JP2008282799A - Non-aqueous secondary battery electrode and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce and prevent unsafety due to an internal short-circuit or the like due to high capacity of a non-aqueous secondary battery. <P>SOLUTION: In a non-aqueous secondary battery, a thickness of an insulator 12 in an active material non-forming region 2 contacting with a negative plate 20 via a separator 50 is formed thicker than that of the insulator 12 in an active-material forming region 1 formed with a positive-electrode active material 13. As a result, even if an internal short-circuit due to mixing of foreign matter into the inside of a battery occurs, it prevents a large current from continuously flowing between the negative plate 20 and the active material non-forming region 2 of a positive plate 10. Accordingly, it is possible to improve battery safety without deteriorating battery electrical performance. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous secondary battery electrode, and more particularly to an electrode having excellent safety for a lithium secondary battery and a method for producing the same.

  In recent years, there is an increasing need for higher functionality and downsizing of electronic devices such as portable devices. In order to cope with higher functionality and downsizing of electronic devices, lithium secondary batteries used for power supplies are also required to have higher rates due to higher capacity, higher safety, and lower resistance.

  Conventionally, lithium secondary batteries have been manufactured by applying a slurry dispersed in a solvent together with a binder and a conductive agent as a positive electrode active material or a negative electrode active material on a current collector, or directly on a current collector by sputtering or vapor deposition. It is produced by using a positive electrode plate and a negative electrode plate produced by forming a material layer, winding or laminating them via a separator and an electrolytic solution, and joining a lead to each electrode plate by welding or the like. ing.

  In the lithium secondary battery, when foreign matter is mixed in the battery, a small hole is generated in the separator due to the collapse, which may cause an internal short circuit. Usually, a lithium secondary battery has a non-formation region of an active material in which a mixture containing an active material is not applied to the electrode plate because the current collecting lead is welded to the outer peripheral side of the electrode plate. When the internal short circuit occurs between the active material non-forming region of the positive electrode plate and the active material forming region of the negative electrode plate, the end of the active material forming region of the positive electrode plate and the negative electrode plate If it occurs between the active material formation region and the positive electrode plate active material non-formation region and the negative electrode plate active material non-formation region. When this occurs due to the involvement of a non-formed region of the substance, there is a problem that a particularly large current flows and may cause battery heat generation.

  For example, Patent Document 1 proposes to apply a thin film of carboxymethyl cellulose (CMC) to the entire surface of the positive electrode plate in order to deal with the problem of causing the battery heat generation.

  Further, in Patent Document 2, from the viewpoint of improving cycle characteristics, at least a part of the non-opposing portion of the negative electrode or the positive electrode located at the start and / or end of winding of the electrode group is made of an insulating resin insoluble in the electrolytic solution. A covering battery has been proposed.

  Moreover, in patent document 3, an uncoated part is provided in the inner peripheral part and outer peripheral part of a positive electrode plate, the coating part edge part of a positive electrode outer peripheral part, and at least negative electrode active material of a positive electrode plate outer peripheral part uncoated part It has been proposed to continuously apply an insulating material, particularly a fluorine-based resin, to a part or the entire surface including the facing part.

  Further, in Patent Document 4, a positive electrode made of a lithium composite oxide, a negative electrode, and an inorganic oxide filler bonded to at least one surface selected from the positive electrode and the negative electrode, particularly α-alumina particles and a film binder. A lithium secondary battery made of a porous film, a separator interposed between a positive electrode and a negative electrode, and a non-aqueous electrolyte has been proposed.

  Moreover, in patent document 5, as an electrical power collector which can improve adhesiveness with an electrode active material, arithmetic mean roughness Ra which shows the roughness of a surface is 0.3 micrometer or more and 1.5 micrometers or less, for example, maximum height A current collector is proposed in which an oxide film having a withstand voltage of 0.5 V to 2.0 V is formed on the surface of an aluminum foil having an Ry of 0.5 μm to 5.0 μm.

Moreover, in patent document 6, by providing an oxide film on the current collector surface, a uniform mixture layer that suppresses the corrosion reaction of the current collector base is formed, and good battery characteristics can be obtained on the surface. Dielectric strength is 2
. A current collector for a non-aqueous electrolyte secondary battery having an oxide layer of 1 V or higher has been proposed.
JP 2000-357505 A JP-A-7-130389 JP 2005-310619 A JP 2005-327680 A Japanese Patent No. 3444769 JP 2005-259682 A

  However, the technique of applying the CMC thin film to the entire surface of the positive electrode plate can improve the safety, but the electrical characteristics of the battery are simultaneously reduced by the resistance of the formed thin film, and the energy density per volume is reduced. It was also causing a new problem.

  In addition, a battery having a structure in which at least a part of the non-opposing portion of the negative electrode or the positive electrode is covered with an insulating resin insoluble in the electrolytic solution covers the entire unformed region of the positive electrode active material that is likely to cause battery heat generation. It is not effective for a short circuit with the largest heat generation.

  In addition, a battery in which an uncoated portion is provided on the inner and outer peripheral portions of the positive electrode plate and an insulating material, in particular, a fluorine-based resin is continuously applied to a part or the entire surface including a portion facing the negative electrode active material is insulated. Since the oxidation resistance and heat resistance of the conductive resin are low, there is a limit to increasing the end-of-charge voltage for high capacity.

  In addition, in porous membranes composed of inorganic oxide fillers, especially α-alumina particles and membrane binders, the charge termination is terminated to increase the capacity because the membrane binders have low oxidation resistance and heat resistance. There is a limit to increasing the voltage.

  In addition, the structure in which an oxide film having a withstand voltage of 0.5 V or more and 2.0 V or less is provided on the surface of the aluminum foil is effective in improving the adhesion between the aluminum foil and the active material. Since it remains low, there is a problem in the corrosion suppression effect when the end-of-charge voltage is increased for higher capacity, that is, safety.

