Electrode and power storage device

Abstract

To increase energy density of a power storage device when an electrode mixture with high ionic resistance is used.SOLUTION: An electrode includes a plate-shaped base comprising an electrode mixture including an electrode active material, a plurality of comb teeth provided on the main surface of the base at an interval in a predetermined direction, and a comb groove formed by the side faces of adjacent comb teeth and the main surface of the base between the side faces. The electrode includes, as the comb teeth: a first comb tooth with a rectangular shape, a length of the first comb tooth in the predetermined direction being 100 μm or less; and a second comb tooth having a staircase shape with a tip side thinner than a root side, a length of the second comb tooth in the predetermined direction being 200 μm or less, which is the same as or longer than that of the first comb tooth, at the root side and 100 μm or less at the tip side. The first comb tooth and the second comb tooth are alternately disposed, and the electrode mixture has ionic resistance of 15 Ω m or more. A power storage device includes the above-mentioned electrode, for example, as at least one of a positive electrode and a negative electrode.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electrode and an electricity storage device. [Background technology]

[0002] Conventionally, as an electricity storage device, there has been proposed an electrode that is composed of an electrode composite material containing an electrode active material, and has, as a positive electrode and a negative electrode, a plate-shaped base, a plurality of comb teeth provided at intervals in a predetermined direction on the main surface of the base, and comb grooves formed by the side surfaces of adjacent comb teeth and the main surface of the base between the side surfaces (see, for example, Non-Patent Document 1). In Non-Patent Document 1, the shapes of the comb teeth of the positive electrode and the negative electrode are adjusted to improve the energy density, etc. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Miyamoto et al., J. Power Sources, 536, 231473 (2022). Summary of the Invention [Problem to be solved by the invention]

[0004] However, while the energy density can be increased in the electricity storage device of Non-Patent Document 1, the case where the ionic resistance of the electrode composite is high has not been considered, and it has been desired to increase the energy density of the electricity storage device when an electrode composite with high ionic resistance is used.

[0005] The present disclosure has been made to solve such problems, and has as its main object to increase the energy density of an electricity storage device when an electrode mixture with high ionic resistance is used. [Means for solving the problem]

[0006] As a result of intensive research to achieve the above-mentioned object, the inventors have found that when an electrode composite having an ionic resistance of 15 Ωm or more is used, the energy density of an electricity storage device can be increased by using an electrode in which first comb teeth having a rectangular parallelepiped shape and a width of 100 μm or less and second comb teeth having a stepped shape with a tip side narrower than the base side, a width at the base side of at least the first comb teeth and not more than 200 μm, and a width at the tip side of 100 μm or less are arranged alternately. This led to the completion of the invention disclosed in this specification.

[0007] That is, the electrode of the present disclosure is The electrode mixture includes a plate-shaped base, a plurality of comb teeth spaced apart in a predetermined direction on a main surface of the base, and comb grooves formed by side surfaces of adjacent comb teeth and the main surface of the base between the side surfaces. The comb teeth include first comb teeth that are rectangular and have a length in the predetermined direction of 100 μm or less, and second comb teeth that have a stepped shape with a tip side that is thinner than a base side, and a length in the predetermined direction of at least the first comb tooth but not exceeding 200 μm on the base side and not exceeding 100 μm on the tip side. The first comb teeth and the second comb teeth are arranged alternately, and the electrode mixture has an ionic resistance of 15 Ωm or more.

[0008] In addition, the electricity storage device of the present disclosure has The positive electrode is the electrode described above, and the ionic resistance of the electrode mixture is 30 Ωm or more; The negative electrode is the above-mentioned electrode, and the ionic resistance of the electrode mixture is 15 Ωm or more; an ion conductive medium that is interposed between the comb grooves of the positive electrode and the comb teeth of the negative electrode that are arranged to enter into the comb grooves, and between the comb grooves of the negative electrode and the comb teeth of the positive electrode that are arranged to enter into the comb grooves, and that conducts carrier ions.

[0009] Alternatively, the electricity storage device of the present disclosure includes the above-mentioned electrode. Effect of the Invention

[0010] In this electrode and electricity storage device, when an electrode composite material having a large ion resistance, such as 15 Ωm or more, is used, the energy density of the electricity storage device can be increased. The reason why such an effect is obtained is presumed to be, for example, as follows. In an electricity storage device having a large ion resistance, the ion resistance is the main cause of the internal resistance. Therefore, the internal resistance of the electricity storage device can be reduced by reducing the width of the comb teeth to reduce the distance of ion movement. On the other hand, if the width of all the comb teeth is narrowed from the base side to the tip side, the ratio of the space required to separate the positive electrode and the negative electrode increases, and the ratio of the positive electrode composite material and the negative electrode composite material decreases, and the capacity of the electricity storage device decreases. Therefore, by using comb teeth that are thin at the tip side and thick at the base side, the internal resistance can be reduced while suppressing the decrease in capacity. In the present disclosure, since the first comb teeth having a rectangular parallelepiped shape and the second comb teeth having a step shape are used and their dimensions are suitable, it is presumed that the balance between the reduction in internal resistance and the suppression of the decrease in capacity can be well balanced, and the energy density of the electricity storage device can be increased. [Brief description of the drawings]

[0011] [Figure 1] 1 is an explanatory diagram showing an outline of the configuration of an electricity storage device 10. [Diagram 2] FIG. 2 is an explanatory diagram showing an outline of the configuration of the electricity storage device of Experimental Examples 1 to 4. [Diagram 3] FIG. 1 is an explanatory diagram showing an outline of the configuration of the electricity storage devices of Experimental Examples 5 to 8. [Figure 4] FIG. 13 is an explanatory diagram showing an outline of the configuration of an electricity storage device of Experimental Example 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The electric storage device of the present disclosure described in the embodiment includes a positive electrode, a negative electrode, and an ion conductive medium. The electric storage device may include a positive electrode current collector electrically connected to the positive electrode, or may include a negative electrode current collector electrically connected to the negative electrode. The electric storage device may be, for example, an electric double layer capacitor, a hybrid capacitor, a pseudo electric double layer capacitor, an alkali metal secondary battery, an alkali metal ion battery, or the like. Examples of carrier ions of the electric storage device include alkali metal ions such as lithium ions, sodium ions, and potassium ions, and Group 2 ions such as magnesium ions, strontium ions, and calcium ions. Here, for convenience of explanation, a lithium ion secondary battery in which lithium ions are used as carrier ions will be described below as a main example.

