Electrode and secondary battery

Abstract

The present disclosure is an electrode and a secondary battery. The electrode includes a substrate and an active material layer. The active material layer is disposed on a surface of the substrate. One or more grooves are formed on a 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 portion at a periphery of the active material layer. The outlet region includes an outlet opening portion 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. The inlet region and the outlet region are each configured such 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.

Description

Electrodes and secondary batteries Technical Field

[0001] This disclosure relates to electrodes and secondary batteries. Background Technology

[0002] Japanese Patent Application Publication No. 2021-009846 discloses a technique for improving the impregnation force of electrolyte and the expulsion force of gas by patterning the bonding force on the surface of a separation membrane. Summary of the Invention

[0003] Hereinafter, a secondary battery can be simply referred to as a "battery". A typical battery consists of electrodes and an electrolyte. The electrodes contain an active material layer. This active material layer is porous. The electrolyte permeates into this active material layer.

[0004] If the electrolyte penetration into the active material layer is insufficient, adverse effects such as reduced cycle performance can be expected. Therefore, forming trenches (linear recesses) on the surface of the active material layer can be considered, for example. These trenches can serve as flow paths for the electrolyte. By forming trenches, it is expected that electrolyte penetration will be promoted.

[0005] For example, gas may sometimes be generated due to the decomposition of the electrolyte. Gas generated within the trench may form bubbles. These bubbles may remain trapped in the trench for extended periods. There may be insufficient electrolyte around the bubbles. Localized degradation may occur around the bubbles.

[0006] In this disclosure, the removal of air bubbles is facilitated in the grooved electrode.

[0007] The technical structure and effects of this disclosure are described below. However, the mechanism of action described in this specification is conjectured. The mechanism of action does not limit the technical scope of this disclosure.

[0008] This disclosure relates to an electrode. The electrode comprises a substrate and an active material layer. The active material layer is disposed on the surface of the substrate. The surface of the active material layer has one or more trenches. The trenches extend linearly along the surface of the active material layer. In top view, the trenches comprise 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, connecting the inlet region and the outlet region. The inlet region and the outlet region are each configured such that a first pressure loss when the fluid flows in the forward direction is smaller than a second pressure loss when the fluid flows in the reverse direction. Forward direction refers to the direction from the inlet region to the outlet region. Reverse direction refers to the direction from the outlet region to the inlet region.

[0009] By ensuring that the first pressure loss during forward flow is smaller than the second pressure loss during reverse flow in both the inlet and outlet regions of the trench, each region can function as a check valve. Therefore, it is expected that the fluid (electrolyte) within the trench will readily flow in this forward direction. In other words, the electrolyte flow can be expected to be directional. Because the electrolyte flows in one direction within the trench, bubbles can move in that direction along with the electrolyte flow. Consequently, it is expected that bubbles will easily exit the trench.

[0010] In the above technical solution, at least one of the inlet region and the outlet region can be configured such that 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.

[0011] The inlet and outlet regions can contain any backflow prevention mechanism. Convergence of fluid flow can promote flow. Conversely, divergence of fluid flow can generate vortices, for example. The generation of vortices can increase pressure loss.

[0012] In the above technical solution, at least one of the inlet region and the outlet region may include a portion whose cross-sectional area decreases in the forward direction.

[0013] Hereinafter, the portion whose cross-sectional area decreases in the forward direction is also referred to as the "cross-sectional area changing section". The cross-sectional area changing section can function as a backflow prevention mechanism. The cross-sectional area changing section can function as a constrictor relative to the forward flow. In the constrictor, forward flow can be promoted. The cross-sectional area changing section can also function as an expander relative to the reverse flow. In the expander, reverse flow can be impeded.

[0014] In the above technical solution, at least one of the inlet area and the outlet area may contain a Tesla valve-shaped planar pattern.

[0015] The "Tesla valve" is a flow pattern developed by Nikola Tesla. In a Tesla valve, the flow path shape significantly increases the reverse pressure loss compared to the forward pressure loss. Tesla valves have no moving parts. They are suitable for backflow prevention mechanisms.

