Electrochemical device and electronic device including the same

Abstract

The present invention relates to an electrochemical device and an electronic device including the same. Specifically, the present invention provides an electrochemical device, the electrochemical device including a negative electrode and an electrolyte, the negative electrode including a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, the negative electrode active material layer including a first region and a second region, the thickness of an arbitrary position of the first region is smaller than the average thickness of the second region, and the electrolyte includes a salt having a P-O bond at a specific content. The electrochemical device of the present invention has excellent cycle characteristics.

Description

Technical Field

[0001] The present invention relates to the field of energy storage technologies, and in particular, to electrochemical devices and electronic devices including the same, and more particularly to lithium-ion batteries.

Background Art

[0002] Electrochemical devices (e.g., lithium-ion batteries) are widely applied in fields and industries such as smart products (electronic products such as mobile phones, notebook computers, cameras, etc.), electric vehicles, power tools, drones, smart robots, and large-scale energy storage due to their advantages such as high energy density, high operating voltage, lightweight, low self-discharge rate, long cycle life, no memory effect, and environmental friendliness. However, with the rapid progress of information and communication technologies and the diverse changes in market needs, the requirements and challenges for the power supplies of electronic products, such as being thinner, lighter, more diverse in appearance, higher volume energy density and mass energy density, higher safety, and higher output, are becoming increasingly high.

[0003]

[0004] In the preparation process of an electrochemical device, usually, an active material layer is formed on the surface of a current collector by a coating method. However, due to the limitations of the production process, the problem of thinning of the edge thickness by this coating method is difficult to avoid, which has an adverse effect on the characteristics of the electrochemical device, especially the cycle characteristics.

Summary of the Invention

[0005] Embodiments of the present invention attempt to solve at least one problem in the related fields by providing an electrochemical device and an electronic device including the same to at least some extent.

[0006] ​In one embodiment, the present invention provides an electrochemical device, the electrochemical device including a negative electrode and an electrolytic solution, the negative electrode including a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, the negative electrode active material layer including a first region and a second region, a thickness D1 of the first region being smaller than an average thickness D2 of the second region, and the electrolytic solution including a salt having a P—O bond, and based on the first region per 1 cm 2 the content of the salt having a P—O bond is 0.05 g or less.

[0007] According to an embodiment of the present invention, D1 and D2 satisfy 0 < D1 ≦ D2 × 97%.

[0008] According to an embodiment of the present invention, the salt having a P—O bond is LiPO 2 F 2 、NaPO 2 F 2 、KPO 2 F 2 、CsPO 2 F 2 and includes at least one of lithium difluorobis(oxalato)phosphate (LiDFOP) and lithium tetrafluorooxalatophosphate (LiTFOP).

[0009] According to an embodiment of the present invention, the electrolytic solution further includes a first additive, the first additive including at least one of 1,3-propanesultone, fluoroethylene carbonate, vinylene carbonate, succinic anhydride, and maleic anhydride.

[0010] According to an embodiment of the present invention, based on the first region per 1 cm 2 the content of the first additive is 0.001 g to 0.2 g.

[0011] According to an embodiment of the present invention, the electrolytic solution further includes a second additive, the second additive being lithium tetrafluoroborate (LiBF 4) Lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTDI), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), adiponitrile (AND), succinonitrile (SN), 1,3,6-hexanetricarbonitrile (HTCN), 1,2,3-tris(2-cyanoxy)propane, 1,4-dicyano-2-butene, glutaronitrile, and at least one of tris(2-cyanoethyl)phosphine, and based on the weight of the electrolyte, the content of the second additive is 0.1 wt% to 10 wt%.

[0012] According to an embodiment of the present invention, the first region is located at the edge of the negative electrode active material layer, and the width of the first region is 15 μm or less.

[0013] According to an embodiment of the present invention, the area of the first region is 20% or less of the total area of the negative electrode active material layer.

[0014] According to an embodiment of the present invention, the negative electrode active material layer contains a negative electrode active material, and the median diameter of the negative electrode active material is 5 μm to 20 μm.

[0015] According to an embodiment of the present invention, the compression density of the negative electrode is 1.3 g / cm 3 ~1.8 g / cm 3 is.

[0016] In another embodiment, the present invention provides an electronic device, and the electronic device includes an electrochemical device as described above.

[0017] Other aspects and advantages of the embodiments of the present invention are partially described, shown, or interpreted by the implementation of the embodiments of the present invention in the following description.

Brief Description of the Drawings

[0018] Hereinafter, in order to describe embodiments of the present invention, the necessary drawings for describing embodiments of the present invention or the prior art will be outlined. The drawings described below are clearly only a part of the embodiments of the present invention. For those skilled in the art, without creative effort, it is still possible to obtain the drawings of other embodiments based on the structures illustrated in these drawings.

Figure 1

Figure 2

Figure 3

Figure 4

Mode for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described in detail. Throughout the specification of the present invention, components having the same or similar parts and the same or similar functions are denoted by similar reference numerals. The embodiments related to the drawings described in the present invention are illustrative and schematic, and are used to generally understand the present invention. The embodiments of the present invention should not be construed as limiting the present invention.

[0020] Unless otherwise specified, the following terms used in this specification have the meanings shown below.

