Electrodes and secondary batteries

Abstract

To promote discharge of bubbles from a groove, in an electrode having the groove.SOLUTION: An electrode 100 includes: a base material 10; and an active material layer 20. The active material layer 20 is arranged in a front surface of the base material 10. One or more grooves 25 are formed in the front surface of the active material layer 20. Each of the grooves 25 extends lineally along the front surface of the active material layer 20. In a plan view, each of the grooves 25 includes: an inlet region 25a; an intermediate region 25b; and an outlet region 25c. The inlet region 25a includes an inlet open portion 21 in a peripheral border of the active material layer 20. The outlet region 25c includes an outlet open portion 22 in the peripheral border of the active material layer 20. The intermediate region 25b is arranged between the inlet region 25a and the outlet region 25c. The intermediate region 25b connects the inlet region 25a and the outlet region 25c to each other. Each of the inlet region 25a and the outlet region 25c is constituted in such a way that a first pressure loss at the flow of fluid to a forward direction becomes smaller than a second pressure loss at the flow of the fluid to an inverse direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an electrode and a secondary battery. [Background technology]

[0002] Japanese Patent Publication No. 2021-009846 (Patent Document 1) discloses a technology for increasing the impregnation power of the electrolyte and the gas discharge power by implementing patterned adhesive force on the surface of the separator. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-009846 Summary of the Invention [Problem to be solved by the invention]

[0004] Hereinafter, the secondary battery may be abbreviated as "battery." Generally, a battery includes electrodes and an electrolyte. The electrodes include an active material layer. The active material layer is porous. The electrolyte permeates the active material layer.

[0005] If the electrolyte solution does not penetrate the active material layer sufficiently, problems such as a decrease in cycle characteristics may occur. Therefore, for example, it is conceivable to form grooves (linear recesses) on the surface of the active material layer. The grooves can serve as paths for the electrolyte solution. The formation of the grooves is expected to promote the penetration of the electrolyte solution.

[0006] For example, decomposition of the electrolyte may generate gas. The gas generated in the groove may form bubbles. The bubbles may remain in the groove for a long period of time. The area around the bubbles may become depleted of electrolyte. The area around the bubbles may experience localized deterioration.

[0007] An object of the present disclosure is to facilitate bubble evacuation in electrodes having grooves. [Means for solving the problem]

[0008] The technical configuration and effects of the present disclosure will be described below. However, the mechanism of action in this specification includes speculation. The mechanism of action does not limit the technical scope of the present disclosure.

[0009] 1. The electrode includes a substrate and an active material layer. The active material layer is disposed on the surface of the substrate. One or more grooves are formed on the surface of the active material layer. The grooves extend linearly along the surface of the active material layer. In a plan view, the grooves include an inlet region, an intermediate region, and an outlet region. The inlet region includes an inlet opening at the periphery of the active material layer. The outlet region includes an outlet opening at the periphery of the active material layer. The intermediate region is disposed between the inlet region and the outlet region. The intermediate region connects the inlet region and the outlet region. Each of the inlet region and the outlet region is configured so that a first pressure loss when a fluid flows in a forward direction is smaller than a second pressure loss when the fluid flows in a reverse direction. The forward direction refers to the direction from the inlet region toward the outlet region. The reverse direction refers to the direction from the outlet region toward the inlet region.

[0010] In each of the inlet and outlet regions of the groove, the first pressure loss when the fluid flows in the forward direction is smaller than the second pressure loss when the fluid flows in the reverse direction, allowing each of the inlet and outlet regions to function like a "check valve." This is expected to facilitate the fluid (electrolyte) in the groove to flow in one direction, the forward direction. In other words, it is expected that the flow of the electrolyte will have directionality. As the electrolyte flows in one direction in the groove, gas bubbles can move in one direction along with the flow of the electrolyte. As a result, it is expected that gas bubbles will be more easily discharged from the groove.

[0011] 2. For example, at least one of the inlet region and the outlet region may be configured such that the fluid flow converges when the fluid flows in a forward direction and diverges when the fluid flows in a reverse direction.

[0012] The inlet and outlet regions may include any backflow prevention mechanism. Converging fluid flow may promote flow. Diverging fluid flow may, for example, generate vortices. The generation of vortices may increase pressure loss.

[0013] 3. For example, at least one of the inlet region and the outlet region may include a portion whose cross-sectional area decreases in the forward direction.