[0016] In the above technical solution, in a cross-section orthogonal to the direction of trench extension, the inlet opening has a first cross-sectional area, and the intermediate region has a second cross-sectional area. The first cross-sectional area can be smaller than the second cross-sectional area.

[0017] The active material layer can expand and contract during charging and discharging. The cross-sectional area of ​​the trench can also change according to the volume change of the active material layer. Therefore, the pressure loss of the trench also changes with charging and discharging. According to the novel insights of this disclosure, the change in pressure loss can be greater in the portion with a relatively small cross-sectional area. Hereinafter, the "portion with a relatively small cross-sectional area" is also referred to as the "narrowing portion". By providing a narrowing portion at the inlet opening, it is expected that the inflow of electrolyte from the inlet opening into the trench will be promoted, and the outflow of electrolyte from the inlet opening to the outside of the trench will be hindered. As a result, it is expected that the flow of electrolyte in the trench will be promoted, and the removal of bubbles will be further promoted.

[0018] A secondary battery consists of electrodes and an electrolyte.

[0019] Secondary batteries exhibit good cycle characteristics, believed to be due to the ease with which air bubbles can escape from the grooves.

[0020] The following describes embodiments of this disclosure (hereinafter referred to as "this embodiment"). However, this embodiment does not limit the technical scope of this disclosure. Attached Figure Description

[0021] The features, advantages, and technical and industrial significance of typical embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like reference numerals denote like elements, wherein:

[0022] Figure 1 is a schematic diagram showing the electrodes in this embodiment.

[0023] Figure 2 is a schematic diagram illustrating the flow of fluid.

[0024] Figure 3 is a schematic diagram showing the first backflow prevention mechanism.

[0025] Figure 4 is a schematic diagram showing the second example of the section with a change in cross-sectional area.

[0026] Figure 5 is a schematic diagram showing the third example of the section with a change in cross-sectional area.

[0027] Figure 6 is a schematic diagram showing the second backflow prevention mechanism.

[0028] Figure 7 is a schematic cross-sectional view of the entrance opening and the intermediate area.

[0029] Figure 8 is a schematic diagram showing an example of a planar pattern of a groove.

[0030] Figure 9 is a schematic cross-sectional view of the secondary battery in this embodiment. Detailed Implementation

[0031] In this specification, the expressions "possessing," "comprising," "having," and variations thereof (e.g., "constructed by employing...") are open forms. Open forms may or may not include additional elements besides the essential elements. The expression "constructed by..." is a closed form. However, even in a closed form, impurities or additional elements unrelated to the present disclosure are not excluded. The expression "substantially constituted by..." is a semi-closed form. In a semi-closed form, the addition of elements that do not substantially affect the basic and novel characteristics of the present disclosure is permitted.

[0032] In this instruction manual, expressions such as "can be carried out" and "able to carry out" are not used in an obligatory sense meaning "must be carried out," but rather in an permissive sense meaning "has the possibility of carrying out."

[0033] In this specification, numerical ranges such as "m~n%" include both upper and lower limits unless otherwise specified. That is, "m~n%" represents 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%." Moreover, a new upper or lower limit can be set by arbitrarily selecting a value from the numerical range. For example, a new numerical range can be set by arbitrarily combining values ​​within the numerical range with values ​​described in other parts of this specification, tables, figures, etc.

[0034] In this specification, all numerical values ​​are described using the term "approximately". The term "approximately" can mean, for example, ±5%, ±3%, ±1%, etc. All numerical values ​​can be approximate values ​​that vary depending on how the technology disclosed is used. All numerical values ​​can be expressed in significant figures. The measured value can be the average of multiple measurements. The number of measurements can be 3 or more, 5 or more, or 10 or more. Generally, the more measurements, the higher the reliability of the average value can be expected. The measured value can be rounded based on the number of significant figures. The measured value may include errors, such as those associated with the detection limits of the measuring device.