  Further, the structure in which an oxide film having a withstand voltage of 2.1 V or more is provided on the surface of the aluminum foil is improved against a corrosion-inhibiting effect and a short circuit with the largest heat generation. There is a limit to the improvement in safety due to the fusing function of the foil.

  In order to solve the above problems, an electrode for a nonaqueous secondary battery of the present invention is provided with an insulator containing a metal oxide on a current collector, and the current collector is an active material on the insulator. And an active material non-formation region where the active material is not provided on the insulator, and the thickness of the insulator in the active material non-formation region is The active material forming region is configured to have a thickness equal to or greater than the thickness of the insulator.

With the above configuration, the contact resistance between the positive electrode plate and the negative electrode plate in the active material non-formation region is larger than that of the conventional non-aqueous secondary battery electrode, and the positive electrode active material and the positive electrode in the active material formation region The contact resistance with the current collector can be reduced.

  According to the electrode for a non-aqueous secondary battery of the present invention, when an internal short circuit occurs due to foreign matter mixing inside the battery, a large current does not flow between the active material non-formation region of the positive electrode plate and the negative electrode plate. Therefore, the safety of the battery can be improved without degrading the electrical performance of the battery.

  Hereinafter, an electrode for a nonaqueous secondary battery and a method for manufacturing the same according to an embodiment of the present invention will be described with reference to the drawings.

(Embodiment)
<Battery structure>
FIG. 1 is a schematic cross-sectional view of a battery according to an embodiment of the present invention. Similar to a general secondary battery, in the battery according to the embodiment of the present invention, the positive electrode plate 10 and the negative electrode plate 20 are arranged via the separator 50. The positive electrode plate 10 includes a positive electrode current collector 11, an insulator 12 formed on the positive electrode current collector 11, and a positive electrode active material 13 formed on the insulator 12. The positive electrode current collector 11 includes an active material formation region 1 where a positive electrode active material is formed and an active material non-formation region 2 where a positive electrode active material is not formed. A positive electrode terminal 30 having an insulator 31 on the surface thereof is connected to a part of the active material non-formation region 2. The negative electrode plate 20 includes a negative electrode current collector 21, a negative electrode active material 22 formed on the negative electrode current collector 21, and a negative electrode terminal 40 connected to the negative electrode current collector 21. The arithmetic average roughness in the active material formation region 1 of the positive electrode current collector 11 is configured to have an arithmetic average roughness equal to or greater than the arithmetic average roughness in the active material non-formation region 2. This arithmetic average roughness (Ra) is defined in Japanese Industrial Standard (JISB 0601-1994), and can be measured by, for example, a contact type or laser type surface roughness meter.

<Method for Manufacturing Positive Electrode Plate 10>
Next, the manufacturing method of the said positive electrode plate 10 is demonstrated in detail as an electrode in this Embodiment.

2 and 3 are schematic views showing a cross section of the positive electrode plate 10 according to the embodiment of the present invention. The material used as the positive electrode current collector 11 is made of a metal foil mainly composed of aluminum in order to improve the fusing property, the ease of processing the surface by a pressure press, and the control of the surface roughness by etching. It is preferable to use it. Therefore, as the material of the positive electrode current collector 11, a metal foil mainly composed of aluminum, for example, alloy numbers 1085, 1N30, and 3003 described in JIS standard H4000 are used. The metal foil mainly composed of aluminum is formed into a thin foil shape from 10 μm to 50 μm by rolling, and the arithmetic average roughness of the surface is about 0.05 μm to 0.15 μm. In order to increase the arithmetic average roughness of the surface above the above numerical value, a blasting method, a chemical etching method or an electrolytic etching method in an acid solution such as hydrochloric acid, sulfuric acid or nitric acid, or an alkali solution such as sodium hydroxide is used. . Note that the electrolytic etching method can be performed by changing the applied current such as direct current, alternating current, and pulse in accordance with a desired surface shape, and thus is a preferable method as a method for controlling the arithmetic average roughness of the surface. Therefore, the anode (positive electrode) oxidation and electrolytic etching apparatus shown in FIG. First, the positive electrode current collector 11 is immersed in an electrolytic cell 101 filled with an acid aqueous solution, and the vicinity of the active material forming region 1 of the positive electrode current collector 11 is masked with an insulator 103 such as alumina, whereby the positive electrode current collector is obtained. The cathode 102 is disposed so as to face the electrode 11, and a direct current or an alternating current is passed between the current collector 11 and the cathode 102 by the power source 104. At this time, since the active material non-formation region 2 of the positive electrode current collector 11 is selectively etched, the arithmetic average roughness in the active material non-formation region 2 can be increased.

  In order to selectively reduce the arithmetic average roughness in the active material forming region 1, the entire surface of the positive electrode current collector 11 is etched once to the same roughness, or after the insulator 12 is formed, This can be dealt with by performing a method in which the electric body 11 is formed by pressure pressing with a mold having a predetermined surface roughness. In addition, when press-pressing with a metal mold | die, the improvement of the pattern and positional accuracy of an active material formation area can be aimed at. Furthermore, when the insulator 12 is formed and the positive electrode current collector 11 is formed and then press-pressed with a mold, defects in the insulator 12 occur in the pressed positive electrode current collector 11, and the non-pressed portion of the positive electrode current collector 11 is formed. A dense insulator 12 remains on the current collector 11. As a result, for example, when an aluminum foil is used as the positive electrode current collector 11, the positive electrode plate 10 having a low contact resistance with the active material and a low solubility of the positive electrode current collector 11 is obtained.

