Electrode and electrode assembly for rechargeable battery

Abstract

The invention relates to an electrode and an electrode assembly for a rechargeable battery. The electrode for a rechargeable battery includes: a substrate having an electrode uncoated region; an active material layer on the substrate forming an electrode active region, the active material layer having an end portion having an inclined surface with respect to the substrate; and an auxiliary layer formed on the inclined surface of the active material layer, wherein the auxiliary layer includes an active material and a resin.

Description

Technical Field

[0001] The present disclosure relates to electrodes and electrode assemblies for rechargeable batteries. Background Art

[0002] Unlike primary batteries, rechargeable batteries are batteries that can be repeatedly charged and discharged. Small-capacity rechargeable batteries can be used in portable small electronic devices, such as mobile phones, laptop computers, and video cameras. Large-capacity and high-density rechargeable batteries can be used as power sources for driving motors of hybrid vehicles and electric vehicles or as energy storage power sources.

[0003] A rechargeable battery can be manufactured by sealing an electrode assembly (the electrode assembly has a structure in which a positive electrode, a separator, and a negative electrode are stacked) together with an electrolyte in a case.

[0004] The positive electrode and the negative electrode can be manufactured into a core-shaped electrode assembly by continuously applying an active material on a long strip-shaped substrate to form an active material layer and then winding the active material layer. Alternatively, the positive electrode and the negative electrode can be manufactured into a stacked electrode assembly by stacking sheet electrodes cut to a predetermined length.

[0005] Active material layers are formed on both surfaces of the substrate to increase the capacity of the rechargeable battery. However, there may be a large thickness difference at its edge. Depending on the amount of the active material, the thickness difference causes a capacity difference. When the capacity ratio (N / P) of the positive electrode to the negative electrode is less than 1, the capacity of the negative electrode is insufficient, resulting in an unstable face-to-face state. This may cause deterioration of the performance of the rechargeable battery (such as lithium precipitation during charging) and safety problems. Summary of the Invention

[0006] Embodiments provide an electrode for a rechargeable battery, in which the thickness difference between the active material layers on both surfaces of the substrate is very small or there is no difference, the thickness and the applied amount of the active material layer are uniform, so there is no capacity ratio difference, thereby reducing lithium precipitation.

[0007] Embodiments of the present disclosure provide an electrode for a rechargeable battery, the electrode for a rechargeable battery including: a substrate having an electrode uncoated area; an active material layer formed on the substrate to form an electrode active area, the active material layer having an end portion with an inclined surface with respect to the substrate; and an auxiliary layer formed on the inclined surface of the active material layer, wherein the auxiliary layer includes an active material and a resin.

[0008] The active material and the resin included in the auxiliary layer can be mixed in a weight ratio of 99.9:0.1 to 90:10.

[0009] The auxiliary layer may include a lower layer made of an active material and a resin, and an upper layer made of a resin and located on the lower layer. The active material and the resin of the lower layer may be mixed in a weight ratio of 99.9:0.1 to 90:10.

[0010] The thickness of the upper layer may be 0.5 μm to 20 μm.

[0011] The thickness of the auxiliary layer may be 10% or less of the maximum thickness of the active material layer.

[0012] The resin may include one of a thermosetting resin, a UV-curable resin, and a thermoplastic resin.

[0013] The thermosetting resin may include at least one of an epoxy resin, a phenolic resin, a melamine resin, a urea-formaldehyde resin, an unsaturated polyester resin, an alkyd resin, a silicone resin, a polyurethane resin, and a polyimide resin.

[0014] The thermoplastic resin may include at least one of polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, vinyl chloride, vinylidene chloride, fluororesin, acrylic resin, polyvinyl acetate resin, polyamide resin, polycarbonate resin, acetal resin, polyphenylene ether, polyester, and polysulfone.

[0015] The UV-curable resin may include at least one of polyurethane acrylate, unsaturated polyester, epoxy acrylate, oxetane, vinyl ether resin, polyester acrylate, silicon acrylate, alicyclic epoxy resin, and glycidyl ether epoxy resin.

[0016] The UV-curable resin may further include a photoinitiator, and based on the total mass of the resin included in the auxiliary layer, the content of the photoinitiator may be 0.01% by mass to 10% by mass.

[0017] The active material may be a negative electrode active material including a carbon-based negative electrode active material.

[0018] According to another embodiment, the electrode assembly includes a negative electrode, which includes: a substrate having an electrode uncoated region; an active material layer formed on the substrate to form an electrode active region, the active material layer having an end portion with an inclined surface with respect to the substrate; and an auxiliary layer formed on the inclined surface of the active material layer, wherein the auxiliary layer includes an active material and a resin. The electrode assembly further includes: a positive electrode overlapping the negative electrode and a separator disposed between the negative electrode and the positive electrode. A part of the end portion of the positive electrode corresponds to the inclined surface of the negative electrode where the auxiliary layer is formed.