[0013] Hereinafter, an embodiment of an electrode and an electricity storage device according to the present disclosure will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing an outline of the configuration of an electricity storage device 10, which is an example of an electricity storage device according to the present disclosure. The electricity storage device 10 includes a positive electrode 20, which is an example of an electrode according to the present disclosure, a negative electrode 40, which is an example of an electrode according to the present disclosure, an ion conductive medium 60, a positive electrode current collector 62, and a negative electrode current collector 64. The electricity storage device 10 is arranged such that the positive electrode 20 and the negative electrode 40 face each other with the ion conductive medium 60 interposed therebetween. The power storage device 10 may have a thickness T of 100 μm or more and 30,000 μm or less, which is the length in the direction in which the positive electrode 20 and the negative electrode 40 face each other (the left-right direction in FIG. 1), a width W of 500 μm or more and 30,000 μm or less, which is the length in the direction in which the positive electrode comb teeth 30 and the negative electrode comb teeth 50 described later are alternately arranged (the up-down direction in FIG. 1), and a depth D of 100 μm or more and 30,000 μm or less, which is the length in the direction perpendicular to the thickness direction and the width direction. The power storage device 10 having such dimensions can be suitably used as a microbattery used as a power source for an IoT (Internet of Things) device. In addition, in this power storage device 10, the positive electrode 20, the negative electrode 40, the ion conductive medium 60, the positive electrode current collector 62, and the negative electrode current collector 64 may appear in the same shape as the cross section appearing in the front of the paper of FIG. 1 in any cross section cut on a plane parallel to the paper of FIG. 1.

[0014] The positive electrode 20 is made of a positive electrode composite material containing a positive electrode active material, and has a plate-shaped positive electrode base 22, a plurality of positive electrode comb teeth 30 provided at intervals on the main surface 22a of the positive electrode base 22 in a predetermined direction (hereinafter also referred to as the width direction; in FIG. 1, the vertical direction), and positive electrode comb grooves 38 formed by the side surfaces 30a, 30a of adjacent positive electrode comb teeth 30, 30 and the main surface 22a of the positive electrode base 22 between the side surfaces 30a, 30a. The predetermined direction may be any direction parallel to the main surface 22a. The thickness t of the positive electrode base 22, which is the length in the direction perpendicular to the main surface 22a of the positive electrode base 22 (the left-right direction in FIG. 1), is p may be 10 μm or more, 30 μm or more, 40 μm or more, or 45 μm or more. p From the viewpoint of increasing the energy density, the thickness is preferably thin, and may be 100 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less. The width of the positive electrode base 22 may be the same as the width W of the electricity storage device 10, and the depth of the positive electrode base 22 may be the same as the depth D of the electricity storage device 10. The positive electrode comb teeth 30 are provided substantially perpendicularly to the main surface 22a of the positive electrode base 22. The height h of the positive electrode comb teeth 30 p The height h may be 100 μm or more, 200 μm or more, or 400 μm or more. pis preferably 30000 μm or less, may be 800 μm or less, or may be 600 μm or less. The depth of the positive electrode comb teeth 30 may be the same as the depth D of the electricity storage device 10. The number of the positive electrode comb teeth 30 may be, for example, 3 to 100, or 5 to 20. The width of the positive electrode comb teeth 30 will be described later. The ion conductive medium 60 and the negative electrode comb teeth 50 described later are arranged in the positive electrode comb groove 38. The width of the positive electrode comb groove 38, that is, the interval between the adjacent positive electrode comb teeth 30, 30, may be appropriately set so that the ion conductive medium 60 and the negative electrode comb teeth 50 can be arranged. The width of the positive electrode comb groove 38 may be 50 μm or more, 70 μm or more, or 90 μm or more. The width of the positive electrode comb groove 38 may be 150 μm or less, 120 μm or less, or 100 μm or less. The width of the positive electrode comb groove 38 is preferably within the above-mentioned numerical range in a portion closer to the positive electrode base portion 22 than the step 34s.

[0015] The positive electrode 20 has positive electrode first comb teeth 32 and positive electrode second comb teeth 34 as the positive electrode comb teeth 30, and the positive electrode first comb teeth 32 and the positive electrode second comb teeth 34 are alternately arranged. Here, nine positive electrode first comb teeth 32 and ten positive electrode second comb teeth 34 are alternately arranged. The positive electrode 20 further has positive electrode third comb teeth 36 as the positive electrode comb teeth 30. The positive electrode third comb teeth 36 are arranged outside at least one of the positive electrode first comb teeth 32 and the positive electrode second comb teeth 34 that are arranged at both ends. In FIG. 1, the positive electrode third comb teeth 36 are arranged outside (below) the positive electrode second comb teeth 34 arranged at the lower end.

[0016] The positive electrode first comb teeth 32 are rectangular parallelepiped-shaped, and both side surfaces 30a, 30a are flat. The positive electrode first comb teeth 32 have a width w p1 This width w p1 is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more. p1 is preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less.

[0017] The positive electrode second comb tooth 34 has a stepped shape with a tip side 34t narrower than a base side 34r, and has a structure in which a rectangular parallelepiped tip side 34t is joined to a rectangular parallelepiped base side 34r. One of the side surfaces 30a, 30a of the positive electrode second comb tooth 34 is flat, and the other has a step 34s. The base side 34r of the positive electrode second comb tooth 34 has a width w p2r is the width w of the positive electrode first comb tooth 32 p1 This width w is 200 μm or more. p2r is preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 80 μm or more. p2r is preferably 180 μm or less, more preferably 150 μm or less, and even more preferably 130 μm or less. p2r / w p1 The ratio w may be 1 or more, may be 1.2 or more, may be 1.5 or more, or may be 2 or more. p2r / w p1 The width w p2t This width w p2t is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. p2t The width w of the tip side 34t of the positive electrode second comb tooth 34 is preferably 80 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less. p2t is the width w of the root side of the positive electrode second comb tooth 34 p2r It is better if it is smaller than w p2t / w p2r The ratio w may be 3 / 4 or less, 2 / 3 or less, or 1 / 2 or less. p2t / w p2r may be 1 / 4 or more. Also, the difference w p2r -w p2t The difference w may be 100 μm or less, 80 μm or less, or 60 μm or less. p2r -w p2t The height h of the tip side 34t of the positive electrode second comb teeth 34 may be 10 μm or more, 20 μm or more, or 30 μm or more.p2t is the height h of the root side of the positive electrode second comb tooth 34 p2r It is preferable that the ratio is about the same as h p2t / h p2r is preferably 7 / 10 or more and 10 / 7 or less, more preferably 8 / 10 or more and 10 / 8 or less, and even more preferably 9 / 10 or more and 10 / 9 or less.

[0018] The positive electrode third comb teeth 36 are rectangular parallelepiped in shape, and the side surface 30a is flat. The positive electrode third comb teeth 36 have a width w p3 The width w may be 100 μm or less. p3 is preferably 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more. p3 The width w of the positive electrode third comb tooth 36 is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less. p3 is the width w of the positive electrode first comb tooth 32 p1 The width w of the positive electrode first comb tooth 32 may be approximately the same as p1 may be larger than w p3 / w p1 may be 1 / 2 or more and 2 or less, 2 / 3 or more and 3 / 2 or less, or 1 or more and 4 / 3 or less.

