Energy storage devices

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] This disclosure relates to electrodes and energy storage devices. [Background technology]

[0002] Conventionally, energy storage devices have been proposed that use electrodes as positive and negative electrodes, which are composed of an electrode composite material containing an electrode active material, and have a plate-shaped base, a plurality of comb teeth provided on the main surface of the base at predetermined intervals in a specific direction, and comb grooves formed by the sides of adjacent comb teeth and the main surface of the base between those sides (see, for example, Non-Patent Document 1). Non-Patent Document 1 describes how the shape of the comb teeth of the positive and negative electrodes is adjusted to improve energy density, etc. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Miyamoto et al., J. Power Sources, 536, 231473 (2022). [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, while the energy storage device described in Non-Patent Document 1 can increase energy density, it does not consider the case where the ionic resistance of the electrode composite material is high. Therefore, it was desired to increase the energy density of the energy storage device when using an electrode composite material with high ionic resistance.

[0005] This disclosure was made to solve these problems, and its main purpose is to increase the energy density of an energy storage device when using electrode composite materials with high ion resistance. [Means for solving the problem]

[0006] Through diligent research to achieve the above-mentioned objectives, the present inventors have discovered that when using an electrode composite material with an ion resistance of 15 Ωm or more, the energy density of the energy storage device can be increased by using electrodes in which a first comb tooth, which is rectangular in shape and has a width of 100 μm or less, and a second comb tooth, which is stepped in shape with a tip that is narrower than the base, and whose base width is between the first comb tooth and 200 μm or less and whose tip width is 100 μm or less, are arranged alternately, and have completed the invention disclosed herein.

[0007] In other words, the electrode of this disclosure is The electrode composite material comprises an electrode active material, a plate-shaped base, a plurality of comb teeth provided on the main surface of the base at intervals in a predetermined direction, and comb grooves formed by the sides of adjacent comb teeth and the main surface of the base between those sides, wherein the comb teeth consist of a first comb tooth with a rectangular parallelepiped shape and a length of 100 μm or less in the predetermined direction, and a second comb tooth with a stepped shape where the tip is narrower than the root, and the length in the predetermined direction is between 200 μm and 100 μm at the root and between at the tip, with the first and second comb teeth arranged alternately, and the electrode composite material having an ion resistance of 15 Ωm or more.

[0008] Furthermore, the energy storage device disclosed herein is The electrode described above, wherein the positive electrode has an ionic resistance of 30 Ωm or more, The electrode is as described above, and the negative electrode has an ionic resistance of 15 Ωm or more of the electrode composite material, The device comprises an ion-conducting medium interposed between the comb grooves of the positive electrode and the comb teeth of the negative electrode, which are arranged to fit into the comb grooves, and between the comb grooves of the negative electrode and the comb teeth of the positive electrode, which are arranged to fit into the comb grooves, and which conducts carrier ions.

[0009] Alternatively, the energy storage device of this disclosure is equipped with the electrodes described above. [Effects of the Invention]

[0010] In this electrode and energy storage device, the energy density of the energy storage device can be increased when an electrode composite material with high ion resistance, such as 15 Ωm or more, is used. The reason for this effect is presumed to be as follows: In energy storage devices with high ion resistance, ion resistance is the main factor in internal resistance. Therefore, by reducing the width of the comb teeth and decreasing the distance ions travel, the internal resistance of the energy storage device can be reduced. On the other hand, if the width of all the comb teeth is narrowed from the root to the tip, the proportion of space required to separate the positive electrode and the negative electrode increases, reducing the proportion of positive electrode composite material and negative electrode composite material, and thus reducing the capacity of the energy storage device. Therefore, by using comb teeth that are narrow at the tip and wide at the root, it is possible to reduce internal resistance while suppressing capacity reduction. In this disclosure, a rectangular parallelepiped first comb tooth and a stepped second comb tooth are used, and their dimensions are suitable, so it is presumed that a good balance is achieved between reducing internal resistance and suppressing capacity reduction, thereby increasing the energy density of the energy storage device. [Brief explanation of the drawing]

[0011] [Figure 1] An explanatory diagram showing the general configuration of the energy storage device 10. [Figure 2] An explanatory diagram showing the general configuration of the energy storage devices in Experimental Examples 1-4. [Figure 3] An explanatory diagram showing the general configuration of the energy storage devices in Experimental Examples 5-8. [Figure 4] An explanatory diagram showing the general configuration of the energy storage device in Experimental Example 9. [Modes for carrying out the invention]

[0012] The energy storage device of the present disclosure, as described in the embodiments, comprises a positive electrode, a negative electrode, and an ion-conducting medium. This energy storage device may include a positive electrode current collector electrically connected to the positive electrode, or a negative electrode current collector electrically connected to the negative electrode. This energy 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, or an alkali metal ion battery. Examples of carrier ions for the energy 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. For the sake of explanation, a lithium-ion secondary battery, which uses lithium ions as carrier ions, will be described below as the main example.

[0013] Embodiments of the electrodes and energy storage devices of this disclosure will be described below with reference to the drawings. Figure 1 is an explanatory diagram showing a schematic configuration of an energy storage device 10, which is an example of an energy storage device of this disclosure. The energy storage device 10 comprises a positive electrode 20, which is an example of an electrode of this disclosure, a negative electrode 40, which is an example of an electrode of this disclosure, an ion conducting medium 60, a positive electrode current collector 62, and a negative electrode current collector 64. The energy storage device 10 is arranged such that the positive electrode 20 and the negative electrode 40 face each other via the ion conducting medium 60. The energy storage device 10 may have, for example, a thickness T of 100 μm or more and 30,000 μm or less in the direction in which the positive electrode 20 and the negative electrode 40 face each other (left-right direction in Figure 1), a width W of, for example, 500 μm or more and 30,000 μm or less in the direction in which the positive electrode comb teeth 30 and the negative electrode comb teeth 50 described later are alternately arranged (up-down direction in Figure 1), and a depth D of 100 μm or more and 30,000 μm or less in the direction perpendicular to the thickness and width directions. An energy storage device 10 with such dimensions can be suitably used as a microbattery for powering IoT (Internet of Things) devices, etc. In this energy storage device 10, the positive electrode 20, negative electrode 40, ion conducting medium 60, positive electrode current collector 62, and negative electrode current collector 64 may appear in the same shape as the cross-section appearing in the foreground of Figure 1, regardless of which cross-section is cut by a plane parallel to the plane of Figure 1.

