Electrodes, batteries, and battery packs

Abstract

According to an embodiment, provided is an electrode comprising an active material-containing layer that contains active material. The active material comprises a lithium-nickel-cobalt-manganese composite oxide having an average primary particle diameter of 2 μm to 7 μm. A specific surface area SBET of the active material-containing layer as measured by the N2 gas adsorption method and a pore specific surface area SHg of the active material-containing layer as measured by the mercury porosimetry satisfy the relationship 0.8<SBET / SHg<2.0. The pore specific surface area SHg of the active material-containing layer and a pore volume VHg of the active material-containing layer as measured by mercury porosimetry satisfy the relationship 20 m2 / mL<SHg / VHg<60 m2 / mL.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION Embodiments of the present invention relate to electrodes, batteries, and battery packs. [Background technology]

[0002] Secondary batteries, including non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries, have been widely adopted and are used not only in electronic devices such as mobile phones but also in vehicles such as hybrid cars and electric cars. These applications require improved large capacity, long life, and output performance.

[0003] Graphite is generally used as the negative electrode active material for non-aqueous electrolyte batteries. Graphite forms LiC6 by Li insertion and exhibits a theoretical capacity of 372 mAh / g. Graphite also has a Li reaction potential (the potential at which the Li insertion-extraction reaction occurs) of 0.1 V (vs. Li / Li + ), so by using a graphite negative electrode, a battery with high output and high energy density can be obtained. On the other hand, because the Li insertion reaction potential of graphite is close to the Li deposition potential, lithium dendrites are easily deposited due to overvoltage, etc. Since the dendrites penetrate the separator, causing an internal short circuit, batteries using graphite negative electrodes have the disadvantage of low safety. In addition, graphite expands and contracts in the c-axis direction as Li insertion and desorption occur, which causes significant structural deterioration of the graphite. Other negative electrode active materials for non-aqueous electrolyte batteries include graphite with a potential of 0.5 V (vs. Li / Li) relative to the Li reaction potential. + ), such as spinel-type lithium titanate (Li4Ti5O 12 It is known that the use of a lithium-ion battery can suppress the precipitation of lithium dendrites, thereby avoiding the risks of short circuits, self-discharge, and fire, and enabling the production of batteries with excellent life performance.

[0004] Positive electrode active materials for nonaqueous electrolyte batteries include lithium nickel cobalt manganese oxide, which excels in high-capacity performance. Conventional batteries using lithium nickel cobalt manganese oxide for the positive electrode and lithium titanate for the negative electrode offer advantages such as rapid charge / discharge performance, long-life performance, and low-temperature performance compared to batteries using graphite-based negative electrodes. However, there is room for improvement in positive electrode active materials, particularly in terms of life performance. During charge / discharge cycles, lithium nickel cobalt manganese oxide particles in the positive electrode undergo particle cracking and irreversible changes to degraded structures such as rock salt structures. This leads to a decrease in capacity and an increase in electrical resistance with each cycle. Conventional lithium nickel cobalt manganese oxide is generally a polycrystalline system that forms secondary particles formed by agglomeration of fine primary particles, with a specific surface area of ​​approximately 2 m. 2 In the case of positive electrodes using such active materials, oxidation reactions between the positive electrode and the electrolyte are likely to occur, particularly during charging and discharging at high potentials, resulting in problems such as significant gas generation and increased resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2016 / 195036 [Patent Document 2] Japanese Patent Application Publication No. 2012-243463 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to provide an electrode that can realize a battery with excellent life performance, a battery including this electrode, and a battery pack including this battery. [Means for solving the problem]

[0007] According to an embodiment, an electrode is provided having an active material-containing layer containing an active material. The active material includes a lithium-nickel-cobalt-manganese composite oxide having an average primary particle size of 2 μm or more and 7 μm or less. The specific surface area S of the active material-containing layer measured by N2 gas adsorption method is BET and the pore specific surface area S of the active material-containing layer measured by mercury porosimetry Hg is 0.8 BET / S Hg The relationship of pore specific surface area S of the active material-containing layer is satisfied. Hg and the pore volume V of the active material-containing layer measured by mercury porosimetry Hg is 20 m 2 / mL Hg / V Hg <60 m 2 / mL. Pore volume V Hg teeth, 0.05 mL / g≦V Hg ≦0.09 mL / g is within the range. Specific surface area S BET is 2.5 m 2 / g≦S BET ≦2.8 m 2 / g.

[0008] According to another embodiment, a battery is provided comprising the above electrode and an electrolyte.

[0009] According to yet another embodiment, there is provided a battery pack including the above battery. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a plan view schematically illustrating an example of an electrode according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view of an example battery according to the embodiment cut in the thickness direction. [Figure 3] FIG. 3 is an enlarged cross-sectional view of part A in FIG. [Figure 4] FIG. 4 is a partially cutaway perspective view of another example of a battery according to the embodiment. [Figure 5] ​​FIG. 5 is an exploded perspective view of an example battery pack according to the embodiment. [Figure 6] FIG. 6 is a block diagram showing the electrical circuit of the battery pack shown in FIG. Embodiment

[0011] One of the conventional methods for improving output performance is to increase electrode density. If the electrode density is too low, contact between the active materials or between the active materials and the conductive agent will be poor, causing a deterioration in input / output performance. On the other hand, if the positive electrode density is too high, it will be difficult for the electrolyte (liquid electrolyte) to penetrate, resulting in a deterioration in input / output performance.

[0012] In conventional lithium-ion rechargeable battery positive electrodes obtained using lithium-containing metal composites as the positive electrode active material, the particles of the positive electrode active material tend to crack when pressurized to increase the electrode density or during repeated charge / discharge cycles. This increases the surface area of ​​the positive electrode, leading to increased side reactions, resulting in increased resistance and significant gas generation. To prevent particle cracking, the secondary particle size and shape are controlled. However, a large positive electrode surface area increases side reactions, leading to increased electrical resistance, while a small surface area hinders the diffusion of lithium ions, resulting in concerns about a decrease in capacity retention.

[0013] One method for increasing capacity is to use lithium nickel-cobalt manganese oxide (NCM), which has a high Ni content and a high capacity per weight. Such high-nickel NCM positive electrodes are prone to side reactions on the active material surface, resulting in the aforementioned deterioration. Attempts to achieve both high capacity and high output have been made by increasing the average particle size of the high-nickel NCM to reduce its specific surface area and using it in combination with an active material with a low Ni content and low reactivity, lithium nickel-cobalt manganese oxide, which has a small average particle size and a large specific surface area. However, this configuration does not fundamentally solve the problem of active material deterioration.

[0014] Hereinafter, embodiments will be described with reference to the drawings. Note that common components throughout the embodiments will be denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0015] Furthermore, each figure is a schematic diagram intended to facilitate explanation and understanding of the embodiment, and the shape, dimensions, ratios, etc. may differ from those of the actual device, but these can be appropriately modified in design by taking into consideration the following explanation and known technology.

[0016] (First embodiment) According to a first embodiment, an electrode is provided. The electrode includes an active material-containing layer containing an active material. The active material includes a lithium nickel cobalt manganese composite oxide having an average primary particle size of 2 μm or more and 7 μm or less. The specific surface area S of the active material-containing layer is determined by N2 gas adsorption method. BET and the pore specific surface area S obtained by mercury porosimetry Hg That is, 0.8 BET / S Hg <2.0. In addition, the pore specific surface area S Hg and the pore volume V obtained by mercury intrusion porosimetry Hg That is, 20 m 2 / mL Hg / V Hg <60 m 2 / mL relationship is satisfied.

[0017] The electrode according to the embodiment may be a battery electrode. Examples of batteries that may include such an electrode include secondary batteries such as lithium ion secondary batteries. Secondary batteries include non-aqueous electrolyte secondary batteries that include a non-aqueous electrolyte. The electrode may be, for example, a positive electrode for the battery.

[0018] ​​An electrode that satisfies the above-mentioned configuration is an electrode that uses a single-crystal lithium-nickel-cobalt-manganese composite oxide (NCM). Compared to a positive electrode that uses a secondary-particle-type NCM, whose surface structure and surface area vary depending on how the primary particles aggregate, this electrode has fewer micropores and a more uniform surface condition. Therefore, the specific surface area obtained by the N2 gas adsorption method and the mercury intrusion method is approximately the same. Furthermore, when comparing the pore volume obtained by the mercury intrusion method between the single-crystal type and the secondary-particle type, the value is smaller for the single-crystal type, which has fewer pores. The specific surface area S obtained by the N2 gas adsorption method (based on the BET (Brunauer, Emmett, Teller) method, as described below) BET and the pore specific surface area S obtained by mercury porosimetry Hg The ratio S BET / S Hg The closer the value of S is to 1.0, the better the life performance of the single crystal NCM. Hg The pore volume V obtained by mercury porosimetry Hg The value S divided by Hg / V Hg By keeping the surface area within a specific range, it is possible to optimize the contact area between the electrolyte and the electrode, which allows for both electrolyte penetration and suppression of side reactions. Compared to secondary particle NCMs, single crystal NCMs have fewer micropores and a more uniform surface condition, so S BET / S Hg is close to 1.0, and the pore volume is small, so S Hg / V Hg The specific surface area of ​​single-crystal NCM is constant regardless of the measurement method, so by controlling the electrode density using this as the active material, it is possible to control the contact area with the electrolyte and improve battery performance.