[0019] The positive electrode 20 is composed of a positive electrode composite material containing a positive electrode active material. The positive electrode 20 has an ionic resistance of 15 Ωm or more in terms of resistivity. The ionic resistance of the positive electrode composite material is preferably 30 Ωm or more, more preferably 50 Ωm or more, and even more preferably 100 Ωm or more. The ionic resistance of the positive electrode composite material can be calculated by calculating the effective conductivity of the composite electrode from the information on the conductivity of the electrolyte and the porosity of the composite electrode, and taking the reciprocal thereof, as described, for example, in the impedance analysis described in Reference 1 (Ogihara et al., J. Electrochem. Soc., 159, A1034 (2012)) or, for example, in Reference 2 (Doyle et al., J. Electrochem. Soc., 143, 1890 (1996)). The ionic resistance of the positive electrode mixture is significantly affected by the quality of the positive electrode active material, and is particularly large when an olivine type positive electrode active material such as lithium iron phosphate (LFP) is used.

[0020] The positive electrode 20 may include a positive electrode active material, a conductive material, and a binder. The positive electrode active material may be capable of absorbing and releasing lithium ions, and may be, for example, a compound having lithium and a transition metal, such as an oxide containing lithium and a transition metal element, or a phosphate compound containing lithium and a transition metal element. Specifically, a compound having a basic composition formula of Li (1-x) MnO 2 (0≦x≦1, etc., same below) and Li (1-x) Mn 2 O 4 The lithium manganese composite oxide has the basic composition formula Li (1-x) Chief of Staff 2 The lithium cobalt composite oxide has the basic composition formula Li (1-x) NiO 2 The lithium nickel composite oxide has the basic composition formula Li (1-x) Co a Ni b Mn c O 2 (a>0, b>0, c>0, a+b+c=1), Li (1-x) Co a Ni b Mn c O 4A lithium cobalt nickel manganese composite oxide such as (0 < a < 1, 0 < b < 1, 1 ≤ c < 2, a + b + c = 2), and a basic composition formula of LiV 2 O 3 A lithium vanadium composite oxide such as, and a basic composition formula of V 2 O 5 Transition metal oxides such as can be used. Also, a basic composition formula of LiFePO 4Lithium iron phosphate compounds having the formula: can be used as the positive electrode active material. Among these, olivine-type positive electrode active materials such as lithium iron phosphate compounds are preferred. The term "basic composition formula" means that other elements, such as Al and Mg, may be included. The conductive material is not particularly limited as long as it is an electronic conductive material that does not adversely affect the battery performance, and for example, one or more mixtures of graphite such as natural graphite (scale graphite, flake graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whisker, needle coke, carbon fiber, and metals (copper, nickel, aluminum, silver, gold, etc.) can be used. The binder plays a role of binding active material particles and conductive material particles to maintain a predetermined shape, and can be, for example, fluorine-containing resin such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine rubber, or thermoplastic resin such as polypropylene or polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR), or the like, either alone or as a mixture of two or more kinds. In addition, a cellulose-based binder or an aqueous dispersion of styrene butadiene rubber (SBR) can also be used. In the positive electrode 20, the content of the positive electrode active material is preferably higher, and is preferably 60 mass% or more with respect to the total mass of the positive electrode 20, and more preferably 70 mass% or more. In the positive electrode 20, the content of the positive electrode active material may be 99 mass% or less. In the positive electrode 20, the content of the positive electrode active material may be 30 volume% or more and 70 volume% or less with respect to the total volume of the positive electrode 20, or 40 volume% or more and 60 volume% or less. The positive electrode 20 may be a porous body, and the porosity thereof may be 10 volume % or more and 40 volume % or less, or 20 volume % or more and 30 volume % or less. The voids in the positive electrode 20 may be filled with a nonaqueous electrolyte solution resulting from the ion conductive medium 60.

[0021] The negative electrode 40 is made of a negative electrode composite material containing a negative electrode active material, and has a plate-shaped negative electrode base 42, a plurality of negative electrode comb teeth 50 provided at intervals on the main surface 42a of the negative electrode base 42 in a predetermined direction (hereinafter also referred to as the width direction; in FIG. 1, the vertical direction), and negative electrode comb grooves 58 formed by the side surfaces 50a, 50a of adjacent negative electrode comb teeth 50, 50 and the main surface 42a of the negative electrode base 42 between the side surfaces 50a, 50a. The predetermined direction may be any direction parallel to the main surface 42a. The thickness t of the negative electrode base 42, which is the length in the direction perpendicular to the main surface 42a of the negative electrode base 42 (the left-right direction in FIG. 1), is n may be 10 μm or more, 30 μm or more, 40 μm or more, or 45 μm or more. n From the viewpoint of increasing the energy density, the thickness is preferably thin, and may be 100 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less. The width of the negative electrode base 42 may be the same as the width W of the electricity storage device 10, and the depth of the negative electrode base 42 may be the same as the depth D of the electricity storage device 10. The negative electrode comb teeth 50 are provided substantially perpendicularly to the main surface 42a of the negative electrode base 42. The height h of the negative electrode comb teeth 50 n The height h may be 100 μm or more, 200 μm or more, or 400 μm or more. nis preferably 30000 μm or less, may be 800 μm or less, or may be 600 μm or less. The depth of the negative electrode comb teeth 50 may be the same as the depth D of the electricity storage device 10. The number of the negative electrode comb teeth 50 may be, for example, 3 to 100, or 5 to 20. The width of the negative electrode comb teeth 50 will be described later. The ion conductive medium 60 and the above-mentioned positive electrode comb teeth 30 are arranged in the negative electrode comb groove 58. The width of the negative electrode comb groove 58, that is, the interval between the adjacent negative electrode comb teeth 50, 50, may be appropriately set so that the ion conductive medium 60 and the positive electrode comb teeth 30 can be arranged. The width of the negative electrode comb groove 58 may be 50 μm or more, 70 μm or more, or 90 μm or more. The width of the negative electrode comb groove 58 may be 150 μm or less, 120 μm or less, or 100 μm or less. The width of the negative electrode comb groove 58 is preferably within the above-mentioned numerical range at a portion closer to the negative electrode base 42 than the step 54s. The negative electrode 40 is preferably made to have the same shape and dimensions as the positive electrode 20. For example, the negative electrode base 42 is preferably made to have the same shape and dimensions as the positive electrode base 22. The negative electrode comb teeth 50 are preferably made to have the same shape and dimensions as the positive electrode comb teeth 30. The negative electrode comb groove 58 is preferably made to have the same shape and dimensions as the positive electrode comb groove 38.

[0022] The negative electrode 40 has negative electrode first comb teeth 52 and negative electrode second comb teeth 54 as the negative electrode comb teeth 50, and the negative electrode first comb teeth 52 and the negative electrode second comb teeth 54 are alternately arranged. Here, nine negative electrode first comb teeth 52 and ten negative electrode second comb teeth 54 are alternately arranged. The negative electrode 40 further has negative electrode third comb teeth 56 as the negative electrode comb teeth 50. The negative electrode third comb teeth 56 are arranged on the outside of at least one of the negative electrode first comb teeth 52 and the negative electrode second comb teeth 54 that are arranged at both ends. In FIG. 1, the negative electrode third comb teeth 56 are arranged on the outside (upper side) of the negative electrode second comb teeth 54 arranged at the upper end.

