Rechargeable lithium battery

Abstract

Provided is a rechargeable lithium battery, including: a positive electrode; a negative electrode; a separator between the positive electrode and the negative electrode; an electrolyte including vinylene carbonate; and a case configured to house the positive electrode, the negative electrode, the separator, and the electrolyte, wherein a coated portion including lithium borate particles is included in at least a portion of the inside of the case.

Description

Technical Field

[0001] This disclosure relates to a rechargeable lithium battery that ensures overcharge safety. Background Technology

[0002] Portable information devices such as mobile phones, laptops, and smartphones, as well as electric vehicles, already use rechargeable lithium batteries with high energy density and portability as their power source. Recently, research has been actively underway to use rechargeable lithium batteries with high energy density as a power source or energy storage source for hybrid or electric vehicles.

[0003] However, with the commercialization of rechargeable lithium batteries in various fields, overcharging problems have emerged, where rechargeable lithium batteries are charged beyond a certain voltage value. When overcharged, the internal pressure and temperature of the rechargeable lithium battery increase due to chemical reactions in the battery's internal materials, potentially leading to accidents such as thermal runaway. To prevent these accidents, a system can be installed inside the battery to cut off the current when the internal pressure and temperature reach a predetermined value or higher.

[0004] However, when the internal temperature of the battery reaches a predetermined value or higher, a temperature sensing / current cut-off system has the problem of operating even at generally high temperatures of about 60°C or lower. Therefore, when the operating temperature is set high, the current cut-off system often delays operation, which limits its ability to ensure overcharge safety.

[0005] When the internal pressure of the battery reaches a predetermined value or higher, another type of temperature sensing / current cut-off system has the problem of the overcharge safety system failing to function properly because even after overcharging, the internal pressure of the battery cannot rise quickly enough, leading to accidents such as explosions after the battery is placed away. Therefore, there is a need for a rechargeable lithium battery system equipped with a safety device that operates rapidly during overcharging to ensure safety. Summary of the Invention

[0006] When overcharged beyond a certain voltage value, a rechargeable lithium battery is provided to ensure overcharge safety by quickly activating a safety device.

[0007] In one embodiment, the rechargeable lithium battery includes: a positive electrode; a negative electrode; a separator between the positive and negative electrodes; an electrolyte including vinylene carbonate; and a housing configured to house the positive electrode, the negative electrode, the separator, and the electrolyte, wherein at least a portion of the interior of the housing includes a coating containing lithium borate particles.

[0008] In the rechargeable lithium battery according to the embodiment, when a large amount of gas is generated in the battery and the pressure increases sufficiently during overcharging, the overcharge safety device operates rapidly to cut off the current, thereby ensuring overcharging safety. Furthermore, excellent performance can be achieved during operation. Attached Figure Description

[0009] Figure 1 This is a perspective view illustrating a rechargeable lithium battery according to an embodiment.

[0010] Figure 2 It is along Figure 1 A cross-sectional view of a rechargeable lithium battery taken from line II-II.

[0011] Figure 3 This is a graph showing the amount of gas generated per cell weight when the battery cells of Example 1 and Comparative Example 1 are charged with an overvoltage of 5V.

[0012] Figure 4 This is a graph evaluating the change in current of a single cell in Reference Examples A and B as the voltage increases at a constant rate.

[0013] <Explanation of Figure Markers>

[0014] 1: Rechargeable lithium battery; 10: Electrode assembly

[0015] 11: Negative electrode 12: Positive electrode

[0016] 11a: Coated portion of the negative electrode active material

[0017] 11b: Uncoated area of ​​the negative electrode

[0018] 12a: Positive electrode active material coating portion

[0019] 12b: Uncoated area of ​​the positive electrode

[0020] 13: Diaphragm 15: Shell

[0021] 20: Cover plate 21: Negative extreme polarity

[0022] 22: Positive end; 24: Vent hole

[0023] 25: Ventilation plate 25a: Notch

[0024] 27: Sealing plug; 29: Electrolyte inlet

[0025] 31: Insulating component; 40: Overcharge safety device

[0026] 41: Short-circuit connector 43: Short-circuit component

[0027] 51: Negative electrode lead connector

[0028] 52: Positive electrode lead connector

[0029] 61: Negative electrode insulating component

[0030] 62: Positive electrode insulating component

[0031] H1, H2: Terminal holes

[0032] 42: Short-circuit hole Detailed Implementation

[0033] Specific embodiments will be described in detail below so that those skilled in the art can readily implement them. However, this disclosure may be embodied in many different forms and is not to be construed as limited to the exemplary embodiments set forth herein.

[0034] The terminology used herein is for describing exemplary embodiments only and is not intended to limit this disclosure. Unless otherwise clearly indicated below, singular expressions include plural expressions.

[0035] As used herein, "any combination thereof" means mixtures, laminates, complexes, copolymers, alloys, blends, reaction products, etc. of the components.

[0036] Here it will be understood that terms such as “comprises,” “includes,” or “have” are intended to indicate the presence of specific features, quantities, steps, elements, or any combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, quantities, steps, elements, or any combination thereof.

[0037] In the accompanying drawings, for clarity, the thicknesses of layers, films, panels, regions, etc., are enlarged, and the same reference numerals denote the same elements throughout the specification. It will be understood that when an element such as a layer, film, region, or substrate is referred to as "on" another element, the element may be directly on the other element, or an intervening element may be present. In contrast, when an element is referred to as "directly on" another element, no intervening element is present.

[0038] Furthermore, the term "layer" here includes not only the shape formed on the entire surface when viewed from a plan view, but also the shape formed on a portion of the surface.

[0039] Additionally, the average particle size can be measured using methods well known to those skilled in the art, for example, by a particle size analyzer, or by transmission electron microscopy or scanning electron microscopy. Alternatively, the average particle size value can be obtained by measuring using a dynamic light scattering method, performing data analysis, counting the number of particles in each particle size range, and thereby calculating. Unless otherwise specified, the average particle size (D50) may refer to the diameter of particles that constitute 50% of the total volume in the particle size distribution.

[0040] Here, "or" is not interpreted as exclusive. For example, "A or B" can be interpreted as including A, B, A+B, etc.

