Lithium-ion battery

Abstract

To improve a high-rate resistance.SOLUTION: A lithium-ion battery includes: a power generation element; and electrolyte. The power generation element includes: a positive electrode; a separator; a negative electrode; a first intervening layer; and a second intervening layer. In the power generation element, at least one of a first gap and a second gap is formed. The first gap is a gap formed to between a negative electrode active material layer and a separator. The second gap is a gap formed between a positive electrode active material layer and the separator. The first intervening layer is arranged in at least one of the first gap and the second gap. The second intervening layer is arranged in at least one of the first gap and the second gap. The power generation element includes a first end portion in one end in a lamination direction, and includes a second end portion in the other end in the lamination direction. The first intervening layer is disposed at a position nearer to the first end portion than the second intervening layer, and a relation "P1 is not equal to P2" is satisfied. The P1 indicates a transmission coefficient of the first intervening layer with respect to the electrolyte, and the P2 indicates a transmission coefficient of the second intervening layer with respect to the electrolyte.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a lithium-ion battery.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2018-106981 discloses providing a region with a low electrolyte permeation coefficient at an end in the width direction of an active material layer in a strip-shaped electrode sheet of a wound electrode body.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] A lithium-ion battery includes a power generation element. The power generation element is also referred to as, for example, an "electrode body", an "electrode group", etc. The power generation element includes a positive electrode active material layer, a separator, and a negative electrode active material layer. Each active material layer is a porous body having voids, and an electrolyte is held in the voids.

[0005] With high-rate charging, the active material can expand rapidly. Due to the expansion of the active material, the voids in the active material layer can decrease. Due to the decrease in the voids, the electrolyte can flow out from the active material layer. Due to the outflow of the electrolyte, the electrolyte can be depleted in the active material layer. Due to the depletion of the electrolyte in the active material layer, the battery performance can deteriorate.

[0006] On the other hand, during discharge, the active material can contract. Due to the contraction of the active material, the voids in the active material layer increase. Due to the increase in voids, the electrolyte around the active material layer can flow into the active material layer. Since the outflow amount of the electrolyte during charging and the inflow amount of the electrolyte during discharge are different, there is a possibility that the salt concentration of the electrolyte becomes uneven inside and outside the active material layer. By repeating charge and discharge, the unevenness of the salt concentration inside and outside the active material layer is promoted, which may also cause a decrease in battery performance. It is required to improve the "high-rate tolerance", that is, the battery performance is less likely to deteriorate even by high-rate charge and discharge.

[0007] The permeability coefficient indicates the ease of electrolyte permeation. The larger the permeability coefficient, the easier it is considered that the electrolyte permeates the object. In a wound power generation element, by arranging a region with a small permeability coefficient at the edge of the active material layer, it is expected that the outflow of the electrolyte from the active material layer is reduced. For example, the permeability coefficient can locally change due to local differences in the composition, density, etc. of the active material layer. However, local differences in composition, etc. within the active material layer may cause disadvantages such as an increase in performance variation. Also, due to local differences in composition, etc. within the active material layer, there is a possibility that productivity decreases. Furthermore, since the electrolyte flowing out of the active material layer is difficult to flow back into the active material layer again, there is a possibility that the unevenness of the salt concentration inside and outside the active material layer is promoted.

[0008] An object of the present disclosure is to improve high-rate tolerance.

Means for Solving the Problems

[0009] Hereinafter, the technical configuration and operation effects of the present disclosure will be described. However, the operation mechanism includes assumptions. The operation mechanism does not limit the technical scope of the present disclosure.

[0010] 1. The lithium-ion battery includes a power generation element and an electrolyte. The power generation element includes a positive electrode, a separator, a negative electrode, a first intermediate layer, and a second intermediate layer. The positive electrode and the negative electrode are alternately laminated with the separator interposed therebetween. The positive electrode includes a positive electrode current collector foil and a positive electrode active material layer. The negative electrode includes a negative electrode current collector foil and a negative electrode active material layer. At least one of a first gap and a second gap is formed in the power generation element. The first gap is a gap formed between the negative electrode active material layer and the separator. The second gap is a gap formed between the positive electrode active material layer and the separator. A first intervening layer is disposed in at least one of the first gap and the second gap. A second intervening layer is disposed in at least one of the first gap and the second gap. The power generation element has a stacking direction. The stacking direction is parallel to the thickness directions of the positive electrode, the separator, and the negative electrode. The power generation element has a first end at one end in the stacking direction and a second end at the other end in the stacking direction. The first intervening layer is closer to the first end than the second intervening layer. The relationship of the following formula (1) is satisfied. P1≠P2 (1) In formula (1), P1 represents the permeation coefficient of the first intervening layer with respect to the electrolytic solution. P2 represents the permeation coefficient of the second intervening layer with respect to the electrolytic solution.

[0011] The "intervening layer" intervenes between the active material layer and the separator. When the material of the intervening layer has a higher melting point than the material of the separator, the intervening layer may be referred to as "HRL (Heat Resistance Layer)" or the like. According to new findings, not only the active material layer but also a considerable amount of electrolytic solution enters and exits the power generation element through the intervening layer. Conventionally, the power generation element includes one type of intervening layer.

[0012] In the present disclosure, the power generation element includes a first intermediate layer and a second intermediate layer. The first intermediate layer and the second intermediate layer have different permeation coefficients. That is, the permeability of the electrolytic solution is different between the first intermediate layer and the second intermediate layer. According to further new findings, in a laminated power generation element, by arranging two intermediate layers with different permeabilities of the electrolytic solution at appropriate positions, an improvement in high-rate tolerance is expected. That is, the power generation element has a first end at one end in the stacking direction and a second end at the other end in the stacking direction. The first intermediate layer is closer to the first end than the second intermediate layer. The intermediate layer with lower liquid permeability can hold the electrolytic solution. By the intermediate layer holding the electrolytic solution, it is expected that the depletion of the electrolytic solution will be reduced. On the other hand, the intermediate layer with higher liquid permeability can promote the outflow and inflow of the electrolytic solution. By making the outflow and inflow of the electrolytic solution active around the intermediate layer, it is expected that the frequency of mixing of the electrolytic solution inside and outside the power generation element will increase. By the mixing of the electrolytic solution, it is expected that the unevenness of the salt concentration will be reduced. It is considered that the high-rate tolerance is improved by the synergistic effect of these actions.

[0013] 2. The lithium-ion battery described in the above "1" may include, for example, the following configuration. The electrolytic solution is more distributed at the first end than at the second end.

[0014] Due to the action of gravity, in the power generation element, the electrolytic solution tends to be unevenly distributed on the lower end side in the vertical direction. On the other hand, on the upper end side in the vertical direction, due to the outflow of the electrolytic solution, the electrolytic solution tends to be depleted. This is because it is difficult for the outflowed electrolytic solution to return to the outflow position. For example, in the stacking direction, the first intermediate layer may be arranged at a position where the electrolytic solution tends to be unevenly distributed. For example, in the stacking direction, the second intermediate layer may be arranged at a position where the electrolytic solution tends to be depleted. Note that the stacking direction may be parallel to the vertical direction or may not be parallel.

[0015] 3. The lithium-ion battery described in the above "1" or "2" may include, for example, the following configuration. The first intermediate layer is arranged in the second gap. The second intermediate layer is arranged in the first gap.

[0016] For example, a first intermediate layer may be disposed between the positive electrode active material layer and the separator. For example, a second intermediate layer may be disposed between the negative electrode active material layer and the separator.

[0017] 4. The lithium ion battery according to any one of the above "1" to "3" may include, for example, the following configuration. The relationship of the following formula (2) is satisfied. P1 > P2 (2)

[0018] For example, the permeability coefficient (P1) of the first intermediate layer may be larger than the permeability coefficient (P2) of the second intermediate layer.

[0019] 5. The lithium ion battery according to any one of the above "1" to "4" may include, for example, the following configuration. The electrolytic solution includes a supporting salt and a solvent. The first intermediate layer includes first inorganic particles and a first binder. The second intermediate layer includes second inorganic particles and a second binder. The relationship of the following formula (3) is satisfied. Δ1 > Δ2 (3) In formula (3), Δ1 represents the absolute value of the difference between the SP value of the electrolytic solution and the SP value of the first binder. Δ2 represents the absolute value of the difference between the SP value of the electrolytic solution and the SP value of the second binder. The unit of the SP value is (cal / cm 3 ) 1 / 2 is.

[0020] For example, the permeability of the electrolytic solution may be adjusted by the SP value (solubility parameter). The larger the absolute value of the difference between the SP value of the solvent of the electrolytic solution and the SP value of the binder of the intermediate layer, the more active the entry and exit of the electrolytic solution in the intermediate layer tend to be. Hereinafter, the "absolute value of the difference" may be simply referred to as the "difference".

[0021] 6. The lithium ion battery according to the above "5" may include, for example, the following configuration. The relationships of the following formulas (4) and (5) are satisfied. 2.5 ≤ Δ1 (4) Δ2 ≤ 2 (5)

[0022] Since Δ1 is 2.5 or more, it is expected that the outflow and inflow of the electrolytic solution in the intermediate layer are promoted. Since Δ2 is 2 or less, it is expected that the electrolytic solution is likely to be retained in the intermediate layer.

