Electrode composite for power storage cell, power storage cell, power storage module, and method for manufacturing electrode composite for power storage cell

Abstract

The present invention effectively reduces the overall electrical resistance of an electrode composite. This electrode composite for a power storage cell comprises: a first electrode that has a first current collector, and a first active material layer formed on a surface of the first current collector and including a first active material for a positive electrode or a negative electrode; and a second electrode that has a second current collector, and a second active material layer formed on a surface of the second current collector and including a second active material that has the opposite polarity from the first active material and has a lower electrical resistance value than the first active material. A plurality of through holes are formed in at least the first electrode among the first electrode and the second electrode, said through holes penetrating through the first active material layer. A first total opening area that results from summing the opening areas of all of the through holes formed in the surface of the first active material layer is greater than a second total opening area that results from summing the opening areas of all of the through holes formed in the surface of the second active material layer.

Description

Electrode composite for power storage cell, power storage cell, power storage module, and method for manufacturing electrode composite for power storage cell

[0001] The present invention relates to an electrode assembly for a power storage cell, a power storage cell, a power storage module, and a method for manufacturing an electrode assembly for a power storage cell.

[0002] Electrode composites for lithium-ion batteries have been known for some time (see Patent Documents 1 to 3 listed below). The electrode composite includes a positive electrode having a positive electrode active material layer and a negative electrode having a negative electrode active material layer. A plurality of pores are formed on the surface of each of the positive electrode active material layer and the negative electrode active material layer. With this configuration, the electrical resistance (internal resistance) of the electrode composite can be reduced by the amount corresponding to the increased surface area of ​​the active material layer, compared to, for example, a configuration in which pores are not formed on the surface of the active material layer.

[0003] JP 2016-58374 A JP 2016-58375 A JP 2012-190625 A

[0004] However, in the above-described conventional electrode composite for a lithium-ion battery, a plurality of holes of the same size and at the same pitch are formed on the surface of the positive electrode active material layer and the surface of the negative electrode active material layer, respectively, thereby reducing the electrical resistance of the electrode composite. However, there is room for further improvement in reducing the electrical resistance of the electrode composite.

[0005] It should be noted that such a problem is not limited to electrode assemblies for lithium ion batteries, but is also a common problem for electrode assemblies for other types of power storage cells.

[0006] An object of the present invention is to provide an electrode assembly for a storage cell, an energy storage cell, an energy storage module, and a method for manufacturing an electrode assembly for a storage cell that can solve the above-mentioned problems.

[0007] (1) The present specification discloses an electrode composite for a storage cell, comprising: a first electrode including a first current collector and a first active material layer formed on the surface of the first current collector and including a first active material of a positive electrode or a negative electrode; and a second electrode including a second current collector and a second active material layer formed on the surface of the second current collector and including a second active material having an opposite polarity to the first active material and a lower electrical resistance than the first active material. At least the first electrode of the first and second electrodes has a plurality of through holes penetrating the first active material layer. A first total opening area, which is the sum of the opening areas of all the through holes formed in the surface of the first active material layer, is greater than a second total opening area, which is the sum of the opening areas of all the through holes formed in the surface of the second active material layer.

[0008] In this electrode composite, at least the first electrode has a plurality of through holes formed therein that penetrate the first active material layer. Therefore, the electrical resistance of the electrode composite as a whole can be reduced compared to, for example, a configuration in which no through holes are formed in either the first or second active material layer. Furthermore, in this electrode composite, the first total opening area of ​​the first active material layer, which has a relatively high electrical resistance, is larger than the second total opening area of ​​the second active material layer, which has a relatively low electrical resistance. The effect of reducing the electrical resistance when through holes are formed in the first active material layer, which has a relatively high electrical resistance, is greater than the effect of reducing the electrical resistance when the same through holes are formed in the second active material layer, which has a relatively low electrical resistance. Therefore, compared to, for example, a configuration in which the first total opening area and the second total opening area are the same, the electrical resistance of the electrode composite as a whole can be effectively reduced by the amount of active material with a high electrical resistance that is lost due to the formation of the through holes.

[0009] (2) In the electrode composite for the above-described storage cell, the first electrode may have a plurality of first through holes formed therein that penetrate the first active material layer, and the second electrode may have a plurality of second through holes formed therein that penetrate the second active material layer, and the pitch spacing between adjacent first through holes in a predetermined direction for the plurality of first through holes may be smaller than the pitch spacing between adjacent second through holes in the predetermined direction for the plurality of second through holes. In this electrode composite, the first total opening area can be made larger than the second total opening area through a relatively simple structure in which the pitch spacing between the through holes in the first active material layer and the second active material layer is made different. Furthermore, the processing burden can be reduced by the fact that the number of through holes formed in the second active material layer is reduced.

[0010] (3) In the electrode composite for a storage cell, the first electrode may have a plurality of first through holes formed therein that penetrate the first active material layer, and the second electrode may have a plurality of second through holes formed therein that penetrate the second active material layer, and a first total inner circumferential surface area, which is the sum of the areas of the inner circumferential surfaces of the first active material layers that constitute each of the first through holes for all of the plurality of first through holes, may be larger than a second total inner circumferential surface area, which is the sum of the areas of the inner circumferential surfaces of the second active material layers that constitute each of the second through holes for all of the plurality of second through holes. This electrode composite can more effectively reduce the electrical resistance of the electrode composite as a whole, compared to, for example, a configuration in which the first total inner circumferential surface area is the same as the second total inner circumferential surface area.

[0011] (4) In the electrode composite for a storage cell, the pitch interval of the first through holes may be 200 μm or more and 700 μm or less, and the pitch interval of the second through holes may be 1000 μm or more and 6000 μm or less. With this electrode composite, the electrical resistance of the electrode composite as a whole is effectively reduced, and the amount of active material is reduced, thereby making it possible to suppress an increase in the impact on a decrease in the electrical capacity of an energy storage cell constructed using this electrode composite.

[0012] (5) In the electrode composite for a storage cell, the aperture ratio of the first through holes in the first active material layer may be 0.1% or more and 10% or less, and the aperture ratio of the second through holes in the second active material layer may be greater than 0% and 0.28% or less. With this electrode composite, the electrical resistance of the electrode composite as a whole can be effectively reduced, and the active material amount can be reduced, thereby preventing an increase in the impact on a decrease in the electrical capacity of an energy storage cell constructed using this electrode composite.

[0013] (6) In the electrode composite for a storage cell, at least some of the plurality of through holes may penetrate from the first active material layer to the first current collector. With this electrode composite, the electrical resistance of the electrode composite as a whole can be effectively reduced.

[0014] (7) In the electrode composite for a storage cell, the first electrode may have the first active material layer of a positive electrode, the first active material including lithium iron phosphate, and the second electrode may have the second active material layer of a negative electrode, the second active material including graphite. This electrode composite can effectively reduce the electrical resistance of the electrode composite as a whole.

[0015] (8) The above-described energy storage cell may be configured to include a housing and the electrode composite for an energy storage cell according to claim 1 or 2, housed in the housing. According to this configuration, the electrical resistance of the electrode composite as a whole can be effectively reduced.

[0016] (9) The above-described energy storage module may be configured to include a plurality of energy storage cells, and at least one of the plurality of energy storage cells may include the energy storage cell electrode composite according to claim 1 or claim 2. According to this configuration, the electrical resistance of the electrode composite as a whole can be effectively reduced.

[0017] (10) A method for manufacturing an electrode composite for an energy storage cell disclosed herein is a method for manufacturing an electrode composite for an energy storage cell including a first electrode and a second electrode, the method including the steps of: preparing a first member having a first active material layer including a first active material for a positive electrode or a negative electrode disposed on a surface of a first current collector; a second member having a second active material layer formed on the surface of the second current collector, the second active material layer including a second active material having an opposite polarity to the first active material and a lower electrical resistance than the first active material; forming a plurality of first through holes at a first pitch interval in the surface of the first active material layer of the first member to form the first electrode; and forming a plurality of second through holes at a second pitch interval larger than the first pitch interval in the surface of the second active material layer of the second member to form the second electrode. According to the present method for manufacturing an electrode assembly for a power storage cell, an electrode assembly with effectively reduced electrical resistance can be efficiently manufactured.

