Lithium-ion battery

Abstract

To provide a lithium-ion battery which can improve a high-rate resistance.SOLUTION: A lithium-ion battery includes electrolyte and a stacked electrode body. The stacked electrode body includes a positive electrode layer and a negative electrode layer. The positive electrode layer and the negative electrode layer are alternatively laminated in a lamination direction. The stacked electrode body includes in order a first region, a second region and a third region in the lamination direction. The second region includes an intermediate point in the lamination direction. The first region includes a first cathode active material with a first grain diameter. The second region and the third region respectively include a second cathode active material with a second grain diameter, and a third cathode active material with a third grain diameter. When the first grain diameter is d1, the second grain diameter is d2, and the third grain diameter is d3, a relation of d2<d1<d3 is satisfied.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to lithium-ion batteries. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2018-106981 discloses that the permeability coefficient of the electrolyte in the in-plane direction of the positive electrode layer is changed by adjusting the binder distribution in the positive electrode layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-106981 Summary of the Invention [Problem to be solved by the invention]

[0004] The "permeability coefficient" represents the ease with which the electrolyte moves within the positive electrode layer. It is believed that the larger the permeability coefficient, the easier the electrolyte moves within the positive electrode layer. For example, it has been proposed to provide a region with a small permeability coefficient at the end of the positive electrode layer in the in-plane direction. This region can block the electrolyte, thereby reducing the amount of electrolyte that flows out of the positive electrode layer. By reducing the amount of electrolyte that flows out, it is expected that the high-rate resistance will be improved, for example.

[0005] The positive electrode layer may contain a positive electrode active material and a binder. For example, it has been proposed to adjust the permeability coefficient by varying the binder concentration in the in-plane direction. However, adjusting the permeability coefficient using this method is likely to result in quality variations. As a result, the productivity and performance of the battery may be reduced. Furthermore, there is still room for improvement in high-rate durability.

[0006] The objective of the present disclosure is to improve high-rate durability. [Means for solving the problem]

[0007] 1. The lithium-ion battery includes an electrolytic solution and a laminated electrode body. The laminated electrode body includes a positive electrode layer and a negative electrode layer. The positive electrode layer and the negative electrode layer are alternately laminated in the lamination direction. In the lamination direction, the laminated electrode body includes a first region, a second region, and a third region in this order. The second region includes the midpoint in the lamination direction. The first region includes a first positive electrode active material having a first particle size. Each of the second region and the third region includes a second positive electrode active material having a second particle size and a third positive electrode active material having a third particle size. The relationship of "d2 < d1 < d3" is satisfied. "d1" represents the first particle size. "d2" represents the second particle size. "d3" represents the third particle size.

[0008] The particle size of the positive electrode active material may be correlated with the void volume in the positive electrode layer. That is, the particle size of the positive electrode active material can be a control factor for the permeation coefficient. When the relationship of "d2 < d1 < d3" is satisfied, the permeation coefficients in the second region and the third region tend to be larger than the permeation coefficient in the first region. The first region, the second region, and the third region are arranged in the lamination direction. In the first region, since it is difficult for the electrolytic solution to flow out from the positive electrode layer, it is considered that lithium (Li) ions in the electrolytic solution are difficult to decrease. On the other hand, in the second region and the third region, the inflow and outflow of the electrolytic solution to and from the positive electrode layer are promoted. In the second region and the third region, the Li ions of the electrolytic solution that have once flowed out from the positive electrode layer can also be effectively utilized. The synergistic effect of these actions is expected to improve the high-rate tolerance.

[0009] 2. The lithium-ion battery according to the above item "1" may include, for example, the following configuration. The relationship of "d3 / d2 ≤ 2.2" is satisfied.

[0010] When the relationship of "d3 / d2 ≤ 2.2" is satisfied, the permeation coefficients in the second region and the third region tend to increase.

[0011] 3. The lithium-ion battery described in the above item “1” or “2” may include, for example, the following configuration. The relationship of “p1 < p2” and “p1 < p3” is satisfied. “p1” represents the permeation coefficient of the electrolyte with respect to the positive electrode layer in the first region. “p2” represents the permeation coefficient of the electrolyte with respect to the positive electrode layer in the second region. “p3” represents the permeation coefficient of the electrolyte with respect to the positive electrode layer in the third region.