[0023] 7. The lithium ion battery described in the above "2" may include, for example, the following configuration. The power generation element includes a first unit and a second unit. In the stacking direction, the first unit is closer to the first end than the second unit. Each of the first unit and the second unit includes a positive electrode, a separator, and a negative electrode. The first unit includes a first intermediate layer in at least one of the first gap and the second gap. The second unit includes a second intermediate layer in at least one of the first gap and the second gap. The relationship of the following formula (2) is satisfied. P1 > P2 (2)

[0024] The power generation element may include a plurality of types of units (repeating units). The first unit is located at a position where the electrolytic solution is likely to be unevenly distributed in the stacking direction. The first unit includes a first intermediate layer. The first intermediate layer has a relatively large permeability coefficient (P1). In the first intermediate layer of the first unit, it is expected that the frequency of mixing of the electrolytic solution inside and outside the power generation element increases due to the active outflow and inflow of the electrolytic solution. It is expected that the unevenness of the salt concentration is reduced by the mixing of the electrolytic solution. On the other hand, the second unit is located at a position where the electrolytic solution is likely to be depleted in the stacking direction. The second unit includes a second intermediate layer. The second intermediate layer has a relatively small permeability coefficient (P2). By retaining the electrolytic solution in the second intermediate layer, the outflow of the electrolytic solution from the second unit can be reduced. The synergistic effect of these actions is expected to improve the high rate tolerance.

[0025] 8. The lithium ion battery described in the above "7" may include, for example, the following configuration. The second unit includes a second intermediate layer in the second gap.

[0026] In the second unit, it is expected that the outflow of the electrolytic solution is reduced by disposing a second intervening layer between the negative electrode active material layer and the separator.

[0027] Hereinafter, embodiments of the present disclosure (hereinafter may be abbreviated as "the present embodiment"), and examples of the present disclosure (hereinafter may be abbreviated as "the present example") will be described. However, the present embodiment and the present example do not limit the technical scope of the present disclosure. The present embodiment and the present example are illustrative in all respects. The present embodiment and the present example are non-limiting. The technical scope of the present disclosure includes all modifications within the meaning and scope equivalent to the description of the claims. For example, any configuration is extracted from the present embodiment, and their arbitrary combination is also initially planned.

Brief Description of the Drawings

[0028]

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Modes for Carrying Out the Invention

[0029] <Main Terms> "Comprise", "include", "have", and their variants are open-ended terms. Open-ended terms may further include additional elements in addition to the essential elements, or may not include them. The description "consisting of" is a closed term. However, even a configuration expressed by a closed term may include additional elements that are normally accompanying impurities or are irrelevant to the target technology. The description "substantially consisting of" is a semi-closed term. In semi-closed terms, the addition of elements that do not substantially affect the basic and novel characteristics of the target technology is allowed.

[0030] Expressions such as "may" and "can" are used in an allowable sense, "having the possibility of doing", rather than in an obligatory sense, "meaning that one must do".

[0031] Geometric terms should not be construed in a strict sense. Examples of geometric terms include, for example, "parallel", "perpendicular", "orthogonal", etc. For example, "parallel" may deviate somewhat from "parallel" in the strict sense. Geometric terms may include, for example, tolerances, errors, etc. in design, operation, manufacturing, etc. The dimensional relationships in each figure may not match the actual dimensional relationships. For the purpose of assisting the reader's understanding, the dimensional relationships in each figure may be changed. For example, the length, width, thickness, etc. may be changed. In some cases, some configurations may be omitted.

[0032] A numerical range such as "from m to n%" includes the upper limit value and the lower limit value unless otherwise specified. That is, "from m to n%" indicates a numerical range of "m% or more and n% or less". Also, "m% or more and n% or less" includes "more than m% and less than n%". "Or more" and "or less" are represented by the inequality sign "≦" with an equal sign. "More than" and "less than" are represented by the inequality sign "<" that does not include an equal sign. A numerically arbitrarily selected value within the numerical range may be used as a new upper limit value or lower limit value. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described in another part of this specification, in a table, in a figure, etc.

[0033] All numerical values are modified by the term "about". The term "about" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values may be approximate values that can vary depending on the usage form of the disclosed technology. All numerical values may be expressed in significant figures. A measured value may be, unless otherwise specified, an average value in multiple measurements. The number of measurements may be 3 or more, may be 5 or more, or may be 10 or more. Generally, the greater the number of measurements, the more reliable the average value is expected to be. A measured value may be rounded off based on the number of significant figures. A measured value may include errors associated with, for example, the detection limit of a measuring device.

[0034] "Intermediate layer" is a general term for the first intermediate layer and the second intermediate layer. Similarly, "inorganic particles" is a general term for the first inorganic particles and the second inorganic particles. "Binder" is a general term for the first binder and the second binder.

[0035] "Transmission coefficient" indicates a value measured by the following method. First, a cross-sectional image of an object (the first intermediate layer, the second intermediate layer, the positive electrode active material layer, the negative electrode active material layer) is acquired by FIB-SEM (Focused Ion Beam-Scanning Electron Microscopy). A three-dimensional structure is reconstructed from the cross-sectional image. It is desirable that the cross-sectional pitch be fine. It is desirable that the imaging area be large. For example, the following conditions may be adopted from the viewpoint of the device specifications of FIB-SEM and the measurement time. Fault pitch: 100 nm (it may be smaller than 100 nm). Imaging area size: 50 μm × 30 μm (it may be larger than 50 μm × 30 μm). Magnification: When particles (solids) and voids can be distinguished at the imaging area size as it is, the magnification as it is is adopted. When particles and voids cannot be distinguished, the magnification is adjusted with a magnification of three times or more the diameter of the particles as a guideline. Number of slices: 200 (it may be more than 200). Cross-sectional sample: The cross-sectional sample may be embedded in resin so that particles and voids can be easily distinguished. Next, the three-dimensional structure is analyzed. The transmission coefficient is calculated from the three-dimensional structure by the analysis module "FlowDict" of the simulation software "GeoDict" (manufactured by Math 2 Market). The transmission coefficient is derived using the Stokes equation or the Navier-Stokes equation. Which of the Stokes equation or the Navier-Stokes equation to select may be determined based on the measured data (the relationship between pressure and flow rate in the object). When the relationship between pressure and flow rate is linear, the Stokes equation is considered appropriate. When the relationship between pressure and flow rate is non-linear, the Navier-Stokes equation is considered appropriate. Since the transmission coefficient in the in-plane direction of the object (layered body) is the target, the X-axis or the Y-axis is selected as the axial direction in which the fluid flows. Based on the cutting direction of the cross-sectional sample, the X-axis or the Y-axis is selected.

[0036] "SP value" indicates the solubility parameter. The SP value is obtained by the method of "estimating from physical property values" or the method of "estimating from molecular structure" described in the paper "Consideration on the solubility parameter of additives" in "Paint Research, No. 152 (issued in October 2010)" published by Kansai Paint Co., Ltd. When there is a literature value for the SP value of the object, the literature value may be adopted.

[0037] "D50" indicates the particle diameter at which the integration becomes 50% in the volume-based particle size distribution (cumulative distribution). The particle size distribution can be measured by the laser diffraction method.

[0038] The stoichiometric composition formula represents a representative example of a compound. The compound may have a non-stoichiometric composition. For example, " 2 O 3 " is not limited to a compound having a molar ratio (mole ratio) of " 2 O 3 " of "Al / O = 2 / 3". Unless otherwise specified, "

[0039] " represents a compound containing Al and O in any molar ratio. For example, the compound may be doped with trace elements. A part of Al and O may be substituted with another element.

[0040] <Lithium-ion battery> FIG. 1 is a conceptual diagram showing an example of a lithium-ion battery according to the present embodiment. Battery 1000 is a lithium-ion battery. Battery 1000 includes a power generation element 500 and an electrolytic solution 800. Battery 1000 may further include an exterior body 900.

[0041] <Exterior body> The exterior body 900 may house the power generation element 500 and the electrolytic solution 800. The exterior body 900 can have any form. The exterior body 900 may be, for example, a metal case, a pouch made of a metal foil laminate film, etc. The exterior body 900 can have any outer shape. The exterior body 900 may be, for example, cylindrical, rectangular, flat, coin-shaped, etc. The exterior body 900 may contain, for example, Al, an Al alloy, etc.

[0042] <Power generation element> The power generation element 500 may have a monopolar structure or a bipolar structure. The power generation element 500 includes a positive electrode 10, a separator 30, a negative electrode 20, a first intervening layer 41, and a second intervening layer 42. The power generation element 500 is a laminated type. The power generation element 500 has a lamination direction (Z direction). The lamination direction is parallel to the thickness direction of the positive electrode 10, the separator 30, and the negative electrode 20. The lamination direction may be parallel to the vertical direction. In the lamination direction, the positive electrode 10 and the negative electrode 20 are laminated alternately. The separator 30 is sandwiched between the positive electrode 10 and the negative electrode 20. The positive electrode 10 includes a positive electrode current collector foil 11 and a positive electrode active material layer 12. The negative electrode 20 includes a negative electrode current collector foil 21 and a negative electrode active material layer 22. In the case of a bipolar structure, for example, the positive electrode current collector foil 11 may be attached to the negative electrode current collector foil 21.

[0043] <First intervening layer, second intervening layer> At least one of a first gap G1 and a second gap G2 is formed within the power generation element 500. The first gap G1 is a gap formed between the negative electrode active material layer and the separator 30. The second gap G2 is a gap formed between the positive electrode active material layer and the separator 30. Either one of the first gap G1 or the second gap G2 may be formed. Both the first gap G1 and the second gap G2 may be formed.

[0044] A first intervening layer 41 is disposed in at least one of the first gap G1 and the second gap G2. Further, a second intervening layer 42 is disposed in at least one of the first gap G1 and the second gap G2. For example, the first intervening layer 41 may be disposed in the second gap G2, and the second intervening layer 42 may be disposed in the first gap G1. For example, both the first intervening layer 41 and the second intervening layer 42 may be disposed in the first gap G1, and no intervening layer may be disposed in the second gap G2.

