Positive electrode for rechargeable lithium batteries and rechargeable lithium batteries including positive electrodes.

Abstract

This application provides a positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the positive electrode. The positive electrode for the rechargeable lithium battery includes a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector. The positive electrode is rectangular in shape, having a horizontal length longer than its vertical length, and having upper and lower sides of equal length. The positive electrode active material layer includes two trapezoidal patterns formed in its surface. The two trapezoidal patterns have short sides adjacent to each other, and the long sides of the two trapezoidal patterns are adjacent to the upper and lower sides of the positive electrode active material layer, respectively.

Description

Technical Field

[0001] A positive electrode for a rechargeable lithium battery and a rechargeable lithium battery including the positive electrode are disclosed. Background Technology

[0002] Rechargeable lithium-ion batteries are rechargeable and, compared to traditional lead-acid, nickel-cadmium, nickel-metal hydride, and nickel-zinc batteries, have three to four times the energy density per unit weight. They can also be charged at high rates. Therefore, rechargeable lithium-ion batteries are being commercially manufactured for use in laptops, cell phones, power tools, electric bicycles, etc., and research is underway to provide additional energy density within these batteries.

[0003] This rechargeable lithium battery is manufactured by injecting an electrolyte into an electrode assembly, which includes a positive electrode comprising a positive electrode active material capable of intercalating / deintercalating lithium ions and a negative electrode comprising a negative electrode active material capable of intercalating / deintercalating lithium ions.

[0004] Abnormal heating can typically occur within 10 charge / discharge cycles of a rechargeable lithium-ion battery. To improve the reliability of rechargeable lithium-ion batteries, this abnormal heating phenomenon must be suppressed. Summary of the Invention

[0005] Some example implementations provide a positive electrode for a rechargeable lithium battery that suppresses abnormal heating and improves the reliability of the rechargeable lithium battery.

[0006] Some example embodiments provide a positive electrode comprising a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector; wherein the positive electrode is rectangular in shape, having a horizontal length longer than its vertical length, and having an upper side and a lower side of equal length; the positive electrode active material layer includes two trapezoidal patterns formed in the surface of the positive electrode active material; the trapezoidal patterns (two trapezoidal patterns) have short sides adjacent to each other; the long sides of the two trapezoidal patterns are adjacent to the upper side and the lower side of the positive electrode active material layer, respectively.

[0007] Some example implementations provide a rechargeable lithium battery including a positive electrode according to some example implementations.

[0008] The positive electrode according to the above embodiments can prevent abnormal heating of rechargeable lithium batteries and improve the reliability of rechargeable lithium batteries. Attached Figure Description

[0009] Figure 1A This is a view of the surface of the positive electrode according to some example embodiments. Figure 1B This is a view of the surface of a patternless positive electrode. Figure 1C A view of the surface of a positive electrode with a vertical pattern, and Figure 1D A view of the surface of a positive electrode with a diagonal pattern.

[0010] Figures 2-5 A view of a rechargeable lithium battery according to some example embodiments.

[0011] <Explanation of Figure Markers>

[0012] 100: Rechargeable lithium battery; 10: Positive electrode

[0013] 11: Positive electrode lead connector 12: Positive electrode terminal

[0014] 20: Negative electrode 21: Negative electrode lead connector

[0015] 22: Negative electrode terminal; 30: Diaphragm

[0016] 40: Electrode assembly; 50: Housing

[0017] 60: Sealing component; 70: Electrode terminal piece

[0018] 71: Positive electrode connector; 72: Negative electrode connector Detailed Implementation

[0019] The embodiments of this disclosure will be described in detail below. However, these embodiments are exemplary, and this disclosure is not limited to the explicitly disclosed embodiments.

[0020] As used herein, unless otherwise specifically defined, it will be understood that when an element (such as a layer, film, region, or substrate) is referred to as being "on" another element (such as a layer, film, region, or substrate), it may be directly on the other element (such as a layer, film, region, or substrate) or there may be an intermediary element present.

[0021] As used herein, the singular may also include the plural unless otherwise specified. Additionally, unless otherwise indicated, “A or B” may mean “including A, including B, or including both A and B”.

[0022] As used herein, “combination of” may mean a mixture, stack, complex, copolymer, alloy, blend, or reaction product of the components.

