Electrode, battery, and battery pack

Abstract

According to an embodiment of the present invention, there is provided an electrode containing active material matter, a conductive agent, and a binding agent. The active material matter contains an active material containing a lithium nickel cobalt manganese oxide. The ratio IAVE / ITOP of the average peak intensity IAVE at ±20°C from the peak top to the peak top intensity ITOP of the strongest peak in the m / z = 132 curve by thermally evolved gas analysis mass spectrometry is equal to or greater than 0.2 and less than 0.5. The ratio A44 / A132 of the area A44 under the m / z=44 curve in the range between 550°C and 600°C inclusive by thermally-induced evolved gas mass spectrometry to the area A132 under the m / z = 132 curve in the range between 200°C and 550°C inclusive is equal to or greater than 5 and less than 10.

Description

Electrodes, batteries and battery packs

[0001] The embodiments relate to an electrode, a battery, and a battery pack.

[0002] In recent years, non-aqueous electrolyte batteries have been expected to be applied to large systems such as electric aircraft, power storage, etc., as well as to attempts to replace gasoline as the power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs). Therefore, improvements in capacity, large current output performance, and long life performance in high-temperature environments are required.

[0003] Nickel-cobalt-manganese oxide (NCM) is an example of an active material for nonaqueous electrolyte batteries. Examples of NCM include polycrystalline NCMs, which form secondary particles formed by aggregation of fine primary particles. However, the use of such high-specific-surface-area positive electrode active materials is prone to oxidation reactions between the positive electrode and the electrolyte, particularly during charge-discharge cycles and storage at high potentials, resulting in significant gas generation and resistance increases. Furthermore, cracking of the positive electrode active material particles and changes to a degraded structure such as a rock salt structure occur during charge-discharge cycles, resulting in poor battery life.

[0004] As the negative electrode active material, for example, spinel-type lithium titanate (e.g., Li4Ti5O 12 ) is used. Spinel-type lithium titanate reacts at a potential 0.5 V or more higher than the Li reaction potential, thereby suppressing the precipitation of lithium dendrites. As a result, spinel-type lithium titanate can avoid risks such as short circuits, self-discharge, and fire, making it possible to provide a battery that is highly safe and has excellent life performance. Furthermore, increasing the specific surface area of ​​spinel-type lithium titanate enables the battery to have a high output.

[0005] However, increasing the specific surface area increases the amount of water adsorbed onto the negative electrode. During battery operation, water adsorbed to the negative electrode is electrolyzed to produce hydrogen and oxygen through an electrode reaction, resulting in increased gas generation. Furthermore, water can react with the lithium compound contained in the non-aqueous electrolyte to produce lithium fluoride (LiF) on the negative electrode. The presence of LiF on the electrode prevents lithium from being inserted into the electrode active material, increasing electrical resistance.

[0006] Japanese Patent Publication No. 2007-103134 Japanese Patent Publication No. 2013-534031 Japanese Patent Publication No. 2019-164960 Japanese Patent Publication No. 2022-41225 Japanese Patent Publication No. 2022-41229

[0007] The problem to be solved is to provide an electrode that can realize a battery with excellent life performance, and a battery and a battery pack that include this electrode.

[0008] According to an embodiment, an electrode is provided, which includes an active material, a conductive agent, and a binder. The active material includes an active material containing a lithium-nickel-cobalt-manganese-containing oxide. The peak top intensity I of the most intense peak in the curve at m / z=132 measured by thermal evolved gas-mass spectrometry is TOP Average value of peak intensity at ±20°C from the peak top I AVE Ratio of I AVE / I TOP The area A under the curve for m / z=132 in the range of 200°C to 550°C is 0.2 or more and less than 0.5. 132 The area A under the curve of m / z=44 by thermal evolution gas-mass spectrometry in the range of 550°C to 600°C 44 Ratio A 44 / A 132 is 5 or more and less than 10.

[0009] According to the embodiment, a battery is provided that includes a positive electrode made of the electrode of the embodiment and a negative electrode.

[0010] According to an embodiment, a battery pack is provided that includes the battery of the embodiment.

[0011] FIG. 1 is an example curve for m / z=132 obtained by thermal evolved gas-mass spectrometry. FIG. 2 is an example curve for m / z=44 obtained by thermal evolved gas-mass spectrometry. FIG. 3 is a plan view schematically showing an example electrode according to an embodiment. FIG. 4 is a cross section of an example battery according to an embodiment cut in the thickness direction. FIG. 5 is an enlarged cross section of part A in FIG. 4. FIG. 6 is a partially cutaway perspective view of another example battery according to an embodiment. FIG. 7 is an exploded perspective view of an example battery pack according to an embodiment. FIG. 8 is a block diagram showing the electrical circuit of the battery pack shown in FIG. 7. Embodiment

[0012] The following techniques have been proposed. In one example, a coating solution is prepared by kneading a cathode material containing a cathode active material with water, and then reacting the alkaline compound produced by the reaction between the cathode active material and water with CO2 to generate carbonates on the surface of the cathode material. This prevents contact between the carbon material and the electrolyte, thereby suppressing the decomposition reaction of the electrolyte. It has also been reported that adding a highly alkaline organic material to the electrode improves the adhesion of the electrode material. It has also been reported that adding acetic anhydride, an acid, to a cathode composite paste containing a certain amount of LiOH removes LiOH and Li2CO3 from the surface of the cathode active material, thereby reducing reaction resistance and increasing output at low temperatures. Furthermore, it has been reported that adding a dispersant to a slurry composition for electrochemical device electrodes can prepare a slurry composition with excellent dispersion stability over time and improves the rate performance and high-temperature storage properties of the resulting electrochemical device. It has also been reported that an electrode comprising an electrode mixture layer containing a conductive material including carbon nanotubes and a dispersant can improve the cycle characteristics, rate characteristics, and high-temperature storage characteristics of an electrochemical device.

[0013] As a result of extensive research, the inventors have discovered that excessive binding of the binder to the conductive agent reduces the binding of the binder to the active material, resulting in a decrease in lifespan performance. Excessive binding of the binder to the conductive agent reduces the dispersibility of the conductive agent, causing the conductive agent to aggregate, resulting in current unevenness in the electrode during charging and discharging, and a decrease in lifespan performance. Furthermore, reduced binding of the binder to the active material makes it impossible to suppress the effects of volumetric expansion and contraction of the active material during charging and discharging, which can lead to peeling of the electrode mixture layer from the current collector and cracking of the electrode. Based on these findings, the inventors have discovered that lifespan performance can be improved by suppressing excessive binding of the conductive agent and binder and uniformly dispersing the active material, conductive agent, and binder in the electrode.

[0014] First Embodiment According to a first embodiment, an electrode is provided. The electrode includes an active material containing a lithium-nickel-cobalt-manganese-containing oxide, a conductive agent, and a binder. In a thermogram of the electrode obtained by thermal evolved gas-mass spectrometry, the peak top intensity I of the most intense peak in the curve at m / z=132 is TOP The average value of the peak intensity in the range of 20°C before and after the peak top for AVE Ratio of I AVE / I TOP The area A under the curve of m / z=132 in the thermogram of the electrode measured by thermal evolved gas-mass spectrometry in the range of 200°C to 550°C is 0.2 or more and less than 0.5. 132 The area A under the curve for m / z=44 in the range of 550°C to 600°C 44 Ratio A 44 / A 132 is 5 or more and less than 10.

[0015] The above ratios for the m / z=132 curve and the m / z=44 curve obtained by Evolved Gas Analysis - Mass Spectrometry (EGA-MS) are indicators of the degree of binding of the binder to the active material and conductive agent. In detail, the magnitude of the peak after 550°C in the m / z=44 curve indicates the amount of binding between the active material and the binder, and the kurtosis of the peak with the highest intensity in the m / z=132 curve indicates the degree of binding between the conductive agent and the binder. The most intense peak in the m / z=132 curve is the ratio I AVE / I TOP The kurtosis is 0.2 or more and less than 0.5, and the ratio A of the area under the m / z=132 curve and the area under the m / z=44 curve 44 / A 132 In an electrode where the ratio is 5 or more and less than 10, the conductive agent is well dispersed and the binder is appropriately bound to the active material, so that the electrode can exhibit excellent life performance.

[0016] Specifically, the binding between the conductive agent and the binder is suppressed, reducing the aggregation of the conductive agent. Suppressing the binding between the conductive agent and the binder also promotes the binding of the binder to the active material, resulting in a more uniform electrode. Uniform dispersion of the binder between the active material and the conductive agent reduces current unevenness during charging and discharging. This reduces localized deterioration and resistance increases in the electrode, allowing the capacity to be maintained even with repeated charge-discharge cycles, resulting in high life performance. The moderate amount of binder bound to the active material prevents the conductive path from being broken by the expansion and contraction of the active material during charge and discharge, resulting in high life performance. Furthermore, the active material surface area in contact with the electrolyte is reduced, reducing gas generation due to the reaction between the electrolyte and the active material, resulting in excellent life performance.

[0017] In other words, the dispersibility of the conductive agent in the electrode and the coverage of the binder on the active material can be evaluated by EGA-MS analysis.

[0018] The dispersibility of the conductive agent can be estimated by looking at the curve derived from the component detected as m / z=132 in the thermogram obtained when the electrode is subjected to EGA-MS analysis. The m / z=132 curve can be attributed to trifluorobenzene. A typical example of a binder is polyvinylidene fluoride (PVdF). PVdF's polymer chain breaks when heated, resulting in its detection as trifluorobenzene in EGA-MS. Therefore, the m / z=132 curve indicates the progression of PVdF decomposition. When PVdF comes into contact with the conductive agent in the electrode, the catalytic action shifts the decomposition temperature to lower temperatures, and the highest intensity peak in the m / z=132 curve broadens. Therefore, the kurtosis of the highest intensity peak in the m / z=132 curve serves as an indicator of the conductive agent's dispersibility.

