High-voltage fast-charging electrolyte as well as preparation method and application thereof

Abstract

The invention discloses a high-voltage fast-charging electrolyte and a preparation method and application thereof, the electrolyte comprises an electrolyte lithium salt, an organic solvent and an additive, the organic solvent comprises a carbonic ester organic solvent and a carboxylic ester organic solvent, and the additive comprises a film-forming additive, a resistance-reducing additive and a high-voltage additive; wherein the mass content of the film-forming additive is recorded as W1, the mass content of the resistance-reducing additive is recorded as W2, and the mass content of the carboxylic ester organic solvent is recorded as Ws by taking the electrolyte as a reference, so that W1 / Ws is more than or equal to 0.003 and less than or equal to 0.125; and / or 0.01 < = W2 / Ws < = 0.25. The formula composition and the content of the electrolyte are optimally designed, and the fast charging performance of the battery under high voltage is greatly improved through the synergistic effect of the solvent and the additive; in addition, the electrolyte is good in interface stability, and the overall performance of the battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of secondary batteries, and in particular relates to a high-voltage fast-charging electrolyte and a preparation method and application thereof. Background Art

[0002] Secondary batteries, also known as rechargeable batteries, are batteries that can restore their electrical energy storage capacity through a charging process. They are widely used in portable electronic devices, electric vehicles, energy storage systems and other fields. The core advantage of secondary batteries is their reusability, which reduces the environmental impact of disposable batteries. At present, the most common and most promising type of secondary batteries on the market is mainly lithium-ion batteries, which have the advantages of high energy density, long cycle life and low self-discharge rate.

[0003] In order to make lithium-ion batteries have higher energy density, longer cycle life, faster charging capacity and wider operating temperature range, it is generally achieved by optimizing or improving the key materials of lithium-ion batteries (such as positive electrode, negative electrode, separator and electrolyte). For example, in the prior art, the fast charging ability of the battery is effectively improved by adding carboxylic acid ester organic solvents to the electrolyte. On the other hand, for improving the energy density of lithium-ion batteries, increasing the charging cut-off voltage of the battery is an effective method. However, there are certain obstacles to achieving high energy density and fast charging capability at the same time. This is because at a high cut-off voltage (generally not less than 4.3V), the electrolyte is prone to continuous oxidative decomposition, uneven positive electrode-electrolyte interface (CEI) overgrowth and slow interface dynamics. These problems hinder the realization of high-voltage fast charging technology.

[0004] In addition, the surface of some high-specific-capacity negative electrodes (such as silicon negative electrodes) is prone to repeated cracking and crushing. The traditional fast-charge electrolyte continuously decomposes and reacts on its surface, which will cause the electrolyte to dry up and the capacity to drop sharply. At the same time, under high voltage conditions, the electrolyte is prone to oxidation reaction on the surface of the oxide positive electrode, generating HF and other substances that corrode the positive electrode material. In addition, the traditional carbonate-based electrolyte is Li-ion at low temperature or high rate conditions. + The strong interaction with carbonates makes the desolvation process difficult, forming a highly polarized interface, leading to a decrease in battery capacity or the formation of lithium dendrites.

[0005] For the above reasons, there is an urgent need to develop an electrolyte that has both high voltage and fast charging capabilities and can improve the compatibility of the electrolyte with the electrode, so as to solve the problems of oxidative decomposition, drying up, capacity decay and interface polarization existing in high voltage or fast charging electrolytes in the existing technology. Summary of the invention

[0006] In view of this, the primary purpose of the present invention is to provide a high-voltage fast-charging electrolyte. By optimizing the formula composition and content of the electrolyte, an electrolyte with both high voltage and fast charging capabilities is obtained, which can improve the compatibility of the electrolyte with the electrode.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] A first aspect of the present invention provides a high-voltage fast-charge electrolyte, which includes an electrolyte lithium salt, an organic solvent and an additive, wherein the organic solvent includes a carbonate organic solvent and a carboxylate organic solvent, and the additive includes a film-forming additive, a resistance-reducing additive and a high-voltage additive.

