JP2010146900A - Positive electrode active material for nonaqueous electrolyte secondary battery - Google Patents

Abstract

Provided is a positive electrode active material that can be used for a non-aqueous electrolyte secondary battery that requires a very high discharge capacity, such as a plug-in hybrid or a power source for an electric vehicle.
An L * a * b color system color coordinate which is a color space defined by JIS Z 8729 is 0 <a <10, −1.2 <b <20.0, and 0 <L <30. And a composition formula of Li _w Ni _x Mn _y Co _z O _{2 + δ} is a positive electrode active material for a non-aqueous electrolyte secondary battery. In that case, 1.1 <w <1.5, 0.1 <x <0.4, 0.4 <y <0.9, 0 <z <0.2, w + x + y + z = 2, −0.2 <. δ <0.2.
[Selection figure] None

Description

  The present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery having a further improved discharge capacity.

  Lithium ion secondary batteries are widely used as power sources for small portable device terminals and mobile communication devices because of their high energy density and high voltage. In recent years, it has been used as a motor drive or auxiliary power source for hybrid electric vehicles (HEV), electric vehicles (EV), fuel cell vehicles, etc., and further high capacity, high output and high cycle durability are required.

As a positive electrode active material for a lithium ion secondary battery, lithium nickel manganese cobalt oxide has been developed for the purpose of high rate charge / discharge performance and charge / discharge cycle performance. In Patent Document 1, by using a lithium nickel manganese cobalt oxide having a composition formula of Li _{(1 + a)} [Mn _x Ni _y Co _z M _b ] O ₂ as a positive electrode active material for a lithium ion secondary battery, It is disclosed that the positive electrode active material having high safety can be obtained. In the above formula, M is an element other than Mn, Ni, Co and Li, and 0 ≦ a ≦ 0.1, −0.1 ≦ x−y ≦ 0.1, y ≦ x + z + b, 0 <Z ≦ 0.4, 0.3 ≦ x, 0.3 ≦ y, and x + y + z + b = 1. Further, Patent Document 1 discloses that the hue of lithium nickel manganese cobalt oxide is preferably lower in chromaticity in the red direction than JIS standard color chart Y05-30B.
JP 2003-3219 A

  However, the positive electrode active material disclosed in the above patent document has a problem in that charge / discharge capacity is insufficient when used for a plug-in hybrid or an electric vehicle power source.

  Therefore, an object of the present invention is to provide a positive electrode active material that can be used for a non-aqueous electrolyte secondary battery that requires a very high discharge capacity, such as a plug-in hybrid or a power source for an electric vehicle.

In order to achieve the above object, the present invention provides a positive electrode for a non-aqueous electrolyte secondary battery in which L * a * b color coordinate system color coordinates and composition formulas are color spaces defined by JIS Z 8729. It is an active material. Specifically, the L * a * b color system color coordinates are 0 <a <10, −1.2 <b <20.0, and 0 <L <30. Further, the composition formula is represented by Li _w Ni _x Mn _y Co _z O _{2 + δ} , and in this case, the parameters are 1.1 <w <1.5, 0.1 <x <0.4, 0. 4 <y <0.9, 0 <z <0.2, w + x + y + z = 2, and −0.2 <δ <0.2.

  ADVANTAGE OF THE INVENTION According to this invention, the positive electrode active material for nonaqueous electrolyte secondary batteries can be obtained by simple operation compared with the past. In addition, the non-aqueous electrolyte secondary battery using the positive electrode active material exhibits a higher discharge capacity and can be used for a plug-in hybrid or an electric vehicle power supply that requires an extremely high discharge capacity. Useful for.

<First Embodiment>
The first embodiment of the present invention relates to a positive electrode active material for a non-aqueous electrolyte secondary battery. The positive electrode active material has an L * a * b color system color coordinate, which is a color space defined by JIS Z 8729, with 0 <a <10, −1.2 <b <20.0, and 0 <L. <30, and the composition formula is represented by Li _w Ni _x Mn _y Co _z O _{2 + δ} . Each parameter in the composition formula is 1.1 <w <1.5, 0.1 <x <0.4, 0.4 <y <0.9, 0 <z <0.2, w + x + y + z = 2, And -0.2 <δ <0.2. Such a composition formula is sometimes referred to as a Li-excess layered oxide in the field to which the present invention belongs. Hereinafter, Li _w Ni _x Mn _y Co _z O _{2 + δ} in the present invention is also simply referred to as “Li-based composite oxide”.

The positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention includes the above two elements, that is, the L * a * b color system color coordinates and the composition ratio (molar ratio) in a specific range in the Li composite oxide. ) Inseparably. When the two elements are inseparably integral, and the average valence of manganese (Mn) among the transition metal elements constituting the Li-based composite oxide is within the desired range, a specific color coordinate is Take. The specific color coordinates are color coordinates (electrodes) that take values in the blue direction, the green direction, and higher brightness as compared with the conventional positive electrode active material for a non-aqueous electrolyte secondary battery (black appearance). Before use; brown appearance). Thus, the present inventors have found that the performance (charge / discharge capacity) of the active material can be remarkably improved. Note that the Li-based composite oxide in the present invention when viewed at the nano _level, a complex with Li 2 MnO ₃ and _{Li p [Ni q Mn r Co} s] O 2, Mn is trivalent and tetravalent It can be in a mixed state. For p, q, r, and s, 0.9 <p <1.1, 0 ≦ q ≦ 0.3, 0 ≦ r ≦ 0.3, and 0 ≦ s ≦ 0.2.

More specifically, out of the lithium (Li) metal element added in excess with respect to the sum of the molar ratios of the respective transition metal elements charged to produce the Li-based composite oxide, the Li metal site fits in the Li metal site. Excessive excess enters the transition metal element site in the crystal structure without excess or deficiency. In addition, since the influence of Li ₂ MnO ₃ increases as the average valence of Mn approaches from tetravalent to trivalent, a positive electrode active material for a nonaqueous electrolyte secondary battery exhibiting a higher discharge capacity is obtained. It is done.

  Among the elements described above, the a value, the b value, and the L value in the L * a * b color system color coordinates are 0 <a <10, −1.2 <b <20.0, and 0 <, respectively. L <30 is preferred. More preferably, 1.6 <a <8, −1.2 <b <10.0, and 10 <L <25, respectively, and more preferably 3 <a <6 and 2.0 <b <respectively. 5.0 and 15 <L <23. When it is within the above range, as described above, the color coordinates (to the electrode) such that the valence of manganese (Mn) is within the desired range, and the blue direction and the green direction, and the brightness is higher. Before use).

  The synthesis method for obtaining the positive electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is not particularly limited, but known methods such as a solid phase method, wet mixing, spray drying, coprecipitation method, etc. Can be selected.

  Moreover, as a metal element used for the positive electrode active material which concerns on this invention, other elements other than the above-mentioned 4 types of metal elements (Li, Ni, Mn, and Co) may be contained. The other elements are not particularly limited. For example, B, F, Na, Mg, Al, Si, P, S, Ca, Sc, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Se, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, In, Sn, Sb, Cs, Ba, Hf, Ta, W, Re, Os, Ir, Tl, Pb, Bi, Rf, etc. are mentioned. The other elements may be used alone or in combination of two or more. The molar ratio of the sum of Ni, Mn, and Co to the other elements among the above four types of essential metal elements is preferably 80 to 99.9: 0.1 to 20. 95-99.0: 1-5 is more preferable.

  The composition ratio of the charging of the four types of metal elements (raw materials) constituting the Li-based composite oxide is Li: Ni: Mn: Co = 1.1 to 1.5: 0.1 to 0.00 in terms of molar ratio. 4: It is preferable that it is 0.4-0.9: 0.0-0.2. That is, the composition ratio in this specification means a molar ratio. In the present specification, for example, “1.1 to 1.5” shown above means that it exceeds 1.1 and is less than 1.5. In the above range, the molar ratio (valence) of the composite oxide which is one of the two elements described above is desired, and a positive electrode active material for a non-aqueous electrolyte secondary battery exhibiting a significantly high discharge capacity is obtained. can get. More preferably, among the metal elements (raw materials), the molar ratio of Li is divided by the sum of the molar ratios of Ni, Mn, Co, and (if the other elements are included) the other elements. The value obtained is greater than 1.1 and less than 1.5.