[0041] In one embodiment, the rechargeable lithium battery includes a positive electrode; a negative electrode; a separator between the positive and negative electrodes; an electrolyte including vinylene carbonate; and a housing configured to house the positive electrode, negative electrode, separator, and electrolyte, wherein at least a portion of the interior of the housing includes a coating containing lithium borate particles.

[0042] When this rechargeable lithium battery is charged at its rated voltage or an abnormal voltage higher (e.g., in the range of approximately 4.5V to approximately 5.0V, such as approximately 4.7V or higher, or approximately 4.8V or higher), the battery internally generates a large amount of gas that causes the overcharge safety device to quickly activate, cutting off current and heat transfer, thereby preventing accidents such as fires. Conversely, at voltages below the rated voltage, since no additional gas is generated, the battery can resume normal operation and exhibit excellent performance (such as cycle life characteristics).

[0043] It has been reported that the cycle life of batteries is improved when additives such as vinylene carbonate are used in the electrolyte. However, these electrolyte additives can reduce the amount of gas generated during overcharging. Therefore, since safety devices may fail to operate because the internal pressure of the casing does not rise quickly enough, problems such as thermal runaway may occur after continued overcharging.

[0044] Conversely, in this embodiment, because vinylene carbonate is added to the electrolyte and a coating comprising lithium borate is simultaneously applied to the casing, no gas is generated below the rated voltage, cycle life characteristics are improved, and a large amount of gas is generated only when charging at the rated voltage or higher (e.g., 4.5V or higher) to enable rapid operation of safety devices, ensure overcharge safety of the rechargeable lithium battery, and improve battery performance (such as cycle life characteristics). It is understood that within the overvoltage range, vinylene carbonate in the electrolyte and lithium borate in the coating cause a chemical reaction, thereby generating a large amount of gas. For example, when a rechargeable lithium battery is charged with an overvoltage greater than or equal to about 5.0V, the amount of gas generated per battery weight may be greater than or equal to about 1.0 cc / g.

[0045] Coated portion inside the casing

[0046] At least a portion of the coating inside the casing comprises lithium borate. Lithium borate can be represented as lithium boron oxide, for example, LiBO2, Li3B7O. 12 Li6B4O9, Li3B 11 O 18 Li₂B₄O₇, Li₃BO₃, Li₈B₆O 13 Li5B3O7, Li4B2O5, Li 10 B4O 11 Li8B2O7 or any combination thereof. This lithium borate compound is understood to not affect battery operation during normal charging periods, but reacts with vinylene carbonate in the electrolyte during overvoltage charging at approximately 4.5V or higher, thus generating a large amount of gas.

[0047] Lithium borates can be compounds with a redox potential of about 4.5V or higher. Examples of lithium borates with a redox potential of about 4.5V or higher include, for example, LiBO₂ and Li₃B₇O₂. 12 Li6B4O9, Li3B 11 O 18 Li₂B₄O₇ or any combination thereof. These compounds can exhibit high phase stability even in overvoltage ranges of about 4.5V or higher. For example, lithium borates can include LiBO₂.

[0048] Table 1 below shows the Li3B7O content in lithium borate. 12 Li6B4O9, Li3B 11 O 18The redox potentials and redox reaction equations for Li₂B₄O₇ and LiBO₂ are shown in Table 1. Referring to Table 1, the compounds typically have redox potentials of about 4.5 V or higher (e.g., greater than or equal to about 5.0 V, or greater than or equal to about 5.1 V) above the battery's operating potential. Therefore, the compound can exhibit high phase stability over the overvoltage range and does not cause side reactions during overvoltage, but it accelerates gas generation through its reaction with vinylene carbonate in the electrolyte.

[0049] Table 1

[0050]

[0051]

[0052] In the coated portion, lithium borate may be present in particulate form. Here, the lithium borate particles may have an average particle size (D50) of about 10 μm or smaller (e.g., about 1 μm to about 10 μm, about 2 μm to about 9 μm, about 3 μm to about 8 μm, or about 4 μm to about 7 μm). When the lithium borate particles have an average particle size within these ranges, the lithium borate particles are advantageous for processing, improve the durability and cycle life of the coated portion, and react well with the electrolyte during overcharging, thereby generating a large amount of gas. The average particle size (D50) can be measured using a particle size analyzer and refers to the diameter of the particles that constitute 50% by volume of the cumulative volume in the particle distribution.

[0053] The coating portion may be disposed in at least a portion of the interior of the housing, wherein this portion of the housing is in contact with the electrolyte. Therefore, the lithium borate in the coating portion comes into contact with the vinylene carbonate and other components in the electrolyte, thereby initiating a chemical reaction within the overvoltage range.

[0054] The coating portion can be any part inside the housing that comes into contact with the electrolyte, without any particular limitation. For example, the coating portion may be located on at least one of the inner walls of the housing and the inner walls of the cover plate.

[0055] electrolyte

[0056] The electrolyte according to the embodiment includes vinylene carbonate (VC). It is believed that the vinylene carbonate in the electrolyte does not generate gas within the normal voltage range, which helps to improve the cycle life characteristics of the battery, and only generates a large amount of gas through contact with the coated portion during overvoltage charging.

[0057] Based on the total weight of the electrolyte, the content of vinylene carbonate can be from about 0.1 wt% to about 5 wt% (e.g., about 0.2 wt% to about 4 wt%, about 0.5 wt% to about 3 wt%, or about 0.8 wt% to about 2 wt%). When vinylene carbonate is included in the above range, safety can be ensured by increasing the amount of gas generated during overcharging while improving the general performance of the battery, such as cycle life characteristics.

[0058] In addition to vinylene carbonate, the electrolyte may further include non-aqueous organic solvents and lithium salts.

[0059] Here, based on the total weight of 100 parts by weight of non-aqueous organic solvent and lithium salt, the content of vinylene carbonate may be about 0.1 parts by weight to about 5 parts by weight, about 0.3 parts by weight to about 4 parts by weight, about 0.5 parts by weight to about 3 parts by weight, or about 0.8 parts by weight to about 2 parts by weight.