[0021] The term "about" is used to explain and describe small variations. When used in combination with an instance or situation, the term can refer to an example where the instance or situation occurred exactly and an example where the instance or situation occurred very approximately. For example, when used in combination with a numerical value, the term can refer to a variation range of ±10% or less of the numerical value, for example, ±5% or less, ±4% or less, ±3% or less, ±2% or less, ±1% or less, ±0.5% or less, ±0.1% or less, or ±0.05% or less. Note that in this specification, quantities, ratios, and other numerical values may be shown in the form of a range. Such a range form is for the purpose of convenience and brevity and should be understood flexibly. The range form includes not only the numerical values clearly specified as the limits of the range, but also each and every numerical value or sub-range included in the range, which is equivalent to each numerical value or sub-range being clearly specified.

[0022] In the embodiments and claims for carrying out the invention, a list of terms connected by the term "at least one" can mean any combination of the listed terms. For example, if terms A and B are listed, the phrase "at least one of A and B" means only A, only B, or A and B. In other examples, if terms A, B, and C are listed, "at least one of A, B, and C" means only A, only B, only C, A and B (excluding C), A and C (excluding B), B and C (excluding A), or all of A, B, C. Term A may include a single element or a plurality of elements. Term B may include a single element or a plurality of elements. Term C may include a single element or a plurality of elements.

[0023] When preparing an electrochemical device (for example, a lithium-ion battery), an active material slurry is applied to a current collector by a coating method to form an active material layer, and then an electrode is prepared. However, the applied active material slurry has a certain fluidity, and there are limitations in the conventional production process. In the active material layer on the current collector, the phenomenon that the thickness of the edge region is smaller than that of the central region is inevitable. As shown in FIG. 1, the active material layer on the current collector includes a first region (i.e., a thinning region) with a gradually decreasing thickness and a second region with a substantially uniform thickness. The existence of the thinning region has an adverse effect on the characteristics of the electrochemical device. For example, in the thinning region of the negative electrode, the interface between the electrolyte and the negative electrode deteriorates, the stress is non-uniform, leading to an increase in polarization, a shortage of space for lithium intercalation in the negative electrode, a difference in current distribution in the negative electrode active material layer during the initial charging process, which delays the film formation in the thinning region. These factors lead to an increase in side reactions during the cycle process of the electrochemical device, making the lithium deposition phenomenon likely to occur and deteriorating the cycle characteristics.

[0024] To solve the above problems, the present invention uses an electrolyte containing a salt having a P-O bond with a specific content to compensate for the adverse effects of the thinning region of the negative electrode active material layer and improve the cycle characteristics of the electrochemical device. Specifically, the present invention provides an electrochemical device including a positive electrode, a negative electrode, and an electrolyte described below. In some embodiments, the electrochemical device further includes a separator provided between the positive electrode and the negative electrode.

[0025] Negative electrode The negative electrode used in the electrochemical device of the present invention includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. The negative electrode active material layer includes a first region and a second region, and the thickness D1 at any position in the first region is smaller than the average thickness D2 of the second region.

[0026] In some embodiments, D1 and D2 satisfy 0 < D1 ≤ D2 × 97%.

[0027] In some embodiments, the first region is located at the edge of the negative electrode active material layer, and the width of the first region is 15 μm or less. In some embodiments, the width of the first region is 12 μm or less. In some embodiments, the width of the first region is 10 μm or less. In some embodiments, the width of the first region is 8 μm or less. In some embodiments, the width of the first region is 5 μm or less. The "width of the first region" is the distance from the boundary position between the negative electrode current collector without the negative electrode active material coated thereon and the negative electrode current collector with the negative electrode active material coated thereon to the point where the thickness of the negative electrode active material layer becomes 97% of the thickness of the central region of the negative electrode active material layer. The "width of the first region" may be the distance from the edge position of the negative electrode active material layer to the point where the thickness of the negative electrode active material layer becomes 97% of the thickness of the central region of the negative electrode active material layer. When the width of the first region is within the above range, the thinning region of the negative electrode active material layer is small, which contributes to improving the cycle characteristics of the electrochemical device.

[0028] In some embodiments, the area of the first region is 20% or less of the total area of the negative electrode active material layer. In some embodiments, the area of the first region is 18% or less of the total area of the negative electrode active material layer. In some embodiments, the area of the first region is 15% or less of the total area of the negative electrode active material layer. In some embodiments, the area of the first region is 12% or less of the total area of the negative electrode active material layer. In some embodiments, the area of the first region is 10% or less of the total area of the negative electrode active material layer. In some embodiments, the area of the first region is 8% or less of the total area of the negative electrode active material layer. In some embodiments, the area of the first region is 5% or less of the total area of the negative electrode active material layer. The smaller the area of the first region, the higher the requirements for the process and the higher the process cost. When the area of the first region in the total area of the negative electrode active material layer is within the above range, the adverse effects caused by the thinning region of the negative electrode active material layer can be effectively reduced, and the cycle characteristics of the electrochemical device can be improved without a significant increase in the cost of additional processes.

[0029] In some embodiments, the negative electrode active material layer contains a negative electrode active material. In some embodiments, the negative electrode active material can be any material that can electrochemically occlude and release metal ions such as lithium ions. In some embodiments, the negative electrode active material includes one or more of a carbonaceous material, a silicon-carbon material, an alloy material, and a lithium-containing metal composite oxide material.