[0035] The geometric terms used in this specification (such as "parallel," "perpendicular," "orthogonal," etc.) should not be interpreted in a strict sense. For example, "parallel" can also deviate slightly from the strict meaning of "parallel." The geometric terms used in this specification may include tolerances and errors in design, operation, manufacturing, etc. Dimensional relationships in the drawings may not always match actual dimensional relationships. To aid in understanding the technology disclosed herein, dimensional relationships (length, width, thickness, etc.) in the drawings have sometimes been altered. Furthermore, some components may sometimes be omitted.

[0036] In this specification, "top view" means viewing the object from a line of sight parallel to the thickness direction of the object (e.g., active material layer, electrode, etc.). For example, viewing the active material layer 20 from the Z-axis direction of Figures 1 and 6 is equivalent to a top view.

[0037] 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. Compounds may also have non-stoichiometric compositions. For example, when lithium cobalt oxide is expressed as "LiCoO2," unless otherwise specified, lithium cobalt oxide is not limited to a composition ratio of "Li / Co / O = 1 / 1 / 2," and can contain Li, Co, and O in any composition ratio. Furthermore, doping and substitution using trace elements are also permissible.

[0038] In this specification, "D50" is defined as the particle size at which the cumulative frequency, starting from the smallest particle size side, reaches 50% in a volumetric particle size distribution. D50 can be determined using a laser diffraction particle size distribution measuring device.

[0039] In this instruction manual, "electrode" is a general term for both positive and negative electrodes. An electrode can be either positive or negative.

[0040] In this specification, "secondary battery" refers to a battery capable of being charged and discharged. A secondary battery can be any battery system as long as it contains an electrolyte. A secondary battery can be, for example, a lithium-ion battery. This embodiment is an application example to a lithium-ion battery. However, the technology disclosed herein can also be applied to battery systems other than lithium-ion batteries.

[0041] electrode

[0042] Figure 1 is a schematic diagram showing the electrode in this embodiment. Hereinafter, "electrode in this embodiment" may be abbreviated as "this electrode". This electrode 100 is used in a secondary battery. The secondary battery will be described later. This electrode 100 is sheet-shaped. This electrode 100 includes a substrate 10 and an active material layer 20.

[0043] The substrate 10 serves as a support for the active material layer 20. The substrate 10 can be, for example, sheet-like or mesh-like. The substrate 10 can have, for example, a strip-like planar shape. The substrate 10 can be conductive. The substrate 10 can also function as a current collector. A portion of the substrate 10 can be exposed from the active material layer 20. For example, a current collector component can be bonded to the exposed portion of the substrate 10.

[0044] The substrate 10 can have any thickness. For example, the substrate 10 can have a thickness of 5 to 50 μm, or a thickness of 5 to 20 μm.

[0045] The substrate 10 may include, for example, a metal foil. The substrate 10 may contain at least one material selected from, for example, aluminum (Al), copper (Cu), nickel (Ni), titanium (Ti), chromium (Cr), and iron (Fe). The substrate 10 may contain at least one material selected from, for example, 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 contain, for example, an Al foil. When the electrode 100 is a negative electrode, the substrate 10 may contain, for example, a Cu foil.

[0046] An active material layer 20 is disposed on the surface of the substrate 10. The active material layer 20 may be disposed on only one side of the substrate 10, or on both its front and back sides. The active material layer 20 may have any thickness. For example, the active material layer 20 may have a thickness of 5–1000 μm, 10–500 μm, or 50–250 μm.

[0047] 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 can be formed by pressing a punch (convex shape) onto the surface of the active material layer 20. For example, the grooves 25 can be formed using an embossing roller.

[0048] One groove 25 can be formed, or multiple grooves 25 can be formed. The spacing between adjacent grooves 25 (the interval between parallel lines) can be, for example, 0.1 to 10 mm.

