Electrolyte, lithium-ion battery, and vehicle

Abstract

An electrolyte, a lithium-ion battery, and a vehicle. The electrolyte comprises an organic solvent, a fluorine-containing lithium salt, and a first additive. The organic solvent comprises a carboxylic acid ester and a carbonate ester. The first additive comprises a combination of 1,3-propanesultone and methylene methanedisulfonate. Based on the total mass of the electrolyte being 100%, the content of the carboxylic acid ester is S1, the content of 1,3-propanesultone is W1, and the content of methylene methanedisulfonate is W2; and S1, W1, and W2 satisfy (S1 / 120)<(W1+W2)<(S1 / 20). By means of the synergistic effect of the organic solvent, the fluorine-containing lithium salt, and the additive, low-temperature conductivity is greatly improved, effectively shortening the battery charging time at a low temperature. A prepared lithium-ion battery exhibits both excellent fast-charging performance and low-temperature performance without compromising high-temperature performance.

Description

An electrolyte, a lithium-ion battery, and a vehicle

[0001] This application claims priority to Chinese Patent Application No. 202411527878.0, filed on October 30, 2024, entitled "An Electrolyte, a Lithium-ion Battery and a Vehicle", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to, but is not limited to, the field of electrolyte technology, and particularly to an electrolyte, a lithium-ion battery, and a vehicle. Background Technology

[0003] Lithium-ion batteries have been widely used in various electronic products, electric vehicles, power tools, and energy storage devices in recent years due to their advantages such as high capacity, high voltage, high cycle stability, and environmental friendliness. Their application is particularly prevalent in electric vehicles. However, conventional lithium-ion batteries have a narrow operating temperature range, exhibiting either low discharge rates at low temperatures or poor storage performance at high temperatures. Therefore, researching lithium-ion batteries that can balance performance at both low and high temperatures is of significant practical importance.

[0004] Compared to ternary cathode materials, lithium iron phosphate materials exhibit slower lithium-ion diffusion rates, poorer electronic conductivity, and a greater tendency to polarize, especially at low temperatures. Since the inherent properties of the electrolyte and its interface with the positive and negative electrodes significantly influence the high and low temperature performance of the battery, it is desirable to provide an electrolyte that can balance the low-temperature and high-temperature performance of lithium-ion batteries. Summary of the Invention

[0005] The following is an overview of the subject matter described in detail herein. This overview is not intended to limit the scope of the claims.

[0006] This application provides an electrolyte, a lithium-ion battery, and a vehicle.

[0007] In a first aspect, this application provides an electrolyte comprising an organic solvent, a fluorinated lithium salt, and a first additive;

[0008] The organic solvents include carboxylic acid esters and carbonates;

[0009] The first additive comprises a combination of 1,3-propanesulfonate lactone (PS) and methylene methane disulfonate (MMDS);

[0010] With the total mass of the electrolyte as 100%, the content of the carboxylic acid ester is S1, the content of the 1,3-propanesulfonate lactone is W1, and the content of the methane disulfonate methylene ester is W2. S1, W1, and W2 satisfy (S1 / 120) < (W1 + W2) < (S1 / 20).

[0011] As a preferred technical solution of this application, S1 satisfies 20% ≤ S1 ≤ 65%.

[0012] As a preferred technical solution of this application, W1 satisfies 0.05% ≤ W1 ≤ 1%.

[0013] As a preferred technical solution of this application, W2 satisfies 0.05% ≤ W2 ≤ 1%.

[0014] As a preferred embodiment of this application, the carboxylic acid ester includes any one or more of ethyl acetate (EA), ethyl propionate (EP), methyl propionate (MP), or methyl acetate (MA).

[0015] As a preferred embodiment of this application, the carbonate includes any one or more of ethyl methyl carbonate (EMC), ethylene carbonate (EC), or dimethyl carbonate (DMC).

[0016] As a preferred embodiment of this application, the fluorinated lithium salt includes lithium bis(fluorosulfonyl)imide (LiFSI), and the content of lithium bis(fluorosulfonyl)imide is 1-8% based on the total mass of the electrolyte as 100%.

