Electrochemical device and electronic device including the same

Abstract

To provide an electrochemical device and an electronic device including the same with improved cycle characteristics.SOLUTION: An electrochemical device includes a negative electrode and an electrolyte, 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, a thickness D1 of the first region at an arbitrary position is smaller than an average thickness D2 of the second region, and the electrolyte includes a salt having a P-O bond, the content of which is 0.05 g or less based on the first region per 1 cm2, the first region is located at an edge of the negative electrode active material layer, and the width of the first region is 15 μm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Electrochemical devices (e.g., lithium-ion batteries) are known for their high energy density and high operating voltage. Lightweight, low self-discharge rate, long cycle life, no memory effect and environmentally friendly. Due to its advantages, smart products (electronic products such as mobile phones, laptops, cameras, etc.), electrical Automotive, power tools, drones, smart robots and large-scale energy storage, etc. However, with the rapid advancement of information and communication technology and the diversification and changes in market needs, As a result of this, for example, they become thinner, lighter, have more diverse shapes, and have higher volumetric energy High density and mass energy density, higher safety and higher power output, etc., are the main features of power sources for electronic products. The demands and challenges for this are becoming increasingly high.

[0003] In the preparation process of electrochemical devices, an active material layer is usually formed on the surface of a current collector by a coating method. However, due to limitations in the production process, this coating method can result in thin edge thickness. Problems are unavoidable, which adversely affect the performance of the electrochemical device, particularly its cycle performance.

[0004] In view of this, an electrochemical device with improved cycle characteristics and an electronic device including the same are provided. must be provided. Summary of the Invention

[0005] Embodiments of the present invention provide electrochemical devices and electronic devices that include the same, thereby reducing the To solve at least one problem in the related art to a certain 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, wherein the thickness D1 of the first region is smaller than the average thickness D2 of the second region, and the electrolytic solution includes a salt having a P-O bond, and based on the first region per 1 cm , the content of the salt having a P-O bond is 0.05 g or less. 2 Based on the first region per 1 cm , 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 includes at least one of LiPO2F2, NaPO2 F2, KPO2F2, CsPO2F2, lithium difluorobis(oxalato)phosphate ( LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP). At least one kind is included.

[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 electrolyte solution further comprises a second additive, , lithium tetrafluoroborate (LiBF4), lithium bis(fluorosulfonyl)iodate Lithium bis(trifluoromethanesulfonyl)imide (LiFSI), Lithium bis(trifluoromethanesulfonyl)imide (LiTFS I), lithium 4,5-dicyano-2-(trifluoromethyl)imidazole (LiTD I), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiDFOB), salicylate) borate (LiBOB), adiponitrile (AND), succinonitrile (S N), 1,3,6-hexanetricarbonitrile (HTCN), 1,2,3-tris(2-cyclohexyl) (anoxy)propane, 1,4-dicyano-2-butene, glutaronitrile, and tris (2-cyanoethyl)phosphine, 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 an 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% of the total area of ​​the negative electrode active material layer. The following is the result.

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

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

[0016] In another embodiment, the present invention provides an electronic device, the electronic device comprising: Includes gas and chemical equipment.

[0017] Other aspects and advantages of embodiments of the present invention are in part described, shown, or incorporated in the following description. It is interpreted by practicing the embodiments of the invention. [Brief explanation of the drawings]

[0018] In the following, in order to explain the embodiments of the present invention, the embodiments of the present invention or the prior art will be described. The drawings described below are clearly intended to illustrate the present invention. It is still possible for a person skilled in the art to understand this without any creative effort. The structures illustrated in these figures allow for the drawing of other embodiments. [Figure 1] FIG. 1 is a schematic diagram showing a thinned region of a negative electrode active material layer. [Figure 2] FIG. 2 is a schematic diagram showing the position of the thinned region of the negative electrode active material layer. [Figure 3] FIG. 3 is a schematic diagram showing the position of another thinned region of the negative electrode active material layer. [Figure 4] FIG. 4 is a schematic diagram showing the position of still another thinned region of the negative electrode active material layer. DETAILED DESCRIPTION OF THE INVENTION

[0019] The following examples of the present invention are described in detail. Components and components having the same or similar functions are designated by like reference numerals. The drawings and associated embodiments are exemplary and diagrammatic and are intended to provide a general understanding of the present invention. The examples of the present invention should not be construed as limiting the present invention.

[0020] Unless otherwise stated, the following terms used herein have the meanings indicated: .