[0019] As in the embodiments of the present disclosure, when the auxiliary layer is formed at the edge of the active material layer, the thickness difference between the edge and the middle portion of the electrode active region can be reduced.

[0020] Accordingly, the capacity difference caused by the thickness difference or the application amount difference is reduced, thereby reducing lithium precipitation. Accordingly, a safe rechargeable battery can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 FIG. is a schematic cross-sectional view of an electrode for a rechargeable battery according to an embodiment of the present disclosure.

[0022] Figure 2 FIG. is a schematic cross-sectional view of an electrode for a rechargeable battery according to another embodiment of the present disclosure.

[0023] Figure 3 FIG. is a schematic exploded perspective view of an electrode assembly according to an embodiment of the present disclosure.

[0024] Figure 4 is Figure 3 a top view of the positive electrode and the negative electrode of the electrode assembly of.

[0025] Figure 5 FIG. is a cross-sectional view taken along line Figure 4 V-V' of.

[0026] Figure 6 FIG. is a cross-sectional view taken along line Figure 4 VI-VI' of.

[0027] Figure 7 illustrates the effect of the auxiliary layer according to an embodiment of the present disclosure.

[0028] Figure 8 FIG. is a schematic perspective view of a rechargeable battery according to another embodiment of the present disclosure.

[0029] Figure 9 FIG. is a cross-sectional view taken along line Figure 8 IX-IX' of. DETAILED DESCRIPTION

[0030] The present disclosure will be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown. As will be recognized by those skilled in the art, the described embodiments can be modified in various different ways without departing from the scope of the present disclosure. The drawings and the description are to be regarded as illustrative rather than restrictive. Throughout the specification, the same reference numerals represent the same elements.

[0031] Figure 1 FIG. is a schematic cross-sectional view of an electrode for a rechargeable battery according to an embodiment of the present disclosure.

[0032] As Figure 1As shown, the electrode for a rechargeable battery according to an embodiment of the present disclosure includes a substrate 70 and an active material layer 71 formed on the substrate 70.

[0033] The electrode may be a negative electrode, and the active material layer 71 may include a negative electrode active material. The negative electrode active material may be a carbon-based negative electrode active material. The carbon-based negative electrode active material may be artificial graphite or a mixture of artificial graphite and natural graphite. When a crystalline carbon-based negative electrode active material (such as artificial graphite or a mixture of artificial graphite and natural graphite) is used as the negative electrode active material, the crystallographic characteristics of the particles are more developed than when an amorphous carbon-based negative electrode active material is used. Therefore, the orientation characteristics of the carbon material in the electrode plate with respect to an external magnetic field can be further improved. The form of artificial graphite or natural graphite may be amorphous, plate-like, flaky, spherical, fibrous, or a combination thereof. In addition, when a mixture of artificial graphite and natural graphite is used, the mixing ratio of artificial graphite and natural graphite may be 70:30 to 95:5 by weight.

[0034] In addition, the negative electrode active material may further include at least one of a Si-based negative electrode active material, a Sn-based negative electrode active material, and a LiMO x (M = metal)-based negative electrode active material. When the negative electrode active material further includes these, that is, when a carbon-based negative electrode active material is included as the first negative electrode active material and a negative electrode active material other than the carbon-based negative electrode active material is included as the second negative electrode active material, the mixing ratio of the first negative electrode active material and the second negative electrode active material may be 50:50 to 99:1 by weight.

[0035] LiMO x (M = metal)-based negative electrode active material may be lithium vanadium oxide.

[0036] The Si-based negative electrode active material may include Si, Si-C composite, SiO x (0 < x ≤ 2) or Si-Q alloy (where Q is an element selected from the group consisting of: alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Si), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof). Examples of the Sn-based negative electrode active material may include Sn, SnO x(0 < x ≤ 2) (e.g., SnO2), Sn-R alloy (where R is an element selected from the group consisting of: alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements (excluding Sn), Group 15 elements, Group 16 elements, transition metals, rare earth elements, and combinations thereof). Additionally, a mixture of at least one of them and SiO2 can be used. Elements Q and R can be selected and used from the group consisting of Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn (R does not include Sn), In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0037] With respect to the total weight of the negative electrode active material layer, the content of the negative electrode active material in the negative electrode active material layer can be 95 wt% to 99 wt%.

[0038] The negative electrode active material layer can further include a binder and optionally further include a conductive material. With respect to the total weight of the negative electrode active material layer, the content of the binder in the negative electrode active material layer can be 1 wt% to 5 wt%. Additionally, when further including a conductive material, with respect to the total weight of the negative electrode active material layer, the amount of the negative electrode active material can be 90 wt% to 98 wt%, the amount of the binder can be 1 wt% to 5 wt%, and the amount of the conductive material can be 1 wt% to 5 wt%.

[0039] The binder is used to bond the negative electrode active material particles well to each other and also bond the negative electrode active material well to the substrate serving as the negative electrode current collector. As the binder, a non-aqueous binder, an aqueous binder, or a combination thereof can be used.