[0030] In some embodiments, the median diameter of the negative electrode active material is 5 μm to 20 μm. In some embodiments, the median diameter of the negative electrode active material is 8 μm to 18 μm. In some embodiments, the median diameter of the negative electrode active material is 10 μm to 15 μm. In some embodiments, the median diameter of the negative electrode active material is 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, or 20 μm, or within the range consisting of any two of these values. The "median diameter" refers to the particle diameter at which the cumulative volume from the small particle diameter side is 50% in the particle size distribution of the negative electrode active material based on volume, that is, the volume of the negative electrode active material smaller than the particle diameter accounts for 50% of the total volume of the negative electrode active material. When the median diameter of the negative electrode active material is within the above range, the cycle characteristics of the electrochemical device can be further improved.

[0031] In some embodiments, the negative electrode active material layer further contains a negative electrode binder. In some embodiments, the negative electrode binder includes one or more of styrene-butadiene rubber, fluorine-based rubber, and ethylene propylene diene.

[0032] In some embodiments, the negative electrode active material layer further contains a negative electrode conductive agent. In some embodiments, the negative electrode conductive agent includes one or more of a metal material having conductivity and a conductive polymer. In some embodiments, the negative electrode conductive agent includes one or more of a carbon material and the like. In some embodiments, the carbon material includes, but is not limited to, graphite, carbon black, acetylene black, and ketjen black.

[0033] In some embodiments, the compression density of the negative electrode is 1.3 g / cm 3 ~1.8 g / cm 3 In some embodiments, the compression density of the negative electrode is 1.4 g / cm 3 ~1.6 g / cm 3 In some embodiments, the compression density of the negative electrode is 1.5 g / cm 3 In some embodiments, the compression density of the negative electrode is 1.5 g / cm

[0034] In some embodiments, the negative electrode current collector includes a negative electrode conductive material. In some embodiments, the negative electrode current collector includes, but is not limited to, copper, nickel, and stainless steel. In some embodiments, the surface of the negative electrode current collector is roughened, and the roughened surface can improve the adhesiveness of the negative electrode active material. In some embodiments, the roughened negative electrode current collector includes, but is not limited to, electrolytic copper foil.

[0035] In some embodiments, a negative electrode active material layer is provided on one surface of the negative electrode current collector. In some embodiments, negative electrode active material layers are provided on both surfaces of the negative electrode current collector. In some embodiments, the negative electrode current collector has a region where no negative electrode active material layer is provided on at least one surface, which is also called an empty foil region.

[0036] Electrolyte The electrolyte used in the electrochemical device of the present invention contains a salt having a P—O bond, and based on the first region per 1 cm 2 the content of the salt having a P—O bond is 0.05 g or less.

[0037] In some embodiments, the salt having a P—O bond is an inorganic salt having a P—O bond.

[0038] In some embodiments, the salt having a P—O bond is LiPO 2 F 2 NaPO 2 F 2 KPO 2 F 2 CsPO 2 F 2, lithium difluoro bis(oxalato) phosphate, and Lithium tetrafluoroxalate phosphate includes at least one of

[0039] In some embodiments, based on the first region per 1 cm 2 , the content of the salt having a P—O bond is 0.04 g or less. In some embodiments, based on the first region per 1 cm 2 , the content of the salt having a P—O bond is 0.03 g or less. In some embodiments, based on the first region per 1 cm 2 , the content of the salt having a P—O bond is 0.02 g or less. In some embodiments, based on the first region per 1 cm 2 , the content of the salt having a P—O bond is 0.01 g or less. In some embodiments, based on the first region per 1 cm 2 , the content of the salt having a P—O bond is 0.005 g or less. In some embodiments, based on the first region per 1 cm 2 , the content of the salt having a P—O bond is 0.001 g or less. In some embodiments, based on the first region per 1 cm 2 , the content of the salt having a P—O bond is 0.0005 g or less.

[0040] When the electrochemical device is initially charged, the salt having a P—O bond preferentially aggregates on the surface of the negative electrode, not only contributing to the film formation in the second region of the negative electrode active material layer, but more importantly, also contributing to the film formation in the first region of the negative electrode active material layer, thereby improving the stability of the formed film, reducing the occurrence of side reactions in the first region of the negative electrode active material layer, reducing the thickness change due to the by-products in the first region, and enhancing the cycle stability of the electrochemical device. In addition, the use of the salt having a P—O bond contributes to reducing the adverse effects due to the difference in current distribution between the first region and the second region of the negative electrode active material layer, and ensuring the effectiveness of film formation in the first region of the negative electrode active material layer. Including the salt having a P—O bond in the above content in the electrolyte reduces the adverse effects due to the thin layer region of the negative electrode active material layer and significantly improves the cycle characteristics of the electrochemical device.

[0041] In some embodiments, the electrolytic solution further includes a first additive, and the reduction potential of the first additive is 2.5 V or less. When the reduction potential of the first additive is 2.5 V or less, a protective layer can be formed on the surface of the negative electrode, which contributes to reducing the adverse effects caused by the thinning region of the negative electrode active material layer, and significantly improving the cycle characteristics of the electrochemical device.

[0042] In some embodiments, the first additive includes at least one of 1,3 - propane sultone (PS), fluoroethylene carbonate (FEC), vinylene carbonate (VC), succinic anhydride, and maleic anhydride.

[0043] In some embodiments, the first additive includes 1,3 - propane sultone (PS) and fluoroethylene carbonate (FEC).

