluminum foil (positive electrode collector) whose thickness is 12 micrometers, vacuum drying was performed at 120 degreeC for 12 hours, and the positive mix layer was formed on both surfaces of the aluminum foil. Then, the press process was performed and the thickness and density of the positive mix layer were adjusted. The positive electrode mixture layer in the obtained positive electrode had a thickness of both sides of 79 μm.
A nonaqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that this positive electrode and negative electrode were used.

  Each battery produced in Examples and Comparative Examples was evaluated by the following evaluation methods. Table 1 shows the configuration of each battery of the comparative example of the example, and Table 2 shows the evaluation results.

<Battery capacity during 1C discharge>
By discharging at a constant current (hereinafter referred to as CC) to 2.75 V at a current value of 1 C, the battery was once completely discharged. Next, constant current constant voltage (hereinafter referred to as CCCV) charging was performed up to 4.35V. The CC charging current value was 1 C, and the charging end current value was 0.05 C. Subsequently, CC discharge was performed up to 2.75 V at a current value of 1 C, and the discharge capacity at that time was measured. The value obtained by dividing the integrated value of the discharge curve from the start of discharge to the end of discharge when the discharge curve is drawn with the discharge capacity on the horizontal axis and the discharge voltage on the vertical axis is the energy density per weight.

<Battery surface temperature during 5C discharge>
CC was discharged to 2.75 V at a current value of 1 C, and once completely discharged. Next, CCCV charge was performed up to 4.35V. The CC charging current value was 1 C, and the charging end current value was 0.05 C. Subsequently, CC discharge was performed up to 2.75 V at a current value of 5 C, and the surface temperature of the battery at that time was measured.

<Capacity maintenance ratio at 1C discharge after 500 cycles of 5C discharge>
By discharging at a constant current (hereinafter referred to as CC) to 2.75 V at a current value of 1 C, the battery was once completely discharged. Next, constant current constant voltage (hereinafter referred to as CCCV) charging was performed up to 4.35V. The CC charging current value was 1 C, and the charging end current value was 0.05 C. Subsequently, CC discharge was performed up to 2.75 V at a current value of 1 C, and the capacity at this time was defined as the initial discharge capacity. Next, CCCV charge was performed up to 4.35V. The CC charging current value was 1 C, and the charging end current value was 0.05 C. Subsequently, CC discharge was performed to 2.75 V at a current value of 5C. This charge / discharge condition was set to 1 cycle and repeated 500 cycles. Thereafter, constant current and constant voltage (hereinafter referred to as CCCV) charging was performed up to 4.35V. The CC charging current value was 1 C, and the charging end current value was 0.05 C. Subsequently, CC discharge was performed up to 2.75 V at a current value of 1 C, and the discharge capacity at that time was defined as the discharge capacity after 500 cycles. In Table 2, the capacity retention rate of each comparative example is shown as a percentage obtained by dividing the discharge capacity after 500 cycles by the initial discharge capacity.

  The present invention is applied to a non-aqueous electrolyte secondary battery.

DESCRIPTION OF SYMBOLS 1 Positive electrode 13 Positive electrode current collection tab N Uncoated part C Center part 2 Negative electrode 23 Negative electrode current collection tab 100 Nonaqueous electrolyte secondary battery

Claims (8)

A non-aqueous secondary battery having a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte,
The positive electrode is coated with a positive electrode mixture layer containing a positive electrode active material on a positive electrode current collector,
A positive electrode material in which the surfaces of the positive electrode active material particles are coated with an Al-containing oxide is used,
The average coating thickness of the Al-containing oxide is 5 to 50 nm,
The positive electrode and the negative electrode have a positive electrode current collecting tab and a negative electrode current collecting tab, respectively, are stacked via the separator and wound in a spiral shape,
The positive electrode current collecting tab is disposed at a position of 30 to 70% of a distance from one end of the positive electrode mixture layer to the other end in the length direction of the positive electrode,
The non-aqueous secondary battery, wherein the negative electrode current collecting tab is disposed at an end portion in a length direction of the negative electrode.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the positive electrode current collecting tab is arranged in an uncoated portion where the positive electrode mixture layer is not coated on the positive electrode current collector.   The positive electrode active material contained in the positive electrode material is lithium cobalt oxide containing at least Co, Mg, and at least one element M selected from the group consisting of Ni, Mn, Ti, and Al. The nonaqueous electrolyte secondary battery according to claim 1 or 2.   The positive electrode is formed by using lithium nickelate containing Ni and Co and an element M2 selected from the group consisting of Mg, Mn, Ba, W, Ti, Zr, Mo and Al together with the positive electrode material. The nonaqueous secondary battery according to claim 1, wherein the nonaqueous secondary battery is provided.   The said positive electrode current collection tab is arrange | positioned only in the uncoated part of the said positive electrode active material in the center part of the length direction of the said positive electrode, The any one of Claims 1-4 characterized by the above-mentioned. Non-aqueous secondary battery.   6. The non-aqueous secondary battery according to claim 1, wherein only one of the negative electrode current collecting tabs is disposed at an end portion in a length direction of the negative electrode. The non-aqueous electrolyte secondary battery according to claim 1, wherein the total thickness of the positive electrode mixture layer is 60 to 120 μm. The non-aqueous electrolyte secondary battery according to claim 1, wherein the total thickness of the negative electrode mixture layer is 70 to 130 μm.

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