[0019] An example of the m / z=132 curve is shown in Figure 1. Figure 1 shows an example of an m / z=132 curve obtained by EGA-MS analysis. The dotted curve 10 was obtained using a sample containing PVdF alone. The dashed-dotted curve 100 was obtained using a sample containing an electrode with low conductive agent dispersibility and a high degree of PVdF binder binding to the conductive agent. Because of the high amount of PVdF in contact with the catalytic conductive agent, the peak top position shifted toward lower temperatures and became broader compared to the PVdF alone (curve 10). The solid curve 110 was obtained using a sample containing an electrode with increased conductive agent dispersibility, resulting in reduced PVdF binding to the conductive agent. As shown, the maximum intensity peak of this curve 110 is less shifted toward lower temperatures and is sharper, approaching the peak position and shape of the curve 10 obtained from the PVdF alone sample.

[0020] The coverage of the active material by the binder can be estimated by referring to the curve derived from the component detected as m / z=44 in the thermogram obtained when the electrode is subjected to EGA-MS analysis. The curve for m / z=44 is carbon dioxide (CO ２ The peaks appearing after 550°C in the m / z=44 curve are due to carbon dioxide (CO ) generated by decomposition of the binder, such as PVdF, that was bound to the active material. ２ The higher the intensity of this peak, the more the binder was bound to the active material.

[0021] An example of the m / z=44 curve is shown in Figure 2. Figure 2 is an example of an m / z=44 curve obtained by EGA-MS analysis. The dashed-dotted curve 20 was obtained using an electrode sample with low conductive agent dispersibility and a high PVdF binder binding to the conductive agent. Because of the high binding between PVdF and the conductive agent, less PVdF was bound to the active material. The solid curve 220 was obtained using an electrode sample with increased conductive agent dispersibility, resulting in less PVdF binding to the conductive agent. The PVdF bound to the conductive agent is reduced, but the PVdF bound to the active material is increased. The intensity of the peaks above 550 °C is higher for curve 220, obtained using a sample with a high PVdF binding to the active material, than for curve 20, obtained using a sample with a low PVdF binding to the active material.

[0022] The electrode of the embodiment will be described in detail below. The electrode of the embodiment may be a positive electrode or a negative electrode.

[0023] The electrode includes, for example, a mixture layer and a current collector on which the mixture layer is laminated. The mixture layer includes an active material, a conductive agent, and a binder.

[0024] The active material contains at least a lithium nickel cobalt manganese-containing oxide as an active material (referred to as a first active material). An example of the lithium nickel cobalt manganese-containing oxide is lithium nickel cobalt manganese oxide. The lithium nickel cobalt manganese-containing oxide may be, for example, Li a Ni (1-b-c-d) Co b Mn c M d In the above formula, 1≦a≦1.2, 0<b≦0.4, 0<c≦0.4, 0≦d≦0.1, and M is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Y, B, Mo, Nb, Zn, Sn, Zr, Ga, and V.

[0025] The lithium nickel cobalt manganese-containing oxide represented by the above formula has a large capacity per unit weight and a low potential of 4.2 V (vs. Li / Li ＋A large capacity can be obtained by using the electrode up to a potential of 1.05 or more. The molar ratio a in the formula can be varied depending on the insertion and desorption of lithium ions into and from the electrode. A more preferable range is 1.05≦a≦1.15.

[0026] By setting the molar ratio b in the formula to 0<b≦0.4 and the molar ratio c to 0<c≦0.4, the lithium nickel cobalt manganese-containing oxide contains Co and Mn as transition metals in addition to Ni, thereby increasing the capacity per unit weight. More preferred ranges for the molar ratios b and c are 0.05≦b≦0.2 and 0.05≦c≦0.2.

[0027] A more preferred range for the molar ratio d of element M in the formula is 0.01≦d≦0.05. By including element M, for example, the following effects can be obtained: Al can reduce lattice distortion, thereby improving Li-ion diffusibility; Mg can improve bulk electronic conductivity, thereby improving apparent discharge capacity; and further, cycle stability under high voltage can be improved. Zr can improve cycle performance. Ti can improve cycle performance by mitigating phase changes under high-voltage charge / discharge. Ga can improve bulk electronic conductivity, thereby improving cycle performance.

[0028] The lithium nickel cobalt manganese-containing oxide may contain elements other than those described above as inevitable impurities.

[0029] The lithium nickel cobalt manganese-containing oxide may have a particle shape. Examples of the lithium nickel cobalt manganese-containing oxide particles include single particles (also called single primary particles) and secondary particles (also called polycrystalline bodies) formed by aggregation of primary particles. A mixture of single particles and secondary particles may also be used. Polycrystalline lithium nickel cobalt manganese-containing oxides can increase the specific surface area, but are prone to electrolyte oxidation during high-potential charge / discharge cycles or calendar tests, resulting in greater gas generation and resistance increases than single particles. Furthermore, cracking of the active material particles and changes to a degraded structure such as a rock salt structure may occur during cycling. Single particles of lithium nickel cobalt manganese-containing oxides are less likely to crack than secondary particles, preventing cracking and the exposure of new surfaces. By preventing the exposure of new surfaces, the increase in the reaction between the electrolyte and the active material can be suppressed.

[0030] The active material may contain an active material (second active material) other than the lithium-nickel-cobalt-manganese-containing oxide. The second active material may include various oxides, for example, lithium-containing cobalt oxide (e.g., LiCoO ２ ), manganese dioxide, lithium manganese composite oxide (e.g., LiMn ２ O ４ , LiMnO ２ ), lithium-containing nickel oxide (e.g., LiNiO ２ ), lithium-containing nickel cobalt oxide (e.g., LiNi ０．８ Co ０．２ O ２ The active material may contain one or more types of active material, such as lithium-containing iron oxide, lithium-containing vanadium oxide, or chalcogen compounds such as titanium disulfide and molybdenum disulfide.

[0031] It is desirable that the active material particles containing the lithium-nickel-cobalt-manganese-containing oxide have a higher proportion of single particles than secondary particles. This can suppress cracking of the active material particles. Active material particles with a breaking strength of 30 MPa or more and 300 MPa or less can suppress cracking, thereby suppressing an increase in the reaction between the electrolyte and the active material. A more preferable range of the breaking strength is 120 MPa or more and 300 MPa or less.

[0032] The active material containing the lithium nickel cobalt manganese-containing oxide has a ratio D in the cumulative frequency distribution on a volume basis of particle size based on particle size distribution by laser diffraction scattering method. ９０ / D １０ Here, the particle size distribution is a cumulative frequency distribution on a volume basis, accumulating from the smallest particle size of the active material. １０ is the particle size at which the cumulative frequency from the small particle size side of the cumulative frequency distribution becomes 10%. ９０ is the particle size at which the cumulative frequency from the small particle size side of the cumulative frequency distribution becomes 90%. ９０ / D １０ The particle size distribution where the ratio D is 4 or less is sharp and has high monodispersity. ９０ / D １０ An active material having a particle size distribution where the ratio D is 4 or less can suppress cracking, and therefore can suppress an increase in alkaline components. ９０ / D １０ is an index showing the variation in particle size, and a smaller value means a smaller variation. When all particles have the same particle size, the ratio D ９０ / D １０ becomes 1.

[0033] The particles of the active material containing the lithium nickel cobalt manganese-containing oxide have an average particle diameter D ５０ The thickness can be set to 2 μm or more and 8 μm or less. ５０ is the particle size at which the cumulative frequency from the small particle size side of the cumulative frequency distribution becomes 50%.

[0034] The content of the first active material (lithium nickel cobalt manganese-containing oxide) in the active material can be in the range of 50% by mass to 99.6% by mass.

[0035] The active material preferably contains 0.4% by mass or more and 1% by mass or less of an alkaline component. The alkaline component includes at least one of lithium carbonate (Li2CO3) and lithium hydroxide (LiOH). The alkaline component may be derived from, for example, raw materials used in synthesizing the lithium-nickel-cobalt-manganese-containing oxide. The alkaline component may be residual alkali content from the synthesis of the active material.

[0036] The amount of binder binding to the active material correlates with the alkaline component contained in the active material. To appropriately adjust the amount of binder binding to the active material, it is desirable to include an appropriate amount of alkaline component in the active material. When the content of alkaline component in the active material is 0.4% by mass or more, the amount of binder binding to the active material is sufficient. This causes a crosslinking reaction of the binder to proceed due to the polyenation reaction of the binder, increasing the binding strength between the composite layer and the current collector. The increased binding strength allows the composite layer to be maintained on the current collector during charge / discharge cycles, making it less likely that the conductive path within the electrode will be damaged, resulting in uneven deterioration within the electrode and therefore reducing the rate of resistance increase and improving life performance. Furthermore, since the binder is bound to the active material, the surface area available for electrolyte contact with the active material is reduced, thereby suppressing the generation of gases such as hydrogen fluoride (HF) that are generated by side reactions between the electrolyte and the active material. If the content of the alkaline component in the active material is within 1% by mass, the amount of binder adhering to the active material will not be excessive. This appropriately suppresses the progress of the binder's polyenation reaction, thereby keeping the acceleration of the binder's crosslinking reaction at a certain level. This increases the adhesive strength between the composite layer and the current collector while suppressing the increase in resistance due to the active material being coated with the binder. Therefore, the rate of increase in resistance is reduced, improving the life performance. A more preferred range for the content of the alkaline component in the active material is 0.5% by mass or more and 0.7% by mass or less.

[0037] The alkaline component may be, for example, attached to or precipitated on the active material particles in a solid state. More specifically, the alkaline component may be attached to or precipitated on the surfaces of the active material particles or on the grain boundaries of the active material particles in a solid state.