[0014] Hereinafter, the portion where the cross-sectional area decreases in the forward direction will also be referred to as a "cross-sectional area change portion." The cross-sectional area change portion can be a backflow prevention mechanism. The cross-sectional area change portion can function as a contraction pipe for the forward flow. In the contraction pipe, the forward flow can be promoted. The cross-sectional area change portion can function as a diverging pipe for the reverse flow. In the diverging pipe, the reverse flow can be inhibited.

[0015] 4. For example, at least one of the entrance and exit regions may include a Tesla bulb-shaped planar pattern.

[0016] The "Tesla valve" is a flow path pattern developed by Nikolaus Tesla. In a Tesla valve, the flow path shape allows the second pressure loss in the reverse direction to be significantly greater than the first pressure loss in the forward direction. The Tesla valve has no moving parts. The Tesla valve is suitable for backflow prevention.

[0017] 5. In a cross section perpendicular to the direction in which the groove extends, the inlet opening has a first cross-sectional area and the intermediate region has a second cross-sectional area, and the first cross-sectional area may be smaller than the second cross-sectional area.

[0018] The active material layer may expand and contract with charge and discharge. The change in volume of the active material layer may also change the cross-sectional area of ​​the groove. Therefore, the pressure loss in the groove changes with charge and discharge. According to the new findings of the present disclosure, the change in pressure loss may be large in portions with relatively small cross-sectional areas. Hereinafter, the "portion with relatively small cross-sectional area" may also be referred to as the "throttled portion." By providing a throttled portion at the inlet opening, it is expected that the inflow of electrolyte from the inlet opening into the groove will be promoted and the discharge of electrolyte from the inlet opening out of the groove will be inhibited. As a result, it is expected that the flow of electrolyte in the groove will be promoted and the discharge of air bubbles will be further promoted.

[0019] 6. A secondary battery includes electrodes and an electrolyte.

[0020] The secondary battery can have good cycle characteristics, presumably because air bubbles are easily discharged from the grooves.

[0021] Hereinafter, an embodiment of the present disclosure (hereinafter may be abbreviated as "the present embodiment") will be described. However, the present embodiment does not limit the technical scope of the present disclosure. [Brief explanation of the drawings]

[0022] [Figure 1] FIG. 1 is a schematic diagram showing an electrode according to this embodiment. [Figure 2] FIG. 2 is a conceptual diagram showing the flow of a fluid. [Figure 3] FIG. 3 is a conceptual diagram showing the first backflow prevention mechanism. [Figure 4] FIG. 4 is a conceptual diagram showing a second example of the cross-sectional area changing portion. [Figure 5] FIG. 5 is a conceptual diagram showing a third example of the cross-sectional area changing portion. [Figure 6] FIG. 6 is a conceptual diagram showing the second backflow prevention mechanism. [Figure 7] FIG. 7 is a schematic cross-sectional view of the inlet opening and intermediate region. [Figure 8] FIG. 8 is a schematic diagram showing an example of a planar pattern of grooves. [Figure 9]FIG. 9 is a schematic cross-sectional view showing a secondary battery according to this embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] <Terminology> In this specification, the terms "comprise," "include," "have," and variations thereof (e.g., "consisting of") are open-ended. Open-ended terms may or may not include additional elements in addition to the required elements. The term "consisting of" is closed-ended. However, even in closed-ended terms, additional elements that are normally incidental impurities or unrelated to the disclosed technology are not excluded. The term "consisting essentially of..." is semi-closed. Semi-closed terms allow for the addition of elements that do not substantially affect the basic and novel characteristics of the disclosed technology.

[0024] In this specification, expressions such as "may" and "can" are used in the permissive sense of "possibly" rather than the obligatory sense of "must."

[0025] In this specification, unless otherwise specified, a numerical range such as "m to n%" includes both the upper and lower limits. That is, "m to n%" indicates a numerical range of "m% or more and n% or less." Furthermore, "m% or more and n% or less" includes "more than m% and less than n%." Furthermore, a numerical value arbitrarily selected from within the numerical range may be set as a new upper or lower limit. For example, a new numerical range may be set by arbitrarily combining a numerical value within the numerical range with a numerical value described elsewhere in this specification, in a table, a figure, or the like.