[0019] Such an electrode may include a current collector. The current collector may have, for example, a foil, strip, or plate shape. An active material-containing layer (electrode mixture layer) may be provided on at least one main surface of the current collector. That is, the current collector may carry an active material-containing layer on one surface or on both surfaces. The current collector may include a portion on its surface that does not carry an active material-containing layer. This portion may function as a current collecting tab. Alternatively, the electrode may include a current collecting tab that is separate from the current collector.

[0020] The specific surface area S of the active material-containing layer measured by N2 gas adsorption method BET and the pore specific surface area S measured by mercury porosimetry Hg Relative to S BET / S Hg is 0.8 BET / S Hg Within the range of <2.0, the effective area contributing to the electrode reaction can be accurately controlled, and electrical resistance can be reduced, suppressing gas generation. The specific surface area S of the active material-containing layer measured by the N2 gas adsorption method BET The specific surface area of ​​the electrode mainly reflects the specific surface area of ​​micropores and mesopores with diameters on the scale of 0.1 nm to 100 nm. In contrast, the specific surface area of ​​the pores, S Hg The specific surface area of ​​mesopores and macropores, which have pore diameters on the scale of 1 nm to 1 mm, is mainly reflected in the active material-containing layer. BET / S Hg is an index that represents the ratio of micropores to macropores in the electrode. BET / S Hg Or S BET / S Hg If the specific surface area is greater than 2.0, there may be many micropores or macropores. In this case, it is difficult to control the effective area that contributes to the side reaction between the active material and the electrolyte (liquid electrolyte), and the reaction area becomes large, resulting in a large increase in electrical resistance. More preferably, the specific surface area S BET and the pore specific surface area S Hg The ratio is 0.85 BET / S Hg ​​It is desirable to satisfy the relationship <1.15. With electrodes where the difference in specific surface area is smaller than 15%, the electrode reaction area is more controlled, and the effect of reducing electrical resistance is more pronounced.

[0021] The pore specific surface area S of the active material-containing layer measured by mercury porosimetry Hg (unit: m 2 / g) and the pore volume V measured by mercury intrusion porosimetry Hg (unit: mL / g) is 20 m 2 / mL Hg / V Hg <60 m 2 By keeping the concentration within the range of 20 m / mL, an electrode with little capacity loss can be obtained. 2 / mL≧S Hg / V Hg In the case of S, the area that contributes to the side reaction between the active material and the electrolyte in the active material-containing layer is large. This promotes the diffusion of lithium ions within the electrode, improving the capacity retention rate. However, this also increases the resistance component associated with the side reaction, resulting in an increase in electrical resistance. Hg / V Hg ≧60 m 2 When the ratio is 20 m / mL, the contact area between the electrode active material and the electrolyte is small and the permeability of the electrolyte into the electrode is reduced, which makes the electrode reaction more likely to be non-uniform and reduces the capacity retention rate. 2 / mL Hg / V Hg <60 m 2 By setting the concentration in the range of 40 m / mL, the reaction area and permeability between the active material and the electrolyte are appropriate, and a battery with excellent life performance can be produced. 2 / mL Hg / V Hg <50 m 2 / mL, it is desirable that the range be such that both the effect of improving the capacity retention rate and the effect of suppressing the increase in resistance can be obtained at a higher level.

[0022] ​​​In the active material-containing layer, by setting the primary particle diameter of the active material particles (including at least particles of lithium nickel cobalt manganese composite oxide) to 2 μm or more and 7 μm or less, it is possible to easily control the electrode surface area and improve the battery life performance. If the primary particle diameter is less than 2 μm, the specific surface area of ​​the electrode increases, and the side reaction between the electrode and the electrolyte has a greater impact on the life performance. Furthermore, if the average particle diameter exceeds 7 μm, a lithium ion concentration gradient occurs within the particle, leading to local structural deterioration and ultimately to a decrease in life performance. It is more preferable to set the primary particle diameter to 3 μm or more and 4.5 μm or less. Within this more preferred range, aggregation and isolation of the primary particles can be prevented, thereby further improving the life performance.

[0023] The active material-containing layer contains, as an active material, a compound of the formula Li a Ni (1-b-c-d) Co b Mn c M d The lithium nickel cobalt manganese composite oxide may be represented by the formula: O2, where each subscript falls within the ranges of 1≦a≦1.2, 0≦b≦0.4, 0≦c≦0.4, and 0≦d≦0.1. M includes at least one element selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Y, B, Mo, Nb, Zn, Sn, Zr, Ga, and V.

[0024] The active material-containing layer may contain, in addition to the active material, a conductive agent and a binder. The conductive agent may be added to improve current collection performance and reduce contact resistance between the active material and the current collector. The binder may be added to bind dispersed active materials together and to bind the active material and the current collector.

[0025] The density of the active material-containing layer is 3.0 g / cm 3 and exceeds 3.6 g / cm 3 It is preferable that the density is less than 3.0 g / cm. In an electrode having a density in the above range, the contact between the active material and the conductive agent is improved, and the electrical resistance is reduced. Therefore, a battery with excellent input / output performance can be fabricated using such an electrode. 3When the density exceeds 3.6 g / cm, the contact between the active material particles and between the active material and the conductive agent improves, the electrical resistance in the active material-containing layer decreases, and the large current output performance improves. In addition, the mechanical stability of the electrode improves. 3 When the density is less than 3.20 g / cm, the penetration of the electrolyte into the active material-containing layer is promoted, improving the output performance and life performance. Furthermore, the active material-containing layer is pressed with a high pressure to increase the density of the electrode. However, care must be taken not to use a pressure that is too high, as this can significantly wear the pressing device. More preferably, the density is 3.20 g / cm. 3 More than 3.50 g / cm 3 In a more preferable range, the resistance reduction effect is greater and damage to the active material is reduced, making it possible to maintain high capacity and low resistance of the battery for a longer period of time.

[0026] Pore ​​volume V measured by mercury porosimetry in the active material-containing layer Hg 0.03 mL / g≦V Hg ≦0.15 mL / g, or the specific surface area S measured by N2 gas adsorption method BET to 1.0 m 2 / g≦S BET ≦5.0 m 2 It is preferable to set the pore volume to 0.03 mL / g or more, or the specific surface area S BET to 1.0 m 2 / g or more, the permeation of the electrolyte is promoted, improving the output performance and life performance. BET to 5.0 m 2 / g or less, the contact between the active material particles and between the active material and the conductive agent increases, further reducing the electrical resistance and improving the large current output performance. In addition, the mechanical stability of the electrode increases. Hg is 0.03 mL / g or less V Hg ≦0.15 mL / g, and the specific surface area S measured by N2 gas adsorption method BET is 1.0 m 2 / g≦S BET ≦5.0 m 2The pore volume V measured by mercury porosimetry is preferably in the range of / g. Hg and specific surface area S by N2 gas adsorption method BET In an electrode in which the content of the active material and the conductive agent satisfies the above range, the contact between the active material and the conductive agent can be improved, the electrical resistance can be reduced, and a battery with excellent input / output performance can be produced. 3 Exceeds 3.6 g / cm 3 It is more desirable that the positive electrode active material-containing layer further has a preferable density of less than 0.05g. Hg is 0.05 mL / g or less V Hg ≦0.08 mL / g, and the specific surface area S measured by N2 gas adsorption method BET is 2.5 m 2 / g≦S BET ≦3.0 m 2 In a more preferable range, the active material, conductive agent, and binder are dispersed well, electrode density control is easily performed appropriately, and a battery with lower resistance and higher input / output performance can be produced.

[0027] In addition, the specific surface area of ​​the active material contained in the active material-containing layer is 0.5 m 2 / g or more 2.0 m 2 The specific surface area of ​​the active material here refers to the specific surface area measured by N2 gas adsorption method for the active material particles alone, without forming a layer. 2 When the specific surface area of ​​the active material is 2.0 m / g or more, the contact area between the active material and the electrolyte increases, improving output performance and lifespan. 2 When the specific surface area of ​​the active material particles is set to 0.5 m / g or less, the contact area between the active material and the electrolyte is kept at a moderate size, which suppresses side reactions and makes it difficult for the electrical resistance to increase. 2 / g or more 2.0 m 2 By setting the specific surface area of ​​the active material to 0.5 m / g or less, the contact area between the active material and the electrolyte can be optimized, and an electrode and a battery with low resistance and excellent life performance can be produced. 2 / g or more 1.0 m2 In a more preferred range, it is easy to control the contact area between the active material and the electrolyte, and it is easy to obtain an electrode with low resistance and excellent life performance.