[0021] The term "about" is used to describe and describe small variations. When used in conjunction with an instance or circumstance, the term refers to the exact instance or circumstance in which the instance or circumstance occurred. It can refer to instances where something has happened and instances where an incident or situation has occurred very similarly. For example: When used in conjunction with a numerical value, the term refers to a range of variation of no more than ±10% of the numerical value. For example, ±5% or less, ±4% or less, ±3% or less, ±2% or less, ±1% or less, ±0.5% Hereinafter, the tolerance can be ±0.1% or less, or ±0.05% or less. In this document, quantities, ratios, and other numerical values ​​may be expressed in range format. The format is for convenience and brevity and should be interpreted flexibly. It is intended to include all and each and every value included in said ranges, as well as any numerical value expressly specified in the limits of said ranges. It also includes values ​​or subranges, provided that each value or subrange is explicitly specified. is equivalent to

[0022] In the detailed description and claims, the term "at least one" Thus, a list of connected terms 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" can be used. " means A only, B only, or A and B. In other instances, terms A, B, and If item C is listed, "at least one of A, B, and C" means A only, B only , C only, A and B (excluding C), A and C (excluding B), B and C (excluding A), or A, Term A means all of B, C, and A. Term A may contain a single element or multiple elements. Term B may contain a single element or multiple elements. The term C may contain a single element or multiple elements. may include:

[0023] When preparing electrochemical devices (e.g., lithium-ion batteries), the active material is applied by coating. The slurry is applied to a current collector to form an active material layer, and then an electrode is prepared. The active material slurry has a certain fluidity, and there are limitations to the conventional production process. In the material layer, the thickness of the edge area is inevitably smaller than the thickness of the central area. As shown in FIG. 1, the active material layer on the current collector has a first region (i.e., The thinned region includes a second region of substantially uniform thickness. For example, the electrolyte may come into contact with the negative electrode in the thinned region of the negative electrode. The interface becomes poor and the stress is uneven, leading to increased polarization and lithium dissipation in the negative electrode. There is a lack of storage space, and there is a difference in the current distribution in the negative electrode active material layer during the initial charging process. These factors contribute to the cycling process of the electrochemical device. This leads to an increase in side reactions in the battery, which makes it easier for lithium deposition to occur and leads to poor cycle characteristics. become.

[0024] In order to solve the above problems, the present invention provides a salt having a specific content of PO bonds. By using an electrolyte, the adverse effects of the thinned region of the negative electrode active material layer can be compensated for, and the electrochemical device Specifically, the present invention provides a positive electrode, a negative electrode, and an electrolyte solution, which will be described below. In some embodiments, the electrochemical device further comprises: Further, it 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. The thickness D1 at any position in the first region is smaller than the average thickness D 2 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 <00…​​​​​​​​​​​​​​​​​​​​​​​​In some embodiments, the area of ​​the first region is 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 area of ​​the negative electrode active material. In some embodiments, the area of ​​the first region is less than 15% of the total area of ​​the matrix layer. In some embodiments, 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 negative electrode active material layer is 10% or less of the total area of ​​the negative electrode active material layer. The area of ​​the first region is 8% or less of the total area of ​​the negative electrode active material layer. The area of ​​the first region is 5% or less of the total area of ​​the negative electrode active material layer. The smaller the product, the higher the demands on the process and the higher the process costs. When the area of ​​the first region in the total area of ​​the negative electrode active material layer is within the above range, This effectively reduces the adverse effects of electrochemical oxidation without significantly increasing the cost of additional processes. The cycle characteristics of the device can be improved.

[0029] In some embodiments, the negative electrode active material layer includes a negative electrode active material. In this example, the negative electrode active material electrochemically absorbs and releases metal ions such as lithium ions. In some embodiments, the negative electrode active material is a carbonaceous material. , silicon carbon material, alloy material, and lithium-containing metal composite oxide material. Includes.

[0030] In some embodiments, the negative electrode active material has a median diameter of 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, 1 2 μm, 15 μm, 18 μm, or 20 μm, or any two of the foregoing values The "median diameter" is the particle size distribution of the negative electrode active material on a volume basis, It refers to the particle size at which the cumulative volume from the small particle size side is 50%, that is, the particle size smaller than the particle size in question. The volume of the negative electrode active material occupies 50% of the total volume of the negative electrode active material. When the content 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 comprises a negative electrode binder. In some embodiments, the negative electrode binder is a styrene butadiene rubber, a fluorine-based rubber, or a and ethylene propylene diene.

[0032] In some embodiments, the negative electrode active material layer further includes a negative electrode conductive agent. In some embodiments, the negative electrode conductive agent is a conductive metal material and a conductive polymer. In some embodiments, the negative electrode conductive agent may comprise one or more of a carbon material. In some embodiments, the carbon material may be graphite, carbon black, or a combination thereof. Examples of suitable fluororesin include, but are not limited to, acetylene black, acetylene black, and ketjen black.

[0033] In some embodiments, the negative electrode has a pressed density of 1.3 g / cm 3 ~1.8g / cm 3 In some embodiments, the negative electrode has a pressed density of 1.4 g / cm 3 ~1.6g / cm 3 In some embodiments, the negative electrode has a pressed density of 1.5 g / cm3 Yes do.