  Further, the molar ratio of the four essential metal elements constituting the Li-based composite oxide to oxygen is such that the molar ratio between the metal elements is in the above-described range and w + x + y + z = 2. Furthermore, it is preferable that −0.2 <δ <0.2. In the composite oxide, oxygen deficiency inevitably occurs. However, when δ is within the above range, the performance (charge / discharge capacity) of the obtained positive electrode active material is hardly lowered even if oxygen deficiency occurs. The Li-based composite oxide as the positive electrode active material in the present invention may be a single type or a mixture of two or more types from the viewpoint of composition.

  As described above, the composition of the Li-based composite oxide is one of the two elements that are inseparable in the present invention, and the average valence of Mn is very important. By setting this value within the above-described preferred range, a positive electrode active material having a particularly high charge / discharge capacity can be obtained.

  The nonaqueous electrolyte secondary battery using the positive electrode active material according to the present invention can solve the problems of the above-described conventional technology, for example, the invention described in Patent Document 1. Furthermore, the invention described in Patent Document 1 has further problems other than those described above. Such a problem is that in the positive electrode active material disclosed in the above patent document, when a lithium ion secondary battery is operated in a high temperature environment of 50 ° C. or higher, a transition metal is introduced into the electrolyte from the positive electrode surface of the secondary battery. The element component is eluted, and the charge / discharge capacity can be reduced. In particular, a reduction in discharge capacity, which is energy that can actually be used in a plug-in hybrid or an electric vehicle power supply, can be an essential problem in practice. On the other hand, in the nonaqueous electrolyte secondary battery using the positive electrode active material according to the present invention, as described above, the composition of the Li-based composite oxide and the hue thereof (the values of the above color coordinates) are in the preferred range described above. Due to being within, elution of the transition metal element component can be effectively suppressed.

  Moreover, it is preferable that the positive electrode active material for nonaqueous electrolyte secondary batteries of this invention is baked at 700 degreeC or more and less than 1000 degreeC. More preferably, they are 750 degreeC or more and 950 degrees C or less. When the firing temperature is 700 ° C. or higher, the reaction for obtaining the positive electrode active material surely proceeds and the reaction time can be kept to a practically practical level, which is preferable. Moreover, when a calcination temperature is less than 1000 degreeC, the rapid progress of reaction can be suppressed and the valence control of a transition metal element can be implement | achieved easily. Furthermore, depending on the firing temperature, a metal element (which may also include other elements) that is a raw material that has been charged may be partially volatilized in the process of becoming a Li-based composite oxide (for example, Li). However, when the firing temperature is lower than 1000 ° C., the change in the molar ratio due to the partial volatilization of the metal element is less likely to occur. Therefore, the positive electrode for a non-aqueous electrolyte secondary battery having a desired molar ratio An active material can be obtained easily. And, it is very preferable that such a change (deviation) in the molar ratio hardly occurs because a positive electrode active material having a constant quality can be obtained stably at all times. Furthermore, in the above-described range, it is possible to reliably obtain the above-described blue direction and green direction, and color coordinates (before use for an electrode; brown appearance) that take higher numerical values. It is. In this sense, the non-aqueous electrolyte secondary battery using the positive electrode active material according to the present invention has a composition of complex oxide (Li-based complex oxide) and a color tone (color coordinate value) within the above-described preferable range. In addition, it is preferable that the firing temperature is within the above-described range. That is, paying attention to the interrelationship between the three elements of the composition, hue (color coordinate value in the present invention), and the firing temperature, and designing each to take a value within the above-described range, An extremely high positive electrode active material can be obtained.

<Second Embodiment>
2nd Embodiment of this invention is a positive electrode for nonaqueous electrolyte secondary batteries containing the positive electrode active material for nonaqueous electrolyte secondary batteries obtained by the said 1st Embodiment. Although it does not specifically limit as said nonaqueous electrolyte secondary battery, For example, the lithium ion secondary battery etc. which are shown below are mentioned. Hereinafter, the electrode for a lithium ion secondary battery including both the positive electrode and the negative electrode will be described.

  The electrode for a nonaqueous electrolyte secondary battery is formed on a positive electrode current collector and a positive electrode including a positive electrode mixture formed on the positive electrode current collector, a negative electrode current collector, and the negative electrode current collector. And a negative electrode including a negative electrode mixture. In addition, the said positive electrode mixture contains a positive electrode active material, a conductive support agent, and a binder, and the said negative electrode mixture contains a negative electrode active material, a conductive support agent, and a binder. Among these, the feature of the present invention resides in the positive electrode active material described in detail in the first embodiment and a positive electrode using the positive electrode active material. Hereinafter, the term “mixture” means both a positive electrode mixture and a negative electrode mixture.

  Hereinafter, preferred embodiments relating to the above-described electrodes will be described in detail with reference to the drawings as appropriate. Each drawing is exaggerated for convenience of explanation, and the dimensional ratio of each component in each drawing may be different from the actual one.

[Positive electrode current collector and negative electrode current collector]
As the positive electrode current collector and the negative electrode current collector, members conventionally used as a current collector material for batteries can be appropriately employed. For example, examples of the positive electrode current collector and the negative electrode current collector include aluminum (Al), nickel (Ni), iron (Fe), stainless steel (SUS), titanium (Ti), and copper (Cu). Among these, Al is preferably used as the positive electrode current collector and Cu is preferably used as the negative electrode current collector in that it is easily processed into a thin film and is inexpensive. Furthermore, when these preferable current collectors are used, an electrode excellent in terms of electron conductivity and battery operating potential can be obtained.

  The general thickness of the current collector is 10 μm or more and 20 μm or less. However, a current collector having a thickness outside this range may be used. The size of the current collector is determined according to the intended use of the battery. If a large electrode used for a large battery is manufactured, a current collector having a large area is used. On the other hand, if a small electrode is produced, a current collector with a small area is used.

  In the third embodiment described later, a stacked lithium ion secondary battery that is not a bipolar type is described in detail. However, the positive electrode active material and the negative electrode active material in the present invention may be used for a bipolar lithium ion secondary battery. In that case, as the current collector, the positive electrode current collector and the negative electrode current collector may be bonded together, and the positive electrode active material layer and the negative electrode active material layer in the present invention may be formed on both surfaces of the current collector. Alternatively, the positive electrode active material layer and the negative electrode active material layer in the present invention can be obtained by using SUS, Ti, or the like that can be used for the positive electrode current collector and the negative electrode current collector as the positive electrode current collector and the negative electrode current collector. It may be formed.

[Positive electrode active material]
As the positive electrode active material in the positive electrode mixture, those described in detail in the first embodiment can be suitably used.

[Negative electrode active material]
The negative electrode active material in the negative electrode mixture is not particularly limited, and examples thereof include lithium metal, lithium alloy, lithium transition metal-composite oxide, carbon, and materials that can be doped or dedoped with lithium. . The carbon is not particularly limited, and examples thereof include graphite-based carbon materials such as natural graphite, artificial graphite, and expanded graphite, carbon black, activated carbon, carbon fiber, coke, soft carbon, and hard carbon. Examples of natural graphite include scaly graphite. Examples of the artificial graphite include MCMB (mesocarbon microbeads), MCF (mesophase carbon fiber), and the like. Of these, MCMB is preferable. MCMB is obtained when coal tar or petroleum heavy oil is melted at around 400 ° C. to form small spheres, which are obtained by heat treatment in an inert atmosphere. At this time, since the carbon hexagonal network structure of the graphite structure has a laminar orientation laminated in one direction, it is easy to take in lithium ions and can be suitably used as a negative electrode material. The mesophase in the MCF is a liquid crystal substance obtained by heat-treating heavy oil. By controlling the process of spinning and heat-treating this, carbon fibers with controlled graphite crystal arrangement can be obtained. The negative electrode active material may be a single type or a combination of two or more types of materials.