[0038] The binder may include polyvinylidene fluoride (PVdF) and its derivatives as a first binder. The PVdF derivative may be, for example, PVdF having a COOZ group. Here, Z contains at least one element of H or Li. The COOZ group may be bonded to the main chain or a side chain of PVdF. Alternatively, the PVdF derivative may be, for example, PVdF having a COOX group. The COOX group is a carboxylate group. An example of X is Li. The COOX group may be generated by the reaction of a COOH group with an active material. For example, when the active material contains an alkaline component, it is presumed that the alkaline component causes a polyenization reaction of PVdF having a COOH group, and the COOH group (carboxy group) is modified into a COOX group (carboxylate group).

[0039] The content of the first binder in the mixture layer can be, for example, in the range of 0.5% by mass to 5% by mass.

[0040] The binder may contain a binder other than the first binder (referred to as a second binder). Examples of the second binder include polytetrafluoroethylene (PTFE), fluorine-based rubber, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyimide, polyamide, etc. The type of binder can be one type or two or more types.

[0041] The conductive agent may be, for example, a carbon material. Specific examples include carbon black such as acetylene black and ketjen black, graphite, carbon fiber, carbon nanotubes, and fullerene. The conductive agent may be one type or two or more types.

[0042] The blending ratio of the active material, conductive agent, and binder in the composite layer is preferably 75% by mass or more and 96% by mass or less of the active material, 3% by mass or more and 20% by mass or less of the conductive agent, and 1% by mass or more and 5% by mass or less of the binder.

[0043] The density of the composite layer is, for example, 3.1 g / cm 3 3.5g / cm or more 3 It can be the following:

[0044] The electrode may further include a polymer having a functional group that adsorbs to the conductive agent in the composite layer. The polymer may be added as a dispersant to improve the dispersibility of the conductive agent during electrode fabrication. Examples of such a polymer include a polymer made of a nitrogen-containing monomer. Specific examples include polymers that can be used as dispersants, as described below.

[0045] The polymer may be contained in the composite layer in an amount of, for example, 2% or more, 3% or more, or 5% or more by mass relative to the conductive agent, and may be contained in the composite layer in an amount of, for example, 20% or less, 15% or less, or 10% or less by mass relative to the conductive agent.

[0046] The current collector is preferably an aluminum foil or an aluminum alloy foil, and its average crystal grain size is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 5 μm or less. A current collector made of an aluminum foil or an aluminum alloy foil having such an average crystal grain size can dramatically increase the strength, making it possible to densify the electrode with a high pressing pressure, and thereby increasing the battery capacity.

[0047] The thickness of the current collector is preferably 20 μm or less, more preferably 15 μm or less. The purity of the aluminum foil is preferably 99% or more. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. On the other hand, the content of transition metals such as iron, copper, nickel, and chromium is preferably 1% or less.

[0048] The electrode is fabricated, for example, by suspending an active material, a conductive agent, a binder, and a dispersant in a suitable solvent, applying the resulting slurry to a current collector, drying the slurry, and then pressing the resulting mixture layer. Alternatively, the active material, the conductive agent, the binder, and the dispersant may be formed into pellets and used as the mixture layer.

[0049] The active material can be synthesized by, for example, a solid-phase reaction method or a co-precipitation method.

[0050] According to the solid-state reaction method, powder raw materials of nickel oxide, cobalt oxide, manganese oxide, and lithium oxide (LiOH, Li2CO3, etc.) are weighed and mixed to obtain a predetermined composition, and then heat-treated at a high temperature to obtain an active substance material containing a lithium-nickel-cobalt-manganese-containing oxide (first compound).

[0051] According to the coprecipitation method, an active material containing a lithium-nickel-cobalt-manganese-containing oxide (first compound) can be obtained as follows. A solution containing a nickel salt, a cobalt salt, and a manganese salt is prepared, and the acidity of the uniformly stirred solution is adjusted to basicity to cause precipitation and obtain a first precursor. The first precursor is then washed and mixed with a lithium salt (LiOH, Li2CO3, etc.) to obtain a second precursor. The second precursor is then heat-treated at high temperature to obtain the target product.

[0052] During the synthesis, the amount of residual alkaline component in the resulting active material can be appropriately adjusted by changing the amount of lithium salt (LiOH, Li2CO3, etc.) used as the raw material and the composition ratio of Ni, Co, and Mn. Furthermore, the amount of alkaline component can be reduced by washing the active material with water. By appropriately adjusting the amount of alkaline component in this way, the binder can be crosslinked appropriately, allowing for control of the coating ability of the active material.

[0053] The dispersant that improves the dispersion of the conductive agent is not particularly limited as long as it has a functional group that adsorbs to the conductive agent. The dispersant may be, for example, a polymer made of a nitrogen-containing monomer. Among these, a dispersant that has good adsorption to a carbon material-based conductive agent such as carbon black is desirable.

[0054] Specific examples of dispersants include polymers containing a nitrile group-containing monomer unit and an alkylene structural unit. The nitrile group-containing monomer unit can be formed using one or more α,β-ethylenically unsaturated nitrile monomers. Examples of the α,β-ethylenically unsaturated nitrile monomers include acrylonitrile, α-halogenoacrylonitriles such as α-chloroacrylonitrile and α-bromoacrylonitrile, methacrylonitrile, and α-alkylacrylonitriles such as α-ethylacrylonitrile. The alkylene structural unit is a -C ｎ H ２ｎ The subscript n in the above formula is an integer of 2 or more.

[0055] Another specific example of the dispersant is a polymer containing a structural unit represented by the following structural formula (1). This structural unit can be adsorbed onto the surface of the conductive agent. The polymer may be a copolymer containing other structural units in addition to the structural unit represented by the following structural formula (1).

[0056]

[0057] In the above structural formula (1), R １ , R ２ , and R ３ is at least one selected from the group consisting of a hydrogen atom, a methyl group, and an ethyl group. １ , R ２ , and R ３ may be the same as or different from each other. １ is an oxygen atom or NH. ４ is a hydrocarbon group having 8 to 30 carbon atoms.

[0058] From the viewpoint of improving the dispersibility of the conductive agent, R 1 and R 2 is preferably a hydrogen atom. 3 is preferably a hydrogen atom or a methyl group. 3 is more preferably a methyl group. 4 is preferably an alkyl group or an alkenyl group. 4 The number of carbon atoms in R is preferably 12 or more, and more preferably 16 or more.4 The number of carbon atoms in R is preferably 24 or less, and more preferably 22 or less. 4 More specifically, examples of the alkyl group include an octyl group, a 2-ethylhexyl group, a decyl group, a lauryl group, a myristyl group, a cetyl group, a stearyl group, an oleyl group, and a behenyl group.

[0059] In synthesizing the polymer, examples of monomers that provide the structural units include ester compounds and amide compounds. Specific examples of ester compounds include 2-ethylhexyl(meth)acrylate, octyl(meth)acrylate, lauryl(meth)acrylate, stearyl(meth)acrylate, isostearyl(meth)acrylate, and behenyl(meth)acrylate. Specific examples of amide compounds include 2-ethylhexyl(meth)acrylamide, octyl(meth)acrylamide, lauryl(meth)acrylamide, stearyl(meth)acrylamide, and behenyl(meth)acrylamide.

[0060] Another specific example of a dispersant is a polymer containing 2-(meth)acrylamido-2-methylpropanesulfonic acid (salt) as a constituent monomer. "2-(meth)acrylamido-2-methylpropanesulfonic acid (salt)" includes 2-(meth)acrylamido-2-methylpropanesulfonic acid and its salts. 2-(meth)acrylamido-2-methylpropanesulfonate salts include salts of 2-(meth)acrylamido-2-methylpropanesulfonic acid with inorganic bases, and salts of 2-(meth)acrylamido-2-methylpropanesulfonic acid with organic bases. Examples of inorganic bases include ammonia, metal hydroxides, and alkali metal carbonates. Examples of organic bases include mono- to trialkylamines having an alkyl group of 1 to 8 carbon atoms. The polymer may be a copolymer containing 2-(meth)acrylamido-2-methylpropanesulfonic acid (salt) and other constituent monomers.

[0061] The amount of dispersant added to the slurry is, for example, 2% or more by mass relative to the conductive agent. The amount of dispersant added is preferably 3% or more, more preferably 5% or more (mass ratio relative to the conductive agent). The amount of dispersant added is, for example, 20% or less by mass relative to the conductive agent. The amount of dispersant added is preferably 15% or less, more preferably 10% or less (mass ratio relative to the conductive agent). By adding an appropriate amount of dispersant, the dispersant binds to the conductive agent to promote dispersion, reducing the binding between the binder and the conductive agent and reducing the aggregation of the conductive agent. Since uneven reaction due to aggregates of the conductive agent is less likely to occur, localized deterioration of the electrode is suppressed and the life performance is improved. As described above, since the dispersant is an organic component, it can become a resistive component within the electrode. Therefore, it is desirable not to add an excessive amount of dispersant. By appropriately adjusting the amount of dispersant added, the binder in the electrode is less likely to bind to the conductive agent, making it less likely for aggregates of the conductive agent to form and allowing it to be uniformly dispersed throughout the electrode. This allows the cycle life performance of a battery using the electrode to be improved.

[0062] As described above, by appropriately controlling the amount of alkaline component contained in the active material and adding an appropriate amount of dispersant that improves the dispersibility of the conductive agent, the conductive agent can be uniformly dispersed while suppressing excessive binding between the conductive agent and the binder, and the binding of the binder to the active material can be promoted. In other words, the ratio I AVE / I TOP and the above-mentioned area ratio A between the m / z=44 curve and the m / z=132 curve. 44 / A 132 This can be controlled by the amount of dispersant added and the amount of residual alkali contained in the active material.