  When the arithmetic average roughness Ra of the active material formation region 1 is R1, and the arithmetic average roughness Ra of the active material non-formation region 2 is R2, R1 is set to 0.05 μm or more and 2 μm or less, and R2 is set to 3 μm or less. Thus, the electrical bonding between the positive electrode active material 13 and the positive electrode current collector 11 can be improved, and the fusing function of the electrode plate between the active material non-formed region 2 and the negative electrode plate 20 can be improved. In order to further improve the electrical joining and fusing function, it is preferable to set R1 to 0.3 μm to 2 μm and R2 to 0.4 μm to 3 μm.

  For example, when an aluminum metal foil is used as the positive electrode current collector 11, an aluminum oxide film is formed on the surface due to the effects of drying treatment after molding, storage conditions (temperature, humidity, etc.), etc. The thickness of the oxide film is about 0.7 nm to 2.1 nm. The breakdown voltage of the oxide film is about 0.5 V to 1.5 V in measurement in an electrolytic solution such as ammonium adipate. In addition, the pressure resistance can be further improved by selectively increasing the thickness of the insulator 12 in the active material non-formation region 2 of the positive electrode current collector 11. For example, the insulator 12 can be manufactured by an anodic oxidation method using the apparatus shown in FIG. The procedure is to immerse the positive electrode current collector 11 in an electrolytic cell 101 filled with a solution in which an acid such as phosphoric acid, boric acid or adipic acid or an ammonium salt such as phosphoric acid, boric acid or adipic acid is dissolved. To do. Next, the vicinity of the active material formation region 1 of the positive electrode current collector 11 is masked with an insulator 103 such as alumina, and a cathode 102 is disposed so as to face the positive electrode current collector 11. A voltage is applied by a power source 104 in accordance with the desired thickness of the insulator 12 therebetween.

  By the above procedure, a positive electrode current collector in which the arithmetic average roughness in the active material formation region 1 is equal to or greater than the arithmetic average roughness in the active material non-formation region 2 is produced.

As another method of increasing the thickness of the insulator 12 in the active material non-formation region 2, an insulator can be formed by an aerosol deposition method. FIG. 5 shows a film forming apparatus using the aerosol deposition method. As shown in FIG. 5, the aerosol generator 203 is connected to an argon gas cylinder 201 as a gas supply source for generating aerosol through a gas transport pipe 202. The aerosol generator 203 is connected to a nozzle 205 installed in the structure formation chamber 207 via an aerosol transport pipe 204. The aerosol generator 203 stores powder to be the insulator 12 and generates an aerosol of the insulator 12 by a gas such as argon gas supplied. A positive electrode current collector 11 serving as a substrate fixed to the substrate holder 206 is disposed at a position facing the tip of the nozzle 205. Further, a vacuum pump 208 is connected to the structure forming chamber 207 via a suction pipe 210 and a particulate collection container 209 as an exhaust mechanism of the structure forming chamber 207. In addition, by using an XY stage that can be moved in a plane as the substrate holder 206, it is possible to change the aerosol collision position on the substrate, and the insulator 12 is formed only in the active material non-formation region 2 It is also possible to carry out selectively. In the aerosol deposition method, since the aerosol is directly injected and formed on the positive electrode current collector 11 by a differential pressure or the like, a dense insulator 12 that does not contain a binder or the like can be obtained, and further, before the active material 13 is formed. It can be carried out regardless of the formation.

  Note that an oxide such as aluminum, zirconium, yttrium, or silicon can be used as the insulator 12, but alumina is particularly preferable in consideration of adhesion to the current collector 11, production, and raw material costs.

  An active material 13 is formed on the positive electrode current collector 11 produced as described above to produce an electrode. The manufacturing method is the same as the procedure for forming the active material 13 in the conventional electrode for a non-aqueous secondary battery, and the detailed description thereof is omitted.

  In addition, when producing the electrode for lithium secondary batteries, the positive electrode active material 13 uses lithium-containing transition metal oxides, such as lithium nickelate and lithium cobaltate, and its solid solution as a lithium-containing transition metal oxide. And is represented by the general formula (Formula 1).

  The element M is at least one element selected from the group consisting of Ni and Co. The element L is at least one selected from the group consisting of alkaline earth metal elements, transition elements other than Ni and Co, rare earth elements, IIIb group elements, and IVb group elements.

  The element L preferably contains at least one element selected from the group consisting of Al, Mn, Ti, Mg, Zr, Nb, Mo, W, and Y. These elements may be included singly or two or more elements may be included. Furthermore, it is desirable that the element L is a transition element such as Mn. The preparation method can be synthesized by firing an oxide or hydroxide having a predetermined metal element ratio in an oxidizing atmosphere.

  Moreover, it is desirable that the coefficients x and y in the general formula (Formula 1) satisfy 0.85 ≦ x ≦ 1.25 and 0 ≦ y ≦ 0.50. In particular, the range of x representing the lithium content increases or decreases depending on the charge / discharge of the battery, but 0.85 ≦ x ≦ 1 in the fully discharged state, the initial state immediately after the battery assembly, or immediately after the synthesis of the lithium composite oxide. .35, and 1.02 ≦ x ≦ 1.25 is more preferable.

  In addition to the lithium-containing transition metal oxide, the layer of the positive electrode active material 13 is made of, for example, artificial graphite, natural graphite, a conductive agent such as fibrous carbon or carbon black, polyvinylidene fluoride, polytetrafluoroethylene, or the like. In general, a binder is included.

<Battery components>
Next, the negative electrode plate 20, the separator, the solvent, the terminal, the battery case, and the like, which are preferable constituent members that constitute the battery other than the positive electrode plate 10 described above, will be described.