[0060] Non-aqueous organic solvents are used as mediators for transporting ions involved in the electrochemical reactions of a battery. Non-aqueous organic solvents can be carbonate solvents, ester solvents, ether solvents, ketone solvents, alcohol solvents, or aprotic solvents. Carbonate solvents can 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), butyl carbonate (BC), etc. Ester solvents can include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, mevalonolactone, caprolactone, etc. Ether solvents can include dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. Ketone solvents can include cyclohexanone, etc. In addition, alcohol solvents can be ethanol, isopropanol, etc., and aprotic solvents can be nitriles (such as R-CN, where R is a C2 to C20 straight chain, branched chain or cyclic hydrocarbon group, and may include double bonds, aromatic rings or ether bonds), amides (such as dimethylformamide), dioxolane (such as 1,3-dioxolane), sulfolane, etc.

[0061] Non-aqueous organic solvents can be used alone or in mixtures. When non-aqueous organic solvents are used in mixtures of two or more, the mixing ratio can be controlled according to the desired battery performance.

[0062] Alternatively, in the case of carbonate solvents, a mixture of cyclic carbonates and chain carbonates can be used. In this case, when cyclic carbonates and chain carbonates are mixed in a volume ratio of about 1:1 to about 1:9, the electrolyte exhibits excellent performance.

[0063] In addition to carbonate solvents, non-aqueous organic solvents may further include aromatic hydrocarbon organic solvents. In this case, carbonate solvents and aromatic hydrocarbon organic solvents can be mixed in a volume ratio of about 1:1 to about 30:1.

[0064] As an aromatic hydrocarbon organic solvent, aromatic hydrocarbon compounds represented by chemical formula I can be used.

[0065] [Chemical Formula I]

[0066]

[0067] In chemical formula I, R 4 ~R 9 They may be the same or different, and are selected from hydrogen, halogens, C1-C10 alkyl groups, C1-C10 haloalkyl groups and any combination thereof.

[0068] Specific examples of aromatic hydrocarbon organic solvents may be selected from benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, 1,2,3-trifluorobenzene, 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2,4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4-triiodobenzene, toluene, and fluorotoluene. 2,3-Difluorotoluene, 2,4-Difluorotoluene, 2,5-Difluorotoluene, 2,3,4-Trifluorotoluene, 2,3,5-Trifluorotoluene, Chlorotoluene, 2,3-Dichlorotoluene, 2,4-Dichlorotoluene, 2,5-Dichlorotoluene, 2,3,4-Trichlorotoluene, 2,3,5-Trichlorotoluene, Iodotoluene, 2,3-Diiodotoluene, 2,4-Diiodotoluene, 2,5-Diiodotoluene, 2,3,4-Triiodotoluene, 2,3,5-Triiodotoluene, Xylene, and any combination thereof.

[0069] In addition to the aforementioned vinylene carbonate, the electrolyte may further include ethylene carbonate compounds of formula II to improve the cycle life of the battery.

[0070] [Chemical Formula II]

[0071]

[0072] In chemical formula II, R 10 and R 11 The same or different, and selected from hydrogen, halogen, cyano, nitro and fluorinated C1 to C5 alkyl groups, provided that R 10 and R 11 At least one of them is selected from halogen, cyano, nitro and fluorinated C1-C5 alkyl groups, but R 10 and R 11 None of them are hydrogen.

[0073] Examples of ethylene carbonate compounds may be difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, or fluoroethylene carbonate. The amount of additives (such as ethylene carbonate compounds) used to improve cycle life may be used within appropriate limits.

[0074] Lithium salts dissolved in non-aqueous organic solvents provide lithium ions in the battery, enabling rechargeable lithium batteries to perform basic operations and improving the transport of lithium ions between the positive and negative electrodes.

[0075] Examples of lithium salts include at least one carrier salt selected from the following: LiPF6, LiBF4, LiSbF6, LiAsF6, LiN(SO2C2F5)2, Li(CF3SO2)2N, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiN(C x F 2x+1 SO2)(C y F 2y+1 SO2 (where x and y are natural numbers, for example, integers ranging from 1 to 20), lithium difluoro(bis(oxalate)phosphate), LiCl, LiI, LiB(C2O4)2 (lithium bis(oxalate)borate; LiBOB) and lithium difluoro(oxalate)borate (LiDFOB).

[0076] Lithium salts can be used at concentrations ranging from approximately 0.1 M to approximately 2.0 M. When lithium salts are used within the above concentration range, the electrolyte exhibits excellent performance and lithium-ion mobility due to optimal electrolyte conductivity and viscosity.

[0077] positive electrode

[0078] The positive electrode for a rechargeable lithium battery according to an embodiment may include a current collector and a layer of positive electrode active material on the current collector. The positive electrode active material layer may include a positive electrode active material and may further include a binder and / or a conductive material.

[0079] The positive electrode active material can be a compound capable of inserting and deintercalating lithium (lithium-intercalating compound). Examples of positive electrode active materials can be compounds represented by one of the following chemical formulas:

[0080] Li a A 1-b X b D2(0.90≤a≤1.8, 0≤b≤0.5);

[0081] 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);

[0082] Li a HAVE BEEN 1-b X b O 2-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);

[0083] Li a HAVE BEEN 2-b X b O 4-c D c (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05);

[0084] Li a Ni 1-b-c Co b X c D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.5,0<α≤2);

[0085] Li a Ni 1-b-c Co b X c O 2-α T α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0<α<2);

[0086] Li a Ni 1-b-c Co b X c O 2-α T2(0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0<α<2);

[0087] Li a Ni 1-b-c Mr b X c D α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0<α≤2);

[0088] Li a Ni 1-b-c Mrb X c O 2-α T α (0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0<α<2);

[0089] The a Nor 1-b-c Mn b X c O 2-α T2(0.90≤a≤1.8,0≤b≤0.5,0≤c≤0.05,0<α<2);

[0090] The a Nor b E c G d O2(0.90≤a≤1.8,0≤b≤0.9,0≤c≤0.5,0.001≤d≤0.1);

[0091] The a Nor b Co c Mn d GeO2(0.90≤a≤1.8,0≤b≤0.9,0≤c≤0.5,0≤d≤0.5,0.001≤e≤0.1);

[0092] The a NiG b O2(0.90≤a≤1.8,0.001≤b≤0.1);

[0093] The a CoG b O2(0.90≤a≤1.8,0.001≤b≤0.1);

[0094] The a Mn 1-b G b O2(0.90≤a≤1.8,0.001≤b≤0.1);

[0095] The a Mn2G b O4(0.90≤a≤1.8,0.001≤b≤0.1);

[0096] The a Mn 1-g G g PO4(0.90≤a≤1.8,0≤g≤0.5);

[0097] QO2;QS2;LiQS2;

[0098] V₂O₅; LiV₂O₅;

[0099] LiZO2;

[0100] LiNiVO4;

[0101] Li (3-f) J2(PO4)3(0≤f≤2);

[0102] Li (3-f) Fe2(PO4)3 (0≤f≤2);

[0103] Li a FePO4 (0.90≤a≤1.8).