[0028] In the particle size distribution (particle diameter distribution) of the active material-containing layer, the particle diameter D at which the cumulative frequency from the small particle diameter side becomes 50% 50 is 2 μm≦D 50 Particle size D, which is within the range of ≦7 μm and has a cumulative frequency of 10% from the small particle size side 10 The particle diameter D at which the cumulative frequency from the small particle diameter side becomes 90% 90 Ratio of D 90 / D 10 is 1.0≦D 90 / D 10 The particle size distribution here refers to the particle size distribution measured by the laser diffraction scattering method. Details of the measurement of the particle size distribution by the laser diffraction scattering method will be described later. 50 On the one hand, the particle diameter of the active material contained in the active material-containing layer, as well as the particle diameter and content ratio of other electrode materials such as conductive agents, can be reflected in the above-mentioned relationship 0.8 BET / S Hg <2.0 and 20 m 2 / mL Hg / V Hg <60 m 2 / mL, the average primary particle diameter of the active material and the D 50 tend to coincide. D 50 If the thickness is 2 μm or more, the contact area between the active material and the electrolyte is not too large, and side reactions are suppressed, so that the electrical resistance is less likely to increase. 50 When the thickness is 7 μm or less, a certain contact area between the active material and the electrolyte can be secured, improving output performance and lifespan. 90 and D 10 Relative to D 90 / D 10 When the ratio is 1.0 or more, the proportion of small particle size active material is reduced, so that the contact area between the active material and the electrolyte increases, and the increase in resistance due to the increase in side reactions can be suppressed. 90 / D 10 ​​When the D is 6.0 or less, the proportion of large particle size active material is reduced, so that the contact area between the active material and the electrolyte is increased appropriately, improving the output performance and life performance. 50 is 2 μm≦D 50 ≦7 μm, D 90 and D 10 Relative to D 90 / D 10 is 1.0≦D 90 / D 10 By satisfying the above condition of 0.5 m ≦5.0, the contact area between the active material and the electrolyte can be made appropriate, and an electrode and a battery having low resistance and excellent life performance can be produced. 2 / g or more 2.0 m 2 For an active material-containing layer containing an active material having a preferred specific surface area of ​​1 / g or less, D 50 and D 90 and D 10 More preferably, D obtained by measuring the particle size distribution of the active material-containing layer satisfies the above relationship. 50 is 2 μm≦D 50 ≦5 μm, D 90 and D 10 Relative to D 90 / D 10 is 2.0≦D 90 / D 10 It is desirable to satisfy the relationship of ≦4.0. In an active material-containing layer that satisfies this more preferable range, the dispersion of each component within the electrode tends to be good, and the reaction area with the electrolyte tends to be appropriately controlled.

[0029] The true specific gravity of the active material is 4.0 g / cm 3 or more, 6.0 g / cm 3 It is preferable that the density is 4.0 g / cm or less. 3 Active materials with a true specific gravity of 6.0 g / cm or more have few voids inside the active material particles, making it easy to increase electrode density and improve battery capacity and output performance. 3 Active materials with a true specific gravity of 4.0 g / cm or less have good lithium ion conductivity inside the particles and are less susceptible to local degradation, improving the life performance.3 More than 6.0 g / cm 3 By setting the true specific gravity of the active material particles to 4.6 g / cm or less, an electrode and a battery having a high battery capacity and a long life performance can be produced. 3 or more, 5.0 g / cm 3 In a more preferable range, the density of the electrode can be easily controlled and the performance can be further improved.

[0030] [material] Next, materials that can be used in the active material-containing layer provided in the electrode according to the first embodiment and in the current collector that can be included in such an electrode will be described.

[0031] <Active material containing layer> As described above, the active material-containing layer can contain a conductive agent and a binder in addition to the active material. The blending ratios of the active material, conductive agent, and binder in the active material-containing layer are preferably 80% by mass or more and 95% by mass or less of the active material, 0.5% by mass or more and 18% by mass or less of the conductive agent, and 0.5% by mass or more and 17% by mass or less of the binder.

[0032] <Active material> The active material-containing layer contains, as an active material, a lithium nickel cobalt manganese composite oxide (for example, Li a Ni (1-b-c-d) Co b Mn c M d O2; where 1≦a≦1.2, 0≦b≦0.4, 0≦c≦0.4, and 0≦d≦0.1; M includes at least one selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Y, B, Mo, Nb, Zn, Sn, Zr, Ga, and V. The lithium nickel cobalt manganese composite oxide may be used as a first active material, and the active material-containing layer may further include a second active material other than the first active material.

[0033] The second active material may be various oxides, such as lithium cobalt composite oxides (e.g., LiCoO), manganese dioxide, lithium manganese composite oxides (e.g., LiMnO, LiMnO), lithium nickel composite oxides (e.g., LiNiO), lithium nickel cobalt composite oxides (e.g., LiNi 0.8 Co 0.2 Examples of the second active material include lithium-containing iron oxides, lithium-containing vanadium oxides, and chalcogen compounds such as titanium disulfide and molybdenum disulfide. The electrode may contain one of the above compounds as the second active material, or may contain two or more of the above compounds as the second active material.

[0034] The mass ratio of the first active material to the total mass of the active material contained in the active material-containing layer is preferably 75 mass % or more and 100 mass % or less, and more preferably 80 mass % or more and 100 mass % or less.

[0035] The active material may have, for example, a particulate shape. That is, the active material-containing layer may contain particles of the active material. The active material particles may be primary particles or a mixture of primary particles and secondary particles.

[0036] It is preferable to have a high proportion of primary particles and a low proportion of secondary particles among the active material particles. The conductivity inside the secondary particles (inside the hollow structure) is poor, so eliminating the presence of the primary particles contained therein improves contact between the active material particles and the conductive agent, enabling further reduction in electrical resistance. By eliminating secondary particle aggregation of the active material particles in the electrode, even if the pore volume is reduced, there is no insufficient electrolyte retention or uneven reaction, improving input / output performance.

[0037] For these reasons, it is desirable to break down the agglomerations of the secondary particles of the active material, but it is also desirable not to further break down the primary particles of the active material to a particle size of less than 2 μm. By not making the active material particle size less than 2 μm, damage to the crystal structure can be avoided and good life performance can be maintained.

[0038] Furthermore, by making the average particle size of the active material 2 μm or more, the specific surface area of ​​the electrode can be reduced, and the impact of side reactions between the electrode and the electrolyte on life performance can be reduced.On the other hand, by making the average particle size 7 μm or less, the impact of the lithium ion concentration gradient occurring within the particles on life performance can be reduced.

[0039] <Conductive agent> The conductive agent preferably contains a carbon material. Examples of the carbon material include acetylene black, ketjen black, furnace black, graphite, and carbon nanotubes. The active material-containing layer can contain one type of conductive agent or two or more types of conductive agents.

[0040] The conductive agent can have, for example, a particle shape. Furthermore, to exhibit good conductivity, it is desirable that the average particle size of the conductive agent is neither too small nor too large. It is desirable to select a conductive agent with an appropriate average particle size to impart excellent conductivity to the electrode and improve the discharge capacity of the battery. For this reason, it is preferable to add, for example, acetylene black, which has excellent conductivity and an average particle size in the range of 20 nm to 100 nm. The average particle size of acetylene black is more preferably in the range of 30 nm to 70 nm.

[0041] <Binder> As the binder, a material containing fluorine atoms in the molecule is preferred because it has excellent oxidation resistance and improves life performance. Examples of such binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluorine-based rubber. Other binders that can be used include styrene-butadiene rubber, acrylic resin and its copolymer, polyacrylic acid, and polyacrylonitrile. The active material-containing layer can contain one of the above binders, or two or more of the above binders.

[0042] <Current collector> The current collector may be, for example, a metal foil or an alloy foil. Examples of metal foils include aluminum foil, stainless steel foil, and nickel foil. Examples of alloy foils include aluminum alloy, copper alloy, and nickel alloy.

[0043] Next, specific examples of the electrodes according to the first embodiment will be described with reference to the drawings.

[0044] 1 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.

[0045] 1 includes a positive electrode current collector 3a and a positive electrode active material-containing layer 3b provided on the surface of the positive electrode current collector 3a. The positive electrode active material-containing layer 3b is supported on the main surface of the positive electrode current collector 3a.

[0046] 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).

[0047] [Production method] The electrode according to the first embodiment can be produced, for example, by the following method.

[0048] First, a primary active material (first active material) is prepared. Particle growth is promoted by any method, such as increasing the calcination temperature or calcination time of a precursor containing nickel, cobalt, and manganese sources, or increasing the amount of lithium carbonate or other lithium source precursor, to synthesize a lithium-nickel-cobalt-manganese composite oxide with an optimized chemical composition so that the primary particle size is 2 μm or greater and the nickel content is at least a predetermined level.

[0049] A lithium nickel cobalt manganese composite oxide prepared as a first positive electrode active material, an optional second positive electrode active material, an optional conductive agent, and an optional binder are added to an appropriate solvent to obtain a mixture. The resulting mixture is then added to a mixer. The mixture is stirred in the mixer to obtain a slurry. In the stirring step, increasing the rotation speed of the mixer can promote the crushing of the active material and conductive agent particles, and the specific surface area S of the electrode after fabrication can be increased. BET The value of can be improved.