[0034] In some embodiments, the negative electrode current collector comprises a negative electrode conductive material. The negative electrode current collector may be made of, 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 is a negative electrode active material. In some embodiments, the roughened negative electrode current collector can improve adhesion of the material. Including, but not limited to, copper foil.

[0035] In some embodiments, the negative electrode current collector has a negative electrode active material layer on one surface thereof. In some examples, the negative electrode current collector has a negative electrode active material layer on each of its two surfaces. In some embodiments, a negative electrode active material layer is provided on at least one surface of the negative electrode current collector. It has an area where there is no foil, which is also called an empty foil area.

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

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

[0038] In some embodiments, the salt having a P-O bond is LiPO2F2, NaPO 2F2, KPO2F2, CsPO2F2, Lithium difluorobis(oxalato)phosphate and lithium difluorodioxalatophosphate (LIDODFP). nothing.

[0039] In some embodiments, 1 cm 2 Based on the first region of the In some embodiments, the amount of salt having a molecular weight of 1 cm is 0.04 g or less. 2 Current The content of the salt having a P-O bond is 0.03 g or less based on the first region per unit area. In some embodiments, 1 cm 2 Based on the first region per P- In some embodiments, the content of salts having O bonds is 0.02 g or less. 2 The content of the salt having a P-O bond is 0.01 g or more based on the first region per In some embodiments, 1 cm 2 Based on the first area of ​​the hit, The content of the salt having a P-O bond is 0.005 g or less. 1cm 2 The content of the salt having a P-O bond is 0.0 based on the first region per In some embodiments, the thickness is less than or equal to 1 cm. 2 Based on the first area The content of the salt having a PO bond is 0.0005 g or less.

[0040] When the electrochemical device is initially charged, salts with PO bonds preferentially collect on the negative electrode surface. , not only contributes to the formation of the second region of the negative electrode active material layer, but more importantly, This also contributes to the formation of the film in the first region, thereby improving the stability of the formed film and The occurrence of side reactions in the first region of the porous layer is reduced, and thickness changes due to by-products in the first region are reduced. The use of a salt having a PO bond also improves the cycle stability of the electrochemical device. By reducing the adverse effects of the difference in current distribution between the first and second regions of the negative electrode active material layer, This contributes to the effectiveness of film formation in the first region of the negative electrode active material layer. The inclusion of a salt having a P-O bond reduces the adverse effects of the thinned region of the negative electrode active material layer. This significantly improves the cycle characteristics of the electrochemical device.

[0041] In some embodiments, the electrolyte further comprises a first additive, When the reduction potential of the first additive is 2.5 V or less, the negative A protective layer can be formed on the electrode surface, which reduces the adverse effects of the thinned region of the negative electrode active material layer. This contributes to a significant improvement in the cycle characteristics of the electrochemical device.

[0042] In some embodiments, the first additive is 1,3-propane sultone (PS), Fluoroethylene carbonate (FEC), vinylene carbonate (VC), amber anhydride The solvent contains at least one of a maleic acid and maleic anhydride.

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

[0044] In some embodiments, the weight of the 1,3-propane sultone in the electrolyte solution The weight fraction is greater than the weight fraction of the fluoroethylene carbonate in the electrolyte. In some embodiments, the weight percentage of the 1,3-propane sultone in the electrolyte is The ratio of the weight fraction of the fluoroethylene carbonate in the electrolyte to the weight fraction of the fluoroethylene carbonate in the electrolyte is 1.5 or more. When the weight fraction ratio is within this range, the cycle characteristics of the electrochemical device can be improved. This also reduces the amount of gas generated by the electrochemical device.

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

[0046] In some embodiments, 1 cm 2 Based on the first region per In some embodiments, the amount of the agent is 0.001 g to 0.2 g. 2 Win Based on the first region, the content of the first additive is 0.005 g to 0.2 g. In some embodiments, 1 cm 2 Based on the first region per The content is 0.01 g to 0.15 g. In some embodiments, 1 cm 2 Before the hit Based on the first region, 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 The amount is 0.08 g to 0.1 g. In some embodiments, 1 cm 2 The first of the Based on the region, the content of the first additive is 0.001g, 0.005g, 0.01g, 0. 0.03g, 0.05g, 0.07g, 0.1g, 0.15g, or 0.2g; or The content of the first additive in the electrolyte solution is within the range consisting of any two of the above values. When the temperature is within this range, it contributes to further improving the cycle characteristics of the electrochemical device.