[0045] The first intervening layer 41 has a transmission coefficient different from that of the second intervening layer 42. That is, the relationship of the following formula (1) is satisfied. P1≠P2 (1) P1: Transmission coefficient of the first intervening layer 41 with respect to the electrolyte 800 P2: Transmission coefficient of the second intervening layer 42 with respect to the electrolyte 800

[0046] Since P1 is different from P2 and the first intervening layer 41 and the second intervening layer 42 have a specific positional relationship in the stacking direction, an improvement in high-rate tolerance is expected. The power generation element 500 has a first end E1 at one end in the stacking direction. The power generation element 500 has a second end E2 at the other end in the stacking direction. The first intervening layer 41 is closer to the first end E1 than the second intervening layer 42. The first end E1 may be, for example, the lower end in the vertical direction. The second end E2 may be, for example, the upper end in the vertical direction. The electrolyte 800 may be distributed more on the first end E1 side, for example. Excess liquid may be stored at the first end E1. The "excess liquid" refers to the electrolyte 800 stored outside the power generation element 500.

[0047] P1 may be greater than or less than P2. That is, for example, the relationship of the following formula (2) may be satisfied. P1 > P2 (2)

[0048] P1 is, for example, 1×10 -15 m 2 or more, 1×10 -14 m 2 or more, 2×10 -14 m 2 or more, 3×10 -14 m 2 or more, 4×10 -14 m 2 or more, 5×10 -14 m 2 or more, 6×10 -14 m 2 or more, 7×10 -14 m 2 or more, 8×10 -14 m 2 or more, 9×10 -14 m 2 or more, or 1×10 -13 m 2 or more. P1 is, for example, 1×10 -11 m 2 or less, 1×10 -12 m 2 or less, 1×10 -13 m 2 or less, or 5×10 -14 m 2 or less.

[0049] P2 is, for example, less than 1×10 -15 m 2 and less than or equal to 1×10 -16 m 2 and less than or equal to 9×10 -17 m 2 and less than or equal to 8×10 -17 m 2 and less than or equal to 7×10 -17 m 2 and less than or equal to 6×10 -17 m 2 and less than or equal to 5×10 -17 m 2 and less than or equal to 4×10 -17 m 2 and less than or equal to 3×10 -17m 2 Hereinafter, 2×10 -17 m 2 Hereinafter, or 1×10 -17 m 2 Hereinafter, P2 is, for example, 1×10 -19 m 2 Above, 1×10 -18 m 2 Above, 1×10 -17 m 2 Above, or 5×10 -17 m 2 Above may also be acceptable.

[0050] The thickness of the interlayer is arbitrary. The thickness of the interlayer may be smaller or larger than the thickness of the separator 30. The thickness of the interlayer may be, for example, from 0.1 to 10 μm, from 0.5 to 5 μm, or from 1 to 3 μm. The thickness of the first interlayer 41 may be the same as or different from the thickness of the second interlayer 42.

[0051] The porosity of the interlayer is arbitrary. The porosity of the interlayer may be, for example, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, or 60% or more. The porosity of the interlayer may be, for example, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, or 30% or less. The porosity of the first interlayer 41 may be the same as or different from the porosity of the second interlayer 42.

[0052] The pore distribution of the interlayer is arbitrary. The most frequent value of the pore diameter in the pore distribution may be, for example, 0.1 μm, 0.5 μm or more, 1 μm or more, 1.5 μm or more, 2 μm or more, 2.5 μm or more, or 3 μm or more. The most frequent value of the pore diameter in the pore distribution may be, for example, 5 μm or less, 4 μm or less, 3 μm or less, 2.5 μm or less, or 2 μm or less. The pore distribution of the first interlayer 41 may be the same as or different from the pore distribution of the second interlayer 42.

[0053] For example, an intervening layer may be formed by applying a coating material to the surface of the separator 30. For example, an intervening layer may be formed by applying a coating material to the surface of the positive electrode active material layer 12 or the negative electrode active material layer 22. The composition of the intervening layer is arbitrary. The first intervening layer 41 may include, for example, first inorganic particles and a first binder. The second intervening layer 42 may include, for example, second inorganic particles and a second binder. The second inorganic particles may be the same as or different from the first inorganic particles. The second binder may be the same as or different from the first binder.

[0054] The inorganic particles have electrical insulation properties. The inorganic particles may have, for example, heat resistance. The inorganic particles may include, for example, metal oxides and the like. The first inorganic particles and the second inorganic particles may each independently include at least one selected from the group consisting of, for example, boehmite, alumina, zirconia, titania, magnesia, and silica. The particle shape of the inorganic particles is arbitrary. The particle shape may be, for example, spherical, columnar, flaky, plate-like, needle-like, fibrous, or the like. The size of the inorganic particles is arbitrary. The D50 of the inorganic particles may be, for example, from 0.1 to 10 μm, from 0.5 to 5 μm, or from 1 to 3 μm.

[0055] The blending amount of the binder may be, for example, from 0.1 to 100 parts by mass with respect to 100 parts by mass of the inorganic particles. Between the first intervening layer 41 and the second intervening layer 42, the blending amount of the binder may be the same or different. The binder can have an arbitrary composition. The first binder and the second binder may each independently contain at least one selected from the group consisting of polyolefin resins, cellulose-based polymers, fluorine-based resins, vinyl-based resins, polyalkylene oxides, and acrylic resins. The polyolefin resin may contain, for example, styrene-butadiene rubber (SBR), polyethylene (PE), etc. In SBR, the SP value can change depending on the molar ratio of the styrene monomer and the butadiene monomer. For example, the relationship of "styrene / butadiene = 85 / 15 to 60 / 40", "styrene / butadiene = 85 / 15 to 75 / 25", or "styrene / butadiene = 75 / 25 to 60 / 40" in terms of molar ratio may be satisfied. The cellulose-based polymer may contain, for example, carboxymethyl cellulose (CMC), etc. The fluorine-based resin may contain, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), etc. The vinyl-based resin may contain, for example, polyvinyl alcohol (PVA), etc. The polyalkylene oxide may contain, for example, polyethylene oxide (PEO), etc. The acrylic resin may contain, for example, homopolymers and copolymers of acrylic monomers. The acrylic monomer may contain at least one selected from the group consisting of acrylic acid, methacrylic acid, acrylamide, methacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, methyl methacrylate, 2-ethylhexyl acrylate, and butyl acrylate. The acrylic resin may contain, for example, acrylic resin and methacrylic resin. The first binder and the second binder may each independently contain at least one selected from the group consisting of, for example, PVDF, acrylic resin, methacrylic resin, SBR, PVA, and PE.

[0056] The permeability of the electrolytic solution in the intervening layer can change depending on the SP value of the binder and the blending amount of the binder. For example, the SP values of the first binder and the second binder may satisfy a specific relationship with the SP value of the solvent of the electrolytic solution. For example, the relationship of the following formula (3) may be satisfied. Δ1>Δ2 (3) Δ1: The absolute value of the difference between the SP value of the solvent of the electrolytic solution and the SP value of the first binder Δ2: The absolute value of the difference between the SP value of the solvent of the electrolytic solution and the SP value of the second binder

[0057] The greater the difference in SP values, the more active the entry and exit of the electrolytic solution in the intervening layer tends to be. For example, the relationships of the following formulas (4) and (5) may be satisfied. 2.5≦Δ1 (4) Δ2≦2 (5) Δ1 may be, for example, 3 or more, 3.5 or more, 4 or more, 4.5 or more, 5 or more, or 5.5 or more. Δ1 may be, for example, 10 or less, 8 or less, 6 or less, or 4 or less. Δ2 may be, for example, 1.5 or less, 1 or less, 0.5 or less, or 0.1 or less. Δ2 may be, for example, 0 or more, 0.5 or more, 1 or more, or 1.5 or more.

[0058] <First unit, second unit> The power generation element 500 may consist of one type of unit (repeating unit). The power generation element 500 may include multiple types of units. The power generation element 500 may include, for example, a first unit 101 and a second unit 102. The power generation element 500 may include a plurality of first units 101. The power generation element 500 may include a plurality of second units. The power generation element may include a plurality of first units 101 and a plurality of second units 102. Each of the first unit 101 and the second unit 102 includes a positive electrode 10, a separator 30, and a negative electrode 20. In the stacking direction, the first unit 101 may be closer to the first end E1 than the second unit 102. The first unit 101 may be in contact with the surplus liquid (electrolyte 800). The second unit 102 may not be in contact with the surplus liquid.

[0059] The first unit 101 may include a first intervening layer 41 in at least one of the first gap G1 and the second gap G2. The second unit 102 may include a second intervening layer 42 in at least one of the first gap G1 and the second gap G2. For example, a relationship of "P1 > P2" may be satisfied between the permeation coefficient (P1) of the first intervening layer 41 and the permeation coefficient (P2) of the second intervening layer 42.

[0060] The configuration of the intervening layer in the first unit 101 and the second unit 102 may be changed according to the relationship between the permeation coefficient (Pc) of the positive electrode active material layer 12 and the permeation coefficient (Pa) of the negative electrode active material layer 22.

[0061] For example, the first unit 101 may have a configuration in which the salt concentration of the electrolyte 800 can be equalized inside and outside the power generation element 500. For example, in the first unit 101, the intervening layer may be arranged such that the total value of the salt concentration of the electrolyte 800 flowing out from the positive electrode active material layer 12 side and the salt concentration of the electrolyte 800 flowing out from the negative electrode active material layer 22 side approximates the salt concentration of the surplus liquid.

[0062] Figure 2 is a conceptual diagram showing a first example of the first unit. The description "Pa >> Pc" indicates that the transmission coefficient (Pa) of the negative electrode active material layer 22 is much larger than the transmission coefficient (Pc) of the positive electrode active material layer 12. When the relationship "Pa >> Pc" is satisfied, for example, Pa may be 2 times or more, 5 times or more, 10 times or more, 20 times or more, 50 times or more, or 100 times or more of Pc. In the first unit 101, for example, when the relationship "Pa >> Pc" is satisfied, the first intervening layer 41 may be disposed in the second gap G2, and the second intervening layer 42 may be disposed in the first gap G1. A relationship such as "P1 > P2" may be satisfied between the transmission coefficient (P1) of the first intervening layer 41 and the transmission coefficient (P2) of the second intervening layer 42.