[0009] The second aspect of the present invention provides a method for preparing the high voltage fast charge electrolyte as described in the first aspect of the present invention, comprising the following steps:

[0010] preparing a basic electrolyte, wherein the basic electrolyte is obtained by uniformly mixing an electrolyte lithium salt and an organic solvent;

[0011] After adding a film-forming additive, a resistance-reducing additive and a high-voltage additive to the basic electrolyte respectively and fully dissolving them, a high-voltage fast-charging electrolyte is obtained.

[0012] The third aspect of the present invention provides the use of the high voltage fast charging electrolyte as described in the first aspect of the present invention in the preparation of a lithium ion battery.

[0013] A fourth aspect of the present invention provides a lithium-ion battery comprising the high-voltage fast-charge electrolyte described in the first aspect of the present invention.

[0014] In the present invention, by adding a certain amount of carboxylate solvents to the electrolyte system, the carboxylate solvents can significantly increase the conductivity of the electrolyte and reduce the viscosity of the system, thereby improving the rate performance of the battery; however, the carboxylate solvents will significantly deteriorate the battery cycle and storage bloating performance, and have a destructive effect on the negative electrode structure. At the same time, the SEI film component LiF content is low, and the compatibility with the negative electrode is poor. Therefore, the present application simultaneously adds a certain amount of film-forming additives, resistance-reducing additives, and high-voltage additives to the system, so that these additives and carboxylate solvents work together to enable the electrolyte to simultaneously form a stable negative electrode SEI film and a positive electrode CEI film, thereby achieving high-voltage fast charging performance and stable circulation under high voltage.

[0015] In the present invention, the ratio of each component in the electrolyte is specifically optimized by taking both cost and performance into consideration, wherein, based on the electrolyte as a reference, the mass content of the film-forming additive is denoted as W1, the mass content of the resistance-reducing additive is denoted as W2, the mass content of the high-voltage additive is denoted as W3, and the mass content of the carboxylic acid ester organic solvent is denoted as Ws.

[0016] In some specific embodiments of the present invention, 0.003≤W1 / Ws≤0.125; and / or 0.01≤W2 / Ws≤0.25 are satisfied, wherein 0.5%≤W1≤5%, and / or 0.5%≤W2≤5%, and / or 0.5%≤W3≤5%.

[0017] In some preferred embodiments of the present invention, 20%≤Ws≤50%, and / or 0.5%≤W1≤2%, and / or 0.5%≤W2≤3%, and / or 0.5%≤W3≤2% are satisfied.

[0018] By selecting the ratio and regulating the electrolyte solvation structure, the oxidation / reduction stability of the electrolyte is improved, and the compatibility of the electrolyte and the electrode is improved. Through the synergistic effect of these solvents and additives, the fast charging performance of the battery at high voltage is greatly improved, and the overall performance of the battery is improved.

[0019] In some specific embodiments of the present invention, the ionic conductivity S of the electrolyte at 25° C. satisfies 14.2 mS / cm≤S≤16.8 mS / cm.

[0020] In the present invention, the electrolyte lithium salt refers to an inorganic or organic salt of lithium conventionally used in lithium-ion battery electrolytes, such as at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, and lithium bis(trifluoromethanesulfonyl)imide, but is not limited thereto. It is understood that the specific lithium salt concentration is not particularly limited and can be determined based on the experience and general knowledge of those skilled in the art or by known methods, such as 0.5 mol / L to 3 mol / L.

[0021] In the present invention, the carbonate organic solvent is a chemical solvent containing a carbonate group in the molecular structure, including linear carbonates and cyclic carbonates. It is more common to use linear carbonates and cyclic carbonates as a mixed solvent to improve the performance of the electrolyte. Specific examples include but are not limited to at least one of ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and methyl propyl carbonate (MPC), or a combination of two or more thereof.

[0022] In the present invention, the carboxylate organic solvent is a chemical solvent with the molecular structure shown below:

[0023]

[0024] Wherein, R1 and R2 are independently selected from any one of C1-C3 alkyl and C1-C3 halogenated alkyl.

[0025] Specific examples include at least one of ethyl acetate, methyl acetate, propyl acetate, and ethyl formate.

[0026] In the present invention, the film-forming additive refers to a type of additive that helps the positive and negative electrodes form stable SEI films and CEI films, and specifically may be at least one of vinylene carbonate, fluoroethylene carbonate, vinyl carbonate, and 1,3-propane sultone, but is not limited thereto.