[0014] The positive electrode 20 is composed 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 on the main surface 22a of the positive electrode base 22 at intervals in a predetermined direction (hereinafter also referred to as the width direction; vertical direction in Figure 1), and a positive electrode comb groove 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 located between the side surfaces 30a, 30a. The predetermined direction can be any direction parallel to the main surface 22a. The thickness t of the positive electrode base 22 is the length in the direction perpendicular to the main surface 22a of the positive electrode base 22 (left-right direction in Figure 1). p This thickness t 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 energy density, it is preferable for the positive electrode base to be 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 energy storage device 10, and the depth of the positive electrode base 22 may be the same as the depth D of the energy storage device 10. The positive electrode comb teeth 30 are erected approximately perpendicular to the main surface 22a of the positive electrode base 22. The height h of the positive electrode comb teeth 30 p This height h may be 100 μm or more, 200 μm or more, or 400 μm or more. pThe thickness is preferably 30,000 μm or less, but may also be 800 μm or less, or 600 μm or less. The depth of the positive electrode comb teeth 30 may be the same as the depth D of the energy storage device 10. The number of 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 conducting 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 spacing between adjacent positive electrode comb teeth 30, 30, may be set appropriately so that the ion conducting 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. Also, the width of the positive electrode comb groove 38 may be 150 μm or less, 120 μm or less, or 100 μm or less. Furthermore, it is preferable that the width of the positive electrode comb groove 38 is within the above-mentioned numerical range in the portion closer to the positive electrode base 22 than the step 34s.

[0015] The positive electrode 20 has positive electrode comb teeth 30, which consist of positive electrode first comb teeth 32 and positive electrode second comb teeth 34, arranged alternately. In this case, nine positive electrode first comb teeth 32 and ten positive electrode second comb teeth 34 are arranged alternately. The positive electrode 20 also has positive electrode third comb teeth 36 as part of the positive electrode comb teeth 30. The positive electrode third comb teeth 36 are positioned outside at least one of the positive electrode first comb teeth 32 and positive electrode second comb teeth 34 that are located at both ends. In Figure 1, the positive electrode third comb teeth 36 are positioned outside (below) the positive electrode second comb teeth 34 located at the lower end.

[0016] The positive electrode first comb teeth 32 are rectangular parallelepiped in shape, with both sides 30a, 30a being planar. The positive electrode first comb teeth 32 have a width w which is the length in the predetermined direction described above. p1 This width is less than 100 μm. p1 The width w is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more. p1 The particle size is preferably 80 μm or less, more preferably 70 μm or less, and even more preferably 60 μm or less.

[0017] The second comb tooth 34 of the positive electrode has a stepped shape in which the tip side 34t is thinner than the root side 34r, and has a structure in which the rectangular parallelepiped-shaped tip side 34t and the rectangular parallelepiped-shaped root side 34r are joined. One of the side surfaces 30a, 30a of the second comb tooth 34 of the positive electrode is flat, and the other has a step 34s. The root side 34r of the second comb tooth 34 of the positive electrode has a width w which is the length in the above-mentioned predetermined direction p2r is the width w of the first comb tooth 32 of the positive electrode p1 and is 200 μm or less and more than 0. This width w p2r is preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 80 μm or more. This width w p2r is preferably 180 μm or less, more preferably 150 μm or less, and even more preferably 130 μm or less. Also, the ratio w p2r / w p1 should be 1 or more, and may be 1.2 or more, 1.5 or more, or 2 or more. The ratio w p2r / w p1 may be 4 or less, 3 or less, or 2.5 or less. The tip side 34t of the second comb tooth 34 of the positive electrode has a width w which is the length in the above-mentioned predetermined direction p2t and is 100 μm or less. This width w p2t is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more. This width w p2t is preferably 80 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less. The width w of the tip side 34t of the second comb tooth 34 of the positive electrode p2t should be smaller than the width w of the root side of the second comb tooth 34 of the positive electrode p2r but the ratio w p2t / w p2r may be 3 / 4 or less, 2 / 3 or less, or 1 / 2 or less. The ratio w p2t / w p2r may be 1 / 4 or more. Also, the difference w p2r -w p2t may be 100 μm or less, 80 μm or less, or 60 μm or less. The difference w p2r -w p2t may be 10 μm or more, 20 μm or more, or 30 μm or more. The height h of the tip side 34t of the second comb tooth 34 of the positive electrodep2t The height h is the root side of the positive electrode second comb tooth 34. p2r It is preferable that it be of a similar degree, and ratio h p2t / h p2r Preferably, the ratio is 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 tooth 36 has a rectangular parallelepiped shape, and its side surface 30a is planar. The positive electrode third comb tooth 36 has a width w which is the length in the predetermined direction described above. p3 It may be assumed that this width w is 100 μm or less. p3 The width w is preferably 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more. p3 The width of the third comb tooth 36 of the positive electrode is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less. p3 The width of the first comb tooth 32 of the positive electrode is w p1 It can be considered to be of a similar degree, and the width of the first comb tooth 32 of the positive electrode w p1 It can be larger than, but compared to w p3 / w p1 It 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 ionic resistance of the positive electrode composite material of this positive electrode 20 is 15 Ωm or more in resistivity. Preferably, the ionic resistance of the positive electrode composite material is 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 determined, for example, by impedance analysis as described in Reference 1 (Ogihara et al., J. Electrochem. Soc., 159, A1034 (2012)), or, for example, by determining the effective conductivity of the composite electrode from information on the conductivity of the electrolyte and the porosity of the composite electrode, and taking the reciprocal thereof, as described in Reference 2 (Doyle et al., J. Electrochem. Soc., 143, 1890 (1996)). The ion resistance of the positive electrode composite material is greatly influenced by the material of the positive electrode active material, and is particularly high 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 intercalating and deintercalating lithium ions, for example, a compound having lithium and a transition metal, such as an oxide containing lithium and a transition metal element, or a phosphoric acid compound containing lithium and a transition metal element. Specifically, the basic composition formula may be Li (1-x) MnO2 (0≦x≦1, etc., the same applies below) and Li (1-x) Lithium manganese composite oxides such as Mn2O4, with the basic composition formula being Li (1-x) Lithium cobalt composite oxides such as CoO2, with the basic composition formula being Li (1-x) Lithium nickel composite oxides such as NiO2, with the basic composition formula being Li (1-x) Co a Ni b Mn c O2(a>0, b>0, c>0, a+b+c=1), Li (1-x) Co a Ni b Mn cLithium cobalt nickel manganese composite oxides such as O4 (0 < a < 1, 0 < b < 1, 1 ≤ c < 2, a + b + c = 2), lithium vanadium composite oxides with a basic composition formula such as LiV2O3, transition metal oxides with a basic composition formula such as V2O5, etc. can be used. Also, lithium iron phosphate compounds with a basic composition formula such as LiFePO4 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. Note that the "basic composition formula" means that it may contain other elements, for example, components such as Al and Mg. The conductive material is not particularly limited as long as it is an electron-conductive material that does not adversely affect battery performance. For example, graphite such as natural graphite (scaly graphite, flaky graphite) and artificial graphite, acetylene black, carbon black, ketjen black, carbon whiskers, needle coke, carbon fibers, metals (copper, nickel, aluminum, silver, gold, etc.), or a mixture of one or more of these can be used. The binder serves to hold the active material particles and conductive material particles together and maintain a predetermined shape. For example, fluorine-containing resins such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), and fluororubber, or thermoplastic resins such as polypropylene and polyethylene, ethylene propylene diene monomer (EPDM) rubber, sulfonated EPDM rubber, natural butyl rubber (NBR), etc. can be used alone or as a mixture of two or more. Also, aqueous binders such as aqueous dispersions of cellulose-based or styrene butadiene rubber (SBR) can be used. In the positive electrode 20, the content of the positive electrode active material is preferably higher, preferably 60% by mass or more, more preferably 70% by mass or more, based on the total mass of the positive electrode 20. In the positive electrode 20, the content of the positive electrode active material may be 99% by mass or less. In the positive electrode 20, the content of the positive electrode active material may be 30% to 70% by volume, or 40% to 60% by volume, based on the total volume of the positive electrode 20. The positive electrode 20 may be a porous body, and its porosity may be 10% to 40% by volume, or 20% to 30% by volume. The voids of the positive electrode 20 may be filled with a non-aqueous electrolyte due to the ion conduction medium 60, etc.