[0017] As a preferred embodiment of this application, the fluorinated lithium salt further includes lithium hexafluorophosphate (LiPF6).

[0018] As a preferred technical solution of this application, the content of the fluorinated lithium salt is 10-18% based on the total mass of the electrolyte as 100%.

[0019] As a preferred embodiment of this application, the electrolyte further includes a second additive, which includes any one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) borate (TMSB), lithium difluorooxalate borate (LiODFB), vinyl sulfate (DTD), or lithium difluorophosphate (LiPO2F2).

[0020] As a preferred embodiment of this application, the content of the second additive is 1-5% based on the total mass of the electrolyte being 100%.

[0021] Secondly, this application provides a lithium-ion battery, the lithium-ion battery comprising the electrolyte described in the first aspect.

[0022] As a preferred technical solution of this application, the lithium-ion battery further includes a positive electrode, a negative electrode, and a separator.

[0023] As a preferred technical solution of this application, the positive electrode material in the positive electrode sheet includes lithium iron phosphate positive electrode material.

[0024] As a preferred technical solution of this application, the negative electrode material in the negative electrode sheet includes graphite.

[0025] As a preferred embodiment of this application, the charging cutoff voltage of the lithium-ion battery is ≤3.75V.

[0026] Thirdly, this application provides a vehicle that includes the lithium-ion battery described in the second aspect.

[0027] The technical solution provided in this application has the following advantages compared with the prior art:

[0028] The electrolyte provided in this application significantly improves the low-temperature conductivity through the synergistic effect of organic solvents, fluorinated lithium salts, and additives, effectively shortening the charging time of the battery at low temperatures. At the same time, it overcomes the problem of poor compatibility between carboxylic esters and graphite anodes, while taking into account high-temperature performance. This allows the prepared lithium-ion battery to have both excellent fast-charging performance and low-temperature performance without sacrificing high-temperature performance.

[0029] After reading and understanding the detailed description, other aspects can be understood. Detailed Implementation

[0030] To better understand the above-mentioned objectives, features, and advantages of this application, the solution of this application will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0031] Many specific details are set forth in the following description in order to provide a full understanding of this application, but this application may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some embodiments of this application, and not all embodiments.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this application.

[0033] Compared to ternary cathode materials, lithium iron phosphate materials exhibit slower lithium-ion diffusion rates, poorer electronic conductivity, and a greater tendency to polarize, especially at low temperatures. Since the inherent properties of the electrolyte and its interface with the positive and negative electrodes significantly influence the high and low temperature performance of the battery, it is desirable to provide an electrolyte that can balance the low-temperature and high-temperature performance of lithium-ion batteries.

[0034] In a first aspect, embodiments of this application provide an electrolyte comprising an organic solvent, a fluorinated lithium salt, and a first additive;

[0035] The organic solvents include carboxylic acid esters and carbonates;

[0036] The first additive comprises a combination of 1,3-propanesulfonate lactone (PS) and methylene methane disulfonate (MMDS);

[0037] With the total mass of the electrolyte as 100%, the content of the carboxylic acid ester is S1, the content of the 1,3-propanesulfonate lactone is W1, and the content of the methane disulfonate methylene ester is W2. S1, W1, and W2 satisfy (S1 / 120) < (W1 + W2) < (S1 / 20).

[0038] The electrolyte provided in this application significantly improves low-temperature conductivity through the synergistic effect of organic solvents, fluorinated lithium salts, and a first additive, effectively shortening the charging time of the battery at low temperatures. This allows the prepared lithium-ion battery to possess both excellent fast-charging and low-temperature performance without sacrificing high-temperature performance. Specifically:

[0039] The electrolyte provided in this application includes an organic solvent, a fluorinated lithium salt, and a first additive. Firstly, the organic solvent, a carboxylic acid ester, has low viscosity and a high dielectric constant, which effectively improves the ion transport rate of the electrolyte, thereby enhancing the battery's fast-charging performance at low temperatures. Simultaneously, because carboxylic acid esters have poor compatibility with the graphite anode, they are difficult to form a stable SEI film, leading to poor capacity retention after high-temperature cycling and storage. Furthermore, they can cause the battery to easily swell at high temperatures, affecting its safety performance. Therefore, this application introduces a fluorinated lithium salt into the electrolyte, which can generate a LiF-rich component. The interface film improves the ionic conductivity and reduces the initial impedance, enhances the compatibility between the carboxylic ester system and the negative electrode, and strengthens the film-forming stability of the SEI film, thereby significantly improving the high-temperature performance of the battery. The additive 1,3-propanesulfonate lactone generates alkyl sulfonates and sulfonate compounds containing unsaturated bonds (C=C) during battery formation, which can effectively inhibit further reactions between the carboxylic ester solvent and the graphite negative electrode, and improve the interfacial stability of the SEI film. Methylene methane disulfonate is a sulfur-based additive that can preferentially reduce carboxylic esters, resulting in good film-forming effect. At high temperatures, it can inhibit the dissolution of transition metals and improve the high-temperature performance of the battery.

[0040] This application's embodiments creatively discover the interaction between the contents of carboxylic acid ester S1, 1,3-propanesulfonate lactone W1, and methanedisulfonate methylene ester W2 in the electrolyte. When (S1 / 120) < (W1+W2) < (S1 / 20), the problem of poor compatibility between carboxylic acid ester and graphite anode can be overcome, while simultaneously ensuring fast charging and low-temperature performance. This allows the battery to have excellent low-temperature performance without sacrificing high-temperature performance. Specifically:

[0041] This application discovers that when the contents of carboxylic acid esters, 1,3-propanesulfonate lactone, and methanedisulfonate in the electrolyte satisfy the above-mentioned relationship, increasing the content of carboxylic acid esters can improve the low-temperature performance of the battery and reduce impedance. However, the increased degree of side reaction between carboxylic acid esters and graphite leads to a decrease in the cycle performance of the battery. Therefore, more first additives (1,3-propanesulfonate lactone and methanedisulfonate) are needed to participate in the film formation at the negative electrode interface and suppress the occurrence of negative electrode side reactions. At the same time, the increase in the content of carboxylic acid esters compensates for the impact on the fast-charging performance and low-temperature performance of the battery caused by the increase of 1,3-propanesulfonate lactone and methanedisulfonate. That is, when the content of carboxylic acid esters increases, the content of first additives must also increase. Correspondingly, when the content of carboxylic acid esters decreases, the content of first additives must also decrease to satisfy the relationship. Therefore, the embodiments of this application achieve a balanced low-temperature and high-temperature performance of the battery through the synergistic effect of carboxylic acid esters, 1,3-propanesulfonate lactone, and methanedisulfonate in the electrolyte. If S1 is too large and W1+W2 is small, the battery's low-temperature performance and fast-charging performance will improve, but the protective effect of the interfacial film will decrease, and interfacial side reactions will intensify, leading to increased interfacial film decomposition and decreased battery cycle and storage performance. If S1 is too small and W1+W2 is large, the electrolyte viscosity will increase, the ion migration rate will decrease, and the film-forming resistance will increase, improving the battery's cycle and storage performance, but decreasing its low-temperature performance and fast-charging performance.

[0042] In some embodiments of this application, S1 satisfies 20% ≤ S1 ≤ 65%, for example, it can be 20%, 30%, 40%, 50%, 60%, 65%, etc. However, this application is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0043] When the content of carboxylic acid ester is within the range of this application, it can more effectively improve the low-temperature conductivity of the electrolyte. If the content of carboxylic acid ester is too low, the conductivity of the electrolyte will decrease, resulting in a decrease in low-temperature performance. If the content of carboxylic acid ester is too high, it may lead to a decrease in the cycle performance of the battery.

[0044] In some embodiments of this application, W1 satisfies 0.05% ≤ W1 ≤ 1%, for example, it can be 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, etc. However, this application is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] When the content of 1,3-propanesulfonate lactone is within this range, it can more effectively inhibit the further reaction between the carboxylic acid ester solvent and the graphite anode, thereby improving the interfacial stability of the SEI film.