[0063] Increasing the amount of dispersant increases the bonding between the conductive agent and dispersant, suppressing contact between the conductive agent and binder and tending to increase the dispersibility of the conductive agent. Because the catalytic action of the conductive agent to lower the decomposition temperature of the binder is reduced, the shift of the most intense peak of the m / z=132 curve to the lower temperature side is reduced, resulting in a sharper peak with a kurtosis approaching that of the peak obtained with the binder alone. Conversely, decreasing the amount of dispersant tends to decrease the dispersibility of the conductive agent and increase the bonding with the binder. Because the decomposition temperature of the binder is lowered by the catalytic action of the conductive agent, the most intense peak of the m / z=132 curve shifts to the lower temperature side and becomes broader. Therefore, when the amount of dispersant is large, the relative I AVE / I TOP The amount of dispersant is small, and the ratio I AVE / I TOP The dispersibility of the conductive agent can be controlled by adjusting the amount of dispersant added appropriately.

[0064] When the amount of residual alkali contained in the active material increases, the binder tends to adhere to the active material more easily. CO generated by the decomposition of the binder on the active material in EGA-MS analysis ２ On the other hand, if the amount of residual alkali contained in the active material is small, the CO generated by the decomposition of the binder in EGA-MS analysis will be ２ Therefore, when the amount of alkaline component contained in the active material is large, the area ratio A 44 / A 132 The amount of alkaline component is small, and the area ratio A 44 / A 132 By adjusting the amount of the alkaline component appropriately, it is possible to control the coverage of the binder on the active material.

[0065] As shown by the peak kurtosis of the m / z=132 curve, the conductive agent is well dispersed, resulting in uniform charge-discharge reactions within the electrode and excellent cycle life performance for the battery. As shown by the area ratio between the m / z=44 curve and the m / z=132 curve, the binder is appropriately coated on the active material, suppressing the effects of expansion and contraction of the active material during charge and discharge. It also suppresses the elution of alkaline components from the active material surface, thereby suppressing the generation of hydrogen fluoride. This reduces gas generation and capacity loss during charge-discharge cycles, resulting in excellent cycle life performance for the battery.

[0066] Next, specific examples of the electrodes according to the first embodiment will be described with reference to the drawings.

[0067] 3 is a partially cutaway plan view schematically illustrating an example of an electrode according to an embodiment, in which an example positive electrode is illustrated as an example of the electrode.

[0068] 3 includes a positive electrode current collector 3 a and a positive electrode active material-containing layer 3 b as a composite layer provided on the surface of the positive electrode current collector 3 a. The positive electrode active material-containing layer 3 b is supported on the main surface of the positive electrode current collector 3 a.

[0069] The positive electrode current collector 3a also includes a portion on its surface where the positive electrode active material-containing layer 3b is not provided. This portion functions, for example, as a positive electrode current collector tab 3c. In the illustrated example, the positive electrode current collector tab 3c is a narrow portion that is narrower than the positive electrode active material-containing layer 3b. The width of the positive electrode current collector tab 3c may be narrower than the width of the positive electrode active material-containing layer 3b, or may be the same as the width of the positive electrode active material-containing layer 3b. Instead of the positive electrode current collector tab 3c that is part of the positive electrode current collector 3a, a separate conductive member may be electrically connected to the positive electrode 3 and used as an electrode current collector tab (positive electrode current collector tab).

[0070] In the electrode of the embodiment, the active material composition, the curve of each m / z value by the thermal evolved gas-mass spectrometry, the alkali component, the breaking strength, the average particle diameter, the ratio D ９０ / D １０ The respective measurement methods are explained below.

[0071] If the electrode to be measured is incorporated into a battery, the electrode to be used as the measurement sample is removed from the battery as follows: The battery is discharged, disassembled in an argon atmosphere glove box, and the electrode is removed. The electrode is washed with ethyl methyl carbonate and then vacuum dried. This gives the measurement sample.

[0072] (Confirmation of Active Material Composition) The composition of the active material can be confirmed by measuring the surface of the electrode by X-ray fluorescence (XRF).

[0073] (Evolved Gas Analysis-Mass Spectrometry Measurement) Measurement of electrodes by evolved gas analysis-mass spectrometry (EGA-MS) is carried out as follows.

[0074] The sample used is a composite layer scraped off from the electrode. Specifically, approximately 10 mg of the composite layer is scraped off from the electrode. The measurement equipment used is a combination of a Frontier Labs Multi-Shot Pyrolyzer (EGA / PY-3030D) and an Agilent Technologies Gas Chromatography Mass Spectrometer 7890A / 5975C. The sample scraped off from the electrode is placed in a sample cup and EGA-MS measurement is performed. The measurement atmosphere is not particularly limited as long as it is a non-oxidizing atmosphere. For example, an inert gas atmosphere such as helium, argon, or nitrogen can be used. EGA-MS measurement is performed in the temperature range of 40°C to 600°C at a heating rate of 10°C / min.

[0075] The resulting EGA thermogram is analyzed, and the curves at m / z=44 and m / z=132, which are respectively attributed to carbon dioxide and trifluorobenzene, are separated. The peak with the highest intensity in the m / z=132 curve is analyzed, and the peak top intensity I TOP and the average value of the peak intensities before and after it, I AVE Find the ratio I AVE / I TOP The area under the curve for m / z=132 in the range of 200°C to 550°C is calculated as follows: 132 and the area A under the curve for m / z=44 in the range of 550°C to 600°C44 Find the ratio A 44 / A 132 Calculate.

[0076] (Confirmation of Alkaline Component) Whether or not lithium carbonate (Li2CO3) is contained in the alkaline component is confirmed by the following method. In addition, a composite layer cut out from an electrode is used as a sample. Specifically, a sample cut out from an area of ​​500 cm2 from the electrode is used. 2 The mass of the active material in the mixture layer as a sample is 500 cm2. 2 and the weight of the composite layer (g / m 2 ) can be obtained from

[0077] The equipment used was an AGK-type CO2 Simple Precision Meter manufactured by Tsutsui Scientific Instruments Co., Ltd. Approximately 50 ml of water was added to the sample cut from the electrode using the above method, followed by neutralization with a solution of 1 part sulfuric acid and 5 parts water by volume, and then a small excess was added. The sample was then boiled to separate the CO2 and water vapor. When the sample was absorbed into a BaCl2 aqueous solution containing a known amount of NaOH, the reaction shown in Equation (2) below occurred.

[0078]

[0079] Next, as shown in the following reaction formula (3), the remaining NaOH is quantified by neutralization titration, and the consumed NaOH is converted to Li2CO3.

[0080]

[0081] Whether or not lithium hydroxide (LiOH) is contained in the alkaline component is confirmed by the following method.

[0082] 50 ml of water was added to 10 g of the sample cut from the electrode using the above method, and the mixture was stirred for 1 hour using a magnetic stirrer. After filtration, 15 ml of the filtrate was collected using a pipette, and 20 ml of a 1% barium chloride solution was added. While measuring the pH, the mixture was titrated with 0.05 mol / L hydrochloric acid until the pH became less than 8.4, and the titration amount was converted to LiOH.

[0083] (Measurement of the content of alkaline components in the active material) 2A sample of the mixture layer is cut out. The sample is added to water and stirred for 10 minutes. After that, the lithium compound present in the water is considered to be the alkaline component in the active material. The pH is then titrated with an acid to determine the mass of the alkaline component, and the mass ratio (mass %) to the active material is calculated. The mass of the active material in the mixture layer is calculated based on the mass of the active material in an area of ​​500 cm of the mixture layer. 2 and the weight of the composite layer (g / m 2 The type of alkaline component is determined by the above method.

[0084] (Method for measuring breaking strength) The electrode is immersed in an N-methyl-2-pyrrolidone solution and stirred to peel the composite layer from the current collector. From this peeled composite layer, particles of 2 μm to 6 μm in size are selected and, using a Shimadzu Micro Compression Tester MCT-510, a very small amount is spread on a pressure plate and compressed one particle at a time. The breaking strength is calculated using the following formula.

[0085] Cs = 2.8P / πd 2 Here, Cs is the breaking strength (numerical unit: N / mm ２ , or MPa), P indicates the test force (numerical unit: N), and d indicates the particle diameter (numerical unit: mm). Whether the composite layer components having a size of 2 μm to 6 μm are lithium nickel cobalt manganese-containing oxides can be confirmed by performing elemental analysis such as inductively coupled plasma (ICP) emission spectroscopy on the sample.

[0086] (Method for Measuring Average Particle Diameter) The particle size distribution of an electrode can be measured by the laser diffraction / scattering method described below. After washing and drying an electrode using the method described above, the active material-containing layer is separated from the current collector using, for example, a spatula, to obtain a powdered electrode composite sample containing active material particles. The powdered sample is then placed in a measurement cell filled with N-methylpyrrolidone (NMP) until a measurable concentration is reached. Note that the capacity and measurable concentration of the measurement cell vary depending on the particle size distribution measurement device. Ultrasonic waves are irradiated onto the measurement cell containing NMP and the electrode composite sample dissolved therein for 5 minutes. The ultrasonic output is, for example, within the range of 35 W to 45 W. For example, when approximately 50 ml of NMP is used as the solvent, ultrasonic waves at an output of approximately 40 W are irradiated onto the solvent containing the measurement sample for 300 seconds. Such ultrasonic irradiation can break down the agglomerations between the conductive agent particles and the active material particles. The measurement cell is then inserted into a particle size distribution measurement device using the laser diffraction / scattering method, and the particle size distribution is measured. Examples of particle size distribution measuring devices include Microtrac 3100 and Microtrac 3000II (both manufactured by Microtrac Bell Co., Ltd.), or devices having equivalent functions. In this way, the particle size distribution of the electrode can be obtained.