The negative electrode current collector 21 constituting the negative electrode plate 20 can be made of a foil having a thickness of 5 μm to 50 μm, such as copper or nickel, from the viewpoint of improving adhesion with an insulator and reducing contact resistance with an active material. It is preferable that the surface is roughened in advance, such as electrolytic copper foil. The active material 22 formed on the negative electrode current collector 21 can be made of a compound such as graphite, amorphous carbon capable of occluding and releasing Li, or Sn, Si, SiO, etc. capable of being alloyed with Li. . Further, the layer of the negative electrode active material 22 is, for example, artificial graphite, natural graphite, a conductive agent such as fibrous carbon or carbon black, polyvinylidene fluoride, a copolymer rubber of styrene and butadiene, etc. The binder may also be included. In addition, it cannot be overemphasized that the manufacturing procedure of the negative electrode plate 20 can apply the manufacturing procedure of said positive electrode plate 10. FIG.

Further, when a battery is formed using the positive electrode plate 10 and the negative electrode plate 20, the separator is not particularly limited as long as the interface portion in contact with the positive electrode is made of polypropylene. For example, a sheet or non-woven fabric made from a polyolefin polymer such as polypropylene or polyethylene alone or in combination, a polyaramid polymer, glass fiber, or the like can be used. In general, an insulating microporous thin film having a high ion permeability and a predetermined mechanical strength is preferable. The pore diameter of the separator is preferably in a range in which the active material, the binder, and the conductive agent detached from the electrode sheet do not permeate, for example, 0.01 to 1 μm is desirable. As for the thickness of a separator, 5-300 micrometers is generally used. The porosity is determined according to the permeability of electrons and ions required as battery characteristics, and the piercing strength of a film such as a battery material or a separator, but is generally 20 to 90%. desirable. The separator may be a multilayer film in which a plurality of single layer films are stacked. In the case of a multilayer film, it is desirable to develop a so-called shutdown function at a temperature of 120 to 145 ° C. in order to increase the safety of the battery. When the shutdown function is operated at a temperature lower than 120 ° C., there is a risk that the battery function is lost during high temperature storage. When the shutdown function is operated at a temperature higher than 145 ° C., there is a risk that the thermal runaway reaction of the battery cannot be suppressed. In order to exhibit the shutdown function in the above temperature range, it is desirable to include a single layer film mainly composed of polyethylene. Furthermore, in order to improve the heat resistance safety of the battery, a single layer film mainly composed of an inorganic material such as SiO ₂ or Al ₂ O ₃ can be included.

Examples of non-aqueous solvents include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, and non-cyclic carbonates such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate. Can be used. One or two or more of these are used in combination, and it is particularly preferable to use a mixed system of a cyclic carbonate and an acyclic carbonate as a main component. Furthermore, as a lithium salt dissolved in a non-aqueous solvent, for example, LiClO ₄ , LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li (CF ₃ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) _2, etc. Can be used. Incidentally, it is also possible to use alone or in combination of two or more lithium salts in the electrolyte solution or the like, particularly, more preferably be included LiPF _6.

  Moreover, the gel electrolyte carry | supported by the organic polymer can also be used as a non-aqueous electrolyte. Examples of the organic polymer that supports the non-aqueous electrolyte include polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyhexafluoropropylene, polyacrylate, polymethacrylate, and derivatives thereof.

  Moreover, as a terminal of this invention, the positive electrode terminal 30 has preferable aluminum, and the negative electrode terminal 40 has preferable nickel and copper. In particular, aluminum is a preferable material because the oxide film 31 can be easily thickened by the oxide film anodic oxidation method, so that the insulating property can be easily increased and a low resistance connection can be easily made by resistance welding or the like. Further, in order to prevent an electrical short circuit between the positive electrode terminal and the negative electrode plate 20 and further improve safety, these terminals are oxidized with a thickness equal to or greater than the thickness of the insulator 12 in the active material non-formation region 2. It is desirable to have the film 31 and an insulator layer.

  In addition, as the battery case in the present invention, a metallic battery can such as Al or Fe or a laminate film obtained by laminating a resin film on both sides of a metal foil can be used as a bag. A battery case made of a laminate film can also be used in order to meet the demand for a reduction in thickness and weight.

<Characteristics and effects of positive electrode plate 10>
Next, the characteristic structure of the positive electrode plate 10 shown in the embodiment of the present invention and the effects thereof will be described.

  A feature of the configuration is that the thickness of the insulator 12 in the active material non-formation region 2 of the positive electrode plate 10 is configured to be equal to or greater than the thickness of the insulator in the active material formation region 1. With this configuration, the contact resistance between the positive electrode plate 10 and the negative electrode plate 20 in the active material unformed region 2 is increased, and the contact resistance between the positive electrode active material 13 and the positive electrode current collector 11 in the active material forming region 1 is increased. Can be small. As a result, when the battery is configured, a large current does not flow between the active material non-formation region of the positive electrode plate and the negative electrode plate when an internal short circuit occurs due to contamination of foreign matter inside the battery. Battery safety can be improved without degrading electrical performance.

  In addition, when the thickness of the insulator 12 in the active material non-formation region 2 is larger than the thickness of the insulator 12 in the active material formation region 1, the arithmetic average roughness R2 of the positive electrode current collector 11 in the active material non-formation region 2 is The positive electrode current collector 11 in the active material forming region 1 is preferably configured to have an arithmetic average roughness R1 or more. When R1 and R2 are the same, the contact resistance between the positive electrode plate 10 and the negative electrode plate 20 in the active material non-formation region 2 is increased, and the positive electrode active material 13 and the positive electrode current collector in the active material formation region 1 The contact resistance with 11 can be reduced. Further, when R2 is larger than R1, a fusing function is developed at the time of a minute short circuit of the active material non-forming region 2, that is, at the protruding portion of the positive electrode current collector 11 with a minute current. Further, when a large current flows exceeding the current at the time of a short circuit, the positive electrode current collector 11 is melted, so that safety can be further improved. Note that fusing refers to a mechanism that cuts off the current flowing through the conductor by melting the conductor by Joule heat when a large current flows through the conductor.