[0046] In some embodiments of this application, W2 satisfies 0.05% ≤ W2 ≤ 1%, for example, it can be 0.05%, 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, 1%, etc. However, this application is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0047] When the content of methylene methane disulfonate is within this range, it can more effectively suppress the dissolution of transition metals at high temperatures and improve the high-temperature performance of the battery.

[0048] In some embodiments of this application, the carboxylic acid ester includes any one or more of ethyl acetate (EA), ethyl propionate (EP), methyl propionate (MP), or methyl acetate (MA). In these embodiments, the carboxylic acid ester can significantly improve the low-temperature conductivity of the electrolyte, effectively shortening the charging time of the battery at low temperatures.

[0049] In some embodiments of this application, the carboxylic acid ester is selected from ethyl acetate.

[0050] In some embodiments of this application, the carbonate includes any one or more of ethyl methyl carbonate (EMC), ethylene carbonate (EC), or dimethyl carbonate (DMC).

[0051] In some embodiments of this application, the fluorinated lithium salt includes lithium bis(fluorosulfonyl)imide. In these embodiments, lithium bis(fluorosulfonyl)imide can generate an interface film rich in LiF, improving the ionic conductivity of the interface film and reducing its initial impedance, thus improving the compatibility of the carboxylic acid ester system with the graphite anode and enhancing the film-forming stability of the SEI film, thereby significantly improving the high-temperature performance of the battery.

[0052] In some embodiments of this application, the content of lithium bis(fluorosulfonyl)imide is 1-8% based on the total mass of the electrolyte as 100%, for example, 1%, 2%, 4%, 6%, 8%, etc. However, this application is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0053] When the content of lithium bis(fluorosulfonyl)imide is within the above range, it can more effectively improve the compatibility between the carboxylic acid ester system and the graphite anode.

[0054] In some embodiments of this application, the fluorinated lithium salt further includes lithium hexafluorophosphate.

[0055] In some embodiments of this application, the content of the fluorinated lithium salt is 10-18% based on the total mass of the electrolyte as 100%, such as 10%, 12%, 14%, 16%, 18%, etc. However, this application is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0056] When the content of fluorinated lithium salt is within this range, it can more effectively improve the ionic conductivity of the electrolyte, thereby improving the low-temperature fast charging performance of the battery. If the content of fluorinated lithium salt is too high or too low, it may lead to a decrease in the ionic conductivity of the electrolyte, or even lithium plating during low-temperature charging.

[0057] In some embodiments of this application, the electrolyte further includes a second additive, which comprises any one or more of vinylene carbonate (VC), fluoroethylene carbonate (FEC), vinyl ethylene carbonate (VEC), tris(trimethylsilane) phosphate (TMSP), tris(trimethylsilane) borate (TMSB), lithium difluorooxalate borate (LiODFB), vinyl sulfate (DTD), or lithium difluorophosphate (LiPO2F2). This application allows for the addition of a second additive as needed.

[0058] In some embodiments of this application, the content of the second additive is 1-5% based on the total mass of the electrolyte as 100%, such as 1%, 2%, 3%, 4%, 5%, etc. However, this application is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0059] Secondly, embodiments of this application provide a lithium-ion battery, the lithium-ion battery comprising the electrolyte described in the first aspect.

[0060] The lithium-ion battery provided in this application has excellent high-temperature performance, cycle performance, low-temperature fast charging performance, and safety.

[0061] In some embodiments of this application, the lithium-ion battery further includes a positive electrode, a negative electrode, and a separator.

[0062] In some embodiments of this application, the positive electrode material in the positive electrode sheet includes lithium iron phosphate positive electrode material.

[0063] The electrolyte provided in this application is suitable for lithium iron phosphate cathode lithium-ion batteries, and can solve the polarization during low-temperature charging, thus ensuring the high-temperature and low-temperature performance of lithium-ion batteries.