[0087] (ratio D ９０ / D １０ The particle size distribution obtained by the above method is a cumulative frequency distribution on a volume basis, accumulating in order from the smallest particle size side. In the particle size distribution, the particle diameter D at which the cumulative frequency on a volume basis from the smallest particle diameter side is 10% is １０ and the particle diameter D at which the cumulative frequency on a volume basis from the small particle diameter side becomes 90%. ９０ From the obtained value, the ratio D ９０ / D １０ Calculate.

[0088] The electrode of the first embodiment includes an active material containing an active material containing a lithium-nickel-cobalt-manganese-containing oxide, a conductive agent, and a binder. The above-mentioned ratio I of the electrode is determined by evolved gas-mass spectrometry (EGA-MS). AVE / I TOP is 0.2 or more and less than 0.5, and the above-mentioned area ratio A44 / A 132 is 5 or more and less than 10. According to the electrode of the first embodiment, a battery having excellent life performance can be provided.

[0089] (Second Embodiment) According to a second embodiment, a battery is provided. The battery includes a positive electrode, a negative electrode, and an electrolyte. At least one of the positive electrode and the negative electrode includes the electrode according to the first embodiment. The battery may further include a separator. The positive electrode, the negative electrode, and the separator may constitute an electrode group. The electrolyte may be held in the electrode group. The battery may also include an exterior member that houses the electrode group and the electrolyte. Furthermore, the battery may further include a positive electrode terminal electrically connected to the positive electrode and a negative electrode terminal electrically connected to the negative electrode. At least a portion of the positive electrode terminal and at least a portion of the negative electrode terminal may extend outside the exterior member.

[0090] Such a battery may be, for example, a lithium ion secondary battery. The battery also includes, for example, a non-aqueous electrolyte battery that contains a non-aqueous electrolyte as the electrolyte.

[0091] The negative electrode, positive electrode, electrolyte, separator, exterior member, positive electrode terminal, and negative electrode terminal will be described in detail below. The following example is an example in which the electrode of the first embodiment is applied to a positive electrode.

[0092] (1) Positive Electrode The positive electrode includes a positive electrode current collector and a positive electrode active material-containing layer (positive electrode mixture layer) supported on one surface or both surfaces of the positive electrode current collector and containing a positive electrode active material, a conductive agent, and a binder.

[0093] The positive electrode may be the electrode according to the first embodiment. In the form of the positive electrode, the positive electrode current collector, the positive electrode active material, and the positive electrode active material-containing layer of the positive electrode correspond to the current collector, the active material material, and the composite layer of the electrode according to the first embodiment, respectively. The electrode according to the first embodiment has been described above, so a description of the positive electrode here will be omitted.

[0094] (2) Negative Electrode The negative electrode includes a negative electrode current collector and a negative electrode active material-containing layer (negative electrode mixture layer) that is supported on one side or both sides of the negative electrode current collector and contains a negative electrode active material. The negative electrode active material-containing layer can contain a conductive agent and a binder in addition to the negative electrode active material.

[0095] The negative electrode active material, the conductive agent, the binder, and the negative electrode current collector will be described below.

[0096] Examples of the negative electrode active material include titanium-containing oxides, carbonaceous materials, and metal compounds. The type of the negative electrode active material may be one or more.

[0097] Examples of titanium-containing oxides include titanium dioxide, lithium titanium oxide, metal composite oxides containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, and Fe, and niobium titanium oxide. Examples of lithium titanium oxides include lithium titanium oxides having a spinel-type crystal structure, ramsdellite-type Li ２＋ｘ Ti ３ O ７ (x varies in the range of -1≦x≦3 depending on the charge / discharge reaction). Examples of metal composite oxides containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, and Fe include TiO ２ -P ２ O ５ , TiO ２ -V ２ O ５ , TiO ２ -P ２ O ５ -SnO ２ , TiO ２ -P ２ O ５ -MO (wherein M is at least one element selected from the group consisting of Cu, Ni, and Fe). Examples of niobium titanium oxides include those represented by the general formula Li ｍ Ti １－ｎ M3 ｎ Nb ２－ｌ M4 ｌ O ７＋σ (M3 is at least one element selected from the group consisting of Zr, Si, Sn, Fe, Co, Mn, and Ni, and M4 is at least one element selected from the group consisting of V, Nb, Ta, Mo, W, and Bi, and 0≦m≦5, 0≦n<1, 0≦l<2, −0.3≦σ≦0.3) and a niobium titanium oxide having a monoclinic crystal structure, and Ti２ Nb １０ O １９ The above metal composite oxides contain lithium when lithium is inserted by charging.

[0098] The titanium-containing oxide preferably includes lithium titanium oxide. An electrode including a titanium-containing oxide such as lithium titanium oxide has a potential of 0.4 V (vs. Li / Li) relative to the oxidation-reduction potential of lithium. ＋ ) or more. Therefore, even when input and output of a large current is repeated, deposition of metallic lithium on the electrode surface can be prevented. Furthermore, lithium titanium oxide has a lower input resistance than niobium titanium oxide. Furthermore, since the reaction potential based on Li is higher (on the noble side) than niobium titanium oxide, side reactions with the electrolyte are less likely to occur, and the rate of increase in resistance tends to be low. It is particularly preferable that the lithium titanium oxide contains lithium titanium oxide having a spinel-type crystal structure. Specific examples of such spinel-type lithium titanium oxide include Li ４＋ａ Ti ５ O １２ The value of the subscript a varies within the range of 0≦a≦3 upon charge and discharge.

[0099] Examples of the carbonaceous material include natural graphite, artificial graphite, coke, vapor-grown carbon fiber, mesophase pitch-based carbon fiber, spherical carbon, and resin-baked carbon. More preferred carbonaceous materials include vapor-grown carbon fiber, mesophase pitch-based carbon fiber, and spherical carbon. The carbonaceous material is preferably a material having a (002) plane spacing d ００２ is preferably 0.34 nm or less.

[0100] The metal compound may be a metal sulfide or a metal nitride, such as titanium sulfide, e.g., TiS, molybdenum sulfide, e.g., MoS, and FeS, FeS, or Li. ｖ Iron sulfides such as FeS (0.9≦v≦1.2) can be used. Metal nitrides include lithium cobalt nitride (e.g., Lis Co t N, 0<s<4, 0<t<0.5) can be used.

[0101] The active material may be in the form of particles. Examples of active material particles include active material primary particles and active material secondary particles. Secondary particles are aggregates of primary particles.

[0102] The average particle size of the secondary particles (average secondary particle size) is preferably 1 μm or more and 100 μm or less. If the average particle size of the secondary particles is within this range, they are easy to handle in industrial production, and the mass and thickness of the coating film for producing an electrode can be made uniform. Furthermore, a decrease in the surface smoothness of the electrode can be prevented. The average particle size of the secondary particles is more preferably 2 μm or more and 30 μm or less.

[0103] The specific surface area of ​​the secondary particles measured by the BET method is 3 m ２ / g or more 50m ２ / g or less. ２ When the specific surface area is 50 m / g or more, it is possible to secure sufficient sites for insertion and desorption of lithium ions. ２ More preferably, the secondary particles have a specific surface area of ​​5 m / g or less as measured by the BET method. ２ / g or more 50m ２ / g or less.

[0104] The conductive agent can improve current collection performance and reduce contact resistance between the active material and the current collector. Examples of the conductive agent include carbonaceous materials such as acetylene black, carbon black, graphite, carbon nanofibers, and carbon nanotubes. These carbonaceous materials may be used alone or in combination.

[0105] The binder can have the function of binding the negative electrode active material particles, the conductive agent, and the current collector. Examples of the binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), carboxylic acid-modified PVdF, fluorine-based rubber, styrene-butadiene rubber, acrylic resin and its copolymer, polyacrylic acid, and polyacrylonitrile. One or more types of binders can be used.

[0106] The compounding ratios of the negative electrode active material, conductive agent, and binder are preferably in the ranges of 70% by mass or more and 97.5% by mass or less for the negative electrode active material, 2% by mass or more and 20% by mass or less for the conductive agent, and 0.5% by mass or more and 10% by mass or less for the binder. By setting the amount of conductive agent to 2% by mass or more, the current collection performance of the active material-containing layer can be improved, and excellent high-current performance and low-temperature performance can be expected. Furthermore, by setting the amount of binder to 0.5% by mass or more, sufficient binding between the active material-containing layer and the current collector can be expected, and excellent high-temperature storage performance can be expected. On the other hand, from the viewpoint of increasing capacity, the conductive agent is preferably 20% by mass or less and the binder is preferably 10% by mass or less.

[0107] When the negative electrode active material is a material capable of inserting and extracting lithium ions, the negative electrode current collector can be made of a material that is electrochemically stable at the lithium ion insertion and extraction potential of the negative electrode active material. The negative electrode current collector is preferably a metal foil made of at least one material selected from copper, nickel, stainless steel, and aluminum, or an alloy foil made of an aluminum alloy containing at least one element selected from Mg, Ti, Zn, Mn, Fe, Cu, and Si. The shape of the negative electrode current collector can vary depending on the application of the battery. The thickness of the current collector can be, for example, 20 μm or less, or 15 μm or less.

[0108] The negative electrode can be produced, for example, by the following method. First, a negative electrode active material, a binder, and, if necessary, a conductive agent are suspended in a commonly used solvent, such as N-methylpyrrolidone, to prepare a slurry for producing the negative electrode. The obtained slurry is applied to a negative electrode current collector. The applied slurry is dried, and the dried coating is pressed to obtain a negative electrode including a negative electrode current collector and a negative electrode active material-containing layer formed on the negative electrode current collector.