[0021] The negative electrode 40 is composed 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 on the main surface 42a of the negative electrode base 42 at intervals in a predetermined direction (hereinafter also referred to as the width direction; vertical direction in Figure 1), and a negative electrode comb groove 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 located 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 is the length in the direction perpendicular to the main surface 42a of the negative electrode base 42 (left-right direction in Figure 1). n This thickness t 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 energy density, it is preferable for the negative electrode base to be 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 energy storage device 10, and the depth of the negative electrode base 42 may be the same as the depth D of the energy storage device 10. The negative electrode comb teeth 50 are erected substantially perpendicular to the main surface 42a of the negative electrode base 42. The height h of the negative electrode comb teeth 50 n This height h may be 100 μm or more, 200 μm or more, or 400 μm or more. nThe thickness is preferably 30,000 μm or less, but may also be 800 μm or less, or 600 μm or less. The depth of the negative electrode comb teeth 50 may be the same as the depth D of the energy storage device 10. The number of 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 conducting medium 60 and the positive electrode comb teeth 30 described above are arranged in the negative electrode comb groove 58. The width of the negative electrode comb groove 58, that is, the spacing between adjacent negative electrode comb teeth 50, 50, may be set appropriately so that the ion conducting medium 60 and 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. Also, the width of the negative electrode comb groove 58 may be 150 μm or less, 120 μm or less, or 100 μm or less. Furthermore, it is preferable that the width of the negative electrode comb groove 58 is within the above-mentioned numerical range in the portion closer to the negative electrode base 42 than the step 54s. It is preferable that the negative electrode 40 has the same shape and dimensions as the positive electrode 20. For example, it is preferable that the negative electrode base 42 has the same shape and dimensions as the positive electrode base 22. It is also preferable that the negative electrode comb teeth 50 have the same shape and dimensions as the positive electrode comb teeth 30. Furthermore, it is preferable that the negative electrode comb groove 58 has the same shape and dimensions as the positive electrode comb groove 38.

[0022] The negative electrode 40 has negative electrode comb teeth 50, which consist of negative electrode first comb teeth 52 and negative electrode second comb teeth 54, arranged alternately. Here, nine negative electrode first comb teeth 52 and ten negative electrode second comb teeth 54 are arranged alternately. The negative electrode 40 also has negative electrode third comb teeth 56 as part of the negative electrode comb teeth 50. The negative electrode third comb teeth 56 are positioned outside at least one of the negative electrode first comb teeth 52 and negative electrode second comb teeth 54 that are located at both ends. In Figure 1, the negative electrode third comb teeth 56 are positioned outside (above) the negative electrode second comb teeth 54 located at the upper end.

[0023] The first comb teeth 52 of the negative electrode are rectangular parallelepiped in shape, with both sides 50a, 50a being planar. The first comb teeth 52 of the negative electrode have a width w which is the length in the predetermined direction described above. n1 This width is less than 100 μm. n1The width w is preferably 20 μm or more, more preferably 30 μm or more, and even more preferably 40 μm or more. n1 The thickness 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 are preferably the same shape and dimensions as the positive electrode first comb teeth 32. The width w of the negative electrode first comb teeth 52 n1 The width w of the first comb teeth 32 of the positive electrode is determined according to the ionic resistance of the negative electrode composite material and the ionic resistance of the positive electrode composite material. p1 You can make it larger or smaller than that.