[0018] 1 is a diagram showing the external configuration of the energy storage module in the first embodiment; 2 is a diagram showing the internal configuration of the energy storage cell; 3 is a diagram showing the configuration of the positive electrode plate 110P; 4 is a diagram showing the configuration of the negative electrode plate 110N; 5 is a table showing the performance evaluation results; 6 is a graph showing the performance evaluation results; 7 is a diagram showing the configuration of the positive electrode plate 110P in a modified example of the first embodiment; 8 is a diagram showing the configuration of the negative electrode plate 110N in a modified example of the first embodiment; 9 is a diagram showing the configuration of the electrode 110 in the second embodiment;

[0019] A. First Embodiment: A-1. Configuration of Energy Storage Module 1: (Configuration of Energy Storage Module 1): Fig. 1 is an explanatory diagram showing the external configuration of the energy storage module 1 in the first embodiment. Fig. 1 shows mutually orthogonal X, Y and Z axes for specifying directions. In this specification, for convenience, the positive direction of the Z axis is referred to as the "upward direction" and the negative direction of the Z axis is referred to as the "downward direction," but the energy storage module 1 may actually be installed in a direction different from these directions.

[0020] As shown in Fig. 1, the energy storage module 1 includes a plurality of energy storage cells 10. The plurality of energy storage cells 10 are electrically connected to one another. Each energy storage cell 10 is, for example, a lithium-ion battery. The energy storage module 1 is used, for example, as a driving power source or an energy regeneration device for an electric vehicle or an electric motorcycle.

[0021] As shown in FIG. 2 , the energy storage cell 10 includes a housing 30. The housing 30 is a container having a storage space formed therein for accommodating the electrode composite 100 described below. The housing 30 is formed of, for example, a metal such as aluminum, or a synthetic resin that does not absorb moisture. The housing 30 is provided with a positive electrode terminal 40P and a negative electrode terminal 40N. Note that, for example, a configuration may be adopted in which a part or all of the metal portion of the housing 30 serves as either the positive electrode terminal 40P or the negative electrode terminal 40N. Furthermore, the energy storage cell 10 may be configured such that the electrode composite 100 is accommodated in a bag such as a laminate film.

[0022] Within the housing 30, the electrode composite 100 and an electrolyte (not shown) are contained in the same space. Specifically, as shown in FIG. 2 , the electrode composite 100 includes a positive electrode plate 110P, a negative electrode plate 110N, and a separator 120. The electrode composite 100 may include multiple pairs of positive electrode plates 110P and negative electrode plates 110N, or may include a single positive electrode plate 110P and negative electrode plate 110N. FIG. 2 shows a state in which multiple positive electrode plates 110P and negative electrode plates 110N are arranged in a predetermined direction (the Y-axis direction in this embodiment). Hereinafter, the direction in which the multiple positive electrode plates 110P and negative electrode plates 110N are arranged (the Y-axis direction) will be referred to as the "arrangement direction." The electrolyte is, for example, a mixture of an electrolyte salt, an organic solvent, and an additive.

[0023] The positive electrode plate 110P includes a positive electrode current collector 112P and a pair of positive electrode active material layers 114P, 114P supported by the positive electrode current collector 112P. The positive electrode current collector 112P is a conductive foil (metal foil) such as aluminum foil, and may be a perforated foil such as an etched foil or a punched foil. The positive electrode current collector 112P also has a positive electrode lug that protrudes upward near its upper end. The pair of positive electrode active material layers 114P are supported on both sides of the positive electrode current collector 112P. That is, one positive electrode active material layer 114P is supported on one side of the positive electrode current collector 112P, and the other positive electrode active material layer 114P is supported on the other side of the positive electrode current collector 112P. The pair of positive electrode active material layers 114P are formed from the same material. Examples of materials (cathode active materials) used to form the cathode active material layer 114P include lithium cobalt oxide, ternary lithium metal composite oxides (nickel-manganese-cobalt, etc.), lithium manganese oxide, lithium nickel oxide, and lithium iron phosphate. The pair of cathode active material layers 114P may be formed from different materials, or may be formed by mixing different materials. The cathode plate 110P is an example of a first electrode, the cathode current collector 112P is an example of a first current collector, and the cathode active material layer 114P is an example of a first active material layer.

[0024] The negative electrode plate 110N includes a negative electrode current collector 112N and a pair of negative electrode active material layers 114N, 114N supported by the negative electrode current collector 112N. The negative electrode current collector 112N is a conductive foil (metal foil) such as copper foil, and may be a porous foil such as an etched foil or a punched foil. The negative electrode current collector 112N also has a negative electrode lug that protrudes upward near its upper end. The pair of negative electrode active material layers 114N are supported on both sides of the negative electrode current collector 112N. That is, one negative electrode active material layer 114N is supported on one side of the negative electrode current collector 112N, and the other negative electrode active material layer 114N is supported on the other side of the negative electrode current collector 112N. The pair of negative electrode active material layers 114N are formed of the same material. Examples of materials (negative electrode active materials) that can be used to form the negative electrode active material layer 114N include graphite, silicon-based materials, hard carbon, soft carbon, and lithium titanate. The pair of negative electrode active material layers 114N may be formed from different materials, or may be formed by mixing different materials. The negative electrode plate 110N is an example of a second electrode, the negative electrode current collector 112N is an example of a second current collector, and the negative electrode active material layer 114N is an example of a second active material layer.

[0025] The separator 120 is made of an insulating material (for example, paper, glass fiber, or synthetic resin (such as a porous polyethylene film)).

[0026] The positive electrode plates 110P and the negative electrode plates 110N are arranged alternately one by one in the arrangement direction. One positive electrode active material layer 114P of the positive electrode plate 110P and one negative electrode active material layer 114N of the negative electrode plate 110N face each other in the arrangement direction. The separator 120 is arranged so as to be interposed between the positive electrode active material layer 114P and the negative electrode active material layer 114N that face each other in the arrangement direction. In other words, the electrode composite 100 has a stacked structure in which the positive electrode plates 110P, the negative electrode plates 110N, and the separators 120 are arranged side by side in the arrangement direction.

[0027] The lugs of the plurality of positive electrode plates 110P are electrically connected to the positive electrode terminal portion 40P, and the lugs of the plurality of negative electrode plates 110N are electrically connected to the negative electrode terminal portion 40N.

[0028] (Detailed Configuration of the Energy Storage Cell 10): FIG. 3 is an explanatory diagram showing the configuration of the positive electrode plate 110P. FIG. 3 schematically shows a portion of the surface configuration of the positive electrode active material layer 114P of the positive electrode plate 110P and a portion of the cross-sectional configuration of the positive electrode plate 110P. As shown in FIG. 3, a plurality of first through holes 200P are formed in the positive electrode plate 110P. Note that FIG. 3 only shows some of the plurality of first through holes 200P. Throughout the positive electrode plate 110P, the plurality of first through holes 200P have substantially the same shape (e.g., circular shapes on the surface of the positive electrode active material layer 114P) and substantially the same size. Throughout the positive electrode plate 110P, the plurality of first through holes 200P are arranged in a matrix at substantially equal intervals on the surface of the positive electrode active material layer 114P. Each of the first through holes 200P penetrates the positive electrode plate 110P. That is, each first through-hole 200P penetrates one positive electrode active material layer 114P, penetrates the positive electrode current collector 112P, and further penetrates the other positive electrode active material layer 114P.