[0063] Figure 3 is a conceptual diagram showing a second example of the first unit. In the first unit 101, for example, when the relationship "Pa << Pc" is satisfied, the second intervening layer 42 may be disposed in the second gap G2, and the first intervening layer 41 may be disposed in the first gap G1. A relationship such as "P1 > P2" may be satisfied between the transmission coefficient (P1) of the first intervening layer 41 and the transmission coefficient (P2) of the second intervening layer 42.

[0064] Figure 4 is a conceptual diagram showing a third example of the first unit. The description "Pa ≒ Pc" indicates that the transmission coefficient (Pc) of the positive electrode active material layer 12 is approximated to the transmission coefficient (Pa) of the negative electrode active material layer 22. When the relationship "Pa ≒ Pc" is satisfied, for example, a relationship such as "0.75 ≦ Pa / Pc ≦ 1.25" or "0.9 ≦ Pa / Pc ≦ 1.1" may be satisfied. In the first unit 101, for example, when the relationship "Pa ≒ Pc" is satisfied, the first intervening layer 41 may be disposed in the first gap G1 and the second gap G2, respectively.

[0065] Figure 5 is a conceptual diagram showing a fourth example of the first unit. In the first unit 101, for example, when the relationship "Pa >> Pc" is satisfied, the first intervening layer 41 may be disposed only in the second gap G2.

[0066] FIG. 6 is a conceptual diagram showing a fifth example of the first unit. In the first unit 101, for example, when the relationship of "Pa << Pc" is satisfied, the first intervening layer 41 may be disposed only in the first gap G1.

[0067] FIG. 7 is a conceptual diagram showing a sixth example of the first unit. In the first unit 101, for example, both the first intervening layer 41 and the second intervening layer 42 may be disposed only in the second gap G2. The second intervening layer 42 may be disposed between the first intervening layer 41 and the positive electrode active material layer 12. The first intervening layer 41 may be disposed between the second intervening layer 42 and the positive electrode active material layer 12. For example, a relationship of "P1 > P2" may be satisfied between the transmission coefficient (P1) of the first intervening layer 41 and the transmission coefficient (P2) of the second intervening layer 42.

[0068] FIG. 8 is a conceptual diagram showing a seventh example of the first unit. In the first unit 101, for example, both the first intervening layer 41 and the second intervening layer 42 may be disposed only in the first gap G1. The second intervening layer 42 may be disposed between the first intervening layer 41 and the negative electrode active material layer 22. The first intervening layer 41 may be disposed between the second intervening layer 42 and the negative electrode active material layer 22. For example, a relationship of "P1 > P2" may be satisfied between the transmission coefficient (P1) of the first intervening layer 41 and the transmission coefficient (P2) of the second intervening layer 42.

[0069] The second unit 102 may have a configuration in which, for example, the electrolyte 800 hardly flows out. FIG. 9 is a conceptual diagram showing a first example of the second unit. In the second unit 102, for example, when the relationship of "Pa >> Pc" is satisfied, the second intervening layer 42 may be disposed in the first gap G1.

[0070] FIG. 10 is a conceptual diagram showing a second example of the second unit. In the second unit 102, for example, both the first intervening layer 41 and the second intervening layer 42 may be disposed only in the first gap G1. The second intervening layer 42 may be disposed between the first intervening layer 41 and the negative electrode active material layer 22. The first intervening layer 41 may be disposed between the second intervening layer 42 and the negative electrode active material layer 22. For example, a relationship of "P1 > P2" may be satisfied between the transmission coefficient (P1) of the first intervening layer 41 and the transmission coefficient (P2) of the second intervening layer 42.

[0071] FIG. 11 is a conceptual diagram showing a third example of the second unit. In the second unit 102, for example, both the first intervening layer 41 and the second intervening layer 42 may be disposed only in the second gap G2. The second intervening layer 42 may be disposed between the first intervening layer 41 and the positive electrode active material layer 12. The first intervening layer 41 may be disposed between the second intervening layer 42 and the positive electrode active material layer 12. For example, a relationship of "P1 > P2" may be satisfied between the transmission coefficient (P1) of the first intervening layer 41 and the transmission coefficient (P2) of the second intervening layer 42.

[0072] <Positive Electrode> The positive electrode 10 includes a positive electrode current collector foil 11 and a positive electrode active material layer 12. The positive electrode current collector foil 11 supports the positive electrode active material layer 12. The positive electrode current collector foil 11 may have a thickness of, for example, 5 to 50 μm. The positive electrode current collector foil 11 may contain at least one selected from the group consisting of, for example, Al, Mn, Ti, Fe, and Cr. The positive electrode current collector foil 11 may include, for example, Al foil, Al alloy foil, Ti foil, stainless steel (SUS) foil, etc.

[0073] An intermediate layer may be formed between the positive electrode current collector foil 11 and the positive electrode active material layer 12. The intermediate layer does not contain a positive electrode active material. The intermediate layer may have a thickness of, for example, 0.1 to 5 μm. The intermediate layer may include, for example, a conductive material, an insulating material, a binder, etc. The conductive material may include, for example, carbon black, etc. The insulating material may include, for example, alumina, boehmite, aluminum hydroxide, etc. The binder may include, for example, PVDF, etc.

[0074] The positive electrode active material layer 12 is disposed on the surface of the positive electrode current collector foil 11. The positive electrode active material layer 12 may be disposed on only one side of the positive electrode current collector foil 11. The positive electrode active material layer 12 may be disposed on both sides of the positive electrode current collector foil 11. The thickness of the positive electrode active material layer 12 may be, for example, from 10 to 1000 μm, from 50 to 500 μm, or from 100 to 300 μm. The positive electrode active material layer 12 contains a positive electrode active material. The positive electrode active material layer 12 may further contain, for example, a conductive material and a binder.

[0075] The blending amount of the conductive material may be, for example, from 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The conductive material may contain any component. The conductive material may contain, for example, at least one selected from the group consisting of graphite, acetylene black (AB), Ketjen black (registered trademark), vapor grown carbon fiber (VGCF), carbon nanotube (CNT), and graphene flake (GF). The CNT may contain at least one selected from the group consisting of single-walled CNT (SWCNT) and multi-walled CNT (MWCNT).

[0076] The blending amount of the binder may be, for example, from 0.1 to 10 parts by mass with respect to 100 parts by mass of the positive electrode active material. The binder may contain any component. The binder may contain, for example, at least one selected from the group consisting of PVDF, PVDF-HFP, PTFE, CMC, polyacrylic acid (PAA), PVA, polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0077] The positive electrode active material layer 12 may further contain, for example, an inorganic filler, an organic filler, a solid electrolyte, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The positive electrode active material layer 12 may contain, for example, polyoxyethylene allyl phenyl ether phosphate, zeolite, silane coupling agent, MoS 2 , WO 3 etc.

[0078] ·Positive electrode active material The positive electrode active material may be, for example, particulate. The D50 of the positive electrode active material may be, for example, from 1 to 30 μm, from 10 to 20 μm, or from 1 to 10 μm. The positive electrode active material may contain any component. The positive electrode active material may contain, for example, a transition metal oxide, a polyanion compound, etc. Within one particle (positive electrode active material), the composition may be uniform or non-uniform. For example, the composition may vary from the surface to the center of the particle. The change in composition may be continuous or discontinuous (stepwise).

[0079] ·Transition metal oxide (space group R-3m) The transition metal oxide may have any crystal structure. The transition metal oxide may contain, for example, a crystal structure belonging to the space group R-3m, etc. For example, a compound represented by the general formula "LiMO 2 " may have a crystal structure belonging to the space group R-3m. The transition metal oxide may be represented, for example, by the following general formula. Li 1-a Ni x M 1-x O 2 In the formula, the relationship -0.5 ≦ a ≦ 0.5, 0 ≦ x ≦ 1 is satisfied. M may contain, for example, at least one selected from the group consisting of Co, Mn, and Al. For example, the relationship 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x ≦ 1 may be satisfied. For example, the relationship -0.4 ≦ a ≦ 0.4, -0.3 ≦ a ≦ 0.3, -0.2 ≦ a ≦ 0.2, or -0.1 ≦ a ≦ 0.1 may be satisfied.

[0080] The transition metal oxide is, for example, LiCoO 2 、LiMnO 2 、LiNi 0.9 Co 0.1 O 2 、LiNi 0.9 Mn0.1 O 2 and may also contain at least one selected from the group consisting of LiNiO 2 .

[0081] ·NCM The transition metal oxide may be represented, for example, by the following general formula. The compound represented by the following general formula may also be referred to as "NCM". Li 1-a Ni x Co y Mn z O 2 In the formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationship of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x < 1 may be satisfied. For example, the relationship of 0 < y ≦ 0.1, 0.1 ≦ y ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0.3 ≦ y ≦ 0.4, 0.4 ≦ y ≦ 0.5, 0.5 ≦ y ≦ 0.6, 0.6 ≦ y ≦ 0.7, 0.7 ≦ y ≦ 0.8, 0.8 ≦ y ≦ 0.9, or 0.9 ≦ y < 1 may be satisfied. For example, the relationship of 0 < z ≦ 0.1, 0.1 ≦ z ≦ 0.2, 0.2 ≦ z ≦ 0.3, 0.3 ≦ z ≦ 0.4, 0.4 ≦ z ≦ 0.5, 0.5 ≦ z ≦ 0.6, 0.6 ≦ z ≦ 0.7, 0.7 ≦ z ≦ 0.8, 0.8 ≦ z ≦ 0.9, or 0.9 ≦ z < 1 may be satisfied.