[0027] The drag reducing additive refers to a type of additive that helps reduce interfacial impedance, and specifically may be at least one of lithium difluorooxalatoborate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, vinyl sulfate, and methylene disulfonate, but is not limited thereto.

[0028] The high voltage additive refers to a type of additive that helps to improve the stability of the battery under high voltage, and specifically can be at least one of 1,3,6-hexane trinitrile, ethylene glycol bis(propionitrile) ether, 1,3,5-pentane trinitrile, and 3-phenylsulfonyl propionitrile, but is not limited thereto.

[0029] Furthermore, the configuration of the high voltage fast charge electrolyte in the present invention is not particularly limited and can be prepared by conventional methods in the art. The specific operation is carried out under the condition of isolating water and oxygen, which will not be elaborated here.

[0030] Further, it is understood that the lithium-ion battery described in the present invention includes components such as a positive electrode, a negative electrode and a separator in addition to an electrolyte. There is no particular limitation on these in the present invention, and all types known in the art can be used.

[0031] Beneficial effects of the present invention:

[0032] In the present invention, carboxylic acid ester solvents are introduced on the basis of traditional carbonate-based electrolytes, and a variety of additives are added to optimize the design of the ratio of solvents and additives, thereby realizing the regulation of the electrolyte solvation structure, improving the oxidation / reduction stability of the electrolyte, and improving the compatibility of the electrolyte and the electrode. Through the synergistic effect of these solvents and additives, the fast charging performance of the battery at high voltage is greatly improved; in addition, the electrolyte has good interface stability and excellent antioxidant properties, which broadens the oxidation window of the electrolyte and can inhibit the continuous decomposition of the electrolyte, thereby reducing the decomposition products of the electrolyte, solving the problems of oxidative decomposition, drying up, capacity decay, and interface polarization existing in traditional electrolytes, and improving the overall performance of the battery. DETAILED DESCRIPTION

[0033] Embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. In addition, unless otherwise specified, methods that do not specifically record conditions or steps are conventional methods, and the reagents and materials used can be obtained from commercial sources.

[0035] Example 1

[0036] This embodiment provides a high voltage fast charge electrolyte, the specific composition and preparation are as follows:

[0037] (1) Preparation of basic electrolyte:

[0038] The carboxylate organic solvent and the carbonate organic solvent are uniformly mixed to obtain an organic solvent base liquid; wherein the carboxylate organic solvent is ethyl acetate, and the carbonate organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 1:1;

[0039] Add lithium hexafluorophosphate (LiPF 6 ) and lithium bis(fluorosulfonyl)imide (LiFSI), and stir them thoroughly until they are completely dissolved to obtain a basic electrolyte.

[0040] In the basic electrolyte, lithium hexafluorophosphate (LiPF 6 The concentrations of ) and lithium bis(fluorosulfonyl)imide (LiFSI) were 1 mol / L and 0.5 mol / L, respectively.

[0041] (2) Preparation of high voltage fast charge electrolyte

[0042] Add film-forming additive vinylene carbonate, drag-reducing additive lithium difluorooxalate borate and high-voltage additive ethylene glycol bis(acrylonitrile) ether to the basic electrolyte, stir evenly at room temperature to make them completely dissolved, and obtain a high-voltage fast-charge electrolyte.

[0043] Among them, based on the high-voltage fast-charging electrolyte as the reference, the mass content Ws of the carboxylic acid ester organic solvent is 40%, the mass content W1 of the film-forming additive is 0.5%, the mass content W2 of the resistance-reducing additive is 2%, and the mass content W3 of the high-voltage additive is 0.5%.

[0044] The electrolytes in this embodiment were prepared in an argon-protected glove box, and the water and oxygen content in the glove box was controlled to meet the H 2 O content <10ppm, O 2 Content <1ppm.

[0045] Example 2

[0046] This embodiment provides a high voltage fast charge electrolyte, the specific composition and preparation are as follows:

[0047] (1) Preparation of basic electrolyte:

[0048] The carboxylate organic solvent and the carbonate organic solvent are uniformly mixed to obtain an organic solvent base liquid; wherein the carboxylate organic solvent is ethyl acetate, and the carbonate organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 1:1;

[0049] Add lithium hexafluorophosphate (LiPF 6 ) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and stirred thoroughly until completely dissolved to obtain a basic electrolyte.