[0050] The slurry thus obtained is applied to one or both surfaces of the current collector. At this time, it is possible to leave a portion of the current collector on either surface where the slurry is not applied. Next, the coating is dried and pressed. At this time, by increasing the pressing load, it is possible to improve the electrode density, and the value of the electrode density can be adjusted. Furthermore, the pore diameter and pore specific surface area S inside the electrode, which can be measured by mercury intrusion porosimetry, increase as the pressing load increases. Hg , and pore volume V Hg It is possible to reduce the value of the electrode and adjust it to the above range, which provides excellent performance.

[0051] The pore size distribution and particle size distribution in the active material-containing layer can be adjusted within the ranges described above by adjusting parameters such as the selection and compounding ratio of the active material, conductive agent, and binder, the particle size of each of the particles of the active material and conductive agent, the stirring (dispersion) conditions of the mixture, and the pressing conditions. The electrode according to the first embodiment contains an NCM active material having an average primary particle size of 2 μm or more and 7 μm or less, and has a specific surface area S BET and the pore specific surface area S Hg The ratio is 0.8 BET / S Hg <2.0, and the pore specific surface area S Hg and the pore volume V measured by mercury porosimetry Hg The ratio is 20 m 2 / mL Hg / V Hg <60 m 2 This would not be possible without the idea of ​​adjusting the state of the pores in the active material-containing layer so as to satisfy the relationship of 1 / mL.

[0052] For example, shortening the calcination time of the precursor containing nickel, cobalt, and manganese sources or reducing the amount of the lithium source precursor promotes nucleation rather than particle growth. Therefore, it is difficult to say that a lithium-nickel-cobalt-manganese composite oxide with a primary particle size of 2 μm or more is obtained unintentionally.

[0053] In addition, by weakening the rotation of the stirrer in the stirring process, a slurry that sufficiently maintains the conductive network of the conductive agent can be obtained. Conversely, by strengthening the rotation of the stirrer, a slurry in which the active material is well dispersed can be obtained. In the electrodes produced using slurries obtained by weakening or strengthening the stirring in this way, the pore specific surface area S BET However, the ratio of the specific surface area S BET / S Hg tends to fall outside the range mentioned above.

[0054] ​​In addition, as mentioned above, the electrode density can be improved by increasing the pressing load, but a higher electrode density tends to make it easier to produce electrodes with better electrical contact and superior capacity. Conversely, by decreasing the pressing load, the pore diameter and pore specific surface area S inside the electrode, which can be measured by mercury intrusion porosimetry, can be reduced. Hg , and pore volume V Hg On the other hand, in an electrode with an extremely high or low density produced by excessive or insufficient pressing, not only will the electrode density fall outside the preferred range described above, but the pore specific surface area S Hg and pore volume V Hg The value of tends to fall outside the range mentioned above.

[0055] A specific example of electrode fabrication will be described in the examples below.

[0056] [Electrode Measurement] Various measurement methods for electrodes will be explained. Specifically, the method for measuring the composition of the active material, the method for measuring the particle size distribution in the active material-containing layer and the average primary particle diameter of the active material particles by laser diffraction scattering, the method for measuring the pore specific surface area S by N2 gas adsorption, BET The method for measuring the pore specific surface area S is HG and pore volume V Hg A method for measuring the specific gravity of the active material, a method for measuring the density of the active material-containing layer, and a method for measuring the true specific gravity of the active material will be described below.

[0057] When analyzing electrodes incorporated in a battery, the electrodes are removed using the following procedure.

[0058] First, prepare the battery to be measured. The battery to be measured must have a discharge capacity of 80% or more of its rated capacity. In other words, batteries that have deteriorated excessively will not be measured.

[0059] Next, the prepared battery is discharged until the open circuit voltage reaches 2.0 V to 2.2 V. Next, the discharged battery is transferred to a glove box filled with argon, the dew point of the internal atmosphere of which is −70°C. The battery is cut open in the glove box. The electrode group is removed from the cut-open battery. If the removed electrode group includes a positive electrode lead and a negative electrode lead, the positive electrode lead and the negative electrode lead are cut off, taking care not to short-circuit the positive electrode and the negative electrode.

[0060] Next, the electrode group is disassembled into a positive electrode, a negative electrode, and a separator. For example, the positive electrode is selected as the electrode to be measured. The resulting electrode is then washed using ethyl methyl carbonate as a solvent. In this washing, the disassembled components are completely immersed in the ethyl methyl carbonate solvent and left in that state for 60 minutes.

[0061] After cleaning, the electrodes are subjected to vacuum drying. Vacuum drying is performed by reducing the pressure from atmospheric pressure to -97 kPa or more in a 25°C environment and maintaining this state for 10 minutes. The electrodes thus removed after disassembly, cleaning, and vacuum drying are then subjected to the following measurements.

[0062] <Measurement of active material composition> The composition of the electrode active material can be determined by measuring the electrode surface using X-ray fluorescence (XRF).

[0063] <Measurement of particle size distribution by laser diffraction scattering method> The particle size distribution of the electrode can be measured by the laser diffraction / scattering method described below.

[0064] After preparing the electrode to be measured, the active material-containing layer is separated from the current collector using, for example, a spatula to obtain a powdered electrode composite sample containing the active material. Next, the powdered sample is placed in a measurement cell filled with N-methylpyrrolidone (NMP) until a measurable concentration is reached. Note that the capacity of the measurement cell and the measurable concentration vary depending on the particle size distribution measurement device.

[0065] For a measurement cell containing NMP and an electrode mixture sample dissolved therein, ultrasonic waves with an output of 40 W are irradiated for 5 minutes. According to such ultrasonic irradiation, the aggregation of conductive agent particles and active material particles can be resolved.

[0066] The measurement cell subjected to ultrasonic treatment is inserted into a particle size distribution measuring device by the laser diffraction / scattering method, and the particle size distribution is measured. As an example of the particle size distribution measuring device, Microtrac3100 can be cited.

[0067] Thus, the particle size distribution of the active material-containing layer can be obtained.

[0068] Also, by performing the above measurement using a sample of active material particles, the particle size distribution of the active material particles can be obtained. From the particle size distribution of the active material particles, the average primary particle size of the active material can be determined.

[0069] After dispersing and stirring the electrode mixture sample in NMP, the solid matter obtained by filtering the solvent is fired to remove the binder and the conductive agent, and isolate the active material particles. The particle size (D 50 ) corresponding to 50% of the cumulative frequency from the small particle size side in the particle size distribution measured using the obtained sample of active material particles is the average primary particle size of the active material.

[0070] <Measurement of Pore Specific Surface Area by N2 Gas Adsorption Method> The pore specific surface area S of the active material-containing layer by the N2 (nitrogen) gas adsorption method BET corresponds to the BET specific surface area of the electrode. The BET specific surface area is the specific surface area determined by the BET method and is calculated by the N2 gas adsorption method. The analysis is carried out, for example, by the following method.

[0071] Multiple rectangular measurement samples with planar dimensions of 0.5 cm x 2.0 cm are cut from the electrode. The weight of the cut measurement samples is measured. Next, 24 measurement samples are placed in the cell of the measurement device. These measurement samples are placed in a measurement cell for nitrogen adsorption / desorption measurement and dried at a temperature of 120°C or higher under N2 gas flow. The specific surface area is then measured using the BET single-point method or BET multi-point method. An example of a measurement device for N2 gas adsorption measurement is the Quantasorb manufactured by QUANTACHROME.

[0072] <Measurement of pore specific surface area and pore volume by mercury intrusion method> The pore specific surface area S of the active material-containing layer measured by mercury porosimetry Hg and pore volume V Hg The measurement method is described below.

[0073] A number of rectangular measurement samples with planar dimensions of 1.25 cm x 2.50 cm are cut out from the electrode. The weight of the cut measurement samples is measured. Next, 24 measurement samples are placed in the cell of the measurement device. These measurement samples are measured under conditions of an initial pressure of 10 kPa (approximately 1.5 psia, equivalent to a pore diameter of approximately 120 μm) and a final pressure of 414,000 kPa (approximately 60,000 psia, equivalent to a pore diameter of approximately 0.003 μm).

[0074] Next, the active material-containing layer is peeled off from another measurement sample cut out from the same electrode using, for example, a spatula to obtain a current collector piece. The weight of this current collector piece is measured. The weight of the active material-containing layer contained in the measurement sample is determined by subtracting the weight of the current collector piece from the weight of the measurement sample previously measured. In addition, the pore size distribution excluding the current collector weight is recalculated for a specific range (0.003 μm to 2 μm).

[0075] From the pore distribution obtained as described above and the weight of the active material-containing layer contained in the measurement sample, the pore volume per 1 g of the active material-containing layer (unit: mL / g) and the pore specific surface area of ​​the active material-containing layer (unit: m 2 / g) can be calculated.