[0082] NCM is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 、LiNi 0.4 Co 0.3 Mn 0.3 O 2 、LiNi 0.3 Co 0.4 Mn 0.3 O 2 、LiNi 0.3 Co 0.3 Mn 0.4 O 2 、LiNi0.5 Co 0.2 Mn 0.3 O 2 、 LiNi 0.5 Co 0.3 Mn 0.2 O 2 、 LiNi 0.5 Co 0.4 Mn 0.1 O 2 、 LiNi 0.5 Co 0.1 Mn 0.4 O 2 、 LiNi 0.6 Co 0.2 Mn 0.2 O 2 、 LiNi 0.6 Co 0.3 Mn 0.1 O 2 、 LiNi 0.6 Co 0.1 Mn 0.3 O 2 、 LiNi 0.7 Co 0.1 Mn 0.2 O 2 、 LiNi 0.7 Co 0.2 Mn 0.1 O 2 、 LiNi 0.8 Co 0.1 Mn 0.1 O 2 、 and, LiNi 0.9 Co 0.05 Mn 0.05 O 2 It may contain at least one selected from the group consisting of.

[0083] ·NCA The transition metal oxide may be represented by, for example, the following general formula. The compound represented by the following general formula may also be referred to as "NCA". Li 1-a Ni x Co y Al z O 2 In the formula, the relationships of -0.5 ≦ a ≦ 0.5, 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1 are satisfied. For example, the relationships of 0 < x ≦ 0.1, 0.1 ≦ x ≦ 0.2, 0.2 ≦ x ≦ 0.3, 0.3 ≦ x ≦ 0.4, 0.4 ≦ x ≦ 0.5, 0.5 ≦ x ≦ 0.6, 0.6 ≦ x ≦ 0.7, 0.7 ≦ x ≦ 0.8, 0.8 ≦ x ≦ 0.9, or 0.9 ≦ x < 1 may be satisfied. For example, the relationships of 0 < y ≦ 0.1, 0.1 ≦ y ≦ 0.2, 0.2 ≦ y ≦ 0.3, 0.3 ≦ y ≦ 0.4, 0.4 ≦ y ≦ 0.5, 0.5 ≦ y ≦ 0.6, 0.6 ≦ y ≦ 0.7, 0.7 ≦ y ≦ 0.8, 0.8 ≦ y ≦ 0.9, or 0.9 ≦ y < 1 may be satisfied. For example, the relationships of 0 < z ≦ 0.1, 0.1 ≦ z ≦ 0.2, 0.2 ≦ z ≦ 0.3, 0.3 ≦ z ≦ 0.4, 0.4 ≦ z ≦ 0.5, 0.5 ≦ z ≦ 0.6, 0.6 ≦ z ≦ 0.7, 0.7 ≦ z ≦ 0.8, 0.8 ≦ z ≦ 0.9, or 0.9 ≦ z < 1 may be satisfied.

[0084] NCA may be, for example, LiNi 0.7 Co 0.1 Al 0.2 O 2 、LiNi 0.7 Co 0.2 Al 0.1 O 2 、LiNi 0.8 Co 0.1 Al 0.1 O 2 、LiNi 0.8 Co 0.17 Al 0.03 O 2 、LiNi 0.8 Co 0.15 Al 0.05 O 2 、and may contain at least one selected from the group consisting of LiNi 0.9 Co 0.05 Al 0.05 O 2

[0085] · Multi-component system The positive electrode active material may contain, for example, two or more types of NCM or the like. The positive electrode active material may contain, for example, NCM(0.6≦x) and NCM(x<0.6). "NCM(0.6≦x)" refers to a compound in the general formula "Li 1-a Ni x Co y Mn z O 2 " where x (Ni ratio) is 0.6 or more. NCM(0.6≦x) may be referred to as, for example, a "high nickel material". NCM(0.6≦x) contains, for example, LiNi 0.8 Co 0.1 Mn 0.1 O 2 and the like. "NCM(x<0.6)" refers to a compound in the general formula "Li 1-a Ni x Co y Mn z O 2 " where x (Ni ratio) is less than 0.6. NCM(x<0.6) contains, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 and the like. The mixing ratio (mass ratio) of NCM(0.6≦x) and NCM(x<0.6) may be, for example, "NCM(0.6≦x) / NCM(x<0.6)=9 / 1 to 1 / 9", "NCM(0.6≦x) / NCM(x<0.6)=9 / 1 to 4 / 6", or "NCM(0.6≦x) / NCM(x<0.6)=9 / 1 to 3 / 7".

[0086] The positive electrode active material may contain, for example, NCA and NCM. The mixing ratio (mass ratio) of NCA and NCM may be, for example, "NCA / NCM=9 / 1 to 1 / 9", "NCA / NCM=9 / 1 to 4 / 6", or "NCA / NCM=9 / 1 to 3 / 7". The Ni ratio may be the same or different between NCA and NCM. The Ni ratio of NCA may be higher than the Ni ratio of NCM. The Ni ratio of NCA may be lower than the Ni ratio of NCM.

[0087] · Transition metal oxide (space group C2 / m) The transition metal oxide may include, for example, a crystal structure belonging to the space group C2 / m. The transition metal oxide may be represented by, for example, the following general formula. Li 2 MO 3 In the formula, M may include at least one selected from the group consisting of, for example, Ni, Co, Mn, and Fe. The positive electrode active material may be, for example, LiMO 2 (space group R-3m) and Li 2 MO 3 (space group C2 / m). The positive electrode active material may include, for example, a mixture of LiMO 2 and Li 2 MO 3 and a solid solution (Li 2 MO 3 -LiMO 2 ), etc.

[0088] · Transition metal oxide (space group Fd-3m) The transition metal oxide may include, for example, a crystal structure belonging to the space group Fd-3m. The transition metal oxide may be represented by, for example, the following general formula. LiMn 2-x M x O 4 In the formula, the relationship of 0 ≦ x ≦ 2 is satisfied. M may include at least one selected from the group consisting of, for example, Ni, Fe, and Zn.

[0089] LiM 2 O 4 (space group Fd-3m) may include, for example, at least one selected from the group consisting of LiMn 2 O 4 , and LiMn 1.5 Ni 0.5 O 4 . The positive electrode active material may include, for example, a mixture of LiMO 2 (space group R-3m) and LiM 2 O 4 (space group Fd-3m). LiMO 2 (space group R-3m) and LiM2 O 4 (Space group Fd-3m) The mixing ratio (mass ratio) with, for example, is "LiMO 2 / LiM 2 O 4 = 9 / 1 to 9 / 1", "LiMO 2 / LiM 2 O 4 = 9 / 1 to 5 / 5", or "LiMO 2 / LiM 2 O 4 = 9 / 1 to 7 / 3".

[0090] · Polyanion compound The polyanion compound may contain, for example, phosphates (e.g., LiFePO 4 etc.), silicates, borates, etc. The polyanion compound may be represented, for example, by the following general formula groups. LiMPO 4 Li 2-x MPO 4 F Li 2 MSiO 4 LiMBO 3 In the above general formula groups, M may contain at least one selected from the group consisting of, for example, Fe, Mn, and Co. In the general formula "Li 2-x MPO 4 F", for example, the relationship 0 ≦ x ≦ 2 may be satisfied.

[0091] The positive electrode active material may contain, for example, a mixture of LiMO 2 (space group R-3m) and a polyanion compound. The mixing ratio (mass ratio) of LiMO 2 (space group R-3m) and the polyanion compound is, for example, "LiMO 2 / Polyanion compound = 9 / 1 to 9 / 1", "LiMO 2 / Polyanion compound = 9 / 1 to 5 / 5", or "LiMO 2 / Polyanion compound = 9 / 1 to 7 / 3".

[0092] · Dopant A dopant may be added to the positive electrode active material. The dopant may be diffused throughout the particles or may be locally distributed. For example, the dopant may be unevenly distributed on the particle surface. The dopant may be a substitutional solid solution atom or an interstitial solid solution atom. The addition amount of the dopant (mole fraction with respect to the entire positive electrode active material) may be, for example, from 0.01 to 5%, from 0.1 to 3%, or from 0.1 to 1%. One or more kinds of dopants may be added. Two or more kinds of dopants may form a complex.

[0093] The dopant may contain, for example, at least one selected from the group consisting of B, C, N, halogen, Si, Na, Mg, Al, Mn, Co, Cr, Sc, Ti, V, Cu, Zn, Ga, Ge, Se, Sr, Y, Zr, Nb, Mo, In, Pb, Bi, Sb, Sn, W, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and actinoid.

[0094] For example, a combination of "Zr, Mg, W, Sm", a combination of "Ti, Mn, Nb, Si, Mo", or a combination of "Er, Mg" may be added to NCA. For example, Ti may be added to NCM. For example, a combination of "Zr, W", a combination of "Si, W", or a combination of "Zr, W, Al, Ti, Co" may be added to NCM.

[0095] · Surface coating The positive electrode active material may form composite particles. The composite particles may include, for example, core particles and a coating layer. The core particles contain the positive electrode active material. The coating layer covers at least a part of the surface of the core particles. The thickness of the coating layer may be, for example, 1 to 3000 nm, 5 to 2000 nm, 10 to 1000 nm, 10 to 100 nm, or 10 to 50 nm. The thickness of the coating layer can be measured, for example, in an SEM image of the particle cross-section or the like. That is, a sample is prepared by embedding the composite particles in a resin material. The sample is subjected to cross-section machining by an ion milling apparatus. The cross-section of the sample is observed by SEM. For 10 composite particles, the thickness of the coating layer is measured in 20 fields of view each. The arithmetic mean of the thicknesses at a total of 200 locations is adopted.