[0104] In the chemical formula, A is selected from Ni, Co, Mn and any combination thereof; X is selected from Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements and any combination thereof; D is selected from O, F, S, P and any combination thereof; E is selected from Co, Mn and any combination thereof; T is selected from F, S, P and any combination thereof; G is selected from Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V and any combination thereof; Q is selected from Ti, Mo, Mn and any combination thereof; Z is selected from Cr, V, Fe, Sc, Y and any combination thereof; and J is selected from V, Cr, Mn, Co, Ni, Cu and any combination thereof.

[0105] For example, the positive electrode active material may include lithium-nickel composite oxides. Lithium-nickel composite oxides may be represented by chemical formula 1.

[0106] [Chemical Formula 1]

[0107] Li a1 Ni x1 M 1 y1 M 2 1-x1-y1 O 2-z X z

[0108] In chemical formula 1, 0.9 ≤ a1 ≤ 1.8, 0.3 ≤ x1 ≤ 1, 0 ≤ y1 ≤ 0.7, and 0 ≤ z ≤ 0.1, M 1 and M 2 Each of them is independently Al, B, Ba, Ca, Ce, Co, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, Zr or any combination thereof, and X is F, P, S or any combination thereof.

[0109] In Chemical Formula 1, 0.4 ≤ x1 ≤ 1 and 0 ≤ y1 ≤ 0.6, 0.5 ≤ x1 ≤ 1 and 0 ≤ y1 ≤ 0.5, 0.6 ≤ x1 ≤ 1 and 0 ≤ y1 ≤ 0.4, or 0.7 ≤ x1 ≤ 1 and 0 ≤ y1 ≤ 0.3, 0.8 ≤ x1 ≤ 1 and 0 ≤ y1 ≤ 0.2, or 0.9 ≤ x1 ≤ 1 and 0 ≤ y1 ≤ 0.1.

[0110] The lithium nickel-based composite oxide can be represented, for example, by Chemical Formula 2.

[0111] [Chemical Formula 2]

[0112] Li a2 Ni x2 Co y2 M 3 1-x2-y2 O 2-z X z

[0113] In Chemical Formula 2, 0.9 ≤ a2 ≤ 1.8, 0.3 ≤ x2 < 1, 0 < y2 ≤ 0.7, and 0 ≤ z ≤ 0.1, M 3 is Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mn, Mo, Nb, Si, Sr, Ti, V, W, Zr, or any combination thereof, and X is F, P, S, or any combination thereof.

[0114] In Chemical Formula 2, 0.3 ≤ x2 ≤ 0.99 and 0.01 ≤ y2 ≤ 0.7, 0.4 ≤ x2 ≤ 0.99 and 0.01 ≤ y2 ≤ 0.6, 0.5 ≤ x2 ≤ 0.99 and 0.01 ≤ y2 ≤ 0.5, 0.6 ≤ x2 ≤ 0.99 and 0.01 ≤ y2 ≤ 0.4, 0.7 ≤ x2 ≤ 0.99 and 0.01 ≤ y2 ≤ 0.3, 0.8 ≤ x2 ≤ 0.99 and 0.01 ≤ y2 ≤ 0.2, or 0.9 ≤ x2 ≤ 0.99 and 0.01 ≤ y2 ≤ 0.1.

[0115] The positive electrode active material may have a coating on the surface of the above compound. The coating may include at least one coating element compound selected from oxides of coating elements, hydroxides of coating elements, hydroxyoxides of coating elements, oxycarbonates of coating elements, and hydroxycarbonates of coating elements. The compound used for the coating may be amorphous or crystalline. The coating elements included in the coating may include Al, As, B, Ca, Co, Fe, Ga, Ge, K, Mg, Na, Si, Sn, Ti, V, Zr, or any combination thereof. The coating formation process may be dry or wet. For example, spraying, dipping, etc. may be used.

[0116] For example, the positive electrode active material may include particles comprising lithium transition metal complex oxides and a boron coating on the surface of the particles. Alternatively, the positive electrode active material may include secondary particles comprising a plurality of primary particles aggregated from lithium transition metal complex oxides and a boron coating on the surface of the secondary particles. In this case, the effect of generating a large amount of gas during overvoltage charging can be increased, and overcharge safety can be further improved. For example, during overvoltage charging at 4.7V or higher, the boron coating in the positive electrode active material can contribute to the generation of a large amount of gas by reacting with vinylene carbonate in the electrolyte.

[0117] The boron coating can be uniformly applied to the surface of the secondary particles. The boron coating may include lithium borate, and lithium borate may be represented as lithium boron oxide. Lithium borate may include, for example, LiBO2, Li3B7O. 12 Li6B4O9, Li3B 11 O 18 Li₂B₄O₇, Li₃BO₃, Li₈B₆O 13 Li5B3O7, Li4B2O5, Li 10 B4O 11 Li8B2O7 or any combination thereof. For example, boron-coated lithium borates may include LiBO2.

[0118] Based on the total weight of the positive electrode active material, the content of lithium borate in the boron coating can be from about 0.01 wt% to about 3 wt% (e.g., about 0.01 wt% to about 2 wt%, about 0.01 wt% to about 1 wt%, or about 0.01 wt% to about 0.5 wt%). In this case, the boron coating does not act as a resistor, but rather increases the structural stability of the positive electrode active material to improve cycle life characteristics and simultaneously improve overcharge safety.

