Electrochemical device and electronic apparatus

Abstract

The present application relates to an electrochemical device and electronic device. The electrochemical device includes a battery cell and an electrolyte, wherein the electrolyte includes a lithium salt, an organic solvent, and an electrolyte additive, wherein the organic solvent includes a chain ester solvent, and the electrolyte additive includes a fluorine-containing compound and a boron-containing compound. The battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator. The electrochemical device satisfies 1≤A / (C+D)×B+100 / E≤4, where the mass percentage of the chain ester solvent to the organic solvent is A%, and the bonding area of ​​the positive electrode tail tape is Bdm. 2 , C is the mass percentage of fluorine-containing compounds in the electrolyte (C%), the mass percentage of boron-containing compounds in the electrolyte (D%), and before electrolyte injection, the total moisture content of the separator and negative electrode sheet in the battery cell is E ppm. The solution provided in this application can suppress the impact of electrolyte byproducts on the positive electrode finishing tape by improving the electrolyte formulation and coordinating the physical parameters of the positive electrode finishing tape, thereby maintaining the battery's good appearance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to an electrochemical device and an electronic device. BACKGROUND

[0002] The positive electrode tailing tape of a lithium ion battery is one of the important components of the battery. The positive electrode tailing tape can cover the end of the positive electrode sheet to prevent the positive electrode sheet burr from piercing the separator, so as to prevent the direct contact between the aluminum foil and the negative electrode, thereby effectively improving the safety of the battery. The PET tape is a commonly used positive electrode tailing tape. However, long-term high-temperature storage of the battery can cause the PET positive electrode tailing tape soaked in the electrolyte to wrinkle and fail, thereby causing the deformation of the battery and resulting in poor appearance.

[0003] In the related art, the wrinkle failure of the PET positive electrode tailing tape during high-temperature storage is generally prevented by improving the electrolyte resistance of the PET positive electrode tailing tape itself.

[0004] However, the above-mentioned improvement has high cost and low compatibility with commercial electrolyte. SUMMARY

[0005] To solve or partially solve the problems in the related art, the present application provides an electrochemical device and an electronic device, which can improve the formula of the electrolyte, and cooperatively improve the physical parameters of the positive electrode tailing tape to inhibit the influence of the electrolyte by-products on the positive electrode tailing tape, prevent the wrinkle failure of the positive electrode tailing tape during high-temperature storage, and maintain the good appearance of the battery.

[0006] The first aspect of the present application provides an electrochemical device, comprising a shell, an electric core arranged in the shell, and an electrolyte injected into the shell, wherein the electrolyte comprises a lithium salt, an organic solvent and an electrolyte additive, the organic solvent comprises a chain ester solvent, and the electrolyte additive comprises a fluorine-containing compound and a boron-containing compound; the electric core comprises a positive electrode sheet, a negative electrode sheet and a separator, the separator is located between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet comprises a positive electrode current collector, one side surface of the positive electrode current collector comprises a blank area and a filler area, the filler area is coated with a positive electrode active material layer, and the blank area is pasted with a positive electrode tailing tape between the filler area, and the positive electrode tailing tape faces the separator;

[0007] wherein the organic solvent, the electrolyte additive and the positive electrode tailing tape satisfy the following relationship:

[0008] 1≤A / (C+D)×B+100 / E≤4

[0009] In the formula, the mass percentage of the chain ester solvent in the organic solvent is A%, the pasting area of the positive electrode tailing tape is B dm 2C is the mass percentage of the fluorine-containing compound in the electrolyte, D is the mass percentage of the boron-containing compound in the electrolyte, and E is the total moisture content of the separator and the negative plate in the battery cell before the electrolyte is injected, in ppm.

[0010] As an optional embodiment, the fluorine-containing compound includes at least one of the following compounds:

[0011]

[0012]

[0013] As an optional embodiment, the boron-containing compound has the following structure:

[0014]

[0015] In the structure 2, R1, R2 and R3 are each independently selected from at least one of H atom, C1-C10 alkyl, C6-C20 aryl and cyano.

[0016] As an optional embodiment, the boron-containing compound includes at least one of the following compounds:

[0017]

[0018]

[0019] As an optional embodiment, the chain ester solvent includes at least one of diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, ethyl propionate, propyl propionate, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, methyl propionate, methyl butyrate, ethyl n-butyrate, methyl acrylate, ethyl acrylate; preferably, the chain ester solvent includes at least propyl propionate; and / or, the organic solvent further includes a cyclic ester solvent, and the cyclic ester solvent includes at least one of ethylene carbonate, propylene carbonate, γ-butyrolactone, sulfolane.

[0020] As an optional embodiment, the mass percentage of the organic solvent in the electrolyte is 20% to 80%.

[0021] As an optional embodiment, A is 20 to 80; and / or, B is 0.02 to 0.5; and / or, C is 1 to 25; and / or, D is 0.1 to 5; and / or, E is less than 120.

[0022] As an optional embodiment, A is 40 to 80; C is 5 to 25; and / or, D is 0.1 to 3.