[0050] In the basic electrolyte, lithium hexafluorophosphate (LiPF 6 The concentrations of ) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were 1 mol / L and 0.5 mol / L, respectively.

[0051] (2) Preparation of high voltage fast charge electrolyte

[0052] Add fluoroethylene carbonate as a film-forming additive, lithium difluorooxalate borate as a drag-reducing additive, and ethylene glycol bis(acrylonitrile) ether as a high-voltage additive to the basic electrolyte, stir evenly at room temperature to completely dissolve them, and obtain a high-voltage fast-charge electrolyte.

[0053] Among them, based on the high-voltage fast-charging electrolyte as the reference, the mass content Ws of the carboxylic acid ester organic solvent is 40%, the mass content W1 of the film-forming additive is 1%, the mass content W2 of the resistance-reducing additive is 0.5%, and the mass content W3 of the high-voltage additive is 0.5%.

[0054] The electrolytes in this embodiment were prepared in an argon-protected glove box, and the water and oxygen content in the glove box was controlled to meet the H 2 O content <10ppm, O 2 Content <1ppm.

[0055] Example 3

[0056] This embodiment provides a high voltage fast charge electrolyte, the specific composition and preparation are as follows:

[0057] (1) Preparation of basic electrolyte:

[0058] The carboxylate organic solvent and the carbonate organic solvent are uniformly mixed to obtain an organic solvent base liquid; wherein the carboxylate organic solvent is methyl acetate, and the carbonate organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 1:1;

[0059] Add lithium hexafluorophosphate (LiPF 6 ), stir thoroughly until completely dissolved to obtain a basic electrolyte.

[0060] In the basic electrolyte, lithium hexafluorophosphate (LiPF 6 ) concentration is 1.5 mol / L.

[0061] (2) Preparation of high voltage fast charge electrolyte

[0062] Add film-forming additive fluoroethylene carbonate, drag-reducing additive tris(trimethylsilyl)borate and high-voltage additive 1,3,5-pentanetrinitrile to the basic electrolyte, stir evenly at room temperature to make them completely dissolved, and obtain a high-voltage fast-charge electrolyte.

[0063] Among them, based on the high-voltage fast-charging electrolyte as the reference, the mass content Ws of the carboxylic acid ester organic solvent is 50%, the mass content W1 of the film-forming additive is 2%, the mass content W2 of the resistance-reducing additive is 0.5%, and the mass content W3 of the high-voltage additive is 1%.

[0064] The electrolytes in this embodiment were prepared in an argon-protected glove box, and the water and oxygen content in the glove box was controlled to meet the H 2 O content <10ppm, O 2 Content <1ppm.

[0065] Example 4

[0066] This embodiment provides a high voltage fast charge electrolyte, the specific composition and preparation are as follows:

[0067] (1) Preparation of basic electrolyte:

[0068] The carboxylate organic solvent and the carbonate organic solvent are uniformly mixed to obtain an organic solvent base liquid; wherein the carboxylate organic solvent is methyl acetate, and the carbonate organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 1:1;

[0069] Add lithium hexafluorophosphate (LiPF 6 ) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and stirred thoroughly until completely dissolved to obtain a basic electrolyte.

[0070] In the basic electrolyte, lithium hexafluorophosphate (LiPF 6 The concentrations of ) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) were 1 mol / L and 0.5 mol / L, respectively.

[0071] (2) Preparation of high voltage fast charge electrolyte

[0072] Add film-forming additive vinylene carbonate, drag-reducing additive tri(trimethylsilyl)borate and high-voltage additive ethylene glycol bis(acrylonitrile) ether to the basic electrolyte, stir evenly at room temperature to make them completely dissolved, and obtain a high-voltage fast-charge electrolyte.

[0073] Among them, based on the high-voltage fast-charging electrolyte as the reference, the mass content Ws of the carboxylic acid ester organic solvent is 50%, the mass content W1 of the film-forming additive is 0.5%, the mass content W2 of the resistance-reducing additive is 2%, and the mass content W3 of the high-voltage additive is 1%.

[0074] The electrolytes in this embodiment were prepared in an argon-protected glove box, and the water and oxygen content in the glove box was controlled to meet the H 2 O content <10ppm, O 2 Content <1ppm.