[0119] In addition to the boron coating, the positive electrode active material may further include a boron-doped layer inside the primary particles exposed on the surface of the secondary particles. The boron-doped layer can be said to be disposed inside the secondary particles. The primary particles exposed on the surface of the secondary particles can refer to the primary particles in the outermost portion of the secondary particles. For example, the boron-doped layer can be disposed at a depth of approximately 10 nm from the outer surface of the primary particles exposed on the surface of the secondary particles. If the distance from the outer surface of the primary particles exposed on the surface of the secondary particles is 0 nm, the boron-doped layer can be said to exist at a depth of approximately 0 nm to approximately 10 nm from that surface. In other words, the boron-doped layer can exist at a depth of approximately 10 nm from the surface of the secondary particles. When the distance from the surface of the secondary particles is approximately 0 nm, the boron-doped layer can exist at a depth of approximately 0 nm to approximately 10 nm from that surface.

[0120] For example, the boron-doped layer may exist at depths of approximately 9 nm, 8 nm, 7 nm, 6 nm, 5 nm, 4 nm, 3 nm, or 2.5 nm from the outer surface of the primary particles exposed to the surface of the secondary particles. This boron-doped layer may differ from the boron coating and the grain boundary boron coating portion described later, thereby contributing to the structural stability of the positive electrode active material.

[0121] On the other hand, in addition to the aforementioned boron coating and boron doping layer, the positive electrode active material may further include a grain boundary boron coating portion disposed on the surface of the primary particles within the secondary particles and comprising lithium borate. This grain boundary boron coating portion is not present on the surface of the secondary particles, but rather within the secondary particles, and may be coated along the interface of the primary particles. Here, the internal portion of the secondary particles means the entire interior except for the surface (e.g., the entire interior from the outer surface to a depth of approximately 2 μm), or the portion that distilled water does not reach when the secondary particles of the positive electrode active material are washed with distilled water.

[0122] According to the embodiment, the weight of the boron coating is greater than the weight of the grain boundary boron coating portion. For example, based on the total amount of the boron coating and the grain boundary boron coating portion, the content of the grain boundary boron coating portion can be about 2 wt% to about 30 wt% (specifically, about 3 wt% to about 25 wt% or about 5 wt% to about 20 wt%), and the content of the boron coating can be about 70 wt% to about 98 wt%, about 75 wt% to about 97 wt%, about 80 wt% to about 95 wt%, etc. For example, the weight ratio of the boron coating and the grain boundary boron coating portion can be about 70:30 to about 98:2 (e.g., about 75:25 to about 97:3 or about 80:20 to about 95:5). When the boron coating and the grain boundary boron coating portion are included in the above content ratio, boron may not act as a resistor, but rather improve performance, while improving the capacity characteristics and cycle life characteristics of the rechargeable lithium battery.

[0123] Based on the total weight of the positive electrode active material, the content of lithium borate in the boron coating portion at the grain boundaries can be from about 0.001 wt% to about 0.05 wt% (e.g., about 0.001 wt% to about 0.04 wt%, about 0.002 wt% to about 0.03 wt%, or about 0.003 wt% to about 0.02 wt%), but is not limited thereto.

[0124] In addition to the aforementioned positive electrode active material, the positive electrode active material layer may further include adhesives and / or conductive materials.

[0125] The adhesive improves the adhesion properties between the positive electrode active material particles and between them and the current collector. Examples of adhesives 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, acrylated styrene-butadiene, epoxy resin, nylon, etc.

[0126] Based on the total weight of the positive electrode active material layer, the content of the binder in the positive electrode active material layer can be approximately 1 wt% to approximately 5 wt%.

[0127] Conductive materials are included to provide electrode conductivity. Any electrically conductive material can be used as a conductive material unless it causes a chemical change. Examples of conductive materials may 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 metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers (such as polyphenylene derivatives); or mixtures thereof.

[0128] Based on the total weight of the positive electrode active material layer, the content of conductive material in the positive electrode active material layer can be approximately 1 wt% to approximately 5 wt%.

[0129] Aluminum foil can be used as a current collector, but is not limited to this.

[0130] negative electrode

[0131] The negative electrode for a rechargeable lithium battery may include, for example, a current collector and a layer of negative electrode active material on the current collector. The negative electrode active material layer may include a negative electrode active material and may further include a binder and / or a conductive material.

[0132] The active material of the negative electrode may include materials that can reversibly insert / deintercalate lithium ions, lithium metal, lithium metal alloys, materials that can be doped / dedoped with lithium, or transition metal oxides.

[0133] Materials capable of reversibly inserting / deintercalating lithium ions can include, for example, crystalline carbon, amorphous carbon, or any combination thereof as active materials for carbon-based negative electrodes. Crystalline carbon can be amorphous or in the form of flakes, sheets, spheres, or fibers, such as natural or artificial graphite. Amorphous carbon can be soft carbon, hard carbon, mesophase pitch carbonization products, calcined coke, etc.

[0134] Lithium metal alloys include alloys of lithium and metals selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn.

[0135] The substance 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 (where Q is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element other than Si, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, or any combination thereof), and the Sn-based negative electrode active material may include Sn, SnO2, a Sn-R alloy (where R is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element other than Sn, a Group 15 element, a Group 16 element, a transition metal, a rare earth element, or any combination thereof). At least one of these substances may be mixed with SiO2. The elements Q and R may be selected from 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 any combination thereof.

[0136] The silicon-carbon composite may be, for example, a silicon-carbon composite including a core containing crystalline carbon and silicon particles and an amorphous carbon coating provided on the surface of the core. The crystalline carbon may be artificial graphite, natural graphite, or any combination thereof. The amorphous carbon precursor may be coal tar pitch, mesophase pitch, petroleum pitch, coal oil, petroleum heavy oil, or a polymer resin (such as phenolic resin, furan resin, or polyimide resin). In this case, based on the total weight of the silicon-carbon composite, the content of silicon may be about 10 wt% to about 50 wt%. Additionally, based on the total weight of the silicon-carbon composite, the content of crystalline carbon may be about 10 wt% to about 70 wt%, and based on the total weight of the silicon-carbon composite, the content of amorphous carbon may be about 20 wt% to about 40 wt%. Additionally, the thickness of the amorphous carbon coating may be about 5 nm to about 100 nm. The average particle size (D50) of the silicon particles may be about 10 nm to about 20 μm. The average particle size (D50) of the silicon particles may preferably be about 10 nm to about 200 nm. The silicon particles may exist in an oxidized form, and in this case, the atomic content ratio of Si:O in the silicon particles indicating the degree of oxidation may be about 99:1 to about 33:67. The silicon particles may be SiO x particles, and in this case, SiO x the range of x may be greater than about 0 and less than about 2. As used herein, when no other definition is provided, the average particle size (D50) indicates the diameter of the particles in the particle distribution where the cumulative volume is about 50 volume%.