[0023] As an optional embodiment, one end of the positive electrode tailing adhesive tape is attached in the filler area, the other end is attached in the blank area, and the area S of the positive electrode tailing adhesive tape attached in the blank area is greater than the area S attached in the filler area K The area S attached in the blank area is greater than the area S attached in the filler area T .

[0024] As an optional embodiment, 1.5S T ≤S K ≤2S T .

[0025] The second aspect of the present application provides an electronic device comprising the aforementioned electrochemical device.

[0026] The technical solutions provided by the present application can include the following beneficial effects:

[0027] The degradation of the positive electrode tailing tape in high-temperature storage (after) is related to whether the partial chain ester solvent (such as DMC) produces by-products, and whether the partial chain ester solvent produces by-products is related to the stability of the SEI film and the trace water content in the electrolyte. Further, the stability of the SEI film is related to the content of the fluorine-containing compound and the boron-containing compound, and the trace water content in the electrolyte is related to the total water content of the separator and the negative electrode sheet in the cell before liquid injection (since the positive electrode sheet uses an organic solvent, the water content can be ignored, and the negative electrode sheet and the separator use an aqueous solvent, which mainly determines the water content in the cell before liquid injection, so the water content in the cell before liquid injection is mainly related to the total water content of the separator and the negative electrode sheet). Therefore, controlling the content of the fluorine-containing compound and the boron-containing compound can maintain the stability of the SEI film, and controlling the total water content of the separator and the negative electrode sheet in the cell before liquid injection can reduce the trace water content in the electrolyte. The content of the fluorine-containing compound and the boron-containing compound needs to be matched with the content of the chain ester solvent and the pasting area of the positive electrode tailing tape, because when the content of the chain ester solvent is relatively high and the content of the fluorine-containing compound and the boron-containing compound is relatively low, it cannot effectively improve the stability of the SEI film, resulting in the electrochemical reaction of the chain ester solvent at the negative electrode to generate methanol lithium; when the content of the chain ester solvent is relatively low and the content of the fluorine-containing compound and the boron-containing compound is relatively high, it will increase the viscosity of the electrolyte and the film forming resistance, reduce the conduction efficiency of lithium ions, and deteriorate the kinetic performance of the battery. In addition, when the pasting area of the positive electrode tailing tape is relatively large, it will reduce the capacity of the battery; and when the content of the fluorine-containing compound and the boron-containing compound is relatively high, it will increase the viscosity of the electrolyte and cannot effectively prevent the positive electrode tailing tape from wrinkling. When the content of the chain ester solvent is relatively low, the pasting area of the positive electrode tailing tape is relatively small, and the content of the fluorine-containing compound and the boron-containing compound is relatively high, it will increase the viscosity of the electrolyte and the film forming resistance, reduce the conduction efficiency of lithium ions, and deteriorate the kinetic performance of the battery. Therefore, the inventors have found that when the organic solvent, the electrolyte additive and the positive electrode tailing tape satisfy 1≤A / (C+D)×B+100 / E≤4, the content of the fluorine-containing compound and the boron-containing compound can be matched with the content of the chain ester solvent, the content of the fluorine-containing compound and the boron-containing compound can be matched with the pasting area of the positive electrode tailing tape, and the trace water content in the electrolyte can be controlled, thereby effectively inhibiting the failure of the positive electrode tailing tape in high-temperature storage (after) and ensuring that the electrolyte has high ionic conductivity.

[0028] It should be understood that the general description above and the detailed description below are only exemplary and explanatory, and cannot limit the present application. BRIEF DESCRIPTION OF DRAWINGS

[0029] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description thereof taken in conjunction with the accompanying drawings, in which like reference characters designate like elements throughout the several views.

[0030] Figure 1 is a structural schematic diagram of a positive electrode sheet according to an embodiment of the present application.

[0031] In the figure, 1, positive electrode sheet; 10, positive electrode current collector; 11, positive electrode active material layer; 12, positive electrode end-tape; K, blank area; T, filler area; S K , area of the positive electrode end-tape in the blank area; S T , area of the positive electrode end-tape in the filler area. DETAILED DESCRIPTION

[0032] Embodiments of the present application will be described in more detail by referring to the drawings. Although the embodiments of the present application are shown in the drawings, it is understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that the present application will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0033] The terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used in the description of the application and the appended claims, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term "and / or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

[0034] It is to be understood that, although the terms "first", "second", "third", and so on can be employed in the present application to describe various information, these information are not limited to these terms. These terms are only used to distinguish one piece of information from another piece of information. For example, the first information can also be referred to as the second information, and similarly, the second information can also be referred to as the first information, without departing from the scope of the present application. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "a plurality of" is two or more, unless otherwise specifically limited.

[0035] The PET tape is a commonly used positive electrode tailing tape, but long-term high-temperature storage of the battery can cause the PET positive electrode tailing tape soaked in the electrolyte to wrinkle and fail, thereby causing deformation of the battery and resulting in poor appearance. In the related art, the wrinkle failure of the PET positive electrode tailing tape during high-temperature storage is generally prevented by improving the electrolyte resistance of the PET positive electrode tailing tape itself. However, the above scheme has high improvement cost and insufficient adaptability to commercial electrolyte.