[0023] (Positive electrode)

[0024] Abnormal heating can occur because the gases generated during the charging and discharging of rechargeable lithium batteries cannot escape smoothly. The gases physically separate the positive and negative electrodes, increasing local resistance and causing lithium (Li) metal to deposit on the surface of the negative electrode. The deposited lithium metal creates micropores in the separator between the positive and negative electrodes, leading to a heat-generating micro-short circuit. This micro-short circuit ends when the separator closes.

[0025] An exemplary embodiment of this disclosure provides a positive electrode for a rechargeable lithium-ion battery, comprising a positive electrode current collector and a positive electrode active material layer on the positive electrode current collector. The positive electrode is rectangular in shape, having a horizontal length longer than its vertical length, and having upper and lower sides of equal length. The positive electrode active material layer has two trapezoidal patterns on its surface, the two trapezoidal patterns having short sides adjacent to each other (e.g., in contact), and the long sides of the two trapezoidal patterns being adjacent to (e.g., in contact with) the upper and lower sides of the positive electrode active material layer, respectively. Previous pattern shapes in the positive electrode have limitations in suppressing abnormal heat generation and temperature rise, but the use of trapezoidal patterns improves this aspect.

[0026] Figure 1A This is a view of the surface of the positive electrode according to some example embodiments. Figure 1B This is a view of the surface of a patternless positive electrode. Figure 1C A view of the surface of a positive electrode with a vertical pattern, and Figure 1D A view of the surface of a positive electrode with a diagonal pattern.

[0027] As will be described later, when a positive electrode is used in a rechargeable lithium battery, the positive electrode, separator, and negative electrode can be stacked and then wound. In this arrangement, in two trapezoidal patterns in which the short sides are in contact with each other, the corners of the acute angles of the long sides of each of the two trapezoidal patterns are located at both ends of the wound stack. Therefore, gas venting is excellent, and abnormal heating and temperature rise are significantly suppressed. Accordingly, by using the positive electrode of some example embodiments, even if gas is generated during charging and discharging during the formation of the rechargeable lithium battery, gas can be effectively vented, and the formation of gaps between the positive and negative electrodes, local resistance increases, and lithium (Li) metal deposition on the surface of the negative electrode can be effectively suppressed. Therefore, the positive electrode of some example embodiments can significantly suppress abnormal heating and temperature rise compared to the pattern shape of the positive electrode in the prior art.

[0028] The following describes in detail the positive electrode for a rechargeable lithium battery according to embodiments of the present disclosure.

[0029] pattern

[0030] Each of the two trapezoidal patterns can be an engraved pattern forming a channel for gas exhaust. Based on the thickness of 100% of the positive electrode active material layer, the engraving pattern of each of the two trapezoidal patterns can be formed from the surface of the positive electrode active material layer at a depth of approximately 1% to approximately 50%, approximately 5% to approximately 20%, or approximately 10% to approximately 15%. The width of each of the two engraved trapezoidal patterns can be approximately 0.5 μm to approximately 10 μm, approximately 1 μm to approximately 8 μm, or approximately 3 μm to approximately 5 μm. Here, the width of the trapezoidal pattern can refer to the distance between the short side and the long side of the trapezoidal pattern. The ratio of the length of the short side to the length of the long side of each of the two trapezoidal patterns can be approximately 5:100 to approximately 98:100, approximately 5:100 to approximately 95:100, approximately 10:100 to approximately 90:100, or approximately 30:100 to approximately 60:100. (For example, relative to) the obtuse angle of the shorter side of each of the two trapezoidal patterns may be about 100° to about 170°, about 110° to about 160°, or about 125° to about 145°. (For example, relative to) the acute angle of the longer side of each of the two trapezoidal patterns may be about 10° to about 80°, about 20° to about 70°, or about 35° to about 55°.

[0031] When the above range is met, gas discharge is improved, and abnormal heating and temperature rise can be significantly suppressed.

[0032] Positive electrode active material

[0033] The positive electrode active material can be a compound capable of intercalating and deintercalating lithium (lithiation intercalation compound). Specifically, a composite oxide of one or more types (e.g., at least one) of lithium with a metal selected from cobalt, manganese, nickel and combinations thereof (e.g., at least one of cobalt, manganese and nickel) can be used.