[0076] Pore ​​specific surface area (pore specific surface area S H ) is calculated assuming the pore shape is cylindrical.

[0077] The analytical principle of mercury porosimetry is based on the following Washburn equation (1).

[0078] D=-4γcosθ / P (1) where D is the pore diameter, γ is the surface tension of mercury (480 dyne cm -1 ), θ is the contact angle between the mercury and the pore wall surface (140°), and P is the applied pressure. Since γ and θ are constants, the relationship between the applied pressure P and the pore diameter D can be found from Washburn's equation (1), and by measuring the mercury intrusion volume at that time, the pore diameter and its volume distribution can be derived.

[0079] An example of a measuring device for measuring pore size distribution is the Autopore 9520 pore size distribution measuring device manufactured by Micromeritics.

[0080] <Measurement of density of active material-containing layer> The density of the active material-containing layer can be measured by the following procedure.

[0081] First, the thickness of the prepared electrode is measured using a thickness measuring machine. Next, the electrode is punched out to a size of 1 cm x 1 cm using a cutting machine to obtain a sample of 1 cm x 1 cm. The weight of this sample is measured.

[0082] Next, the active material-containing layer is peeled off from the sample. For example, the active material-containing layer can be peeled off by immersing the sample in N-methylpyrrolidone. Any solvent can be used to peel off the active material-containing layer as long as it does not corrode the current collector and can peel off the active material-containing layer. The thickness and weight of the remaining current collector are measured.

[0083] Next, the thickness of the current collector is subtracted from the thickness of the electrode to calculate the thickness of the active material-containing layer. The weight of the current collector sample is also subtracted from the weight of the 1 cm x 1 cm sample to calculate the weight of the 1 cm x 1 cm active material-containing layer. The weight of the 1 cm x 1 cm active material-containing layer is then divided by the thickness of the active material-containing layer to calculate the density of the active material-containing layer (unit: g / cm). 3 ) can be calculated.

[0084] <Measurement of true specific gravity> Active material particles are isolated using the same procedure as described above for measuring the particle size distribution of active material particles. The sample of active material particles is then placed in a pycnometer, and the true density can be measured using a specified method. The gas or solvent used for substitution in pycnometer measurements can be any gas or solvent that can sufficiently penetrate or permeate the sample.

[0085] The electrode according to the first embodiment includes an active material layer containing at least a lithium nickel cobalt manganese composite oxide having an average primary particle diameter of 2 μm or more and 7 μm or less as an active material. The active material layer has a specific surface area S BET and the pore specific surface area S measured by mercury porosimetry Hg That is, 0.8 BET / S Hg <2.0. In addition, the pore specific surface area S Hg and the pore volume V measured by mercury porosimetry Hg That is, 20 m 2 / mL Hg / V Hg <60 m 2 / mL. This electrode can realize a battery with excellent capacity retention rate, suppressed resistance increase, and excellent life performance.

[0086] (Second embodiment) ​​According to a second embodiment, a battery is provided. The battery includes the electrode according to the first embodiment and an electrolyte. As described above, the electrode according to the first embodiment can realize a battery with excellent life performance. Therefore, the battery according to the second embodiment can have excellent life performance.

[0087] Such a battery may comprise a positive electrode and a negative electrode, and may include the electrode according to the first embodiment as the positive electrode.

[0088] The battery may further include a separator disposed between the positive electrode and the negative electrode. The positive electrode, the negative electrode, and the separator may constitute an electrode assembly. The electrolyte may be held in the electrode assembly.

[0089] Moreover, the battery can further include an exterior member that houses the electrode group and the electrolyte.

[0090] The battery may further include a positive terminal electrically connected to the positive electrode and a negative terminal electrically connected to the negative electrode. Each electrode terminal may be connected to, for example, a current collecting tab of the corresponding electrode. At least a portion of the positive terminal and at least a portion of the negative terminal may extend outside the exterior member.

[0091] 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.

[0092] The positive electrode, negative electrode, electrolyte, separator, exterior member, positive electrode terminal, and negative electrode terminal will be described in detail below.

[0093] (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.

[0094] The positive electrode may be the electrode according to the first embodiment. In the embodiment as a positive electrode, the positive electrode current collector, positive electrode active material, and positive electrode active material-containing layer of the positive electrode correspond to the current collector, active material, and active material-containing layer of the electrode according to the first embodiment, respectively. The electrode according to the first embodiment has been described in detail above, so a description of the positive electrode here will be omitted.

[0095] (2) Negative electrode The negative electrode includes a negative electrode current collector and a negative electrode active material-containing layer (negative electrode composite layer) supported on one side or both sides of the negative electrode current collector. The negative electrode active material-containing layer contains a negative electrode active material. The negative electrode active material-containing layer may further include a conductive agent and a binder in addition to the negative electrode active material. The conductive agent may be added to improve current collection performance and reduce contact resistance between the negative electrode active material and the negative electrode current collector. The binder may be added to bind dispersed negative electrode active material particles together and to bind the negative electrode active material and the negative electrode current collector together.

[0096] [material] Materials that can be used in the negative electrode active material-containing layer and the negative electrode current collector will be described below.

[0097] <Negative electrode active material containing layer> The blending ratios of the negative electrode active material, conductive agent, and binder in the negative electrode active material-containing layer are preferably in the ranges of 70% by mass to 96% by mass of the negative electrode active material, 2% by mass to 28% by mass of the conductive agent, and 2% by mass to 28% by mass of the binder. By setting the amount of the conductive agent to 2% by mass or more, the current collection performance of the negative electrode 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 the binder to 2% by mass or more, sufficient binding between the negative electrode active material-containing layer and the current collector can be expected, and excellent cycle performance can be expected.

[0098] On the other hand, from the viewpoint of increasing capacity, the conductive agent and binder are each preferably contained in an amount of 28 mass % or less.

[0099] <Negative electrode active material> The negative electrode was 0.4 V (vs. Li / Li +) or higher. In the battery according to the second embodiment including such a negative electrode, lithium deposition due to charge and discharge can be suppressed. Therefore, such a battery has excellent rapid charge and discharge performance.

[0100] 0.4 V (vs. Li / Li + ) or more, the negative electrode active material capable of inserting and extracting lithium ions is, for example, Li 4+x Ti5O 12 Lithium titanate with a spinel-type crystal structure represented by the formula (x varies in the range of -1≦x≦3 depending on the charge / discharge reaction), and Li with a ramsdellite-type crystal structure. 2+x Examples of suitable metal composite oxides include Ti3O7 (where x varies within the range of -1≦x≦3 depending on the charge / discharge reaction), and metal composite oxides containing Ti and at least one element selected from the group consisting of P, V, Sn, Cu, Ni, and Fe. 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 TiO2-P2O5, TiO2-V2O5, TiO2-P2O5-SnO2, and TiO2-P2O5-MeO (where Me is at least one element selected from the group consisting of Cu, Ni, and Fe). These metal composite oxides are converted into lithium-titanium composite oxides by intercalating lithium upon charging. Among the lithium-titanium composite oxides, spinel-type lithium titanate is preferred due to its excellent cycle performance.

[0101] The negative electrode may contain other active materials, such as carbonaceous materials and metal compounds.

[0102] Examples of carbonaceous materials 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. Carbonaceous materials preferably have a d002 interplanar spacing of 0.34 nm or less in the (002) plane as determined by X-ray diffraction.

[0103] As the metal compound, metal sulfides, metal nitrides, etc. can be used. As the metal sulfide, for example, titanium sulfide such as TiS2, molybdenum sulfide such as MoS2, and iron sulfides such as FeS, FeS2, Li y FeS2(0≦y≦2) can be used. As the metal nitride, for example, lithium cobalt nitride (e.g., Li s Co t N; 0<s<4, 0<t<0.5) can be used.

[0104] In addition to the above lithium titanium composite oxide, lithium titanium composite oxides such as monoclinic niobium titanium composite oxide and orthorhombic titanium-containing composite oxide may be included as the negative electrode active material.

[0105] Examples of the above monoclinic niobium titanium composite oxide include compounds represented by Li e Ti 1-f M1 f Nb 2-g M2 g O 7+δ Here, M1 is at least one selected from the group consisting of Zr, Si, and Sn. M2 is at least one selected from the group consisting of V, Ta, and Bi. Each subscript in the composition formula is 0≦e≦5, 0≦f<1, 0≦g<2, -0.3≦δ≦0.3. Specific examples of the monoclinic niobium titanium composite oxide include Li e Nb2TiO7(0≦e≦5).

[0106] Other examples of the monoclinic niobium titanium composite oxide include compounds represented by Li e Ti 1-f M3 f+g Nb 2-g O 7-δ Here, M3 is at least one selected from Mg, Fe, Ni, Co, W, Ta, and Mo. Each subscript in the composition formula is 0≦e≦5, 0≦f<1, 0≦g<2, -0.3≦δ≦0.3.