[0109] (3) Electrolyte Examples of the electrolyte include non-aqueous electrolytes, etc. Examples of the non-aqueous electrolyte include a liquid non-aqueous electrolyte (nonaqueous electrolyte solution) prepared by dissolving an electrolyte salt (solute) in a non-aqueous solvent, and a gel-like non-aqueous electrolyte obtained by combining a liquid non-aqueous electrolyte with a polymer material.

[0110] The electrolyte salt is, for example, lithium perchlorate (LiClO ４ ), lithium hexafluorophosphate (LiPF ６ ), lithium tetrafluoroborate (LiBF ４ ), lithium arsenic hexafluoride (LiAsF ６ ), lithium difluorophosphate (LiPO ２ F ２ ), lithium trifluoromethanesulfonate (LiCF ３ SO ３ ), lithium bistrifluoromethylsulfonylimide [LiN(CF ３ SO ２ ) ２ These electrolyte salts may be used alone or in combination of two or more.

[0111] The electrolyte salt is preferably dissolved in the non-aqueous solvent in a range of 0.5 mol / L to 2.5 mol / L.

[0112] Examples of non-aqueous solvents include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC); chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC); cyclic ethers such as tetrahydrofuran (THF) and 2-methyltetrahydrofuran (2MeTHF); and dimethoxyethane (dimethoxyethane). Examples of organic solvents include chain ethers such as γ-butyrolactone (DMFE); cyclic esters such as γ-butyrolactone (BL); chain esters such as methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate; acetonitrile (AN); and sulfolane (SL). These organic solvents can be used alone or in the form of a mixture of two or more kinds.

[0113] Examples of polymer materials used for the gel-like non-aqueous electrolyte include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

[0114] (4) Separator The separator may be disposed, for example, on at least one of the positive electrode and the negative electrode, or between the positive electrode and the negative electrode.

[0115] Examples of the separator include porous films containing polyethylene (PE), polypropylene (PP), cellulose, or polyvinylidene fluoride (PVdF), and synthetic resin nonwoven fabrics.

[0116] (5) Exterior Component The exterior component may be formed from a laminate film or may be a metal container. When a metal container is used, the lid may be integral with the container or may be a separate component. The thickness of the metal container is preferably 0.5 mm or less, more preferably 0.2 mm or less. Examples of the shape of the exterior component include flat, rectangular, cylindrical, coin, button, sheet, and laminated types. The exterior component may be for small batteries mounted in portable electronic devices, etc., as well as for large batteries mounted in two- or four-wheeled automobiles.

[0117] The thickness of the laminate film exterior component is preferably 0.2 mm or less. Examples of laminate films include multilayer films containing a resin film and a metal layer disposed between the resin films. The metal layer is preferably aluminum foil or aluminum alloy foil for weight reduction. Polymer materials such as polypropylene (PP), polyethylene (PE), nylon, and polyethylene terephthalate (PET) can be used for the resin film. The laminate film can be sealed by heat fusion to form it into the shape of the exterior component.

[0118] The metal container is made of aluminum or an aluminum alloy. The aluminum alloy is preferably an alloy containing elements such as magnesium, zinc, and silicon. In aluminum or an aluminum alloy, the content of transition metals such as iron, copper, nickel, and chromium is preferably 100 ppm or less, in order to significantly improve long-term reliability and heat dissipation in a high-temperature environment.

[0119] The metal container made of aluminum or an aluminum alloy desirably has an average crystal grain size of 50 μm or less, more preferably 30 μm or less, and even more preferably 5 μm or less. By setting the average crystal grain size to 50 μm or less, the strength of the metal container made of aluminum or an aluminum alloy can be dramatically increased, allowing the container to be made even thinner. As a result, a lightweight, high-power, and highly reliable battery suitable for use in vehicles can be realized.

[0120] An example of such a battery will be described with reference to Figures 4 and 5. The flat-type battery shown in Figure 4 includes a flat wound electrode group 1, an exterior member 2, a positive electrode terminal 7, a negative electrode terminal 6, and an electrolyte (not shown). The exterior member 2 is a bag-shaped exterior member made of a laminate film. The wound electrode group 1 is housed in the exterior member 2. As shown in Figure 5, the wound electrode group 1 includes a positive electrode 3, a negative electrode 4, and a separator 5, and is formed by spirally winding a laminate obtained by stacking the negative electrode 4, separator 5, positive electrode 3, and separator 5 in this order from the outside in, and then press-molding the laminate.

[0121] The positive electrode 3 includes a positive electrode current collector 3a and a positive electrode active material-containing layer 3b. The positive electrode active material-containing layer 3b contains a positive electrode active material. The positive electrode active material-containing layer 3b is formed on both sides of the positive electrode current collector 3a. The negative electrode 4 includes a negative electrode current collector 4a and a negative electrode active material-containing layer 4b. The negative electrode active material-containing layer 4b contains a negative electrode active material. In the outermost portion of the negative electrode 4, the negative electrode active material-containing layer 4b is formed only on one side of the inner surface of the negative electrode current collector 4a. In the other portions of the negative electrode 4, the negative electrode active material-containing layer 4b is formed on both sides of the negative electrode current collector 4a.

[0122] As shown in Fig. 4, a positive electrode terminal 7 is electrically connected to the positive electrode 3 near the outer peripheral end of the wound electrode pack 1. In addition, a negative electrode terminal 6 is electrically connected to the negative electrode 4 in the outermost layer portion. The positive electrode terminal 7 and the negative electrode terminal 6 extend to the outside through openings in the exterior member 2.

[0123] Such a battery is not limited to the configuration shown in FIGS. 4 and 5, but may have a configuration shown in FIG. 6, for example.

[0124] In the prismatic battery shown in Fig. 6, a wound electrode group 11 is housed in a metal rectangular cylindrical container 12 with a bottom, which serves as an exterior member. A rectangular lid 13 is welded to the opening of the container 12. The flat wound electrode group 11 may have a configuration similar to that of the wound electrode group 1 described with reference to Figs. 4 and 5, for example.

[0125] One end of the negative electrode tab 14 is electrically connected to the negative electrode current collector, and the other end is electrically connected to a negative electrode terminal 15. The negative electrode terminal 15 is fixed to the rectangular lid 13 by a hermetic seal with a glass material 16 interposed therebetween. One end of the positive electrode tab 17 is electrically connected to the positive electrode current collector, and the other end is electrically connected to a positive electrode terminal 18 fixed to the rectangular lid 13.

[0126] The negative electrode tab 14 is made of a material such as aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, Si, etc. The negative electrode tab 14 is preferably made of the same material as the negative electrode current collector in order to reduce contact resistance with the negative electrode current collector.

[0127] The positive electrode tab 17 is made of a material such as aluminum or an aluminum alloy containing elements such as Mg, Ti, Zn, Mn, Fe, Cu, Si, etc. The positive electrode tab 17 is preferably made of the same material as the positive electrode current collector in order to reduce contact resistance with the positive electrode current collector.

[0128] The battery shown in the figure uses a wound electrode group in which the separator is wound together with the positive and negative electrodes, but a stacked electrode group in which the separator is folded zigzag and the positive and negative electrodes are alternately arranged at the folded points may also be used.

[0129] The battery of the second embodiment described above includes the electrode of the first embodiment as at least one of the positive and negative electrodes. Therefore, the battery of the second embodiment has excellent life performance. (Third Embodiment) According to the third embodiment, a battery pack is provided. This battery pack includes the electrode of the first embodiment or the battery of the second embodiment.

[0130] The battery pack according to the third embodiment may include one or more batteries (single cells) according to the second embodiment described above. The batteries included in the battery pack may be electrically connected in series or parallel to each other to form a battery assembly. The battery pack may include a plurality of battery assemblies.

[0131] Next, an example of a battery pack according to a third embodiment will be described with reference to the drawings.

[0132] Fig. 7 is an exploded perspective view of an example battery pack according to an embodiment, and Fig. 8 is a block diagram showing an electrical circuit of the battery pack of Fig. 7.

[0133] 7 and 8 includes a plurality of unit cells 21. The unit cells 21 may be flat type batteries, which are an example of the embodiment described with reference to FIG.

[0134] The plurality of cells 21 are stacked so that the negative electrode terminals 51 and positive electrode terminals 61 extending outward are aligned in the same direction, and are fastened together with adhesive tape 22 to form a battery pack 23. These cells 21 are electrically connected in series with each other as shown in FIG.

[0135] The printed wiring board 24 is disposed opposite the side surface from which the negative electrode terminal 51 and the positive electrode terminal 61 of the cell 21 extend. As shown in Fig. 8, the printed wiring board 24 is mounted with a thermistor 25, a protection circuit 26, and a terminal 27 for supplying current to an external device. An insulating plate (not shown) is attached to the surface of the printed wiring board 24 facing the assembled battery 23 to prevent unnecessary connection with the wiring of the assembled battery 23.

[0136] The positive electrode lead 28 is connected to a positive electrode terminal 61 located on the bottom layer of the battery pack 23, and its tip is inserted into and electrically connected to a positive electrode connector 29 on the printed wiring board 24. The negative electrode lead 30 is connected to a negative electrode terminal 51 located on the top layer of the battery pack 23, and its tip is inserted into and electrically connected to a negative electrode connector 31 on the printed wiring board 24. These connectors 29 and 31 are connected to the protection circuit 26 via wires 32 and 33 formed on the printed wiring board 24.

[0137] The thermistor 25 detects the temperature of the cell 21 and transmits the detection signal to the protection circuit 26. The protection circuit 26 can interrupt the positive wiring 34a and the negative wiring 34b between the protection circuit 26 and the terminal 27 for supplying power to the external device under predetermined conditions. An example of the predetermined condition is when the temperature detected by the thermistor 25 exceeds a predetermined temperature. Another example of the predetermined condition is when overcharge, overdischarge, overcurrent, or the like of a cell 21 is detected. This overcharge detection is performed for each cell 21 or the entire battery pack 23. When detecting an individual cell 21, the battery voltage may be detected, or the positive electrode potential or negative electrode potential may be detected. In the latter case, a lithium electrode used as a reference electrode is inserted into each cell 21. In the battery pack 20 shown in FIGS. 7 and 8, wiring 35 for voltage detection is connected to each cell 21. A detection signal is transmitted to the protection circuit 26 via these wiring 35.