[0029] FIG. 4 is an explanatory diagram showing the configuration of the negative electrode plate 110N. FIG. 4 schematically shows a portion of the surface configuration of the negative electrode active material layer 114N of the negative electrode plate 110N and a portion of the cross-sectional configuration of the negative electrode plate 110N. As shown in FIG. 4, a plurality of second through holes 200N are formed in the negative electrode plate 110N. Note that FIG. 4 only shows some of the second through holes 200N. Throughout the negative electrode plate 110N, the plurality of second through holes 200N have substantially the same shape (e.g., circular shapes on the surface of the negative electrode active material layer 114N) and substantially the same size. Throughout the negative electrode plate 110N, the plurality of second through holes 200N are arranged in a matrix at substantially equal intervals on the surface of the negative electrode active material layer 114N. Each second through hole 200N penetrates the negative electrode plate 110N. That is, each second through-hole 200N penetrates one negative electrode active material layer 114N, penetrates the negative electrode current collector 112N, and further penetrates the other negative electrode active material layer 114N.

[0030] In this embodiment, the electrical resistance value of the negative electrode active material forming the negative electrode active material layer 114N is lower than the electrical resistance value of the positive electrode active material forming the positive electrode active material layer 114P. For example, the positive electrode active material (an example of a first active material) includes lithium iron phosphate, and the negative electrode active material (an example of a second active material) includes graphite. Note that the electrical resistance of the active material may be determined as the resistance of the active material layer using, for example, an electrode resistance measurement system (HIOKI RM2610) for the positive electrode plate 110P alone or the negative electrode plate 110N alone. Alternatively, in the state of the storage cell 10, if the storage cell 10 includes a composite compound, the electrical resistance may be determined as the charge transfer resistance of each separated electrode by applying an AC voltage to the active material and measuring the impedance.

[0031] In the energy storage cell 10 of this embodiment, the following relative condition A is satisfied for the positive electrode active material layer 114P of the positive electrode plate 110P and the negative electrode active material layer 114N of the negative electrode plate 110N, which face each other. <Relative condition A> First total opening area of ​​the positive electrode active material layer 114P > Second total opening area of ​​the negative electrode active material layer 114N The total opening area is the sum of the opening areas of all of the through holes (first through holes 200P, second through holes 200N) formed in the surface (the surface facing the active material of the opposite polarity) of each active material layer (positive electrode active material layer 114P, negative electrode active material layer 114N).

[0032] The following relative condition B is satisfied for the positive electrode active material layer 114P of the positive electrode plate 110P and the negative electrode active material layer 114N of the negative electrode plate 110N, which face each other. <Relative condition B> First pitch interval Pp of the first through holes 200P in a predetermined direction < Second pitch interval Pn of the second through holes 200N in the same predetermined direction The pitch interval is the center-to-center distance between the centers of adjacent through holes in the predetermined direction. Each pitch interval Pp, Pn is the average value of the pitch intervals of the through holes (first through holes 200P, second through holes 200N). In the examples of FIGS. 3 and 4 , the predetermined directions are two directions (X-axis direction and Z-axis direction) that are perpendicular to each other.

[0033] The following relative condition C is satisfied for the positive electrode active material layer 114P of the positive electrode plate 110P and the negative electrode active material layer 114N of the negative electrode plate 110N, which face each other: <Relative condition C> First total inner circumferential surface area of ​​the first through hole 200P > Second total inner circumferential surface area of ​​the second through hole 200N The total inner circumferential surface area is the sum of the areas of the inner circumferential surfaces 116P, 116N of the active material layers (positive electrode active material layer 114P, negative electrode active material layer 114N) that constitute the through holes (first through hole 200P, second through hole 200N) for all of the multiple through holes.

[0034] For example, in the example of FIG. 3 , the area of ​​the inner circumferential surface of the positive electrode active material layer 114P is the sum of the area of ​​the inner circumferential surface 116P constituting the hole formed in one positive electrode active material layer 114P and the area of ​​the inner circumferential surface 116P constituting the hole formed in the other positive electrode active material layer 114P. In this embodiment, the first through-hole 200P includes the hole 118P formed in the positive electrode current collector 112P. However, the positive electrode current collector 112P is an extremely thin metal foil, and the inner circumferential surface constituting the hole 118P is extremely small. Therefore, the area of ​​the inner circumferential surface constituting the hole 118P may be ignored, and the area of ​​the inner circumferential surface (= (Dp × π) × H1) constituting the entire length (H1) of the first through-hole 200P in the positive electrode plate 110P may be used as the area of ​​the inner circumferential surface of the positive electrode active material layer 114P.

[0035] For example, in the example of FIG. 4 , the area of ​​the inner circumferential surface of the negative electrode active material layer 114N is the sum of the area of ​​the inner circumferential surface 116N constituting the hole formed in one negative electrode active material layer 114N and the area of ​​the inner circumferential surface 116N constituting the hole formed in the other negative electrode active material layer 114N. In this embodiment, the second through-hole 200N includes the hole 118N formed in the negative electrode current collector 112N. However, the negative electrode current collector 112N is an extremely thin metal foil, and the inner circumferential surface constituting the hole 118N is extremely small. Therefore, the area of ​​the inner circumferential surface constituting the hole 118N may be ignored, and the area of ​​the inner circumferential surface (= (Dn × π) × H2) constituting the entire length (H2) of the second through-hole 200N in the negative electrode plate 110N may be used as the area of ​​the inner circumferential surface of the negative electrode active material layer 114N.

[0036] The positive electrode active material layer 114P of the positive electrode plate 110P and the negative electrode active material layer 114N of the negative electrode plate 110N, which face each other, satisfy the following relative condition D: <Relative condition D> The first pitch interval Pp of the first through holes 200P is not less than 200 μm and not more than 700 μm, and the second pitch interval Pn of the second through holes 200N is not less than 1000 μm and not more than 6000 μm.

[0037] The following relative condition E is satisfied for the positive electrode active material layer 114P of the positive electrode plate 110P and the negative electrode active material layer 114N of the negative electrode plate 110N, which face each other. <Relative Condition E> The aperture ratio of the first through hole 200P is 0.1% or more and 10% or less, and the aperture ratio of the second through hole 200N is greater than 0% and 0.28% or less. The aperture ratio is the ratio (%) of the total aperture area to the surface area of ​​each active material layer (positive electrode active material layer 114P, negative electrode active material layer 114N). In this embodiment, the aperture ratio is the ratio (%) of the pitch area to the average value of the aperture area of ​​each through hole (first through hole 200P, second through hole 200N). The pitch area is the square of the pitch interval (pitch intervals Pp, Pn). The aperture area of ​​a through hole is the square of the aperture radius (= aperture width Dp, Dn / 2).

[0038] The opening widths Dp and Dn (hole diameters) of the through holes (first through hole 200P, second through hole 200N) can be measured using a measuring instrument such as an SEM (Scanning Electron Microscope SEM SU3500 TM-3000 manufactured by Hitachi High-Technologies Corporation) or an optical microscope (One-Shot 3D Shape Measuring Instrument VR-5000 manufactured by Keyence Corporation). Specifically, for example, the surface of the active material layer (positive electrode active material layer 114P, negative electrode active material layer 114N) is photographed using a measuring instrument to obtain an image. For the obtained image, using the measurement software of the measuring instrument, each through hole is considered to be a perfect circle, and two points located at both ends of the circle in a predetermined direction are specified. The distance between these two points is the hole diameter of the through hole, and the center position between the two points is the center position of the through hole.

[0039] A-2. Manufacturing method of the energy storage cell 10: The energy storage cell 10 can be manufactured by, for example, the following manufacturing method. First, a raw positive electrode plate and a raw negative electrode plate are prepared. The raw positive electrode plate is the positive electrode plate 110P before the first through-hole 200P is formed, and is an example of a first member. The raw negative electrode plate is the negative electrode plate 110N before the second through-hole 200N is formed, and is an example of a second member. The raw positive electrode plate and the raw negative electrode plate are each manufactured as follows.

[0040] (Preparation of raw positive electrode plate): Commercially available LiFePO ４ The powder (90 parts by weight), acetylene black powder (5 parts by weight), and polyvinylidene fluoride (PVdF) powder (5 parts by weight) were mixed, N-methylpyrrolidone was added, and the mixture was thoroughly stirred and degassed to obtain a positive electrode slurry. This positive electrode slurry was applied to both sides of aluminum foil, dried, pressed, and cut into a predetermined shape to obtain a raw positive electrode plate.