[0034] The composite oxide can be a lithium transition metal composite oxide, and specific examples include lithium nickel oxides, lithium cobalt oxides, lithium manganese oxides, lithium iron phosphate compounds, cobalt-free lithium nickel manganese oxides, or combinations thereof. As an example, compounds represented by any of the following chemical formulas can be used: Li a A 1-b X b O 2-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Mn 2-b X b O 4-c D c (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b- c Cob X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0≤α≤2); Li a Ni 1-b-c Mn b X c O 2-α D α (0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.5, 0≤α≤2); Li a Ni b Co c L 1 d G e O2(0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0≤e≤0.1); Li a NiG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-b G b O2(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4(0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn 1-g G g PO4(0.90≤a≤1.8, 0≤g≤0.5); Li (3-f) Fe2(PO4)3 (0≤f≤2); and Li a FePO4 (0.90≤a≤1.8). In these chemical formulas, A is Ni, Co, Mn or a combination thereof; X is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or a combination thereof; D is O, F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; and L 1 It is Mn, Al, or a combination thereof.

[0035] The positive electrode active material may be, for example, lithium nickel oxide represented by the following chemical formula 11, lithium cobalt oxide represented by the following chemical formula 12, lithium iron phosphate compound represented by the following chemical formula 13, cobalt-free lithium nickel manganese oxide represented by the following chemical formula 14, or a combination thereof.

[0036] Chemical Formula 11:

[0037] Li a1 Ni x1 M 1 y1 M 2 z1 O 2-b1 X b1

[0038] In chemical formula 11, 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.7, 0 ≤ z1 ≤ 0.7, 0.9 ≤ x1 + y1 + z1 ≤ 1.1, and 0 ≤ b1 ≤ 0.1, M 1 and M 2 Each of the elements is independently one or more selected from Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more selected from F, P, and S. In a further embodiment, 0.6 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.4, and 0 ≤ z1 ≤ 0.4, or 0.8 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.2, and 0 ≤ z1 ≤ 0.2.

[0039] Chemical formula 12:

[0040] Li a2 Co x2 M 3 y2 O 2-b2 X b2

[0041] In chemical formula 12, 0.9 ≤ a² ≤ 1.8, 0.7 ≤ x² ≤ 1, 0 ≤ y² ≤ 0.3, 0.9 ≤ x² + y² ≤ 1.1, and 0 ≤ b² ≤ 0.1, M 3 X is one or more of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Nb, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more of F, P, and S.

[0042] Chemical formula 13:

[0043] Li a3 Fe x3 M 4 y3 PO 4-b3 X b3

[0044] In Chemical Formula 13, 0.9 ≤ a3 ≤ 1.8, 0.6 ≤ x3 ≤ 1, 0 ≤ y3 ≤ 0.4, 0.9 ≤ x3 + y3 ≤ 1.1, and 0 ≤ b3 ≤ 0.1, M 4 is one or more of Al, B, Ba, Ca, Ce, Co, Cr, Cu, Mg, Mn, Mo, Ni, Nb, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more of F, P, and S.

[0045] Chemical Formula 14:

[0046] Li a4 Ni x4 Mn y4 M 5 z4 O 2-b4 X b4

[0047] In Chemical Formula 14, 0.9 ≤ a4 ≤ 1.8, 0.8 ≤ x4 < 1, 0 < y4 ≤ 0.2, 0 ≤ z4 ≤ 0.2, 0.9 ≤ x4 + y4 + z4 ≤ 1.1, and 0 ≤ b4 ≤ 0.1, M 5 is one or more of Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Se, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X is one or more of F, P, and S.

[0048] For example, the positive electrode active material can be a high-nickel positive electrode active material, in which based on 100 mol% of the metals other than lithium in the lithium transition metal composite oxide, the nickel content is greater than or equal to about 80 mol%, greater than or equal to about 85 mol%, greater than or equal to about 90 mol%, greater than or equal to about 91%, or greater than or equal to about 94 mol% and less than or equal to about 99 mol%. The high-nickel positive electrode active material can provide high capacity and is used in high-capacity, high-density rechargeable lithium batteries.

[0049] positive electrode

[0050] The positive electrode for a rechargeable lithium battery can include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector.

[0051] The positive electrode active material layer can include a positive electrode active material and can further include a binder and / or a conductive material. The positive electrode can further include components that can be used as a sacrificial positive electrode.