[0024] The negative electrode second comb tooth 54 has a stepped shape, with the tip side 54t being narrower than the root side 54r, and has a structure in which the rectangular parallelepiped tip side 54t and the rectangular parallelepiped root side 54r are joined. One of the sides 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 positioned so that this step 54s faces the step 34s of the positive electrode second comb tooth 34. The root side 54r of the negative electrode second comb tooth 54 has a width w, which is the length in the predetermined direction described above. n2r The width of the first comb tooth 52 of the negative electrode w n1 The width is less than or equal to 200 μm. n2r The width w is preferably 50 μm or more, more preferably 60 μm or more, and even more preferably 80 μm or more. n2r The particle size is preferably 180 μm or less, more preferably 150 μm or less, and even more preferably 130 μm or less. n2r / w n1 It is fine if it is 1 or more, 1.2 or more, 1.5 or more, or 2 or more. n2r / w n1 This may be 4 or less, 3 or less, or 2.5 or less. The tip side 54t of the negative electrode second comb teeth 54 has a width w which is the length in the predetermined direction described above. n2t This width is less than 100 μm. n2t The width w 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 second comb tooth 54 of the negative electrode is preferably 80 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less.n2t may be smaller than the width w at the base side of the second negative electrode comb tooth 54, but the ratio w n2r / w n2t / w n2r may be 3 / 4 or less, 2 / 3 or less, or 1 / 2 or less. The ratio w n2t / w n2r may be 1 / 4 or more. Also, the difference w n2r -w n2t may be 100 μm or less, 80 μm or less, or 60 μm or less. The difference w n2r -w n2t may be 10 μm or more, 20 μm or more, or 30 μm or more. The height h of the tip side 54t of the second negative electrode comb tooth 54 n2t is preferably approximately the same as the height h of the base side of the second negative electrode comb tooth 54, and the ratio h n2r / 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 second negative electrode comb tooth 54 is preferably the same shape and the same dimensions as the second positive electrode comb tooth 34. The width w of the tip side 54t of the second negative electrode comb tooth 54 n2t may be larger or smaller than the width w of the tip side 34t of the second positive electrode comb tooth 34 according to the ion resistance of the negative electrode composite material, the ion resistance of the positive electrode composite material, etc. Also, the width w of the base side 54r of the second negative electrode comb tooth 54 p2t may be larger or smaller than the width w of the base side 34r of the second positive electrode comb tooth 34 according to the ion resistance of the negative electrode composite material, the ion resistance of the positive electrode composite material, etc. However, it is preferable to make the difference w n2r -w p2r in the second negative electrode comb tooth 54 the same as the difference w n2r -w n2t in the second positive electrode comb tooth 34 because the thickness of the ion conduction medium 60 can be made constant. p2r -w p2t

[0025] The third negative electrode comb tooth 56 has a rectangular parallelepiped shape, and the side surface 50a is planar. The third negative electrode comb tooth 56 may have a width w n3 which is 100 μm or less as the length in the predetermined direction described above. This width w​n3 is preferably 30 μm or more, more preferably 40 μm or more, and even more preferably 50 μm or more. This width w n3 is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less. The width w of the third negative comb tooth 56 n3 may be of the same degree as the width w of the first negative comb tooth 52, n1 or may be larger than the width w of the first negative comb tooth 52, but the ratio w n1 / w n3 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 third negative comb tooth 56 is preferably the same shape and the same dimensions as the third positive comb tooth 36. The width w of the third negative comb tooth 56 n1 may be larger or smaller than the width w of the third positive comb tooth 36 according to the ionic resistance of the negative electrode composite material, the ionic resistance of the positive electrode composite material, etc. n3 p3

[0026] The negative electrode 40 is composed of a negative electrode composite material containing a negative electrode active material. The ionic resistance of this negative electrode 40 is 15 Ωm or more in terms of specific resistance of the negative electrode composite material. 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 obtained in the same manner as the ionic resistance of the positive electrode composite material. The ionic resistance of the negative electrode composite material is greatly affected by the material of the negative electrode active material, and particularly increases 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 also include a conductive material as needed. The negative electrode active material may be capable of intercalating and deintercalating lithium ions, and examples include inorganic compounds such as tin compounds, carbonaceous materials capable of intercalating and deintercalating 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, allow for charging and discharging at high operating voltages, suppress self-discharge when a lithium salt is used as a supporting salt, and 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. Among these, composite oxides such as lithium titanate are preferred as the negative electrode active material. The conductive material, binder, etc. used in the negative electrode 40 may be those exemplified for the positive electrode 20. In the negative electrode 40, the content of the negative electrode active material is preferably higher, preferably 60% by mass or more, and more preferably 70% by mass or more, relative to 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, relative to the total volume of the negative electrode 40. The negative electrode 40 may be a porous body, and its 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 non-aqueous electrolyte solution resulting from the ion conducting medium 60.

[0028] The ion-conducting medium 60 is interposed between the positive electrode 20 and the negative electrode 40. More specifically, the ion-conducting medium 60 is interposed between the positive electrode comb teeth 30 and the negative electrode comb groove 58, and between the positive electrode comb groove 38 and the negative electrode comb teeth 50. The ion-conducting medium 60 is positioned to fill the gaps between the positive electrode comb teeth 30 and the negative electrode comb groove 58, and between the positive electrode comb groove 38 and the negative electrode comb teeth 50. The thickness t of the ion-conducting medium 60 corresponds to this gap. s For example, it may be 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 ion-conducting medium 60 conducts lithium ions, which are carrier ions. The ion-conducting medium may be, for example, a non-aqueous electrolyte containing a supporting salt (supporting electrolyte) and an organic solvent. As the supporting salt, for example, when lithium ions are used as carriers in the positive electrode, it may contain known lithium salts. Examples of these lithium salts include LiPF6, LiBF4, LiClO4, LiAsF6, Li(CF3SO2)2N, and LiN(C2F5SO2)2, of which LiPF6 and LiBF4 are preferred. The concentration of this supporting salt in the non-aqueous electrolyte is preferably 0.1 mol / L or more and 5 mol / L or less, and 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 made more stable. In addition, flame retardants such as phosphorus-based and halogen-based agents may be added to this non-aqueous electrolyte. As the organic solvent, for example, an aprotic organic solvent can be used. Examples of such organic solvents include cyclic carbonates, linear carbonates, cyclic esters, cyclic ethers, and linear ethers. Examples of cyclic carbonates include ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate. Examples of linear carbonates include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Examples of cyclic ester carbonates include gamma-butyrolactone and gamma-valerolactone. Examples of cyclic ethers include tetrahydrofuran and 2-methyltetrahydrofuran. Examples of linear ethers include dimethoxyethane and ethylene glycol dimethyl ether. These may be used individually or in combination. In addition, nitrile solvents such as acetonitrile and propylnitrile, or ionic liquids may be used as non-aqueous electrolytes. Alternatively, aqueous electrolytes may be used instead of non-aqueous electrolytes.