[0044] In some embodiments, the weight fraction of 1,3 - propane sultone in the electrolytic solution is greater than the weight fraction of fluoroethylene carbonate in the electrolytic solution. In some embodiments, the ratio of the weight fraction of 1,3 - propane sultone in the electrolytic solution to the weight fraction of fluoroethylene carbonate in the electrolytic solution is 1.5 or less. When the ratio of the weight fractions is within this range, the cycle characteristics of the electrochemical device can be improved, and the gas generation amount of the electrochemical device can be reduced.

[0045] In some embodiments, the first additive includes 1,3 - propane sultone (PS), fluoroethylene carbonate (FEC), and vinylene carbonate (VC).

[0046] In some embodiments, 1 cm 2 Based on the first region per unit area, the content of the first additive is 0.001 g to 0.2 g. In some embodiments, 1 cm 2 Based on the first region per unit area, the content of the first additive is 0.005 g to 0.2 g. In some embodiments, 1 cm2 Based on the first region per hit, the content of the first additive is 0.01 g to 0.15 g. In some embodiments, 1 cm 2 Based on the first region per hit, the content of the first additive is 0.05 g to 0.13 g. In some embodiments, 1 cm 2 Based on the first region per hit, the content of the first additive is 0.08 g to 0.1 g. In some embodiments, 1 cm 2 Based on the first region per hit, the content of the first additive is 0.001 g, 0.005 g, 0.01 g, 0.03 g, 0.05 g, 0.07 g, 0.1 g, 0.15 g, or 0.2 g, or within the range consisting of any two of the above values. When the content of the first additive in the electrolyte is within the above range, it contributes to further improving the cycle characteristics of the electrochemical device.

[0047] In some embodiments, the electrolyte further contains a second additive, and the second additive is lithium tetrafluoroborate (LiBF 4 ), lithium bis(fluorosulfonyl)imide (LiFSI), Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) , 4,5-dicyano-2-trifluoromethylimidazole lithium (LiTDI), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate, adiponitrile (ADN), succinonitrile, 1,3,6-hexanetricarbonitrile (HTCN), 1,2,3-tris(2-cyanoxy)propane, 1,4-dicyano-2-butene, glutaronitrile, and at least one of tris(2-cyanoethyl)phosphine. In some embodiments, the second additive contains LiBF 4 and LiDFOB. In some embodiments, the second additive contains HTCN and LiDFOB. In some embodiments, the second additive contains LiBF 4 and LiDFOB and LiTFSI. In some embodiments, the second additive contains HTCN, LiDFOB, and LiTFSI.

[0048] The second additive can form a protective layer on the surface of the positive electrode, reduce the occurrence of side reactions at the positive electrode, and further reduce the elution of metal ions from the positive electrode. During the cycling process of the electrochemical device, the stability of the negative electrode protective film is affected by the products of side reactions at the positive electrode. Therefore, the second additive plays a role in protecting both the positive electrode and the negative electrode, contributing to improving the cycling characteristics of the electrochemical device.

[0049] In some embodiments, based on the weight of the electrolyte, the content of the second additive is 0.1 wt% to 10 wt%. Based on the weight of the electrolyte, the content of the second additive is 0.2 wt% to 5 wt%. In some embodiments, based on the weight of the electrolyte, the content of the second additive is 0.5 wt% to 3 wt%. In some embodiments, based on the weight of the electrolyte, the content of the second additive is 1 wt% to 2 wt%. In some embodiments, based on the weight of the electrolyte, the content of the second additive is 0.1 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%, or within the range consisting of any two of the above values. When the content of the second additive in the electrolyte is within the above range, it contributes to further improving the cycling characteristics of the electrochemical device.

[0050] The electrolyte used in the present invention contains LiPF 6 In some embodiments, the concentration of LiPF 6 is in the range of 0.8 mol / L to 3 mol / L, in the range of 0.8 mol / L to 2.5 mol / L, in the range of 0.8 mol / L to 2 mol / L, or in the range of 1 mol / L to 2 mol / L. In some embodiments, the concentration of the lithium salt is about 1 mol / L, about 1.15 mol / L, about 1.2 mol / L, about 1.5 mol / L, about 2 mol / L, or about 2.5 mol / L.

[0051] The solvents used in the electrolytic solution in the embodiments of the present invention include, but are not limited to, cyclic carbonates, chain carbonates, cyclic carboxylic acid esters, chain carboxylic acid esters, cyclic ethers, chain ethers, phosphorus-containing organic solvents, sulfur-containing organic solvents, and aromatic fluorine-containing solvents.

[0052] In some embodiments, the cyclic carbonates include, but are not limited to, ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate. In some embodiments, the cyclic carbonates have 3 to 6 carbon atoms.

[0053] In some embodiments, the chain carbonates include chain carbonates such as dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate, and chain carbonates substituted with fluorine, such as bis(fluoromethyl) carbonate, bis(difluoromethyl) carbonate, bis(trifluoromethyl) carbonate, bis(2-fluoroethyl) carbonate, bis(2,2-difluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) carbonate, 2-fluoroethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate, and 2,2,2-trifluoroethyl methyl carbonate, but are not limited thereto.

[0054] In some embodiments, the cyclic carboxylic acid esters include, but are not limited to, γ-butyrolactone and γ-valerolactone. In some embodiments, a part of the hydrogen of the cyclic carboxylic acid ester may be substituted with fluorine.