[0040] The non-aqueous binder can include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or combinations thereof.

[0041] The aqueous binder can include styrene-butadiene rubber (SBR), acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, ethylene-propylene copolymer, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene-propylene-diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, acrylate resin, or combinations thereof.

[0042] When an aqueous binder is used as a binder in the negative electrode active material layer, a cellulose compound capable of imparting viscosity may be further included as a thickener. As the cellulose compound, at least one of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and its alkali metal salts may be used in admixture. As the alkali metal, Na, K, or Li may be used. The amount of the thickener used may be 0.1 parts by weight to 3 parts by weight with respect to 100 parts by weight of the negative electrode active material.

[0043] The conductive material is used to impart conductivity to the electrode and may be any electronically conductive material as long as the electronically conductive material does not cause a chemical change in the constructed battery. Examples of the conductive material may include: carbon materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, and carbon fiber; metal materials including metal fibers or metal powders of copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0044] The Brunauer - Emmett - Teller (BET) specific surface area of the negative electrode active material layer may be less than 3.0 m 2 / g and may also be 0.6 m 2 / g to 1.2 m 2 / g. If the BET specific surface area of the negative electrode active material layer is less than 3.0 m 2 / g, the electrochemical life characteristics of the battery cell may be improved.

[0045] The BET specific surface area measurement is carried out as follows: A rechargeable battery including the negative electrode is charged and discharged, and then the negative electrode obtained by disassembling the battery in a fully discharged state is cut into a certain size, placed in a BET sample holder, and measured using the nitrogen adsorption method.

[0046] The negative electrode may have a cross - sectional load level (L / L) of 6 mg / cm 2 to 65 mg / cm 2 . The edge of the active material layer 71 may have an inclined surface S with respect to the substrate 70, and the auxiliary layer 77 is formed on the inclined surface S. The width D1 (see Figure 5 ) of the edge of the active material layer 71 may extend 15 mm from the end E of the active material layer in the direction toward the central portion C.

[0047] The auxiliary layer 77 may be formed on all or a part of the edge of the active material layer 71 to compensate for the thickness difference caused by the inclination of the active material layer 71. Accordingly, the width D1 (see Figure 5 ) of the edge of the active material layer 71 may be equal to or greater than the width D2 (see Figure 3 ) of the auxiliary layer 77.

[0048] The auxiliary layer 77 compensates for the thickness reduction of the active material layer 71 due to the inclination of the active material layer 71. For this reason, the thickness of the auxiliary layer 77 gradually decreases from the end E at the edge toward the central portion C, thereby compensating for the inclination of the active material layer 71. Accordingly, the thickness of the active material layer 71 and the auxiliary layer 77 combined at the edge can be substantially the same as the thickness of the active material layer 71 at the central portion C of the active material layer 71. That is, the thickness of the active material layer 71 and the combination of the active material layer 71 and the auxiliary layer 77 is constant, such that the thickness at the edge and the thickness at the central portion C can be substantially the same. Accordingly, lithium precipitation caused by the difference in the amount of active material applied at the edge and the central portion can be reduced.

[0049] The N / P ratio according to Equation 1 below can be changed according to the positions where the positive electrode active material layer and the negative electrode active material layer face each other. The negative electrode specific capacity is generally designed to be higher than the positive electrode specific capacity, and thus the negative electrode can be formed to be larger than the positive electrode.

[0050]

[0051] The active material layer can be applied in a slurry state, and after roll pressing, a slitting process can be performed to form tabs. In this case, slitting is performed on the entire edge of the electrode portion, and a part of the edge of the active material layer is cut and removed. Therefore, the thickness of the remaining active material layer can vary according to the cutting position. As described above, the thickness difference of the active material layer may cause a difference in specific capacity, and if the negative electrode specific capacity is less than the positive electrode specific capacity such that the N / P ratio is less than 1, lithium precipitation may occur.

[0052] In particular, when misalignment occurs and the end of the active material layer of the positive electrode moves toward the inclined surface S at the edge of the active material layer 71 of the negative electrode, the difference in specific capacity with the positive electrode increases due to the reduction in the thickness of the portion of the active material layer 71 of the negative electrode corresponding to the inclined surface S.

[0053] In an embodiment of the present disclosure, an auxiliary layer 77 is formed to increase the specific capacity in the portion of the active material layer 71 of the negative electrode corresponding to the inclined surface, which is the region J1 (see Figure 3 and Figure 4 ) facing the end of the active material layer of the positive electrode. Therefore, phenomena such as lithium precipitation caused by the difference in specific capacity can be prevented or reduced.

[0054] The auxiliary layer 77 can be solidified by a curing or drying method separate from the formation of the active material layer 71. The auxiliary layer 77 can include an active material and a resin, and the active material and the resin can be mixed in a weight ratio of 99.9:0.1 to 90:10. The resin included in the auxiliary layer 77 can be a thermosetting resin. For example, it can include at least one of epoxy resin, phenolic resin, melamine resin, urea-formaldehyde resin, unsaturated polyester resin, alkyd resin, silicone resin, polyurethane resin, and polyimide resin.