[0047] In some embodiments, the electrolyte further comprises a second additive, Lithium tetrafluoroborate (LiBF4), lithium bisfluorosulfonyl Lithium bis(trifluorosulfonyl)imide (LiFSI), lithium bis(trifluorosulfonyl)imide (LiTFSI), 4,5-Dicyano-2-trifluoromethylimidazole lithium (LiTDI), Lithium Lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalate) Borate, adiponitrile (ADN), succinonitrile, 1,3,6-hexanetrical nitrile (HTCN), 1,2,3-tris(2-cyanoxy)propane, 1,4-disiloxy A small amount of benzo-2-butene, glutaronitrile, and tris(2-cyanoethyl)phosphine In some embodiments, the second additive comprises at least one of LiBF4 and Li In some embodiments, the second additive comprises HTCN and LiDF In some embodiments, the second additive comprises LiBF and LiDF. In some embodiments, the second additive comprises HTC N, LiDFOB, and LiTFSI.

[0048] The second additive forms a protective layer on the surface of the positive electrode to reduce the occurrence of side reactions at the positive electrode, and It can reduce the elution of metal ions from the positive electrode. It also protects the negative electrode during the cycle process of electrochemical devices. The stability of the membrane is affected by the products of side reactions at the positive electrode. It protects the positive electrode and the negative electrode, improving the cycle characteristics of the electrochemical device. Contribute to improving it.

[0049] In some embodiments, the content of the second additive based on the weight of the electrolyte is The content of the second additive is 0.1 wt% to 10 wt% based on the weight of the electrolyte. In some embodiments, the amount is 0.2 wt % to 5 wt % based on the weight of the electrolyte. Based on this, the content of the second additive is 0.5 wt% to 3 wt%. The content of the second additive is 1 wt% to 2 wt% based on the weight of the electrolyte. In some embodiments, the content of the second additive is based on the weight of the electrolyte. The amounts are 0.1wt%, 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, or 10 wt%, or any of the foregoing When the content of the second additive in the electrolyte is within the above range, This contributes to further improving the cycle characteristics of the electrochemical device.

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

[0051] The solvent used in the electrolyte solution in the embodiment of the present invention is a cyclic carbonate, a chain carbonate, or the like. esters, 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, but Not limited.

[0052] In some embodiments, the cyclic carbonate is ethylene carbonate (EC), propane carbonate (P), or a mixture thereof. Including, but not limited to, propylene carbonate (PC) and butylene carbonate In some embodiments, the cyclic carbonate has 3 to 6 carbon atoms.

[0053] In some embodiments, the linear carbonate is dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate (DEC), methyl-n-propyl carbonate, Chain carbonates such as ethyl-n-propyl carbonate and di-n-propyl carbonate Examples of fluorine-substituted chain carbonates include bis(fluoromethyl)carbonate. nate, bis(difluoromethyl)carbonate, bis(trifluoromethyl)carbonate bis(2-fluoroethyl)carbonate, bis(2,2-difluoroethyl)carbonate carbonate, bis(2,2,2-trifluoroethyl)carbonate, 2-fluoroethylmethylcarbonate methyl carbonate, 2,2-difluoroethyl methyl carbonate, and 2,2,2-trifluoromethyl carbonate Including, but not limited to, fluoroethyl methyl carbonate.

[0054] In some embodiments, the cyclic carboxylic acid ester is selected from the group consisting of γ-butyrolactone and γ- In some embodiments, cyclic carbocyclic esters include, but are not limited to, valerolactone. A part of the hydrogen atoms of the carboxylic acid ester may be substituted with fluorine atoms.

[0055] In some embodiments, the chain carboxylic acid ester is methyl acetate, ethyl acetate, acetic acid, or the like. Propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, acetic acid t-Butyl propionate, methyl propionate, ethyl propionate, propyl propionate, Isopropyl pionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, iso Includes ethyl butyrate, methyl valerate, ethyl valerate, methyl pivalate, and ethyl pivalate In some embodiments, the hydrogen atom of the linear carboxylic acid ester may be substituted with a carboxylic acid ester. In some embodiments, a portion of the fluorine-substituted chain may be substituted with fluorine. The carboxylic acid esters are methyl trifluoroacetate, ethyl trifluoroacetate, trifluoroacetate, Propyl trifluoroacetate, butyl trifluoroacetate, and 2,2,2-trifluoroacetate Examples include, but are not limited to, fluoroethyl.

[0056] In some embodiments, the cyclic ether is tetrahydrofuran, 2-methyltetrahydrofuran, Hydrofuran, 1,3-dioxolane, 2-methyl-1,3-dioxolane, 4-methyl- 1,3-dioxolane, 1,3-dioxane, 1,4-dioxane, and dimethoxypropane Including but not limited to bread.

[0057] In some embodiments, the linear ether is dimethoxymethane, 1,1-dimethoxy Ethane, 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 solvent is trimethyl phosphate, triethyl phosphate, or the like. Dimethyl ethyl phosphate, Methyl diethyl phosphate, Ethylene methyl phosphate, Ethylene phosphate Ethylene ethyl, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, phosphite triphenyl, tris(2,2,2-trifluoroethyl) phosphate, and tris( 2,2,3,3,3-pentafluoropropyl).