[0055] In some embodiments, the chain carboxylic acid esters include, but are not limited to, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate, and ethyl pivalate. In some embodiments, some of the hydrogens of the chain carboxylic acid esters may be substituted with fluorine. In some embodiments, the chain carboxylic acid esters substituted with fluorine include, but are not limited to, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroethyl trifluoroacetate.

[0056] In some embodiments, the cyclic ethers include, but are not limited to, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl-1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane.

[0057] In some embodiments, the chain ethers include, but are not limited to, dimethoxymethane, 1,1-dimethoxyethane, 1,2-dimethoxyethane, diethoxymethane, 1,1-diethoxyethane, 1,2-diethoxyethane, ethoxymethoxymethane, 1,1-ethoxymethoxyethane, and 1,2-ethoxymethoxyethane.

[0058] In some embodiments, the phosphorus-containing organic solvents include, but are not limited to, trimethyl phosphate, triethyl phosphate, dimethylethyl phosphate, methyldiethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(2,2,3,3,3-pentafluoropropyl) phosphate.

[0059] In some embodiments, the sulfur-containing organic solvent includes, but is not limited to, sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate, and dibutyl sulfate. In some embodiments, a part of the hydrogen of the sulfur-containing organic solvent may be substituted with fluorine.

[0060] In some embodiments, the aromatic fluorine-containing solvent includes, but is not limited to, fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, pentafluorobenzene, hexafluorobenzene, and trifluoromethylbenzene.

[0061] In some embodiments, the solvent used in the electrolyte of the present invention includes one or more of the above-mentioned solvents. In some embodiments, the solvent used in the electrolyte of the present invention includes cyclic carbonates, chain carbonates, cyclic carboxylic acid esters, chain carboxylic acid esters, and combinations thereof. In some embodiments, the solvent used in the electrolyte of the present invention includes an organic solvent selected from the group consisting of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, n-propyl acetate, ethyl acetate, and combinations thereof. In some embodiments, the solvent used in the electrolyte of the present invention includes ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, propyl propionate, γ-butyrolactone, and combinations thereof.

[0062] Positive electrode The positive electrode includes a positive electrode current collector and a positive electrode active material provided on the positive electrode current collector. The specific type of the positive electrode active material is not particularly limited and may be selected as needed.

[0063] In some embodiments, the positive electrode active material includes a positive electrode material capable of occluding and releasing lithium (Li). Examples of the positive electrode material capable of occluding and releasing lithium (Li) may include lithium cobaltate, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, lithium manganate, lithium iron manganese phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium iron phosphate, lithium titanate, and lithium-rich manganese-based materials.

[0064] Specifically, the chemical formula of lithium cobaltate may be Chemical Formula 1. Li x Co a M1 b O 2-c Chemical Formula 1

[0065] M1 represents at least one element selected from nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), yttrium (Y), lanthanum (La), zirconium (Zr), silicon (Si), fluorine (F), and sulfur (S), and the values of x, a, b, and c are respectively in the ranges of 0.8 ≦ x ≦ 1.2, 0.8 ≦ a ≦ 1, 0 ≦ b ≦ 0.2, and -0.1 ≦ c ≦ 0.2.

[0066] The chemical formula of lithium nickel cobalt manganate or lithium nickel cobalt aluminate may be Chemical Formula 2. Li y Ni d M2 e O 2-f Chemical Formula 2

[0067] M2 represents at least one element selected from cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), tungsten (W), zirconium (Zr), silicon (Si), fluorine (F), and sulfur (S), and the values of y, d, e, and f are respectively in the ranges of 0.8 ≦ y ≦ 1.2, 0.3 ≦ d ≦ 0.98, 0.02 ≦ e ≦ 0.7, and -0.1 ≦ f ≦ 0.2.

[0068] The chemical formula of lithium manganate may be Chemical Formula 3. Li z Mn 2-g M3 g O 4-h Chemical Formula 3

[0069] M3 represents at least one element selected from cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr), niobium (Nb), tantalum (Ta), and tungsten (W), and the values of z, g, and h are respectively in the ranges of 0.8 ≦ z ≦ 1.2, 0 ≦ g < 1.0, and -0.2 ≦ h ≦ 0.2.

[0070] In some embodiments, the positive electrode active material layer may have a coating on its surface or may be mixed with another compound having a coating. The coating may include at least one compound of a coated element selected from oxides of the coated element, hydroxides of the coated element, oxyhydroxides of the coated element, oxycarbonates of the coated element, and hydroxycarbonates of the coated element. The compound used for the coating may be amorphous or crystalline. The coated elements contained in the coating may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, F, and mixtures thereof. As long as it does not adversely affect the properties of the positive electrode active material, the coating may be formed by any method. For example, the method may include any coating method known to those skilled in the art, such as spraying, dipping, etc.

[0071] In some embodiments, the positive electrode active material layer further includes a binder and optionally further includes a positive electrode conductive material.

[0072] The binder can enhance the binding between the positive electrode active material particles and also enhance the binding between the positive electrode active material and the current collector. Non-limiting examples of the binder include polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene butadiene rubber, acrylate (ester) styrene butadiene rubber, epoxy resin, nylon, etc.