[0137] Si-based or Sn-based negative electrode active materials can be mixed with carbon-based negative electrode active materials. When Si-based or Sn-based negative electrode active materials are mixed with carbon-based negative electrode active materials, the mixing ratio can be approximately 1:99 to approximately 90:10 by weight.

[0138] In the negative electrode active material layer, the content of the negative electrode active material can be approximately 95 wt% to approximately 99 wt%, based on the total weight of the negative electrode active material layer.

[0139] In an embodiment, the negative electrode active material layer may further include an adhesive, and optionally further include a conductive material. Based on the total weight of the negative electrode active material layer, the adhesive content in the negative electrode active material layer may be from about 1 wt% to about 5 wt%. Alternatively, when further including a conductive material, the negative electrode active material layer may include about 90 wt% to about 98 wt% of the negative electrode active material, about 1 wt% to about 5 wt% of the adhesive, and about 1 wt% to about 5 wt% of the conductive material.

[0140] Adhesives are used to ensure good adhesion between particles of the negative electrode active material, and also to adhere the negative electrode active material to the current collector. Adhesives can be water-insoluble adhesives, water-soluble adhesives, or any combination thereof.

[0141] Examples of water-insoluble adhesives include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, ethylene propylene copolymers, polystyrene, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyimide, or any combination thereof.

[0142] Water-soluble adhesives may include rubber adhesives or polymeric resin adhesives. Rubber adhesives may be selected from styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile-butadiene rubber, acrylic rubber, butyl rubber, fluororubber, and any combination thereof. Polymeric resin adhesives may be selected from polyethylene oxide, polyvinylpyrrolidone, polyepoxychloropropane, polyphosphazene, polyacrylonitrile, ethylene-propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and any combination thereof.

[0143] When a water-soluble binder is used as a negative electrode binder, it may further include a cellulose-based compound as a thickener capable of imparting viscosity. One or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, and their alkali metal salts may be mixed and used as the cellulose-based compound. Na, K, or Li may be used as the alkali metal. Based on 100 parts by weight of the negative electrode active material, the amount of this thickener may be from about 0.1 parts by weight to about 3 parts by weight.

[0144] Conductive materials are included to provide electrode conductivity. Any electrically conductive material can be used as a conductive material unless it causes a chemical change. 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.

[0145] The current collector may include one selected from copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, polymer substrate coated with conductive metal, and any combination thereof.

[0146] diaphragm

[0147] The separator separates the positive and negative electrodes and provides a channel for lithium-ion transport, and can be any commonly used separator in lithium-ion batteries. In other words, the separator can have low resistance to ion transport and excellent impregnation with electrolytes. For example, the separator material can be selected from glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene, or any combination thereof. The separator can be in the form of a non-woven or woven fabric. For example, in lithium-ion batteries, polyolefin polymer separators (such as polyethylene separators and polypropylene separators) can be used primarily. To ensure heat resistance or mechanical strength, coated separators including ceramic components or polymer materials can be used. Optionally, the separator can have a single-layer or multi-layer structure.

[0148] Rechargeable lithium batteries

[0149] Rechargeable lithium batteries can be classified into lithium-ion batteries, lithium-ion polymer batteries, lithium polymer batteries, or all-solid-state batteries based on the presence or absence of a separator and the type of electrolyte. Based on shape, rechargeable lithium batteries can be categorized into cylindrical, square, coin-shaped, and pouch-shaped batteries, among others.

[0150] Figure 1 This is a perspective view of a rechargeable lithium battery according to an embodiment, and Figure 2 It is along Figure 1 A sectional view taken along line II-II. (Refer to...) Figure 1 and Figure 2 The rechargeable lithium battery 1 includes an electrode assembly 10 for charging and discharging current, a housing 15 for housing the electrode assembly 10, and a cover 20 coupled to an opening in the housing 15. The rechargeable lithium battery 1 may further include electrode terminals (negative and positive terminals) 21, 22 mounted on the cover 20, and may further include an overcharge safety device 40.

[0151] The electrode assembly 10 is formed by providing a negative electrode 11 and a positive electrode 12 on two surfaces of a diaphragm 13, which is an electrically insulating material, and winding the negative electrode 11, the diaphragm 13, and the positive electrode 12 into a wound state. Although not shown, the electrode assembly can be formed as a stacked type in which the negative electrode, the diaphragm, and the positive electrode are stacked. The negative electrode 11 and the positive electrode 12 each include a coated portion 11a, 12a (also referred to as negative electrode active material coated portion 11a and positive electrode active material coated portion 12a, respectively) coated with an active material on a current collector of a metal plate, and a respective uncoated region 11b, 12b (also referred to as negative electrode uncoated region 11b and positive electrode uncoated region 12b, respectively) exposed to the current collector without being coated with an active material. The uncoated region 11b of the negative electrode 11 is formed at one end of the wound negative electrode 11. The uncoated region 12b of the positive electrode 12 is formed at one end of the wound positive electrode 12. Uncoated areas 11b and 12b are respectively located at both ends of the electrode assembly 10.

[0152] A cover plate 20 is installed in the opening of the housing 15 and closes and seals the housing 15. For example, the housing 15 and the cover plate 20 may be formed of aluminum and welded together. Additionally, the cover plate 20 may have a vent 24 and terminal holes H1, H2. The vent 24 can be represented as a vent port through which internal gases can be released when the internal pressure of the housing 15 increases drastically due to overcharging, accidents, etc. The vent 24 can be closed and sealed by a vent plate 25, and when the internal pressure of the housing 15 exceeds a predetermined pressure (i.e., reaches excessive pressure), the vent plate 25 is cut off to open the vent 24. The vent plate 25 may have a notch 25a that causes the cut-off.