[0059] In some embodiments, the sulfur-containing organic solvent is sulfolane, 2-methylsulfolane , 3-methylsulfolane, dimethylsulfone, diethylsulfone, ethylmethylsulfone , methyl propyl sulfone, dimethyl sulfoxide, methyl methanesulfonate, methane Ethyl sulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, sulfuric acid, Examples include, but are not limited to, diethyl ester, and dibutyl sulfate. In this case, some of the hydrogen atoms of the sulfur-containing organic solvent may be substituted with fluorine atoms.

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

[0061] In some embodiments, the solvent used in the electrolyte of the present invention may be one or more of the solvents described above. In some embodiments, the solvent used in the electrolyte of the present invention includes a cyclic Carbonates, chain carbonates, cyclic carboxylic acid esters, chain carboxylic acid esters, and combinations thereof. In some embodiments, the electrolytes of the present invention include The solvents are ethylene carbonate, propylene carbonate, diethyl carbonate, Ethyl pionate, propyl propionate, n-propyl acetate, ethyl acetate, and their In some embodiments, the present invention comprises an organic solvent selected from the group consisting of: The solvents used in the electrolyte are ethylene carbonate, propylene carbonate, diethylene carbonate, ethyl propionate, propyl propionate, γ-butyrolactone, and 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 material is not particularly limited and may be selected as needed.

[0063] In some embodiments, the positive electrode active material is a compound capable of absorbing and releasing lithium (Li). Examples of positive electrode materials that can absorb and release lithium (Li) include cobalt. Lithium oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminate Lithium manganese oxide, lithium iron manganese phosphate, lithium vanadium phosphate, phosphorus Lithium vanadyl oxide, lithium iron phosphate, lithium titanate, and lithium-rich manganese It may also contain silicon-based materials.

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

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

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

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

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

[0069] M3 is cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (F e), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (C a), strontium (Sr), niobium (Nb), tantalum (Ta), and tungsten (W), and the values ​​of z, g, and h are each 0. The ranges are 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 Alternatively, the coating may be mixed with another compound. oxides of the applied elements, hydroxides of the applied elements, oxyhydroxides of the applied elements, Oxycarbonates of the applied elements and hydroxycarbonates of the applied elements At least one selected from hydroxycarbonate The compounds used in the coating may include ammonia and other compounds of the two applied elements. The applied elements contained in the coating may be crystalline or amorphous. Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Z The positive electrode active material may contain r, F, and mixtures thereof, as long as they do not adversely affect the properties of the positive electrode active material. The coating may be formed by any method, for example, spraying, dispensing, or the like. The application method may include any application method known to those skilled in the art, such as slapping.

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

[0072] The binder strengthens the bond between the positive electrode active material particles and also strengthens the bond between the positive electrode active material and the current collector. Non-limiting examples of binders include polyvinyl alcohol, hydroxybenzoates, and the like. Dipropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated Polyvinyl chloride, polyvinyl fluoride, polyvinylpyrrolidone, polyurethane, poly Polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, Styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin , nylon, etc.

[0073] The positive electrode active material layer contains a positive electrode conductive material, which provides electrical conductivity to the electrode. Any conductive material may be included as long as it does not cause a chemical change. Examples include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene, etc.). black, ketjen black, carbon fiber, etc.), metallic materials (e.g., copper, nickel, metal powders and metal fibers containing zinc, 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 is made of aluminum (Al). may be used, but is not limited to this.

[0075] Separator In some embodiments, the electrochemical device of the present invention includes a separator between the positive electrode and the negative electrode. By providing this, it is possible to prevent short circuits of current caused by contact between the two pole pieces and also to prevent the lithium ion It can 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 the materials and shapes of the separators used in the electrochemical device of the present invention. The separator may be any of those disclosed in the art. In some embodiments, the separator is , a polymer (e.g., a synthetic resin) formed from a material that is stable against the electrolyte solution of the present invention. or inorganic materials (e.g., ceramics), etc. In some embodiments, the separator The electrode includes a porous membrane made of the polymer or the inorganic material. The separator includes a laminated membrane formed by laminating two or more types of porous membranes. In examples, the polymers include polytetrafluoroethylene, polypropylene, and polyethylene. This includes, but is not limited to, polyethylene.

[0077] In some embodiments, the separator is a porous membrane (substrate material layer) and a substrate. and a polymer compound layer provided on one or two surfaces of the plate material layer, thereby The separator improves the adhesion to the positive and negative electrodes, and prevents distortion when the electrode pieces are wound up. By suppressing the generation of electrolyte, the decomposition reaction of the electrolyte is suppressed, and leakage of the electrolyte that impregnates the substrate material layer is prevented. By using this separator, it is possible to suppress the Even in this case, the resistance of the electrochemical device does not increase significantly, and the expansion of the electrochemical device is suppressed. It is possible.