[0036] To solve the above problems, the embodiments of the present application provide an electrochemical device, which can improve the formula of the electrolyte, and cooperates with the physical parameters of the positive electrode tailing tape to inhibit the influence of the electrolyte by-products on the positive electrode tailing tape, prevent the positive electrode tailing tape from wrinkling and failing during high-temperature storage, and maintain good appearance of the battery.

[0037] Referring to Figure 1 The embodiments of the present application provide an electrochemical device, which includes a shell, a battery cell arranged in the shell, and an electrolyte injected into the shell, the electrolyte including a lithium salt, an organic solvent and an electrolyte additive, the organic solvent including a chain ester solvent, the electrolyte additive including a fluorine-containing compound and a boron-containing compound; the battery cell includes a positive electrode sheet, a negative electrode sheet and a separator, the separator is located between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet 1 includes a positive electrode current collector 10, one side surface of the positive electrode current collector 10 includes a blank area K and a filler area T, the filler area T is coated with a positive electrode active material layer 11, and the blank area K and the filler area T are pasted with a positive electrode tailing tape 12, and the positive electrode tailing tape 12 faces the separator; wherein the organic solvent, the electrolyte additive and the positive electrode tailing tape satisfy the following relationship:

[0038] 1≤A / (C+D)×B+100 / E≤4

[0039] In the formula, the mass percentage of the chain ester solvent in the organic solvent is A%, the pasting area of the positive electrode tailing tape is B dm 2 , C is the mass percentage of the fluorine-containing compound in the electrolyte, which is C%, the mass percentage of the boron-containing compound in the electrolyte is D%, and the total moisture content of the separator and the negative electrode sheet in the battery cell before the electrolyte is injected is E ppm.

[0040] In the embodiments of the present application, the electrochemical device can be a battery, for example, a lithium ion battery, and the shell of the battery can be used to package the battery cell and the electrolyte. The shell of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. It can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate and polybutylene succinate, etc. can be listed. The present application does not have special restrictions on the shape of the battery, which can be cylindrical, square or any other shape.

[0041] The battery cell of the embodiment of the application can be formed by winding the positive electrode sheet, the negative electrode sheet and the separator. Specifically, the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence with the separator between the positive electrode and the negative electrode to play a separating role, and then the stacked electrode sheet and the separating film are wound to obtain the battery cell, wherein the positive electrode sheet, the separator and the negative electrode sheet are from inside to outside. The battery cell is placed in a shell, and the battery cell is baked to remove moisture, and then electrolyte is injected, and the lithium ion battery is obtained through processes such as vacuum packaging, standing, formation and shaping.

[0042] In the embodiment of the application, the positive electrode sheet includes a positive electrode current collector, the positive electrode current collector has two side surfaces a and b, both the a surface and the b surface have a filler area and a blank area, the filler area of the a surface is longer than that of the b surface, and the a surface is attached to the separator when the battery cell is prepared; the filler areas of the a surface and the b surface are coated with a positive electrode active material layer, and the blank area of the a surface is pasted with a positive electrode end tape between the filler areas, which can provide a positive electrode tail safety position and ensure that the negative electrode sheet at the tail of the wound core exceeds the positive electrode sheet in length and width. It can be ensured that the negative electrode can embed lithium ions from the positive electrode during the charging process, thereby avoiding the accumulation of lithium ions at the edge of the negative electrode and reducing the occurrence of lithium precipitation; on the other hand, the positive electrode end tape can wrap the upper and lower edges of the blank area to prevent the positive electrode blank foil edge burr from piercing the separator. The positive electrode end tape can be made of polypropylene (PP) material, polyimide (PI), polyethylene terephthalate (PET) and other materials. Preferably, it is made of polyethylene terephthalate (PET) material.

[0043] In the embodiment of the application, the type of the positive electrode current collector is not particularly limited, and it can be any known material suitable for use as a positive electrode current collector. In one embodiment, the positive electrode current collector includes aluminum, stainless steel, nickel plating, titanium, tantalum and other metal materials, as well as carbon cloth, carbon paper and other carbon materials. Preferably, the positive electrode current collector is a metal material.

[0044] In the embodiment of the application, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material is selected from at least one of lithium cobaltate, nickel-cobalt-manganese ternary material, lithium iron phosphate and lithium manganate. Preferably, the positive electrode material is lithium cobaltate or nickel-cobalt-manganese ternary material.

[0045] In a specific embodiment, the positive electrode active material layer further includes a conductive agent and a binder. The conductive agent includes at least one of natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, graphene and other carbon materials. The binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose and nitrocellulose.

[0046] The material and shape of the diaphragm are not particularly limited in the embodiments of the present application, and can include a porous sheet or non-woven fabric material having excellent liquid retention, and the like, a resin or glass fiber diaphragm material including but not limited to polyolefin, aromatic polyamide, polytetrafluoroethylene, polyether sulfone, and the like, which can be set as needed.