[0030] The ion-conducting medium 60 may be an ion-conducting membrane containing a resin and the electrolyte described above. Examples of resins 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 copolymer of PVdF and HFP, a portion of the non-aqueous electrolyte swells and gels the membrane, forming an ion-conducting 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 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 to this; for example, it may be formed on a part of the surface 22b, or on the end face of the positive electrode 20 that allows a view to the back of the comb groove 30, i.e., on the entire surface or part of the front or back surface in Figure 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 can be made of aluminum, titanium, stainless steel, nickel, iron, calcined carbon, conductive polymer, conductive glass, etc., or aluminum or copper whose surfaces have been treated with carbon, nickel, titanium, or silver for the purpose of improving adhesion, conductivity, and oxidation resistance. Of these, aluminum is preferred. The positive electrode current collector 62 is particularly suitable for the positive electrode of a lithium secondary battery because it is less susceptible to lithium ion doping in the potential range in which it is used, and it has high corrosion resistance. The shape of the positive electrode current collector 62 can be a sheet, a net, a punched or expanded material, or a lath. Sheets include foils and films. The thickness of the positive electrode current collector 62 is preferably 10 μm to 20 μm, and more preferably 12 μm to 17 μm. If the thickness of the positive electrode current collector 62 is 10 μm or more, the mechanical strength of the positive electrode current collector 62 can be further increased. Also, if the thickness of the positive electrode current collector 62 is 20 μm or less, the volume fraction of the positive electrode current collector 62 in the energy storage device 10 can be reduced and the volume fraction of the positive electrode 20, etc., can be increased, thereby increasing the energy density of the energy storage device 10.

[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 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 to this; for example, it may be formed on a part of the surface 42b, or on the end face of the negative electrode 40 that allows a view to the back of the comb groove 50, i.e., on the entire surface or part of the front or back surface in Figure 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 can be made of copper, nickel, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., or, for the purpose of improving adhesion, conductivity, and reduction resistance, a surface treated with carbon, nickel, titanium, or silver, for example, can also be used. Of these, copper is preferred. This is because the negative electrode current collector 64 is particularly suitable for the negative electrode of a lithium secondary battery due to its low susceptibility to lithium ion doping in the potential range in which it is used, and its high corrosion resistance. The shape of the negative electrode current collector 64 can be a sheet, a net, a punched or expanded sheet, a lath, etc. The sheet shape includes foil and film shapes. The thickness of the negative electrode current collector 64 is preferably 5 μm to 15 μm, and more preferably 8 μm to 12 μm. If the thickness of the negative electrode current collector 64 is 5 μm or more, the mechanical strength of the negative electrode current collector 64 can be further increased. Also, if the thickness of the negative electrode current collector 64 is 15 μm or less, the volume fraction of the negative electrode current collector 64 in the energy storage device 10 can be reduced and the volume fraction of the negative electrode 40 etc. can be increased, thereby increasing the energy density of the energy storage device 10.

[0033] The thickness T of this energy storage device 10 may be, for example, 100 μm or more and 30,000 μm or less, 300 μm or more and 1,000 μm or less, 500 μm or more and 700 μm or less, or 600 μm. However, the thickness T excludes the positive electrode current collector 62 and the negative electrode current collector 64. The width W of this energy storage device 10 may be, for example, 500 μm or more and 30,000 μm or less, 1,000 μm or more and 7,000 μm or less, 2,000 μm or more and 5,000 μm or less, or 3,000 μm. The depth D of this energy storage device 10 may be, for example, 100 μm or more and 30,000 μm or less, 1,000 μm or more and 7,000 μm or less, 2,000 μm or more and 5,000 μm or less, or 3,000 μm.

[0034] The energy storage device 10 may be formed, for example, using 3D printing technology. When manufacturing the energy storage device 10 using 3D printing technology, for example, as described in Reference 3 (Sun et al., Adv. Mater., 25, 4539 (2013)), a 3D structure may be fabricated by first applying a high-viscosity electrode ink, then the 3D structure may be heated to remove liquids and polymers, and then an electrolyte may be injected for packaging. The electrode inks used for the positive and negative electrodes may, for example, have an active material content of 45% to 65% by mass, or 50% to 60% by mass. Alternatively, the energy storage device 10 may be formed using lithography technology, for example, as described in Reference 4 (Ning et al., Proc. Natl. Acad. Sci. USA, 112, 6573 (2015)).

[0035] In the energy storage device 10 of the embodiment described above, the energy density of the energy storage device 10 can be increased when an electrode composite material with high ion resistance, such as 15 Ωm or more, is used. In particular, the current density can be increased to 6 mA / cm². 2The energy density can be increased when discharge is performed at high current densities as described above. The reason for this effect can be inferred, for example, as follows: In the energy storage device 10, positive electrode composite material and negative electrode composite material with high ion resistance are used, and ion resistance is the main cause of internal resistance. Therefore, by reducing the width of the positive electrode first comb teeth 32 and the negative electrode first comb teeth 52 and reducing the distance ions travel, the internal resistance of the energy storage device 10 can be reduced. On the other hand, if the width of all positive electrode comb teeth 30 and negative electrode comb teeth 50 is narrowed from the root to the tip, the proportion of space required to separate the positive electrode 20 and the negative electrode 40 increases, the proportion of positive electrode composite material and negative electrode composite material decreases, and the capacity of the energy storage device 10 decreases. Therefore, by using positive electrode second comb teeth 34 with a narrow tip side 34t and a wide root side 34r, and negative electrode second comb teeth 54 with a narrow tip side 54t and a wide root side 54r, it is possible to reduce internal resistance while suppressing a decrease in capacity. In particular, in the energy storage device 10, the shape and dimensions of the positive electrode first comb teeth 32 and positive electrode second comb teeth 34, and the negative electrode first comb teeth 52 and negative electrode second comb teeth 54 are suitable, resulting in a good balance between reducing internal resistance and suppressing capacity degradation, which is presumed to increase the energy density of the energy storage device 10.