[0052] Based on a 100 wt% positive electrode active material layer, the amount of positive electrode active material can be approximately 90 wt% to approximately 99 wt%. Based on a 100 wt% positive electrode active material layer, the amounts of binder and conductive material can each be approximately 0.5 wt% to approximately 5 wt%.

[0053] Binders improve the adhesion properties between the active material particles of the positive electrode and the adhesion properties between the active material particles of the positive electrode and the positive electrode current collector. Examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, epoxy resins, (meth)acrylate resins, polyester resins, and nylon.

[0054] Any conductive material that provides electrode conductivity and does not cause chemical changes in the battery can be used as a conductive material. Examples of conductive materials include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials including metal powders or fibers of copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0055] (Rechargeable lithium battery)

[0056] Some example implementations provide a rechargeable lithium battery including a positive electrode, a negative electrode, and a separator between the positive and negative electrodes according to the above embodiments.

[0057] In some exemplary embodiments of rechargeable lithium batteries, a stack of positive electrode, separator, and negative electrode can be wound. In this configuration, the horizontal length of the positive electrode can be the winding direction of the stack. As a result, the gas venting effect at both ends of the wound stack is excellent, and abnormal heating and temperature rise can be significantly suppressed. Accordingly, the rechargeable lithium battery of the exemplary embodiments can effectively vent the gas generated during charging / discharging during formation, thereby effectively preventing gap formation between the positive and negative electrodes, preventing an increase in local resistance, and preventing lithium (Li) metal deposition on the surface of the negative electrode.

[0058] The above description will be omitted below, and a rechargeable lithium battery according to some example embodiments will be described in detail.

[0059] Negative electrode active material

[0060] The negative electrode active material may include a material that can reversibly intercalate / deintercalate lithium ions, lithium metal, a lithium metal alloy, a material capable of doping / de-doping lithium, or a transition metal oxide.

[0061] The material that can reversibly intercalate / deintercalate lithium ions may include, for example, crystalline carbon, amorphous carbon, or a combination thereof as a carbon-based negative electrode active material. The crystalline carbon may be natural graphite or artificial graphite in an irregular, flaky, sheet-like, spherical, or fibrous shape. The amorphous carbon may be soft carbon, hard carbon, a mesophase pitch carbonized product, calcined coke, etc.

[0062] The lithium metal alloy includes an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn.

[0063] The material capable of doping / de-doping lithium may be a Si-based negative electrode active material or a Sn-based negative electrode active material. The Si-based negative electrode active material may include silicon, a silicon-carbon composite, SiO x (0 < x ≤ 2), a Si-Q alloy, or a combination thereof. In the formula Si-Q, Q is an element selected from 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. The Sn-based negative electrode active material may be Sn, SnO x (0 < x ≤ 2, such as SnO2), a Sn-based alloy, or a combination thereof.

[0064] The silicon-carbon composite may be a composite of silicon and amorphous carbon. According to an exemplary embodiment, the silicon-carbon composite may be in the form of silicon particles and amorphous carbon coated on the surface of the silicon particles. For example, the silicon-carbon composite may include secondary particles (cores) in which silicon primary particles are aggregated and an amorphous carbon coating (shell) on the surface of the secondary particles. Amorphous carbon may also be present between the silicon primary particles. For example, the silicon primary particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0065] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles and an amorphous carbon coating on the surface of the core.

[0066] The Si-based negative electrode active material and / or the Sn-based negative electrode active material may be mixed with the carbon-based negative electrode active material.

[0067] negative electrode

[0068] The negative electrode for a rechargeable lithium-ion battery includes a negative electrode current collector and a negative electrode active material layer on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material and may further include a binder and / or a conductive material. For example, the negative electrode active material layer may include about 90 wt% to about 99 wt% of negative electrode active material, about 0.5 wt% to about 5 wt% of binder, and about 0.5 wt% to about 5 wt% of conductive material.

[0069] The binder is used to bond the active material particles of the negative electrode to each other and also to the negative electrode current collector. The binder can be a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof.

[0070] Non-aqueous adhesives may include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or combinations thereof.

[0071] Waterborne adhesives may include styrene-butadiene rubber, (meth)acrylated styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, or combinations thereof.