[0026] In this specification, all numerical values ​​are modified by the term "about." The term "about" may mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​may be approximate values ​​that may vary depending on the application of the disclosed technology. All numerical values ​​may be expressed with significant figures. Measured values ​​may be the average value of multiple measurements. The number of measurements may be three or more, five or more, or ten or more. In general, the more measurements are made, the more reliable the average value is expected to be. Measured values ​​may be rounded off based on the number of significant figures. Measured values ​​may include errors, such as those associated with the detection limits of the measuring device.

[0027] Geometric terms used in this specification (e.g., "parallel," "perpendicular," "orthogonal," etc.) should not be interpreted in a strict sense. For example, "parallel" may deviate slightly from the strict meaning of "parallel." Geometric terms used in this specification may include, for example, tolerances, errors, etc. in design, work, manufacturing, etc. The dimensional relationships in each drawing may not match the actual dimensional relationships. To facilitate understanding of the disclosed technology, the dimensional relationships (length, width, thickness, etc.) in each drawing may be changed. Furthermore, some configurations may be omitted.

[0028] As used herein, the term "planar view" refers to viewing an object (e.g., an active material layer, an electrode, etc.) from a line of sight parallel to the thickness direction of the object. For example, viewing the active material layer 20 from the Z-axis direction in Figures 1 and 6 can correspond to a planar view.

[0029] In this specification, when a compound is expressed by a stoichiometric formula (e.g., "LiCoO2"), the stoichiometric formula is merely a representative example of the compound. The compound may have a non-stoichiometric composition. For example, when lithium cobalt oxide is expressed as "LiCoO2," unless otherwise specified, the lithium cobalt oxide is not limited to a composition ratio of "Li / Co / O = 1 / 1 / 2" and may contain Li, Co, and O in any composition ratio. Furthermore, doping or substitution with trace elements may be permitted.

[0030] As used herein, "D50" is defined as the particle size at which the cumulative frequency of smaller particle sizes reaches 50% in a volume-based particle size distribution. D50 can be measured using a laser diffraction particle size distribution analyzer.

[0031] In this specification, the term "electrode" is a general term for a positive electrode and a negative electrode. The electrode may be a positive electrode or a negative electrode.

[0032] In this specification, the term "secondary battery" refers to a battery that can be charged and discharged. The secondary battery may be any battery system as long as it contains an electrolyte. The secondary battery may be, for example, a lithium ion battery. This embodiment is an example of application to a lithium ion battery. However, the technology of the present disclosure may also be applied to battery systems other than lithium ion batteries.

[0033] <Electrode> FIG. 1 is a schematic diagram showing an electrode in this embodiment. Hereinafter, "the electrode in this embodiment" may be abbreviated as "the electrode." The electrode 100 is for a secondary battery. The secondary battery will be described later. The electrode 100 is in a sheet form. The electrode 100 includes a substrate 10 and an active material layer 20.

[0034] 《Base material》 The substrate 10 is a support for the active material layer 20. The substrate 10 may be, for example, in the form of a sheet or a mesh. The substrate 10 may have, for example, a strip-like planar shape. The substrate 10 may be conductive. The substrate 10 may function as a current collector. A portion of the substrate 10 may be exposed from the active material layer 20. For example, a current collecting member or the like may be joined to the exposed portion of the substrate 10.

[0035] The substrate 10 may have any thickness. For example, the substrate 10 may have a thickness of 5 to 50 μm, or may have a thickness of 5 to 20 μm.

[0036] The substrate 10 may include, for example, a metal foil. The substrate 10 may include, for example, at least one selected from the group consisting of aluminum (Al), copper (Cu), nickel (Ni), titanium (Ti), chromium (Cr), and iron (Fe). The substrate 10 may include, for example, at least one selected from the group consisting of Al foil, Al alloy foil, Cu foil, Cu alloy foil, Ni foil, Ni alloy foil, Ti foil, and stainless steel foil. When the electrode 100 is a positive electrode, the substrate 10 may include, for example, Al foil. When the electrode 100 is a negative electrode, the substrate 10 may include, for example, Cu foil.

[0037] 《Active material layer》 The active material layer 20 is disposed on the surface of the substrate 10. The active material layer 20 may be disposed on only one surface of the substrate 10, or on both the front and back surfaces. The active material layer 20 may have any thickness. For example, the active material layer 20 may have a thickness of 5 to 1000 μm, 10 to 500 μm, or 50 to 250 μm.