[0073] The positive electrode active material layer contains a positive electrode conductive material to impart conductivity to the electrode. The positive electrode conductive material may include any conductive material as long as it does not cause a chemical change. Non-limiting examples of the positive electrode conductive material include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powders and metal fibers including copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.

[0074] The positive electrode current collector used in the electrochemical device according to the present invention may be aluminum (Al), but is not limited thereto.

[0075] Separator In some embodiments, the electrochemical device of the present invention provides a separator between the positive electrode and the negative electrode to prevent short-circuiting of the current due to contact between the two electrode plates and to allow lithium ions to pass through.

[0076] The material and shape of the separator used in the electrochemical device of the present invention are not particularly limited and may be any of those disclosed in the prior art. In some embodiments, the separator includes a polymer (e.g., synthetic resin) or an inorganic substance (e.g., ceramics) formed from a material that is stable with respect to the electrolytic solution of the present invention. In some embodiments, the separator includes a porous membrane made of the polymer or the inorganic substance. In some embodiments, the separator includes a laminated membrane formed by laminating two or more types of porous membranes. In some embodiments, the polymer includes, but is not limited to, polytetrafluoroethylene, polypropylene, and polyethylene.

[0077] In some embodiments, the separator includes the porous membrane (substrate material layer) and a polymer compound layer provided on one or both surfaces of the substrate material layer, thereby improving the adhesion of the separator to the positive electrode and the negative electrode and suppressing the generation of strain when winding the electrode sheet, suppressing the decomposition reaction of the electrolytic solution, and suppressing the leakage of the electrolytic solution impregnating the substrate material layer. By using this separator, even when charging / discharging is repeated, the resistance of the electrochemical device does not increase significantly, and the expansion of the electrochemical device can be suppressed.

[0078] In some embodiments, the polymer compound layer includes, but is not limited to, polyvinylidene fluoride. Polyvinylidene fluoride has excellent physical strength and electrochemical stability. The polymer compound layer may be formed by preparing a solution in which a polymer material is dissolved, applying the solution to the substrate material layer, or immersing the substrate material layer in the solution, and finally drying.

[0079] Use The electrochemical device of the present invention includes any device in which an electrochemical reaction occurs, and specific examples thereof include all types of primary batteries and secondary batteries. In particular, this electrochemical device is a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, and a lithium ion polymer secondary battery.

[0080] The use of the electrochemical device of the present invention can be used, without particular limitation, in any electronic device known in the prior art. In one embodiment, the electrochemical device of the present invention can be used in a notebook computer, a pen input computer, a mobile computer, an e-book player, a mobile phone, a portable facsimile machine, a portable copier, a portable printer, a stereo headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD player, a mini CD, a transceiver, an electronic notebook, a calculator, a memory card, a portable tape recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, an assist bicycle, a bicycle, a lighting fixture, a toy, a game machine, a clock, a power tool, a flash, a camera, a large household storage battery, and a lithium ion capacitor, etc., but is not limited thereto.

[0081] Example Hereinafter, the characteristics of the lithium ion battery of the present invention will be evaluated for examples and comparative examples.

[0082] 1. Preparation of Lithium Ion Battery Comparative Example 1 (1) Preparation of Negative Electrode Artificial graphite (median diameter 12.0 μm) as the negative electrode active material, conductive agent SuperP, sodium carboxymethyl cellulose (CMC), and styrene butadiene rubber (SBR) as the binder were mixed at a weight ratio of 96.4:1.5:0.5:1.6, deionized water was added, and the mixture was uniformly stirred to obtain a negative electrode slurry with a solid content of 54 wt%. The negative electrode slurry was uniformly coated on a copper foil, dried at 85 °C, and then cold rolled, die cut, slit, and wound. After that, it was dried under vacuum conditions at 120 °C for 12 hours to obtain a negative electrode with a length of 1544.0 ± 5.0 mm and a width of 66.5 ± 1.0 mm. The total area of the negative electrode active material layer on one side (based on one side) was 1544.0 × 66.5 = 102676 (mm 2 ) and was about 1027 cm 2 . The compression density of the negative electrode was 1.6 g / cm 3 .

[0083] According to the settings of the following comparative examples and examples, the viscosity of the negative electrode slurry was adjusted, application dies with different specifications were used, and the distance from the application die to the application roll and the speed of the base material on the conveyor belt were controlled, etc., so as to adjust and control the width and area of the first region of the negative electrode active material layer.

[0084] In Table 1, the widths of the first regions corresponding to the areas of the first regions in each comparative example and example are shown in the following table.

Table A

[0085] (2) Preparation of the positive electrode Li(Ni 0.8 Co 0.08 Mn 0.07 )Al 0.05 O 2 , which is a positive electrode active material, Super-P which is a conductive agent, and polyvinylidene fluoride were mixed with N-methylpyrrolidone (NMP) at a mass ratio of 97:1.4:1.6, stirred uniformly, and a positive electrode slurry with a solid content of 72 wt% was obtained. This positive electrode slurry was applied to an aluminum foil, dried at 85°C, and then cold-rolled, die-cut, slit, and tab-welded, and then dried under vacuum conditions at 85°C for 4 hours to obtain a positive electrode.

[0086] (3) Preparation of the electrolyte In a dry argon gas atmosphere, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at a mass ratio of EC:PC:DEC:EMC = 15:25:50:10. According to the settings of the examples and comparative examples, additives were added, dissolved, and stirred sufficiently, and then lithium salt LiPF 6 was added and mixed uniformly to obtain a base electrolyte, and the concentration of LiPF 6 was 1.2 mol / L.