[0075] Example 5

[0076] This embodiment provides a high voltage fast charge electrolyte, the specific composition and preparation are as follows:

[0077] (1) Preparation of basic electrolyte:

[0078] The carboxylate organic solvent and the carbonate organic solvent are uniformly mixed to obtain an organic solvent base liquid; wherein the carboxylate organic solvent is methyl acetate, and the carbonate organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 1:1;

[0079] Add lithium hexafluorophosphate (LiPF 6 ), stir thoroughly until completely dissolved to obtain a basic electrolyte.

[0080] In the basic electrolyte, lithium hexafluorophosphate (LiPF 6 ) concentration is 1.5 mol / L.

[0081] (2) Preparation of high voltage fast charge electrolyte

[0082] Add film-forming additive vinylene carbonate, drag-reducing additive methylene disulfonate and high-voltage additive ethylene glycol bis(acrylonitrile) ether to the basic electrolyte, stir evenly at room temperature to make them completely dissolved, and obtain a high-voltage fast-charge electrolyte.

[0083] Among them, based on the high-voltage fast-charging electrolyte as the reference, the mass content Ws of the carboxylic acid ester organic solvent is 20%, the mass content W1 of the film-forming additive is 1%, the mass content W2 of the resistance-reducing additive is 3%, and the mass content W3 of the high-voltage additive is 2%.

[0084] The electrolytes in this embodiment were prepared in an argon-protected glove box, and the water and oxygen content in the glove box was controlled to meet the H 2 O content <10ppm, O 2 Content <1ppm.

[0085] Example 6

[0086] This embodiment provides a high voltage fast charge electrolyte, the specific composition and preparation are as follows:

[0087] (1) Preparation of basic electrolyte:

[0088] The carboxylate organic solvent and the carbonate organic solvent are uniformly mixed to obtain an organic solvent base liquid; wherein the carboxylate organic solvent is ethyl acetate, and the carbonate organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 1:1;

[0089] Add lithium hexafluorophosphate (LiPF 6 ), stir thoroughly until completely dissolved to obtain a basic electrolyte.

[0090] In the basic electrolyte, lithium hexafluorophosphate (LiPF 6 ) concentration is 1.5 mol / L.

[0091] (2) Preparation of high voltage fast charge electrolyte

[0092] Add a film-forming additive 1,3-propane sultone, a drag-reducing additive methanedisulfonic acid methylene ester, and a high-voltage additive 1,3,6-hexanetrinitrile to the basic electrolyte, stir evenly at room temperature to completely dissolve them, and obtain a high-voltage fast-charge electrolyte.

[0093] Among them, based on the high-voltage fast-charging electrolyte as the reference, the mass content Ws of the carboxylic acid ester organic solvent is 20%, the mass content W1 of the film-forming additive is 2%, the mass content W2 of the resistance-reducing additive is 0.5%, and the mass content W3 of the high-voltage additive is 2%.

[0094] The electrolytes in this embodiment were prepared in an argon-protected glove box, and the water and oxygen content in the glove box was controlled to meet the H 2 O content <10ppm, O 2 Content <1ppm.

[0095] Example 7

[0096] This embodiment provides a high voltage fast charge electrolyte, the specific composition and preparation are as follows:

[0097] (1) Preparation of basic electrolyte:

[0098] The carboxylate organic solvent and the carbonate organic solvent are uniformly mixed to obtain an organic solvent base liquid; wherein the carboxylate organic solvent is ethyl acetate, and the carbonate organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 1:1;

[0099] Add lithium hexafluorophosphate (LiPF 6 ), stir thoroughly until completely dissolved to obtain a basic electrolyte.

[0100] In the basic electrolyte, lithium hexafluorophosphate (LiPF 6 ) concentration is 1.5 mol / L.

[0101] (2) Preparation of high voltage fast charge electrolyte

[0102] Add a film-forming additive 1,3-propane sultone, a drag-reducing additive methanedisulfonic acid methylene ester, and a high-voltage additive 1,3,6-hexanetrinitrile to the basic electrolyte, stir evenly at room temperature to completely dissolve them, and obtain a high-voltage fast-charge electrolyte.

[0103] Among them, based on the high-voltage fast-charging electrolyte as the reference, the mass content Ws of the carboxylic acid ester organic solvent is 50%, the mass content W1 of the film-forming additive is 1%, the mass content W2 of the resistance-reducing additive is 1%, and the mass content W3 of the high-voltage additive is 1%.