[0041] (Preparation of unprocessed negative electrode plate): Commercially available artificial graphite powder (96 parts by weight), acetylene black powder (1 part by weight), and styrene butadiene rubber (SBR) powder (2 parts by weight) were mixed, and carboxymethyl cellulose (1 part by weight) was added. The mixture was thoroughly stirred and degassed to obtain a negative electrode slurry. This negative electrode slurry was applied to both sides of a porous copper foil, dried, and pressed, and then cut into a predetermined shape to obtain a negative electrode plate.

[0042] Next, a plurality of first through holes 200P are formed at a first pitch interval Pp in the surface of the positive electrode active material layer 114P of the raw positive electrode plate to produce a positive electrode plate 110P. A plurality of second through holes 200N are formed at a second pitch interval Pn in the surface of the negative electrode active material layer 114N of the raw negative electrode plate to produce a negative electrode plate 110N. The second pitch interval Pn is different from the first pitch interval Pp (the second pitch interval Pn > the first pitch interval Pp). The through holes can be formed, for example, by laser processing the raw plate (raw positive electrode plate, raw negative electrode plate). Note that any method can be selected as the method for forming the through holes. For example, the through holes may be formed by pressing a mold having multiple small protrusions into the raw plate.

[0043] The positive electrode plate 110P and the negative electrode plate 110N thus prepared were stacked with a separator 120 (a polyethylene microporous film) interposed therebetween to form the electrode composite 100. Next, external terminals were welded to each of the positive electrode plate 110P and the negative electrode plate 110N constituting the electrode composite 100, and the electrode composite 100 was placed in a bag-shaped aluminum laminate. Next, an electrolyte solution was poured into the laminate, and then the opening of the laminate was vacuum-sealed to produce a sample of the energy storage cell 10.

[0044] A-3. Performance Evaluation: Hereinafter, a performance evaluation performed using samples of the energy storage cell 10 of the above embodiment will be described. FIG. 5 is a table showing the performance evaluation results, and FIG. 6 is a graph showing the performance evaluation results. The vertical axis of FIG. 6 indicates the charge transfer resistance Re(Z) (Ω) of the electrode composite 100, and the horizontal axis indicates the names of the six samples. The bar graph of "Initial Value" indicates the electrical resistance before the cycle test described below, and the bar graph of "300 cycles" indicates the electrical resistance after the cycle test.

[0045] A-3-1. Regarding the Samples: In this embodiment, performance evaluation was performed on six samples of the energy storage cell 10. Each sample had a configuration in which lithium iron phosphate was used as the positive electrode active material layer 114P and graphite was used as the negative electrode active material layer 114N. Each sample was manufactured according to the manufacturing method described above. The six samples differed from one another in at least one of the aperture ratio (first pitch interval Pp) of the positive electrode plate 110P and the aperture ratio (second pitch interval Pn) of the negative electrode plate 110N, but were otherwise identical in configuration (such as the size of the electrode plate or active material layer, the diameter and size of the through-holes, etc.).

[0046] A-3-2. Cycle Test and Impedance Measurement: In one cycle of the cycle test, each sample was subjected to a constant-current / constant-voltage charge (charging current 1C, upper limit voltage maintained for 30 minutes) and a constant-current discharge (discharging current 1C) once within a predetermined voltage range (e.g., 2.0 V or higher and 3.65 V or lower) in a 50°C environment. In this cycle test, the cycle was performed 300 times.

[0047] For impedance measurement, the state of charge of each sample was adjusted to 50% of full charge at each stage of the cycle test, and then the amplitude of the voltage applied to the sample was changed to 10 mV and the frequency to 10 mHz or more and 200 kHz, and the impedance of the electrode composite 100 was measured. The impedance of the electrode composite 100 can be measured by a known method. For example, it can be measured using an electrochemical measurement system (Biologic model VMP-3e or Meiden Hokuto model HZ-Pro). Hereinafter, the impedance value of the electrode composite 100 before the cycle test is referred to as the "initial impedance value," and the impedance value of the electrode composite 100 after the cycle test is referred to as the "final impedance value." The charge transfer resistance is determined from a Cole-Cole plot obtained from the impedance measurement results. Hereinafter, the charge transfer resistance value of the electrode composite 100 before the cycle test is referred to as the "initial Re value," and the charge transfer resistance value of the electrode composite 100 after the cycle test is referred to as the "final Re value."

[0048] A-3-2. Performance Evaluation Results: As shown in FIGS. 5 and 6 , the initial impedance values ​​and initial Re values ​​of Examples 1 and 2 are lower than those of Comparative Example 1. Furthermore, the final impedance values ​​and final Re values ​​of Examples 1 and 2 are lower than those of Comparative Example 1. In Comparative Example 1, no through-holes are formed in either the positive electrode plate 110P or the negative electrode plate 110N. Meanwhile, in Examples 1 and 2, a first through-hole 200P is formed in the positive electrode plate 110P, and a second through-hole 200N is formed in the negative electrode plate 110N. The exposed area of ​​the positive electrode active material layer 114P in Examples 1 and 2 that comes into contact with the electrolyte is larger than the exposed area of ​​the positive electrode active material layer 114P in Comparative Example 1 by the area of ​​the inner circumferential surfaces 116P, 116N of the through-holes. It is believed that this is why the impedance and Re values ​​of Examples 1 and 2 were lower than those of Comparative Example 1 both before and after the cycle test.

[0049] The initial impedance values ​​and initial Re values ​​of Examples 1 and 2 are lower than the initial impedance values ​​and initial Re values ​​of Comparative Example 2. Furthermore, the final impedance values ​​and final Re values ​​of Examples 1 and 2 are lower than the final impedance values ​​and final Re values ​​of Comparative Example 2. Comparative Example 2 also has first through-holes 200P formed in the positive electrode plate 110P and second through-holes 200N formed in the negative electrode plate 110N. However, in Examples 1 and 2, the first pitch interval Pp of the positive electrode plate 110P is smaller than the second pitch interval Pn of the negative electrode plate 110N. This means that both the relative condition A (first total opening area of ​​the positive electrode active material layer 114P > second total opening area of ​​the negative electrode active material layer 114N) and the relative condition B are satisfied. In this embodiment, the hole diameter of the first through hole 200P and the hole diameter of the second through hole 200N are approximately the same, and the external area of ​​the positive electrode active material layer 114P and the external area of ​​the negative electrode active material layer 114N are approximately the same.

[0050] On the other hand, in Comparative Examples 2 and 3, the first pitch distance Pp of the positive electrode plates 110P is larger than the second pitch distance Pn of the negative electrode plates 110N. This means that neither the relative condition A nor the relative condition B is satisfied.

[0051] Here, for Examples 1 and 2, the aperture ratios (first pitch interval Pp) of the positive electrode plates 110P are the same, and the aperture ratios (second pitch interval Pn) of the negative electrode plates 110N are different. However, for Examples 1 and 2, the initial impedance values ​​and initial Re values ​​are substantially the same, and the final impedance values ​​and final Re values ​​are also substantially the same. This means that differences in the aperture ratios (second pitch interval Pn) of the negative electrode plates 110N have less effect on the impedance of the electrode composite 100 than differences in the aperture ratios (first pitch interval Pp) of the positive electrode plates 110P. As described above, this is thought to be because the electrical resistance value of the negative electrode active material forming the negative electrode active material layer 114N is lower than the electrical resistance value of the positive electrode active material forming the positive electrode active material layer 114P. For this reason, it is thought that the impedance values ​​and Re values ​​of Examples 1 and 2 were lower than the impedance values ​​and Re values ​​of Comparative Examples 1 to 3 both before and after the cycle test.

[0052] Furthermore, in Comparative Example 4, the aperture ratio (first pitch interval Pp) of the positive electrode plate 110P and the aperture ratio (second pitch interval Pn) of the negative electrode plate 110N are the same. In this case, the impedance value and Re value of Comparative Example 4 are approximately equivalent to the impedance value and Re value of Examples 1 and 2. However, since Comparative Example 4 requires the formation of more through holes than Examples 1 and 2, the processing burden during manufacturing increases. Furthermore, since many through holes are formed in Comparative Example 4, the capacity of a storage cell constructed using Comparative Example 4 decreases.