  The average particle diameter of the active material (positive electrode active material and negative electrode active material) is not particularly limited. However, if this average particle size is too large, the reaction surface area of the active material will be reduced, or lithium ion conduction inside the active material particles will limit the lithium ion conduction in the active material layer. There is a possibility that the effects of the invention cannot be sufficiently obtained. From such a viewpoint, the average particle diameter of the active material is preferably 0.1 μm or more and 20 μm or less. However, those outside these ranges can also be used. In addition, the value measured by the laser diffraction scattering type particle size distribution measuring method shall be employ | adopted for the average particle diameter in this specification.

[Conductive aid]
Although it does not specifically limit as a conductive support agent in the said mixture, A carbonaceous material is mentioned. The carbonaceous material is not particularly limited, and examples thereof include natural graphite, artificial graphite, cokes, and carbon black. The conductive auxiliary agent may be composed of one kind alone, or may be a mixture of two or more kinds, for example, artificial graphite and carbon black. When the electrode contains a conductive additive, an electronic network inside the electrode is effectively formed, which can contribute to improving the output characteristics of the battery.

[Binder]
Although it does not specifically limit as a binder of the said mixture, A thermoplastic resin is mentioned. The plastic resin is not particularly limited, but may be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride copolymer, hexafluoride. Examples thereof include propylene fluoride / vinylidene fluoride copolymer, tetrafluoroethylene / perfluorovinyl ether copolymer, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), acrylonitrile, polyimide, and a synthetic rubber binder. These may be used alone or in combination of two or more. In addition, what was melt | dissolved in the organic solvent in which binders are soluble, such as N-methyl-2-pyrrolidone (NMP), can also be used for these binders.

  Moreover, the ratio of the said fluororesin in the said mixture will be 1 mass% or more and 10 mass% or less, and the ratio of the said polyolefin resin will be 0.1 mass% or more and 2 mass% or less. A binder prepared by adjusting to is preferable. In such a case, it is preferable because the binding property between the current collector and the active material in the mixture is excellent, and the safety of the lithium secondary battery against external heating as represented by the heating test can be further improved.

  Here, the method for supporting the mixture on the current collector is not particularly limited since a conventionally known method can be used. For example, a method of pressure molding or a method of pasting using a solvent or the like, and applying and drying on a current collector followed by pressing or the like can be mentioned.

<Third Embodiment>
3rd Embodiment of this invention is a nonaqueous electrolyte secondary battery which has an electrode for nonaqueous electrolyte secondary batteries obtained by the said 2nd Embodiment.

  The positive electrode active material and the negative electrode active material obtained by the present invention are formed on the surfaces of the positive electrode current collector and the negative electrode current collector, respectively, and are not a bipolar type laminated (internal parallel connection type) non-aqueous electrolyte secondary battery. Can be used. Hereinafter, a laminated lithium ion secondary battery that is not a bipolar type will be outlined with reference to the drawings, but is not limited thereto.

  FIG. 1 schematically shows the overall structure of a laminated lithium ion secondary battery (hereinafter also simply referred to as a lithium ion battery) which is a typical embodiment of the lithium ion battery of the present invention. FIG. The number of laminated layers is not particularly limited, but is preferably 5 or more and 30 or less, more preferably 10 or more and 25 or less.

  As shown in FIG. 1, in the lithium ion battery 10 of this embodiment, a substantially rectangular power generation element (battery element) 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate sheet 29 that is an exterior. It has a structure. Specifically, the power generation element 21 is housed and sealed by using a polymer-metal composite laminate sheet as the battery exterior and joining all of its peripheral parts by thermal fusion.

  The power generation element 21 includes a positive electrode in which the positive electrode active material layer 13 is disposed on both surfaces of the positive electrode current collector 11, an electrolyte layer 17, and a negative electrode in which the negative electrode active material layer 15 is disposed on both surfaces of the negative electrode current collector 12. It has a stacked configuration. Specifically, the positive electrode, the electrolyte layer, and the negative electrode are laminated in this order so that one positive electrode active material layer 13 and the negative electrode active material layer 15 adjacent thereto face each other with the electrolyte layer 17 therebetween. .

  Thereby, the adjacent positive electrode, electrolyte layer, and negative electrode constitute one unit cell layer 19. Therefore, it can be said that the lithium ion battery 10 of the present embodiment has a configuration in which a plurality of single battery layers 19 are stacked and electrically connected in parallel. Further, on the outer periphery of the unit cell layer 19, a seal portion (insulating layer) for insulating between the adjacent positive electrode current collector 11 and negative electrode current collector 12 (not shown; reference numeral 31 in FIG. 4 described later) May be provided. Although the positive electrode active material layer 13 is disposed on only one side of the outermost layer positive electrode current collector located on both outermost layers of the power generation element 21, active material layers may be provided on both sides. 2, the arrangement of the positive electrode and the negative electrode is reversed so that the outermost layer negative electrode current collector is positioned in both outermost layers of the power generation element 21, and the negative electrode is formed only on one side of the outermost layer negative electrode current collector. An active material layer may be arranged.

  The positive electrode current collector 11 and the negative electrode current collector 12 are attached to a positive electrode current collector plate 25 and a negative electrode current collector plate 27 that are electrically connected to the respective electrodes (positive electrode and negative electrode), and are sandwiched between end portions of the laminate sheet 29. Thus, it has a structure led out of the laminate sheet 29. The positive electrode current collector plate 25 and the negative electrode current collector plate 27 are ultrasonically welded to the positive electrode current collector 11 and the negative electrode current collector 12 of each electrode, respectively, via a positive electrode lead and a negative electrode lead (not shown) as necessary. Or resistance welding or the like.

[Active material layer]
The active material layer includes an active material, a conductive additive, and a binder, and may further include other additives as necessary.

  The positive electrode active material layer 12 includes a positive electrode active material according to the present invention. Here, since the specific description of the positive electrode active material was performed in the first embodiment, the description thereof is omitted here. The thickness of the positive electrode active material layer 12 in the thickness direction is preferably 10 μm or more and 500 μm or less, and more preferably 20 μm or more and 250 μm or less.

  Since the specific description of the negative electrode active material contained in the negative electrode active material layer 15 has been made above, it is omitted here. The thickness of the negative electrode active material layer 15 in the thickness direction is preferably 10 μm or more and 500 μm or less, and more preferably 20 μm or more and 250 μm or less.

  In addition to the active material, the active material layer includes a conductive additive and a binder. Furthermore, the other additive that can be contained in the active material layer is not particularly limited, and examples thereof include an electrolyte salt (lithium salt) and an ion conductive polymer. Since the conductive auxiliary agent and the binder have been described in detail above, description thereof is omitted here.

Examples of the electrolyte salt (lithium salt) include Li (C ₂ F ₅ SO ₂ ) ₂ N, LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO _{3 and the} like.

  The ion conductive polymer is not particularly limited, and examples thereof include polyethylene oxide (PEO) -based and polypropylene oxide (PPO) -based polymers.

  The compounding ratio of these components contained in the positive electrode active material layer 12 and the negative electrode active material layer 15 is not particularly limited. The blending ratio can be adjusted by appropriately referring to known knowledge about lithium ion secondary batteries.

[Electrolyte layer]
The electrolyte layer may be liquid, gel, or solid. By using a solid electrolyte (which will be described later in detail, including a polymer gel electrolyte, a solid polymer electrolyte, and an inorganic solid electrolyte) as the electrolyte layer, it is possible to prevent leakage.

  By using a gel polymer electrolyte layer (polymer gel electrolyte) as the electrolyte layer, the fluidity of the electrolyte is lost, it is possible to suppress the outflow of the electrolyte to the current collector, and to block the ionic conductivity between the layers. . Examples of the gel electrolyte host polymer include PEO, PPO, PVdF, polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), PAN, PMA, and PMMA. Moreover, as a plasticizer, it is possible to use the electrolyte solution normally used for a lithium ion battery.