[0047] In the embodiments of the present application, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material coated on at least one side of the negative electrode current collector, and the negative electrode active material includes at least one of graphite, hard carbon, silicon, silicon oxide, and silicon carbide. Preferably, the negative electrode active material is silicon.

[0048] The present application does not limit the selection of the negative electrode current collector, which can be selected as needed, for example, a copper foil can be selected. The negative electrode active material layer of the present application includes a negative electrode active material and a binder, and the negative electrode active material includes a carbon material and a silicon material. The present application does not limit the selection of the carbon material, which can be selected as needed, for example, graphite, carbon black, hard carbon, soft carbon, and the like can be selected. The present application does not limit the selection of the silicon material, which can be selected as needed, for example, silicon oxide, pre-lithiated silicon oxide, pre-magnesiumized silicon oxide material, silicon-carbon composite material, elemental silicon, and the like can be selected. The binder of the present application includes a polypropylene compound and a butadiene rubber, and the polypropylene compound refers to a polypropylene derivative, for example, polyacrylic acid, polyacrylonitrile, polyacrylamide, poly(methyl acrylate), and the like.

[0049] Since dimethyl carbonate (DMC) and chain ester solvents similar in structure to DMC can generate lithium methoxide by electrochemical reaction at the negative electrode when the SEI film is unstable, and can also generate methanol by hydrolysis reaction with trace water in the electrolyte, these two by-products can catalyze the degradation of the positive electrode end tab adhesive tape, so the positive electrode end tab adhesive tape soaked in the electrolyte during high-temperature storage is prone to lose adhesion and wrinkle, resulting in battery deformation. The embodiments of the present application add fluorine-containing compounds as electrolyte additives, the fluorine element contained in the fluorine-containing compounds can reduce the energy level of the lowest occupied molecular orbital (LUMO) of the molecule, so that the fluorine-containing compounds will preferentially undergo reduction reaction at the negative electrode interface than other solvents and additives, establishing a stable SEI film, inhibiting the electrochemical decomposition of DMC and chain ester solvents similar in structure to DMC, and inhibiting the generation of catalysts that degrade the positive electrode end tab adhesive tape, so that the positive electrode end tab adhesive tape exhibits good electrolyte resistance, ensuring that the positive electrode end tab adhesive tape does not wrinkle during (after) high-temperature storage, maintaining the good appearance of the battery. However, the introduction of fluorine elements will reduce the ionic conductivity of the electrolyte. Based on this, the embodiments of the present application add boron-containing compounds as electrolyte additives to ensure that there are a large number of free Li+ in the electrolyte. Therefore, the synergistic effect of boron-containing compounds and fluorine-containing compounds can make the electrolyte and the negative electrode interface have good stability, while inhibiting the side reactions of chain ester solvents and the catalytic degradation effect of by-product on the positive electrode end tab adhesive tape.

[0050] Based on the above analysis, the degradation of the positive electrode tailing tape in high-temperature storage (after) is related to whether the chain ester solvent produces by-products, and whether the chain ester solvent produces by-products is related to the stability of the SEI film and the trace water content in the electrolyte. Further, the stability of the SEI film is related to the content of fluorine-containing compounds and boron-containing compounds, and the trace water content in the electrolyte is related to the total water content of the separator and the negative electrode sheet in the battery before liquid injection (since the positive electrode sheet uses an organic solvent, the water content can be ignored, and the negative electrode sheet and the separator use an aqueous solvent, which mainly determines the water content in the battery before liquid injection, so the water content in the battery before liquid injection is mainly related to the total water content of the separator and the negative electrode sheet). Therefore, controlling the content of fluorine-containing compounds and boron-containing compounds can maintain the stability of the SEI film, and controlling the total water content of the separator and the negative electrode sheet in the battery before liquid injection can reduce the trace water content in the electrolyte. The content of fluorine-containing compounds and boron-containing compounds needs to be matched with the content of chain ester solvents and the pasting area of the positive electrode tailing tape, because when the content of chain ester solvents is high and the content of fluorine-containing compounds and boron-containing compounds is relatively low, it cannot effectively improve the stability of the SEI film, resulting in the electrochemical reaction of chain ester solvents at the negative electrode to generate methanol lithium; when the content of chain ester solvents is low and the content of fluorine-containing compounds and boron-containing compounds is relatively high, it will increase the viscosity of the electrolyte and the film forming resistance, reduce the conduction efficiency of lithium ions, and worsen the kinetic performance of the battery. In addition, when the pasting area of the positive electrode tailing tape is large and the content of fluorine-containing compounds and boron-containing compounds is relatively low, it will reduce the capacity of the battery; when the pasting area of the positive electrode tailing tape is small and the content of fluorine-containing compounds and boron-containing compounds is relatively high, it will increase the viscosity of the electrolyte and cannot effectively prevent the positive electrode tailing tape from wrinkling. Therefore, the inventors have found that when the organic solvent, electrolyte additives and positive electrode tailing tape satisfy 1≤A / (C+D)×B+100 / E≤4, the content of fluorine-containing compounds and boron-containing compounds can be matched with the content of chain ester solvents, the content of fluorine-containing compounds and boron-containing compounds can be matched with the pasting area of the positive electrode tailing tape, and the trace water content in the electrolyte can be controlled, thereby effectively inhibiting the failure of the positive electrode tailing tape in high-temperature storage (after) and ensuring that the electrolyte has high ionic conductivity.