[0036] This energy storage device 10 has a current density of 6.32 mA / cm². 2 The energy density when discharged at (equivalent to 2C) is 0.8 mWh / cm². 2 The above is preferable, and 1 mWh / cm² 2 The above is more preferable, 1.2 mWh / cm² 2 The above is even more preferable. Current density 6.32 mA / cm² 2 The energy density when discharged is 3 mWh / cm². 2 The following may also be used. Furthermore, this energy storage device 10 has a current density of 9.48 mA / cm². 2 The energy density when discharged at (equivalent to 3C) is 0.0060 mWh / cm². 2 The above is preferable, and 0.0062 mWh / cm² 2 The above is more preferable, 0.0064 mWh / cm² 2 The above is even more preferable. Current density 9.48 mA / cm² 2 The energy density when discharged is 0.010 mWh / cm². 2The following may also be used. Furthermore, this energy storage device 10 has a current density of 12.64 mA / cm². 2 The energy density when discharged at (equivalent to 4C) is 0.0019 mWh / cm². 2 The above is preferable, and 0.0021 mWh / cm³ 2 The above is more preferable, 0.0023 mWh / cm² 2 The above is even more preferable. Current density 12.64 mA / cm² 2 The energy density when discharged is 0.0035 mWh / cm³. 2 The following may also be used. Note that the current density is the value per unit area of ​​the energy storage device 10 with width W × depth D. Also, the energy density is the value per unit area of ​​the energy storage device 10 with width W × thickness T.

[0037] It goes without saying that this disclosure is not limited in any way to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of this disclosure.

[0038] For example, in the embodiments described above, both the positive electrode 20 and the negative electrode 40 are electrodes of the present disclosure, but either the positive electrode 20 or the negative electrode 40 may be the electrode of the present disclosure. Also, in the embodiments described above, the positive electrode 20 and the negative electrode 40 were given as examples of electrodes, but since the choice between the positive electrode 20 and the negative electrode 40 is determined by the relative potential, the positive electrode 20 may be used as the negative electrode, or the negative electrode 40 may be used as the positive electrode.

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

[0040] This disclosure may be any of the following [1] to [7]. [1] An electrode comprising an electrode composite material containing an electrode active material, having a plate-shaped base, a plurality of comb teeth provided on the main surface of the base at intervals in a predetermined direction, and comb grooves formed by the side surfaces of adjacent comb teeth and the main surface of the base between those side surfaces, wherein the comb teeth include a first comb tooth which is rectangular in shape and has a length of 100 μm or less in the predetermined direction, and a second comb tooth which is stepped in shape with a tip that is narrower than the root, and has a length of 200 μm or less at the root and the same as or greater than the first comb tooth in the predetermined direction, and 100 μm or less at the tip, and the first comb teeth and the second comb teeth are arranged alternately, and the electrode composite material has an ion resistance of 15 Ωm or more. [2] The electrode according to [1], wherein the first comb teeth have a length of 30 μm or more and 70 μm or less in the predetermined direction, and the second comb teeth have a length of 50 μm or more and 130 μm or less at the root end and 10 μm or more and 50 μm or less at the tip end in the predetermined direction. [3] A power storage device comprising: a positive electrode, which is the electrode described in [1] or [2], wherein the ion resistance of the electrode composite material is 30 Ωm or more; a negative electrode, which is the electrode described in [1] or [2], wherein the ion resistance of the electrode composite material is 15 Ωm or more; and an ion conducting medium interposed between the comb groove of the positive electrode and the comb teeth of the negative electrode, which are arranged to fit into the comb groove, and between the comb groove of the negative electrode and the comb teeth of the positive electrode, which are arranged to fit into the comb groove, for conducting carrier ions. [4] The energy storage device according to [3], wherein the first comb teeth of the positive electrode are the same shape and dimensions as the first comb teeth of the negative electrode, and the second comb teeth of the positive electrode are the same shape and dimensions as the second comb teeth of the negative electrode. [5] The energy storage device according to [3] or [4], wherein the first comb teeth of the positive electrode and the first comb teeth of the negative electrode have a length of 30 μm or more and 70 μm or less in the predetermined direction, and the second comb teeth of the positive electrode and the second comb teeth of the negative electrode have a length of 50 μm or more and 130 μm or less at the root end and 10 μm or more and 50 μm or less at the tip end. [6] A power storage device comprising the electrodes described in [1] or [2]. [7] Current density 6.32mA / cm 2 The energy density when discharged is 0.8 mWh / cm².2 The above is a power storage device as described in any one of [3] to [6]. [Examples]

[0041] The following describes specific examples of the energy storage device described herein. Experimental Examples 1-7 are considered examples, while Experimental Examples 8-9 are considered comparative examples.

[0042] [Energy storage devices] In Experimental Examples 1-9, the energy storage devices shown in Figures 2A-2D, 3A-3D, and 4 were examined. Figures 2A-2D, 3A-3D, and 4 correspond to the front view in Figure 1. Figures 2B-2D only show dimensions that differ from Figure 2A. Figures 3B-3D only show dimensions that differ from Figure 3A. In all of the energy storage devices in Experimental Examples 1-9, the thickness T (thickness excluding the current collector) was 600 μm and the depth D was 3000 μm. The thickness of the separator (separation membrane) was 20 μm. In Experimental Examples 1-9, 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 gel electrolyte composed of an electrolyte solution made by adding 1.0 M LiPF6 to a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a volume ratio of EC:DMC = 1:2, and a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP). The content of the positive electrode active material was 50% by volume relative to the total volume of the positive electrode 20, and the content of the negative electrode active material was 42.1% by volume relative to the total volume of the negative electrode. The positive electrode 20 was a porous material with a porosity of 26.3% by volume. The negative electrode was a porous material with a porosity of 38.3% by volume. The ion resistance of the positive electrode composite was 128.18 Ωm, and the ion resistance of the negative electrode composite was 46.46 Ωm. The specific dimensions of Experimental Examples 1 to 9 are described below.