[0078] In some embodiments, the polymer layer comprises polyvinylidene fluoride; Polyvinylidene fluoride has excellent physical strength and electrochemical stability. The polymer compound layer is formed by preparing a solution in which a polymer material is dissolved, and then A method of applying a substrate material layer with a liquid or immersing the substrate material layer in a solution and then drying it. It may be formed.

[0079] use The electrochemical device of the present invention includes any device in which an electrochemical reaction occurs. Specific examples thereof include: This includes all types of primary and secondary batteries. In particular, the electrochemical device is Metal secondary batteries, lithium ion secondary batteries, lithium polymer secondary batteries, and lithium ion The present invention relates to a lithium secondary battery including a polyimide polymer secondary battery.

[0080] The use of the electrochemical device of the present invention is not particularly limited and can be used 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. , pen-input computers, mobile computers, e-book players, mobile phones Talking, portable fax machines, portable copiers, portable printers, stereo headsets, Video recorders, LCD TVs, portable cleaners, portable CD players, mini C D, walkie-talkies, electronic notebooks, calculators, memory cards, portable tape recorders readers, radios, backup power supplies, motors, automobiles, motorcycles, assisted bicycles, Bicycles, lighting equipment, toys, game consoles, clocks, power tools, flashlights, cameras, large household items It may be used in storage batteries and lithium ion capacitors, but Not limited to:

[0081] Example The following describes the characteristics of the lithium ion battery according to the present invention, as well as examples and comparative examples. Do the following.

[0082] 1. Preparation of Lithium-ion Battery Comparative Example 1 (1) Preparation of negative electrode The negative electrode active material is artificial graphite (median diameter 12.0 μm), the conductive material SuperP, and carbon Sodium hydroxymethylcellulose (CMC), styrene butadiene rubber as a binder (SBR) in a weight ratio of 96.4:1.5:0.5:1.6, and deionized water was added. The negative electrode slurry was then applied to a copper foil. It is coated evenly, dried at 85°C, and then cold rolled, die cut, slit and wound. After that, it was dried at 120°C under vacuum for 12 hours, and the length was 1544.0±5.0mm. A negative electrode having a width of 66.5±1.0 mm was obtained, and the total area of ​​the negative electrode active material layer on one side (based on one side) ) is 1544.0 x 66.5 = 102676 (mm 2 ) and is approximately 1027 cm 2 and , the compressed density of the negative electrode is 1.6 g / cm 3 It was.

[0083] According to the settings of the following comparative examples and examples, the viscosity of the negative electrode slurry was adjusted to apply different specifications. The distance from the coating die to the coating roll and the speed of the substrate on the conveyor belt were adjusted using a die. The width and area of ​​the first region of the negative electrode active material layer were adjusted and controlled by controlling the temperature.

[0084] In Table 1, the width of the first region corresponding to the area of ​​the first region in each comparative example and example is as follows: As shown in the table below. [Table A]

[0085] (2) Preparation of the positive electrode The positive electrode active material Li(Ni 0.8 Co 0.08 Mn 0.07 )Al 0.05O2, conductive agent Super-P and polyvinylidene fluoride were mixed in a mass ratio of 97:1.4:1.6 with N-methyl Mix with NMP (Non-Methylpyrrolidone) and stir evenly to obtain a positive copolymer with a solid content of 72 wt%. This positive electrode slurry was applied to an aluminum foil, dried at 85°C, and After cold rolling, die cutting, slitting and tab welding, the sheet is left in a vacuum at 85°C for 4 hours. After drying, a positive electrode was obtained.

[0086] (3) Preparation of electrolyte Ethylene carbonate (EC), propylene carbonate (PC) in a dry argon gas atmosphere Carbonate (PC), Ethyl methyl carbonate (EMC), Diethyl carbonate (DEC) The mixture was mixed in a mass ratio of EC:PC:DEC:EMC=15:25:50:10, and the results were compared with those in Examples. Following the example settings, add the additive, dissolve it, stir thoroughly, then add the lithium salt LiPF6. The mixture was mixed uniformly to obtain a base electrolyte with a LiPF6 concentration of 1.2 mol / L. .

[0087] According to the following comparative examples and examples, a salt having a PO bond was added to the base electrolyte, and the first additive The agent and / or the second additive were added to obtain an electrolyte solution.

[0088] (4) Preparation of separator A polyethylene (PE) film with a thickness of 7 μm is used, and a coating thickness of 3 μm is applied on top of it. As shown in the figure, the ratio of PVDF slurry and inorganic particles (sheet boehmite and Al2O3) was 70%. The separator was obtained by applying a slurry of 100% ethanol (1:30) to the substrate and drying it.