[0023] The negative electrode first comb teeth 52 are rectangular parallelepiped-shaped, and both side surfaces 50a, 50a are flat. The negative electrode first comb teeth 52 have a width w n1 This width w n1is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more. n1 The width w of the negative electrode first comb teeth 52 is preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less. The negative electrode first comb teeth 52 preferably have the same shape and dimensions as the positive electrode first comb teeth 32. n1 The width w of the positive electrode first comb tooth 32 is determined according to the ionic resistance of the negative electrode composite material and the ionic resistance of the positive electrode composite material. p1 It may be larger or smaller than.

[0024] The negative electrode second comb tooth 54 has a stepped shape with a tip side 54t narrower than a base side 54r, and has a structure in which a rectangular parallelepiped tip side 54t is joined to a rectangular parallelepiped base side 54r. One of the side surfaces 50a, 50a of the negative electrode second comb tooth 54 is flat, and the other has a step 54s. The negative electrode second comb tooth 54 is disposed such that this step 54s faces the step 34s of the positive electrode second comb tooth 34. The base side 54r of the negative electrode second comb tooth 54 has a width w n2r is the width w of the negative electrode first comb tooth 52 n1 This width w is 200 μm or more. n2r is preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 80 μm or more. n2r is preferably 180 μm or less, more preferably 150 μm or less, and even more preferably 130 μm or less. n2r / w n1 The ratio w may be 1 or more, may be 1.2 or more, may be 1.5 or more, or may be 2 or more. n2r / w n1 The width w n2t This width w n2t is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. n2t The width w of the tip side 54t of the negative electrode second comb tooth 54 is preferably 80 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less.n2t is the width w of the root side of the negative electrode second comb tooth 54 n2r It is better if it is smaller than w n2t / w n2r The ratio w may be 3 / 4 or less, 2 / 3 or less, or 1 / 2 or less. n2t / w n2r may be 1 / 4 or more. Also, the difference w n2r -w n2t The difference w may be 100 μm or less, 80 μm or less, or 60 μm or less. n2r -w n2t The height h of the tip side 54t of the negative electrode second comb teeth 54 may be 10 μm or more, 20 μm or more, or 30 μm or more. n2t is the height h of the base side of the negative electrode second comb tooth 54 n2r It is preferable that the ratio is about the same as h n2t / h n2r is preferably 7 / 10 or more and 10 / 7 or less, more preferably 8 / 10 or more and 10 / 8 or less, and even more preferably 9 / 10 or more and 10 / 9 or less. The negative electrode second comb teeth 54 preferably have the same shape and dimensions as the positive electrode second comb teeth 34. The width w n2t is determined depending on the ionic resistance of the negative electrode composite material and the ionic resistance of the positive electrode composite material. p2t In addition, the width w of the base side 54r of the negative electrode second comb tooth 54 may be larger or smaller than . n2r is determined depending on the ionic resistance of the negative electrode composite material and the ionic resistance of the positive electrode composite material. p2r However, the difference w n2r -w n2t The difference w p2r -w p2t This is preferable because it allows the thickness of the ion conductive medium 60 to be constant.

[0025] The negative electrode third comb teeth 56 are rectangular parallelepiped-shaped, and the side surfaces 50a are flat. The negative electrode third comb teeth 56 have a width w n3 The width w may be 100 μm or less.n3 is preferably 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more. n3 The width w of the negative electrode third comb tooth 56 is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less. n3 is the width w of the negative electrode first comb tooth 52 n1 The width w of the negative electrode first comb tooth 52 may be approximately the same as n1 may be larger than w n3 / w n1 may be 1 / 2 or more and 2 or less, 2 / 3 or more and 3 / 2 or less, or 1 or more and 4 / 3 or less. The negative electrode third comb teeth 56 preferably have the same shape and dimensions as the positive electrode third comb teeth 36. The width w of the negative electrode third comb teeth 56 n3 The width w of the third comb tooth 36 of the positive electrode is determined according to the ionic resistance of the negative electrode mixture and the ionic resistance of the positive electrode mixture. p3 It may be larger or smaller than.

[0026] The negative electrode 40 is composed of a negative electrode composite material containing a negative electrode active material. The negative electrode 40 has an ionic resistance of 15 Ωm or more in terms of resistivity. The ionic resistance of the negative electrode composite material is preferably 24 Ωm or more, more preferably 30 Ωm or more, and even more preferably 40 Ωm or more. The ionic resistance of the negative electrode composite material can be determined in the same manner as the ionic resistance of the positive electrode composite material. The ionic resistance of the negative electrode composite material is significantly affected by the material of the negative electrode active material, and is particularly large when a negative electrode active material that is a composite oxide such as lithium titanate (LTO) is used.

[0027] The negative electrode 40 may include a negative electrode active material and a binder, and may include a conductive material as necessary. The negative electrode active material may be capable of absorbing and releasing lithium ions, and examples of the material include inorganic compounds such as tin compounds, carbonaceous materials capable of absorbing and releasing lithium ions, composite oxides containing multiple elements, and conductive polymers. Examples of carbonaceous materials include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, and carbon fibers. Among these, graphites such as artificial graphite and natural graphite are preferred because they have an operating potential close to that of metallic lithium, can be charged and discharged at a high operating voltage, and can suppress self-discharge when a lithium salt is used as a supporting salt, and can reduce irreversible capacity during charging. Examples of composite oxides include lithium titanium composite oxides such as lithium titanate (LTO) and lithium vanadium composite oxides such as lithium vanadate. Of these, composite oxides such as lithium titanate are preferred as the negative electrode active material. The conductive material, binder, and the like used in the negative electrode 40 may be the same as those exemplified for the positive electrode 20. In the negative electrode 40, the content of the negative electrode active material is preferably higher, and is preferably 60% by mass or more, and more preferably 70% by mass or more, based on the total mass of the negative electrode 40. In the negative electrode 40, the content of the negative electrode active material may be 99% by mass or less. In the negative electrode 40, the content of the negative electrode active material may be 20% by volume or more and 60% by volume or less, or 30% by volume or more and 50% by volume or less, based on the total volume of the negative electrode 40. The negative electrode 40 may be a porous body, and the porosity may be 30% by volume or more and 50% by volume or less, or 35% by volume or more and 45% by volume or less. The voids in the negative electrode 40 may be filled with a nonaqueous electrolyte solution resulting from the ion conductive medium 60.

[0028] The ion conductive medium 60 is interposed between the positive electrode 20 and the negative electrode 40. More specifically, the ion conductive medium 60 is interposed between the positive electrode comb teeth 30 and the negative electrode comb grooves 58, and between the positive electrode comb grooves 38 and the negative electrode comb teeth 50. The ion conductive medium 60 is disposed so as to fill the gaps between the positive electrode comb teeth 30 and the negative electrode comb grooves 58, and between the positive electrode comb grooves 38 and the negative electrode comb teeth 50. The thickness t of the ion conductive medium 60 corresponding to these gaps is s may be, for example, 1 μm or more and 30 μm or less, 5 μm or more and 25 μm or less, or 10 μm or more and 20 μm or less.