[0049] Viewed from above (XY plane of FIG1), the trench 25 includes an inlet region 25a, an intermediate region 25b, and an outlet region 25c. The inlet region 25a includes an inlet opening 21 at the periphery of the active material layer 20. The outlet region 25c includes an outlet opening 22 at the periphery of the active material layer 20. The intermediate region 25b is disposed between the inlet region 25a and the outlet region 25c, connecting the inlet region 25a and the outlet region 25c.

[0050] The length of the intermediate region 25b relative to the total length of the trench 25 can be, for example, 50 to 98%. The length of the inlet region 25a relative to the total length of the trench 25 can be, for example, 1 to 25%. The length of the outlet region 25c relative to the total length of the trench 25 can be, for example, 1 to 25%. The total length of the trench 25 can be, for example, 1 to 5000 mm, or 1 to 1000 mm.

[0051] Figure 2 is a schematic diagram illustrating the fluid flow. The groove 25 has forward FD and reverse BD. Forward FD indicates the direction from the inlet region 25a towards the outlet region 25c. Reverse BD indicates the direction from the outlet region 25c towards the inlet region 25a.

[0052] The first pressure loss ΔP1 represents the pressure loss when the fluid flows in the forward FD direction. When the fluid flows in the forward FD direction, the first pressure loss ΔP1 is generated in the inlet region 25a. Similarly, the first pressure loss ΔP1 is also generated in the outlet region 25c. Furthermore, the pressure loss in the outlet region 25c may be the same as or different from the pressure loss in the inlet region 25a.

[0053] 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 can be generated in the outlet region 25c. Similarly, the second pressure loss ΔP2 can also be generated in the inlet region 25a.

[0054] The inlet region 25a and the outlet region 25c are each configured to satisfy the relationship "ΔP1 < ΔP2". Therefore, it is expected that the electrolyte will flow in one direction (forward FD). With the electrolyte flowing in one direction, it is expected that bubbles will become less likely to be trapped within the trench 25. For example, the relationship "1 < (ΔP2 / ΔP1) ≤ 100", "2 ≤ (ΔP2 / ΔP1)", or "10 ≤ (ΔP2 / ΔP1)" can also be satisfied. Furthermore, the magnitude of the pressure loss can be calculated using, for example, the Darcy-Weisbach formula.

[0055] Both inlet region 25a and outlet region 25c include a backflow prevention mechanism. This backflow prevention mechanism enables the relationship "ΔP1 < ΔP2". Inlet region 25a and outlet region 25c may include any type of backflow prevention mechanism. For example, at least one of inlet region 25a and outlet region 25c may include a first backflow prevention mechanism. For example, at least one of inlet region 25a and outlet region 25c may include a second backflow prevention mechanism. For example, at least one of inlet region 25a and outlet region 25c may include a combination of the first and second backflow prevention mechanisms.

[0056] Figure 3 is a schematic diagram showing the first backflow prevention mechanism. In the first backflow prevention mechanism, a cross-sectional area changing section 27 is provided within the trench. Figure 3 shows a first example of the cross-sectional area changing section 27. The cross-sectional area changing section 27 is connected to the sidewall of the trench. In the cross-sectional area changing section 27, the cross-sectional area decreases in the forward direction FD. The cross-sectional area can change continuously. The cross-sectional area can gradually decrease. One cross-sectional area changing section 27 can be provided, or multiple cross-sectional area changing sections 27 can be provided. Multiple cross-sectional area changing sections 27 can be arranged continuously along the forward direction FD.

[0057] When the fluid flows in the forward FD direction, the cross-sectional area change section 27 functions as a converging tube. That is, the flow can converge in the cross-sectional area change section 27. As a result, forward FD flow can be promoted.

[0058] When the fluid flows in the reverse direction BD, the cross-sectional area change section 27 functions as an expander. That is, the flow can diverge in the cross-sectional area change section 27. The divergent flow can form vortices. Due to the generation of vortices, the pressure loss can increase. In other words, it can impede the reverse flow BD.