[0064] In some embodiments of this application, the negative electrode material in the negative electrode sheet includes graphite.

[0065] In some embodiments of this application, the charging cutoff voltage of the lithium-ion battery is ≤3.75V.

[0066] The electrolyte provided in this application is suitable for graphite anode lithium-ion batteries, is compatible with graphite anodes, and ensures the high-temperature and low-temperature performance of lithium-ion batteries.

[0067] Thirdly, embodiments of this application provide a vehicle that includes the lithium-ion battery described in the second aspect.

[0068] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0069] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with conventional techniques or conditions in the art, techniques or conditions described in the literature, or product instructions. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0070] Examples & Comparative Examples

[0071] The examples and comparative examples each provide an electrolyte, the specific composition of which is shown in Table 1.

[0072] Table 1

[0073] Application examples

[0074] The batteries are assembled using the electrolytes provided in the examples and comparative examples, as detailed below:

[0075] (1) Preparation of electrolyte

[0076] In a glove box or drying room, carbonates and carboxylic esters are mixed according to the mass ratios in Table 1. Then, the substances shown in Table 1 are added and mixed thoroughly to prepare the electrolyte. The content of each substance shown in Table 1 is a mass percentage based on the total mass of the electrolyte.

[0077] (2) Preparation of positive electrode sheet

[0078] LiFePO4 (positive electrode material), PVDF (binder), and acetylene black (conductive agent) were mixed in a mass ratio of 94:3:3. N-methylpyrrolidone (NMP) solvent was added until the system became homogeneous and transparent. The mixture was stirred using a vacuum mixer to obtain a positive electrode slurry, which was then uniformly coated onto a 12 μm thick aluminum current collector foil. After air-drying at room temperature, the slurry was transferred to a 120°C oven and dried for 1 hour. Finally, it was cold-pressed (compacted density 2.5 g / cm³). 3 The positive electrode sheet is obtained by cutting.

[0079] (3) Preparation of negative electrode

[0080] A negative electrode slurry was prepared by mixing graphite (anode material), sodium carboxymethyl cellulose (CMC) solution (thickener), and styrene-butadiene rubber (SBR) emulsion (binder) at a mass ratio of graphite:sodium carboxymethyl cellulose:SBR of 96:2:2. Deionized water solvent was added, and the mixture was stirred using a vacuum mixer. This slurry was then uniformly coated onto a copper foil current collector (8 μm thick). After air-drying at room temperature, it was transferred to a 120°C oven for 1 hour of drying, followed by cold pressing (compacted density 1.6 g / cm³). 3 The negative electrode sheet is obtained by cutting.

[0081] (4) Assembly of lithium-ion batteries

[0082] The positive electrode sheet, negative electrode sheet, and polypropylene separator are wound together, wrapped with an aluminum-plastic film, baked to remove water, injected with the above-mentioned electrolyte, and sealed. After standing, hot and cold pressing, formation, clamping, and capacity testing, a soft-pack lithium-ion battery is prepared.

[0083] It should be noted that the lithium-ion battery used for testing described above is only an example for testing the performance of the electrolyte. This application is not limited to this type of battery. The raw materials (other than the electrolyte), proportions, parameters and processes can all be replaced with other conventional raw materials, proportions, parameters and processes in the field to form a battery different from the lithium-ion battery used for testing.

[0084] Performance testing

[0085] Performance tests were conducted on the electrolytes prepared in the examples and comparative examples and the assembled lithium-ion batteries:

[0086] (1) Electrolyte conductivity test

[0087] The electrolytes of the examples and comparative examples were placed in a 25°C constant temperature water bath for 30 minutes, and then the conductivity was measured using a conductivity meter.

[0088] (2) Low-temperature fast charging lithium plating test

[0089] At -10°C, the lithium-ion batteries of the examples and comparative examples were first discharged at 1C to 2.0V, then charged at 0.5C constant current to 3.75V. After 10 charge-discharge cycles, they were charged at 1C constant current to 3.75V, and then charged at constant voltage to a current of 0.05C. Finally, they were disassembled in a drying room to observe the negative electrode interface.