[0043] (Experimental Example 1) The energy storage device shown in Figure 2A was examined. The thickness t of the positive electrode base. p and the thickness t of the negative electrode base n The width was set to 50 μm. The positive electrode first comb teeth and the negative electrode first comb teeth each consisted of 9 teeth, with a width w p1 and wn1 The width was set to 20 μm. The positive electrode second comb teeth and the negative electrode second comb teeth each consisted of 10 teeth, with a width w at the tip. p2t and w n2t 40 μm, tip length h p2t and h n2t 240 μm, width at the base w p2r and w n2r 100 μm, root length h p2r and h n2r The width was set to 240 μm. The positive electrode third comb tooth and the negative electrode third comb tooth each consisted of one tooth with a width w p3 and w n3 The width was set to 30 μm. The width W of the energy storage device was 2600 μm. (Experimental Example 2) The energy storage device shown in Figure 2B was examined. The width of the first comb tooth of the positive electrode was w. p1 and the width of the first comb tooth of the negative electrode w n1 Let the width be 40 μm, and the width of the third comb tooth of the positive electrode w p3 and the width of the third comb tooth of the negative electrode w n3 The procedure was the same as in Experimental Example 1, except that the width was set to 50 μm. The width W of the energy storage device was 3000 μm. (Experimental Example 3) The energy storage device shown in Figure 2C was examined. The width of the first comb tooth of the positive electrode was w. p1 and the width of the first comb tooth of the negative electrode w n1 Let the width be 60 μm, and the width of the third comb tooth of the positive electrode w p3 and the width of the third comb tooth of the negative electrode w n3 The procedure was the same as in Experimental Example 1, except that the width was set to 70 μm. The width W of the energy storage device was 3400 μm. (Experimental Example 4) The energy storage device shown in Figure 2D was examined. The width of the first comb tooth of the positive electrode was w. p1 and the width of the first comb tooth of the negative electrode w nl Let the width be 80 μm, and the width of the third comb tooth of the positive electrode w p3 and the width of the third comb tooth of the negative electrode w n3 The procedure was the same as in Experimental Example 1, except that the width was set to 90 μm. The width W of the energy storage device was 3800 μm. (Experimental Example 5) The energy storage device shown in Figure 3A was examined. The width w of the tip side of the second comb tooth of the positive electrode. p2t and the width w of the tip side of the second comb tooth of the negative electrode n2t Let the width be 20 μm, and the width w at the root side of the second comb tooth of the positive electrode. p2r and the width w of the root side of the second tooth of the negative electrode comb. n2rThe procedure was the same as in Experimental Example 3, except that the width was set to 60 μm. The width W of the energy storage device was 2800 μm. (Experimental Example 6) The energy storage device shown in Figure 3B was examined. The width w of the tip side of the second comb tooth of the positive electrode. p2t and the width w of the tip side of the second comb tooth of the negative electrode n2t Let the width be 60 μm, and the width w at the root side of the second comb tooth of the positive electrode. p2r and the width w of the root side of the second tooth of the negative electrode comb. n2r The procedure was the same as in Experimental Example 3, except that the width was set to 140 μm. The width W of the energy storage device was 4000 μm. (Experimental Example 7) The energy storage device shown in Figure 3C was examined. The width w of the tip side of the second comb tooth of the positive electrode. p2t and the width w of the tip side of the second comb tooth of the negative electrode n2t Let the width be 80 μm, and the width w at the root side of the second comb tooth of the positive electrode. p2r and the width w of the root side of the second tooth of the negative electrode comb. n2r The procedure was the same as in Experimental Example 3, except that the width was set to 180 μm. The width W of the energy storage device was 4600 μm. (Experimental Example 8) The energy storage device shown in Figure 3D was examined. The width w of the tip side of the second comb tooth of the positive electrode. p2t and the width w of the tip side of the second comb tooth of the negative electrode n2t Let this be 100 μm, and the width w of the root side of the second comb tooth of the positive electrode. p2r and the width w of the root side of the second tooth of the negative electrode comb. n2r The procedure was the same as in Experimental Example 3, except that the width was set to 220 μm. The width W of the energy storage device was 5200 μm. (Experimental Example 9) The energy storage device shown in Figure 4 was examined. The thickness t of the positive electrode base. p and the thickness t of the negative electrode base n The diameter was set to 50 μm. The positive electrode first comb teeth and the negative electrode first comb teeth were omitted. The positive electrode second comb teeth and the negative electrode second comb teeth consisted of 10 teeth each, with a tip width w. p2t and w n2t 100 μm, tip length h p2t and h n2t 240 μm, width at the base w p2r and w n2r 160 μm, root length h p2r and h n2r The width was set to 240 μm. The positive electrode had no third comb teeth, and the negative electrode had one third comb tooth with a width of w. n3The thickness was set to 50 μm. Experimental Example 9 is the optimal structure reported in Non-Patent Literature 1. This structure is the optimized structure in Non-Patent Literature 1 under the conditions that the positive electrode active material is lithium manganese composite oxide (LMO), the negative electrode active material is graphite, and the volume ratio of the positive electrode to the negative electrode is 5:5.

[0044] [evaluation] For the energy storage devices of Experimental Examples 1-9, the energy density was evaluated by continuum simulation using the COMSOL Multiphysics Software package. The battery model (a model combining porous electrode theory and concentrated solution theory) described in Reference 2 (Doyle, et al., J. Electrochem. Soc., 143, 1890 (1996)) was used for the continuum simulation. Table 1 summarizes the parameters of the electrode materials used in the simulation. For other details, including electrolyte parameters, please refer to Reference 5 (Miyamoto et al., Cell Rep. Phys. Sci., 2, 100504 (2021)). Furthermore, for 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 using 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 process, the ionic resistance (ρ) of the composite electrode was considered. ion [Ωm] and conductivity (κ eff [S / m]) has a reciprocal relationship (κ eff = 1 / ρ ion This was utilized. The current density was defined as the surface area composed of the width W and depth D of the energy storage device (for example, 2600 μm × 3000 μm in Experimental Example 1). The current density was given by XC = X × 3.16 mA / cm². 2 It is expressed as follows: 2C = 6.32mA / cm². 2 Therefore, 3C = 9.48mA / cm 2 Therefore, 4C = 12.64mA / cm² 2It was assumed that the energy density was defined by the surface formed by the width W and thickness T of the energy storage device (for example, 2600 μm × 600 μm in Experimental Example 1).