[0059] Figure 4 is a schematic diagram showing a second example of a section with a changing cross-sectional area. For example, the section with a changing cross-sectional area can be located away from the sidewall of the trench. That is, a gap can also exist between the section with the changing cross-sectional area and the sidewall of the trench.

[0060] Figure 5 is a schematic diagram showing the third example of a section with a changing cross-sectional area. For example, in the section with a changing cross-sectional area, the cross-sectional area can change in stages (steps).

[0061] When the cross-sectional area changes in stages, the section with the change in cross-sectional area can function as a sudden contraction pipe relative to the forward FD flow. The pressure loss in the sudden contraction pipe is calculated using the following equations (1) to (3).

[0062] ζ=ξ(1 / C c -1) 2 (1)

[0063] h=ζ(u2 2 / 2g) (2)

[0064] ΔP=ρgh (3)

[0065] ζ: Loss coefficient; ξ≈1; C c : Reduction factor; h: Loss head [m];

[0066] u2: Flow velocity [m / s] (refer to Figure 5); g: Gravitational acceleration [m / s²] 2 ];

[0067] ρ: Fluid density [kg / m³] 3 ]; ΔP: pressure loss.

[0068] When the cross-sectional area changes in stages, the flow in the section with the change in cross-sectional area relative to the reverse BD can function as a rapidly expanding tube. The pressure loss in the rapidly expanding tube is calculated using the following equations (4) to (6).

[0069] ζ=ξ(1-A1 / A2) 2 (4)

[0070] h=ζ(u1 2 / 2g) (5)

[0071] ΔP=ρgh (6)

[0072] ζ: loss coefficient; ξ≈1; A1, A2: cross-sectional area (refer to Figure 5); h: head loss [m];

[0073] u1: Flow velocity [m / s] (refer to Figure 5); g: Gravitational acceleration [m / s²] 2 ];

[0074] ρ: Fluid density [kg / m³] 3 ]; ΔP: pressure loss.

[0075] Shrinkage coefficient (C) c The values ​​for (c) and (ζ) are derived from Weisbach's experiments. The shrinkage coefficient (C) c The relationship between the loss coefficient (ζ) and the cross-sectional area ratio (A1 / A2) is shown in Table 1 below.

[0076] Table 1

[0077] A1 / A20.10.20.30.40.50.60.70.80.91.0C c 0.610.620.630.650.670.700.730.770.841.00ζ0.410.380.340.290.240.180.140.0890.0360.0 surface

[0078] Figure 6 is a schematic diagram showing the second backflow prevention mechanism. In the second backflow prevention mechanism, the groove contains a Tesla valve-shaped planar pattern. The Tesla valve contains a teardrop-shaped loop flow channel 29. The Tesla valve may contain one loop flow channel 29 or multiple loop flow channels 29. Multiple loop flow channels 29 may be arranged continuously along the forward FD direction.

[0079] When the fluid flows along the forward direction FD, it is difficult for the fluid to flow into the annular flow path 29. The fluid flows in the main flow path 28. Therefore, it is considered that when the fluid flows along the forward direction FD, the pressure loss is small. On the other hand, when the fluid flows along the reverse direction BD, the fluid can flow into the annular flow path 29. It is considered that the pressure loss increases due to the flow bending.

[0080] For example, a constriction portion may be provided at the inlet opening 21. Compared with other parts, the cross-sectional area of the groove 25 is relatively small in the constriction portion. By including the constriction portion in the inlet opening 21, the inflow of the electrolyte from the inlet opening 21 can be promoted. In addition, by including the constriction portion in the inlet opening 21, the outflow of the electrolyte from the inlet opening 21 can be hindered. Thereby, the discharge of bubbles can be promoted more.

[0081] 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, and the relationship of "0.3 ≤ (S1 / S2) ≤ 0.7" may also be satisfied.

[0082] The inlet opening 21 has a first depth d1. The intermediate region 25b has a second depth d2. The depth represents the maximum depth in the cross-section orthogonal to the axial direction of the groove. Each of the first depth d1 and the second depth d2 can be, for example, 10 to 400 μm, and can be 50 to 200 μm. For example, the relationship of "0.1 ≤ (d1 / d2) ≤ 0.9" may be satisfied, and the relationship of "0.3 ≤ (d1 / d2) ≤ 0.7" may also be satisfied.