[0029] The ionically conductive medium 60 conducts lithium ions, which are carrier ions. The ionically conductive medium may be, for example, a non-aqueous electrolyte solution containing a supporting salt (supporting electrolyte) and an organic solvent. For example, when the carrier of the positive electrode is lithium ions, the supporting salt may contain a known lithium salt. For example, the lithium salt may be LiPF 6 Or LiBF 4 , LiClO 4 ,LiAsF 6 ,Li(CF 3 SO 2 ) 2 N,LiN(C 2 F 5 SO 2 ) 2 Among these, LiPF 6 Or LiBF 4is preferable. The concentration of the supporting salt in the non-aqueous electrolyte is preferably 0.1 mol / L or more and 5 mol / L or less, more preferably 0.5 mol / L or more and 2 mol / L or less. When the concentration of the supporting salt is 0.1 mol / L or more, a sufficient current density can be obtained, and when it is 5 mol / L or less, the electrolyte can be more stabilized. In addition, a flame retardant such as a phosphorus-based or halogen-based flame retardant may be added to the non-aqueous electrolyte. As the organic solvent, for example, an aprotic organic solvent can be used. As such an organic solvent, for example, a cyclic carbonate, a chain carbonate, a cyclic ester, a cyclic ether, a chain ether, etc. can be mentioned. As the cyclic carbonate, for example, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, etc. can be mentioned. As the chain carbonate, for example, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, etc. can be mentioned. Examples of cyclic ester carbonates include gamma butyrolactone and gamma valerolactone. Examples of cyclic ethers include tetrahydrofuran and 2-methyltetrahydrofuran. Examples of chain ethers include dimethoxyethane and ethylene glycol dimethyl ether. These may be used alone or in combination. In addition, as the non-aqueous electrolyte, nitrile solvents such as acetonitrile and propylnitrile, ionic liquids, etc. may also be used. In addition, an aqueous electrolyte may be used instead of the non-aqueous electrolyte.

[0030] The ion conductive medium 60 may be an ion conductive membrane containing a resin and the above-mentioned electrolyte. Examples of the resin include polyvinylidene fluoride (PVdF), a copolymer of PVdF and hexafluoropropylene (PVdF-HFP), polymethyl methacrylate (PMMA), and a copolymer of PMMA and an acrylic polymer. For example, in the case of a copolymer of PVdF and HFP, a part of the nonaqueous electrolyte swells and gels the membrane, forming an ion conductive membrane.

[0031] The positive electrode current collector 62 is electrically connected to the positive electrode 20. Here, the positive electrode current collector 62 is formed on the entire surface of the surface 22b of the positive electrode base 22 opposite to the main surface 22a on which the positive electrode comb teeth 30 are provided. The arrangement of the positive electrode current collector 62 is not limited thereto, and may be formed on a part of the surface 22b, or may be formed on the entire surface or a part of the end surface of the positive electrode 20 from which the depth of the comb grooves 30 can be seen, that is, the front or back surface in FIG. 1. The positive electrode current collector 62 is not particularly limited as long as it is chemically and electrically stable with respect to the positive electrode active material, and may be aluminum, titanium, stainless steel, nickel, iron, baked carbon, conductive polymer, conductive glass, or the like, and may be aluminum or copper whose surface has been treated with carbon, nickel, titanium, silver, or the like for the purpose of improving adhesion, conductivity, and oxidation resistance. Of these, aluminum is preferred. This is because the positive electrode collector 62 is particularly suitable for the positive electrode of a lithium secondary battery because it is difficult to dope lithium ions in the potential region used as the positive electrode collector 62 and has high corrosion resistance. The shape of the positive electrode collector 62 can be a sheet, a net, a punched or expanded one, a lath, or the like. The sheet shape includes a foil shape and a film shape. The thickness of the positive electrode collector 62 is preferably, for example, 10 μm or more and 20 μm or less, and more preferably 12 μm or more and 17 μm or less. If the thickness of the positive electrode collector 62 is 10 μm or more, the mechanical strength of the positive electrode collector 62 can be further increased. In addition, if the thickness of the positive electrode collector 62 is 20 μm or less, the volume fraction of the positive electrode collector 62 in the electricity storage device 10 can be reduced and the volume fraction of the positive electrode 20, etc. can be further increased, so that the energy density of the electricity storage device 10 can be further increased.

[0032] The negative electrode current collector 64 is electrically connected to the negative electrode 40. Here, the negative electrode current collector 64 is formed on the entire surface of the surface 42b of the negative electrode base 42 opposite to the main surface 42a on which the negative electrode comb teeth 50 are provided. The arrangement of the negative electrode current collector 64 is not limited thereto, and may be formed on a part of the surface 42b, or may be formed on the entire surface or a part of the end surface of the negative electrode 40 from which the depth of the comb grooves 50 can be seen, that is, the front or back surface in FIG. 1. The negative electrode current collector 64 is not particularly limited as long as it is chemically and electrically stable with respect to the negative electrode active material, and may be copper, nickel, stainless steel, titanium, aluminum, baked carbon, conductive polymer, conductive glass, Al-Cd alloy, or the like, and may be, for example, copper whose surface has been treated with carbon, nickel, titanium, silver, or the like for the purpose of improving adhesion, conductivity, and reduction resistance. Of these, copper is preferred. This is because the negative electrode collector 64 is particularly suitable for the negative electrode of a lithium secondary battery because it is difficult to be doped with lithium ions in the potential region used as the negative electrode collector 64 and has high corrosion resistance. The shape of the negative electrode collector 64 can be a sheet, a net, a punched or expanded one, a lath, or the like. The sheet shape includes a foil shape, a film shape, and the like. The thickness of the negative electrode collector 64 is preferably, for example, 5 μm or more and 15 μm or less, and more preferably 8 μm or more and 12 μm or less. If the thickness of the negative electrode collector 64 is 5 μm or more, the mechanical strength of the negative electrode collector 64 can be further increased. In addition, if the thickness of the negative electrode collector 64 is 15 μm or less, the volume fraction of the negative electrode collector 64 in the electricity storage device 10 can be reduced and the volume fraction of the negative electrode 40, etc. can be further increased, so that the energy density of the electricity storage device 10 can be further increased.

[0033] The thickness T of the electricity storage device 10 may be, for example, 100 μm or more and 30000 μm or less, 300 μm or more and 1000 μm or less, 500 μm or more and 700 μm or less, or 600 μm or less. However, the thickness T excludes the positive electrode collector 62 and the negative electrode collector 64. The width W of the electricity storage device 10 may be, for example, 500 μm or more and 30000 μm or less, 1000 μm or more and 7000 μm or less, 2000 μm or more and 5000 μm or less, or 3000 μm. The depth D of the electricity storage device 10 may be, for example, 100 μm or more and 30000 μm or less, 1000 μm or more and 7000 μm or less, 2000 μm or more and 5000 μm or less, or 3000 μm.