[0096] The ratio of the portion of the surface of the core particles covered by the coating layer is also referred to as the "coverage rate". The coverage rate may be, for example, 1% or more, 10% or more, 30% or more, 50% or more, or 70% or more. The coverage rate may be, for example, 100% or less, 90% or less, or 80% or less.

[0097] The coverage rate can be measured, for example, by XPS (X-ray Photoelectron Spectroscopy). A powder sample composed of composite particles is set in the XPS. Narrow scan analysis is performed. The measurement data is processed by analysis software. By analyzing the measurement data, a plurality of types of elements are detected. From the area of each peak, the ratio of each detected element is obtained. The coverage rate is obtained by the following formula. γ={I 1 / (I 0 +I 1 )}×100 γ: Coverage rate [%] I 0 : Ratio of elements derived from the core particles I 1 : Ratio of elements derived from the coating layer For example, when the core particles contain NCM, I 0 indicates the total element ratio of "Ni, Co, Mn". For example, when the core particles contain NCA, I0 represents the total element ratio of "Ni, Co, Al". For example, when the coating layer contains P and B, I 1 represents the total element ratio of "P, B".

[0098] The coating layer may contain any component. The coating layer may contain, for example, a single substance, an organic substance, an inorganic acid salt, an organic acid salt, a hydroxide, an oxide, a carbide, a nitride, a sulfide, a halide, etc. The coating layer may contain, for example, B, Al, W, Zr, Ti, Co, F, a lithium compound (such as Li 2 CO 3 , LiHCO 3 , LiOH, Li 2 O, etc.), tungsten oxide (such as WO 3 , etc.), titanium oxide (such as TiO 2 , etc.), zirconium oxide (such as ZrO 2 ), boron oxide, boron phosphate (such as BPO 4 , etc.), aluminum oxide (such as Al 2 O 3 , etc.), boehmite, aluminum hydroxide, phosphate [such as Li 3 PO 4、 (NH 4 ) 3 PO 4 , AlPO 4 , etc.), borate (such as Li 2 B 4 O 7 , LiBO 3 , etc.), polyacrylate (Li salt, Na salt, NH 4 salt, etc.), acetate (such as Li salt, etc.), CMC (CMC-Na, CMC-Li, CMC-NH 4 , etc.), LiNbO 3、 Li 2 TiO 3 , and at least one selected from the group consisting of Li-containing halides (such as LiAlCl 4 , LiTiAlF 6 , LiYBr 6 , LiYCl 6 , etc.).

[0099] ·Hollow particles / Solid particles Both hollow particles and solid particles are secondary particles. A "hollow particle" means that in a cross-sectional image, the ratio of the area of the cavity in the central part is 30% or more of the cross-sectional area of the entire particle. The ratio of the cavity in the hollow particle may be, for example, 40% or more, 50% or more, or 60% or more. A "solid particle" means that in the cross-sectional image of the particle, the ratio of the area of the cavity in the central part is less than 30% of the cross-sectional area of the entire particle. The ratio of the cavity in the solid particle may be, for example, 20% or less, 10% or less, or 5% or less. The positive electrode active material may be hollow particles or solid particles. A mixture of hollow particles and solid particles may also be used. The mixing ratio (mass ratio) of hollow particles and solid particles may be, for example, "hollow particles / solid particles = 1 / 9 to 9 / 1", "hollow particles / solid particles = 2 / 8 to 8 / 2", "hollow particles / solid particles = 3 / 7 to 7 / 3", or "hollow particles / solid particles = 4 / 6 to 6 / 4".

[0100] · Large particles / small particles The active material may have, for example, a unimodal particle size distribution (number-based). The active material may have, for example, a multimodal particle size distribution. The active material may have, for example, a bimodal particle size distribution. That is, the active material may contain large particles and small particles. When the particle size distribution is bimodal, the particle diameter corresponding to the peak top with the larger particle diameter is regarded as the particle diameter of the large particles (d L ). The particle diameter corresponding to the peak top with the smaller particle diameter is regarded as the particle diameter of the small particles (d S ). The particle size ratio (d L / d S ) may be, for example, 2 to 10, 2 to 5, or 2 to 4. d L may be, for example, 8 to 20 μm, or 8 to 15 μm. d S may be, for example, 1 to 10 μm, or 1 to 5 μm.

[0101] For example, the particle size distribution may be subjected to peak separation processing by waveform analysis software. The ratio of the peak area (S L ) derived from large particles to the peak area (S S ) derived from small particles is, for example, "SL / S S = 1 / 9 to 9 / 1, "S L / S S = 5 / 5 to 9 / 1" or "S L / S S = 7 / 3 to 9 / 1" may also be applicable.

[0102] The particle size distribution based on the number is measured by microscopy. A plurality of cross-sectional samples are taken from the active material layer. The cross-sectional sample may include, for example, a cross-section perpendicular to the surface of the active material layer. For example, the observation surface is cleaned by ion milling or the like. The cross-sectional sample is observed by SEM. The observation magnification is adjusted so that 10 to 100 particles fit within the observation field of view. The Feret diameter of all the particles in the image is measured. The "Feret diameter" indicates the distance between the two farthest points on the contour line of the particle. By observing a plurality of cross-sectional samples, a total of more than 1000 Feret diameters are obtained. A particle size distribution based on the number is created from more than 1000 Feret diameters.

[0103] A bimodal particle size distribution can be formed by mixing two types of particles. The two types of particles have different particle size distributions from each other. For example, the two types of particles may have different D50 values from each other. The measurement sample is a powder. For example, the D50 of the large particles may be 8 to 20 μm, or 8 to 15 μm. For example, the D50 of the small particles may be 1 to 10 μm, or 1 to 5 μm. The ratio of the D50 of the large particles to the D50 of the small particles may be, for example, 2 to 10, 2 to 5, or 2 to 4. The mixing ratio (mass ratio) of the large particles to the small particles may be, for example, "large particles / small particles = 1 / 9 to 9 / 1", "large particles / small particles = 5 / 5 to 9 / 1", or "large particles / small particles = 7 / 3 to 9 / 1".

[0104] Note that the large particles and the small particles may have the same composition or different compositions from each other. For example, the large particles may be NCA and the small particles may be NCM. For example, the large particles may be NCM (0.6 ≤ x) and the small particles may be NCM (x < 0.6).

[0105] <Negative electrode> The negative electrode 20 includes a negative electrode current collector foil 21 and a negative electrode active material layer 22. The negative electrode current collector foil 21 supports the negative electrode active material layer 22. The negative electrode current collector foil 21 may have a thickness of, for example, 5 to 50 μm. The negative electrode current collector foil 21 may contain at least one selected from the group consisting of, for example, Cu and Ni. The negative electrode current collector foil 21 may contain, for example, Cu foil, Cu alloy foil, Ni foil, etc.

[0106] The negative electrode active material layer 22 is disposed on the surface of the negative electrode current collector foil 21. The negative electrode active material layer 22 may be disposed on only one side of the negative electrode current collector foil 21. The negative electrode active material layer 22 may be disposed on both sides of the negative electrode current collector foil 21. The thickness of the negative electrode active material layer 22 may be, for example, 10 to 1000 μm, 50 to 500 μm, or 100 to 300 μm. The negative electrode active material layer 22 contains a negative electrode active material. The negative electrode active material layer 22 may further contain, for example, a conductive material, a binder, etc.

[0107] The blending amount of the conductive material may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material. The conductive material may contain any components. The conductive material may contain at least one selected from the group consisting of, for example, AB, Ketjenblack (registered trademark), VGCF, CNT, and GF.

[0108] The blending amount of the binder may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material. The binder may contain any components. The binder is, for example, SBR, acrylate butadiene rubber (ABR), sodium alginate, CMC (CMC-H, CMC-Na, CMC-Li, CMC-NH 4etc.), PAA (such as PAA-H, PAA-Na, PAA-Li, etc.), polyacrylonitrile (PAN), PVDF, PTFE, acrylic resin, methacrylic resin, PVP, PVA, and may contain at least one selected from the group consisting of these derivatives. For example, the description of "CMC-Na" indicates the Na salt of CMC. For example, the description of "CMC-H" indicates the acid form of CMC. The same applies to "PAA-Na" and the like.

[0109] The negative electrode active material layer 22 may further contain, for example, an inorganic filler, an organic filler, a solid electrolyte, a surface modifier, a dispersant, a lubricant, a flame retardant, a protective agent, a flux, a coupling agent, an adsorbent, etc. The negative electrode active material layer 22 may contain, for example, a layered silicate (such as smectite, montmorillonite, bentonite, hectorite, etc.), an inorganic filler (such as solid alumina, hollow silica, boehmite, etc.), a polysiloxane compound, etc.

[0110] ·Negative electrode active material The negative electrode active material may be, for example, particulate or sheet-like. The D50 of the negative electrode active material may be, for example, from 1 to 30 μm, from 10 to 20 μm, or from 1 to 10 μm.

[0111] ·Carbon-based active material The negative electrode active material may contain, for example, a carbon-based active material. The carbon-based active material may contain at least one selected from the group consisting of graphite, soft carbon, and hard carbon. "Graphite" is a general term for natural graphite and artificial graphite. Graphite may be a mixture of natural graphite and artificial graphite. The mixing ratio (mass ratio) may be, for example, "natural graphite / artificial graphite = 1 / 9 to 9 / 1", "natural graphite / artificial graphite = 2 / 8 to 8 / 2", or "natural graphite / artificial graphite = 3 / 7 to 7 / 3".

[0112] Graphite may contain a dopant. The dopant may contain, for example, at least one selected from the group consisting of B, N, P, Li, and Ca. The addition amount may be, for example, from 0.01 to 5%, from 0.1 to 3%, or from 0.1 to 1% in mole fraction.