[0083] The ratio of the second depth d2 to the thickness of the active material layer 20 can be, for example, 0.1 to 0.9, and can be 0.3 to 0.7.

[0084] The inlet opening 21 has a first width w1. The intermediate region 25b has a second width w2. The width represents the maximum width in the cross-section orthogonal to the axial direction of the groove. Each of the first width w1 and the second width w2 can be, for example, 10 to 500 μm, and can be 50 to 250 μm. For example, the relationship of "0.1 ≤ (w1 / w2) ≤ 0.9" may be satisfied, and the relationship of "0.3 ≤ (w1 / w2) ≤ 0.7" may also be satisfied.

[0085] The length of the constriction portion in the axial direction of the groove can be, for example, 0.1 to 10 mm, and can be 0.1 to 5 mm.

[0086] The groove 25 can have any cross-sectional shape. For example, the cross-sectional shape of the groove 25 can be rectangular, U-shaped, or V-shaped.

[0087] 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 it may have a different cross-sectional shape. The outlet opening 22 may or may not include a contraction. For example, it may also satisfy the relationship "S1 < S2 < S3".

[0088] The trench 25, as long as it includes an inlet region 25a, a middle region 25b, and an outlet region 25c, can have any planar pattern. The trench 25 can, for example, be meandering (see Figure 1). The planar pattern of the trench 25 can, for example, be serpentine. The trench 25 can also, for example, extend in a curved shape.

[0089] Figure 8 is a schematic diagram showing an example of a planar pattern of trenches. The trenches 25 may extend in a straight line, for example. The trenches 25 may extend in a manner that traverses the surface of the active material layer 20, for example. Multiple trenches 25 may also be formed as a group of lines. A group of lines represents a collection of parallel lines. Multiple trenches 25 may also be formed as a grid.

[0090] The active material layer 20 contains an active material. In addition to the active material, the active material layer 20 may also contain, for example, adhesives, conductive materials, etc. The active material layer 20 can be formed, for example, by coating a slurry onto the surface of the substrate 10 in a layered manner. The active material layer 20 can also be formed, for example, by shaping wet powder particles into a sheet shape.

[0091] The active material can be, for example, in particulate form. The active material can have a D50 of, for example, 1–30 μm. The active material can contain, for example, a positive electrode active material. Compared to the negative electrode active material, the positive electrode active material can absorb and release lithium ions at a higher potential. The positive electrode active material can contain any component. The positive electrode active material can contain, for example, at least one selected from LiCoO2, LiNiO2, LiMnO2, LiMn2O4, Li(NiCoMn)O2, Li(NiCoAl)O2, and LiFePO4. For example, in "Li(NiCoMn)O2", "(NiCoMn)" indicates that the total composition ratio within the parentheses is 1. As long as the total is 1, the amount of each component is arbitrary. Li(NiCoMn)O2 can contain, 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 Co0.1 Mn 0.1 O2, etc.

[0092] The active material can include, for example, a negative electrode active material. Compared to the positive electrode active material, the negative electrode active material can absorb and release lithium ions at a lower potential. The negative electrode active material can contain any composition. It can include, for example, materials selected from graphite, soft carbon, hard carbon, silicon, silicon oxide, silicon-based alloys, tin, tin oxide, tin-based alloys, and Li4Ti5O. 12 At least one of them.

[0093] Conductive materials can form electronic conduction pathways. The amount of conductive material relative to 100 parts by mass of active material can be, for example, 0.1 to 10 parts by mass. Conductive materials can contain any components. Conductive materials can contain at least one selected from, for example, carbon black, vapor-grown carbon fibers, carbon nanotubes, and graphene sheets.