[0034] The electricity storage device 10 may be formed, for example, by using a 3D printing technique. When the electricity storage device 10 is manufactured by using a 3D printing technique, for example, as in Reference 3 (Sun et al., Adv. Mater., 25, 4539 (2013)), a high-viscosity electrode ink may be applied to manufacture a 3D structure, and then the 3D structure may be heated to remove liquids, polymers, and the like, and then an electrolyte solution may be injected and packaged. The electrode inks for the positive and negative electrodes used in this case may have an active material content of, for example, 45% by mass or more and 65% by mass or less, or 50% by mass or more and 60% by mass or less. The electricity storage device 10 may also be formed by using a lithography technique, for example, as in Reference 4 (Ning et al., Proc. Natl. Acad. Sci. USA, 112, 6573 (2015)).

[0035] In the electricity storage device 10 of the embodiment described above, when an electrode composite material having a high ionic resistance, such as 15 Ωm or more, is used, the energy density of the electricity storage device 10 can be increased. In particular, when the current density is 6 mA / cm 2The energy density can be increased when discharging at a high current density such as the above. The reason why such an effect is obtained is presumed to be, for example, as follows. In the electricity storage device 10, a positive electrode composite material and a negative electrode composite material having a large ionic resistance are used, and the ionic resistance is the main cause of the internal resistance. Therefore, the internal resistance of the electricity storage device 10 can be reduced by reducing the width of the positive electrode first comb tooth 32 and the negative electrode first comb tooth 52 to reduce the distance of ion movement. On the other hand, if the width of all the positive electrode comb teeth 30 and the negative electrode comb teeth 50 is narrowed from the base side to the tip side, the ratio of the space required to separate the positive electrode 20 and the negative electrode 40 increases, and the ratio of the positive electrode composite material and the negative electrode composite material decreases, and the capacity of the electricity storage device 10 decreases. Therefore, by using the positive electrode second comb tooth 34 having a thin tip side 34t and a thick base side 34r and the negative electrode second comb tooth 54 having a thin tip side 54t and a thick base side 54r, the internal resistance can be reduced while suppressing the decrease in capacity. In particular, in the energy storage device 10, the shapes and dimensions of the positive electrode first comb teeth 32 and the positive electrode second comb teeth 34 and the negative electrode first comb teeth 52 and the negative electrode second comb teeth 54 are suitable, so it is presumed that a good balance is achieved between reducing internal resistance and suppressing capacity reduction, thereby enabling the energy density of the energy storage device 10 to be increased.

[0036] This electricity storage device 10 has a current density of 6.32 mA / cm 2 The energy density when discharged at (equivalent to 2C) is 0.8mWh / cm 2 More than 1mWh / cm is preferable. 2 More preferably, 1.2 mWh / cm 2 More preferably, the current density is 6.32 mA / cm. 2 The energy density when discharged is 3mWh / cm 2 The power storage device 10 may have a current density of 9.48 mA / cm 2 The energy density when discharged at (equivalent to 3C) is 0.0060mWh / cm 2 More than 0.0062 mWh / cm is preferable. 2 More preferably, 0.0064 mWh / cm 2 More preferably, the current density is 9.48 mA / cm 2 The energy density when discharged is 0.010 mWh / cm 2The power storage device 10 may have a current density of 12.64 mA / cm 2 When discharged at 4C (equivalent), the energy density is 0.0019mWh / cm 2 More than 0.0021 mWh / cm is preferable. 2 More preferably, 0.0023 mWh / cm or more. 2 More preferably, the current density is 12.64 mA / cm 2 The energy density when discharged is 0.0035mWh / cm 2 The current density is a value per area of ​​the width W × depth D of the power storage device 10. The energy density is a value per area of ​​the width W × thickness T of the power storage device 10.

[0037] It goes without saying that the present disclosure is in no way limited to the above-described embodiment, and can be embodied in various forms as long as it falls within the technical scope of the present disclosure.

[0038] For example, in the above-described embodiment, both the positive electrode 20 and the negative electrode 40 are electrodes of the present disclosure, but one of the positive electrode 20 and the negative electrode 40 may be an electrode of the present disclosure. In addition, in the above-described embodiment, the positive electrode 20 and the negative electrode 40 are exemplified as electrodes, but since whether it is the positive electrode 20 or the negative electrode 40 is determined by the relative potential, the above-described positive electrode 20 may be used as the negative electrode, or the above-described negative electrode 40 may be used as the positive electrode.

[0039] In the above-described embodiment, the number of the positive electrode comb teeth 30 and the negative electrode comb teeth 50 are the same, but the number of the positive electrode comb teeth 30 may be increased, or the number of the negative electrode comb teeth 50 may be increased. In addition, although one positive electrode third comb tooth 36 and one negative electrode first comb tooth 56 are provided, one or both of them may be omitted.

[0040] The present disclosure may be any one of the following [1] to [7]. [1] An electrode composed of an electrode mixture containing an electrode active material, the electrode comprising: a plate-shaped base; a plurality of comb teeth spaced apart in a predetermined direction on a main surface of the base; and comb grooves formed by side surfaces of adjacent comb teeth and the main surface of the base between the side surfaces, the comb teeth including first comb teeth that are rectangular parallelepiped-shaped and have a length in the predetermined direction of 100 μm or less; and second comb teeth that are stepped-shaped with a tip side that is thinner than a base side, the length in the predetermined direction being the same as or larger than the first comb teeth, being 200 μm or less on the base side, and 100 μm or less on the tip side, the first comb teeth and the second comb teeth are arranged alternately, and the electrode mixture has an ionic resistance of 15 Ωm or more. [2] The electrode described in [1], wherein the length of the first comb tooth in the specified direction is 30 μm or more and 70 μm or less, and the length of the second comb tooth in the specified direction is 50 μm or more and 130 μm or less on the base side and 10 μm or more and 50 μm or less on the tip side. [3] An electricity storage device comprising: a positive electrode which is the electrode according to [1] or [2], the ionic resistance of the electrode composite being 30 Ωm or more; a negative electrode which is the electrode according to [1] or [2], the ionic resistance of the electrode composite being 15 Ωm or more; and an ion conductive medium interposed between the comb grooves of the positive electrode and the comb teeth of the negative electrode arranged to enter the comb grooves, and between the comb grooves of the negative electrode and the comb teeth of the positive electrode arranged to enter the comb grooves, and between the comb grooves of the negative electrode and the comb teeth of the positive electrode arranged to enter the comb grooves, and conducting carrier ions. [4] The energy storage device described in [3], wherein the first comb teeth of the positive electrode have the same shape and dimensions as the first comb teeth of the negative electrode, and the second comb teeth of the positive electrode have the same shape and dimensions as the second comb teeth of the negative electrode. [5] The energy storage device described in [3] or [4], wherein the first comb tooth of the positive electrode and the first comb tooth of the negative electrode have a length in the specified direction of 30 μm or more and 70 μm or less, and the second comb tooth of the positive electrode and the second comb tooth of the negative electrode have a length in the specified direction of 50 μm or more and 130 μm or less on a base side and 10 μm or more and 50 μm or less on a tip side. [6] An electricity storage device comprising the electrode according to [1] or [2]. [7] Current density 6.32mA / cm 2 When discharged, the energy density is 0.8 mWh / cm2 The electricity storage device according to any one of [3] to [6] above. EXAMPLES

[0041] Examples in which the electricity storage device of the present disclosure has been specifically examined will be described below as examples, with Experimental Examples 1 to 7 corresponding to Examples and Experimental Examples 8 and 9 corresponding to Comparative Examples.