[0104] The electrolytes in this embodiment were prepared in an argon-protected glove box, and the water and oxygen content in the glove box was controlled to meet the H 2 O content <10ppm, O 2 Content <1ppm.

[0105] Example 8

[0106] This embodiment provides a high voltage fast charge electrolyte, the specific composition and preparation are as follows:

[0107] (1) Preparation of basic electrolyte:

[0108] The carboxylate organic solvent and the carbonate organic solvent are uniformly mixed to obtain an organic solvent base liquid; wherein the carboxylate organic solvent is methyl acetate, and the carbonate organic solvent is a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a mass ratio of 1:1;

[0109] Add lithium hexafluorophosphate (LiPF 6 ), stir thoroughly until completely dissolved to obtain a basic electrolyte.

[0110] In the basic electrolyte, lithium hexafluorophosphate (LiPF 6 ) concentration is 1.5 mol / L.

[0111] (2) Preparation of high voltage fast charge electrolyte

[0112] Add film-forming additive vinylene carbonate, drag-reducing additive tris(trimethylsilyl)phosphate and high-voltage additive 3-phenylsulfonylpropionitrile to the basic electrolyte, stir evenly at room temperature to make them completely dissolved, and obtain a high-voltage fast-charge electrolyte.

[0113] Among them, based on the high-voltage fast-charging electrolyte as the reference, the mass content Ws of the carboxylic acid ester organic solvent is 50%, the mass content W1 of the film-forming additive is 1%, the mass content W2 of the resistance-reducing additive is 2%, and the mass content W3 of the high-voltage additive is 1%.

[0114] The electrolytes in this embodiment were prepared in an argon-protected glove box, and the water and oxygen content in the glove box was controlled to meet the H 2 O content <10ppm, O 2 Content <1ppm.

[0115] Comparative Example 1

[0116] This comparative example provides an electrolyte solution, which adopts the same implementation as Example 8, except that no carboxylic acid ester organic solvent is added.

[0117] Comparative Example 2

[0118] This comparative example provides an electrolyte solution which is implemented in the same manner as in Example 8, except that the mass content of the film-forming additive is 0.1%.

[0119] Comparative Example 3

[0120] This comparative example provides an electrolyte solution which is implemented in the same manner as in Example 8, except that the mass content of the film-forming additive is 7%.

[0121] Comparative Example 4

[0122] This comparative example provides an electrolyte solution, which adopts the same implementation as Example 8, except that the content of the carboxylic acid ester organic solvent is 30%, the content of the film-forming additive is 2%, and the content of the drag-reducing additive is 0.2%.

[0123] Comparative Example 5

[0124] This comparative example provides an electrolyte solution, which adopts the same implementation as Example 8, except that the content of the carboxylic acid ester organic solvent is 20%, the content of the film-forming additive is 2%, and the content of the drag-reducing additive is 10%.

[0125] Table 1 Composition of carboxylic acid ester organic solvents and additives in high voltage fast charge electrolytes in Examples and Comparative Examples

[0126]

[0127]

[0128] Performance Testing

[0129] 1. The electrolytes of Examples 1-8 and Comparative Examples 1-5 were tested for ionic conductivity at room temperature (25° C.). The test results are shown in Table 2.

[0130] 2. The electrolytes in Examples 1-8 and Comparative Examples 1-5 were assembled into soft-pack batteries. The composition of the soft-pack batteries is as follows:

[0131] Positive electrode: LiNi 0.8 Co 0.1 Mn 0.1 O 2 As active material, SP and MWCNT are used as conductive agents, PVDF is used as binder, N-methyl-2-pyrrolidone (NMP) is used as dispersant, and LiNi 0.8 Co 0.1 Mn 0.1 O 2 The positive electrode slurry is prepared with a mass ratio of MWCNT:SP:PVDF=90:4:2:4, and the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and then dried and cold pressed to obtain the positive electrode sheet.

[0132] Negative electrode: The negative electrode active material graphite, the conductive agent acetylene black, the thickener carboxymethyl cellulose (CMC), and the adhesive styrene butadiene rubber (SBR) are mixed uniformly in deionized water at a mass ratio of 96:1:1:2 to prepare a negative electrode slurry with a solid content of 53%, and the negative electrode slurry is coated on the current collector copper foil; after drying and cold pressing, a negative electrode sheet is obtained.