[0107] As an example of orthorhombic titanium-containing composite oxide, Li 2+h M4 2-i Ti 6-j M5 k O 14+σ Here, M4 is at least one selected from the group consisting of Sr, Ba, Ca, Mg, Na, Cs, Rb, and K. M5 is at least one selected from the group consisting of Zr, Sn, V, Nb, Ta, Mo, W, Y, Fe, Co, Cr, Mn, Ni, and Al. The subscripts in the composition formula are 0≦h≦6, 0≦i<2, 0≦j<6, 0≦k<6, and -0.5≦σ≦0.5. Specific examples of orthorhombic titanium-containing composite oxides include Li 2+h Na2Ti6O 14 (0≦k≦6).

[0108] Of the active materials, one may be contained in the negative electrode as the negative electrode active material, or two or more may be contained in the negative electrode as the negative electrode active material.

[0109] <Conductive agent> 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.

[0110] <Binder> Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-based rubber, and styrene-butadiene rubber (SBR). Other binders that can be used include carboxymethyl cellulose (CMC), polyimide, and polyamide. These binders may be used alone or in combination.

[0111] <Negative electrode current collector> The negative electrode current collector may be made of a material that is electrochemically stable at the potential at which the lithium ion insertion-extraction reaction of the negative electrode active material occurs. The negative electrode current collector is preferably a metal foil made of at least one selected from the group consisting of copper, nickel, stainless steel, and aluminum, or an aluminum alloy foil containing at least one selected from the group consisting of Mg, Ti, Zn, Mn, Fe, Cu, and Si.

[0112] The negative electrode current collector may have a variety of shapes depending on the application of the battery in which the negative electrode is used.

[0113] The negative electrode current collector may include a portion on its surface that does not carry a negative electrode active material-containing layer. This portion can serve as a negative electrode current collecting tab. Alternatively, the negative electrode may include a current collecting tab that is separate from the negative electrode current collector.

[0114] <Production method> The negative electrode can be produced, for example, by the following method.

[0115] First, a negative electrode active material, a binder, and optionally, a conductive agent are suspended in a suitable solvent to prepare a negative electrode slurry. A commonly used solvent, such as N-methylpyrrolidone, is used as the solvent. The resulting slurry is applied to a negative electrode current collector. The applied slurry is dried and pressed to obtain a negative electrode comprising a negative electrode current collector and a negative electrode active material-containing layer formed on the negative electrode current collector. Alternatively, the negative electrode active material, the binder, and optionally, the conductive agent may be formed into pellets and used as the negative electrode active material-containing layer.

[0116] (3) Separator The separator is made of an electrically insulating material. While there are no particular limitations on the material as long as it is insulating, the separator may be made of, for example, a porous film or nonwoven fabric made of a polymer such as polyolefin, cellulose, polyethylene terephthalate, or vinylon. The separator may be made of one material or a combination of two or more materials.

[0117] (4) Electrolyte Examples of the electrolyte include a liquid non-aqueous electrolyte prepared by dissolving an electrolyte salt (solute) in a non-aqueous solvent, and a gel non-aqueous electrolyte obtained by combining a liquid non-aqueous electrolyte with a polymer material.

[0118] Examples of the electrolyte salt include lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium hexalithium antimonate (LiSbF6), lithium difluorophosphate (LiPO2F2), lithium trifluoromethanesulfonate (LiCF3SO3; commonly known as LiTFS), and lithium bistrifluoromethanesulfonylamide {Li(CF3SO2)2N Examples of suitable electrolyte salts include lithium salts such as lithium bispentafluoroethanesulfonylamide {Li(CFSO)N; commonly known as LiBETI}, lithium bisoxalatoborate {LiB(CO)N; commonly known as LiBOB}, and lithium difluoro(trifluoro-2-oxido-2-trifluoromethylpropionato(2-)-0,0)borate {LiBFCOOC(CF)N; commonly known as LiBF(HHIB)}. These electrolyte salts may be used alone or in combination. Among these, LiPF and LiBF are particularly preferred.

[0119] The electrolyte salt is preferably dissolved in the non-aqueous solvent in a concentration of 1 mol / L to 3 mol / L, which can suppress the effect of increased viscosity due to an increase in the electrolyte salt concentration and can further improve performance when a high load current is applied.

[0120] 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), diethyl carbonate (DEC), and dipropyl carbonate (DPC); cyclic ethers such as tetrahydrofuran (THF) and 2-methyl tetrahydrofuran (2-MeTHF); and 1,2-dimethoxyethane (1,2-dimethoxyethane). Examples of suitable organic solvents include chain ethers such as ethane (DME); cyclic esters such as γ-butyrolactone (BL); chain esters such as methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate; 1,3-dioxolane; acetonitrile (AN); and sulfolane (SL). These organic solvents can be used alone or in the form of a mixture of two or more. It is preferable to use a non-aqueous solvent containing a cyclic carbonate and / or a chain carbonate.

[0121] Examples of polymer materials used for the gel-like non-aqueous electrolyte include polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), and polyethylene oxide (PEO).

[0122] (5) Exterior materials The exterior member may be formed from a laminate film or a metal container. Furthermore, a resin container made of polyolefin resin, polyvinyl chloride resin, polystyrene resin, acrylic resin, phenolic resin, polyphenylene resin, fluorine-based resin, etc. may also be used as the exterior member. When a metal container is used, the lid can be integrated with the container or formed as a separate member. The thickness of the metal container is preferably 3 mm or less, and more preferably 0.5 mm or less.

[0123] The shape of the exterior member may be flat (thin), rectangular, cylindrical, coin, button, sheet, laminated, etc. The exterior member may be for a small battery mounted in a portable electronic device or the like, or may be for a large battery mounted in a two- or four-wheeled automobile.

[0124] The thickness of the laminate film exterior component is preferably 0.5 mm or less. Examples of laminate films include multilayer films containing resin layers and metal layers disposed between the resin layers. The metal layer is preferably aluminum foil or aluminum alloy foil for weight reduction. The resin layer may be a film made of a polymer material such as polypropylene (PP), polyethylene (PE), nylon, or polyethylene terephthalate (PET). The laminate film can be sealed by heat fusion and molded into the shape of the exterior component.

[0125] The metal container is made of aluminum or an aluminum alloy. The aluminum alloy preferably contains elements such as magnesium, zinc, and silicon. When the aluminum or aluminum alloy contains transition metals such as iron, copper, nickel, and chromium, the content of these metals is preferably 100 ppm or less.

[0126] An example of such a battery will be described with reference to Figures 2 and 3. The flat-type battery shown in Figure 2 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 3, 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 in which the negative electrode 4, separator 5, positive electrode 3, and separator 5 are stacked in this order from the outside in, and then press-molding the laminate.

[0127] 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.

[0128] 2, a positive electrode terminal 7 is connected to the positive electrode 3 near the outer peripheral end of the wound electrode group 1. Furthermore, a negative electrode terminal 6 is 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.

[0129] Such a battery is not limited to the configuration shown in FIGS. 2 and 3, but may have a configuration shown in FIG. 4, for example.

[0130] In the prismatic battery shown in Fig. 4, 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. 2 and 3, for example.

[0131] 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.

[0132] 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, and Si. 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.

[0133] 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, and Si. 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.

[0134] Although the illustrated battery uses a wound-type electrode group in which a separator is wound together with a positive electrode and a negative electrode, a stacked-type electrode group in which positive electrodes and negative electrodes are alternately stacked with a separator interposed therebetween may also be used, or the electrode group may have another structure.

[0135] The battery according to the second embodiment includes the electrode according to the first embodiment, and therefore the battery has an excellent capacity retention rate, a suppressed increase in resistance, and an excellent life performance.

[0136] (Third embodiment) According to a third embodiment, a battery pack is provided, which includes the battery according to the second embodiment.

[0137] 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 such a battery pack may be electrically connected in series or parallel to each other to form a battery assembly. Such a battery pack may include a plurality of battery assemblies.

[0138] Next, an example of a battery pack according to a third embodiment will be described with reference to the drawings.

[0139] Fig. 5 is an exploded perspective view of an example battery pack according to the second embodiment, and Fig. 6 is a block diagram showing an electric circuit of the battery pack of Fig. 5.

[0140] 5 and 6 includes a plurality of unit cells 21. The unit cells 21 may be the flat battery of the example according to the second embodiment described with reference to FIG.

[0141] A 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.

[0142] 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. 6, 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.

[0143] 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 through wires 32 and 33 formed on the printed wiring board 24.

[0144] 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 or the positive 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. 5 and 6, each cell 21 is connected to wiring 35 for voltage detection. A detection signal is transmitted to the protection circuit 26 via these wirings 35.

[0145] 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.

[0146] 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 arranged 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 arranged 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.

[0147] 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.

[0148] 5 and 6 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.

[0149] 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.

[0150] The battery pack according to the third embodiment includes the battery according to the second embodiment, and therefore has an excellent capacity retention rate, a suppressed increase in resistance, and an excellent life performance.

[0151] [Example] 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 depart from the gist of the invention.