[0038] <groove> One or more grooves 25 (recesses) are formed on the surface of the active material layer 20. The grooves 25 extend linearly along the surface of the active material layer 20. The grooves 25 can be formed by any method. For example, the grooves 25 may be formed by pressing a convex mold against the surface of the active material layer 20. For example, the grooves 25 may be formed by an embossing roll.

[0039] There may be one groove 25 formed, or there may be a plurality of grooves 25. The pitch between adjacent grooves 25 (the distance between parallel lines) may be, for example, 0.1 to 10 mm.

[0040] In a plan view (XY plane in FIG. 1 ), groove 25 includes an entrance region 25a, an intermediate region 25b, and an exit region 25c. Entrance region 25a includes an entrance opening 21 at the periphery of active material layer 20. Exit region 25c includes an exit opening 22 at the periphery of active material layer 20. Intermediate region 25b is disposed between entrance region 25a and exit region 25c. Intermediate region 25b connects entrance region 25a and exit region 25c.

[0041] The length of the intermediate region 25b may be, for example, 50 to 98% of the total length of the groove 25. The length of the inlet region 25a may be, for example, 1 to 25% of the total length of the groove 25. The length of the outlet region 25c may be, for example, 1 to 25% of the total length of the groove 25. The total length of the groove 25 may be, for example, 1 to 5000 mm, or 1 to 1000 mm.

[0042] 2 is a conceptual diagram showing the flow of a fluid. The groove 25 has a forward direction FD and a reverse direction BD. The forward direction FD indicates the direction from the inlet region 25a to the outlet region 25c. The reverse direction BD indicates the direction from the outlet region 25c to the inlet region 25a.

[0043] The first pressure loss ΔP1 indicates the pressure loss when the fluid flows in the forward direction FD. When the fluid flows in the forward direction FD, the first pressure loss ΔP1 may occur in the inlet region 25a. Similarly, the first pressure loss ΔP1 may also occur in the outlet region 25c. Note that the pressure loss in the outlet region 25c may be the same as or different from the pressure loss in the inlet region 25a.

[0044] The second pressure loss ΔP2 represents the pressure loss when the fluid flows in the reverse direction BD. When the fluid flows in the reverse direction BD, the second pressure loss ΔP2 may occur in the outlet region 25c. Similarly, the second pressure loss ΔP2 may also occur in the inlet region 25a.

[0045] The inlet region 25a and the outlet region 25c are each configured to satisfy the relationship "ΔP1<ΔP2." This is expected to cause the electrolyte to flow in one direction (forward direction FD). By causing the electrolyte to flow in one direction, it is expected that bubbles will be less likely to remain in the groove 25. For example, the relationship "1<(ΔP2 / ΔP1)≦100" may be satisfied, or the relationship "2≦(ΔP2 / ΔP1)" may be satisfied, or the relationship "10≦(ΔP2 / ΔP1)" may be satisfied. The magnitude of the pressure loss can be calculated, for example, using the Darcy-Weisbach equation.

[0046] <Backflow prevention mechanism> Each of the inlet region 25a and the outlet region 25c includes a backflow prevention mechanism. The backflow prevention mechanism can realize the relationship "ΔP1<ΔP2." The inlet region 25a and the outlet region 25c can include any backflow prevention mechanism. For example, at least one of the inlet region 25a and the outlet region 25c can include a first backflow prevention mechanism. For example, at least one of the inlet region 25a and the outlet region 25c can include a second backflow prevention mechanism. For example, at least one of the inlet region 25a and the outlet region 25c can include a combination of the first backflow prevention mechanism and the second backflow prevention mechanism.

[0047] FIG. 3 is a conceptual diagram showing a first backflow prevention mechanism. In the first backflow prevention mechanism, a cross-sectional area change portion 27 is provided in the groove. FIG. 3 shows a first example of the cross-sectional area change portion 27. The cross-sectional area change portion 27 is connected to the side wall of the groove. In the cross-sectional area change portion 27, the cross-sectional area decreases toward the forward direction FD. The cross-sectional area may change continuously. The cross-sectional area may decrease gradually. One cross-sectional area change portion 27 may be provided, or multiple cross-sectional area change portions 27 may be provided. The multiple cross-sectional area change portions 27 may be continuously arranged in the forward direction FD.

[0048] When the fluid flows in the forward direction FD, the cross-sectional area change section 27 can function as a contraction pipe. That is, the flow can be focused at the cross-sectional area change section 27. This can promote the flow in the forward direction FD.