  The gel polymer electrolyte (polymer gel electrolyte) is produced by including an electrolyte solution usually used in a lithium ion battery in an all solid polymer electrolyte such as PEO or PPO. The gel polymer electrolyte (polymer gel electrolyte) includes a polymer skeleton having no lithium ion conductivity, such as PVdF, PAN, and PMMA. The ratio of the polymer constituting the gel polymer electrolyte (polymer gel electrolyte) and the electrolytic solution is not particularly limited. When 100% of the polymer is an all solid polymer electrolyte and 100% of the electrolyte is a liquid electrolyte, all of the intermediates are included in the concept of gel polymer electrolyte (polymer gel electrolyte). In addition, an inorganic solid electrolyte having ion conductivity such as an inorganic solid such as ceramic is also included in the all solid electrolyte. Therefore, as described above, the solid electrolyte in the present invention includes all of polymer gel electrolyte, solid polymer electrolyte, and inorganic solid electrolyte.

  Specifically, as the electrolyte layer, conventionally known materials include (a) polymer gel electrolyte (gel polymer electrolyte), (b) all solid polymer electrolyte (polymer solid electrolyte, inorganic solid electrolyte), ( c) A liquid electrolyte (electrolytic solution) can be used. In addition, (d) separators (including non-woven fabric separators) impregnated with the electrolytes listed in (a) to (c) can be used as the electrolyte layer.

(A) Gel polymer electrolyte (polymer gel electrolyte)
The gel polymer electrolyte (polymer gel electrolyte) refers to an electrolyte solution held in a polymer matrix. By using a gel polymer electrolyte as the electrolyte, the fluidity of the electrolyte is lost, and it is easy to suppress the outflow of the electrolyte to the current collector layer such as a conductive polymer film and to block the ionic conductivity between the layers. Is excellent.

Examples of the polymer matrix (polymer) or the gel electrolyte host polymer used as the polymer gel electrolyte include polymers having polyethylene oxide in the main chain or side chain (PEO), polymers having polypropylene oxide in the main chain or side chain ( PPO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polymethacrylic acid ester, polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), poly (methyl methacrylate) ( PMMA) and copolymers thereof are preferred. Among these, it is more preferable to use PEO, PPO and a copolymer thereof, or PVdF-HFP. Moreover, as a plasticizer, it is possible to use the electrolyte solution normally used for a lithium ion battery. And such electrolyte, which electrolyte salt dissolved in a solvent, as the _{electrolyte, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 inorganic acid anions such as One or more selected from organic acid anion salts such as ionic salt, LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, and Li (C ₂ F ₅ SO ₂ ) ₂ N are preferable. Moreover, as a solvent, 1 or more types selected from ethylene carbonate (EC), propylene carbonate (PC), (gamma) -butyrolactone (GBL), dimethyl carbonate (DMC), and diethyl carbonate (DEC) are preferable.

  The ratio of the electrolytic solution in the gel electrolyte in the present invention is not particularly limited, but is preferably about several mass% or more and 98 mass% or less from the viewpoint of ion conductivity and the like. In particular, a gel electrolyte with a large amount of electrolytic solution in which the proportion of the electrolytic solution is 70% by mass or more (and 98% by mass or less) is more preferable because the desired effect of the present application can be obtained.

(B) All solid electrolyte (all solid polymer electrolyte, polymer solid electrolyte, inorganic solid electrolyte)
By using an all-solid electrolyte (intrinsic polymer electrolyte) as the electrolyte, it is superior in that the fluidity of the electrolyte is lost and the electrolyte does not flow out to the current collector layer, and the ion conductivity between each layer can be blocked. ing. That is, the intrinsic polymer electrolyte has a structure in which a supporting salt (lithium salt) is dissolved in a matrix polymer that is a solid polymer electrolyte having ion conductivity, and does not include an organic solvent that is a plasticizer. Therefore, when the electrolyte layer is composed of an intrinsic polymer electrolyte, there is no fear of liquid leakage from the battery, and the battery reliability can be improved.

Examples of the all solid polymer electrolyte include known solid polymer electrolytes such as PEO, PPO, and copolymers thereof, and inorganic solid electrolytes having ion conductivity such as ceramics. The solid polymer electrolyte contains a lithium salt in order to ensure ionic conductivity. As the lithium salt, LiBF ₄ , LiPF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , or a mixture thereof can be used.

(C) Liquid electrolyte (electrolyte)
Examples of the liquid electrolyte include those obtained by dissolving an electrolyte salt in an organic solvent (plasticizer). The liquid electrolyte is not particularly limited, and various conventionally known liquid electrolytes can be appropriately used. The electrolyte salt may include one or more selected from inorganic acid anion salts and organic acid anion salts. The inorganic acid anion _{salts, LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiTaF 6, LiAlCl 4, Li 2 B 10 Cl 10 and the like. On the other hand, examples of the organic acid anion salt include LiCF ₃ SO ₃ , Li (CF ₃ SO ₂ ) ₂ N, Li (C ₂ F ₅ SO ₂ ) ₂ N, and the like.

  Examples of the solvent include cyclic carbonates such as propylene carbonate (PC) and ethylene carbonate (EC); chain carbonates such as dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), and diethyl carbonate (DEC); tetrahydrofuran, 2 -Ethers such as methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-dibutoxyethane; Lactones such as γ-butyrolactone (GBL); Nitriles such as acetonitrile; Methyl propionate, etc. Esters such as dimethylformamide; methyl acetate and methyl formate. And what uses plasticizers (organic solvent), such as an aprotic solvent, formed by mixing these components individually by 1 type or 2 types or more can be used.

(D) Separator impregnated with the electrolyte (including non-woven separator)
As the electrolyte that can be impregnated in the separator, the same electrolytes as those already described (a) to (c) can be used.

  Examples of the separator include a porous sheet and a nonwoven fabric made of a polymer that absorbs and holds the electrolyte.

  As the porous sheet, for example, a microporous separator can be used. Examples of the polymer include fluororesins; polyolefins such as polyethylene (PE) and polypropylene (PP); laminates having a three-layer structure of PP / PE / PP, polyimide, nylon, and (aromatic) aramid. And as a specific form of a separator, forms, such as a microporous film which consists of an above-mentioned material, a nonwoven fabric, and a woven fabric, are mentioned. Further, the thickness of the separator is preferably as thin as possible as long as the mechanical and chemical strength is maintained from the viewpoint that the volume energy density of the battery is increased and the internal resistance is reduced. In terms of numerical values, it is preferably 5 μm or more and 200 μm or less. In applications such as secondary batteries for driving motors such as electric vehicles (EV), hybrid electric vehicles (HEV), and fuel cell vehicles (FCV), the thickness is preferably 4 μm or more and 60 μm or less in a single layer or multiple layers. The separator preferably has a fine pore size of 1 μm or less (usually a pore size of about several tens of nanometers) and a porosity of 20% or more and 80% or less.

  As the nonwoven fabric, cotton, rayon, acetate, nylon, polyester; polyolefins such as PP and PE; conventionally known materials such as polyimide and aramid can be used alone or in combination. The bulk density of the nonwoven fabric is not particularly limited as long as sufficient battery characteristics can be obtained by the impregnated polymer gel electrolyte. The porosity of the nonwoven fabric separator is preferably 50% or more and 90% or less. Furthermore, the thickness of the nonwoven fabric separator may be the same as that of the electrolyte layer, and is preferably 5 μm or more and 200 μm or less, more preferably 10 μm or more and 100 μm or less. When the thickness is 5 μm or more, the electrolyte retention can be improved. Further, when the thickness is 200 μm or less, an increase in resistance can be prevented.

  In addition, the shape of the non-aqueous electrolyte secondary battery of the present invention is not particularly limited, and may be any of a stacked battery or a bipolar battery that is not a bipolar battery. Among these, a bipolar nonaqueous electrolyte secondary battery is preferable from the viewpoint of realizing both high energy density and high output density. Further, the shape of the secondary battery viewed from another viewpoint is not particularly limited, but may be a paper type, a coin type, a cylindrical type, a square type, an aluminum laminate type, or the like.

[Seal part]
The seal (also referred to as the peripheral insulating layer) is used to prevent the adjacent current collectors in the battery from contacting each other and short-circuiting due to slight unevenness at the end of the laminated electrode. It arrange | positions in the peripheral part of the cell layer (it is not shown in FIG. 1). As the seal portion, for example, polyolefin resin such as PE and PP, epoxy resin, rubber, polyimide and the like can be used, and polyolefin resin is preferable from the viewpoint of corrosion resistance, chemical resistance, film forming property, economy and the like. However, it is not limited to these.