[0153] Negative terminal 21 and positive terminal 22 are respectively installed in terminal holes H1 and H2 of cover plate 20 and electrically connected to electrode assembly 10. In other words, negative terminal 21 and positive terminal 22 are electrically connected to negative electrode 11 and positive electrode 12 of electrode assembly 10, respectively. Therefore, electrode assembly 10 is led out from housing 15 through negative terminal 21 and positive terminal 22. Negative electrode insulating member 61 and positive electrode insulating member 62 are respectively installed between negative electrode lead connector 51 and cover plate 20 and between positive electrode lead connector 52 and cover plate 20, so as to electrically insulate negative electrode lead connector 51 and positive electrode lead connector 52 from cover plate 20.

[0154] An electrolyte inlet 29 is formed in the cover plate 20 to allow electrolyte to be injected into the interior of the housing 15 after the cover plate 20 is attached to the housing 15. After the electrolyte is injected, the electrolyte inlet 29 is sealed with a sealing plug 27.

[0155] On the other hand, the overcharge safety device 40 is a device that blocks the current by implementing an external short circuit when the internal pressure of the housing 15 increases due to the gas generated by overcharging.

[0156] Overcharge safety devices can be, for example, devices that cause a short circuit when the internal pressure of the housing increases (i.e., pressure-response short-circuit devices), or pressure-response circuit disconnection devices that cause an open circuit when the internal pressure of the housing increases.

[0157] A pressure-responsive circuit disconnect device is a current-interrupting device that blocks charging when the internal pressure inside the casing becomes greater than or equal to a predetermined value (e.g., due to problems such as the battery temperature or voltage becoming greater than or equal to a predetermined value). The pressure-responsive circuit disconnect device can be configured, for example, to cause a metal plate of a certain type on the outer wall of the casing to expand upwards when the internal pressure of the battery rises excessively, thereby blocking both external and internal circuitry. Because gas is rapidly generated during overcharging, the circuit disconnect device operates quickly, and the rechargeable lithium battery according to the embodiment can stop charging, thus effectively preventing overcharging.

[0158] When the gas pressure inside the battery exceeds a predetermined value due to issues such as the battery temperature or voltage exceeding a predetermined value, the pressure-responsive short-circuit device can cause an internal short circuit and discharge the electrodes. For example, the pressure-responsive short-circuit device can be configured to create a short circuit between the positive and negative electrodes when the internal pressure of the casing excessively increases, causing a type of metal plate attached to the outer wall of the casing to expand upwards and contact components with different potentials. The rechargeable lithium battery according to the embodiment effectively prevents overcharging because the pressure-responsive short-circuit device operates rapidly and the electrode plates discharge due to the rapid generation of gas in the battery during overvoltage charging. When the pressure-responsive short-circuit device is applied, the rechargeable lithium battery may further include thermal circuit breaker (TCO) devices (such as fuses), positive electrode thermal circuit breakers (PTCs), bimetallic strips, circuit breakers, etc., to control the heat generated during discharge.

[0159] exist Figure 1 and Figure 2 In this design, the overcharge safety device 40 can be considered a type of pressure-response short-circuit device. The overcharge safety device 40 includes short-circuit terminals 41 and short-circuit members 43 that are spaced apart or short-circuited from each other. The short-circuit terminals 41 are electrically connected to the negative terminal 21 and are disposed outside the cover plate 20. An insulating member 31 is located between the short-circuit terminals 41 and the cover plate 20. The insulating member 31 is installed between the short-circuit terminals 41 and the cover plate 20 to electrically insulate the short-circuit terminals 41 and the cover plate 20. That is, the cover plate 20 is electrically insulated from the negative terminal 21.

[0160] A short-circuit member 43 is installed in a short-circuit hole 42 formed in the cover plate 20. A short-circuit terminal 41 is connected to the negative terminal 21 and extends along the outer side of the short-circuit member 43. Therefore, the short-circuit terminal 41 and the short-circuit member 43 correspond to each other in the short-circuit hole 42, face each other, and remain spaced apart. When the internal pressure of the housing 15 increases due to overcharging or the like and reaches excessive pressure, the bending of the short-circuit member 43 reverses, creating a short circuit. For example, in the overcharge safety device 40, when the internal pressure of the housing 15 exceeds 10 kgf / cm², a short circuit is formed. 2 When this occurs, the short-circuit component 43 reverses direction, causing an external short circuit. The overcharge safety device is activated when the internal pressure of the housing 15 is greater than or equal to 7 kgf / cm². 2 Time operation.

[0161] On the other hand, the coating portion, including the aforementioned lithium borate particles, can be provided without limitation as long as it can come into contact with the electrolyte inside the casing. For example, the coating portion can be provided with... Figure 2 At least one of the inner wall surfaces of the housing 15 and the cover plate 20. In this case, when charging is performed with an overvoltage of about 4.5V to about 5.0V (e.g., about 4.7V or higher), a large amount of gas is generated due to the reaction between the coated portion and the vinylene carbonate in the electrolyte, and the current is cut off by an overcharge safety device or the like, preventing accidents such as explosions.

[0162] Embodiments and comparative examples of the present invention are described below. However, it should be understood that these embodiments are for illustrative purposes and should not be construed as limiting the invention.

[0163] Example 1

[0164] 1. Manufacturing of the positive electrode

[0165] 96 wt% LiNi was used as the positive electrode active material. 0.945 Co 0.04 Al 0.015 O2, 2 wt% polyvinylidene fluoride, 2 wt% carbon nanotubes, and N-methylpyrrolidone as a solvent are mixed in a mixer to prepare a slurry for forming the active material layer of the positive electrode. The slurry for forming the active material layer of the positive electrode is coated onto aluminum foil to form an electrode plate, which is then rolled and dried to manufacture the positive electrode.

[0166] 2. Manufacturing of the negative electrode

[0167] A negative electrode active material slurry was prepared by mixing 97.3 wt% graphite, 0.5 wt% acetylene black, 0.9 wt% carboxymethyl cellulose, and 1.3 wt% styrene-butadiene rubber in an aqueous solvent. The negative electrode active material slurry was coated onto copper foil, then dried and rolled to manufacture the negative electrode.

[0168] 3. Manufacturing of individual battery cells

[0169] LiBO2 particles with an average particle size of 5 μm were dispersed in NMP solvent to prepare a lithium borate slurry. The lithium borate slurry was then coated onto the inner wall of the cover plate of the battery casing and vacuum dried to form a coated portion, resulting in a battery casing with the coated portion.