[0053] A-4. Effects of First Embodiment: As described above, in the electrode composite 100 of each storage cell 10 in the above embodiment, a plurality of through holes (first through holes 200P, second through holes 200N) are formed that penetrate the active material layers (positive electrode active material layer 114P, negative electrode active material layer 114N). Therefore, the electrical resistance of the electrode composite 100 as a whole can be reduced compared to, for example, a configuration in which no through holes are formed in either the positive electrode active material layer 114P or the negative electrode active material layer 114N.

[0054] Furthermore, in the present electrode composite 100, the first total opening area of ​​the positive electrode active material layer 114P, which has a relatively high electrical resistance, is larger than the second total opening area of ​​the negative electrode active material layer 114N, which has a relatively low electrical resistance (relative condition A). The reduction in electrical resistance achieved by forming through holes in the positive electrode active material layer 114P, which has a relatively high electrical resistance, is greater than the reduction in electrical resistance achieved by forming the same through holes in the negative electrode active material layer 114N, which has a relatively low electrical resistance. Therefore, in this embodiment, the total opening area of ​​the positive electrode active material layer 114P, which has a greater effect in reducing electrical resistance, is relatively large. As a result, according to this embodiment, compared to a configuration in which the total opening area of ​​the negative electrode active material layer 114N, which has a smaller effect in reducing electrical resistance, is relatively large, while the electrical resistance of the electrode composite 100 as a whole can be effectively reduced.

[0055] In this embodiment, the first pitch interval Pp of the first through holes 200P in a predetermined direction is smaller than the second pitch interval Pn of the second through holes 200N in the same predetermined direction (relative condition B). According to this embodiment, the first total opening area can be made larger than the second total opening area by a relatively simple structure in which the pitch intervals between the through holes in the positive electrode active material layer 114P and the negative electrode active material layer 114N are made different. Furthermore, the processing burden can be reduced by the amount of through holes formed in the negative electrode active material layer 114N being reduced.

[0056] In this embodiment, the first total inner circumferential surface area of ​​first through hole 200P is larger than the second total inner circumferential surface area of ​​second through hole 200N (relative condition C). According to this embodiment, the electrical resistance of electrode assembly 100 as a whole can be more effectively reduced compared to, for example, a configuration in which the first total inner circumferential surface area is the same as the second total inner circumferential surface area.

[0057] In the present embodiment, the first pitch interval Pp of the first through holes 200P is 200 μm or more and 700 μm or less, and the second pitch interval Pn of the second through holes 200N is 1000 μm or more and 6000 μm or less (relative condition D). According to the present embodiment, the electrical resistance of the electrode composite 100 as a whole can be effectively reduced while suppressing the influence of a reduced amount of active material on the reduction in the electrical capacity of the energy storage cell 10 constructed using the electrode composite 100. That is, when the pitch interval of the first through holes is smaller than 200 μm, the electrical resistance of the electrode composite 100 as a whole can be more effectively reduced, but the reduced amount of active material may result in a reduction in the electrical capacity of the energy storage cell 10 constructed using the electrode composite 100. Furthermore, when the pitch interval of the first through holes is larger than 700 μm, the effect of reducing the electrical resistance of the electrode composite 100 as a whole may be reduced. If the pitch spacing of the second through holes is made smaller than 1000 μm, the effect of reducing the electrical resistance of the electrode composite 100 as a whole will be low, and the processing burden may increase due to the increased number of through holes formed in the active material layer.

[0058] In the present embodiment, the aperture ratio of the first through holes 200P is 0.1% or more and 10% or less, and the aperture ratio of the second through holes 200N is greater than 0% and 0.28% or less (relative condition E). According to the present embodiment, the electrical resistance of the electrode composite 100 as a whole can be effectively reduced while the effect of a reduced amount of active material on the reduction in the electrical capacity of the energy storage cell 10 constructed using the electrode composite 100 can be suppressed. That is, when the aperture ratio of the first through holes 200P is greater than 10%, the electrical resistance of the electrode composite 100 as a whole can be more effectively reduced, but the reduced amount of active material may result in a reduction in the electrical capacity of the energy storage cell 10 constructed using the electrode composite 100. Furthermore, when the aperture ratio of the first through holes 200P is less than 0.1%, the effect of reducing the electrical resistance of the electrode composite 100 as a whole may be reduced. If the opening ratio of the second through hole 200N is made larger than 0.28%, the effect of reducing the electrical resistance of the electrode composite 100 as a whole will be low, and the processing burden may increase due to the increased number of through holes formed in the active material layer.

[0059] A-5. Modification of the First Embodiment: FIG. 7 is an explanatory diagram showing the configuration of a positive electrode plate 110P in a modification of the first embodiment, and FIG. 8 is an explanatory diagram showing the configuration of a negative electrode plate 110N in a modification of the first embodiment. In the first embodiment, the through holes are exemplified as through holes (first through hole 200P, second through hole 200N) that penetrate the electrode composite 100, but it is sufficient that the through holes penetrate at least one of a pair of active material layers. Furthermore, the electrode composite 100 may be configured such that through holes are formed in active material layers with a relatively high electrical resistance value, and through holes are not formed in active material layers with a low electrical resistance value.

[0060] In this modification, as shown in FIG. 7 , the first through-hole 200P penetrates one positive electrode active material layer 114P and the positive electrode current collector 112P, but does not penetrate the other positive electrode active material layer 114P. The first through-hole 200P extends partway through the other positive electrode active material layer 114P. As shown in FIG. 8 , the second through-hole 200N penetrates one negative electrode active material layer 114N and the negative electrode current collector 112N, but does not penetrate the other negative electrode active material layer 114N. The second through-hole 200N extends partway through the other negative electrode active material layer 114N. In this modification, the electrode composite 100 satisfies the above-mentioned relative condition A. Furthermore, it is preferable that the electrode composite 100 satisfy at least one of the above-mentioned relative conditions B to E.

[0061] In this modification, the area of ​​the inner peripheral surface of the hole 118P may be ignored, and the area of ​​the inner peripheral surface of the positive electrode active material layer 114P may be, for example, the area (=(Dp×π)×H3) of the inner peripheral surface of the first through hole 200P in the positive electrode plate 110P over the entire length (H3). The area of ​​the inner peripheral surface of the hole 118N may be ignored, and the area (=(Dn×π)×H4) of the inner peripheral surface of the second through hole 200N in the negative electrode plate 110N over the entire length (H4) may be used as the area of ​​the inner peripheral surface of the negative electrode active material layer 114N.

[0062] B. Second embodiment: B-1. Configuration of power storage module: Fig. 9 is an explanatory diagram showing the configuration of an electrode 110 in the second embodiment. In the following, among the configuration of the power storage module of the second embodiment, the same configuration as the power storage module 1 of the first embodiment described above will be denoted by the same reference numerals, and the description thereof will be omitted as appropriate.

[0063] In the energy storage cell 10 of this embodiment, the following first condition is satisfied for each of the positive electrode plate 110P and the negative electrode plate 110N. <First condition> The following relational expression (1) is satisfied for each electrode 110. Total inner peripheral surface area > Total opening area ... (1) Specifically, in the example of FIG. 9 , the above relational expression (1) is satisfied for the following three configurations (a) to (c): (a) The above relational expression (1) is satisfied for one active material layer 114 (the active material layer 114 on the upper side of the current collector 112 in FIG. 3 ). (b) The above relational expression (1) is satisfied for the other active material layer 114 (the active material layer 114 on the lower side of the current collector 112 in FIG. 3 ). (c) The above relational expression (1) is satisfied for the active material layers 114 on both sides (the active material layers 114 on the upper and lower sides of the current collector 112 in FIG. 3 ).