[Tab (positive tab and negative tab)]
For the purpose of extracting current outside the battery, a tab (a positive tab (not shown, the same below) and a negative tab (not shown, the same below)) electrically connected to each current collector are external to the battery exterior material. Has been taken out. Specifically, as shown in FIG. 1, a positive electrode tab electrically connected to each positive electrode current collector 11 and a negative electrode tab electrically connected to each negative electrode current collector 12 include battery exterior materials ( It is taken out of the laminate sheet 29 (not shown).

  The material which comprises a tab (a positive electrode tab and a negative electrode tab) in particular is not restrict | limited, The well-known highly electroconductive material conventionally used as a tab for lithium ion batteries can be used. As a constituent material of the tab, for example, metal materials such as aluminum, copper, titanium, nickel, stainless steel (SUS), and alloys thereof are preferable, and aluminum, copper, and the like are more preferable from the viewpoint of light weight, corrosion resistance, and high conductivity. Is preferred. In the relationship between the positive electrode tab and the negative electrode tab, the same material may be used, or different materials may be used. Moreover, it is good also as a positive electrode tab and a negative electrode tab by extending each collector 11 and 12, and the positive electrode tab and negative electrode tab which were prepared separately may be connected to each collector 11 and 12. FIG.

[Positive and negative terminal leads]
A positive terminal lead (not shown, the same below) and a negative terminal lead (not shown, the same below) are also used as necessary. For example, when the positive electrode tab and the negative electrode tab that are output electrode terminals are directly taken out from the current collectors 11 and 12, the positive electrode terminal lead and the negative electrode terminal lead may not be used.

  As a material for the positive electrode terminal lead and the negative electrode terminal lead, a terminal lead used in a known lithium ion secondary battery can be used. It should be noted that the part taken out from the battery exterior material (not shown) does not affect products (for example, automobile parts, particularly electronic devices) by contacting with peripheral devices or wiring and causing electric leakage. It is preferable to coat with a heat-shrinkable heat-shrinkable tube.

[Battery exterior materials]
As the battery exterior member 22, a conventionally known metal can case can be used, and a bag-like case that can cover a power generation element (battery element) using a laminate film containing aluminum can be used. For example, a laminate film having a three-layer structure in which PP, aluminum, and nylon are laminated in this order can be used as the laminate film, but the laminate film is not limited thereto.

[External structure of lithium-ion battery]
FIG. 2 is a perspective view showing the appearance of a stacked flat non-bipolar or bipolar lithium ion secondary battery which is a typical embodiment of the lithium ion battery according to the present invention.

  As shown in FIG. 2, the laminated flat lithium ion battery 50 has a rectangular flat shape, and a positive electrode tab 58 and a negative electrode tab 59 for taking out electric power are drawn out from both sides thereof. ing. The power generation element (battery element) 57 is encased in the battery exterior material 52 of the lithium ion secondary battery 50. The surroundings are heat-sealed, and the power generation element (battery element) 57 is sealed with the positive electrode tab 58 and the negative electrode tab 59 pulled out to the outside. Here, the power generation element (battery element) 57 corresponds to the power generation element (battery element) 21 of the stacked lithium ion battery 50 which is not the bipolar type shown in FIG. That is, the power generation element (battery element) 21 includes a single battery layer (= battery unit or single cell) 19 including a positive electrode (positive electrode active material layer) 13, an electrolyte layer 17, and a negative electrode (negative electrode active material layer) 15. Are stacked.

  The lithium ion battery of the present invention is not limited to a laminated flat shape as shown in FIG. For example, a wound lithium ion battery may have a cylindrical shape. Further, such a cylindrical shape may be deformed to form a rectangular flat shape. In the said cylindrical shape thing, a laminate film may be used for the exterior material, and a conventionally well-known cylindrical can (metal can) may be used, and it does not restrict | limit in particular.

  Further, the tabs 58 and 59 shown in FIG. 2 are not particularly limited, and the positive electrode tab 58 and the negative electrode tab 59 may be pulled out from the same side. On the other hand, the positive electrode tab 58 and the negative electrode tab 59 may be divided into a plurality of parts and taken out from each side, and are not limited to those shown in FIG. Further, in a wound type lithium ion battery, instead of a tab, for example, a terminal may be formed using a cylindrical can (metal can).

  Further, as described above, the electrode for a lithium ion secondary battery obtained by the present invention can also be used for a bipolar nonaqueous electrolyte secondary battery (hereinafter also referred to as “bipolar battery”).

  FIG. 3 schematically shows the overall structure of a bipolar stacked lithium ion secondary battery (hereinafter also simply referred to as a bipolar lithium ion battery), which is another typical embodiment of the lithium ion battery of the present invention. FIG. However, the technical scope of the present invention is not limited to such a form.

  In the bipolar battery 10 ′ of the present embodiment shown in FIG. 3, a substantially rectangular power generation element (battery element; laminate) 21 in which a charge / discharge reaction actually proceeds is sealed inside a laminate film 29 which is a battery exterior material. It has a stopped structure.

  As shown in FIG. 3, the power generation element 21 of the bipolar battery 10 ′ of the present embodiment is formed with a positive electrode active material layer 13 electrically coupled to one surface of the current collector 11, and the current collector 11. And a plurality of bipolar electrodes having a negative electrode active material layer 15 electrically coupled to the opposite surface. Each bipolar electrode is stacked via the electrolyte layer 17 to form the power generation element 21. The electrolyte layer 17 has a configuration in which an electrolyte is held at the center in the surface direction of a separator as a base material. At this time, each bipolar type is formed such that the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode face each other through the electrolyte layer 17. Electrodes and electrolyte layers 17 are alternately stacked. That is, the electrolyte layer 17 is disposed between the positive electrode active material layer 13 of one bipolar electrode and the negative electrode active material layer 15 of another bipolar electrode adjacent to the one bipolar electrode.

  The adjacent positive electrode active material layer 13, electrolyte layer 17, and negative electrode active material layer 15 constitute one single battery layer (= battery unit or single cell) 19. Therefore, it can be said that the bipolar battery 10 ′ has a configuration in which the single battery layers 19 are stacked. Further, for the purpose of preventing liquid junction due to leakage of the electrolytic solution from the electrolyte layer 17, a seal portion 31 is disposed on the outer peripheral portion of the unit cell layer 19. By providing the seal portion 31, it is possible to insulate between the adjacent current collectors 11 and prevent a short circuit due to contact between adjacent electrodes. A positive electrode active material layer 13 is formed only on one side of the positive electrode outermost layer current collector 11 a located in the outermost layer of the power generation element 21. The negative electrode active material layer 15 is formed only on one surface of the outermost current collector 11b on the negative electrode side located in the outermost layer of the power generation element 21. However, the positive electrode active material layer 13 may be formed on both surfaces of the outermost layer current collector 11a on the positive electrode side. Similarly, the negative electrode active material layer 15 may be formed on both surfaces of the outermost layer current collector 11b on the negative electrode side.

  Further, in the bipolar battery 10 ′ shown in FIG. 3, the positive electrode current collector plate 25 is disposed so as to be adjacent to the positive electrode side outermost layer current collector 11a, and this is extended and led out from the laminate sheet 29 which is a battery exterior material. ing. On the other hand, a negative electrode current collector plate 27 is disposed so as to be adjacent to the outermost layer current collector 11b on the negative electrode side, and this is similarly extended and led out from a laminate sheet 29 which is an exterior of the battery.

  In the bipolar battery 10 ′ shown in FIG. 3, a seal portion 31 is usually provided around each single cell layer 19. The purpose of the seal portion 31 is to prevent the adjacent current collectors 11 in the battery from coming into contact with each other and a short circuit caused by a slight irregularity at the end of the unit cell layer 19 in the power generation element 21. Is provided. By installing such a seal portion 31, long-term reliability and safety can be ensured, and a high-quality bipolar battery 10 'can be provided.