[0113] The surface of the graphite may be coated with, for example, amorphous carbon. The surface of the graphite may be coated with, for example, a different material. The different material may contain, for example, at least one selected from the group consisting of P, W, Al, and O. The different material may be, for example, Al(OH) 3 , AlOOH, Al 2 O 3 , WO 3 , Li 2 CO 3 , LiHCO 3、 and, Li 3 PO 4 and may contain at least one selected from the group consisting of.

[0114] · Alloy-based active material The negative electrode active material may contain, for example, an alloy-based active material. The negative electrode active material may contain, for example, at least one selected from the group consisting of Si, Li silicate, SiO, Si-based alloy, Sn, SnO, and Sn-based alloy.

[0115] SiO may be represented by, for example, the following general formula. SiO x In the formula, the relationship of 0 < x < 2 is satisfied. For example, the relationship of 0.5 ≤ x ≤ 1.5, or 0.8 ≤ x ≤ 1.2 may be satisfied.

[0116] Li silicate is, for example, Li 4 SiO 4 , Li 2 SiO 3 , Li 2 Si 2 O 5 , and, Li 8 SiO 6It may contain at least one selected from the group consisting of. The negative electrode active material may contain, for example, a mixture of Si and Li silicate. The mixing ratio (mass ratio) may be, for example, "Si / Li silicate = 1 / 9 to 9 / 1", "Si / Li silicate = 2 / 8 to 8 / 2", "Si / Li silicate = 3 / 7 to 7 / 3", or "Si / Li silicate = 4 / 6 to 6 / 4".

[0117] The alloy-based active material (Si, SiO, etc.) may contain additives. The additives may be, for example, substitutional solid solution atoms or interstitial solid solution atoms. The additives may be deposits adhering to the surface of the alloy-based active material. The deposits may be, for example, simple substances, oxides, carbides, nitrides, halides, etc. The addition amount may be, in mole fraction, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1%. The additives may contain, for example, at least one selected from the group consisting of Li, Na, K, Rb, Be, Mg, Ca, Sr, Fe, Ba, B, Al, Ga, In, C, Ge, Sn, Pb, N, P, As, Y, Sb, and S. That is, Mg and Na may be doped into SiO. For example, Mg silicate, Na silicate, etc. may be formed. For example, boron oxide (e.g., B 2 O 3 etc.), yttrium oxide (e.g., Y 2 O 3 etc.) etc. may be added.

[0118] ·Si-C composite material The negative electrode active material may contain, for example, a composite material of a carbon-based active material (graphite, etc.) and an alloy-based active material (Si, etc.). The composite material containing Si and carbon may also be referred to as "Si-C composite material". For example, Si fine particles may be dispersed in carbon particles. For example, Si fine particles may be dispersed in graphite particles. For example, Li silicate particles may be coated with a carbon material (amorphous carbon, etc.).

[0119] ·Other active materials The negative electrode active material may be, for example, Li metal, Li-based alloy, and Li4 Ti 5 O 12 It may contain at least one selected from the group consisting of. The negative electrode active material may contain, for example, a Li foil or the like.

[0120] <Separator> The separator 30 can separate the positive electrode 10 from the negative electrode 20. The separator 30 has electrical insulation. The separator 30 may contain, for example, a resin film. The resin film is porous. The resin film may contain, for example, a microporous membrane, a non-woven fabric, or the like. The resin film contains a resin skeleton. The resin skeleton may be continuously reticulated, for example. Pores are formed in the gaps of the resin skeleton. The average pore diameter of the resin film may be, for example, from 0.01 to 1 μm, or from 0.1 to 0.5 μm. The "average pore diameter" can be measured by the mercury intrusion method. The Gurley value of the resin film may be, for example, from 50 to 250 s / 100 cm 3 It may be. The "Gurley value" can be measured by the Gurley test method.

[0121] The resin film may contain at least one selected from the group consisting of, for example, olefin resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, acrylic resins, and polyester resins. The resin film may contain at least one selected from the group consisting of, for example, PE, polypropylene (PP), polyamide (PA), polyamideimide (PAI), polyimide (PI), aromatic polyamide (aramid), polyphenylene ether (PPE), and derivatives thereof. The resin film can be formed, for example, by a stretching method, a phase separation method, or the like. The thickness of the resin film may be, for example, from 5 to 50 μm, or from 10 to 25 μm.

[0122] The resin film may have, for example, a single-layer structure. The resin film may be composed of, for example, a PE layer. The backbone of the PE layer is formed by PE. The PE layer may have a shutdown function. The resin film may have, for example, a multilayer structure. The resin film may include, for example, a PP layer and a PE layer. The backbone of the PP layer is formed by PP. The resin film may have, for example, a three-layer structure. The resin film may be formed, for example, by laminating a PP layer, a PE layer, and a PP layer in this order. The thickness of the PE layer may be, for example, 5 to 20 μm. The thickness of the PP layer may be, for example, 3 to 10 μm.

[0123] <Electrolyte solution> The electrolyte solution is a liquid electrolyte. The electrolyte solution contains a supporting salt and a solvent. The supporting salt is also referred to as a "supporting electrolyte". The concentration of the supporting salt (salt concentration) may be, for example, 0.5 to 1 mol / L, 1 to 1.5 mol / L, 1.5 to 2 mol / L, 2 to 2.5 mol / L, or 2.5 to 3 mol / L. "mol / L" may also be denoted as "M". The supporting salt may contain, for example, inorganic acid salts, imide salts, oxalato complexes, halides, etc. The supporting salt may be, for example, LiPF 6 , LiBF 4 , LiClO 4 , LiAsF 6 , LiSbF 6 , LiN(SO 2 F) 2 "LiFSI", LiN(SO 2 CF 3 ) 2 "LiTFSI", LiB(C 2 O 4 ) 2 "LiBOB", LiBF 2 (C 2 O 4 ) "LiDFOB", LiPF 2 (C 2 O 4 ) 2 "LiDFOP", LiPO 2 F 2 , FSO 3It may contain at least one selected from the group consisting of Li, LiI, LiBr, and derivatives thereof.

[0124] The electrolytic solution may contain, for example, a carbonate-based solvent (carbonate ester-based solvent). The solvent may contain, for example, cyclic carbonates, chain carbonates, fluorinated carbonates, etc. The solvent may contain at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (FEC), difluoroethylene carbonate, 4,4-difluoroethylene carbonate, trifluoroethylene carbonate, perfluoroethylene carbonate, fluoropropylene carbonate, difluoropropylene carbonate, and derivatives thereof.

[0125] The solvent may contain a cyclic carbonate (such as EC, PC, FEC, etc.) and a chain carbonate (such as EMC, DMC, DEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate and the chain carbonate may be, for example, "cyclic carbonate / chain carbonate = 1 / 9 to 4 / 6", "cyclic carbonate / chain carbonate = 2 / 8 to 3 / 7", or "cyclic carbonate / chain carbonate = 3 / 7 to 4 / 6".

[0126] The solvent may contain a cyclic carbonate (such as EC, PC, etc.) and a fluorinated cyclic carbonate (such as FEC, etc.). The mixing ratio (volume ratio) of the cyclic carbonate and the fluorinated cyclic carbonate may be, for example, "cyclic carbonate / fluorinated cyclic carbonate = 99 / 1 to 90 / 10", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 1 / 9", "cyclic carbonate / fluorinated cyclic carbonate = 9 / 1 to 7 / 3", or "cyclic carbonate / fluorinated cyclic carbonate = 3 / 7 to 1 / 9".

[0127] The solvent may contain, for example, EC, FEC, EMC, DMC, and DEC. The volume ratio of each component may satisfy, for example, the relationship represented by the following formula. V EC +V FEC +V EMC +V DMC +V DEC =10 In the formula, V EC 、V FEC 、V EMC 、V DMC 、V DEC respectively represent the volume ratios of EC, FEC, EMC, DMC, and DEC. 1≦V EC ≦4, 0≦V FEC ≦3, V EC +V FEC ≦4, 0≦V EMC ≦9, 0≦V DMC ≦9, 0≦V DEC ≦9, 6≦V EMC +V DMC +V DEC ≦9 The relationship is satisfied. For example, the relationship of 1≦V EC ≦2 or 2≦V EC ≦3 may be satisfied. For example, the relationship of 1≦V FEC ≦2 or 2≦V FEC ≦4 may be satisfied. For example, the relationship of 3≦V EMC ≦4 or 6≦V EMC ≦8 may be satisfied. For example, the relationship of 3≦V DMC ≦4 or 6≦V DMC ≦8 may be satisfied. For example, the relationship of 3≦V DEC ≦4 or 6≦V DEC ≦8 may be satisfied.

[0128] The solvent may have a composition such as "EC / EMC = 3 / 7", "EC / DMC = 3 / 7", "EC / FEC / DEC = 1 / 2 / 7", "EC / DMC / EMC = 3 / 4 / 3", "EC / DMC / EMC = 3 / 3 / 4", "EC / FEC / DMC / EMC = 2 / 1 / 4 / 3", "EC / FEC / DMC / EMC = 1 / 2 / 4 / 3", "EC / FEC / DMC / EMC = 2 / 1 / 3 / 4", "EC / FEC / DMC / EMC = 1 / 2 / 3 / 4", etc. by volume ratio.

[0129] The electrolyte may contain an ether-based solvent. The electrolyte may contain, for example, at least one selected from the group consisting of tetrahydrofuran (THF), 1,4-dioxane (DOX), 1,3-dioxolane (DOL), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), hydrofluoroether (HFE), ethyl glyme, triglyme, tetraglyme, and derivatives thereof.