[0012] 4. The lithium-ion battery described in any one of the above items “1” to “3” may include, for example, the following configuration. The relationship of “1 ≦ n2 ≦ 0.5(n1 + n2 + n3)” is satisfied. “n1” represents the number of layers of the positive electrode layer included in the first region. “n2” represents the number of layers of the positive electrode layer included in the second region. “n3” represents the number of layers of the positive electrode layer included in the third region.

[0013] The second region is not limited to a single positive electrode layer located in the middle in the stacking direction. The second region may have a range covering a plurality of positive electrode layers in the stacking direction.

[0014] 5. The lithium-ion battery described in the above item “3” may include, for example, the following configuration. “1 × 10 -16 m 2 ≦ p1 < 1 × 10 -14 m 2 ”, “1 × 10 -14 m 2 ≦ p2 < 1 × 10 -13 m 2 ” and “1 × 10 -14 m 2 ≦ p3 < 1 × 10 -13 m 2 ” relationship is satisfied.

[0015] Hereinafter, one embodiment of the present disclosure (hereinafter may be abbreviated as "this embodiment") and one example of the present disclosure (hereinafter may be abbreviated as "this example") will be described. However, this embodiment and this example do not limit the technical scope of the present disclosure. This embodiment and this example are illustrative in all respects. This embodiment and this example are non-restrictive. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the claims. For example, it is originally intended that any configurations may be extracted from this embodiment and arbitrarily combined. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a conceptual diagram illustrating an example of a lithium ion battery according to an embodiment of the present invention. [Figure 2] 1 is a graph showing a square wave in a high-rate durability test. [Figure 3] 1 is a graph showing the results of a high-rate durability test. [Figure 4] 1 is a graph showing the correlation between the pore size and the permeability coefficient in a positive electrode layer. [Figure 5] 3 is a graph showing a first pore size distribution. [Figure 6] 1 is a table showing the relationship between particle size ratio and permeability coefficient in a positive electrode layer. [Figure 7] 1 is a graph showing the relationship between particle size ratio and permeability coefficient in a positive electrode layer. [Figure 8] 4 is a graph showing a second pore size distribution. [Figure 9] 1 is a graph showing the correlation between the pore size of the positive electrode layer and the permeability coefficient. [Figure 10] 1 is a graph showing the correlation between the porosity and the permeability coefficient of a positive electrode layer. DETAILED DESCRIPTION OF THE INVENTION

[0017] -Terms and phrases- Geometric terms should not be interpreted in a strict sense. Examples of geometric terms include "parallel," "perpendicular," and the like. For example, directions, angles, distances, and the like may be displaced relative to one another as long as substantially the same or similar functions are obtained. Geometric terms may include, for example, tolerances, errors, and the like in design, work, manufacturing, and the like. The dimensional relationships in each figure may not match the actual dimensional relationships. The dimensional relationships in each figure may be changed to aid the reader's understanding. For example, length, width, thickness, and the like may be changed. Some components may be omitted.

[0018] Numerical ranges such as "m to n%" include the upper and lower limits unless otherwise specified. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "more than m% and less than n%." "Equal to or more" and "equal to or less" are represented by inequality signs with an equal sign "≦, ≧." "More than" and "less than" are represented by inequality signs without an equal sign "<, >." A numerical value arbitrarily selected from within the numerical range may be used as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described elsewhere in this specification, in a table, a figure, or the like.