[0049] When a fluid flows in the reverse direction BD, the cross-sectional area change section 27 may function as a diverging pipe. That is, the flow may diverge in the cross-sectional area change section 27. The diverged flow may form a vortex. The generation of the vortex may increase the pressure loss. That is, the flow in the reverse direction BD may be obstructed.

[0050] 4 is a conceptual diagram showing a second example of the cross-sectional area changing portion. The cross-sectional area changing portion may be separated from the side wall of the groove, for example. That is, there may be a gap between the cross-sectional area changing portion and the side wall of the groove.

[0051] 5 is a conceptual diagram showing a third example of the cross-sectional area changing portion. For example, in the cross-sectional area changing portion, the cross-sectional area may change in a step-like manner.

[0052] When the cross-sectional area changes stepwise, the cross-sectional area change section can function as a sudden contraction pipe for the flow in the forward direction FD. The pressure loss in a sudden contraction pipe is calculated by the following equations (1) to (3).

[0053] ζ=ξ(1 / C c -1) 2 (1) h=ζ(u2 2 / 2g) (2) ΔP=ρgh (3) ζ: Loss coefficient, ξ≒1, C c : Reduction coefficient, h: Loss head [m] u2: flow velocity [m / s] (see Figure 5), g: gravitational acceleration [m / s 2 ] ρ: Fluid density [kg / m 3 ], ΔP: pressure loss

[0054] When the cross-sectional area changes stepwise, the cross-sectional area change section can function as a sudden expansion pipe for the flow in the reverse direction BD. The pressure loss in the sudden expansion pipe is calculated by the following equations (4) to (6).

[0055] ζ=ξ(1-A1 / A2) 2 (4) h=ζ(u1 2 / 2g) (5) ΔP=ρgh (6) ζ: loss coefficient, ξ≒1, A1, A2: cross-sectional area (see Figure 5), h: loss head [m] u1: flow velocity [m / s] (see Figure 5), g: gravitational acceleration [m / s 2 ] ρ: Fluid density [kg / m 3 ], ΔP: pressure loss

[0056] Contraction coefficient (C c ) and loss coefficient (ζ) are values ​​obtained from the Weisbach experiment. c The relationship between the cross-sectional area ratio (A1 / A2) and the loss factor (ζ) is shown in Table 1 below.

[0057] [Table 1]

[0058] FIG. 6 is a conceptual diagram showing a second backflow prevention mechanism. In the second backflow prevention mechanism, the groove includes a planar pattern in the shape of a Tesla valve. The Tesla valve includes a teardrop-shaped loop flow channel 29. The Tesla valve may include one loop flow channel 29 or multiple loop flow channels 29. The multiple loop flow channels 29 may be arranged consecutively in the forward direction FD.

[0059] When the fluid flows in the forward direction FD, it is difficult for the fluid to flow into the loop flow path 29. The fluid flows through the main flow path 28. Therefore, when the fluid flows in the forward direction FD, it is thought that the pressure loss is small. On the other hand, when the fluid flows in the reverse direction BD, the fluid can flow into the loop flow path 29. It is thought that the pressure loss increases due to the bending of the flow.

[0060] <Diaphragm section> For example, a throttle portion may be provided at the inlet opening 21. The throttle portion has a relatively smaller cross-sectional area of the groove 25 compared to other portions. By including the throttle portion in the inlet opening 21, the inflow of the electrolytic solution from the inlet opening 21 can be promoted. Also, by including the throttle portion in the inlet opening 21, the outflow of the electrolytic solution from the inlet opening 21 can be inhibited. Thereby, the discharge of bubbles can be further promoted.

[0061] FIG. 7 is a schematic cross-sectional view of the inlet opening and the intermediate region. The cross-section of FIG. 7 is orthogonal to the direction in which the groove 25 extends (the axial direction of the groove). The inlet opening 21 has, for example, a first cross-sectional area S1. The intermediate region 25b has a second cross-sectional area S2. For example, the relationship of "S1 < S2" may be satisfied. For example, the relationship of "0.1 ≦ (S1 / S2) ≦ 0.9" may be satisfied, or the relationship of "0.3 ≦ (S1 / S2) ≦ 0.7" may be satisfied.

[0062] The inlet opening 21 has a first depth d1. The intermediate region 25b has a second depth d2. The depth indicates the maximum depth in a cross-section orthogonal to the axial direction of the groove. Each of the first depth d1 and the second depth d2 may be, for example, 10 to 400 μm, or may be 50 to 200 μm. For example, the relationship of "0.1 ≦ (d1 / d2) ≦ 0.9" may be satisfied, or the relationship of "0.3 ≦ (d1 / d2) ≦ 0.7" may be satisfied.