[0090] (3) 25℃ 4C cycle performance test

[0091] At 25°C, the lithium-ion batteries of the examples and comparative examples were first discharged at 1C to 2.0V and then subjected to cycle testing. The test procedure was as follows: first, constant current charging at 4C to 3.75V, then constant voltage charging to a current of 0.05C, and then constant current discharging at 1C to 2.0V. This charge / discharge cycle was repeated, and the capacity retention rate of the lithium-ion battery after 1000 cycles at 25°C with 4C / 1C was calculated.

[0092] (4) Storage performance test at 60℃

[0093] At 25°C, the lithium-ion batteries of the examples and comparative examples were first discharged at 1C to 2.0V, then charged at a constant current of 1C to 3.75V, then charged at a constant voltage to a current of 0.05C, and finally discharged at a constant current of 1C to 2.0V. The discharge capacity was recorded as C. 放1 The battery cell was then charged at a constant current of 1C to 3.75V, followed by constant voltage charging to a current of 0.05C. The cell was stored in a 60℃ oven for 60 days, then placed at room temperature. It was first discharged at 1C to 2.0V, then charged at a constant current of 1C to 3.75V, followed by constant voltage charging to a current of 0.05C, and finally discharged at a constant current of 1C to 2.0V. The discharge capacity was recorded as C. 放2 C 放2 / C 放1 = Capacity retention rate.

[0094] The test results are shown in Table 2:

[0095] Table 2

[0096] As can be seen from Table 2, the electrolyte provided in this application has high conductivity. The lithium-ion battery prepared using the electrolyte provided in this application has excellent low-temperature fast charging performance, high-temperature storage performance, and cycle performance compared with traditional electrolyte systems.

[0097] A comparison of Example 1 with the conventional electrolyte system (Comparative Example 1) reveals that the low-temperature charging capability of the battery cell can be significantly improved without deteriorating cycle and high-temperature performance.

[0098] A comparison of Example 1 and Comparative Example 2 reveals that the introduction of additives PS and MMDS significantly improved the 60°C storage performance and 25°C 4C cycle capacity retention without deteriorating the lithium plating level during -10°C 0.5C charging. This indicates that PS can generate alkyl sulfonates and sulfonate compounds containing unsaturated bonds (C=C), effectively inhibiting further reactions between the carboxylic acid ester solvent and the graphite anode, thus enhancing the interfacial stability of the SEI film. Meanwhile, methylene disulfonate, a sulfur-based additive, preferentially reduces carboxylic acid esters, resulting in good film formation. At high temperatures, it can suppress transition metal dissolution, improving the battery's high-temperature performance. The synergistic effect of these two additives significantly enhances the interfacial stability of the carboxylic acid ester electrolyte system.

[0099] A comparison of Examples 1 and 2 reveals that reducing the PS content decreases the storage performance at 60°C, while the capacity retention rate at 25°C 4C cycling is similar. This indicates that 0.05% PS content provides relatively poor protection for the anode interface, while 0.5% PS content can more effectively inhibit further reactions between the carboxylic acid ester solvent and the graphite anode, thereby improving the high-temperature interface stability of the SEI film.

[0100] A comparison of Examples 1 and 3 reveals that increasing the PS content slightly improves the storage performance at 60°C and the capacity retention rate during 4C cycling at 25°C. However, slight lithium plating occurs during 0.5C charging at -10°C, indicating that while increasing the PS content improves the interfacial stability of the SEI film at high temperatures, it also leads to a deterioration in low-temperature performance.

[0101] The comparison between Examples 1 and 4-5 shows that reducing the amount of MMDS slightly worsens the high-temperature storage performance of the battery, while increasing the amount of MMDS results in moderate lithium plating during charging at -10°C and 0.5C. This indicates that adding an appropriate amount of MMDS can improve high-temperature cycle performance and storage performance while also maintaining low-temperature fast charging performance.

[0102] A comparison of Examples 1 and 6 reveals that reducing the EA content decreases the electrolyte conductivity, causes slight lithium plating during 0.5C charging at -10°C, and significantly improves high-temperature storage and cycling performance.