[0019] Hereinafter, for example, "the permeability coefficient of the electrolyte through the positive electrode layer" will also be referred to as "the permeability coefficient of the positive electrode layer." The "permeability coefficient" refers to a value measured by the following method. First, a tomographic image of the positive electrode layer is acquired using FIB-SEM (Focused Ion Beam Scanning Electron Microscopy). A three-dimensional structure is reconstructed from the tomographic image. A finer tomographic pitch is desirable. A larger imaging area is desirable. For example, the following conditions may be adopted in terms of the FIB-SEM device specifications and measurement time. Fault pitch: 100 nm (may be smaller than 100 nm) Imaging area size: 50 μm × 30 μm (may be larger than 50 μm × 30 μm) Magnification: If particles (solids) and voids can be distinguished with the same imaging area size, the same magnification is used. If particles and voids cannot be distinguished, the magnification is adjusted to a value of at least three times the particle diameter. Number of slices: 200 (more than 200 is acceptable) Cross-section samples: Cross-section samples may be embedded in resin to facilitate the distinction between particles and voids. Next, the three-dimensional structure is analyzed. The permeability coefficient is calculated from the three-dimensional structure using the analysis module "FlowDict" of the simulation software "GeoDict" (manufactured by Math 2 Market). The permeability coefficient is derived using the Stokes equation or the Navier-Stokes equation. The selection of either the Stokes equation or the Navier-Stokes equation may be determined based on actual measurement data (the relationship between pressure and flow rate in the positive electrode layer). If the relationship between pressure and flow rate is linear, the Stokes equation is considered appropriate. If the relationship between pressure and flow rate is nonlinear, the Navier-Stokes equation is considered appropriate. Since the permeability coefficient in the in-plane direction of the positive electrode layer is of interest, the X-axis or Y-axis is selected as the axial direction of fluid flow. The X-axis or Y-axis is selected based on the cutting direction of the cross-sectional sample. For example, the "permeability coefficient of the negative electrode layer" can also be measured in a similar manner.

[0020] "Particle size" is measured by microscopy. That is, particle size refers to the particle size at the peak of the number-based particle size distribution measured in a cross-sectional SEM image of the positive electrode layer. In a cross-sectional SEM image, particle size refers to the maximum Feret diameter. The "maximum Feret diameter" refers to the distance between the two most distant points on the particle's outline. A particle size distribution is created from 100 or more particle sizes. For example, if the particle size distribution is unimodal, the particle size at the peak is considered to be the particle size (d1) of the medium particle. For example, if the particle size distribution is multimodal, the highest peak and the second highest peak are extracted. Of the two peaks, the smaller particle size is considered to be the particle size (d2) of the small particle. The larger particle size is considered to be the particle size (d3) of the large particle.

[0021] -Lithium-ion battery- FIG. 1 is a conceptual diagram showing an example of a lithium-ion battery according to this embodiment. The battery 100 is a lithium-ion battery. The battery 100 includes an electrolyte solution 80 and a laminated electrode assembly 50. The battery 100 may also include an exterior body 90. The exterior body 90 may house the electrolyte solution 80 and the laminated electrode assembly 50. The exterior body 90 may have any shape. The exterior body 90 may be, for example, a metal case or a pouch made of a metal foil laminate film. Within the exterior body 90, the electrolyte solution 80 may be stored, for example, vertically downward.

[0022] -Laminated electrode body- The laminated electrode body 50 can be referred to as, for example, a "power generating element." The laminated electrode body 50 may have a bipolar structure or a monopolar structure. The laminated electrode body 50 includes a positive electrode layer 10 and a negative electrode layer 20. The laminated electrode body 50 may further include a separator 30. The separator 30 is disposed between the positive electrode layer 10 and the negative electrode layer 20. The laminated electrode body 50 has a stacking direction. In FIG. 1 , the stacking direction is the Z direction. The stacking direction may be, for example, along the vertical direction. The stacking direction may be, for example, parallel to the vertical direction. The positive electrode layers 10 and the negative electrode layers 20 are alternately stacked in the stacking direction.

[0023] In the stacking direction, the laminated electrode body 50 includes a first region 51, a second region 52, and a third region 53, in this order. The second region 52 includes a midpoint in the stacking direction. For example, the first region 51 may be adjacent to the second region 52. For example, the second region 52 may be adjacent to the third region 53. For example, the regions may be continuous. For example, the first region 51 may include one end in the stacking direction. For example, the third region 53 may include the other end in the stacking direction.

[0024] For example, the first region 51 may be located vertically above the second region 52. For example, the second region 52 may be located vertically above the third region 53. For example, at least a part of the third region 53 may be immersed in the electrolytic solution 80. That is, the third region 53 may be in contact with the surplus liquid. For example, at least a part of the second region 52 may also be immersed in the electrolytic solution 80. For example, the first region 51 may be separated from the surplus liquid.

[0025] Each region contains one or more layers of the positive electrode layer 10. The first region �1 contains the first positive electrode active material. That is, the positive electrode layer 10 contained in the first region 51 contains the first positive electrode active material. The first positive electrode active material has a first particle size "d1".