[0089] (5) Preparation of Lithium-ion Battery The obtained positive electrode, separator, and negative electrode are sequentially wound up to form a bare cell. The battery was placed on an outer foil, with the injection hole remaining. The electrolyte was poured into the injection hole, and the package and (Charge to 3.3V at a constant current of 0.02C, and to 3.6V at a constant current of 0.1C) After going through the process of determining the capacity, the lithium-ion battery (approximately 9.1 mm thick and 49 mm wide) is produced. mm and approximately 74 mm in length).

[0090] 2.Measurement method (1) Measurement method for cycle capacity retention rate and cycle thickness expansion rate of lithium-ion batteries The lithium-ion battery was placed in a 25°C incubator and left to stand for 30 minutes. The temperature became constant. The initial thickness H0 of the lithium-ion battery was measured. The battery was charged at a constant current of 1.0C until the voltage reached 4.2V, and then at a constant voltage of 4.2V. Discharge the battery at a constant current of 4C until the voltage reaches 2.8V. The first discharge capacity C0 is recorded as one charge-discharge cycle. The lithium-ion battery was subjected to 600 charge / discharge cycles using the charge / discharge tester, and the measurement was stopped. The discharge capacity C1 and thickness H1 of the lithium-ion battery after cycling were recorded.

[0091] The cycle capacity retention rate and cycle thickness expansion rate of a lithium-ion battery can be calculated using the following formula: I calculated it. Cycle capacity retention rate = C1 / C0 x 100% Cycle thickness expansion rate = (H1-H0) / H0 x 100%

[0092] (2) Method for measuring the thickness of the first and second regions of the negative electrode active material layer When the negative electrode active material layer has the structure shown in FIG. 2, the central axis of the length is taken as the cross section, and the center in the width direction is taken as the cross section. A cross section of 1 cm in length was selected and imaged using a digital microscope system (VHX-9 50F), measure the thickness of the negative electrode active material layer, randomly select 10 points, and calculate the total thickness of the negative electrode piece. Calculate the average value E0 and the average value E1 of the thickness of the current collector using the formula: D2 = (E0 - E1) / 2 Then, the thickness D2 of the second region of the negative electrode active material layer was calculated.

[0093] The central axis of the length is taken as the cross section, and 1 is taken at intervals of 0.1 mm from the edge region of the negative electrode active material layer. The negative electrode active material layer on any one side was measured from the surface away from the current collector. The thickness of the current collector surface that is in contact with the material layer is measured as D1, and the thickness is measured at five points. If all three of these satisfy D1>D2×97%, the edge of the negative electrode active material layer 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 defined as the width of the first region of the negative electrode active material layer. The above thickness measurements were made to an accuracy of 0.01 mm. The selection must 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, the cross section is defined along the central axis of the width, and the same as above is also defined along the central axis of the width. Measurement was carried out in a similar manner.

[0095] When the negative electrode active material layer has the structure shown in FIG. 4, the central axis of length and the central axis of width are Except for the cross section, the measurements were carried out in a manner similar to that described above.

[0096] (3) Method for measuring the content of salts having P-O bonds in electrolyte Discharge the lithium-ion battery at a rate of 0.2C until the voltage reaches 2.8V. The weight of the battery is measured as M0, and the tab and exterior are cut off to obtain a bare cell. The electrolyte is obtained by centrifuging the mixture, and the solution is analyzed by ion chromatography IC (type: Thermo The anion content in the electrolyte was measured using a Fischer AQUION. The relative content Q of salts with PO bonds in the centrifuged bare cells was obtained. The cells were immersed in dichloromethane (DMC) for 72 hours and then dried. The dried bare cells, tabs, and outer packaging were then The total mass of the device was measured and designated as M1. The P in the bare cell was calculated using the formula: (M0-M1) x Q. The mass of the salt having an -O bond was calculated. The mass of the salt having a PO bond was calculated as the first mass of the negative electrode active material layer. Divide by the total area of ​​1 area and calculate the quality of salt with PO bonds corresponding to the 1 area per unit area. amount was obtained.

[0097] The types of the first and second additives are ion chromatography IC (type: Thermof Fisher, AQUION) or gas chromatograph GC (model: Agilent 78 90A-5975C).

[0098] 3, Measurement results Table 1 shows the composition of the electrolyte solution and the first region of the negative electrode active material layer in each comparative example and example. The effect on the cycle characteristics of lithium-ion batteries is shown. The content of 1 additive per unit area is 1cm 2 Based on the first region per P- The weight of the salt having an O bond or the first additive is shown in Table 1. The total area of ​​the negative electrode active material layer on one side is 1027 cm 2 is.

[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 It can improve the cycle capacity retention rate of lithium-ion batteries and reduce their thickness expansion rate. The ion battery has a low cycle capacity retention rate and a high thickness expansion rate, which makes it difficult to meet usage needs. It is difficult.