  Note that the number of stacks of the unit cell layers 19 is adjusted according to a desired voltage. In the bipolar battery 10 ′, the number of times the single battery layer 19 is stacked may be reduced if a sufficient output can be secured even if the battery is made as thin as possible. Even in the bipolar battery 10 ′, in order to prevent external impact and environmental degradation during use, the power generation element 21 is sealed under reduced pressure in a laminate sheet 29 that is a battery exterior material, and the positive current collector plate 25 and the negative current collector. It is preferable that the plate 27 be taken out of the laminate sheet 29.

  The constituent elements and the manufacturing method of the lithium ion battery 10 and the bipolar battery 10 'are basically the same except that the electrical connection form (electrode structure) in both batteries is different. And it cannot be overemphasized that it can be comprised thru | or manufactured using the same structural requirements and manufacturing method suitably also regarding each structural requirements and manufacturing method of bipolar battery 10 '. Moreover, an assembled battery and a vehicle can also be comprised using the lithium ion battery 10 and / or bipolar battery 10 'of this invention.

[Method for producing non-aqueous electrolyte secondary battery]
Below, an example of the manufacturing method of the thing obtained by the above-mentioned 1st-3rd embodiment is explained. Although it does not specifically limit as a nonaqueous electrolyte secondary battery, For example, a lithium ion secondary battery etc. are mentioned. Hereinafter, a method for manufacturing a lithium ion secondary battery will be described.

(Active material slurry preparation process)
In this step, the positive electrode active material and the negative electrode active material, which are the characteristics of the present invention, and other components (for example, a binder, a conductive additive, an electrolyte, a polymerization initiator) as necessary are mixed in a solvent. Then, an active material slurry is prepared. The specific form of each component blended in the active material slurry is as described in the column of the configuration of the electrode of the present invention, and a detailed description thereof will be omitted here.

  When manufacturing the positive electrode active material for a nonaqueous electrolyte secondary battery according to the present invention, the plurality of steps may be firing steps. Note that the firing temperature described above indicates a so-called “main firing” condition, and the temporary firing is not limited to the above temperature range. Although not particularly limited, in the case of performing preliminary firing which is an optional step, as an example, the firing temperature is preferably 500 ° C. or higher and 700 ° C. or lower, and the firing time is preferably 1 hour or longer and 20 hours or shorter. Further, it is preferable that the main firing or the temporary firing is performed in an oxidizing atmosphere.

  The kind of solvent and the mixing means are not particularly limited, and conventionally known knowledge about electrode production can be appropriately referred to. Examples of the solvent include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, methylformamide and the like. When adopting polyvinylidene fluoride (PVdF) as a binder, NMP is preferably used as a solvent.

(Coating film formation process)
Subsequently, each current collector is prepared, and the active material slurry prepared above is applied to the surface of the current collector and dried. Thereby, the coating film consisting of the positive electrode active material slurry according to the present invention is formed on the surface of the current collector. This coating film becomes an active material layer through a pressing step described later.

  The specific form of the current collector to be prepared is as described in the column of the configuration of the electrode of the present invention, and thus detailed description thereof is omitted here.

  The application means for applying the active material slurry is not particularly limited, but generally used means such as a self-propelled coater may be employed.

  A coating film is formed according to the desired arrangement | positioning form of each collector and active material layer in the electrode manufactured. For example, when the manufactured electrode is a bipolar electrode, a coating film containing the positive electrode active material according to the present invention is formed on one surface of the current collector. In addition, the coating film containing the negative electrode active material which concerns on this invention is formed in the other surface. On the other hand, when manufacturing a non-bipolar electrode, a coating film containing either the positive electrode active material according to the present invention or the negative electrode active material according to the present invention is formed on both surfaces of one current collector. The

  Thereafter, the coating film formed on the surface of the current collector is dried. Thereby, the solvent in a coating film is removed.

  The drying means for drying the coating film is not particularly limited, and conventionally known knowledge about electrode production can be appropriately referred to. For example, heat treatment is exemplified. Drying conditions (drying time, drying temperature, etc.) can be appropriately set according to the application amount of the active material slurry and the volatilization rate of the solvent of the slurry according to the present invention.

  When a coating film contains a polymerization initiator, the ion conductive polymer in a coating film is bridge | crosslinked by a crosslinkable group by performing a superposition | polymerization process further.

  The polymerization treatment in the polymerization step is not particularly limited, and conventionally known knowledge may be referred to as appropriate. For example, when the coating film contains a thermal polymerization initiator (AIBN or the like), the coating film is subjected to heat treatment. Moreover, when a coating film contains a photoinitiator (BDK etc.), light, such as an ultraviolet light, is irradiated. In addition, the heat processing for thermal polymerization may be performed simultaneously with said drying process, and may be performed before or after the said drying process.

(Pressing process)
Then, the laminated body produced through the said coating-film formation process is pressed to the lamination direction. Thereby, the battery electrode according to the present invention is completed. At this time, the porosity of the active material layer can be controlled by adjusting the pressing conditions.

  Specific means and pressing conditions for the press treatment are not particularly limited, and can be appropriately adjusted so that the porosity of the active material layer after the press treatment becomes a desired value. Specific examples of the press process include a hot press machine and a calendar roll press machine. Also, the pressing conditions (temperature, pressure, etc.) are not particularly limited, and conventionally known knowledge can be referred to as appropriate.

<Fourth embodiment>
[Battery]
4th Embodiment of this invention is an assembled battery which has a nonaqueous electrolyte secondary battery obtained by the said 3rd Embodiment.

  The assembled battery of the present invention is constituted by connecting a plurality of lithium ion batteries of the present invention. Specifically, at least two or more are used, and are configured by serialization, parallelization, or both. Capacitance and voltage can be freely adjusted by paralleling in series. In the assembled battery of the present invention, a non-bipolar stacked lithium ion battery and bipolar lithium ion battery of the present invention are used, and a plurality of these are combined in series, in parallel, or in series and in parallel. An assembled battery can also be configured.

  4 (4A to 4C) is an external view of a typical embodiment of the assembled battery according to the present invention. 4A is a plan view of the assembled battery, FIG. 4B is a front view of the assembled battery, and FIG. 4C is a side view of the assembled battery.

  As shown in FIGS. 4A to 4C, the assembled battery 300 according to the present invention forms a small assembled battery 250 that can be attached and detached by connecting a plurality of lithium ion batteries of the present invention in series or in parallel. . A plurality of the detachable small assembled batteries 250 are further connected in series or in parallel. Thereby, the assembled battery 300 having a large capacity and a large output suitable for a power source for driving a vehicle and an auxiliary power source that require a high volume energy density and a high volume output density can be formed. 4A is a plan view of the assembled battery, FIG. 4A is a front view, and FIG. 4C is a side view. The small assembled battery 250 that can be attached and detached is connected to each other using an electrical connection means such as a bus bar, and the assembled battery 250 is stacked in a plurality of stages using a connection jig 310. How many non-bipolar stacked or bipolar lithium ion batteries are connected to form the assembled battery 250, and how many assembled batteries 250 are stacked to form the assembled battery 300 are mounted. What is necessary is just to determine according to the battery capacity and output of the vehicle (electric vehicle) to be.

<Fifth Embodiment>
[vehicle]
The fifth embodiment is a vehicle on which the nonaqueous electrolyte secondary battery obtained in the third embodiment or the assembled battery obtained in the fourth embodiment is mounted. The vehicle according to the present invention is characterized in that the non-aqueous electrolyte secondary battery of the present invention or an assembled battery formed by combining a plurality of them is mounted.

  When such a battery is mounted, a plug-in hybrid electric vehicle having a longer EV mileage or an electric vehicle having a longer mileage by one charge can be configured. In other words, the non-aqueous electrolyte secondary battery of the present invention or the assembled battery formed by combining a plurality of these can be used as a power source for driving a vehicle.

  By using a non-aqueous electrolyte secondary battery using the non-aqueous electrolyte secondary battery electrode of the present invention or an assembled battery formed by combining a plurality of them in a vehicle, a vehicle that exhibits the effects described above can be obtained.

  The vehicle is not particularly limited. For example, in the case of a car, a hybrid car, a fuel cell car, an electric car (all are four-wheeled vehicles (passenger cars, commercial vehicles such as trucks and buses, light vehicles, etc.), and motorcycles (motorcycles). ) And tricycles). Further, it can be applied to various power sources for other vehicles such as a moving body such as a train, and can also be used as a mounting power source for an uninterruptible power supply.