  Moreover, when the thickness of the insulator 12 in the active material non-formation region 2 is the same as the thickness of the insulator 12 in the active material formation region 1, the arithmetic average roughness R2 of the positive electrode current collector 11 in the active material non-formation region 2 is The positive electrode current collector 11 in the active material forming region 1 is preferably configured to be larger than the arithmetic average roughness R1. When the thickness of the insulator 12 in the active material formation region 1 and the thickness T of the insulator 12 in the active material non-formation region 2 are the same, the arithmetic average roughness R2 of the positive electrode current collector 11 in the active material non-formation region 2 is By making the arithmetic mean roughness R1 of the positive electrode current collector 11 in the active material forming region 1 larger than the arithmetic mean roughness R1, the active material non-formed region 2 is blown at the protrusion of the positive electrode current collector 11 at a minute short circuit, that is, at a small current. Express function. Further, when a large current flows exceeding the current at the time of a short circuit, the positive electrode current collector 11 is melted, so that safety can be further improved.

  Further, in order to improve the electrical connection between the positive electrode active material 13 and the positive electrode current collector 11 and to improve the insulation between the active material non-formation region 2 and the negative electrode plate 20, an insulator in the active material formation region 1 is used. Preferably, the thickness of 12 is 3 nm or more and 14 nm or less. At this time, the thickness of the insulator 12 in the active material non-formation region 2 is preferably 3 nm or more and does not exceed the thickness of the positive electrode active material.

  In addition, the shape of the battery which comprises is not specifically limited, Any of cylindrical shape, a flat shape, and a square shape may be sufficient.

Further, in the battery using the positive electrode plate 10 according to the present invention, the function of preventing a short circuit between the positive electrode plate 10 and the negative electrode plate 20 can be improved, so that the end-of-charge voltage of the battery is high between 4.4V and 5.0V. A non-aqueous secondary battery can be produced. In addition, as a method for forming the insulator 12, the anodizing method and the aerosol deposition method, which are binder-free forming methods, do not cause oxidative degradation of the binder, so that the end-of-charge voltage is 4.4 V or more and 5. This is suitable as a method for forming the insulator 12 in the current collector used at 0 V or less.

  Next, examples of the positive electrode plate 10 of the present invention and examples of the internal short circuit test of the battery configured using the manufactured positive electrode plate 10 and comparative examples will be described with reference to the drawings.

Example 1
In Example 1, the arithmetic average roughness R1 of the active material formation region 1 and the arithmetic average roughness R2 of the active material non-formation region 2 are the same, and the active material non-formation region is greater than the thickness of the insulator 12 in the active material formation region 1 A positive electrode plate 10 having a large thickness of the insulator 12 was prepared. The current collector 11 used is JIS alloy number 1N30, the in-plane variation is 0.05 μm to 0.15 μm, the average value is 0.11 μm, and the natural oxide film thickness as the insulator 12 is about 0.5 nm to 1 nm. It is an aluminum foil made of Toyo Foil with a thickness of 20 μm. That is, in Example 1, R1 and R2 are 0.11 μm on average.

<Formation of insulator 12 on positive electrode current collector 11>
The insulator 12 was formed on the positive electrode current collector 11 by an anodizing method using the apparatus shown in FIG. First, before anodizing, the aluminum foil is immersed in an aqueous solution of 3% by weight NaOH and a liquid temperature of 40 ° C. for 20 seconds, then washed with water, dried at 400 ° C. for 1 minute, and the surface of the aluminum foil. Was cleaned. Thereafter, a 10% by weight ammonium adipate aqueous solution was placed in the electrolytic bath 101, the temperature of the solution was set to 80 ° C., and an aluminum foil and a carbon plate serving as the cathode plate 102 were immersed therein. Next, with the insulating plate 103 removed, an aluminum foil was used as an anode and a cathode plate 102 was used as a cathode, and a DC voltage of 2.4 V was applied for 10 minutes to form an insulator 12 having a thickness of 3 nm. Thereafter, the active material forming region 1 is sandwiched between the insulating plates 103, and a 10.2 V DC voltage is applied for 15 minutes to form an insulator 12 in the active material non-formed region 2 having a thickness of 14 nm, washed with water, and then 400 ° C. Dry for 2 minutes. That is, in Example 1, the thickness of the insulator 12 in the active material formation region 1 is 3 nm, and the thickness of the insulator 12 in the active material non-formation region 2 is 14 nm.

<Synthesis of positive electrode active material>
A raw material solution was prepared by dissolving 3 kg of a mixture of nickel sulfate, cobalt sulfate and aluminum sulfate mixed in a molar ratio of Ni atoms, Co atoms and Al atoms of 80: 15: 5 in 10 liters of water. Got. 400 g of sodium hydroxide was added to the raw material solution to form a precipitate. The precipitate was sufficiently washed with water and dried to obtain a coprecipitated hydroxide.

A predetermined amount of lithium hydroxide was mixed with 3 kg of the obtained Ni—Co—Al coprecipitated hydroxide and calcined at a temperature of 750 ° C. for 10 hours in an oxygen atmosphere with an oxygen partial pressure of 0.5 atm. Then, a Ni / Co-based Li composite oxide (LiNi _0.8 Co _0.15 Al _0.05 O ₂ ) containing Al as the element L was produced. The composite oxide was pulverized using a planetary ball mill having a cobblestone diameter of 2 mm, dried, and further heat-treated in oxygen at 500 ° C. for 10 hours. In addition, active material particles having an average particle diameter of 1.2 μm (measured by a wet laser particle size distribution measuring device manufactured by Microtrack Co., Ltd.) were produced by the treatment.

<Formation of Positive Electrode Active Material 13 in Active Material Formation Region 1>
Using the aerosol deposition apparatus shown in FIG. 5, the active material film was formed in the active material formation region 1. The film forming conditions were as follows: the film forming temperature was 30 ° C., argon was used as the carrier gas, and the carrier gas flow rate was adjusted to 3000 sccm so that the degree of vacuum in the film forming chamber was 100 Pa. A film having an area of 50 mm × 70 mm, a thickness of 70 μm, and a film relative density of about 60% was obtained.