[0072] When an aqueous binder is used as a binder in the negative electrode active material layer, it may further include a cellulose compound capable of imparting viscosity. As a cellulose compound, one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts may be mixed and used. The alkali metal may be Na, K, or Li.

[0073] Dry adhesives are polymeric materials capable of being fibrous. Dry adhesives may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or combinations thereof.

[0074] Any conductive material that provides electrode conductivity and does not cause chemical changes in the battery can be used as a conductive material. Examples of conductive materials include: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fibers, carbon nanofibers, carbon nanotubes, etc.; metallic materials including metal powders or fibers of copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0075] The negative electrode current collector may include one of the following: copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and combinations thereof.

[0076] electrolyte

[0077] Electrolytes used in rechargeable lithium batteries include non-aqueous organic solvents and lithium salts.

[0078] Non-aqueous organic solvents are used as media for transporting ions that participate in the electrochemical reactions of a battery. Non-aqueous organic solvents may include carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, aprotic solvents, or combinations thereof.

[0079] Carbonate solvents may include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC). Ester solvents may include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolactone, mevalonolactone, valproic acid lactone, caprolactone, etc. Ether solvents may include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, tetrahydrofuran, etc. Additionally, ketone solvents may include cyclohexanone, etc. Alcohol solvents may include ethanol, isopropanol, etc., and aprotic solvents may include nitriles, such as R-CN (where R is a C2-C20 straight-chain, branched, or cyclic hydrocarbon group, and may include double bonds, aromatic rings, or ether bonds, etc.); amides, such as dimethylformamide; dioxolane, such as 1,3-dioxolane, 1,4-dioxolane, etc.; sulfolane, etc.

[0080] Non-aqueous organic solvents can be used alone or in mixtures of two or more types.

[0081] In addition, when using carbonate solvents, cyclic carbonates and chain carbonates can be mixed and used, and cyclic carbonates and chain carbonates can be mixed in a volume ratio of about 1:1 to about 1:9.

[0082] The electrolyte may further include vinyl ethylene carbonate, vinylene carbonate, fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, or combinations thereof as additives.

[0083] Lithium salts dissolved in non-aqueous organic solvents supply lithium ions in batteries, ensuring basic operation of rechargeable lithium batteries and improving lithium ion transport between the positive and negative electrodes. Examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2 (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFBOP), and lithium bis(oxalate)borate (LiBOB).

[0084] diaphragm

[0085] Depending on the type of rechargeable lithium battery, a separator may be present between the positive and negative electrodes. The separator may include polyethylene (PE) separators, polypropylene separators, polyvinylidene fluoride separators, or multilayer films of two or more layers thereof (such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polypropylene three-layer separators, polypropylene / polypropylene / polypropylene three-layer separators, etc.).

[0086] The diaphragm may include a porous substrate and a coating on one or both surfaces of the porous substrate, comprising organic materials, inorganic materials, or combinations thereof.

[0087] The porous substrate may be a polymer membrane formed from any one of the following polymers and / or copolymers or mixtures thereof: polyolefins (such as polyethylene and polypropylene), polyesters (such as polyethylene terephthalate and polybutylene terephthalate), polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymers, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., ).

[0088] Organic materials may include polymers such as polyvinylidene fluoride or (meth)acrylic acid polymers.

[0089] Inorganic materials may include inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. However, this disclosure is not limited thereto.

[0090] Organic and inorganic materials can be mixed in a single coating. In other embodiments, a first coating comprising organic materials and a second coating comprising inorganic materials can be stacked.

[0091] Rechargeable lithium batteries

[0092] Depending on their shape, rechargeable lithium batteries can be cylindrical, prismatic, pouch-shaped, or coin-shaped, etc. Figures 2-5 This is a schematic diagram illustrating a rechargeable lithium battery according to some example embodiments. Figure 2 It is a cylindrical battery. Figure 3 It is a prismatic battery, and Figure 4 and Figure 5 It is a pouch-shaped battery. (Reference) Figures 2-5 The rechargeable lithium battery 100 includes an electrode assembly 40 (having a separator 30 inserted between a positive electrode 10 and a negative electrode 20) and a housing 50 (containing the electrode assembly 40). The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). Figure 2 As shown, the rechargeable lithium battery 100 may include a sealing member 60 of a sealed housing 50. (As...) Figure 3 As shown, the rechargeable lithium battery 100 may include a positive electrode lead connector 11, a positive electrode terminal 12, a negative electrode lead connector 21, and a negative electrode terminal 22. For example... Figure 4 and Figure 5 As shown, the rechargeable lithium battery 100 may include electrode terminals 70, namely positive electrode terminal 71 and negative electrode terminal 72, forming an electrical path for guiding current formed in the electrode assembly 40 to the outside.