[0042] [Electricity storage device] In Experimental Examples 1 to 9, the power storage devices of Figs. 2A to 2D, 3A to 3D, and 4 were examined. Figs. 2A to 2D, 3A to 3D, and 4 correspond to the front view of Fig. 1. Figs. 2B to 2D show only dimensions different from Fig. 2A. Figs. 3B to 3D show only dimensions different from Fig. 3A. In all of the power storage devices of Experimental Examples 1 to 9, the thickness T (thickness excluding the current collector) was 600 μm and the depth D was 3000 μm. The thickness of the separator (separation film) was 20 μm. In Experimental Examples 1 to 9, the positive electrode active material was lithium iron phosphate (LFP). The negative electrode active material was lithium titanate (LTO). The ion-conducting medium (ion-conducting membrane) was a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of 1:2, with 1.0M LiPF 6 The gel electrolyte was composed of an electrolyte solution containing the above and a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP). The content of the positive electrode active material was 50% by volume with respect to the total volume of the positive electrode 20, and the content of the negative electrode active material was 42.1% by volume with respect to the total volume of the negative electrode. The positive electrode 20 was a porous body, and its porosity was 26.3% by volume. The negative electrode was a porous body, and its porosity was 38.3% by volume. The ionic resistance of the positive electrode composite was 128.18 Ωm, and the ionic resistance of the negative electrode composite was 46.46 Ωm. Specific dimensions and the like of Experimental Examples 1 to 9 will be described below.

[0043] (Experimental Example 1) The electricity storage device of FIG. 2A was examined. p and the thickness of the negative electrode base t n The positive electrode first comb teeth and the negative electrode first comb teeth each have 9 teeth and a width w p1and w n1 The positive electrode second comb teeth and the negative electrode second comb teeth each have 10 teeth, and the width of the tip side w p2t and w n2t is 40 μm, and the length of the tip side h p2t and h n2t 240μm, width at the base w p2r and w n2r is 100 μm, and the length of the base side h p2r and h n2r The positive electrode third comb tooth and the negative electrode third comb tooth each have one tooth and a width w p3 and w n3 The width W of the electricity storage device was 2600 μm. (Experimental Example 2) The electricity storage device of FIG. 2B was examined. The width w p1 and the width of the negative electrode first comb tooth w n1 is 40 μm, and the width of the third comb tooth of the positive electrode w p3 and the width of the negative electrode third comb tooth w n3 The thickness of the conductive layer was 50 μm, and the other factors were the same as in Experimental Example 1. The width W of the electricity storage device was 3000 μm. (Experimental Example 3) The electricity storage device of FIG. 2C was examined. The width w p1 and the width of the negative electrode first comb tooth w n1 is 60 μm, and the width of the third comb tooth of the positive electrode w p3 and the width of the negative electrode third comb tooth w n3 The thickness of the conductive layer was 70 μm, and the other factors were the same as in Experimental Example 1. The width W of the electricity storage device was 3400 μm. (Experimental Example 4) The electricity storage device of FIG. 2D was examined. The width w p1 and the width of the negative electrode first comb tooth w nl is 80 μm, and the width of the third comb tooth of the positive electrode w p3 and the width of the negative electrode third comb tooth w n3 The thickness of the conductive layer was 90 μm, and other than that, the experiment was conducted in the same manner as in Experimental Example 1. The width W of the electricity storage device was 3800 μm. (Experimental Example 5) The electricity storage device of FIG. 3A was examined. The width w p2t and the width w of the tip side of the negative electrode second comb tooth n2t is 20 μm, and the width of the root side of the second comb tooth of the positive electrode w p2r and the width w of the root side of the negative electrode second comb tooth n2rThe experiment was conducted in the same manner as in Experimental Example 3, except that the thickness was 60 μm. The width W of the electricity storage device was 2800 μm. (Experimental Example 6) The electricity storage device of FIG. 3B was examined. The width w p2t and the width w of the tip side of the negative electrode second comb tooth n2t is 60 μm, and the width of the root side of the second comb tooth of the positive electrode w p2r and the width w of the root side of the negative electrode second comb tooth n2r The thickness of the conductive layer was 140 μm, and the other conditions were the same as in Experimental Example 3. The width W of the electricity storage device was 4000 μm. (Experimental Example 7) The electricity storage device of FIG. 3C was examined. The width w p2t and the width w of the tip side of the negative electrode second comb tooth n2t is 80 μm, and the width of the root side of the second comb tooth of the positive electrode w p2r and the width w of the root side of the negative electrode second comb tooth n2r The experiment was conducted in the same manner as in Experimental Example 3, except that the thickness was 180 μm. The width W of the electricity storage device was 4600 μm. (Experimental Example 8) The electricity storage device of FIG. 3D was examined. The width w p2t and the width w of the tip side of the negative electrode second comb tooth n2t is 100 μm, and the width of the root side of the second comb tooth of the positive electrode w p2r and the width w of the root side of the negative electrode second comb tooth n2r The thickness of the power storage device was 220 μm, and the other factors were the same as in Experimental Example 3. The width W of the power storage device was 5200 μm. (Experimental Example 9) The electricity storage device shown in FIG. 4 was examined. p and the thickness of the negative electrode base t n The positive electrode first comb teeth and the negative electrode first comb teeth were absent. The positive electrode second comb teeth and the negative electrode second comb teeth were each 10 in number, and the width at the tip side w p2t and w n2t is 100 μm, and the length of the tip side h p2t and h n2t 240μm, width at base w p2r and w n2r is 160 μm, and the length of the base side h p2r and h n2r The positive electrode third comb tooth was absent, and the negative electrode third comb tooth had one tooth and a width w n3was set to 50 μm. Experimental Example 9 is the optimum structure reported in Non-Patent Document 1. This structure is optimized in Non-Patent Document 1 under the conditions that the positive electrode active material is lithium manganese oxide (LMO), the negative electrode active material is graphite, and the volume ratio of the positive electrode:negative electrode is 5:5.