<Preparation of negative electrode plate 20>
3 kg of artificial graphite was stirred together with 200 g of binder (BM-400B) manufactured by Nippon Zeon Co., Ltd., 50 g of carboxymethyl cellulose (CMC) and an appropriate amount of water in a double-arm kneader to prepare a negative electrode mixture paste. . This paste was applied to a 12 μm-thick copper foil serving as the negative electrode current collector 21 so that the coating area was 54 mm × 74 mm. Then, it dried and rolled so that total thickness might be set to 70 micrometers, and the negative electrode plate 20 was produced.

<Battery assembly>
As shown in FIG. 1, a 100 μm thick aluminum plate having a natural oxide film of about 1 nm is used as the positive electrode terminal 30 in the active material non-formation region 1 of the positive electrode plate 10, and the active material non-formation region 1 of the negative electrode plate 20. A nickel plate having a thickness of 100 μm was resistance welded to each as a negative electrode terminal 40, and an internal battery was configured through a separator 50. As the separator 50, a composite film of polyethylene and polypropylene (2300 manufactured by Celgard Co., Ltd., thickness 25 μm) was used. The produced internal battery and 5 g of non-aqueous electrolyte were put in a laminate case to produce a non-aqueous secondary battery. The non-aqueous electrolyte is a mixture solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 10:30, with 2% vinylene carbonate, 2% vinyl ethylene carbonate, 5% fluorobenzene, and 5% phosphazene added. Then, a solution obtained by dissolving LiPF6 at a concentration of 1.2 mol / liter was used in the mixed solution.

(Example 2)
In Example 2, the positive electrode plate 10 formed using the aerosol deposition method with the insulator 12 in the active material non-formation region 2 made of alumina was used. Otherwise, the battery was assembled in the same manner as in Example 1. In Example 2, R1 and R2 are 0.11 μm on average, the thickness of the insulator 12 in the active material formation region 1 is 3 nm, and the thickness of the insulator 12 in the active material non-formation region 2 is 2 μm. . The conditions for forming the insulator 12 on the positive electrode current collector 11 will be described below.

<Formation of alumina as insulator 12 on positive electrode current collector 11>
The aluminum foil used as the positive electrode current collector 11 is immersed in an aqueous solution of 3% by weight NaOH and a liquid temperature of 40 ° C. for 20 seconds, then washed with water, dried at 400 ° C. for 1 minute, Cleaning was performed. Thereafter, a 10 wt% ammonium adipate aqueous solution was placed in the electrolytic cell 101 shown in FIG. 4, the liquid temperature was set to 80 ° C., and an aluminum foil and a carbon plate serving as the cathode plate 102 were immersed therein. Next, after the insulating plate 103 is removed, the aluminum foil is used as an anode, the cathode plate 102 is used as a cathode, and a DC voltage of 2.4 V is applied for 10 minutes to form an insulator 12 having a thickness of 3 nm and washed with water. And dried at 400 ° C. for 2 minutes. Then, it was installed in the aerosol deposition apparatus shown in FIG. 5, and an alumina insulator 12 was formed in the active material non-formation region 2.

  The alumina used was α-alumina having an average diameter of 0.5 μm manufactured by Wako Pure Chemical Industries, Ltd. Film formation was performed while adjusting the flow rate of carrier gas at 8000 sccm so that the film formation temperature was 30 ° C., the carrier gas was argon, and the degree of vacuum in the film formation chamber was 100 Pa. An insulating film having a thickness of 2 μm and a film relative density of about 92% was obtained.

(Example 3)
In Example 3, the positive electrode 10 formed by vapor deposition using the insulator 12 in the active material non-formation region 2 as aluminum fluoride was used. Otherwise, the battery was assembled in the same manner as in Example 1. In Example 2, R1 and R2 are 0.13 μm on average, the thickness of the insulator 12 in the active material formation region 1 is 3 nm, and the thickness of the insulator 12 in the active material non-formation region 2 is 2 μm. . The conditions under which the formation of the insulator and the arithmetic surface roughness of the positive electrode current collector 11 are controlled will be described below.

<Formation of aluminum fluoride as the insulator 12 on the positive electrode current collector 11>
Aluminum fluoride with a purity of 99.9% was placed in a tantalum boat, and the film was formed on the aluminum etching foil produced in Example 1 for 10 seconds by a resistance heating method at a film formation rate of 0.3 nm / second. An aluminum halide insulator (insulating film) was formed. Further, the active material forming region 1 is shielded with a stainless steel plate, and similarly, a resistance heating method is used to form a film at a film forming rate of 20 nm / second for 100 seconds, and the active material non-formed region 2 is insulated with 2 μm of aluminum fluoride. An object (insulating film) was formed.

Example 4
In Example 4, the thickness of the insulator 12 is 5 nm for both the active material formation region 1 and the active material non-formation region 2, the arithmetic average roughness R2 of the active material non-formation region 2 is 1.5 μm, and the active material formation region 1 A positive electrode plate 10 having an arithmetic average roughness R1 of 1 μm was used (positive electrode plate 10 as shown in FIG. 3). Otherwise, the battery was assembled in the same manner as in Example 1. In addition, the manufacturing conditions of the positive electrode current collector 11 will be described below.

<Preparation of positive electrode current collector 11>
First, the aluminum foil was immersed in an aqueous solution of 3 wt% NaOH and a liquid temperature of 40 ° C. for 20 seconds, then washed with water and dried at 400 ° C. for 1 minute to clean the aluminum foil surface. Thereafter, a 30 ° C. solution consisting of an aqueous solution of 5% by weight hydrochloric acid and 2% by weight aluminum chloride, the current collector 11 and the cathode plate 102 were immersed in the electrolytic cell 101 shown in FIG. AC etching was performed on the entire surface of the current collector 11 with a wave AC current at a current density of 0.2 A / cm ² for 20 seconds to obtain an aluminum foil with R1 = R2 = 1.5 μm.