[0045] Table 2 summarizes the energy densities for Experimental Examples 1-9. As shown in Table 2, the current density for Experimental Examples 1-7 was 6.32 mA / cm². 2 In this case, the energy density was higher than in experimental example 9, at 6 mA / cm². 2 It was found that the energy density can be increased when discharging at high current densities as described above. In experimental examples 1-6, the current density was 9.48 mA / cm². 2 and current density 12.64 mA / cm² 2 In this case as well, the energy density was higher than in Experimental Example 9, indicating 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, especially at a current density of 9.48 mA / cm². 2 and current density 12.64 mA / cm² 2 It was found that the energy density was highest and therefore preferable at this current density. In Experimental Example 2, the energy density was high at all current densities, and especially at a current density of 6.32 mA / cm². 2 and current density 12.64 mA / cm² 2 It was found that the energy density was highest and therefore preferable at this current density. Furthermore, in Experimental Example 5, the energy density was high at all current densities, and especially at a current density of 12.64 mA / cm². 2 It was found that the energy density was highest and therefore the most favorable at this point.

[0046] Table 3 summarizes the relationship between the ion resistance and energy density of the positive and negative electrode composite materials for energy storage devices with the same structure as those in Experimental Example 3 or Experimental Example 9, but with different positive and negative electrode composite materials. Current density: 6.32 mA / cm² 2The energy density was higher for the structure in Experimental Example 9 from No. 1 to No. 5, but higher for the structure in Experimental Example 3 in No. 6, and then higher for all subsequent structures. The ionic resistance of the negative electrode composite material in No. 5 was 14.69 Ωm, and the ionic resistance of the negative electrode composite material in No. 6 was 17.79 Ωm. Therefore, it was inferred that if the ionic resistance of the electrode composite material is 15 Ωm or higher, the energy density can be increased by using the structure in Experimental Example 3. Considering that the ionic resistance of the positive electrode composite material in No. 5 was 25.81 Ωm, and the ionic resistance of the positive electrode composite material in No. 6 was 33.71 Ωm, it was inferred that the energy density can be further increased by using the structure in Experimental Example 3 when the ionic resistance of the negative electrode composite material is 15 Ωm or higher and the ionic resistance of the positive electrode composite material is 30 Ωm or higher. Furthermore, in No. 8, where the ion resistance of the positive electrode composite was 57.52 Ωm and the ion resistance of the negative electrode composite was 26.12 Ωm, the energy density of the structure in Experimental Example 3 exceeded that of the structure in Experimental Example 9 at all current densities. Therefore, it was inferred that when the ion resistance of the positive electrode composite is 50 Ωm or higher and the ion resistance of the negative electrode composite is 24 Ωm or higher, the structure in Experimental Example 3 can be used to further increase the energy density even at higher current densities. It was inferred that the same would be true for the other examples besides Experimental Example 3.

[0047] [Table 1]

[0048] [Table 2]

[0049] [Table 3] [Industrial applicability]

[0050] This disclosure is applicable to the field of energy storage devices. [Explanation of Symbols]

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

Claims

1. An electrode storage device comprising an electrode composite material containing an electrode active material, having a plate-shaped base, a plurality of comb teeth provided on the main surface of the base at intervals in a predetermined direction, and comb grooves formed by the sides of adjacent comb teeth and the main surface of the base between those sides, wherein the comb teeth include a first comb tooth which is rectangular in shape and has a length of 100 μm or less in the predetermined direction, and a second comb tooth which is stepped in shape with a tip that is narrower than the root, and has a length of 200 μm or less at the root and the same as or greater than the first comb tooth in the predetermined direction, and 100 μm or less at the tip, and the first comb teeth and the second comb teeth are arranged alternately, and the electrode composite material has an ion resistance of 15 Ωm or more.

2. The electrode is composed of an electrode composite material containing an electrode active material, and comprises a plate-shaped base, a plurality of comb teeth provided on the main surface of the base at intervals in a predetermined direction, and comb grooves formed by the side surfaces of adjacent comb teeth and the main surface of the base between those side surfaces, wherein the comb teeth consist of a first comb tooth which is rectangular in shape and has a length of 100 μm or less in the predetermined direction, and a second comb tooth which is stepped in shape with a tip that is narrower than the root, and has a length of 200 μm or less at the root and the same as or greater than the first comb tooth in the predetermined direction, and 100 μm or less at the tip, and the first comb teeth and the second comb teeth are arranged alternately, and the electrode composite material has an ion resistance of 15 Ωm or more, and the positive electrode is composed of the electrode composite material with an ion resistance of 30 Ωm or more. The electrode is composed of an electrode composite material containing an electrode active material, and comprises a plate-shaped base, a plurality of comb teeth provided on the main surface of the base at intervals in a predetermined direction, and comb grooves formed by the side surfaces of adjacent comb teeth and the main surface of the base between those side surfaces, wherein the comb teeth consist of a first comb tooth which is rectangular in shape and has a length of 100 μm or less in the predetermined direction, and a second comb tooth which is stepped in shape with a tip that is narrower than the root, and has a length of 200 μm or less at the root and the same as or greater than the first comb tooth in the predetermined direction, and 100 μm or less at the tip, and the first comb teeth and the second comb teeth are arranged alternately, and the electrode composite material has an ion resistance of 15 Ωm or more, and the negative electrode is the electrode composite material with an ion resistance of 15 Ωm or more. The system comprises an ion-conducting medium interposed between the comb grooves of the positive electrode and the comb teeth of the negative electrode, which are arranged to fit into the comb grooves, and between the comb grooves of the negative electrode and the comb teeth of the positive electrode, which are arranged to fit into the comb grooves, and which conducts carrier ions. Energy storage device.

3. The first comb teeth have a length of 30 μm or more and 70 μm or less in the predetermined direction. The energy storage device according to claim 1 or 2, wherein the length of the second comb teeth in the predetermined direction is 50 μm or more and 130 μm or less at the root end and 10 μm or more and 50 μm or less at the tip end.

4. The energy storage device according to claim 2, wherein the first comb teeth of the positive electrode are the same shape and dimensions as the first comb teeth of the negative electrode, and the second comb teeth of the positive electrode are 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 of 30 μm or more and 70 μm or less in the predetermined direction. The second comb teeth of the positive electrode and the second comb teeth of the negative electrode have a length of 50 μm or more and 130 μm or less at the root end and 10 μm or more and 50 μm or less at the tip end in the predetermined direction. The energy storage device according to claim 4.

6. Current density 6.32mA / cm 2 The energy density when discharged is 0.8 mWh / cm². 2 The energy storage device according to claim 1 or 2.

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