  FIG. 5 is a conceptual diagram of a vehicle equipped with the assembled battery of the present invention.

  As shown in FIG. 5, in order to mount the assembled battery 300 on a vehicle such as the electric vehicle 400, the battery pack 300 is mounted under the seat at the center of the vehicle body of the electric vehicle 400. This is because if it is installed under the seat, the interior space and the trunk room can be widened. The place where the assembled battery 300 is mounted is not limited to the position under the seat, but may be a lower part of the rear trunk room or an engine room in front of the vehicle. The electric vehicle 400 using the assembled battery 300 as described above has high durability and can provide sufficient output even when used for a long period of time. Furthermore, it is possible to provide electric vehicles and hybrid vehicles that are excellent in fuel efficiency and running performance. A vehicle equipped with the assembled battery of the present invention can be widely applied to a hybrid vehicle, a fuel cell vehicle and the like in addition to an electric vehicle as shown in FIG.

  The effects of the present invention will be described using the following examples and comparative examples. However, the technical scope of the present invention is not limited to only the forms shown in the following examples.

<Example 1>
(1) Preparation of positive electrode active material E-1 for lithium ion secondary battery Nickel (II) sulfate hexahydrate, manganese (II) sulfate tetrahydrate, and cobalt (II) sulfate heptahydrate are transition metals. Weighed so that the molar ratio of the elements was Ni: Mn: Co = 17: 56: 7, and added to ion-exchanged water to prepare a 2 mol / L sulfate aqueous solution. The temperature of the aqueous sulfate solution was controlled at 25 ° C. and stirred at a constant rate. To this sulfate aqueous solution, a 0.2 mol / L ammonium hydroxide aqueous solution was dropped at a constant rate to adjust the pH value to 7.5. Thereafter, a 0.2 mol / L ammonium hydroxide aqueous solution and a 2 mol / L sodium carbonate aqueous solution were dropped at a constant rate while maintaining the pH at 7.5 to obtain a precipitate A-1. Precipitate A-1 was washed with ion exchange water and suction filtered to remove excess water. Furthermore, in a drier kept at 120 ° C., a small amount of water was evaporated and removed to obtain a composite hydroxide B-1. While maintaining the composite hydroxide B-1 in an air atmosphere at 500 ° C., the composite hydroxide B-1 was calcined over 5 hours to obtain a composite oxide C-1. Among the complex oxides C-1, Ni, Mn, and Co were subjected to composition analysis using an ICP emission spectroscopic analyzer (model number: SPS1500VR, manufactured by Seiko Instruments Inc.). As a result, it was confirmed that the composition and the charged composition in the composite oxide C-1 were matched. Thereafter, the composite oxide C-1 and lithium hydroxide monohydrate were mixed and pulverized so that the molar ratio of each metal element was Li: Ni: Mn: Co = 125: 17: 56: 7. The mixed raw material powder D-1 was obtained. The mixed raw material powder D-1 was held and fired in the air at 900 ° C. for 12 hours to obtain positive electrode active material particles E-1 for a lithium ion secondary battery. When E-1 was visually observed, it was brown.

(2) Measurement of powder X-ray diffraction About the positive electrode active material particle E-1 for lithium ion secondary batteries obtained by said (1), the powder X-ray diffraction was measured. For the measurement, RU-200 (rotary counter cathode type) manufactured by Rigaku Corporation was used, and the measurement was performed under the following conditions.

The result of the powder X-ray-diffraction measurement of the positive electrode active material particle E-1 for lithium ion secondary batteries is shown in FIG. And the peak shown by the uppermost stage in a figure was contrasted with the peak shown by the 2nd stage-the 4th stage (bottom stage). As a result, the observed peak (corresponding to the peak shown at the top in the figure) belongs to Li ₂ MnO ₃ (monoclinic structure) or LiNiO ₂ (α-NaFeO ₂ type structure). It was.

(3) Measurement of color difference meter When the positive electrode active material E-1 for a lithium ion secondary battery obtained in (1) above was measured with a color difference meter, L * a, which is a color space defined by JIS Z 8729 * B color coordinate system color coordinates were a = 4.36, b = 2.09, and L = 17.89, respectively.

For reference, the positive electrode active material particles for a lithium ion secondary battery made of Li ₂ MnO ₃ were measured under the above conditions for L * a * b color system color coordinates, and a = 30.46, respectively. B = 26.14 and L = 39.44.

(4) Production of lithium ion secondary battery 20 mg of positive electrode active material E-1 for lithium ion secondary battery and 12 mg of TAB-2 which is a conductive agent and binder are kneaded and pellet-molded for lithium ion secondary battery A positive electrode was obtained.

The positive electrode for the lithium ion secondary battery produced above, Li metal as the counter electrode (negative electrode), glass filter paper as the separator, and ethylene carbonate (EC) and diethyl carbonate (DMC) containing 1.0 M LiPF ₆ as the electrolyte ) And a mixed solution (1: 2 molar ratio) was used to produce a coin-type bipolar cell.

(5) Measurement of charge / discharge capacity After the above-described coin-type bipolar battery was prepared and 24 hours passed, a charge / discharge test by constant current / constant voltage charge and constant current discharge was started under the following conditions.

Charging: Charging voltage 4.8V, charging time 8 hours, charging current density 0.2 mA / cm ²
Discharge: discharge voltage 2.0 V, discharge current density 0.2 mA / cm ²
However, the upper limit voltage was changed to 4.5V, 4.6V, and 4.7V as the formation in order every 2 cycles (6 cycles in total), and then the test was performed under the above charge / discharge conditions. The obtained discharge capacity was 275 mAh / g.

For reference, the discharge capacity was measured in the same manner as described above except that the cathode active material particles for lithium ion secondary batteries were made of Li ₂ MnO _{3. The} obtained discharge capacity was 21 mAh. / G.

<Example 2>
(1) Preparation of positive electrode active material E-2 for lithium ion secondary battery The molar ratio of each element of the composite oxide C-1 and lithium hydroxide monohydrate in Example 1 was Li: Ni: Mn. : Positive electrode active material particles E-2 for a lithium ion secondary battery were obtained in the same manner as in Example 1, except that mixing and pulverization were performed so that Co: 135: 17: 56: 7. When E-2 was visually observed, it was brown.

(2) Measurement of color difference meter When the positive electrode active material E-2 for lithium ion secondary battery obtained in (1) above was measured with a color difference meter, L * a, which is a color space defined by JIS Z 8729 * B color coordinate system color coordinates were a = 2.11, b = −1.10, and L = 19.52.

(3) Production of Lithium Ion Secondary Battery A lithium ion secondary battery was produced by the same method and conditions as in Example 1 except that E-2 was used as the positive electrode active material for the lithium ion secondary battery.

(4) Measurement of charge / discharge capacity When measured by the same method and conditions as in Example 1, the obtained discharge capacity was 256 mAh / g.

<Example 3>
(1) Production of positive electrode active material E-3 for lithium ion secondary battery The composite oxide C-1 and lithium hydroxide monohydrate in Example 1 were mixed at a molar ratio of each element of Li: Ni: Mn. : Positive electrode active material particles E-3 for a lithium ion secondary battery were obtained in the same manner as in Example 1 except that mixing and pulverization were performed so that Co = 140: 17: 56: 7. When E-3 was visually observed, it was brown.

(2) Measurement of color difference meter When the positive electrode active material E-3 for lithium ion secondary battery obtained in the above (1) was measured with a color difference meter, L * a which is a color space defined by JIS Z 8729 * B color coordinate system color coordinates were a = 1.68, b = −0.95, and L = 19.18, respectively.

(3) Production of Lithium Ion Secondary Battery A lithium ion secondary battery was produced by the same method and conditions as in Example 1 except that E-3 was used as the positive electrode active material for the lithium ion secondary battery.

(4) Measurement of charge / discharge capacity When measured in the same procedure as in Example 1, the obtained discharge capacity was 245 mAh / g.