[0152] Example 1 [Preparation of positive electrode] The positive electrode active material is a lithium nickel cobalt manganese composite oxide (LiNi) with an average primary particle size of 3.7 μm. 0.8 Co 0.1 Mn 0.1O2, acetylene black as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder were prepared. The prepared materials were suspended in N-methylpyrrolidone to obtain a slurry for preparing a positive electrode. The mass ratios of the positive electrode active material, conductive agent, and binder added to N-methylpyrrolidone were 100 parts by mass, 5 parts by mass, and 10 parts by mass, respectively. A horizontal bead mill (RMH-03 manufactured by Imex Co., Ltd.) was used to disperse the slurry for preparing the positive electrode. Zirconia beads of 2 mm diameter were used as the beads, and the bead filling rate was 80%, the disk rotation speed was 800 rpm, and the flow rate was 200 cm. 3 The obtained slurry was applied to both sides of a strip-shaped aluminum foil (current collector) having a thickness of 12 μm and dried. After a pressing process, the density was 3.31 g / cm 3 , pore volume V by mercury porosimetry Hg 0.06 mL / g, and the pore specific surface area S Hg is 2.8 m 2 / g, pore specific surface area S by N2 adsorption method (BET method) BET is 2.6 m 2 A positive electrode having an active material-containing layer with a porosity of 1 / g was fabricated.

[0153] [Preparation of negative electrode] Spinel-type lithium titanate Li4Ti5O as the negative electrode active material 12 Graphite was prepared as a conductive agent, and PVdF was prepared as a binder. The prepared materials were suspended in N-methylpyrrolidone to obtain a slurry for preparing a negative electrode. The mass ratios of the negative electrode active material, conductive agent, and binder added to N-methylpyrrolidone were 95 mass%, 2.5 mass%, and 2.5 mass%, respectively. The prepared slurry for preparing a negative electrode was applied to both sides of a strip-shaped aluminum foil (current collector) with a thickness of 12 μm, dried, and then pressed to prepare a negative electrode.

[0154] [Preparation of electrode groups] The positive and negative electrodes prepared as described above were stacked with a separator sandwiched between them. A cellulose separator with a thickness of 14 μm and a width of 85 mm was used as the separator. The resulting laminate was wound around an axis extending in the direction of the short sides of the positive and negative electrode current collectors. The wound positive and negative electrodes and separator were then hot-pressed at 80°C and fixed with insulating tape. Thus, a wound electrode group was obtained, comprising a positive electrode, a negative electrode, and a separator positioned between the positive and negative electrodes.

[0155] [Preparation of non-aqueous electrolyte] A non-aqueous solvent was prepared by mixing propylene carbonate (PC) and diethyl carbonate (DEC) in a volume ratio of 1:1. Lithium hexafluorophosphate (LiPF6) was dissolved in the resulting non-aqueous solvent at a concentration of 1.0 mol / L to prepare a non-aqueous electrolyte.

[0156] [Battery assembly] The electrode group formed into a flat shape as described above was inserted into a metal can made of an aluminum plate with a thickness of 0.5 mm. The opening of the metal can was sealed with a sealing plate, and the electrode group was housed inside the metal can as an exterior member. The nonaqueous electrolyte prepared as described above was poured into the container through an electrolyte injection port provided in the sealing plate. Next, a sealing lid was welded to the periphery of the electrolyte injection port to produce a flat-type nonaqueous electrolyte battery.

[0157] (Examples 2-6, Comparative Examples 1-8) In Examples 2-6 and Comparative Examples 1-8, the positive electrode active material was changed from that of Example 1 as shown in Table 1, and the dispersion conditions of the positive electrode preparation slurry and the press load of the active material-containing layer were adjusted to change the design of the positive electrode active material-containing layer to that shown in Table 2. Batteries were fabricated in the same manner as in Example 1. The positive electrode active material-containing layer was designed to have a pore volume V measured by mercury intrusion porosimetry as shown in Table 2. Hg , pore specific surface area S by mercury intrusion porosimetry Hg , specific surface area S by N2 gas adsorption method (BET method) BET , electrode density, and particle size distribution were adjusted.

[0158] The details of the positive electrode active materials in each example and comparative example are summarized in Table 1. The details of the positive electrode active materials include the composition of the active material, the average primary particle size of the active material particles, the BET specific surface area of ​​the active material particles alone, and the true specific gravity of the active material.

[0159] The following Table 2 summarizes the design of the positive electrode active material-containing layer in each example and each comparative example. The active material-containing layer was designed based on the pore volume V measured by the above-mentioned mercury intrusion method. Hg and pore specific surface area S Hg , the specific surface area S measured by the N2 gas adsorption method (BET method) mentioned above BET , the electrode density (density of the active material-containing layer excluding the current collector) measured by the above-mentioned method, and the particle diameter D in the particle size distribution measured by the above-mentioned laser diffraction scattering method. 50 and particle diameter D 90 and particle diameter D 10 Relative to D 90 / D 10 Shows.

[0160] [Table 1]

[0161] [Table 2]

[0162] [Cycle test] A cycle test was carried out on each of the prepared batteries as follows.

[0163] First, the battery was charged in a 25°C environment and adjusted to a state of charge (SOC) of 50%. After waiting for one hour, the OCV (open circuit voltage) was recorded. The battery was then discharged at a current of 10 C, and the voltage drop during this time was measured. The OCV value was subtracted from the voltage drop during 10 C discharge, and the resulting value was divided by the current value at 10 C to determine the discharge resistance (unit: mΩ) of the battery.

[0164] The battery was then charged at a 2C rate to 100% SOC and discharged at a 2C rate to 0% SOC for 600 cycles at 45°C. The discharge capacity was measured at the first and 600th cycles.

[0165] After the 600th discharge cycle, the discharge resistance of the battery was measured again.

[0166] The capacity retention rate was calculated from the discharge capacities at the first and 600th cycles using the following formula: Capacity retention rate (unit: %) = [Discharge capacity at the 600th cycle / Discharge capacity at the first cycle] × 100%. The resistance increase rate was calculated from the discharge resistance values ​​before and after 600 charge / discharge cycles using the following formula: Resistance increase rate (unit: %) = [Discharge resistance value after cycling / Discharge resistance value before cycling] × 100%. The calculation results are shown in Table 3 below.

[0167] [Table 3]

[0168] From Table 3, it can be seen that the batteries fabricated in Examples 1-6 achieved both excellent capacity retention and suppression of resistance increase. On the other hand, it can be seen that in Comparative Example 1-8, either or both of the capacity retention and suppression of resistance increase were inferior to those in Example 1-6. This is because in Example 1-6, the positive electrode active material-containing layer contained a lithium nickel cobalt manganese composite oxide having a primary particle diameter of 2 μm or more and 7 μm or less as the positive electrode active material, and the ratio of the pore specific surface area to the pore volume was 0.8 or less. BET / S Hg <2.0 and 20 m 2 / mL Hg / V Hg <60 m 2 / mL, the permeability of the electrolyte into the positive electrode active material-containing layer and the electrode reaction area could be appropriately controlled.

[0169] ​​Among the batteries of Example 1-6, the battery of Example 1-3 was particularly excellent in both capacity retention rate and resistance increase suppression. Hg / V Hg 40 m 2 / mL Hg / V Hg <50 m 2 / mL, a battery superior in terms of capacity retention rate and resistance increase can be obtained.

[0170] On the other hand, the battery of Comparative Example 1-8 did not satisfy any of the above conditions in the positive electrode active material-containing layer, and either or both of the capacity retention rate and the suppression of resistance increase were inferior to those of Example 1-6. That is, the electrode reaction area in the positive electrode active material-containing layer was too large, causing many side reactions and forming many resistance components, or the electrolyte solution did not penetrate into the positive electrode active material-containing layer well or did not penetrate uniformly, causing a distribution in the electrode reaction, and therefore, both the capacity retention rate and the suppression of resistance increase were not excellent.

[0171] Specifically, in Comparative Example 1, the average primary particle diameter of the positive electrode active material was larger than 7 μm. In Comparative Example 1, the capacity retention rate was worse than in Examples 1-6. In an electrode with a large particle diameter of the active material, the distribution of lithium within the active material particles is likely to become uneven, resulting in a non-uniform distribution of the electrode reaction. This leads to deterioration of the active material and a deterioration in the capacity retention rate during cycling.

[0172] In Comparative Example 2, S BET and S Hg In Comparative Example 2, the ratio between S Hg S BET greater than 0.8 BET / S Hg Since the relationship of S<2.0 was not satisfied, the capacity retention rate was worse than in Example 1-6, and the increase in resistance was greater. Hg ​​In electrodes where the pore size is significantly larger, the number of rough pores increases, causing the reaction distribution to become uneven across the electrode, and the electrode surface area where side reactions occur also increases, which leads to deterioration of the active material and an increase in side reactions, resulting in both a decrease in capacity retention during cycling and an increase in resistance.