[0051] As an optional embodiment, the fluorine-containing compound includes at least one of the following compounds:

[0052]

[0053]

[0054] In the embodiments of the present application, the compounds 1-1 to 1-7 belong to fluorinated cyclic carbonate compounds, the compounds 1-8 to 1-10 belong to fluorinated sultone compounds, and the compounds 1-12 to 1-14 belong to fluorinated linear carbonate compounds. These compounds can preferentially undergo reduction reactions at the negative electrode interface in preference to other solvents and additives, and can establish a stable SEI film, inhibit lithium precipitation at the negative electrode, inhibit the electrochemical decomposition of DMC and other chain ester solvents similar in structure, and inhibit the generation of catalysts that degrade the positive electrode end tab, so that the positive electrode end tab exhibits good electrolyte resistance, and ensures that the positive electrode end tab does not wrinkle during (after) high-temperature storage, and maintains good appearance of the battery.

[0055] As an optional embodiment, the structure of the boron-containing compound is as follows:

[0056]

[0057]

[0058] In the structure 2, R1, R2 and R3 are each independently selected from at least one of an H atom, a C1-C10 alkyl group, a C6-C20 aryl group and a cyano group.

[0059] Preferably, the boron-containing compound includes at least one of the following compounds:

[0060]

[0061] In the embodiments of the present application, the compounds 2-1 to 2-6 belong to borate compounds, which are beneficial to consume HF generated by electrolyte decomposition, and form a SEI protective layer containing B-O-F structure on the negative electrode surface. In addition, the borate compound can also form a uniform and thin CEI layer on the positive electrode side, which can further effectively reduce the dissolution of transition metal ions.

[0062] As an optional embodiment, the chain ester solvent includes at least one of diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), ethyl propionate (EP), propyl propionate (PP), methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, methyl propionate (MP), methyl butyrate, ethyl n-butyrate, methyl acrylate, and ethyl acrylate.

[0063] Preferably, the chain ester solvent includes at least propyl propionate. That is, the chain ester solvent includes only propyl propionate, or includes propyl propionate and other chain ester solvents listed above. Propyl propionate has good compatibility with the negative electrode and is not prone to oxidative decomposition, and thus is not prone to generate catalysts that degrade the positive electrode end tab.

[0064] As an optional embodiment, the organic solvent further comprises a cyclic ester solvent, and the cyclic ester solvent comprises at least one of ethylene carbonate (EC), propylene carbonate (PC), gamma-butyrolactone, and sulfolane.

[0065] As an optional embodiment, the mass percentage of the organic solvent in the electrolyte is 20% to 80%.

[0066] In the embodiments of the present application, the mass percentage of the organic solvent in the electrolyte can be 20%, 40%, 60%, 80%, or any value within the above range, which is not limited in the present application.

[0067] Preferably, the mass percentage of the chain ester solvent in the organic solvent is 20% to 80%.

[0068] In the embodiments of the present application, the mass percentage of the chain ester solvent in the organic solvent can be 20%, 40%, 60%, 70%, 80%, or any value within the above range, which is not limited in the present application.

[0069] As an optional embodiment, A is 20 to 80.

[0070] In the embodiments of the present application, the mass percentage of the chain ester solvent in the organic solvent is A%, and A can be 20%, 40%, 60%, 70%, 80%, or any value within the above range, which is not limited in the present application.

[0071] Preferably, the chain ester solvent at least comprises propyl propionate. By controlling the chain ester solvent to comprise propyl propionate and the content to be within the above range, the embodiments of the present application can maintain the solvent to have good stability and not to easily produce gas after high-temperature storage.

[0072] As a preferred embodiment, A is 60 to 80.

[0073] Preferably, when the chain ester solvent is propyl propionate, the mass percentage of the propyl propionate in the organic solvent is 60% to 80%.

[0074] As an optional embodiment, B is 0.02 to 0.5.

[0075] In the embodiments of the present application, the width of the positive electrode tailing adhesive tape is generally 5 mm to 25 mm, and the length of the positive electrode tailing adhesive tape is equivalent to the length of the positive electrode sheet. The length of the positive electrode sheet is different for different battery cell models, and is generally 40 mm to 200 mm. According to experience, the area of the positive electrode tailing adhesive tape is generally 0.02 dm 2 ~-0.5 dm 2 The area of the positive electrode tailing adhesive tape within the range can be applied to most models of battery cells.