Thereafter, in order to reduce the arithmetic average roughness R1 of the active material formation region 1, the active material formation region 1 was pressed at a pressure of 5 MPa per cm ^{2 in} a size of 50 mm × 70 mm, and R1 was set to 1 μm.

(Example 5)
In Example 5, the positive electrode current collector 11 having an arithmetic average roughness R1 in the active material formation region 1 of 2 μm and an arithmetic average roughness R2 in the active material non-formation region 2 of 3 μm was used. In order to obtain the arithmetic average roughness, the etching time by the anodic oxidation method was set to 32 seconds. Note that the thickness of the insulator 12 in the active material formation region 1 and the active material non-formation region 2 is 5 nm. Otherwise, the battery was assembled in the same manner as in Example 1.

(Example 6)
In Example 6, before the insulator 12 is formed on the positive electrode current collector 11, the arithmetic average roughness is increased by electrolytic etching, and then the active material formation region 1 is decreased by the pressurization press. Thereafter, the positive electrode plate 10 in which the insulator in the active material non-formation region 2 was formed by the aerosol deposition method was used. Specifically, the positive electrode current collector 11 produced in Example 4 is used as the positive electrode current collector 11, and is equivalent to the insulator 12 formed on the positive electrode current collector 10 of Example 2 by the aerosol deposition apparatus. An insulator was produced (positive electrode plate 10 as shown in FIG. 2). Otherwise, the battery was assembled in the same manner as in Example 1. In Example 6, R1 is 1 μm, R2 is 1.5 μm, the thickness of the insulator 12 in the active material formation region 1 is 3 nm, and the thickness of the insulator 12 in the active material non-formation region 2 is 2 μm.

(Example 7)
In Example 7, the positive electrode terminal 30 having the insulator 31 with a thickness of 30 nm was used for the positive electrode plate 10 of Example 1. The remaining configuration was the same as in Example 1, and a battery was assembled. In Example 7, R1 and R2 are 0.11 μm on average, and the insulator 1 in the active material formation region 1
2 is 3 nm, and the thickness of the insulator 12 in the active material unformed region 2 is 14 nm. In addition, the production conditions by anodic oxidation of the positive electrode terminal will be described below.

<Preparation by positive electrode terminal anodic oxidation>
An aluminum plate having a thickness of 100 μm is immersed in an aqueous solution of 3% by weight NaOH and a liquid temperature of 40 ° C. for 20 seconds, then washed with water and dried at 400 ° C. for 1 minute to clean the surface of the aluminum plate. It was. Thereafter, a 10 wt% aqueous solution of ammonium adipate was placed in the electrolytic cell 101 shown in FIG. 4, the liquid temperature was set to 90 ° C., and an aluminum foil and a carbon plate serving as the cathode plate 102 were immersed therein. First, with the insulating plate 103 removed, an aluminum plate was used as an anode and a cathode plate 102 was used as a cathode, and a DC voltage of 22 V was applied for 20 minutes to form an insulator 31 having a thickness of 30 nm.

(Comparative Example 1)
In Comparative Example 1, the positive electrode plate 10 of Example 1 in which R1 and R2 are 0.11 μm on average and the thickness of the insulator 12 in the active material formation region 1 and the active material non-formation region 2 is 2.9 nm. Was used as the positive electrode plate 10. The remaining configuration was the same as in Example 1, and a battery was assembled.

(Comparative Example 2)
In Comparative Example 2, the positive electrode plate 10 of Example 4 that was not pressed in the active material forming region 1 was used as the positive electrode plate. Note that R1 and R2 are 1.5 μm, and the thickness of the insulator 12 in the active material formation region 1 and the active material non-formation region 2 is 5 nm. Otherwise, the battery was assembled in the same manner as in Example 1.

<Evaluation>
Using the batteries prepared in Examples 1 to 7 and Comparative Examples 1 and 2, the battery characteristics were evaluated. The evaluation was performed under a constant current charge at 0.05 C, a discharge end voltage of 2.5 V, and a constant current discharge at 0.2 C for 3 cycles under a 20 ° C. environment with a charge end voltage of 4.4 V. Once again, the end-of-charge voltage is set to 4.4 V, constant current charging is performed at 0.05 C, and a 1 mm diameter iron round nail is pierced at a rate of 5 mm / second in an environment where the active material is not formed 2 at a temperature of 20 ° C. A short-circuit test was performed, and the temperature reached after 1 second and 20 seconds in the vicinity of the penetration portion was measured. In addition, the battery produced in Example 4 and Comparative Example 2 also measured the resistance in the film thickness direction per 1 cm ² of the active material formation region of the positive electrode plate. Table 1 shows the evaluation results of battery characteristics.

  Comparing the test results of Example 1 and Comparative Example 1, it can be seen that the temperature of the battery in Example 1 during the internal short circuit test is low. That is, it can be seen that by increasing the thickness of the insulator 12 in the active material formation region 1 compared to the thickness of the insulator 12 in the active material non-formation region 2, the temperature rise of the battery is suppressed and the safety is improved. .

  Comparing the evaluation of Example 1 with Example 2 and Example 3, it was found that the thick and dense insulator 12 was formed in the active material non-formed region 2 by the aerosol deposition method or the vapor deposition method. It can be seen that the temperature rise of the battery is suppressed and the safety is improved. From the evaluation results of Example 2 and Example 3, the same effect can be obtained even if the insulator to be formed is aluminum oxide or aluminum fluoride alone or a mixture of aluminum oxide and aluminum fluoride. I can guess it.