[0044] [evaluation] The energy density of the energy storage devices of Experimental Examples 1 to 9 was evaluated by continuum simulation using the COMSOL Multiphysics Software package. In the continuum simulation, the battery model (a model combining porous electrode theory and concentrated solution theory) described in the above-mentioned Reference 2 (Doyle, et al., J. Electrochem. Soc., 143, 1890 (1996).) was used. The parameters of the electrode materials used in the simulation are summarized in Table 1. For other details, including the parameters of the electrolyte, refer to Reference 5 (Miyamoto et al., Cell Rep. Phys. Sci., 2, 100504 (2021)). In addition, for the energy storage devices with the same structure as Experimental Example 3 or Experimental Example 9 but with different positive and negative electrode composites, the energy density was evaluated by the same continuum simulation as above, and the relationship between the ionic resistance of the positive and negative electrode composites and the energy density was evaluated. In this case, the ionic resistance of the composite electrode (ρ ion [Ωm]) and electrical conductivity (κ eff [S / m]) is inversely related (κ eff =1 / ρ ion The current density was defined as a plane consisting of the width W and depth D of the power storage device (for example, 2600 μm × 3000 μm in Experimental Example 1). The current density was calculated as XC = X × 3.16 mA / cm 2 In other words, 2C = 6.32mA / cm 2 , 3C=9.48mA / cm 2 , 4C=12.64mA / cm 2In addition, the energy density was defined in a plane defined by the width W and thickness T of the electricity storage device (for example, 2600 μm×600 μm in Experimental Example 1).

[0045] Table 2 summarizes the energy densities of Experimental Examples 1 to 9. As shown in Table 2, in Experimental Examples 1 to 7, the current density was 6.32 mA / cm 2 The energy density is higher than that of Experimental Example 9 at 6 mA / cm 2 It was found that the energy density can be increased when discharging at a high current density such as that described above. In Experimental Examples 1 to 6, the current density was 9.48 mA / cm 2 and current density 12.64mA / cm 2 Even at a current density of 9.48 mA / cm, the energy density was higher than that of Experimental Example 9, and it was found that the energy density can be increased even when discharging at a higher current density. In Experimental Example 3, the energy density was high at all current densities, and especially at a current density of 9.48 mA / cm 2 and current density 12.64mA / cm 2 In Experimental Example 2, the energy density was high at all current densities, especially at a current density of 6.32 mA / cm. 2 and current density 12.64mA / cm 2 In Experimental Example 5, the energy density was high at all current densities, and especially at a current density of 12.64 mA / cm 2 It was found that the energy density was the highest and most preferable.

[0046] Table 3 shows the relationship between the ionic resistance and the energy density of the positive and negative electrode composites for the electricity storage devices having the same structure as in Experimental Example 3 or Experimental Example 9 but using different positive and negative electrode composites. Current density: 6.32 mA / cm 2The energy density in the structure of Experimental Example 9 was larger for No. 1 to No. 5, but the structure of Experimental Example 3 was larger for No. 6, and thereafter the structure of Experimental Example 3 was larger. Since the ionic resistance of the negative electrode composite of No. 5 was 14.69 Ωm and the ionic resistance of the negative electrode composite of No. 6 was 17.79 Ωm, it was inferred that if the ionic resistance of the electrode composite is 15 Ωm or more, the energy density can be increased by using the structure of Experimental Example 3. Considering that the ionic resistance of the positive electrode composite of No. 5 was 25.81 Ωm and the ionic resistance of the positive electrode composite of No. 6 was 33.71 Ωm, it was inferred that if the ionic resistance of the negative electrode composite is 15 Ωm or more and the ionic resistance of the positive electrode composite is 30 Ωm or more, the energy density can be further increased by using the structure of Experimental Example 3. In addition, in No. 8, in which the ionic resistance of the positive electrode composite was 57.52 Ωm and the ionic resistance of the negative electrode composite was 26.12 Ωm, the energy density of the structure of Experimental Example 3 exceeded the energy density of the structure of Experimental Example 9 at all current densities. This suggests that when the ionic resistance of the positive electrode composite is 50 Ωm or more and the ionic resistance of the negative electrode composite is 24 Ωm or more, the energy density can be increased even at higher current densities by using the structure of Experimental Example 3. It is speculated that the same applies to Examples other than Experimental Example 3.

[0047] [Table 1]

[0048] [Table 2]

[0049] [Table 3] [Industrial Applicability]

[0050] The present disclosure is applicable to the field of electricity storage devices. [Explanation of symbols]

[0051] 10 Electricity storage device, 20 Positive electrode, 22 Positive electrode base, 22a Main surface, 22b surface, 30 Positive electrode comb tooth, 30a Side, 32 Positive electrode first comb tooth, 34 Positive electrode second comb tooth, 34r Root side, 34s ​​Step, 34t Tip side, 36 Positive electrode third comb tooth, 38 Positive electrode comb groove, 40 Negative electrode, 42 Negative electrode base, 42a Main surface, 44b surface, 50 Negative electrode comb tooth, 50a Side, 52 Negative electrode first comb tooth, 54 Negative electrode second comb tooth, 54r Root side, 54s Step, 54t Tip side, 56 Negative electrode third comb tooth, 58 Negative electrode comb groove, 60 Ion conductive medium (separation membrane), 62 Positive electrode current collector, 64 Negative electrode current collector.

Claims

1. an electrode mixture containing an electrode active material, the electrode mixture having a plate-shaped base, a plurality of comb teeth provided at intervals in a predetermined direction on a main surface of the base, and comb grooves formed by side surfaces of adjacent comb teeth and the main surface of the base between the side surfaces, the comb teeth including first comb teeth in a rectangular parallelepiped shape and a length in the predetermined direction of 100 μm or less, and second comb teeth in a stepped shape whose tip side is thinner than whose base side, and whose length in the predetermined direction is the same as or larger than the first comb teeth, 200 μm or less on the base side and 100 μm or less on the tip side, the first comb teeth and the second comb teeth are alternately arranged, and the electrode mixture has an ionic resistance of 15 Ωm or more; electrode.

2. The first comb teeth have a length in the predetermined direction of 30 μm or more and 70 μm or less, The second comb teeth have a length in the predetermined direction of 50 μm or more and 130 μm or less on a base side and 10 μm or more and 50 μm or less on a tip side.

2. The electrode of claim 1.

3. 2. The electrode according to claim 1, wherein the electrode mixture has an ionic resistance of 30 Ωm or more; and 2. The electrode according to claim 1, wherein the electrode mixture has an ionic resistance of 15 Ωm or more; and an ion conductive medium that is interposed between the comb grooves of the positive electrode and the comb teeth of the negative electrode that are arranged so as to enter the comb grooves, and between the comb grooves of the negative electrode and the comb teeth of the positive electrode that are arranged so as to enter the comb grooves, and that conducts carrier ions; Energy storage device.

4. 4. The power storage device according to claim 3, wherein the first comb teeth of the positive electrode have the same shape and dimensions as the first comb teeth of the negative electrode, and the second comb teeth of the positive electrode have the same shape and dimensions as the second comb teeth of the negative electrode.

5. The first comb teeth of the positive electrode and the first comb teeth of the negative electrode have a length in the predetermined direction of 30 μm or more and 70 μm or less, The second comb teeth of the positive electrode and the second comb teeth of the negative electrode have a length in the predetermined direction of 50 μm or more and 130 μm or less on a base side and 10 μm or more and 50 μm or less on a tip side. The electricity storage device according to claim 4 .

6. An electricity storage device comprising the electrode according to claim 1.

7. Current density 6.32mA / cm 2 When discharged, the energy density is 0.8 mWh / cm 2 The above-mentioned electric storage device according to any one of claims 3 to 6.

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