[0055] In addition, the resin included in the auxiliary layer 77 can be a thermoplastic resin and can include, for example, at least one of polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, vinyl chloride, vinylidene chloride, fluororesin, acrylic resin, polyvinyl acetate resin, polyamide resin, polycarbonate resin, acetal resin, polyphenylene ether, polyester, and polysulfone.

[0056] In addition, the resin included in the auxiliary layer 77 can be a UV-curable resin and can include, for example, at least one of polyurethane acrylate, unsaturated polyester, epoxy acrylate, oxetane, vinyl ether resin, polyester acrylate, silicone acrylate, alicyclic epoxy resin, and glycidyl ether epoxy resin.

[0057] The UV-curable resin can further include a photoinitiator. The photoinitiator can include at least one of alkylbenzophenone polymerization initiators, acylphosphine oxide photoinitiators, oxime ester compounds (e.g., α-acyl oxime ester compounds), benzophenone compounds, acetophenone compounds, thioxanthone compounds, phenylglyoxylic acid compounds, azo compounds, diphenyl sulfide compounds, organic pigment compounds, iron phthalocyanine compounds, benzoin ether compounds, anthraquinone compounds, diazonium salts, iodonium salts, sulfonium salts, and metallocene compounds (e.g., titanocene compounds).

[0058] The UV-curable resin can have an organic solvent (N-methylpyrrolidone (NMP), acetone, etc.) or use water as a solvent.

[0059] The photoinitiator can include one type, but is not limited thereto, and can include a plurality of photoinitiators. Based on the total mass of the resin included in the auxiliary layer 77, the content of the photoinitiator can be 0.01% by mass to 10% by mass, preferably 0.1% by mass to 5% by mass, and more preferably 0.5% by mass to 3% by mass.

[0060] The surface of the substrate made of metal is smooth, so the active material layer 71 can be easily separated. However, in the embodiments of the present disclosure, by forming an auxiliary layer 77 including a resin on the active material layer 71 to fix the active material layer 71, the amount of the separated active material layer can be reduced.

[0061] Figure 2 Schematic cross-sectional view of an electrode for a rechargeable battery according to another embodiment of the present disclosure.

[0062] Since Figure 2 most of Figure 1 is the same as

[0063] Reference Figure 2 , an electrode for a rechargeable battery according to another embodiment of the present disclosure includes a substrate 70 and an active material layer 71 formed on the substrate 70. The edge of the active material layer 71 has an inclined surface S, and an auxiliary layer 77 is formed on the inclined surface S.

[0064] The auxiliary layer 77 includes a lower layer 7 and an upper layer 8 formed on the lower layer 7. The lower layer 7 can be made of a mixture of an active material and a resin, and the upper layer 8 can be made of a resin. In this case, the resins of the lower layer 7 and the upper layer 8 can be the same material, but are not limited thereto, and can be different materials.

[0065] The thickness of the auxiliary layer 77 can be 10% or less of the maximum thickness of the active material layer 71, and the thickness of the upper layer 8 can be 0.5 μm to 20 μm. In this case, the thickness of the auxiliary layer 77 is the average value obtained by measuring the thickness at points along the width D2 (see Figure 3 ) of the auxiliary layer 77, and these points divide the auxiliary layer 77 approximately into three equal parts in the width D2 (see Figure 3 ) direction. For example, if the width D2 (see Figure 3 ) is 10 mm, the thicknesses for determining the average value are at points 1 mm, 5 mm, and 9 mm from the edge of the auxiliary layer 77.

[0066] The above electrode can be used as a negative electrode of a rechargeable battery, and will be described below with reference to the accompanying drawings.

[0067] Figure 3 Schematic exploded perspective view of an electrode assembly according to an embodiment of the present disclosure, Figure 4 is Figure 3 top view of the positive electrode and the negative electrode of the electrode assembly of Figure 5 is Figure 4 cross-sectional view taken along line V-V' of Figure 6 and Figure 4 is cross-sectional view taken along line VI-VI' of

[0068] As Figures 3 to 6As shown, the electrode assembly 101 according to an embodiment of the present disclosure is a stacked electrode assembly 101, in which the negative electrode 200 and the positive electrode 100 are repeatedly stacked, and the separator 300 is inserted between the negative electrode 200 and the positive electrode 100. The separator 300 is disposed between the positive electrode 100 and the negative electrode 200 and insulates the positive electrode 100 and the negative electrode 200 from each other.

[0069] The positive electrode 100 includes: a substrate 72; a first electrode active region DA1 formed of an active material layer 73 on the substrate 72; and a first electrode uncoated region DA2, where the substrate 72 is exposed because the active material is not applied to the first electrode uncoated region DA2.