[0130] The electrolyte may contain an arbitrary additive. The addition amount (mass fraction with respect to the whole electrolyte) may be, for example, from 0.01 to 5%, from 0.05 to 3%, or from 0.1 to 1%. The additive may contain, for example, an SEI (Solid Electrolyte Interphase) formation promoter, an SEI formation inhibitor, a gas generator, an overcharge prevention agent, a flame retardant, an antioxidant, an electrode protector, a surfactant, etc.

[0131] Additives include, for example, vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3 - propane sultone (PS), tert - amylbenzene, 1,4 - di - tert - butylbenzene, biphenyl (BP), cyclohexylbenzene (CHB), ethylene sulfite (ES), ethylene sulfate (DTD), γ - butyrolactone, phosphazene compounds, carboxylic acid esters [e.g., methyl formate (MF), methyl acetate (MA), methyl propionate (MP), diethyl malonate (DEM), etc.], fluorobenzenes [e.g., monofluorobenzene (FB), 1,2 - difluorobenzene, 1,3 - difluorobenzene, 1,4 - difluorobenzene, 1,2,3 - trifluorobenzene, 1,2,4 - trifluorobenzene, 1,3,5 - trifluorobenzene, 1,2,3,4 - tetrafluorobenzene, 1,2,3,5 - tetrafluorobenzene, 1,2,4,5 - tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, etc.], fluorotoluenes (e.g., 2 - fluorotoluene, 3 - fluorotoluene, 4 - fluorotoluene, 2,3 - difluorotoluene, 2,4 - difluorotoluene, 2,5 - difluorotoluene, 2,6 - difluorotoluene, 3,4-difluorotoluene, octafluorotoluene, etc.), benzotrifluoride (e.g., benzotrifluoride, 2-fluorobenzotrifluoride, 3-fluorobenzotrifluoride, 4-fluorobenzotrifluoride, 2-methylbenzotrifluoride, 3-methylbenzotrifluoride, 4-methylbenzotrifluoride, etc.), fluoroxylene (e.g., 3-fluoro-o-xylene, 4-fluoro-o-xylene, 2-fluoro-m-xylene, 5-fluoro-m-xylene, etc.), sulfur-containing heterocyclic compounds (e.g., benzothiazole, 2-methylbenzothiazole, tetrathiafulvalene, etc.), nitrile compounds (e.g., adiponitrile, succinonitrile, etc.), phosphate esters (e.g., trimethyl phosphate, triethyl phosphate, etc.), carboxylic acid anhydrides (e.g., acetic anhydride, propionic anhydride, oxalic anhydride, succinic anhydride, maleic anhydride, phthalic anhydride, benzoic anhydride, etc.), alcohols (e.g., methanol, ethanol, n-propyl alcohol, ethylene glycol, diethylene glycol monomethyl ether, etc.), and at least one selected from the group consisting of derivatives thereof may be included.,

[0132] The components described above as supporting salts and solvents may be used as trace components (additives). Additives include, for example, LiBF 4 、LiFSI、LiTFSI、LiBOB、LiDFOB、LiDFOP、LiPO 2 F 2 、FSO 3 Li、LiI、LiBr、HFE、DOX、PC、FEC, and at least one selected from the group consisting of derivatives thereof may be included.,

[0133] The electrolytic solution may contain an ionic liquid. The ionic liquid may include, for example, at least one selected from the group consisting of sulfonium salts, ammonium salts, pyridinium salts, piperidinium salts, pyrrolidinium salts, morpholinium salts, phosphonium salts, imidazolium salts, and derivatives thereof.,

[0134] <Battery Configuration> FIG. 12 is a table showing the first battery configuration. FIG. 13 is a table showing the second battery configuration. FIG. 14 is a table showing the third battery configuration. In each table, when a plurality of types of materials are described in a cell, the description includes each material alone and combinations thereof. For example, when the materials "α, β, γ" are described in a cell, the description indicates "at least one selected from the group consisting of α, β, and γ". Any elements may be extracted from each of the first battery configuration, the second battery configuration, and the third battery configuration and arbitrarily combined.

Example

[0135] <Evaluation cell> FIG. 15 is a conceptual diagram showing the configuration of the evaluation cell. FIG. 16 is a table showing the configuration of the intervening layer in the evaluation cell. Evaluation cells 103 according to Nos. 1 to 9 were prepared. The evaluation cell 103 includes a positive electrode 10, a first intervening layer 41, a separator 30, a second intervening layer 42, and a negative electrode 20 in this order. The first intervening layer 41 and the second intervening layer 42 include inorganic particles and a binder. The details of the binder in each evaluation cell are shown in FIG. 16. The other materials are common. The inorganic particles of the intervening layer are alumina. The electrolytic solution includes a mixed solvent. The mixed solvent includes EC, DEC, and DMC. The positive electrode active material layer 12 includes NCM. The negative electrode active material layer 22 includes graphite. In the evaluation cell 103, the relationship "Pa >> Pc" is satisfied with respect to the permeation coefficient (Pc) of the positive electrode active material layer 12 and the permeation coefficient (Pa) of the negative electrode active material layer 22.

[0136] <High-rate resistance test> One cycle of "charge → rest → discharge" under the following conditions was repeated 3000 times. "C" is a symbol indicating the time rate of current. At a time rate of 1C, the rated capacity of the evaluation cell 103 is discharged in 1 hour. Charge: 30C, 10 seconds Rest: 5 seconds Discharge: 4C, 75 seconds

[0137] <Results> Figure 17 is a graph showing the evaluation results. It is considered that the higher the high-rate tolerance is, the gentler the increase in the resistance increase rate is as the number of cycles increases.

[0138] In No.1, the first intermediate layer has the same configuration as the second intermediate layer. The transmission coefficient (P1) of the first intermediate layer is considered to be equal to the transmission coefficient (P2) of the second intermediate layer. That is, it is considered that the relationship of "P1 = P2" is satisfied. In No.1, as the number of cycles increases, the increase in the resistance increase rate is remarkable.

[0139] In No.2 to No.9, the first intermediate layer has a different configuration from the second intermediate layer. The transmission coefficient (P1) of the first intermediate layer is considered to be different from the transmission coefficient (P2) of the second intermediate layer. That is, it is considered that the relationship of "P1 ≠ P2" is satisfied. In No.2 to No.9, as Δ1 in Figure 16 becomes larger than Δ2, the high-rate tolerance tends to improve.

Explanation of symbols

[0140] 10 Positive electrode, 11 Positive electrode current collector foil, 12 Positive electrode active material layer, 20 Negative electrode, 21 Negative electrode current collector foil, 22 Negative electrode active material layer, 30 Separator, 41 First intermediate layer, 42 Second intermediate layer, 101 First unit, 102 Second unit, 103 Evaluation cell, 500 Power generation element, 800 Electrolyte, 900 Exterior body, 1000 Battery (lithium ion battery), E1 First end, E2 Second end, G1 First gap, G2 Second gap.

Claims

1. comprising a power generation element and an electrolytic solution, wherein the power generation element includes a positive electrode, a separator, a negative electrode, a first intervening layer, and a second intervening layer, with the positive electrode and the negative electrode being alternately laminated with the separator interposed therebetween, wherein the positive electrode includes a positive electrode current collector foil and a positive electrode active material layer, wherein the negative electrode includes a negative electrode current collector foil and a negative electrode active material layer, wherein at least one of a first gap and a second gap is formed within the power generation element, wherein the first gap is a gap formed between the negative electrode active material layer and the separator, wherein the second gap is a gap formed between the positive electrode active material layer and the separator, wherein the first intervening layer is disposed in at least one of the first gap and the second gap, wherein the second intervening layer is disposed in at least one of the first gap and the second gap, wherein the power generation element has a stacking direction, wherein the stacking direction is parallel to the thickness directions of the positive electrode, the separator, and the negative electrode, wherein the power generation element has a first end at one end of the stacking direction and a second end at the other end of the stacking direction, wherein the first intervening layer is closer to the first end than the second intervening layer, wherein the relationship of the following formula (1) is satisfied, P1 ≠ P2 (1) In the formula (1), P1 represents the permeation coefficient of the first intervening layer with respect to the electrolytic solution, and P2 represents the permeation coefficient of the second intervening layer with respect to the electrolytic solution, a lithium ion battery.

2. The electrolytic solution is more distributed at the first end than at the second end, The lithium ion battery according to Claim 1.

3. The first intervening layer is disposed in the second gap, and The second intervening layer is disposed in the first gap, The lithium ion battery according to Claim 1.

4. The relationship of the following formula (2) is satisfied, P1 > P2 (2) The lithium ion battery according to any one of Claims 1 to 3.

5. The electrolytic solution includes a supporting salt and a solvent, The first intervening layer includes first inorganic particles and a first binder, The second intervening layer includes second inorganic particles and a second binder, The relationship of the following formula (3) is satisfied, Δ1 > Δ2 (3) In the formula (3), Δ1 represents the absolute value of the difference between the SP value of the solvent and the SP value of the first binder, Δ2 represents the absolute value of the difference between the SP value of the solvent and the SP value of the second binder, and The unit of the SP value is (cal / cm 3 ). 1 / 2 That is, The lithium-ion battery according to any one of claims 1 to 3.

6. wherein the relationships of the following formulas (4) and (5) are satisfied, 2.5 ≤ Δ1 (4) Δ2 ≤ 2 (5) The lithium-ion battery according to claim 5.

7. The power generation element includes a first unit and a second unit, in the stacking direction, the first unit is closer to the first end portion than the second unit, each of the first unit and the second unit includes the positive electrode, the separator, and the negative electrode, the first unit includes the first intervening layer in at least one of the first gap and the second gap, the second unit includes the second intervening layer in at least one of the first gap and the second gap, and the relationship of the following formula (2) is satisfied, P1 > P2 (2) The lithium-ion battery according to claim 2.

8. The second unit includes the second intervening layer in the second gap, The lithium-ion battery according to claim 7.

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