[0093] According to some example embodiments, rechargeable lithium batteries can be used in automobiles, mobile phones, and / or various types of electronic devices. However, this disclosure is not limited to these examples.

[0094] The following describes embodiments and comparative examples of this disclosure. However, the following embodiments are merely examples of this disclosure, and this disclosure is not limited to the following embodiments.

[0095] Example 1

[0096] (1) Manufacturing of the positive electrode

[0097] To manufacture the positive electrode, a positive electrode current collector is formed from an aluminum foil with a thickness of 12 μm.

[0098] By using LiNi as the positive electrode active material 0.91 Co 0.05 Al 0.04 O2, polyvinylidene fluoride (PVDF) as a binder, and carbon black as a conductive agent are mixed in a weight ratio of 92:4:4. The mixture is then dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode active material slurry. The positive electrode active material slurry is coated onto a 150 μm thick aluminum foil to form a positive electrode active material layer.

[0099] On the surface of the positive electrode active material layer, a layer such as Figure 1A The image shows two trapezoidal patterns. Two trapezoidal patterns are etched such that the short sides are adjacent to each other, and the long sides are adjacent to the upper and lower sides of the positive electrode active material layer.

[0100] Based on the thickness of the 100% positive electrode active material layer, each of the two trapezoidal patterns is formed to a depth of 15% from the surface of the positive electrode active material layer. The two trapezoidal patterns are each formed with a width of 5 μm, an obtuse angle of 120° on the short side, a ratio of 50:100 between the length of the short side and the length of the long side, and an acute angle of 60° on the long side.

[0101] (2) Manufacturing of rechargeable lithium battery cells

[0102] Artificial graphite and silicon particles were mixed in a weight ratio of 93.5:6.5 to prepare a negative electrode active material. The negative electrode active material, styrene-butadiene rubber binder and carboxymethyl cellulose were mixed in a weight ratio of 97:1:2 and then dispersed in distilled water to prepare a negative electrode active material slurry.

[0103] The negative electrode active material slurry is coated onto a Cu foil to a thickness of 8 μm, dried at 100 °C, and then pressed to form a negative electrode active material layer.

[0104] An electrolyte was prepared by mixing 1.5M lithium salt (LiPF6) with a carbonate solvent comprising ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC) in a volume ratio of 20:40:40.

[0105] The manufactured positive electrode, PE separator, and negative electrode are stacked, wound, and then inserted into a prismatic housing. Electrolyte is injected into the prismatic housing to form a rechargeable lithium battery cell.

[0106] Example 2

[0107] The positive electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that the width of the two trapezoidal patterns was changed to 3 μm.

[0108] Example 3

[0109] The positive electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that the width of the two trapezoidal patterns was changed to 8 μm.

[0110] Example 4

[0111] The positive electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that the depth of the two trapezoidal patterns was changed to 30%.

[0112] Example 5

[0113] The positive electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that the depth of the two trapezoidal patterns was changed to 10%.

[0114] Comparative Example 1 (for reference)

[0115] The positive electrode and rechargeable lithium battery cell were manufactured in essentially the same manner as in Example 1, except that the two trapezoidal patterns were not formed.

[0116] Comparative Example 2

[0117] Will as Figure 1C The vertical pattern shown is formed on the surface of the positive electrode active material layer.

[0118] Based on the thickness of the 100% positive electrode active material layer, vertical patterns are engraved to a depth of 15% starting from the surface of the positive electrode active material layer. The vertically engraved patterns have a width of 5 μm, and a total of four vertically engraved patterns are formed by setting the distance between adjacent patterns to an equal 20% of the long side.

[0119] Except for the vertical pattern in the positive electrode, the rechargeable lithium battery cell of Comparative Example 2 was manufactured in essentially the same manner as in Example 1.

[0120] Comparative Example 3

[0121] Will as Figure 1C The horizontal pattern shown is formed on the surface of the positive electrode active material layer.