[0064] 9, the above-mentioned relational expression (1) holds for the following three configurations (e) to (g): (e) For a configuration in which the through-hole 200 penetrates from one active material layer 114 to the other active material layer 114 via the current collector 112, the above-mentioned relational expression (1) holds for the above-mentioned (a) to (c). (f) For a configuration in which the through-hole 200 penetrates one active material layer 114 and terminates midway through the other active material layer 114 via the current collector 112, or in which the through-hole 200 is not formed in the current collector 112 or the other active material layer 114, the above-mentioned relational expression (1) holds for the above-mentioned (a). (g) In a configuration in which the through hole 200 penetrates the other active material layer 114 and the current collector 112 and stops halfway through one active material layer 114 via the current collector 112, or in which the through hole 200 is not formed in the current collector 112 or the other active material layer 114, the above relational formula (1) holds in the above (b).

[0065] In the energy storage cell 10 of this embodiment, in addition to the first condition, the following second condition is satisfied for the positive electrode plate 110P and the negative electrode plate 110N. <Second Condition> For each electrode 110, the plurality of through holes 200 are evenly dispersed and arranged on the surface of the active material layer 114. Specifically, the plurality of through holes 200 are arranged at approximately the same pitch interval P in two orthogonal directions (X direction and Z direction). Note that the shape and arrangement of the through holes 200 may vary due to, for example, the falling off of the active material from the active material layer 114. Even in such a case, it is sufficient to confirm that the plurality of through holes 200 are evenly dispersed and arranged based on, for example, the shape and arrangement of the holes 118 that constitute the through holes 200 in the current collector 112.

[0066] Furthermore, in the energy storage cell 10 of this embodiment, the following third condition is also satisfied for each electrode 110. <Third Condition> The following relational expression (2) is satisfied for the plurality of through holes 200: Pitch interval P in a predetermined direction ≦ opening width D of the through hole 200 in the predetermined direction × 20 (2) Predetermined direction: at least one of the X direction and the Z direction Opening width D: opening width of the through hole 200 in the predetermined direction on the surface of the active material layer 114 The opening width D refers to the diameter if the shape of the through hole 200 on the surface of the active material layer 114 is circular, and refers to the length of a side if the shape is rectangular. Note that the shape and arrangement of the through holes 200 may vary due to, for example, shedding of the active material from the active material layer 114. In such cases, for example, the pitch interval P may be regarded as the center-to-center distance between the holes 118 constituting the through hole 200 in the current collector 112. Furthermore, for example, the average opening width of the plurality of through holes 200 may be regarded as the opening width D.

[0067] Furthermore, in the energy storage cell 10 of this embodiment, the following fourth condition is also satisfied for each electrode 110. <Fourth condition> The plurality of through holes 200 satisfy the following relational expression (3): pitch interval P in a predetermined direction ≧ opening width D of the through holes 200 in the predetermined direction × 3 (3)

[0068] Furthermore, in the energy storage cell 10 of this embodiment, the following fifth condition is also satisfied for each electrode 110. <Fifth Condition> The following relational expression (4) is satisfied for the plurality of through holes 200: pitch interval P in a predetermined direction ≧ opening width D of the through holes 200 in the predetermined direction × 4 (4)

[0069] Furthermore, in the energy storage cell 10 of this embodiment, the following sixth condition is also satisfied for each electrode 110. <Sixth Condition> The following relational expression (5) is satisfied for each electrode 110: total inner peripheral surface area≧total opening area×1.2 (5)

[0070] B-2. Performance Evaluation: Performance evaluations performed using samples of the energy storage cell 10 according to the above embodiment will be described below. Figures 5 to 7 are explanatory diagrams showing the performance evaluation results. Each sample was configured to use lithium iron phosphate as the positive electrode active material layer 114P and graphite as the negative electrode active material layer 114N.

[0071] B-2-1. Sample Production Method: Each sample of the energy storage cell 10 was produced according to the production method described above.

[0072] B-2-2. Performance Evaluation Regarding the Third Condition: FIG. 10 is an explanatory diagram showing the results of the performance evaluation regarding the third condition. The left vertical axis and graph G1 of FIG. 10 represent the electrical resistance (Ω) of the energy storage cell 10, the right vertical axis and bar graph represent the ratio (%) of the electrical resistance (Ω) of the energy storage cell 10 relative to that of sample S0, and the horizontal axis represents the numbers of the four samples S0 to S3. All of samples S0 to S3 used in this performance evaluation had the same thickness of the current collector 112 and the same thickness of the active material layer 114, and each electrode 110 satisfied the first and second conditions. Furthermore, no through-holes 200 were formed in the electrode 110 of sample S0. The electrodes 110 of samples S1 to S3 each had through-holes 200 of approximately the same size (opening width D: 35 μm). However, the pitch interval P of the through-holes 200 differed among samples S1 to S3.

[0073] Specifically, in sample S1, the pitch interval P is 175 μm, and the ratio of the pitch interval P to the opening width D (hereinafter referred to as the "first pitch ratio") is 5. In sample S2, the pitch interval P is 700 μm, and the first pitch ratio is 20. In sample S3, the pitch interval P is 1400 μm, and the first pitch ratio is 40. As shown in graph G1 and the bar graph in FIG. 10, the smaller the first pitch ratio, the lower the electrical resistance of the energy storage cell 10. In other words, all of the samples used in this performance evaluation have approximately the same opening width D of the through holes 200, so the first pitch ratio correlates with the total number of through holes 200, and the smaller the first pitch ratio, the greater the total number of through holes 200. Here, as the total number of through holes 200 increases, the total opening area of ​​the electrode 110 increases. However, because the first condition holds for each electrode 110, the increase in the total inner circumferential surface area is greater than the increase in the total opening area. Therefore, the surface area of ​​the active material layer 114 increases throughout the electrode 110, and the smaller the first pitch ratio, the lower the electrical resistance of the energy storage cell 10. Note that, as shown in graph G1, if the first pitch ratio is 20 times or less (if the third condition is satisfied), the electrical resistance of the energy storage cell 10 can be reduced by 10% or more compared to sample S0 in which no through holes 200 are formed.

[0074] The electrical resistance of the energy storage cell 10 can be determined by measuring the electrical resistance of each sample using a known measurement method. The capacity of the energy storage cell 10 can be determined by measuring the amount of electricity passed through each sample during charging and discharging. Alternatively, the capacity of the energy storage cell 10 may be determined theoretically by calculation from the opening width D and pitch interval P of the through holes 200 of each sample, or may be determined experimentally by measuring the weight ratio of each of samples S1 to S3 to sample S0.

[0075] B-2-3. Performance Evaluation for the Fourth and Fifth Conditions: FIG. 11 is an explanatory diagram showing the performance evaluation results for the fourth and fifth conditions. The vertical axis of FIG. 11 represents the percentage of capacity reduction of the energy storage cell 10 relative to a sample in which the through-holes 200 are not formed in the electrode 110, and the horizontal axis represents the pitch interval P (μm) of the through-holes 200. Graph G2 shows the evaluation results for multiple samples in which the opening width D of the through-holes 200 is 30 μm and the pitch interval P is different, and graph G3 shows the evaluation results for multiple samples in which the opening width D of the through-holes 200 is 40 μm and the pitch interval P is different. All of the samples used in this performance evaluation had the same thickness of the current collector 112 and the same thickness of the active material layer 114, and the first and second conditions were satisfied for each electrode 110.

[0076] As shown in graphs G2 and G3 in FIG. 11 , the smaller the pitch interval P, the lower the capacity of the energy storage cell 10. That is, the pitch interval P correlates with the total number of through holes 200, and the smaller the pitch interval P, the greater the total number of through holes 200. Here, as the total number of through holes 200 increases, the amount of active material in the active material layer 114 decreases, and the capacity of the energy storage cell 10 decreases. However, according to graphs G2 and G3, it can be seen that if the first pitch ratio is 3 times or more (if the above-mentioned fourth condition is satisfied), the capacity decrease of the energy storage cell 10 can be suppressed to 10% or less. It can also be seen that if the first pitch ratio is 4 times or more (if the above-mentioned fifth condition is satisfied), the capacity decrease of the energy storage cell 10 can be suppressed to 5% or less.