[0138] Protective sheets 36 made of rubber or resin are disposed on the three sides of the battery pack 23 excluding the sides from which the positive electrode terminal 61 and the negative electrode terminal 51 protrude.

[0139] The battery pack 23 is housed in a storage container 37 together with the protective sheets 36 and the printed wiring board 24. That is, the protective sheets 36 are disposed on both inner surfaces along the long sides and the inner surface along the short sides of the storage container 37, and the printed wiring board 24 is disposed on the inner surface on the opposite side along the short sides. The battery pack 23 is located in a space surrounded by the protective sheets 36 and the printed wiring board 24. A lid 38 is attached to the top surface of the storage container 37.

[0140] Heat-shrinkable tape may be used to secure the battery pack 23 instead of the adhesive tape 22. In this case, protective sheets are placed on both sides of the battery pack, and the heat-shrinkable tape is wrapped around the battery pack, and then the heat-shrinkable tape is thermally shrunk to bind the battery pack.

[0141] 7 and 8 show the cells 21 connected in series, they may be connected in parallel to increase the battery capacity. Furthermore, assembled battery packs may be connected in series and / or in parallel.

[0142] The configuration of the battery pack may be changed as appropriate depending on the application. The battery pack is preferably used in applications where good cycle performance is desired when a large current is drawn. Specific applications include power sources for digital cameras and in-vehicle applications such as two- to four-wheel hybrid electric vehicles, two- to four-wheel electric vehicles, and power-assisted bicycles. The battery pack is particularly suitable for in-vehicle applications.

[0143] The battery pack according to the third embodiment includes the electrode according to the first embodiment or the battery according to the second embodiment, and therefore, the battery pack can exhibit excellent life performance.

[0144] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the examples listed below as long as it does not deviate from the gist of the invention. (Example 1) <Preparation of Positive Electrode> A positive electrode active material was prepared using a lithium nickel cobalt manganese oxide (LiNi) containing 0.5% by mass of an alkaline component. 0.8 Co 0.1 Mn 0.1 The alkaline component contained Li2CO3 and LiOH. ５０ , and D ９０ / D １０ was measured by the method described above, and the results are shown in Table 1.

[0145] Carbon black (CB) was also prepared as a conductive agent. Polyvinylidene fluoride (PVdF) and a dispersant were also prepared as a binder. A polymer containing a nitrile group-containing monomer unit and an alkylene structural unit was prepared by hydrogenating a precursor obtained by copolymerizing acrylonitrile and 1,3-butadiene as a dispersant. Next, the CB was dispersed in n-methylpyrrolidone (NMP), and the prepared dispersant was added and further dispersed to obtain a CB dispersion. At this time, the CB was added at a ratio of 5% by mass relative to the positive electrode composite layer (positive electrode active material-containing layer) to be prepared, and the dispersant was added at a ratio of 5% by mass relative to the CB. Next, PVdF was added and dispersed in the CB dispersion, and then the positive electrode active material was added and dispersed to prepare a slurry. At this time, PVdF was added at a ratio of 2% by mass relative to the positive electrode composite layer (positive electrode active material-containing layer) to be prepared. The obtained slurry was applied to an aluminum foil having a thickness of 12 μm in an amount of 80 g / m per unit area. 2 The coated layer was then dried so that the coating weight was 80 g / m. The dried coating was then pressed. 2 and the density is 3.3 g / cm 3 A positive electrode was fabricated.

[0146] <Preparation of negative electrode> As a negative electrode active material, lithium titanium oxide (Li4Ti5O 12 ) was prepared. Graphite was also prepared as a conductive agent. PVdF was then prepared as a binder. Next, the negative electrode active material, carbon black, and PVdF were mixed to obtain a mixture. In this case, the carbon black was added so that it accounted for 4 mass % of the negative electrode composite layer (negative electrode active material-containing layer) to be prepared. PVdF was added so that it accounted for 2 mass % of the negative electrode composite layer (negative electrode active material-containing layer) to be prepared. Next, the obtained mixture was mixed in an N-methylpyrrolidone (NMP) solution to prepare a slurry. The obtained slurry was applied to a current collector made of aluminum foil with a thickness of 12 μm in an amount of 101 g / m per unit area. ２The coated film was then applied and dried so that the coating weight was 100 g / m. The dried coating film was then pressed to form a negative electrode composite layer on the current collector. 2 and the density is 2.1 g / cm 3 A strip-shaped negative electrode was prepared.

[0147] <Preparation of Non-Aqueous Electrolyte> A liquid non-aqueous electrolyte consisting of 14% by volume of LiPF6, 33% by volume of propylene carbonate (PC), and 53% by volume of diethyl carbonate (DEC) was prepared.

[0148] <Preparation of Electrode Assembly> The separator was folded zigzag, and positive and negative electrodes were alternately arranged at the folded portions to prepare a laminated electrode assembly. The obtained electrode assembly was placed in a pack (exterior member) made of a 0.1 mm thick laminate film and vacuum dried at 95°C for 10 hours.

[0149] <Preparation of Nonaqueous Electrolyte Battery> A liquid nonaqueous electrolyte was poured into the laminate film pack containing the electrode group, and the pack was then completely sealed by heat sealing to prepare a nonaqueous electrolyte battery with a rated capacity of 1 Ah.

[0150] Example 2 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that the amount of the dispersant added was changed to 3 mass % relative to the CB.

[0151] Example 3 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that the amount of the dispersant added was changed to 10% by mass relative to CB.

[0152] Example 4 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that a lithium-nickel-cobalt-manganese-containing oxide containing 0.4 mass % of residual alkaline components was used instead as the positive electrode active material.

[0153] Example 5 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that a lithium-nickel-cobalt-manganese-containing oxide containing 1% by mass of residual alkaline components was used instead as the positive electrode active material.

[0154] Comparative Example 1 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that a positive electrode was fabricated by preparing a slurry without using a dispersant as described below.

[0155] As the positive electrode active material, lithium nickel cobalt manganese oxide (LiNi) containing an alkaline component at a ratio of 0.5 mass % was used. 0.8 Co 0.1 Mn 0.1 O2) was prepared. CB was also prepared as a conductive agent. PVdF was then prepared as a binder. Next, the positive electrode active material and CB were mixed to obtain a mixture. At this time, CB was added so that the ratio of CB was 5% by mass with respect to the positive electrode composite layer to be prepared. Next, the obtained mixture was dispersed in a mixed solvent of NMP and PVdF to prepare a slurry. At this time, PVdF was added so that the ratio of PVdF was 2% by mass with respect to the positive electrode composite layer to be prepared. Thereafter, the positive electrode preparation procedure was carried out in the same manner as in Example 1.

[0156] The negative electrode, the nonaqueous electrolyte, the electrode group, and the nonaqueous electrolyte battery were also fabricated in the same manner as in Example 1.

[0157] Comparative Example 2 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that the amount of the dispersant added was changed to 30% by mass relative to CB.

[0158] Comparative Example 3 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that a lithium-nickel-cobalt-manganese-containing oxide containing 0.3 mass % of residual alkaline components was used instead as the positive electrode active material.

[0159] Comparative Example 4 A nonaqueous electrolyte battery was fabricated in the same manner as in Example 1, except that a lithium-nickel-cobalt-manganese-containing oxide containing 1.2 mass% of residual alkaline components was used instead as the positive electrode active material.

[0160] The amount of alkaline component contained in the positive electrode active material for each of Examples 1 to 5 and Comparative Examples 1 to 4, the breaking strength of the positive electrode active material, and the average particle diameter D ５０ , D ９０ / D １０The amount of dispersant added to the slurry for preparing the positive electrode is shown in Table 1.

[0161]

[0162] The positive electrodes prepared in each example were measured by evolved gas mass spectrometry (EGA-MS). From the obtained spectrum, a curve derived from the component at m / z=132 and a curve derived from the component at m / z=44 were obtained, and the peak kurtosis (ratio I AVE / I TOP ) and the ratio A of the area on the high-temperature side of the m / z=44 curve to the area on the low-temperature side of the m / z=132 curve 44 / A 132 The nonaqueous electrolyte battery of each example was evaluated for life by the following method. The results are shown in Table 2.

[0163] The battery was charged and discharged at a charge rate of 3C and a discharge rate of 3C at an ambient temperature of 75°C within a range of SOC 0% to 100%. The battery was first charged to 100% SOC and then discharged to 0% SOC. This constituted one charge / discharge cycle, and the initial discharge capacity was measured. This charge / discharge cycle was repeated 300 times, and the discharge capacity after 300 cycles was measured. The discharge capacity after 300 cycles was then divided by the initial discharge capacity and multiplied by 100 to evaluate the capacity retention rate after 300 cycles as a percentage. The battery was then sealed in a vacuum-sealed container, and the laminate film pack was opened to measure the amount of gas that escaped.

[0164]

[0165] As is clear from Table 2, the nonaqueous electrolyte batteries of Examples 1 to 5 had better results in any of the life performance evaluations compared to the batteries of Comparative Examples 1 to 4. Specifically, the nonaqueous electrolyte batteries of Examples 1 to 5 had either a lower amount of gas generation, a higher capacity retention rate, or both.