[0122] Based on the thickness of the 100% positive electrode active material layer, horizontal patterns are engraved to a depth of 15% starting from the surface of the positive electrode active material layer. The horizontal engraved patterns have a width of 5 μm, and a total of four horizontal engraved patterns are formed by setting the distance between adjacent patterns to be equal to 20% of the shorter side.

[0123] Except for the horizontal pattern in the positive electrode, the rechargeable lithium battery cell of Comparative Example 3 was manufactured in substantially the same manner as in Example 1.

[0124] Comparative Example 4

[0125] Will as Figure 1D The two diagonal patterns shown are formed on the surface of the positive electrode active material layer.

[0126] Based on the thickness of the 100% positive electrode active material layer, the diagonal pattern is engraved to a depth of 15% starting from the surface of the positive electrode active material layer. The thickness of the engraving line of each diagonal pattern is made to be 5 μm, forming a total of two diagonal engraved patterns.

[0127] Except for the diagonal pattern in the positive electrode, the rechargeable lithium battery cell of Comparative Example 4 was manufactured in essentially the same manner as in Example 1.

[0128] Evaluation Example

[0129] Each of the rechargeable lithium-ion battery cells in the examples and comparative examples was evaluated using the methods described below, and the results are shown in Table 1 below.

[0130] Connect the rechargeable lithium battery cell to the charger in an environment with an ambient temperature of 55°C. After charging and discharging the rechargeable lithium battery cell 10 times at 0.33C / 0.33C cutoff voltage of 0.05V, attach a thermocouple to the rechargeable lithium battery cell to measure the temperature.

[0131] Abnormal heating was considered to have occurred when a temperature rise of 5°C or higher occurred during 10 charge and discharge cycles. The probability of abnormal heating was measured by evaluating 20 rechargeable lithium-ion battery cells separately.

[0132] (Table 1)

[0133]

[0134] As indicated by the results shown in Table 1, the positive electrodes of Examples 1 to 5 prevented abnormal heating and improved the reliability of the rechargeable lithium battery cells.

[0135] While this disclosure has been described in conjunction with exemplary embodiments now considered to be practices, it should be understood that this disclosure is not limited to the disclosed embodiments. Rather, this disclosure includes various modifications and equivalent arrangements.

Claims

1. A positive electrode for a rechargeable lithium battery, the positive electrode comprising: Positive electrode current collector and positive electrode active material layer on the positive electrode current collector, The positive electrode is rectangular in shape, having a horizontal length longer than its vertical length, and having upper and lower sides of equal length. The positive electrode active material layer includes two trapezoidal patterns formed on the surface of the positive electrode active material. The two trapezoidal patterns have short sides that are adjacent to each other, and The long sides of the two trapezoidal patterns are adjacent to the upper and lower sides of the positive electrode active material layer, respectively.

2. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the two trapezoidal patterns are engraved in the positive electrode active material layer.

3. The positive electrode for a rechargeable lithium battery according to claim 2, wherein, Based on 100% of the thickness of the positive electrode active material layer, each of the two engraved trapezoidal patterns is formed at a depth of 1% to 50% starting from the surface of the positive electrode active material layer.

4. The positive electrode for a rechargeable lithium battery according to claim 2, wherein the width of each of the two engraved trapezoidal patterns is 0.5 μm to 10 μm.

5. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the ratio of the length of the short side to the length of the long side in each of the two trapezoidal patterns is 5:100 to 98:

100.

6. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the obtuse angle of the short side relative to each of the two trapezoidal patterns is 100° to 170°.

7. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the acute angle of the long side relative to each of the two trapezoidal patterns is 10° to 80°.

8. The positive electrode for a rechargeable lithium battery according to claim 1, wherein the positive electrode active material comprises at least one composite oxide containing at least one of lithium, cobalt, manganese and nickel.

9. A rechargeable lithium battery, comprising: The positive electrode according to any one of claims 1 to 8; negative electrode; and A diaphragm is located between the positive electrode and the negative electrode.

10. The rechargeable lithium battery of claim 9, wherein the positive electrode, the separator, and the negative electrode are stacked and wound together.

11. The rechargeable lithium battery of claim 9, wherein the rechargeable lithium battery further comprises an electrolyte impregnating the separator.

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