[0173] In Comparative Example 3, the average primary particle diameter of the positive electrode active material was larger than 7 μm, as in Comparative Example 1. In Comparative Example 3, the capacity retention rate was worse than in Comparative Example 1, and the resistance increase was also increased. In Comparative Example 3, S was lower than in Comparative Example 1. Hg and S BET The overall specific surface area of ​​the pores in the electrode is large, and the electrode area where side reactions occur also increases, leading to deterioration of the active material and an increase in side reactions, resulting in both a deterioration in the capacity retention rate during cycling and an increase in resistance.

[0174] In Comparative Example 4, the average primary particle diameter of the positive electrode active material was larger than 7 μm, similar to Comparative Examples 1 and 3. Hg and V Hg The ratio S between Hg / V Hg 60 m 2 / mL. It can be seen that the capacity retention rate in Comparative Example 4 is worse than that in Comparative Example 3. That is, the specific surface area S BET and the pore specific surface area S measured by mercury porosimetry Hg Even if the surface of a single-crystal active material is uniform and the pore volume V Hg specific surface area S Hg 60 m 2 / mL or more, the permeability of the electrolyte is poor, which leads to localized deterioration of the active material and a poor capacity retention rate.

[0175] In Comparative Example 5, the average primary particle diameter of the positive electrode active material was larger than 7 μm, similar to Comparative Examples 1, 3, and 4. BET and S Hg The ratio between S Hg and V Hg The ratio S between Hg / VHg 20 m 2 / mL. In Comparative Example 5, the increase in resistance was significantly greater than in Comparative Example 1. That is, S Hg is small, 0.8 BET / S Hg <2.0 and 20 m 2 / mL Hg / V Hg <60 m 2 It can be seen that the resistance increased significantly as a result of not satisfying any of the relationships of / mL.

[0176] In Comparative Example 6, S BET and S Hg The ratio between is 0.5 and S Hg and V Hg The ratio S between Hg / V Hg 60 m 2 / mL. BET and S Hg The ratio between is 0.8 and S Hg and V Hg The ratio S between Hg / V Hg is 60.6 m 2 / mL. Comparative Example 6 had the lowest capacity retention rate among Comparative Examples 1 to 8, and Comparative Example 7 had the second lowest capacity retention rate after Comparative Example 4. That is, in Comparative Examples 6 and 7, the pore volume V Hg specific surface area S Hg It was confirmed that when the temperature becomes very high, the capacity retention rate deteriorates.

[0177] In Comparative Example 8, the average primary particle diameter of the positive electrode active material was larger than 7 μm, similar to Comparative Examples 1 and 3-5. Hg and V Hg The ratio S between Hg / V Hg 20 m 2 / mL. In Comparative Example 8, the increase in resistance was greater than in Comparative Example 1, which means that many side reactions occurred on the electrode. This shows that even if the active material is a single crystal with a uniform surface, the pore volume V Hg ​​specific surface area S Hg It can be seen that when is 20 or less, the effect of suppressing the increase in resistance cannot be obtained.

[0178] According to one or more of the above-described embodiments and examples, an electrode is provided. The electrode has an active material-containing layer containing a lithium nickel cobalt manganese composite oxide having an average primary particle size of 2 μm or more and 7 μm or less as an active material. In the active material-containing layer, the specific surface area S BET and the pore specific surface area S measured by mercury porosimetry Hg and 0.8 BET / S Hg <2.0 and the pore specific surface area S measured by mercury porosimetry Hg and the pore volume V measured by mercury porosimetry Hg and 20 m 2 / mL Hg / V Hg <60 m 2 The electrode can provide a battery and a battery pack with excellent life performance.

[0179] 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. The inventions described in the original claims of this application are set forth below. [1] An active material-containing layer containing an active material, the active material contains a lithium nickel cobalt manganese composite oxide having an average primary particle size of 2 μm or more and 7 μm or less, N 2 The specific surface area S of the active material-containing layer measured by gas adsorption BET and the pore specific surface area S of the active material-containing layer measured by mercury porosimetry Hg satisfies the relationship 0.8 < 2.0, BET / S Hg The pore specific surface area S of the active material-containing layer and the pore volume V of the active material-containing layer measured by mercury porosimetry. ​​Hg 20 m Hg / mL / mL relationship is satisfied. 2 electrode. Hg / V Hg <60 m 2 [2] The density of the active material-containing layer is 3.0 g / cm and exceeds 3.6 g / cm The electrode according to [1], wherein the electrode is less than 3 [3] The pore volume V 3 is 0.03 mL / g or less V The electrode according to [1], wherein the range is ≦0.15 mL / g. Hg [4] The specific surface area S Hg is 1.0 m / g≦S BET The electrode according to [1], wherein the range is / g. 2 [5] The density of the active material-containing layer is 3.0 g / cm BET ≦5.0 m 2 and exceeds 3.6 g / cm the pore volume V is less than 3 is 0.03 mL / g or less V 3 ≦0.15 mL / g, and the specific surface area S Hg is 1.0 m Hg / g≦S BET The electrode according to [1], wherein the range is / g. 2 The specific surface area of ​​the active material measured by gas adsorption is 0.5 m BET ≦5.0 m 2 / g or more 2.0 m [6] N 2 / g or less, and the particle diameter D at which the cumulative frequency from the small particle diameter side in the particle size distribution of the active material-containing layer is 50% 2 is 2 μm≦D 2 ≦7 μm, and the particle diameter D at which the cumulative frequency from the small particle diameter side in the particle size distribution is 10% 50 The particle diameter D at which the cumulative frequency from the small particle diameter side becomes 90% 50 Ratio of D 10 is 1.0≦D 90 The electrode according to any one of [1] to [5], wherein the σ is in the range of ≦5.0. 90 / D 10 [7] The active material has a density of 4.0 g / cm 90 / D 10 More than 6.0 g / cm The electrode according to any one of [1] to [6], having the following true specific gravity: 3 [8] The lithium nickel cobalt manganese composite oxide is Li 3 Ni Co a Mn (1-b-c-d) ​ b ​ c M d O 2

[0023] The electrode according to any one of [1] to [7], wherein 1≦a≦1.2, 0≦b≦0.4, 0≦c≦0.4, and 0≦d≦0.1, and M is a compound containing at least one selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Y, B, Mo, Nb, Zn, Sn, Zr, Ga, and V. [9] An electrode according to any one of [1] to [8]; Electrolytes and A battery comprising:

[10] A battery pack comprising the battery according to [9].

Claims

1. The active material-containing layer includes an active material, the active material contains a lithium nickel cobalt manganese composite oxide having an average primary particle size of 2 μm or more and 7 μm or less, N 2 The specific surface area S of the active material-containing layer measured by gas adsorption BET and the pore specific surface area S of the active material-containing layer measured by mercury porosimetry. Hg is 0.8<S BET / S Hg < Satisfying 2.0 relationships, The pore specific surface area S of the active material-containing layer Hg and the pore volume V of the active material-containing layer measured by mercury porosimetry. Hg 20 m 2 / mL<S Hg / V Hg <60 m 2 / mL relationship, The pore volume V Hg is within the range of 0.05 mL / g≦V Hg ≦0.09 mL / g, An electrode, wherein the specific surface area S BET is in the range of 2.5 m 2 / g≦S BET ≦2.8 m 2 / g.

2. An electrode as described in claim 1, wherein the specific surface area S BET and the pore specific surface area S Hg satisfy the relationship 0.9 < S BET / S Hg < 1.0, and the pore specific surface area S Hg and the pore volume V Hg satisfy the relationship 30.9 m 2 / mL < S Hg / V Hg < 53.9 m 2 / mL.

3. The density of the active material-containing layer is 3.0 g / cm 3 and exceeds 3.6 g / cm 3 3. The electrode of claim 1 or 2, wherein the .lambda.

4. N 2 The specific surface area of ​​the active material measured by gas adsorption is 0.5 m 2 / g or more 2.0 m 2 / g or less, and the particle diameter D at which the cumulative frequency from the small particle diameter side in the particle size distribution of the active material-containing layer is 50% 50 is 2 μm≦D 50 ≦7 μm, and the particle diameter D at which the cumulative frequency from the small particle diameter side in the particle size distribution is 10% 10 The particle diameter D at which the cumulative frequency from the small particle diameter side becomes 90% 90 Ratio of D 90 / D 10 is 1.0≦D 90 / D 10 4. The electrode according to claim 1, wherein the ρ is in the range of ≦5.

0.

5. The active material is 4.0 g / cm 3 More than 6.0 g / cm 3 5. The electrode according to claim 1, having a true specific gravity of:

6. The lithium nickel cobalt manganese composite oxide is Li a Ni (1-b-c-d) Co b Mn c M d O 2 6. The electrode of claim 1 , wherein 1≦a≦1.2, 0≦b≦0.4, 0≦c≦0.4, and 0≦d≦0.1, and M comprises a compound including at least one selected from the group consisting of Fe, Cu, Ti, Mg, Al, W, Y, B, Mo, Nb, Zn, Sn, Zr, Ga, and V.

7. The electrode according to any one of claims 1 to 6; Electrolytes and A battery comprising:

8. A battery pack comprising the battery according to claim 7.

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