  When the test results of Example 2 and Example 4 are compared, in Example 4, the arithmetic average roughness R2 of the active material non-formation region 2 is larger than the arithmetic average roughness R1 of the active material non-formation region 2; As a result, the temperature increase after 1 second became large. However, since the convex part is melted and opened with a small Joule heat, the temperature after 20 seconds is the same as in Example 2, and it can be seen that the safety has increased as in Example 2. When the electrode plate resistances of Example 4 and Comparative Example 2 are compared, the electrode plate resistance in Example 4 is small. This is an effect obtained by press-pressing the positive electrode current collector 11. The contact resistance between the positive electrode active material 13 and the positive electrode current collector 11 is reduced, and the electrode plate has a low resistance in addition to safety. I understand that.

  Comparing the test results of Example 4 and Example 5, in Example 5, the arithmetic average roughness is larger than Example 4, so the temperature after 20 seconds is lower than Example 4, and the fusing function is more than that of Example 4. Can also be improved.

  When the test results of Example 6 and Example 2 and Example 5 are compared, the configurations of Example 2 and Example 5 are combined in the positive electrode current collector 11 of Example 6, so that Examples 2 and 4 are combined. It can be seen that the temperature rise can be suppressed as compared with the battery.

  Comparing the evaluation of Example 1 and Example 7, the thickness of the insulator 31 of the positive electrode terminal 30 of Example 7 is thicker than the thickness of the insulator 31 of the positive electrode terminal 30 of Example 1, so that the temperature rise It can be seen that a suppressed and safe battery was obtained.

  As described above, by using the positive electrode plate with high safety disclosed by the present invention, it is possible to provide a high energy density lithium secondary battery having a charge end voltage of 4.4 V or more and 5.0 V or less that is required to be more safe. .

  The electrode for a non-aqueous secondary battery and the method for producing the same according to the present invention can obtain a highly safe electrode, so that not only a lithium ion secondary battery having high capacity and excellent safety, but also an electrochemical capacitor It is useful as a device in general using an electrochemical mechanism.

The schematic diagram which shows the cross section of the internal battery in embodiment of this invention The schematic diagram which shows an example of the cross section of the positive electrode plate in embodiment of this invention The schematic diagram which shows an example of the cross section of the positive electrode plate in embodiment of this invention Schematic diagram of an apparatus used for anodization and electrolytic etching in an embodiment of the present invention Schematic of an aerosol deposition apparatus in an embodiment of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Active material formation area | region 2 Active material non-formation area | region 10 Positive electrode plate 11 Positive electrode collector 12 Insulator 13 Positive electrode active material 20 Negative electrode plate 21 Negative electrode collector 22 Negative electrode active material 30 Positive electrode terminal 31 Insulator 40 Negative electrode terminal 50 Separator 101 Electrolytic cell 102 Cathode plate 103 Insulating plate 104 Power supply 201 Gas cylinder 202 Gas delivery pipe 203 Aerosol generation chamber 204 Aerosol delivery pipe 205 Nozzle 206 Substrate holder 207 Structure formation chamber 208 Vacuum pump 209 Fine particle collection container 210 Suction pipe

Claims (11)

A current collector,
An insulator provided on the current collector and including a metal oxide;
Battery active material,
The current collector includes an active material forming region in which the active material is provided on the insulator, and an active material non-forming region in which the active material is not provided on the insulator. An electrode for a non-aqueous secondary battery configured such that the thickness of the insulator in the active material non-formation region is equal to or greater than the thickness of the insulator in the active material formation region. When the thickness of the insulator in the active material unformed region is larger than the thickness of the insulator in the active material formed region,
Arithmetic average roughness of the current collector non-formation region current collector,
The active material forming region is configured to have a roughness equal to or higher than the arithmetic average roughness of the current collector,
The electrode for nonaqueous secondary batteries according to claim 1. The thickness of the active material unformed region insulator is
When the thickness of the insulator in the active material formation region is the same,
Arithmetic average roughness of the current collector non-formation region current collector,
The active material forming region is configured to have a roughness larger than the arithmetic average roughness of the current collector,
The electrode for nonaqueous secondary batteries according to claim 1. The arithmetic mean roughness of the current collector in the active material formation region is 0.05 μm or more and 2 μm or less,
The electrode for non-aqueous secondary batteries according to claim 2 and 3, wherein the current collector in the active material non-formation region is configured to have an arithmetic average roughness of 3 µm or less. The thickness of the insulator in the active material formation region is configured to be 3 nm or more and 14 nm or less,
The electrode for nonaqueous secondary batteries in any one of Claim 1 to 4. The current collector is a foil mainly composed of aluminum;
The electrode for nonaqueous secondary batteries in any one of Claim 1 to 5. The insulator is an oxide mainly composed of alumina;
The electrode for nonaqueous secondary batteries according to any one of claims 1 to 6. The terminal connected to the current collector has an insulator having a thickness greater than or equal to the thickness of the insulator in the active material non-formation region.
The electrode for nonaqueous secondary batteries in any one of Claim 1 to 7. It is comprised using the electrode for nonaqueous secondary batteries in any one of Claim 1 to 8,
The end-of-charge voltage is set at a voltage not lower than 4.4V and not higher than 5.0V.
Lithium secondary battery. The insulator in the active material non-formation region is
Formed by an aerosol deposition method in which an aerosol containing fine particles of brittle material is sprayed onto a substrate under a low vacuum,
The manufacturing method of the electrode for nonaqueous secondary batteries in any one of Claim 1 to 9. The current collector is
Roughening the surface of the current collector;
Forming an insulator on the surface of the current collector;
Manufactured by a process including a step of reducing the arithmetic average roughness of the current collector in the active material formation region by a pressure press,
The manufacturing method of the electrode for nonaqueous secondary batteries in any one of Claim 1 to 10.

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