[0087] According to the settings of the following comparative examples and examples, a salt having a P-O bond, a first additive, and / or a second additive were added to the base electrolyte to obtain an electrolyte.

[0088] (4) Preparation of separator A polyethylene (PE) film with a thickness of 7 μm was used, and on it, a PVDF slurry and an inorganic particle (the ratio of sheet-like boehmite and Al 2 O 3 with a ratio of 70:30) slurry were coated and dried to obtain a separator.

[0089] (5) Preparation of lithium-ion battery The obtained positive electrode, separator, and negative electrode were sequentially wound to form a bare cell. The bare cell was placed on an exterior foil, leaving an injection port. Electrolyte was injected into the injection port, and through processes such as packaging, formation (charging to 3.3 V at a constant current of 0.02 C and then charging to 3.6 V at a constant current of 0.1 C), and capacity Sorting etc., a lithium-ion battery (with a thickness of about 9.1 mm, a width of about 49 mm, and a length of about 74 mm) was obtained.

[0090] 2. Measurement method (1) Measurement method for cycle capacity retention rate and cycle thickness expansion rate of lithium-ion battery The lithium-ion battery was placed in a thermostat at 25 °C and left standing for 30 minutes until the lithium-ion battery reached a constant temperature. The initial thickness H0 of the lithium-ion battery was measured. The lithium-ion battery at a constant temperature was charged at a constant current of 1.0 C until the voltage reached 4.2 V, and then discharged at a constant voltage of 4.2 V until the current reached 0.05 C. Next, charging at a constant current of 4 C until the voltage reached 2.8 V was regarded as one charge-discharge cycle, and the capacity C0 of the first discharge was recorded. Using the same steps, 600 charge-discharge cycles were performed on the lithium-ion battery, and the measurement was stopped. The discharge capacity C1 after cycling and the thickness H1 of the lithium-ion battery were recorded.

[0091] The cycle capacity retention rate and cycle thickness expansion rate of the lithium-ion battery were calculated by the following formulas. Cycle capacity retention rate = C1 / C0 × 100% Cycle thickness expansion rate = (H1 - H0) / H0 × 100%

[0092] (2) Method for Measuring Thicknesses of First and Second Regions of Negative Electrode Active Material Layer When the negative electrode active material layer has the structure shown in FIG. 2, with the central axis of the length as the cross-section and the width direction as the center, a cross-section with a length of 1 cm is selected, and the thickness of the negative electrode active material layer is measured using a digital microscope system (VH X-950F). Ten points are randomly selected, and the average value E of the total thickness of the negative electrode sheet 0 and the average value E of the thickness of the current collector 1 are calculated, and the thickness D2 of the second region of the negative electrode active material layer is calculated by the formula: D2 = (E 0 - E 1 ) / 2.

[0093] With the central axis of the length as the cross-section, starting from the edge region of the negative electrode active material layer, one point is measured at intervals of 0.1 mm. For any single-sided negative electrode active material layer, the thickness from the surface away from the current collector to the surface of the current collector in contact with this negative electrode active material layer is measured as D1. The thicknesses of five points are measured. When all three of the three points among them satisfy D1 > D2 × 97%, at this time, the distance from the point closest to the edge of the negative electrode active material layer to the edge of the negative electrode active material layer is taken as the width of the first region of the negative electrode active material layer. The above thickness measurement unit is accurate to 0.01 mm. In the measurement process, the cross-section selection needs to include the first and second regions of the negative electrode active material layer.

[0094] When the negative electrode active material layer has the structure shown in FIG. 3, except that the central axis of the width is used as the cross-section, it is measured by a method substantially the same as the above.

[0095] When the negative electrode active material layer has the structure shown in FIG. 4, except that the central axes of the length and width are used as cross-sections respectively, it is measured by a method substantially the same as the above.

[0096] (3) Method for Measuring Content of Salt Having P—O Bond in Electrolyte The lithium-ion battery is discharged at a rate of 0.2C until the voltage reaches 2.8V, and the weight of the lithium-ion battery is measured as M 0and the tab and the exterior packaging were cut off to obtain a bare cell. The bare cell was centrifuged to obtain an electrolytic solution, and the anion content in the electrolytic solution was measured by ion chromatography IC (model: Thermo Fisher, AQUION), and the relative content Q of the salt having a P-O bond in the electrolytic solution was obtained. The centrifuged bare cell was immersed in dimethyl carbonate (DMC) for 72 hours and dried, and the total mass of the dried bare cell, the tab, and the packaging exterior was weighed, M 1 was used. Formula: (M 0 -M 1 )×Q was used to calculate the mass of the salt having a P-O bond in the bare cell. The mass of the salt having a P-O bond was divided by the total area of the first region of the negative electrode active material layer to obtain the mass of the salt having a P-O bond corresponding to the first region per unit area.

[0097] The types of the first additive and the second additive are measured by ion chromatography IC (model: Thermo Fisher, AQUION) or gas chromatography GC (model: Agilent7890A-5975C).

[0098] 3. Measurement Results Table 1 shows the influence of the composition of the electrolytic solution in each comparative example and the example and the first region in the negative electrode active material layer on the cycle characteristics of the lithium-ion battery. The content per unit area of the salt having a P-O bond or the first additive is the weight of the salt having a P-O bond or the first additive based on the first region per 1 cm 2 . In each example and comparative example shown in Table 1, the total area of the single-sided negative electrode active material layer is 1027 cm 2 .