[0070] The material of the substrate 72 of the positive electrode 100 may be aluminum, and a compound capable of reversibly embedding and de-embedding lithium (lithiated embedding compound) may be used as the positive electrode active material forming the active material layer 73 of the positive electrode 100. Specifically, the active material may be at least one composite oxide formed of a metal (such as cobalt, manganese, nickel, and combinations thereof) and lithium. Based on the total weight of the active material layer 73 of the positive electrode 100, the content of the active material of the positive electrode 100 may be 90 wt% to 98 wt%.

[0071] The active material layer 73 of the positive electrode 100 may further include a binder and a conductive material. In this case, based on the total weight of the active material layer 73 of the positive electrode 100, the content of the binder may be 1 wt% to 5 wt%, and the content of the conductive material may be 1 wt% to 5 wt%.

[0072] The binder is used to bond the positive electrode active material particles well to each other and also bond the positive electrode active material well to the substrate as the positive electrode current collector. Representative examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc., but are not limited thereto. The conductive material is used to impart conductivity to the electrode and may be any electronically conductive material as long as the electronically conductive material does not cause a chemical change in the constructed battery.

[0073] The negative electrode 200 is Figure 1 or Figure 2 the negative electrode shown in, and includes: a second electrode active region DB1 in which an active material layer 71 is formed on a substrate 70; and a second electrode uncoated region where the substrate 70 is exposed by not applying the active material. The second electrode uncoated region may be used as an electrode tab for leading current to the outside, and for the convenience of the following description, will be referred to as the electrode tab DB2.

[0074] Reference Figures 3 to 6 The active material layer 71 of the negative electrode 200 has an inclined surface S at the edge, and the auxiliary layer 77 is formed on the inclined surface S. Accordingly, the specific capacity and thickness at the edge and the central portion C of the active material layer 71 can be the same.

[0075] During the grooving process for forming the electrode tab DB2, a laser cutting process can be performed along the periphery of the electrode. At this time, a part of the active material layer 71 located at the edge can also be removed. That is, since the cutting process is not performed on the electrode tab DB2 portion, the boundary L1 between the electrode tab DB2 and the active material layer 71 of the negative electrode 200 can have an inclined surface S of the active material layer 71 different from that of the active material layer 71 of the rest of the structure. The boundary L1 between the active material layer 71 of the negative electrode 200 and the electrode tab DB2 has the inclined surface S of the active material layer 71 initially formed without undergoing the cutting process. Accordingly, the width D1 of the edge of the active material layer 71 of the negative electrode 200 located at the boundary L1 with the electrode tab DB2 can be greater than the width D3 of the edge of the active material layer 71 of the negative electrode 200 located around the negative electrode 200 and subjected to the laser cutting process.

[0076] In this case, the cutting surface of the active material layer 71 of the laser-cut negative electrode 200 can be exposed to the outside and can have a cross-section perpendicular to the substrate 70 of the negative electrode 200. In laser cutting, the edge adjacent to the electrode tab DB2 can be removed from the end of the substrate 70 to a width within 1.5 mm (preferably 0.6 mm to 0.9 mm). The edge of the electrode tab located on the opposite side of the electrode tab DB2 and facing the electrode tab of the positive electrode 100 can be removed from the end of the substrate 70 to a width within 3 mm.

[0077] Meanwhile, the boundary L1 between the electrode tab DB2 and the active material layer 71 of the negative electrode 200 has an inclined surface S of the active material layer 71 not affected by the cutting process, and at the end L2 of the positive electrode 100 located overlapping with the inclined surface S, the active material layer 73 of the positive electrode 100 can be laser-cut together with the substrate 72. The cutting surface of the active material layer 73 of the laser-cut portion can have a cross-section perpendicular to the substrate 72 of the positive electrode 100.

[0078] As described above, since the end portion of the inclined surface S is cut, the end portion L2 of the positive electrode 100 disposed by laser cutting can be relatively thicker than the inclined surface S of the negative electrode 200. In this case, in a state where the thickness of the active material layer 73 at the edge of the positive electrode 100 is relatively thick, when it faces the inclined surface S of the active material layer 71 of the negative electrode 200, the difference in specific capacity in the region J1 where the positive electrode 100 and the negative electrode 200 face each other becomes larger, and lithium may precipitate due to insufficient negative electrode specific capacity (N / P < 1).

[0079] In an embodiment of the present disclosure, in order to provide a more uniform specific capacity in the region J1 where the positive electrode 100 and the negative electrode 200 face each other, an auxiliary layer 77 is added, and the amount of the applied active material becomes substantially the same at the edge and the central portion C. Therefore, the difference in specific capacity between the edge and the central portion C is reduced. Accordingly, lithium precipitation can be reduced, and safety can be improved.

[0080] Figure 7 Illustrate the effect of the auxiliary layer according to an embodiment of the present disclosure.