[0063] The ratio of the second depth d2 to the thickness of the active material layer 20 may be, for example, 0.1 to 0.9, or may be 0.3 to 0.7.

[0064] The inlet opening 21 has a first width w1. The intermediate region 25b has a second width w2. The width indicates the maximum width in a cross-section orthogonal to the axial direction of the groove. Each of the first width w1 and the second width w2 may be, for example, 10 to 500 μm, or may be 50 to 250 μm. For example, the relationship of "0.1 ≦ (w1 / w2) ≦ 0.9" may be satisfied, or the relationship of "0.3 ≦ (w1 / w2) ≦ 0.7" may be satisfied.

[0065] The length of the throttle portion in the axial direction of the groove may be, for example, 0.1 to 10 mm, or may be 0.1 to 5 mm.

[0066] The groove 25 can have an arbitrary cross-sectional shape. The cross-sectional shape of the groove 25 may be, for example, rectangular, U-shaped, or V-shaped.

[0067] The outlet opening 22 has a third cross-sectional area S3. The outlet opening 22 may have the same cross-sectional shape as the inlet opening 21, or may have a different cross-sectional shape. The outlet opening 22 may or may not include a throttle portion. For example, the relationship of "S1 < S2 < S3" may be satisfied.

[0068] 〈Planar pattern〉 As long as the groove 25 includes an inlet region 25a, an intermediate region 25b, and an outlet region 25c, it can have an arbitrary planar pattern. The groove 25 may, for example, meander (see FIG. 1). The planar pattern of the groove 25 may be, for example, serpentine. The groove 25 may, for example, extend in a curved shape.

[0069] FIG. 8 is a schematic view showing an example of the planar pattern of the groove. The groove 25 may, for example, extend linearly. The groove 25 may, for example, extend so as to cross the surface of the active material layer 20. A plurality of grooves 25 may be formed in a myriad line shape. A myriad line indicates a set of parallel lines. A plurality of grooves 25 may be formed in a lattice shape.

[0070] 〈Composition〉 The active material layer 20 contains an active material. In addition to the active material, the active material layer 20 may further contain, for example, a binder, a conductive material, etc. The active material layer 20 may be formed, for example, by laminating a slurry on the surface of the base material 10. The active material layer 20 may be formed, for example, by molding wet powder particles into a sheet shape.

[0071] The active material may be, for example, particulate. The active material may have a D50 of, for example, 1 to 30 μm. The active material may include, for example, a positive electrode active material. The positive electrode active material can absorb and release lithium ions at a higher potential than the negative electrode active material. The positive electrode active material may include any component. The positive electrode active material may include, for example, at least one selected from the group consisting of LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. For example, "(NiCoMn)" in "Li(NiCoMn)O2" indicates that the sum of the composition ratios in parentheses is 1. As long as the sum is 1, the amounts of the individual components are arbitrary. Li(NiCoMn)O2 may be, for example, Li(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 )O2, Li(Ni 0.5 Co 0.2 Mn 0.3 )O2, Li(Ni 0.8 Co 0.1 Mn 0.1 ) O2, etc.

[0072] The active material may include, for example, a negative electrode active material. The negative electrode active material can absorb and release lithium ions at a lower potential than the positive electrode active material. The negative electrode active material may include any component. Examples of the negative electrode active material include graphite, soft carbon, hard carbon, silicon, silicon oxide, silicon-based alloys, tin, tin oxide, tin-based alloys, and Li4Ti5O. 12 It may contain at least one selected from the group consisting of:

[0073] The conductive material can form an electron conduction path. The amount of the conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the active material. The conductive material may contain any component. For example, the conductive material may contain at least one material selected from the group consisting of carbon black, vapor-grown carbon fiber, carbon nanotubes, and graphene flakes.

[0074] The binder can bind solid materials together. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of active material. The binder may contain any component. For example, the binder may contain at least one selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyimide (PI), polyamideimide (PAI), and polyacrylic acid (PAA).

[0075] <Secondary battery> 9 is a schematic cross-sectional view showing the secondary battery of this embodiment. Hereinafter, the "secondary battery of this embodiment" may be abbreviated as "the battery."