[0133] Separator: Polypropylene with a thickness of 16 μm was used as the separator.

[0134] The electrolyte in each embodiment and comparative example was prepared into a 2Ah soft-pack battery according to the above composition, and its electrochemical performance was tested. The specific test conditions were: the soft-pack battery was first charged and discharged at current densities of 3.0 and 4.0C, and then the cycle performance test was performed at a current density of 4.0C. The charge and discharge cut-off voltage was set in the range of 2.8-4.7V. The test results are shown in Table 2.

[0135] Table 2 Electrochemical performance test results of 2Ah soft pack battery

[0136]

[0137] The discharge capacity retention rate in the storage performance = final cycle discharge capacity / first cycle discharge capacity × 100%.

[0138] It can be seen from the test results in Table 2 that the ionic conductivity of the high-voltage fast-charge electrolyte prepared in the present invention is more excellent, and the use of carboxylic acid ester solvents reduces the viscosity of the electrolyte, which increases the lithium ion transfer kinetics under high voltage compared with the traditional electrolyte. At the same time, by optimizing the composition and ratio of solvents and additives, the LiPF 6 Combined with the previous analysis, the lithium-ion battery made with this electrolyte also has long cycle stability and excellent rate performance at high voltage.

[0139] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0140] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A high voltage fast charge electrolyte, characterized in that: The invention comprises an electrolyte lithium salt, an organic solvent and an additive, wherein the organic solvent comprises a carbonate organic solvent and a carboxylate organic solvent, and the additive comprises a film-forming additive, a resistance-reducing additive and a high-voltage additive; Wherein, based on the electrolyte as the reference, the mass content of the film-forming additive is recorded as W1, the mass content of the drag-reducing additive is recorded as W2, and the mass content of the carboxylic acid ester organic solvent is recorded as Ws, then 0.003≤W1 / Ws≤0.125; and / or 0.01≤W2 / Ws≤0.25 is satisfied; Preferably, the mass content of the high voltage additive is recorded as W3 based on the electrolyte, and then 20%≤Ws≤50%, and / or 0.5%≤W1≤2%, and / or 0.5%≤W2≤3%, and / or 0.5%≤W3≤2% are satisfied; Preferably, the ionic conductivity S of the electrolyte at 25° C. satisfies 14.2 mS / cm≤S≤16.8 mS / cm.

2. The high voltage fast charge electrolyte according to claim 1, characterized in that: The electrolyte lithium salt is at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethanesulfonyl)imide.

3. The high voltage fast charge electrolyte according to claim 1, characterized in that: The carbonate organic solvent is at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate.

4. The high voltage fast charge electrolyte according to claim 1, characterized in that: The carboxylate organic solvent is at least one of ethyl acetate, methyl acetate, propyl acetate and ethyl formate.

5. The high voltage fast charge electrolyte according to claim 1, characterized in that: The film-forming additive is at least one of vinylene carbonate, fluoroethylene carbonate, vinyl vinyl carbonate, and 1,3-propane sultone.

6. The high voltage fast charge electrolyte according to claim 1, characterized in that: The drag reducing additive is at least one of lithium difluorooxalatoborate, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, vinyl sulfate, and methylene methanedisulfonate.

7. The high voltage fast charge electrolyte according to claim 1, characterized in that: The high voltage additive is at least one of 1,3,6-hexane trinitrile, ethylene glycol bis(propionitrile) ether, 1,3,5-pentane trinitrile, and 3-phenylsulfonyl propionitrile.

8. A method for preparing a high voltage fast charge electrolyte according to any one of claims 1 to 7, characterized in that: The following steps are involved: preparing a basic electrolyte, wherein the basic electrolyte is obtained by uniformly mixing an electrolyte lithium salt and an organic solvent; After adding a film-forming additive, a resistance-reducing additive and a high-voltage additive to the basic electrolyte respectively and fully dissolving them, a high-voltage fast-charging electrolyte is obtained.

9. Use of the high voltage fast charging electrolyte according to any one of claims 1 to 7 in the preparation of lithium ion batteries.

10. A lithium ion battery, characterized in that: Contains the high voltage fast charge electrolyte as described in any one of claims 1 to 7.

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