[0026] The second region 52 contains the second positive electrode active material and the third positive electrode active material. That is, the positive electrode layer 10 contained in the second region 52 contains the second positive electrode active material and the third positive electrode active material. The second positive electrode active material has a second particle size "d2". The third positive electrode active material has a third particle size "d3". The third region 53 also contains the second positive electrode active material and the third positive electrode active material. That is, the positive electrode layer 10 contained in the third region 53 contains the second positive electrode active material and the third positive electrode active material.

[0027] Regarding the particle sizes of the first positive electrode active material, the second positive electrode active material, and the third positive electrode active material, the relationship of "d2 < d1 < d3" is satisfied. The relationship of "d2 < d1 < d3" is derived from the results of the following first experiment and second experiment.

[0028] - First experiment (Regarding the permeation coefficient of each region) - An evaluation cell (lithium ion battery) containing the following laminated electrode body 50 was fabricated. Positive electrode layer 10: Positive electrode active material (lithium nickel cobalt manganese composite oxide) Negative electrode layer 20: Negative electrode active material (graphite) Number of electrode laminations: 30 [[ID=X]]

[0029] [[ID=Y]] Three types of positive electrode layers 10 were prepared. The three types of positive electrode layers 10 had different permeability coefficients. The permeability coefficients were adjusted by the magnitude of the pressure applied to the positive electrode layers 10 during press processing. Permeability coefficient "L": 6 x 10 -14 m 2 Permeability coefficient "M": 3 x 10 -15 m 2 Transmission coefficient "S": 8 x 10 -16 m 2

[0030] A high-rate durability test was conducted on the evaluation cell. Figure 2 is a graph showing the square wave in the high-rate durability test. The square wave includes the following first, second, and third steps, in this order. First step: Charging (current rate = 2C, charging time = 18 seconds) Second step: Discharge (current rate = 1C, charge time = 84 seconds) Third step: Charge (current rate = 2C, charge time = 24 seconds) "C" is the symbol for the current rate. At a current rate of 1C, the rated capacity of the evaluation cell is passed for one hour.

[0031] Charge and discharge were repeated, with the square wave shown in Figure 2 being one cycle. The resistance increase rate was measured every 1,000 cycles. Figure 3 is a graph showing the results of the high-rate durability test. The smaller the resistance increase rate, the better the high-rate durability is evaluated to be.

[0032] There is a tendency for the high-rate resistance to improve as the permeability coefficient of the positive electrode layer 10 increases. This is thought to be because, in a system in which the electrolyte solution 80 (excess liquid) is present around the positive electrode layer 10, the inflow and outflow of the electrolyte solution 80 to and from the positive electrode layer 10 is promoted, and the electrolyte solution 80 that has flowed out from the positive electrode layer 10 is effectively utilized.

[0033] On the other hand, in a system where there is no electrolyte solution 80 (excess liquid) around the positive electrode layer, it is considered effective in suppressing an increase in the resistance increase rate by preventing the electrolyte solution 80 from flowing out from the positive electrode layer 10 as much as possible. In a system where there is no electrolyte solution around the positive electrode layer 10, it is considered that the electrolyte solution that has flowed out from the positive electrode layer 10 is unlikely to return to the positive electrode layer 10. It is considered that the electrolyte solution 80 in the positive electrode layer 10 continues to decrease as the electrolyte solution 80 (Li ions) flows out of the positive electrode layer 10. The decrease in the electrolyte solution 80 (Li ions) in the positive electrode layer 10 can promote an increase in resistance. Therefore, in a system where there is no electrolyte solution around the positive electrode layer 10, it is considered that a small permeability coefficient of the positive electrode layer 10 is preferable.

[0034] For example, the electrolyte may move vertically downward due to the action of gravity. For example, when the stacking direction is vertical, the first region 51 may be a system in which the electrolyte 80 is not present around the positive electrode layer 10. The second region 52 and the third region 53 may be systems in which the electrolyte 80 is present around the positive electrode layer 10. Therefore, by adopting a structure in which the permeability coefficient of the positive electrode layer 10 in the first region 51 is smaller than the permeability coefficient of the positive electrode layer 10 in the second region 52 and the third region 53, improvement in high-rate durability is expected.