[0094] Adhesives are used to bond solid materials together. The amount of adhesive used relative to 100 parts by weight of the active material can be, for example, 0.1 to 10 parts by weight. Adhesives can contain any components. Adhesives can contain at least one selected from, for example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-HFP copolymer, styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyimide (PI), polyamide-imide (PAI), and polyacrylic acid (PAA).

[0095] Figure 9 is a schematic cross-sectional view showing the secondary battery in this embodiment. Hereinafter, "the secondary battery in this embodiment" may be abbreviated as "this battery".

[0096] This battery 200 includes a casing 260. The casing 260 can be sealed. The casing 260 can have any shape. The casing 260 can be, for example, a pouch made of laminated metal foil. The casing 260 can be, for example, a metal container. The casing 260 can be, for example, square or cylindrical. The casing 260 can contain, for example, Al.

[0097] The housing 260 includes an electrode group 250 and an electrolyte (not shown). The electrolyte permeates into the electrode group 250. A portion of the electrolyte may also accumulate at the bottom of the housing 260. The electrode group 250 can have any shape. In Figure 9, a wound electrode group 250 is shown as an example. The electrode group 250 may also be a stacked type, for example. The electrode group 250 includes a positive electrode 210 and a negative electrode 220. The electrode group 250 may also include a separator 230. At least one of the positive electrode 210 and the negative electrode 220 is the aforementioned electrode 100. That is, the battery 200 includes the electrode 100 and the electrolyte.

[0098] The separator 230 can be located between the positive electrode 210 and the negative electrode 220. The separator 230 is electrically insulating. The separator 230 is porous. The separator 230 can be made of, for example, polyolefin.

[0099] The electrolyte is a liquid electrolyte. The electrolyte can be a viscous fluid. The electrolyte may have a viscosity of, for example, 500–2000 kg / cm³. 3 The density. The electrolyte contains lithium salt and solvent. The electrolyte may also contain any additives.

[0100] The lithium salt is dissolved in a solvent. The lithium salt may contain at least one selected from, for example, LiPF6, LiBF4, and Li(FSO2)2N. The concentration of the lithium salt may be, for example, 0.5 to 2 mol / L.

[0101] The solvent may contain any components. The solvent may contain at least one selected from, for example, ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and diethyl carbonate (DEC). The additive may contain at least one selected from, for example, vinylene carbonate (VC), vinylene carbonate (VEC), 1,3-propanesultone (PS), cyclohexylbenzene (CHB), tert-amylbenzene (TAB), and lithium bis(oxalato)borate (LiBOB).

[0102] This embodiment is illustrative in all respects. This embodiment is not restrictive. The scope of this disclosure includes all modifications within the meaning and scope equivalent to the claims. For example, it was intended from the outset that arbitrary components could be extracted from this embodiment and combined arbitrarily.

Claims

1. An electrode, characterized in that, The device comprises a substrate and an active material layer disposed on the surface of the substrate. The active material layer has one or more grooves on its surface, which extend linearly along the surface of the active material layer. In top 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, and 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, connecting the inlet region and the outlet region. The inlet region and the outlet region are each configured such that a first pressure loss when the 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 to the outlet region, and the reverse direction refers to the direction from the outlet region to the inlet region. At least one of the inlet region and the outlet region includes a Tesla valve-shaped planar pattern.

2. The electrode according to claim 1, characterized in that, At least one of the inlet region and the outlet region is configured such that when the fluid flows in the forward direction, the flow of the fluid converges, and when the fluid flows in the reverse direction, the flow of the fluid diverges.

3. The electrode according to claim 1 or 2, characterized in that, At least one of the inlet region and the outlet region includes a portion whose cross-sectional area decreases in the forward direction.

4. The electrode according to claim 1 or 2, characterized in that, In a cross section orthogonal to the direction in which the trench extends, the inlet opening has a first cross-sectional area, the intermediate region has a second cross-sectional area, and the first cross-sectional area is smaller than the second cross-sectional area.

5. A secondary battery comprising: an electrode as described in any one of claims 1 to 4; and an electrolyte.

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