[0076] In the use of the positive electrode tailing adhesive tape, it is not that the larger the pasting area is, the better. If the pasting area is too large, the capacity of the battery will be reduced; if the pasting area is too small, the positive electrode tailing adhesive tape cannot play its role. Therefore, the application embodiment controls the pasting area to be in the above range, so that the positive electrode tailing adhesive tape can fully play its role.

[0077] As an optional embodiment, C is 1-25.

[0078] In the application embodiment, the mass percentage of the fluorine-containing compound in the electrolyte is C%, and C can be 1, 5, 10, 15, 20, 25 or any value in the above range, which is not limited by the application. If the content of the fluorine-containing compound is too large, the viscosity of the electrolyte will increase, the conduction rate of lithium ions will decrease, the kinetics will be deteriorated, or gas will be easily produced, which will affect the cycle and safety performance of the battery; if the content of the fluorine-containing compound is too low, a stable SEI film cannot be formed. Therefore, the application embodiment controls the content of the fluorine-containing compound in the above range, so that the fluorine-containing compound can effectively play its role.

[0079] As a preferred embodiment, C is 5-25.

[0080] In the application embodiment, C can be 5, 10, 15, 20, 25 or any value in the above range, which is not limited by the application. When C is in the above limited range, the high-temperature cycle performance of the battery can be further improved.

[0081] As an optional embodiment, D is 0.1-5.

[0082] In the application embodiment, the mass percentage of the boron-containing compound in the electrolyte is D%, and D can be 0.1, 1, 3, 5 or any value in the above range, which is not limited by the application. If the content of the boron-containing compound is too large, the impedance of the formed film will be too large, which will affect the kinetic performance of the battery; if the content of the boron-containing compound is too low, the dissociation of lithium salt will be affected, and the conduction rate of lithium ions will be reduced. Therefore, the application embodiment controls the content of the boron-containing compound in the above range, so that the fluorine-containing compound can effectively play its role.

[0083] As a preferred embodiment, D is 0.1-3.

[0084] In the application embodiment, D can be 0.1, 1, 3 or any value in the above range, which is not limited by the application. When D is in the above limited range, a synergistic effect can be further played, and the high-temperature cycle performance of the battery can be improved.

[0085] As an optional embodiment, E<120.

[0086] In the embodiments of the present application, the total moisture content of the separator and the negative plate in the battery cell before the electrolyte is injected is Eppm, E can be 110, 100, 90, etc., as long as E<120, which is not limited in the present application.

[0087] As an optional embodiment, A is 20-80, B is 0.02-0.5, C is 1-25, D is 0.1-5, and E<120.

[0088] Since lithium hexafluorophosphate in the electrolyte is prone to hydrolysis, the electrolyte needs to be baked before being injected into the dry battery cell to control the moisture content in the dry battery cell. The total moisture content of the separator and the negative plate can be tested to determine whether the dry battery cell meets the injection condition. When E<120, the injection condition is met.

[0089] As a preferred embodiment, A is 60-80, B is 0.02-0.5, C is 5-25, D is 0.1-3, and E<120.

[0090] As an optional embodiment, referring to Figure 1 As shown in the figure, one end of the positive electrode end tape 12 is pasted in the filler area T, and the other end is pasted in the blank area K, and the area S K pasted by the positive electrode end tape 12 in the blank area K is greater than the area S T pasted in the filler area T.

[0091] The embodiments of the present application can control the area S K pasted by the positive electrode end tape 12 in the blank area K to be greater than the area S T pasted in the filler area T, so that the lithium ion extraction in the positive electrode active material in the filler area is not affected, and the lithium precipitation at the junction between the tail filler area and the blank area is prevented, and the capacity of the battery is not affected.

[0092] As a preferred embodiment, referring to Figure 1 As shown in the figure, the area pasted by the positive electrode end tape in the blank area is S K , the area pasted in the filler area is S T , 1.5S T ≤S K ≤2S T .

[0093] The area pasted by the positive electrode end tape in the blank area is not the larger the better, and the area pasted in the filler area is not the smaller the better, when 1.5S T ≤S K ≤2S T , there is enough safety margin, and the capacity of the battery is not affected.

[0094] In the embodiments of the present application, the lithium salt includes one or more of lithium hexafluorophosphate LiPF6, lithium difluoro(oxalato)borate LiODFB, lithium difluorodioxalate phosphate LiDFOP, lithium tetrafluoroborate LiBF, lithium bis(trifluoromethylsulfonyl)imide LiTFSI, lithium bis(fluorosulfonyl)imide LiFSI, and lithium difluorophosphate LiPOF2, and the lithium salt accounts for 10-30% of the mass percentage of the electrolyte.

[0095] In the embodiments of the present application, the electrolyte additive further includes other additives, which include but are not limited to several of vinylene carbonate VC, 1,3-propane sultone PS, vinyl sulfate DTD, succinonitrile SN, adiponitrile ADN, 1,3,6-hexanetricarbonitrile HTCN, propene sultone PST, methanemalonate MMDS, ethylene glycol bis(propionitrile) ether EGBE, pentafluoroethoxy phosphazene, dicyclohexyl carbonyl, phosphoric acid trimethyl imide, hexamethylene diisocyanate, etc.