[0077] B-2-4. Performance Evaluation Regarding the Sixth Condition: Figure 12 is an explanatory diagram showing the results of the performance evaluation regarding the sixth condition. Figure 12 shows the evaluation results of multiple samples in which the opening width D of the through-holes 200 is 30 μm and the pitch interval P and the thickness H of the active material layer 114 are different, and the evaluation results of multiple samples in which the opening width D is 40 μm and the pitch interval P and the thickness H of the active material layer 114 are different. All of the samples used in this performance evaluation had the same thickness of the current collector 112.

[0078] The symbol "◯" in Fig. 12 indicates that the electrical resistance of the energy storage cell 10 was reduced by 20% or more. The samples marked with "◯" had a ratio of the total inner circumferential surface area to the total opening area (hereinafter referred to as "inner circumferential surface ratio") of 1.2 or more. That is, Fig. 12 shows that if the inner circumferential surface ratio is 1.2 or more (if the sixth condition is satisfied), the electrical resistance of the energy storage cell 10 can be reduced by 20% or more.

[0079] B-3. ​​Advantages of the Second Embodiment: As described above, in the electrodes 110 (positive electrode plate 110P, negative electrode plate 110N) of each storage cell 10 in the above embodiment, a plurality of through holes 200 are formed penetrating the active material layer 114, and the total inner circumferential surface area of ​​these through holes 200 is larger than the total opening area (first condition). Therefore, according to the above embodiment, the surface area of ​​the active material layer 114 is larger than that of a configuration in which the total opening area is larger than the total inner circumferential surface area, and electrical resistance can be reliably reduced. In other words, electron transfer and lithium ion insertion and desorption occur not only on the surface of the active material layer 114 but also at positions deep in the thickness direction from the surface of the active material layer 114, allowing for effective use of the active material at positions deep in the thickness direction from the surface of the active material layer 114.

[0080] Furthermore, in the electrode 110 of the above embodiment, the total inner circumferential surface area and the total opening area of ​​all of the multiple through holes 200 formed in the active material layer 114 are compared, so that even if, for example, the shapes of the through holes 200 are non-uniform or the arrangement of the through holes 200 is non-uniform on the surface of the active material layer 114, the electrical resistance of the electrode 110 as a whole can be reliably reduced. Furthermore, in the electrode 110 of the above embodiment, the total inner circumferential surface area is larger than the total opening area. Therefore, when comparing electrodes having the same total inner circumferential surface area, the loss of active material due to the formation of the through holes 200 is smaller than in a configuration in which the total opening area is larger than the total inner circumferential surface area. Therefore, a decrease in the capacity of the energy storage cell 10 can be suppressed.

[0081] In the above embodiment, the plurality of through holes 200 formed in the electrode 110 are evenly dispersed and arranged on the surface of the active material layer 114 (second condition). Therefore, according to the above embodiment, current concentration is less likely to occur at a specific location on the electrode 110 compared to a configuration in which the plurality of through holes 200 are unevenly arranged on the surface of the active material layer 114. Therefore, it is possible to prevent the life of the storage cell 10 from being shortened.

[0082] In the above embodiment, for the plurality of through holes 200 formed in the electrode 110, the center-to-center distance (pitch interval P) between the through holes 200 is 20 times or less the opening width D of the through holes 200 (third condition). Therefore, according to the above embodiment, it is possible to effectively reduce the electrical resistance compared to a configuration in which the pitch interval P is greater than 20 times the opening width D.

[0083] In the above embodiment, for the plurality of through holes 200 formed in the electrode 110, the pitch interval P of the through holes 200 is three times or more the opening width D (fourth condition). Therefore, according to the above embodiment, compared to a configuration in which the pitch interval P is less than three times the opening width D, it is possible to suppress the reduction in the active material layer 114 caused by the formation of the through holes 200 and systematically suppress the capacity reduction of the energy storage cell 10. Furthermore, if the pitch interval P is four times or more the opening width D (fifth condition), it is possible to more systematically suppress the capacity reduction of the energy storage cell 10.

[0084] In the above embodiment, the total inner circumferential surface area of ​​each electrode 110 is 1.2 times or more the total opening area (sixth condition), which makes it possible to more effectively reduce electrical resistance compared to a configuration in which the total opening area is less than 1.2 times the total inner circumferential surface area.

[0085] C. Modifications The present invention is not limited to the above-described embodiment, and can be modified in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0086] The configurations of the electrode composite 100, the energy storage cell 10, and the energy storage module 1 in the above embodiment are merely examples and can be modified in various ways. In the above embodiment, the electrode composite 100 including the separator 120 is illustrated as an example of the electrode composite. However, the electrode composite may be one that does not yet include the separator 120. In the above embodiment, the first electrode is configured such that the first active material layer (positive electrode active material layer 114P) is formed on each of both surfaces of the first current collector (positive electrode current collector 112P). However, the first electrode may have the first active material layer formed on only one surface of the first active material layer. In the above embodiment, the second electrode is configured such that the second active material layer (negative electrode active material layer 114N) is formed on each of both surfaces of the second current collector (negative electrode current collector 112N). However, the second electrode may have the second active material layer formed on only one surface of the second active material layer.

[0087] In the above embodiment, the electrical resistance value of the positive electrode active material forming the positive electrode active material layer 114P may be lower than the electrical resistance value of the negative electrode active material forming the negative electrode active material layer 114N. In this case, the negative electrode plate 110N is an example of a first electrode, the negative electrode current collector 112N is an example of a first current collector, and the negative electrode active material layer 114N is an example of a first active material layer. The positive electrode plate 110P is an example of a second electrode, the positive electrode current collector 112P is an example of a second current collector, and the positive electrode active material layer 114P is an example of a second active material layer.

[0088] In the above embodiment, the shape of the through holes 200, 200P, 200N is not limited to a circle, but may be a polygon, an ellipse, etc. In the above embodiment, the plurality of through holes is formed at a predetermined pitch interval in two directions perpendicular to each other on the surface of the active material layer, but this is not limiting, and for example, the plurality of through holes may be formed at a predetermined pitch interval in one direction on the surface of the active material layer.

[0089] In the first embodiment and the modified examples described above, the electrode assembly 100 may have a configuration that does not satisfy at least one of the relative conditions B to E.

[0090] In the above embodiment, the energy storage cell 10 is configured such that the electrode composite 100 and the electrolyte are housed in the same space, but the energy storage cell 10 may be configured such that a plurality of electrode composites 100 are housed in different spaces (battery containers). In the above embodiment, the energy storage cell 10 is configured to have a stacked structure, but the present invention is not limited to this, and the energy storage cell 10 may be configured such that the positive electrode and the negative electrode are wound around each other, for example.

[0091] In the above embodiment, a configuration may be adopted in which at least one of the second to sixth conditions is not satisfied. Specifically, the first pitch ratio may be 5 times or less, 10 times or less, 30 times or less, or 40 times or less. The first pitch ratio may be 2 times or more, 5 times or more, or 10 times or more. The inner peripheral surface ratio may be 1.1 times or more, or 1.5 times or more. In the energy storage module 1 including a plurality of energy storage cells 10, the above-described effects can be obtained by satisfying the first condition and further the second to sixth conditions for at least one energy storage cell 10.

[0092] In the above embodiment, the current collectors 112 (positive electrode current collector 112P, negative electrode current collector 112N) are conductive foils, but are not limited to this and may be conductive plate-like members, etc. In the above embodiment, the electrodes 110 (positive electrode plate 110P, negative electrode plate 110N) are configured such that the active material layers 114 (positive electrode active material layer 114P, negative electrode active material layer 114N) are formed on both sides of the current collectors 112 (positive electrode current collector 112P, negative electrode current collector 112N). However, the active material layer 114 may be formed on only one side of the current collectors 112.

[0093] In the above embodiment, the present invention is applied to the positive electrode plate 110P and the negative electrode plate 110N used in a lithium ion battery, but this is not limited to this, and the present invention may be applied to only one of the positive electrode plate 110P and the negative electrode plate 110N, or the present invention may be applied to the electrodes of other types of storage cells (such as lithium ion capacitors).