[0166] In the m / z=132 curve measured by EGA-MS for the positive electrode prepared in Comparative Example 1, the ratio I AVE / I TOPA broad, most intense peak with a high value was obtained. This is because PVdF was mainly bound to CB by omitting the addition of a dispersant to the slurry for preparing the positive electrode, and the decomposition temperature of PVdF was lowered by catalytic action. The most intense peak at m / z=132 was shifted to the lower temperature side and became broad. Furthermore, the preferential binding of PVdF to CB resulted in less binding of PVdF to the active material, which was explained by the small value of the ratio A 44 / A 132 This is reflected in the following. Because the active material was covered with less PVdF, the amount of gas generated by the reaction between the electrolyte and the active material increased. CB aggregation caused uneven reactions in the positive electrode, leading to localized deterioration, and the expansion and contraction of the active material damaged the conductive path, resulting in a decrease in capacity retention.

[0167] In the m / z=132 curve measured for the positive electrode prepared in Comparative Example 2, the ratio I AVE / I TOP The peak intensity was low and a sharp maximum intensity peak was obtained. This indicates that the amount of dispersant was too large, which resulted in the CB being very well dispersed, resulting in little PVdF adhering to the CB. The large amount of dispersant, which is a resistance component, increased the resistance and reduced the capacity retention rate.

[0168] The ratio A obtained from the EGA-MS spectrum measured for the positive electrode prepared in Comparative Example 3 44 / A 132 The value of was small, indicating that there was little binding of PVdF to the active material. Because the amount of alkaline component in the positive electrode active material was small, it was difficult for the binder to bind, and the amount of gas generated by the reaction between the electrolyte and the active material increased. In addition, the conductive path in the positive electrode was damaged due to the expansion and contraction of the active material, resulting in a decrease in the capacity retention rate.

[0169] The ratio A obtained from the EGA-MS spectrum measured for the positive electrode prepared in Comparative Example 4 44 / A 132The value of was large. This indicates that the active material contained a large amount of alkaline components, which caused the cross-linking reaction of the binder to proceed excessively, resulting in excessive binding of PVdF to the active material. The excessive cross-linking reaction of the binder resulted in the excessive generation of hydrogen fluoride (HF), resulting in a large amount of gas generation. In addition, the active material was excessively covered with PVdF, which increased the resistance and reduced the capacity retention rate.

[0170] The following describes embodiments of the invention. <1> An active material containing an active material containing a lithium-nickel-cobalt-manganese-containing oxide, a conductive agent, and a binder, wherein the peak top intensity I of the most intense peak in the curve at m / z=132 measured by thermal evolved gas-mass spectrometry is TOP The average value I of the peak intensity at ±20 ° C from the peak top AVE Ratio of I AVE / I TOP is 0.2 or more and less than 0.5, and the area A under the curve of m / z=132 in the range of 200°C or more and 550°C or less 132 The area A under the curve of m / z=44 by thermal evolution gas-mass spectrometry in the range of 550°C to 600°C 44 Ratio A 44 / A 132 The electrode according to <2>, wherein the active material contains 0.4 mass % or more and 1 mass % or less of an alkaline component containing at least one of lithium carbonate and lithium hydroxide. <3> The lithium nickel cobalt manganese-containing oxide is Li a Ni (1-b-c-d) Co b Mn c M d<1> The electrode according to <1> or <2>, wherein the active material has a breaking strength of 30 MPa or more and 300 MPa or less. <6> The electrode according to <1> or <5>, wherein the active material has a particle shape, and the average particle diameter of the active material measured by a laser diffraction scattering method is 2 μm or more and 8 μm or less. <7> The electrode according to <1> or <5>, wherein the active material has a particle shape, and the average particle diameter of the active material measured by a laser diffraction scattering method is 2 μm or more and 8 μm or less. <8> The electrode according to <1> or <5>, wherein the active material has a particle shape, and the average particle diameter of the active material measured by a laser diffraction scattering method is 2 μm or more and 8 μm or less. <9> The electrode according to <1> or <2>, wherein the active material has a particle shape, and the average particle diameter of the active material measured by a laser diffraction scattering method is 2 μm or more and 8 μm or less. <10> The electrode according to <1> or <2>, wherein the active material has a particle shape, and the average particle diameter of the active material measured by a laser diffraction scattering method is 2 μm or more and 8 μm or less. <11> The electrode according to <1> or <2>, wherein the active material has a particle shape, and the average particle diameter of the active material measured by a laser diffraction scattering method is 2 μm or more and 8 μm or less. <12> The electrode according to <1> or <2>, wherein the active material has a particle shape, and the average particle diameter of the active material measured by a laser diffraction scattering method is 2 μm or more and 8 μm or less. <7> The active material has a particle shape, and a ratio D in a cumulative frequency distribution of particle diameters on a volume basis based on a particle size distribution by a laser diffraction scattering method of the active material ９０ / D １０ (where D １０ is the particle size at which the cumulative frequency from the small particle size side of the cumulative frequency distribution becomes 10%, and D ９０ <8> The electrode according to any one of <1> to <7>, wherein the particle diameter at which the cumulative frequency from the small particle diameter side of the cumulative frequency distribution is 90% (is a particle diameter at which the cumulative frequency distribution is 90%) is 4 or less. <9> The electrode according to any one of <1> to <7>, wherein the active material has a single particle shape. <10> 3.1 g / cm 3 3.5g / cm or more 3 The electrode according to any one of <1> to <8>, having the following density. <10> A battery comprising a positive electrode consisting of the electrode according to any one of <1> to <9>, and a negative electrode. <11> The battery according to <10>, in which the negative electrode contains a titanium-containing oxide. <12> The battery according to <11>, in which the titanium-containing oxide contains at least one selected from the group consisting of lithium titanium oxide having a spinel crystal structure, lithium titanium oxide having a ramsdellite crystal structure, niobium titanium oxide, and titanium dioxide. <13> The battery according to any one of <10> to <12>, further containing a non-aqueous electrolyte. <14> A battery pack comprising the battery according to any one of <10> to <13>.

[0171] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as defined in the claims.

[0172] DESCRIPTION OF SYMBOLS 1... Wound electrode group, 2... Exterior member, 3... Positive electrode, 3a... Positive electrode current collector, 3b... Positive electrode active material-containing layer, 3c... Positive electrode current collector tab, 4... Negative electrode, 4a... Negative electrode current collector, 4b... Negative electrode active material-containing layer, 5... Separator, 6... Negative electrode terminal, 7... Positive electrode terminal, 11... Wound electrode group, 12... Container, 13... Lid, 14... Negative electrode tab, 15... Negative electrode terminal, 16... Glass material, 17... Positive electrode tab, 18... Positive electrode terminal, 20... Battery pack, 21... Single cell , 22...adhesive tape, 23...battery pack, 24...printed wiring board, 25...thermistor, 26...protection circuit, 27...power-supply terminal, 28...positive electrode lead, 29...positive electrode connector, 30...negative electrode lead, 31...negative electrode connector, 32...wiring, 33...wiring, 34a...positive electrode wiring, 34b...negative electrode wiring, 35...wiring, 36...protective sheet, 37...storage container, 38...lid, 51...negative electrode terminal, 61...positive electrode terminal.

Claims

1. An active material containing an active material containing a lithium nickel cobalt manganese-containing oxide, a conductive agent, and a binder, wherein the peak top intensity I of the most intense peak in the curve of m / z=132 measured by thermal evolved gas-mass spectrometry TOP The average value I of the peak intensity at ±20 ° C from the peak top AVE Ratio of I AVE / I TOP is 0.2 or more and less than 0.5, and the area A under the curve of m / z=132 in the range of 200°C or more and 550°C or less 132 The area A under the curve of m / z=44 by thermal evolution gas-mass spectrometry in the range of 550°C to 600°C 44 Ratio A 44 / A 132 is 5 or more and less than 10.

2. The electrode according to claim 1, wherein the active material contains 0.4% by mass or more and 1% by mass or less of an alkaline component including at least one of lithium carbonate and lithium hydroxide.

3. The lithium nickel cobalt manganese-containing oxide is Li a Ni (1-b-c-d) Co b Mn c M d 2. The electrode of claim 1, wherein the electrode is represented by the formula: O2 (wherein 1≦a≦1.2, 0<b≦0.4, 0<c≦0.4, 0≦d≦0.1, and M is one or more elements selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Y, B, Mo, Nb, Zn, Sn, Zr, Ga, and V).

4. The electrode according to claim 1, wherein the binder comprises one or more selected from the group consisting of polyvinylidene fluoride and derivatives thereof.

5. The electrode according to claim 1, wherein the breaking strength of the active material is 30 MPa or more and 300 MPa or less.

6. The electrode according to claim 1, wherein the active material has a particulate shape and the average particle diameter of the active material measured by a laser diffraction scattering method is 2 μm or more and 8 μm or less.

7. The active material has a particle shape, and the ratio D in the cumulative frequency distribution of particle diameters on a volume basis based on the particle size distribution of the active material by a laser diffraction scattering method is ９０ / D １０ (where D １０ is the particle size at which the cumulative frequency from the small particle size side of the cumulative frequency distribution becomes 10%, and D ９０ 2. The electrode according to claim 1, wherein the particle size distribution (wherein the cumulative frequency from the small particle size side of the cumulative frequency distribution is 90%) is 4 or less.

8. The electrode of claim 1, wherein the active material has a single particle shape.

9. 3.1 g / cm 3 3.5g / cm or more 3 10. The electrode of claim 1 having a density:

10. A battery comprising a positive electrode made of the electrode according to any one of claims 1 to 9 and a negative electrode.

11. The battery of claim 10, wherein the negative electrode comprises a titanium-containing oxide.

12. The battery according to claim 11, wherein the titanium-containing oxide comprises at least one selected from the group consisting of lithium titanium oxide having a spinel crystal structure, lithium titanium oxide having a ramsdellite crystal structure, niobium titanium oxide, and titanium dioxide.

13. The battery of claim 10, further comprising a non-aqueous electrolyte.

14. A battery pack comprising the battery of claim 10.