[0096] In the embodiments of the present application, the electrolyte additive accounts for 5-35% of the mass percentage of the electrolyte.

[0097] The embodiments of the present application also provide an electronic device comprising the aforementioned electrochemical device.

[0098] For example, the above-mentioned power consuming device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0099] In order to further understand the present application, the present application is described below in conjunction with the embodiments, which are only used to illustrate the present application and do not limit the scope of the present application.

[0100] I. Preparation of the battery

[0101] (1) Preparation of the electrolyte

[0102] The chain ester solvent and the cyclic ester solvent are mixed according to the mass ratio in Table 1 as the organic solvent, wherein the organic solvent accounts for 75% of the mass percentage of the electrolyte, and the chain ester solvent accounts for the mass percentage of the organic solvent according to Table 1. Then LiPF6 is added to obtain a mixed solution with a LiPF6 concentration of 1.1 mol / L, and then the first additive and the second additive, 4% of succinonitrile SN and 4% of 1,3-propane sultone PS are added to the mixed solution according to Table 1 to prepare the electrolyte of each embodiment and the comparative example.

[0103] (2) Preparation of the positive electrode sheet:

[0104] Lithium nickel manganese cobalt ternary positive electrode active material, conductive agent CNT, and binder polyvinylidene fluoride were mixed in a weight ratio of 97:1.5:1.5 in an N-methylpyrrolidone solvent, and stirred sufficiently to form a uniform positive electrode slurry. The slurry was coated on the a surface of a positive electrode current collector aluminum foil, and on the filler area of the b surface of the positive electrode current collector aluminum foil, and a positive electrode end tape was pasted between the filler area and the blank area of the b surface, with the pasting area being set according to Table 1. After drying, cold pressing, the positive electrode sheet of each example and the comparative example was obtained.

[0105] (3) Preparation of negative electrode sheet:

[0106] The negative electrode active material graphite, conductive agent acetylene black, binder styrene butadiene rubber, and thickening agent sodium carboxymethyl cellulose were mixed in a mass ratio of 95:2:2:1 in a proper amount of deionized water solvent, and stirred sufficiently to form a uniform negative electrode slurry. The slurry was coated on a negative electrode current collector Cu foil, dried, and cold pressed to obtain a negative electrode sheet.

[0107] (4) Preparation of lithium ion battery:

[0108] The positive electrode sheet, separator, and negative electrode sheet were stacked in order, with the separator being between the positive electrode and the negative electrode to play a separation role, and then the bare cell was wound. The bare cell was placed in a shell, the cell was baked at 80°C, the total moisture content of the separator and the negative electrode sheet in the cell was controlled according to Table 1, the electrolyte of each example and the comparative example was injected into the dried cell, and the lithium ion battery was prepared after vacuum packaging, standing, formation, shaping, and other processes.

[0109] Table 1 Formulation and relationship table

[0110]

[0111]

[0112]

[0113]

[0114]

[0115] II. Performance test

[0116] 1. 0°C negative electrode lithium precipitation: 0.2C discharge to 3V at 25°C, then 0°C standing for 3H, 0.34C constant current and constant voltage charging to 4.53V, with a cutoff current of 0.05C, then 0.5C discharging to 2.8V, repeating the cycle for 50cls, and disassembling the full battery to observe the lithium precipitation state of the negative electrode interface.

[0117] 2. 60℃ storage 28D performance: the cell is charged to 4.53V at 0.5C constant current, the cutoff current is 0.05C, and it is rested for 10min, the full charge thickness D0 is tested, the battery is stored at 60±2℃ open circuit full charge for 28D, and the hot state thickness D1 is tested immediately after unpacking. Thickness change rate = D1 / D0-1.

[0118] 3. 60℃ storage 28D appearance test: observe whether the battery produces gas and whether the positive electrode end tape (referred to as tape) is corrugated (wrinkled).

[0119] The performance of each of the above examples and comparative examples is tested, and the test results are shown in Table 2.

[0120] Table 2 test results

[0121]

[0122]

[0123] According to the data in Table 1 and Table 2, by comparing Example 1 to Example 14, and Example 17 to Example 21, it can be known that when the fluorine-containing compound and the boron-containing compound provided in the examples of the present application are used, and 1≤A / (C+D)×B+100 / E≤4 is met, the failure of the positive electrode end tape in the (later) high-temperature storage can be effectively inhibited, and the electrolyte can also have a high ionic conductivity.

[0124] By comparing Example 14 and Example 40, it can be known that replacing PP with EP will cause the battery to produce gas, affecting the safety performance of the battery; by comparing Example 14 and Example 41, it can be known that EP+PP has a synergistic effect, which can improve the safety performance of the battery; by comparing Example 14 and Example 42, replacing PP with DMC will cause the battery to produce gas, affecting the safety performance of the battery; by comparing Example 41 and Example 43, DMC+PP also has a synergistic effect, which can improve the safety performance of the battery; further combined with Example 44, it can be known that the synergistic effect of DMC+EP is not as good as that of EP+PP and DMC+PP, therefore, the chain-like ester solvent obtained in the examples of the present application preferably contains at least PP.