<Example 4>
(1) Production of positive electrode active material E-4 for lithium ion secondary battery The composite oxide C-1 and lithium hydroxide monohydrate in Example 1 were mixed at a molar ratio of each element of Li: Ni: Mn. : Positive electrode active material particles E-4 for a lithium ion secondary battery were obtained in the same manner as in Example 1 except that the mixture was mixed and pulverized so that Co = 145: 17: 56: 7. When E-4 was visually observed, it was brown.

(2) Measurement of color difference meter When the positive electrode active material E-4 for lithium ion secondary battery obtained in (1) above was measured with a color difference meter, L * a which is a color space defined by JIS Z 8729 * B color coordinate system color coordinates were a = 1.60, b = −0.92, and L = 19.98, respectively.

(3) Production of Lithium Ion Secondary Battery A lithium ion secondary battery was produced by the same method and conditions as in Example 1 except that E-4 was used as the positive electrode active material for the lithium ion secondary battery.

(4) Measurement of charge / discharge capacity When measured in the same procedure as in Example 1, the obtained discharge capacity was 220 mAh / g.

<Example 5>
(1) Preparation of positive electrode active material E-5 for lithium ion secondary battery Synthesize | combined in the same procedure as Example 1 except the point which baked mixed raw material powder D-1 in the said Example 1 at 700 degreeC. Thus, positive electrode active material particles E-5 for a lithium ion secondary battery were obtained. When E-5 was visually observed, it was brown.

(2) Measurement of color difference meter When the positive electrode active material E-5 for lithium ion secondary battery obtained in (1) above was measured with a color difference meter, L * a, which is a color space defined by JIS Z 8729 * B color coordinate system color coordinates were a = 5.70, b = 5.81, and L = 18.51 respectively.

(3) Production of Lithium Ion Secondary Battery A lithium ion secondary battery was produced by the same method and conditions as Example 1 except that E-5 was used as the positive electrode active material for the lithium ion secondary battery.

(4) Measurement of charge / discharge capacity When measured in the same procedure as in Example 1, the obtained discharge capacity was 245 mAh / g.

<Comparative Example 1>
(1) Production of positive electrode active material E-6 for lithium ion secondary battery Lithium ion secondary was performed in the same manner as in Example 1 except that the mixed raw material powder D-1 in Example 1 was baked at 1000 ° C. The positive electrode active material particle E-6 for batteries was obtained. When E-6 was visually observed, it was black.

(2) Measurement of color difference meter When the positive electrode active material E-6 for lithium ion secondary battery obtained in (1) above was measured with a color difference meter, L * a, which is a color space defined by JIS Z 8729 * B color coordinate system color coordinates were a = 2.43, b = -1.20, and L = 18.94, respectively.

(3) Production of Lithium Ion Secondary Battery A lithium ion secondary battery was produced by the same method and conditions as Example 1 except that E-6 was used as the positive electrode active material for the lithium ion secondary battery.

(4) Measurement of charge / discharge capacity When measured in the same procedure as in Example 1, the obtained discharge capacity was 201 mAh / g.

  The significant difference between the results of the above examples and comparative examples is due to the value of the L * a * b color system color coordinate of the positive electrode active material. Furthermore, in the said comparative example 1, it is estimated that a calcination temperature is so high that it may cause partial volatilization of Li, and a rock salt type crystal structure with inferior properties is partially generated. Therefore, it is considered that a significant difference in the results of the discharge capacity between the above example and the comparative example occurred.

<Reference Example 1>
(1) Simultaneous analysis of thermogravimetry and differential heat About the mixed raw material powder D-1 obtained in Example 1, the simultaneous analysis of thermogravimetry (TG) and differential heat (DTA) was performed on the following conditions. An apparatus used for such simultaneous analysis is generally referred to as a differential thermothermal gravimetric simultaneous measurement apparatus (TG / DTA).

  The measurement results of the simultaneous analysis of thermogravimetry and differential heat are shown in FIG. In FIG. 7, the upper curve shows a weight loss curve (TG, mass%), and the lower curve shows a differential heat curve (DTA, μV). Looking at the weight loss curve (TG, mass%), the intersection where the rapid decrease occurs is about 60 ° C. and −2.5%, and the points where the sudden decrease in weight falls are about 100 ° C. and −16.5 ° C. It turns out that it is. After that, as can be seen from the numerical values of 1200 ° C. and −26.6%, the weight decreases only moderately. On the other hand, in the differential heat curve (DTA, μV), endotherm due to melting near 40 ° C. and 419 ° C. and heat generation due to thermal decomposition near 79 ° C. are observed.

  In order to obtain high-performance positive electrode active material particles for a lithium ion secondary battery that sufficiently exhibit the desired effect of the present application by firing the mixed raw material powder in an air atmosphere, a preferable firing temperature is about 419 ° C. or higher. It has been found that a more preferable firing temperature is 500 ° C. or higher. The “500 ° C.” is derived as a result of microscopically viewing the weight loss curve and the differential heat curve of FIG. Furthermore, it has also been found that the firing temperature is particularly preferably 700 ° C. or higher in consideration of the firing time required for the reaction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view schematically showing an outline of a stacked lithium ion secondary battery that is not a stacked flat bipolar type, which is a typical embodiment of the lithium ion battery of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view schematically showing an appearance of a stacked flat lithium ion secondary battery that is a typical embodiment of a lithium ion battery according to the present invention. It is the cross-sectional schematic which represented typically the outline | summary of the laminated flat bipolar lithium ion secondary battery which is another typical embodiment of the lithium ion battery of this invention. FIG. 4A is an external view schematically showing a typical embodiment of an assembled battery according to the present invention, and FIG. 4A is a plan view of the assembled battery. FIG. 4B is an external view schematically showing a typical embodiment of the assembled battery according to the present invention, and FIG. 4B is a front view of the assembled battery. FIG. 4C is an external view schematically showing a typical embodiment of the assembled battery according to the present invention, and FIG. 4C is a side view of the assembled battery. It is a conceptual diagram of the vehicle carrying the assembled battery of this invention. It is a graph which shows the result of the powder X-ray-diffraction measurement of the positive electrode active material particle E-1 for lithium ion secondary batteries. It is a graph which shows the measurement result of the simultaneous analysis of thermogravimetry and differential heat.

Explanation of symbols

10, 50 lithium ion battery,
10 'bipolar battery,
11 Positive electrode current collector, current collector,
11a The outermost layer current collector on the positive electrode side,
11b The outermost layer current collector on the negative electrode side,
12 negative electrode current collector,
13 positive electrode, positive electrode active material layer,
14 negative electrode current collector,
14a outermost layer negative electrode current collector,
15 negative electrode, negative electrode active material layer,
17 electrolyte layer,
19 single battery layer (= battery unit or single cell),
21, 57 Battery element, power generation element, battery element (power generation element; laminate),
52 Battery exterior material,
25 positive current collector,
27 negative current collector,
29 Laminate sheet, laminate film,
31 seal part,
58 positive electrode tab,
59 Negative electrode tab,
250 small battery pack,
300 battery packs,
310 connection jig,
400 Electric car.

Claims (7)

L * a * b color system color coordinates which are color spaces defined by JIS Z 8729 are 0 <a <10, −1.2 <b <20.0, and 0 <L <30, and , composition formula _{Li w Ni x Mn y Co z} O represented by _{2 + [delta],} the positive electrode active material for a nonaqueous electrolyte secondary battery.
In that case, 1.1 <w <1.5, 0.1 <x <0.4, 0.4 <y <0.9, 0 <z <0.2, w + x + y + z = 2, and −0. 2 <δ <0.2.   The positive electrode active material for nonaqueous electrolyte secondary batteries according to claim 1, which is fired at 700 ° C or higher and lower than 1000 ° C.   The positive electrode for nonaqueous electrolyte secondary batteries containing the positive electrode active material for nonaqueous electrolyte secondary batteries of Claim 1 or 2.   A nonaqueous electrolyte secondary battery comprising the positive electrode for a nonaqueous electrolyte secondary battery according to claim 3.   The nonaqueous electrolyte secondary battery according to claim 4, which is a bipolar nonaqueous electrolyte secondary battery.   An assembled battery comprising the nonaqueous electrolyte secondary battery according to claim 4.   A vehicle comprising the nonaqueous electrolyte secondary battery according to claim 4 or 5 or the assembled battery according to claim 6.