[0170] The prepared positive electrode, the separator with a polyethylene / polypropylene multilayer structure, and the prepared negative electrode are sequentially stacked into an electrode assembly, then inserted into a housing with a coated portion and equipped with a vent and an overcharge safety device, and electrolyte is injected therein to manufacture a rechargeable lithium battery cell. The electrolyte is prepared by the following steps: mixing ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a volume ratio of 2:4:4, and adding 1.1M of lithium LiPF6 salt to the mixed solvent to prepare the electrolyte, and then adding 1.5 parts by weight of ethylene carbonate to 100 parts by weight of the electrolyte.

[0171] Example 2

[0172] The battery cell is manufactured in the same manner as in Example 1, except that the coating portion is formed by coating the inner wall of the casing with lithium borate slurry.

[0173] Comparative Example 1

[0174] The battery cells are manufactured in the same manner as in Example 1, except that no coating containing lithium borate is formed in the casing.

[0175] Evaluation Example 1: 5V Overcharge Evaluation

[0176] The battery cells according to Example 1 and Comparative Example 1 were charged to 5V at a constant current of 0.5C at 25°C and then cut off at 0.1C. Here, the gas generation per battery weight (cc / g) was measured, and the results are shown below. Figure 3 Regarding the overcharge C rate, based on the estimated capacity, the capacity is measured by the following steps: charging at a constant current to 4.3V at a 0.2C rate, charging at a constant voltage to a current of 0.05C, then pausing for 10 minutes, and discharging at a constant current at a 0.2C rate to 3V as a reference for the 1C rate.

[0177] Reference Figure 3 Comparative Example 1, charged with a 5V overvoltage, exhibited a low gas generation of 0.2 cc / g, which resulted in insufficient internal pressure increase in the casing to allow the overcharge safety device to operate. On the other hand, Example 1 exhibited a high gas generation of 1.2 cc / g, which was sufficient for the internal pressure of the casing to allow the overcharge safety device to operate rapidly during overvoltage charging. In rechargeable lithium batteries, the amount of gas generated per cell weight was greater than or equal to 1.0 cc / g during a 5.0V overcharge evaluation.

[0178] Evaluation Example 2: Current Assessment During Overvoltage Charging

[0179] A three-electrode cup-shaped battery was fabricated by coating LiBO2 onto aluminum foil and punching a 14mm circle, and then using lithium as the negative electrode. In this cup-shaped battery, an electrolyte containing vinylene carbonate, identical to that used in Example 1, was placed inside, and the current change was monitored while the voltage was increased at a predetermined rate; this is referred to as Reference Example A. Additionally, the battery of Reference Example B was fabricated in the same manner as Reference Example A, except that an electrolyte excluding vinylene carbonate was used. The current change of the batteries in Reference Examples A and B was measured while the voltage was increased from 3V to 7V at a predetermined rate of 0.1mV / sec at 25°C, and the results are shown in… Figure 4 middle.

[0180] Reference Figure 4 Reference Example A exhibited a sharp current increase from approximately 4.7V, but Reference Example B, which does not include vinylene carbonate, did not exhibit a current change up to 7V. Therefore, as Figure 3 As shown, the increase in the amount of gas produced is confirmed to be due to the effects of lithium borate inside the casing and vinylene carbonate included in the electrolyte.

[0181] Although this disclosure has been described in conjunction with exemplary embodiments now considered practical, it should be understood that the invention is not limited to the disclosed embodiments. Rather, it is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the claims.

Claims

1. A rechargeable lithium battery, said rechargeable lithium battery comprising: Positive electrode; negative electrode; A diaphragm is located between the positive electrode and the negative electrode; Electrolytes, including vinylene carbonate; and The housing is configured to accommodate the positive electrode, the negative electrode, the diaphragm, and the electrolyte. in, The housing includes a coating portion on at least a portion of its interior, the coating portion comprising lithium borate particles. The housing includes an overcharge safety device, and The coated portion of the casing comes into contact with the electrolyte.

2. The rechargeable lithium battery according to claim 1, wherein, In the rechargeable lithium battery, during a 5.0V overcharge assessment, the amount of gas generated per battery weight is greater than or equal to 1.0 cc / g.

3. The rechargeable lithium battery according to claim 1, wherein, The overcharge safety device is configured such that the internal pressure of the housing is greater than or equal to 7 kgf / cm². 2 Time operation.

4. The rechargeable lithium battery according to claim 1, wherein, The overcharge safety device is configured to disconnect the circuit when the internal pressure of the housing becomes a predetermined value or greater.

5. The rechargeable lithium battery according to claim 1, wherein, The overcharge safety device is configured to cause a short circuit when the internal pressure of the housing becomes a predetermined value or greater.

6. The rechargeable lithium battery according to claim 1, wherein, The lithium borate particles include LiBO2 and Li3B7O. 12 Li6B4O9, Li3B 11 O 18 Li₂B₄O₇, Li₃BO₃, Li₈B₆O 13 Li5B3O7, Li4B2O5, Li 10 B4O 11 Li8B2O7 or any combination thereof.

7. The rechargeable lithium battery according to claim 1, wherein, The average particle size of the lithium borate particles is less than or equal to 10 μm.

8. The rechargeable lithium battery according to claim 1, wherein, The coating is applied to at least one of the inner walls of the housing and the inner walls of the cover plate.

9. The rechargeable lithium battery according to claim 1, wherein, Based on the total weight of the electrolyte, the content of vinylene carbonate is 0.1wt% to 5wt%.

10. The rechargeable lithium battery according to claim 1, wherein, The positive electrode includes a positive electrode active material, which comprises particles containing a lithium transition metal composite oxide and a boron coating on the surface of the particles.

11. The rechargeable lithium battery according to claim 10, wherein, The boron coating comprises lithium borate, and the lithium borate comprises LiBO2 and Li3B7O. 12 Li6B4O9, Li3B 11 O 18 Li₂B₄O₇, Li₃BO₃, Li₈B₆O 13 Li5B3O7, Li4B2O5, Li 10 B4O 11 Li8B2O7 or any combination thereof.

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