[0125] By comparing each example and comparative example, and combining Example 39 and Comparative Example 14, it can be known that when 1≤A / (C+D)×B+100 / E≤4 is met, the failure of the positive electrode end tape in the (later) high-temperature storage can be effectively inhibited, and the electrolyte can also have a high ionic conductivity.

[0126] While the application has been described with reference to the preferred embodiments, it will be understood by those skilled in the art that various changes can be made and equivalents can be substituted for elements thereof without departing from the scope of the application. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the application without departing from the central scope of the application. Therefore, the application is not intended to be limited to the particular embodiments disclosed as the best mode contemplated for carrying out the application, but it is intended to cover in the appended claims all embodiments falling within the scope of the application.

[0127] All ranges disclosed herein are inclusive of the endpoints, and the endpoints are combinable with each other.

[0128] Embodiments of the application have been described above, with the understanding that these embodiments are exemplary, but are not exhaustive, and are not limited to the embodiments disclosed. Many modifications and variations of the described embodiments will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms to be used in the description is not intended to limit the scope or breadth of the embodiments disclosed herein. Rather, the terms are chosen to best explain the principles of the embodiments, practical application, or improvement over the technology in the art, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An electrochemical device, characterized by, The battery includes a shell, an electric core arranged in the shell, and an electrolyte injected into the shell, the electrolyte including a lithium salt, an organic solvent, and an electrolyte additive, the organic solvent including a chain ester solvent, the electrolyte additive including a fluorine-containing compound and a boron-containing compound; the electric core includes a positive electrode sheet, a negative electrode sheet, and a separator, the separator being located between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet including a positive electrode current collector, one side surface of the positive electrode current collector including a blank area and a filler area, the filler area being coated with a positive electrode active material layer, and a positive electrode end adhesive tape being pasted between the blank area and the filler area, the positive electrode end adhesive tape facing the separator. Wherein, the following relationship is satisfied between the organic solvent, the electrolyte additive, and the positive electrode end adhesive tape: 1≤A / (C+D)×B+100 / E≤4 Wherein, the mass percentage of the chain ester solvent to the organic solvent is A%, and the pasting area of ​​the positive electrode tail tape is B dm 2 , C is the mass percentage of the fluorine-containing compound in the electrolyte is C%, the mass percentage of the boron-containing compound in the electrolyte is D%, and before injecting the electrolyte, the total moisture content of the separator and the negative electrode sheet in the battery cell is E ppm.

2. The electrochemical device of claim 1, wherein The fluorine-containing compound includes at least one of the following compounds: Compound 1-1 Compound 1-2 Compound 1-3 Compound 1-4 Compound 1-5 Compound 1-6 Compound 1-7 Compound 1-8 Compound 1-9 Compound 1-10 Compound 1-11 Compound 1-12 Compound 1-13 Compound 1-14.

3. The electrochemical device of claim 1, wherein The boron-containing compound has the following structural formula: Structural formula 2 In structural formula 2, R1, R2, and R3 are each independently selected from at least one of an H atom, a C1-C10 alkyl group, a C6-C20 aryl group, and a cyano group.

4. The electrochemical device of claim 3, wherein The boron-containing compound includes at least one of the following compounds: Compound 2-1 Compound 2-2 Compound 2-3 Compound 2-4 Compound 2-5 Compound 2-6.

5. The electrochemical device of claim 1, wherein The chain ester solvent includes at least one of diethyl carbonate, methyl ethyl carbonate, dimethyl carbonate, ethyl propionate, propyl propionate, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, methyl propionate, methyl butyrate, ethyl n-butyrate, methyl acrylate, and ethyl acrylate.

6. The electrochemical device of claim 5, wherein, The chain ester solvent at least includes propyl propionate; and / or, the organic solvent further includes a cyclic ester solvent, the cyclic ester solvent including at least one of ethylene carbonate, propylene carbonate, γ-butyrolactone, and sulfolane.

7. The electrochemical device of claim 1, wherein The mass percentage of the organic solvent in the electrolyte is 20% to 80%.

8. The electrochemical device according to any one of claims 1 to 7, wherein A is 20 to 80; and / or, B is 0.02 to 0.5; and / or, C is 1 to 25; and / or, D is 0.1 to 5; and / or, E is less than 120.

9. The electrochemical device of claim 8, wherein, A is 40 to 80; C is 5 to 25; and / or, D is 0.1 to 3.

10. The electrochemical device of claim 1, wherein One end of the positive electrode end-taping tape is attached in the filler region, the other end is attached in the blank region, and the area S of the positive electrode end-taping tape attached in the blank region K greater than the area S attached in the filler region T .

11. The electrochemical device of claim 10, wherein, 1.5S T ≤S K ≤2S T .

12. An electronic device, comprising: The electrochemical device includes any one of the batteries according to claims 1 to 11.

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