[0035] -Second experiment (permeability coefficient of the positive electrode layer)- The lower the density of the positive electrode layer 10, the more voids there are in the positive electrode layer 10, which can increase the permeability coefficient. However, conventionally, a decrease in density leads to a decrease in capacity. Therefore, this embodiment proposes a structure that increases the permeability coefficient while reducing the decrease in density of the positive electrode layer 10.

[0036] As described below, three types of positive electrode active materials (particles) having different particle sizes are prepared. Large particles: D50=7.45μm Medium particle: 2μm <D50<7.45μm Small particles: D50=2μm

[0037] In No. 1, a positive electrode layer 10 containing only medium particles is simulated. The density of the positive electrode layer 10 is 2.2 g / cm3 It is.

[0038] In No.2, the positive electrode layer 10 containing only small particles is simulated. The density of the positive electrode layer 10 is 3.3 g / cm 3 It is.

[0039] In No.3, the positive electrode layer 10 containing two types of small particles and large particles is simulated. The mixing ratio (mass ratio) is "small particles: large particles = 7:3". The density of the positive electrode layer 10 is the same as that in No.2, 3.3 g / cm 3 It is.

[0040] Figure 4 is a graph showing the correlation between the pore diameter and the permeation coefficient in the positive electrode layer. By mixing large particles with small particles, the permeation coefficient increases by about 30% while the density is maintained. In the mixed system of large particles and small particles, it is considered that relatively large voids can be formed between large particles. Figure 5 is a graph showing the first pore diameter distribution. The first pore diameter distribution is the measured data measured by a mercury porosimeter. Also in the measured data, in the mixed system of large particles and small particles, the pore diameter tends to increase. On the other hand, as shown in Figure 4, in the single system of medium particles, the permeation coefficient tends to decrease.

[0041] From the results of Figure 4, for the positive electrode layer 10 for which a relatively large permeation coefficient is required, a mixed system of large particles and small particles is considered suitable. For the positive electrode layer 10 for which a relatively small permeation coefficient is required, a single system of medium particles is considered suitable.

[0042] Therefore, the positive electrode layer 10 contained in the first region 51 is a single system of medium particles. The positive electrode layers 10 contained in the second region 52 and the third region 53 are mixed systems of small particles and large particles. That is, the relationship "d2 < d1 < d3" is satisfied. By satisfying this relationship, an improvement in high-rate resistance is expected. d1: Particle size of medium particles d2: Particle size of small particles d3: Particle size of large particles

[0043] -Third experiment (particle size ratio "d3 / d2")- FIG. 6 is a table showing the relationship between the particle size ratio and the permeability coefficient in the positive electrode layer. FIG. 7 is a graph showing the relationship between the particle size ratio and the permeability coefficient in the positive electrode layer. The data in FIG. 6 are plotted in FIG. 7. The capacity, thickness, density, and mixture ratio of the positive electrode layer 10 are the same for all of No. 1 to No. 12 in FIG. 6. The mixture ratio is "small particles:large particles = 7:3 (mass ratio)". In FIG. 6 etc., for example, "1.99E-15" means "1.99 x 10 -15 " indicates.

[0044] As shown in Figure 7, when the particle size ratio of large particles to small particles, "d3 / d2," is in the range of 2.2 or less, the permeability coefficient tends to increase significantly. Figure 8 is a graph showing the second pore size distribution. The second pore size distribution is a calculated value. The second pore size distribution includes No. 8 in Figure 6, where "d3 / d2=1.2, permeability coefficient=3.13×10 -14 " and No. 12 "d3 / d2 = 11.0, permeability coefficient = 5.63 × 10 -16 The larger the permeability coefficient of the positive electrode layer 10, the larger the pore diameter at the peak in the pore diameter distribution tends to be.

[0045] Figure 9 is a graph showing the correlation between the pore size of the positive electrode layer and the permeability coefficient. As shown in Figure 9, it is believed that the pore size has a strong correlation with the permeability coefficient. There is a tendency for the permeability coefficient to increase as the pore size increases.

[0046] Fig. 10 is a graph showing the correlation between the porosity and permeability coefficient of the positive electrode layer. As shown in Fig. 10, it is believed that there is a low correlation between the porosity and permeability coefficient of the positive electrode layer 10.