[0094] The materials constituting each component in the above-described embodiments are merely examples, and each component may be made of other materials. Furthermore, the manufacturing method of the energy storage cell in the above-described embodiments is merely an example, and the energy storage cell may be manufactured by other manufacturing methods.

[0095] Furthermore, the technology disclosed in this specification can be realized, for example, in the following forms.

[0096] (1) The present specification discloses an electrode for a storage cell, comprising a current collector and an active material layer formed on the surface of the current collector and containing a positive electrode active material or a negative electrode active material, wherein a plurality of through holes are formed through the active material layer, and a total inner peripheral surface area, which is the sum of the areas of the inner peripheral surfaces of the active material layer constituting each of the through holes for all of the plurality of through holes, is larger than a total opening area, which is the sum of the opening areas of each of the through holes on the surface of the active material layer for all of the plurality of through holes.

[0097] In this storage cell electrode, multiple through-holes are formed through the active material layer, and the total inner circumferential surface area of ​​the through-holes is larger than the total opening area. This increases the surface area of ​​the active material layer, thereby reliably reducing electrical resistance compared to a configuration in which the total opening area is larger than the total inner circumferential surface area. Furthermore, in this storage cell electrode, the total inner circumferential surface area of ​​all of the through-holes formed in the active material layer is compared to the total opening area. Therefore, even if the through-holes are non-uniform in shape or are unevenly arranged on the surface of the active material layer, the electrical resistance of the entire electrode can be reliably reduced. Furthermore, in this storage cell electrode, the total inner circumferential surface area is larger than the total opening area. Therefore, when comparing electrodes with the same total inner circumferential surface area, the loss of active material due to the formation of the through-holes is reduced compared to a configuration in which the total opening area is larger than the total inner circumferential surface area. Therefore, using this storage cell electrode in a storage cell can suppress a decrease in the capacity of the storage cell. The through-holes may penetrate the current collector, or, when active material layers are formed on the front and back surfaces of the current collector, may penetrate both the front and back active material layers and the current collector.

[0098] (2) In the above-described storage cell electrode, the plurality of through holes may be configured to be evenly dispersed on the surface of the active material layer. With this storage cell electrode, current concentration at a specific location on the electrode is less likely to occur compared to a configuration in which the plurality of through holes are unevenly distributed on the surface of the active material layer. Therefore, by using this storage cell electrode in a storage cell, it is possible to prevent the life of the storage cell from being shortened.

[0099] (3) In the storage cell electrode, the center-to-center distance between adjacent through holes in a predetermined direction may be 20 times or less the opening width of the through holes in the surface of the active material layer in the predetermined direction. This storage cell electrode can effectively reduce electrical resistance compared to a configuration in which the center-to-center distance between the through holes is greater than 20 times the opening width of the through holes.

[0100] (4) In the storage cell electrode, the center-to-center distance between adjacent through holes in a predetermined direction may be three times or more the opening width of the through holes in the surface of the active material layer in the predetermined direction. This storage cell electrode can suppress the loss of active material due to the formation of the through holes and systematically suppress a decrease in the capacity of the storage cell, compared to a configuration in which the center-to-center distance between the through holes is less than three times the opening width of the through holes.

[0101] (5) In the storage cell electrode, the center-to-center distance between adjacent through holes in a predetermined direction may be four or more times the opening width of the through holes in the surface of the active material layer in the predetermined direction. This storage cell electrode can suppress the loss of active material caused by the formation of the through holes and systematically suppress a decrease in the capacity of the storage cell, compared to a configuration in which the center-to-center distance between the through holes is less than four times the opening width of the through holes.

[0102] (6) In the storage cell electrode, the total inner circumferential surface area may be 1.2 times or more the total opening area. This storage cell electrode can effectively reduce electrical resistance compared to a configuration in which the total inner circumferential surface area is less than 1.2 times the total opening area.

[0103] (7) The storage cell may include a positive electrode and a negative electrode, and at least one of the positive electrode and the negative electrode may be the storage cell electrode.

[0104] (8) An electric storage module may include a plurality of electric storage cells, and at least one of the plurality of electric storage cells may include the above-described electric storage cell electrode.

[0105] DESCRIPTION OF SYMBOLS 1: Energy storage module 10: Energy storage cell 30: Housing 40N: Negative electrode terminal portion 40P: Positive electrode terminal portion 100: Electrode composite 110: Electrode 110N: Negative electrode plate 110P: Positive electrode plate 112: Current collector 112N: Negative electrode current collector 112P: Positive electrode current collector 114: Active material layer 114N: Negative electrode active material layer 114P: Positive electrode active material layer 116: Inner circumferential surface 118: Hole 120: Separator 200, 200P, 200N: Through-hole D: Opening width H: Thickness P: Pitch interval

Claims

1. An electrode composite for a storage cell, comprising: a first electrode having a first current collector and a first active material layer formed on a surface of the first current collector, the first active material layer including a first active material of a positive electrode or a negative electrode; a second current collector and a second active material layer formed on the surface of the second current collector, the second active material layer including a second active material having an opposite polarity to the first active material and having a lower electrical resistance than the first active material; wherein at least the first electrode of the first and second electrodes has a plurality of through holes penetrating the first active material layer, and a first total opening area obtained by adding up the opening areas of all the through holes formed in the surface of the first active material layer is larger than a second total opening area obtained by adding up the opening areas of all the through holes formed in the surface of the second active material layer.

2. An electrode composite for a storage cell as described in claim 1, wherein the first electrode has a plurality of first through holes formed therein that penetrate the first active material layer, and the second electrode has a plurality of second through holes formed therein that penetrate the second active material layer, and the pitch interval between adjacent first through holes in a predetermined direction for the plurality of first through holes is smaller than the pitch interval between adjacent second through holes in the predetermined direction for the plurality of second through holes.

3. An electrode composite for a storage cell as described in claim 1 or 2, wherein the first electrode has a plurality of first through holes formed therein penetrating the first active material layer, and the second electrode has a plurality of second through holes formed therein penetrating the second active material layer, and a first total inner circumferential surface area, which is the sum of the areas of the inner circumferential surfaces of the first active material layers constituting each of the first through holes for all of the plurality of first through holes, is greater than a second total inner circumferential surface area, which is the sum of the areas of the inner circumferential surfaces of the second active material layers constituting each of the second through holes for all of the plurality of second through holes.

4. An electrode composite for a storage cell as described in claim 2, wherein the pitch interval of the first through holes is 200 μm or more and 700 μm or less, and the pitch interval of the second through holes is 1000 μm or more and 6000 μm or less.

5. An electrode composite for a storage cell as described in claim 4, wherein the aperture ratio of the first through-hole in the first active material layer is 0.1% or more and 10% or less, and the aperture ratio of the second through-hole in the second active material layer is greater than 0% and 0.28% or less.

6. An electrode composite for a storage cell according to claim 1, wherein at least a portion of the plurality of through holes penetrate from the first active material layer to the first current collector.

7. An electrode composite for a storage cell according to claim 1 or 2, wherein the first electrode has the first active material layer of a positive electrode, the first active material including lithium iron phosphate, and the second electrode has the second active material layer of a negative electrode, the second active material including graphite.

8. A storage cell comprising: a housing; and an electrode composite for a storage cell according to claim 1 or 2, housed in the housing.

9. A storage module comprising a plurality of storage cells, at least one of the plurality of storage cells comprising an electrode composite for a storage cell according to claim 1 or 2.

10. A method for manufacturing an electrode composite for a storage cell including a first electrode and a second electrode, comprising the steps of: preparing a first member having a first active material layer including a first active material of a positive electrode or a negative electrode disposed on a surface of a first current collector; a second current collector; and a second active material layer formed on the surface of the second current collector, the second active material layer including a second active material having an opposite polarity to the first active material and having a lower electrical resistance value than the first active material; forming a plurality of first through holes at a first pitch interval in the surface of the first active material layer of the first member to fabricate the first electrode; and forming a plurality of second through holes at a second pitch interval larger than the first pitch interval in the surface of the second active material layer of the second member to fabricate the second electrode.

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