[0081] Reference Figure 7 and Figure 3 When the alignment position of the end portion L2 of the active material layer 73 of the positive electrode 100 and the edge of the active material layer 71 of the negative electrode 200 is misaligned or its edge is made shorter, the end portion L2 of the active material layer 73 of the positive electrode 100 extends toward the end of the active material layer 71 of the negative electrode 200 (see the arrow), so that the positive electrode 100 and the negative electrode 200 can face each other, as shown in the region J2. As described above, even if the positive electrode 100 extends to a position closer to the edge of the negative electrode 200, forming the auxiliary layer 77 in the embodiment of the present disclosure makes the thickness of the negative electrode 200 more uniform, and specific capacity non-uniformity does not occur in the region J2. Therefore, lithium precipitation does not occur due to insufficient negative electrode specific capacity (N / P < 1).

[0082] Refer again to Figure 3 and Figure 4 , the separator 300 is a polymer film through which lithium ions can pass. Polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof can be used as the separator. Hybrid multilayer films (such as polyethylene / polypropylene bilayer separators, polyethylene / polypropylene / polyethylene trilayer separators, or polypropylene / polyethylene / polypropylene trilayer separators) can also be used as the separator.

[0083] Figure 8 is a schematic perspective view of a rechargeable battery according to another embodiment of the present disclosure, and Figure 9 is a cross-sectional view taken along the line IX-IX' of Figure 8 .

[0084] As Figure 8 and Figure 9 shown in, the rechargeable battery 1000 according to an embodiment includes an electrode assembly 102, a case 27 accommodating the electrode assembly 102, and a cap assembly 30 mounted in an opening of the case 27.

[0085] The electrode assembly 102 includes a positive electrode 110 and a negative electrode 210 stacked in sequence, and a separator 300 (as described above) disposed therebetween. The separator 300 is disposed between the positive electrode 110 and the negative electrode 210 and insulates the positive electrode 110 and the negative electrode 210 from each other.

[0086] The electrode assembly 102 may be in the form of a jelly roll, where the separator 300 is inserted between the positive electrode (or first electrode) 110 and the negative electrode (or second electrode) 210, wound around a winding axis X, and then flattened.

[0087] The positive electrode 110 includes: a strip-shaped substrate having a long length in one direction; a first electrode active region DC1 including an active material layer formed on the substrate in the length direction of the substrate; and a first electrode uncoated region DC2 where the substrate is exposed by not applying the active material. The first electrode uncoated region DC2 may be formed longer along the first electrode active region DC1. Thus, a separate laser grooving process may not be performed to form an electrode tab, but the present disclosure is not limited thereto, and if necessary, the first electrode uncoated region DC2 in the form of an electrode tab protruding from the first electrode active region DC1 may be formed at regular intervals using a laser. In this case, the first electrode uncoated region DC2 may be formed such that a plurality of first electrode uncoated regions DC2 overlap each other to be electrically connected by welding.

[0088] The negative electrode 210 includes: a strip-shaped substrate having a long length in one direction; a second electrode active region DD1 including an active material layer formed on the substrate in the length direction of the substrate; and a second electrode uncoated region DD2 where the substrate is exposed by not applying the active material. The second electrode uncoated region DD2 may be formed longer along the second electrode active region DD1. Thus, a separate laser grooving process may not be performed to form an electrode tab, but the present disclosure is not limited thereto, and if necessary, the second electrode uncoated region DD2 in the form of an electrode tab protruding from the second electrode active region DD1 may be formed at regular intervals using a laser. In this case, the second electrode uncoated region DD2 may be formed such that a plurality of second electrode uncoated regions DD2 overlap each other to be electrically connected by welding.

[0089] In addition, the negative electrode 210 may have Figure 1 or Figure 2The edge shape of the negative electrode shown in [Fig.]. In other words, the active material layer 71 of the negative electrode 210 has an inclined surface S with respect to the substrate 70 at the edge, and the auxiliary layer 77 is formed on the inclined surface S. Accordingly, the specific capacity and thickness at the edge and the central portion C of the active material layer 71 can be the same. In this case, the edge of the active material layer 71 of the negative electrode 210 can be the position where the end of the active material layer 71 of the negative electrode 210 is located, and can be, for example, the region J3 adjacent to the second electrode uncoated region DD2.

[0090] As described above, in the embodiment of the present disclosure, the auxiliary layer 77 is formed on the inclined surface S of the active material layer 71 of the negative electrode 210 so that the thickness at the edge is constant, thereby reducing phenomena such as lithium precipitation. In other words, since the amount of the active material is substantially the same at the edge and the central portion C, the difference in specific capacity between the edge and the central portion C is reduced. Accordingly, lithium precipitation can be reduced, and safety can be improved.