[0047] -Detailed structure- The particle size ratio "d3 / d2" may be, for example, 2.0 or less, 1.8 or less, 1.6 or less, 1.5 or less, 1.4 or less, 1.3 or less, or 1.2 or less. The particle size ratio "d3 / d2" may be, for example, 1.1 or more, 1.2 or more, 1.3 or more, 1.4 or more, 1.5 or more, 1.6 or more, 1.8 or more, or 2.0 or more.

[0048] The mixing ratio of the small particles (the second positive electrode active material) and the large particles (the third positive electrode active material) may be, in terms of mass ratio, for example, "small particles: large particles = 1:9" to "small particles: large particles = 9:1", "small particles: large particles = 1:9" to "small particles: large particles = 4:6", or "small particles: large particles = 2:8" to "small particles: large particles = 4:6".

[0049] For example, the relationship of "p1 < p2" and "p1 < p3" may be satisfied. p1: Permeability coefficient of the electrolytic solution with respect to the positive electrode layer 10 in the first region 51 p2: Permeability coefficient of the electrolytic solution with respect to the positive electrode layer 10 in the second region 52 p3: Permeability coefficient of the electrolytic solution with respect to the positive electrode layer 10 in the third region 53

[0050] For example, "1×10 -16 m <00--0026>≦ p1 < 1×10 -14 m 2 ", "1×10 -14 m 2 ≦ p2 < 1×10 -13 m <000003--002>" and "1×10 -14 m 2 ≦ p3 < 1×10 -13 m 2 " may be satisfied". <--

[0051] <-- For example, "1×10 -14 m 2 ≦ p n < 1×10 -13 m 2 " may be satisfied. p n : Permeability coefficient of the electrolytic solution with respect to the negative electrode layer 20 in the second region 52 and the third region 53

[0052] The electrolyte solution 80 can also enter and exit the negative electrode layer 20. In the second region 52 and the third region 53 where the positive electrode layer 10 has a large permeability coefficient, the permeability coefficient of the positive electrode layer 10 and the permeability coefficient of the negative electrode layer 20 are equivalent to each other, which is expected to improve the high-rate durability.

[0053] The permeability coefficient "p2" and the permeability coefficient "p3" are each independently, for example, 1.13 × 10 -14 m 2 That's it, 1.69 x 10 -14 m 2 That's it, 1.84 x 10 -14 m 2 or more, or 3.13 x 10 -14 m 2 The transmission coefficient "p2" and the transmission coefficient "p3" may each independently be, for example, 3.13 × 10 -14 m 2 Below, 1.84 x 10 -14 m 2 Below, 1.69 x 10 -14 m 2 or less, or 1.13 x 10 -13 m 2 It may be the following:

[0054] For example, the relationship "1≦n2≦0.5(n1+n2+n3)" may be satisfied. n1: the number of positive electrode layers 10 included in the first region 51 (a positive integer) n2: the number of positive electrode layers 10 included in the second region 52 (a positive integer) n3: the number of positive electrode layers 10 included in the third region 53 (a positive integer)

[0055] The number of layers "n2" may be, for example, 0.4(n1+n2+n3) or less, 0.3(n1+n2+n3) or less, 0.2(n1+n2+n3) or less, or 0.1(n1+n2+n3) or less. The number of layers "n2" may be, for example, 2 or more, 3 or more, 4 or more, or 5 or more.

[0056] For example, the relationship "n1 = n3" may be satisfied. For example, the relationship "n2 ≦ (n1 + n3)" may be satisfied. For example, the relationship "n2 ≧ (n1 + n3)" may be satisfied. For example, the relationship "0.5 (n1 + n2 + n3) ≦ (n2 + n3)" may be satisfied.

[0057] The positive electrode layer 10 may be supported by a positive electrode current collector 11. The positive electrode layer 10 may be formed on both sides of the positive electrode current collector 11. The positive electrode current collector 11 may include, for example, aluminum foil. The positive electrode layer 10 may have a thickness of, for example, 10 to 1000 μm. The mass fraction of the positive electrode active material in the positive electrode layer 10 may be, for example, 80 to 99%. The positive electrode active material may have any chemical composition. The positive electrode active material may include, for example, at least one selected from the group consisting of lithium nickel manganese composite oxide, lithium nickel aluminum composite oxide, and lithium iron phosphate. The positive electrode layer 10 may further include a binder. The mass fraction of the binder in the positive electrode layer 10 may be, for example, 0.1 to 10%. The binder may have any chemical composition. The binder may include, for example, polyvinylidene fluoride. The positive electrode layer 10 may further include a conductive material. The mass fraction of the conductive material in the positive electrode layer 10 may be, for example, 0.1 to 10%. The conductive material may have any chemical composition. The conductive material may include, for example, carbon black.