[0101] As shown in Examples 1 to 13, the electrolyte was 0.05 g / cm 2 The following PO bonds are present: When the salt is contained, the cycle capacity retention rate of the lithium-ion battery is significantly improved, and the thickness As shown in Examples 34 to 37, the expansion coefficient can be significantly reduced. The salts having the above structure or combinations thereof can provide substantially the same effect.

[0102] As shown in Examples 14 to 20, the electrolyte is 0.001 to 0.2 g / cm 2 The first additive When the lithium ion battery further contains The expansion rate can be reduced.

[0103] As shown in Examples 21 to 27, the electrolyte solution contained 0.1 wt% to 10 wt% of the second additive. When further containing, the cycle capacity retention rate of the lithium ion battery is further improved, and the thickness As shown in Examples 28 to 33, the first additive and / or the second additive can reduce the expansion rate. When multiple agents are used in combination, the cycle capacity retention rate of lithium-ion batteries can be further improved. This allows the thickness expansion rate to 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, lithium ions can be easily transported. This can further improve the cycle capacity retention rate of the lithium battery and reduce its thickness expansion rate.

[0105] Table 2 shows the effect of the median diameter of the negative electrode active material on the cycle characteristics of lithium-ion batteries. The preparation methods of Examples 38 to 41 and Example 3 were almost the same, but the parameters shown in Table 2 were used. The data was different.

[0106] [Table 2]

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

[0108] Throughout the specification, the terms "some embodiments," "some embodiments," "one embodiment," "another," "another" and "another" are used interchangeably. Any reference to "one example," "example," "partial example," or "some examples" of the present invention is indicative of at least one example of the present invention. An embodiment or example may be modified without departing from the spirit or scope of the invention, without departing from the spirit or scope of the invention. Therefore, the phrases "a" and "b" appearing in various places throughout the specification are also used. In some embodiments, "in an embodiment," "in one embodiment," "in another embodiment," "in one example," "in a particular example," or "example" does not necessarily mean It is not intended to cite the same embodiment or example of the invention. , material, or property may be used in any suitable manner in one or more embodiments or examples. can be combined with.

[0109] While exemplary embodiments have been disclosed and described, those skilled in the art will recognize that the above-described embodiments do not limit the present invention. and does not depart from the technical idea, principle, and scope of the present invention. It should be understood that changes, substitutions, and alterations to the embodiments are possible.

Claims

1. 1. An electrochemical device comprising: a negative electrode and an electrolyte; The negative electrode is provided on a negative electrode current collector and on at least one surface of the negative electrode current collector. a negative electrode active material layer, the negative electrode active material layer including a first region and a second region, the first region the thickness D1 at any point of the second region is less than the average thickness D2 of the second region; and The electrolyte contains a salt having a P—O bond, and ２ Based on the first area of and the content of the salt having a P—O bond is 0.05 g or less. Electrochemical equipment.

2. D1 and D2 satisfy D1≦D2×97%. The electrochemical device of claim 1 .

3. The salt having a P—O bond is LiPO ２ F ２ , NaPO ２ F ２ , K.P.O. ２ F ２ , Cs P.O. ２ F ２ , lithium difluorobis(oxalato)phosphate, and tetrafluorooxaphosphate At least one lithium phosphate salt, The electrochemical device of claim 1 .

4. The electrolyte solution further includes a first additive, and the first additive is 1,3-propanesulfonate. Fluoroethylene carbonate, vinylene carbonate, succinic anhydride, and methyl anhydride containing at least one of leic acid, The electrochemical device of claim 1 .

5. 1 cm ２ Based on the first region per 0.2g, 5. The electrochemical device of claim 4.

6. The electrolyte solution further includes a second additive, and the second additive is lithium tetrafluoroborate. Lithium, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethane sulfonyl)imide, 4,5-dicyano-2-trifluoromethylimidazole lithium, Lithium difluoro(oxalato)borate, Lithium bis(oxalato)borate, Diponitrile, succinonitrile, 1,3,6-hexanetricarbonitrile, 1,2,3- Tris(2-cyanoxy)propane, 1,4-dicyano-2-butene, glutaronitrile and tris(2-cyanoethyl)phosphine, Based on the amount, the content of the second additive is 0.1 wt% to 10 wt%; The electrochemical device of claim 1 .

7. The first region is located at an edge of the negative electrode active material layer, and the width of the first region is 15 mm or more. Below, The electrochemical device of claim 1 .

8. the area of ​​the first region is 20% or less of the total area of ​​the negative electrode active material layer; The electrochemical device of claim 1 .

9. 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. μm, The electrochemical device according to any one of claims 1 to 8.

10. The electrochemical device according to any one of claims 1 to 9, electronic equipment.

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