[0103] A comparison of Examples 1 and 7 reveals that increasing the EA content increases the conductivity of the electrolyte. To ensure interface stability, it is necessary to simultaneously increase the content of MMDS and PS to ensure that high-temperature storage and cycling do not deteriorate significantly.

[0104] A comparison of Examples 1 and 8-9 reveals that replacing EA with EP slightly improves high-temperature storage, but there is slight lithium plating during 0.5C charging at -10°C; replacing EA with MA worsens high-temperature storage and cycling performance.

[0105] A comparison of Examples 1 and 10 reveals that EP partially replaces EA, resulting in slight improvement in high-temperature storage, and slight lithium plating during 0.5C charging at -10°C.

[0106] A comparison of Examples 1 and 11 reveals that the total lithium salt content is reduced, the electrolyte conductivity is reduced, and there is slight lithium plating during charging at -10°C and 0.5C.

[0107] A comparison of Examples 1 and 12 reveals that an increase in total lithium salt content leads to a decrease in electrolyte conductivity, and moderate lithium plating occurs during 0.5C charging at -10°C.

[0108] A comparison of Examples 1 and 13-19 reveals that the addition of additives such as FEC, VEC, TMSP, LiODFB, DTD, TMSP, and LiPO2F2 has a slight impact on cycling and storage. These additives can be added according to the actual application.

[0109] The comparison between Comparative Example 2 and Comparative Example 1 (traditional electrolyte system) reveals that the degree of lithium plating during 0.5C charging at -10℃ and the low-temperature charging time are significantly reduced. However, due to the large degree of side reaction between carboxylic acid ester EA and the graphite anode, the storage performance at 60℃ and the capacity retention rate during 4C cycling at 25℃ are significantly reduced. This indicates that although carboxylic acid ester EA can improve the low-temperature performance of the battery, its high-temperature cycling and storage performance is poor.

[0110] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0111] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

An electrolyte comprising an organic solvent, a fluorinated lithium salt, and a first additive; The organic solvents include carboxylic acid esters and carbonates; The first additive comprises a combination of 1,3-propanesulfonate lactone and methanedisulfonate methylene ester; With the total mass of the electrolyte as 100%, the content of the carboxylic acid ester is S1, the content of the 1,3-propanesulfonate lactone is W1, and the content of the methane disulfonate methylene ester is W2. S1, W1, and W2 satisfy (S1 / 120) < (W1 + W2) < (S1 / 20). The electrolyte according to claim 1, wherein, S1 satisfies 20% ≤ S1 ≤ 65%. The electrolyte according to claim 1 or 2, wherein, W1 satisfies 0.05% ≤ W1 ≤ 1%; And / or, W2 satisfies 0.05% ≤ W2 ≤ 1%. The electrolyte according to any one of claims 1-3, wherein, The carboxylic acid ester includes any one or more of ethyl acetate, ethyl propionate, methyl propionate, or methyl acetate; And / or, the carbonate includes any one or more of ethyl methyl carbonate, ethylene carbonate, or dimethyl carbonate. The electrolyte according to any one of claims 1-4, wherein, The fluorinated lithium salt includes lithium bis(fluorosulfonyl)imide, and the content of lithium bis(fluorosulfonyl)imide is 1-8% based on the total mass of the electrolyte (100%). The electrolyte according to any one of claims 1-5, wherein, The fluorinated lithium salt also includes lithium hexafluorophosphate. The electrolyte according to any one of claims 1-6, wherein, The content of the fluorinated lithium salt is 10-18% based on the total mass of the electrolyte (100%). The electrolyte according to any one of claims 1-7 further comprises a second additive, the second additive comprising any one or more of vinylene carbonate, fluoroethylene carbonate, vinyl ethylene carbonate, tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, lithium difluorooxalate borate, ethylene sulfate, or lithium difluorophosphate. A lithium-ion battery comprising the electrolyte according to any one of claims 1-8. A vehicle comprising the lithium-ion battery of claim 9.

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