[0091] Meanwhile, the electrode assembly 102 can be accommodated in the housing 27 together with the electrolyte, and the electrolyte includes a non-aqueous organic solvent and a lithium salt. The non-aqueous organic solvent serves as a medium through which ions participating in the electrochemical reaction of the battery can move. The lithium salt is a substance dissolved in the non-aqueous organic solvent and acts as a supply source of lithium ions in the battery, ensuring the basic operation of the rechargeable battery 1000 and promoting the movement of lithium ions between the positive electrode and the negative electrode. Representative examples of the lithium salt include one or two or more selected from the group consisting of: LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2)(where x and y are natural numbers, for example, integers from 1 to 20), LiCl, LiI, and LiB(C2O4)2 (lithium bis(oxalate) borate (LiBOB)) as carrier salts. The concentration of the lithium salt can be in the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within such a range, excellent electrolyte performance can be provided because the electrolyte has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0092] The housing 27 can be made of a metal (such as aluminum) and can have a substantially rectangular parallelepiped shape. One side of the housing 27 can be open, and the cover plate 31 can be installed on the open side of the housing 27.

[0093] The lid assembly 30 includes a cover plate 31 coupled to the housing 27 to block an opening of the housing 27, a positive electrode terminal 21 electrically connected to the positive electrode 110, and a negative electrode terminal 22 electrically connected to the negative electrode 210, wherein the positive electrode terminal 21 and the negative electrode terminal 22 protrude to the outside of the cover plate 31. The cover plate 31 is formed in the form of a long plate extending in one direction and is coupled to the opening of the housing 27.

[0094] The cover plate 31 has an injection hole 32 penetrating into the interior of the housing 27. The injection hole 32 is for injecting an electrolyte, and a sealing plug 38 can be installed in the injection hole 32. Additionally, an exhaust plate 39 having a notch 39a is installed in the exhaust hole 34 such that the cover plate 31 can be opened under a set pressure.

[0095] The positive electrode terminal 21 and the negative electrode terminal 22 are installed to protrude upward from the cover plate 31. The positive electrode terminal 21 is electrically connected to the positive electrode 110 through a current collecting tab 41, and the negative electrode terminal 22 is electrically connected to the negative electrode 210 through a current collecting tab 42.

[0096] A terminal connection member 25 is installed between the positive electrode terminal 21 and the current collecting tab 41 to electrically connect the positive electrode terminal 21 and the current collecting tab 41. The terminal connection member 25 is inserted into a hole formed in the positive electrode terminal 21 such that its upper end is fixed to the positive electrode terminal 21 by welding, and its lower end is fixed to the current collecting tab 41 by welding.

[0097] Between the terminal connection member 25 and the cover plate 31, a gasket 59 for sealing is inserted into the hole through which the terminal connection member 25 passes, and a lower insulating member 43 is installed below the cover plate 31, and the lower portion of the terminal connection member 25 is inserted into the lower insulating member 43. A connection plate 58 is installed between the positive electrode terminal 21 and the cover plate 31 to electrically connect them. The terminal connection member 25 is installed by being inserted into the connection plate 58. Accordingly, the cover plate 31 and the housing 27 are charged by the positive electrode 110.

[0098] A terminal connection member 26 is installed between the negative electrode terminal 22 and the current collecting tab 42 to electrically connect the negative electrode terminal 22 and the current collecting tab 42. The terminal connection member 26 is inserted into a hole formed in the negative electrode terminal 22 such that its upper end is fixed to the negative electrode terminal 22 by welding, and its lower end is fixed to the current collecting tab 42 by welding.

[0099] Between the negative electrode terminal 22 and the cover plate 31, a gasket 59 for sealing is inserted and installed into the hole through which the terminal connection member 26 passes, and an upper insulating member 54 is installed to insulate between the negative electrode terminal 22 and the cover plate 31. The terminal connection member 26 can be installed by being inserted into a hole of the upper insulating member 54, and the upper insulating member 54 can be formed to surround the end of the negative electrode terminal 22.

[0100] Further, below the cover plate 31, a lower insulating member 45 is installed to insulate the negative electrode terminal 22 and the current collecting tab 42 from the cover plate 31.

[0101] A short - circuit hole 37 is formed in the cover plate 31, and a short - circuit member 56 is installed in the short - circuit hole 37. The short - circuit member 56 includes a bent portion that protrudes downward in an arc shape and an edge portion that is formed on the outside of the bent portion and fixed to the cover plate 31. The upper insulating member 54 may have a cutout that overlaps with the short - circuit hole 37, and the short - circuit member 56 overlaps with the negative electrode terminal 22 exposed through the cutout.

[0102] The short - circuit member 56 is electrically connected to the cover plate 31 and deforms when the internal pressure of the rechargeable battery 1000 increases, resulting in a short - circuit between the positive electrode 110 and the negative electrode 210. When gas is generated due to an abnormal reaction inside the rechargeable battery 1000, the internal pressure of the rechargeable battery 1000 increases. When the internal pressure of the rechargeable battery 1000 becomes greater than a predetermined pressure, the bent portion deforms to protrude upward. At this time, the negative electrode terminal 22 and the short - circuit member 56 come into contact with each other, causing a short - circuit.