[0058] The negative electrode layer 20 may be supported by a negative electrode current collector 21. The negative electrode layer 20 may be formed on both sides of the negative electrode current collector 21. The negative electrode current collector 21 may include, for example, copper foil. The negative electrode layer 20 may have a thickness of, for example, 10 to 1000 μm. The mass fraction of the negative electrode active material in the negative electrode layer 20 may be, for example, 80 to 99%. The negative electrode active material may have any chemical composition. The negative electrode active material may include, for example, at least one selected from the group consisting of graphite, silicon oxide, and silicon. The negative electrode layer 20 may further include a binder. The mass fraction of the binder in the negative electrode layer 20 may be, for example, 0.1 to 10%. The binder may have any chemical composition. The binder may include, for example, styrene butadiene rubber, carboxymethyl cellulose, or the like. Like the positive electrode layer 10, the negative electrode layer 20 may also further include a conductive material.

[0059] The separator 30 is a porous film. The separator 30 has electrical insulation properties. The separator may contain, for example, polyethylene, polypropylene, etc. The separator 30 may have a thickness of, for example, 5 to 50 μm.

[0060] The electrolyte 80 is a liquid electrolyte. The density of the electrolyte 80 (measured at 25° C.) is, for example, 1.2×10 3 to 1.3 x 10 3 kg / m 3 The viscosity of the electrolyte (measured at 25°C) may be, for example, 2 × 10 -3 From 4×10 -3 The electrolytic solution 80 may have a specific conductivity (H / (m·s)). The electrolytic solution includes a Li salt and a solvent. The concentration of the Li salt may be, for example, 0.8 to 1.2 mol / L. The Li salt may include, for example, LiPF6. The solvent may include, for example, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, or the like. The electrolytic solution 80 may further include any additives. [Explanation of symbols]

[0061] 10 positive electrode layer, 11 positive electrode current collector, 20 negative electrode layer, 21 negative electrode current collector, 30 separator, 50 laminated electrode body, 51 first region, 52 second region, 53 third region, 80 electrolyte, 90 exterior body, 100 battery.

Claims

1. an electrolyte solution and a laminated electrode body, the laminated electrode body includes a positive electrode layer and a negative electrode layer, the positive electrode layers and the negative electrode layers are alternately stacked in a stacking direction, In the stacking direction, the stacked electrode body includes a first region, a second region, and a third region in this order, the second region includes a midpoint in the stacking direction, the first region includes a first positive electrode active material having a first particle size; each of the second region and the third region includes a second positive electrode active material having a second particle size and a third positive electrode active material having a third particle size; d 2 <d 1 <d 3 The relationship is satisfied, The above d 1 represents the first particle size, The above d 2 indicates the second particle size, and The above d 3 indicates the third particle size, Lithium-ion battery.

2. d 3 / d 2 The relationship ≦2.2 is satisfied, The lithium ion battery of claim 1.

3. p 1 <p 2 , and p 1 <p 3 The relationship is satisfied, The p 1 represents the permeability coefficient of the electrolyte solution through the positive electrode layer in the first region, The p 2 represents the permeability coefficient of the electrolyte solution through the positive electrode layer in the second region, and The p 3 represents the permeability coefficient of the electrolyte solution through the positive electrode layer in the third region, The lithium ion battery according to claim 1 or 2.

4. 1≦n 2 ≦0.5(n 1 +n 2 +n 3 ) relationship is satisfied, The n 1 indicates the number of the positive electrode layers included in the first region, The n 2 indicates the number of the positive electrode layers included in the second region, and The n 3 indicates the number of the positive electrode layers included in the third region, The lithium ion battery according to claim 1 or 2.

5. 1×10 -16 m 2 ≦p 1 <1×10 -14 m 2 、 1 x 10 -14 m 2 ≦p 2 <1 x 10 -13 m 2 ,and, 1×10 -14 m 2 ≦p 3 <1×10 -13 m 2 The relationship is satisfied, The lithium ion battery of claim 3.

Images