[0099]

Table 1

[0100] As shown in Comparative Examples 1 to 9, reducing the area of the first region of the negative electrode active material layer can improve the cycle capacity retention rate of the lithium-ion battery and reduce its thickness expansion rate. However, the cycle capacity retention rate of the lithium-ion battery is low, the thickness expansion rate is high, and it is difficult to meet the usage needs.

[0101] As shown in Examples 1 to 13, when the electrolytic solution contains a salt having the following P-O bond, the cycle capacity retention rate of the lithium-ion battery can be significantly improved, and its thickness expansion rate can be significantly reduced. As shown in Examples 34 to 37, salts having different types of P-O bonds or combinations thereof can obtain substantially the same effects. 2 As shown in Examples 14 to 20, when the electrolytic solution further contains a first additive of 0.001 to 0.2 g / cm

[0102] As shown in Examples 14 to 20, when the electrolytic solution further contains a first additive of 0.001 to 0.2 g / cm 2 of the first additive, the cycle capacity retention rate of the lithium-ion battery can be further improved, and its thickness expansion rate can be reduced.

[0103] As shown in Examples 21 to 27, when the electrolytic solution further contains a second additive of 0.1 wt% to 10 wt%, the cycle capacity retention rate of the lithium-ion battery can be further improved, and its thickness expansion rate can be reduced. As shown in Examples 28 to 33, when a plurality of the first additive and / or the second additive are used in combination, the cycle capacity retention rate of the lithium-ion battery can be further improved, and its thickness expansion rate can be reduced.

[0104] In addition, when the area of the first region is 20% or less of the total area of the negative electrode active material layer, the cycle capacity retention rate of the lithium-ion battery can be further improved, and its thickness expansion rate can be reduced.

[0105] Table 2 shows the influence of the median diameter of the negative electrode active material on the cycle characteristics of the lithium-ion battery. The preparation methods of Examples 38 to 41 and Example 3 are substantially the same, but the parameters shown in Table 2 are different.

[0106]

Table 2

[0107] As shown in Table 2, when the median diameter of the negative electrode active material in the negative electrode active material layer is 5 μm to 20 μm, the cycle capacity retention rate of the lithium ion battery can be further improved and its thickness expansion rate can be reduced.

[0108] Throughout the specification, references by "some embodiments", "some of the embodiments", "one embodiment", "another example", "example", "specific example", or "some examples" mean that at least one embodiment or example of the present invention includes the specific features, structures, materials, or characteristics described in the said embodiment or example. Therefore, references described in various places throughout the specification, such as "in some embodiments", "in an embodiment", "in one embodiment", "in other examples", "in one example", "in a specific example", or "example", do not necessarily refer to the same embodiment or example of the present invention. Also, the specific features, structures, materials, or characteristics of this specification can be combined in any suitable way in one or more embodiments or examples.

[0109] Exemplary embodiments have been disclosed and described, but those skilled in the art should understand that the above-described embodiments are not to be construed as limiting the present invention, and that changes, substitutions, and modifications to the embodiments are possible without departing from the technical idea, principle, and scope of the present invention.

Claims

1. An electrochemical device comprising: a negative electrode and an electrolytic solution, wherein the negative electrode includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, the negative electrode active material layer includes a first region and a second region, the thickness D1 at any position in the first region is smaller than the average thickness D2 of the second region, and the electrolytic solution contains a salt having a P—O bond and having a content of 0.05 g or less per 1 cm2 of the first region, the salt having a P—O bond includes at least one of LiPO2F2, NaPO2F2, KPO2F2, CsPO2F2, lithium difluoro(bis(oxalato))phosphate, and lithium tetrafluorooxalate phosphate, the electrolytic solution further includes a first additive, the first additive includes at least one of 1,3 - propane sultone, fluoroethylene carbonate, vinylene carbonate, succinic anhydride, and maleic anhydride, based on 1 cm2 of the first region, the content of the first additive contained in the electrolytic solution is 0.001 g to 0.2 g, An electrochemical device.

2. D1 and D2 satisfy D1≤D2×97%, The electrochemical device according to Claim 1.

3. the electrolytic solution further includes a second additive, the second additive includes at least one of lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, 4,5 - dicyano - 2 - trifluoromethylimidazole lithium, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, adiponitrile, succinonitrile, 1,3,6 - hexanetricarbonitrile, 1,2,3 - tris(2 - cyanoxy)propane, 1,4 - dicyano - 2 - butene, glutaronitrile, and tris(2 - cyanoethyl)phosphine, and based on the weight of the electrolytic solution, the content of the second additive is 0.1 wt% to 10 wt%, The electrochemical device according to Claim 1.

4. the first region is located at the edge of the negative electrode active material layer, and the width of the first region is 15 μm or less, The electrochemical device according to Claim 1.

5. the area of the first region is 20% or less of the total area of the negative electrode active material layer, The electrochemical device according to Claim 1.

6. The negative electrode active material layer contains a negative electrode active material, and the median diameter of the negative electrode active material is 5 μm to 20 μm. The electrochemical device according to any one of claims 1 to 5.

7. Including the electrochemical device according to any one of claims 1 to 6, An electronic device.

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