[0076] The battery 200 includes a case 260. The case 260 may be sealed. The case 260 may have any shape. For example, the case 260 may be a pouch made of a metal foil laminate film. The case 260 may be a metal container. The case 260 may be, for example, rectangular or cylindrical. The case 260 may contain, for example, Al.

[0077] The case 260 contains an electrode group 250 and an electrolyte (not shown). The electrolyte permeates the electrode group 250. A portion of the electrolyte may be stored in the bottom of the case 260. The electrode group 250 may have any shape. FIG. 9 shows a wound electrode group 250 as an example. The electrode group 250 may be, for example, a laminated type. The electrode group 250 includes a positive electrode 210 and a negative electrode 220. The electrode group 250 may further include a separator 230. At least one of the positive electrode 210 and the negative electrode 220 is the above-mentioned present electrode 100. That is, the present battery 200 includes the present electrode 100 and an electrolyte.

[0078] The separator 230 may be interposed between the positive electrode 210 and the negative electrode 220. The separator 230 is electrically insulating. The separator 230 is porous. The separator 230 may be made of, for example, polyolefin.

[0079] 《Electrolyte》 The electrolyte is a liquid electrolyte. The electrolyte may be a viscous fluid. The electrolyte may have a viscosity of, for example, 500 to 2000 kg / cm. 3 The electrolyte may have a density of 1000 .mu.m. The electrolyte includes a lithium salt and a solvent. The electrolyte may further include an optional additive.

[0080] The lithium salt is dissolved in the solvent. The lithium salt may include at least one selected from the group consisting of LiPF6, LiBF4, and Li(FSO2)2N. The concentration of the lithium salt may be, for example, 0.5 to 2 mol / L.

[0081] The solvent may contain any component. For example, the solvent may contain at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). The additive may contain at least one selected from the group consisting of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), 1,3-propane sultone (PS), cyclohexylbenzene (CHB), tert-amylbenzene (TAB), and lithium bis(oxalato)borate (LiBOB).

[0082] The present embodiment is illustrative in all respects. The present embodiment is not restrictive. The technical scope of the present disclosure encompasses all modifications within the meaning and scope equivalent to the description of the claims. For example, it is also intended from the beginning that any configuration may be extracted from the present embodiment and arbitrarily combined. [Explanation of symbols]

[0083] 10 substrate, 20 active material layer, 21 inlet opening, 22 outlet opening, 25 groove, 25a inlet region, 25b intermediate region, 25c outlet region, 27 cross-sectional area change section, 28 main flow path, 29 loop flow path, 100 electrode, 200 secondary battery, 210 positive electrode, 220 negative electrode, 230 separator, 250 electrode group, 260 case, BD reverse direction, FD forward direction, S1 first cross-sectional area, S2 second cross-sectional area, d1 first depth, d2 second depth, w1 first width, w2 second width.

Claims

1. Substrate and Active material layer and Including, the active material layer is disposed on a surface of the substrate, one or more grooves are formed on the surface of the active material layer, the grooves extend linearly along the surface of the active material layer, In plan view, the groove includes an inlet region, an intermediate region, and an outlet region; the inlet region includes an inlet opening at a periphery of the active material layer; the outlet region includes an outlet opening at the periphery of the active material layer; the intermediate region is disposed between the inlet region and the outlet region; the intermediate region connects the inlet region and the outlet region; each of the inlet region and the outlet region configured such that a first pressure loss when fluid flows in a forward direction is less than a second pressure loss when fluid flows in a reverse direction; the forward direction indicates a direction from the entrance region toward the exit region; the reverse direction indicates a direction from the outlet region toward the inlet region; At least one of the inlet region and the outlet region includes a Tesla valve-shaped planar pattern. electrode.

2. At least one of the inlet region and the outlet region is When the fluid flows in the forward direction, the fluid flow converges; and When the fluid flows in the reverse direction, the fluid flow diverges. It is configured as follows:

10. The electrode of claim 1.

3. At least one of the inlet region and the outlet region includes a portion whose cross-sectional area decreases in the forward direction.

3. The electrode according to claim 1 or claim 2.

4. In a cross section perpendicular to the direction in which the groove extends, the inlet opening has a first cross-sectional area; the intermediate region has a second cross-sectional area; The first cross-sectional area is smaller than the second cross-sectional area.

4. The electrode according to claim 1.

5. The electrode according to any one of claims 1 to 4; Electrolyte and Including, Secondary battery.

Images