[0103] To facilitate the short - circuit between the negative electrode terminal 22 and the short - circuit member 56, the negative electrode terminal 22 may further include at least one protrusion (not shown) protruding toward the short - circuit member 56, and the protrusion may be spaced apart from the short - circuit member 56.

[0104] In the above - described embodiment, a rechargeable battery including a prismatic case has been described, but the present disclosure is not limited thereto. The rechargeable battery may include a cylindrical case and a pouch - type case.

[0105] Although the present disclosure has been described in connection with presently considered practical embodiments, it should be understood that the present disclosure is not limited to the disclosed embodiments. On the contrary, the present disclosure is intended to cover various modifications and equivalent arrangements included within the scope of the claims.

Claims

1. An electrode for a rechargeable battery, comprising: A substrate having an uncoated electrode area; An active material layer formed on the substrate to form an electrode active area, the active material layer having an end portion with an inclined surface relative to the substrate; And An auxiliary layer formed on the inclined surface of the active material layer, Wherein the auxiliary layer comprises an active material and a resin.

2. The electrode for a rechargeable battery according to claim 1, wherein the active material and the resin included in the auxiliary layer are mixed in a weight ratio of 99.9:0.1 to 90:

10.

3. The electrode for a rechargeable battery according to claim 1, wherein the auxiliary layer comprises a lower layer made of an active material and a resin and an upper layer made of a resin and located on the lower layer.

4. The electrode for a rechargeable battery according to claim 3, wherein the active material and the resin of the lower layer are mixed in a weight ratio of 99.9:0.1 to 90:

10.

5. The electrode for a rechargeable battery according to claim 3, wherein The thickness of the upper layer is 0.5 μm to 20 μm.

6. The electrode for a rechargeable battery according to claim 1, wherein the thickness of the auxiliary layer is 10% or less of the maximum thickness of the active material layer.

7. The electrode for a rechargeable battery according to claim 1, wherein the resin comprises one of a thermosetting resin, a UV curable resin, and a thermoplastic resin.

8. The electrode for a rechargeable battery according to claim 7, wherein the thermosetting resin comprises at least one of an epoxy resin, a phenol resin, a melamine resin, a urea formaldehyde resin, an unsaturated polyester resin, an alkyd resin, a silicone resin, a polyurethane resin, and a polyimide resin.

9. The electrode for a rechargeable battery according to claim 7, wherein the thermoplastic resin comprises at least one of polytetrafluoroethylene, polyethylene, polypropylene, polystyrene, vinyl chloride, vinylidene chloride, fluororesin, acrylic resin, polyvinyl acetate resin, polyamide resin, polycarbonate resin, acetal resin, polyphenylene ether, polyester, and polysulfone.

10. The electrode for a rechargeable battery according to claim 7, wherein the UV curable resin comprises at least one of polyurethane acrylate, unsaturated polyester, epoxy acrylate, oxetane, vinyl ether resin, polyester acrylate, silicone acrylate, alicyclic epoxy resin, and glycidyl ether epoxy resin.

11. The electrode for a rechargeable battery according to claim 10, wherein the UV curable resin further comprises a photoinitiator, and Based on the total mass of the resin included in the auxiliary layer, the content of the photoinitiator is 0.01% by mass to 10% by mass.

12. The electrode for a rechargeable battery according to claim 1, wherein the active material is a negative electrode active material including a carbon-based negative electrode active material.

13. The electrode for a rechargeable battery according to claim 1, wherein the uncoated electrode area of the substrate protrudes from the electrode active area, and The width of the first edge of the active material layer, which is located at the boundary between the uncoated area of the electrode and the active area of the electrode and has the inclined surface, is greater than the width of the second edge of the active material layer, which is located at the end of the active area of the electrode and has the inclined surface.

14. The electrode for a rechargeable battery according to claim 13, wherein the second edge of the active material layer is cut with a laser, and the resulting cut surface is exposed to the outside of the electrode.

15. An electrode assembly, comprising: a negative electrode including the electrode for a rechargeable battery according to any one of claims 1 to 14, a positive electrode overlapping the negative electrode, and a separator disposed between the negative electrode and the positive electrode, wherein a part of the end portion of the positive electrode corresponds to the inclined surface of the negative electrode of the auxiliary layer formed thereon.

16. The electrode assembly according to claim 15, wherein, The end portion of the active material layer of the positive electrode corresponding to the inclined surface of the negative electrode is cut with a laser to have a cross-section perpendicular to the substrate of the positive electrode.

17. The electrode assembly according to claim 15, wherein the electrode assembly includes a plurality of negative electrodes, a plurality of separators, and a plurality of positive electrodes, and the negative electrodes, the positive electrodes, and the separators between the negative electrodes and the positive electrodes are repeatedly stacked to form a sheet, and wherein the uncoated area of the electrode of the negative electrode and the uncoated area of the electrode of the positive electrode protrude from the sheet in opposite directions.

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