Electrolyte for improving low-temperature performance and preparation method and application thereof

Abstract

The invention discloses an electrolyte for improving low-temperature performance and a preparation method and application thereof, and the electrolyte is prepared from the following raw materials in parts by weight: 0.6-5 parts of PTSM additive, 80-90 parts of organic solvent and 10-15 parts of electrolyte lithium salt; the organic solvent comprises a carbonic ester organic solvent and a carboxylic ester organic solvent; the structural formula of the PTSM additive is as shown in formula I in the specification. According to the invention, after the additive containing 4-methyl benzenesulfonic acid propyl ester (PTSM) is used as the additive, the low-temperature cycle capacity retention ratio of the battery is obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular to an electrolyte with improved low-temperature performance, a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have become one of the important chemical energy sources that are indispensable in the fields of electronic digital, electric vehicles, energy storage applications, aerospace, etc. due to their high operating voltage, high specific energy density, long cycle life, and environmental friendliness. Electrolyte is an important component of lithium-ion batteries and is called the "blood" of lithium-ion batteries. It is usually composed of lithium salts, solvents, and additives, and has an important impact on the cycle performance, rate performance, and safety performance of lithium-ion batteries. Since the electrolyte must simultaneously meet the requirements of compatibility with positive and negative electrode materials, physical and chemical stability, high conductivity, and low viscosity during operation, cyclic carbonates, chain carbonates, and low-viscosity carboxylate compounds are generally selected to form a combined solvent, which can solve the viscosity problem of the solvent at low temperatures. However, under low temperature conditions, solvents containing linear carbonates and carboxylates often have relatively low dielectric constants, so it is difficult for conventional lithium salts to completely dissolve under low temperature conditions, resulting in low ion conductivity and difficulty in maintaining a faster lithium ion migration rate, resulting in poor low-temperature performance of lithium-ion batteries.

[0003] Therefore, it is urgent to develop an electrolyte that can improve the low-temperature performance of the battery. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention provides an electrolyte with improved low temperature performance, and after using a 4-propyl methylbenzenesulfonate (PTSM) type additive as an additive, the low temperature cycle capacity retention rate of the battery is significantly improved.

[0005] A second aspect of the present invention provides a method for preparing an electrolyte with improved low-temperature performance.

[0006] A third aspect of the present invention provides a lithium-ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and the electrolyte.

[0007] According to the first aspect of the present invention, an electrolyte with improved low temperature performance, the raw materials for preparing the electrolyte include 0.6 to 5 parts of PTSM additives, 80 to 90 parts of organic solvents and 10 to 15 parts of electrolyte lithium salts, by weight;

[0008] The organic solvent includes: carbonate organic solvent and carboxylate organic solvent;

[0009] The structural formula of the PTSM additive is shown in Formula I:

[0010] R is selected from F, Br, HSO3, p-CH3-C6H4-SO2, an alkane or cycloalkane having 1 to 6 carbon atoms;

[0011]

[0012] PTSM additives are superior to solvent molecules in the electrolyte and preferentially decompose, which is conducive to the formation of a stable low-impedance interface film at the positive and negative electrodes of lithium ions. Compared with batteries without the additive, the battery containing the additive shows stronger performance. After 3000 cycles at 25°C, the capacity retention rate increased from 50.21% to 94.20%. Under the temperature condition of -20°C, after 100 cycles, the capacity retention rate increased from 37.32% to 88.02%, indicating that PTSM has a unique effect on the low-temperature cycle performance of lithium-ion batteries.

[0013] According to some preferred embodiments of the present invention, the raw materials for preparing the electrolyte include the following components, measured by weight: 0.5 to 5 parts of PTSM additives, 70 to 78 parts of carbonate organic solvents, 10 to 20 parts of carboxylate organic solvents and 10 to 15 parts of electrolyte lithium salts.

[0014] According to some preferred embodiments of the present invention, the raw materials for preparing the electrolyte include the following components, measured by weight: 1 to 5 parts of PTSM additives, 84 to 87 parts of organic solvents and 10 to 15 parts of electrolyte lithium salts.

[0015] According to some preferred embodiments of the present invention, the raw materials for preparing the electrolyte include the following components by weight: 3 parts of PTSM additives, 85 parts of organic solvents and 13 parts of electrolyte lithium salts;

[0016] The PTSM additive is isobutyl o-toluenesulfonate;

[0017] In terms of volume ratio, the organic solvent is: ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate: ethylene glycol propylene ether in a ratio of 2:4:2:2;

[0018] The electrolyte lithium salt is composed of 9 parts of lithium hexafluorophosphate and 3 parts of lithium bis(fluorosulfonyl)imide.

[0019] According to some embodiments of the present invention, the PTSM additive includes at least one of propyl 4-methylbenzenesulfonate, isoamyl p-toluenesulfonate, isobutyl o-toluenesulfonate, sec-butyl p-toluenesulfonate, 3,3-dimethylbutyl 4-methylbenzenesulfonate, 2,2-dimethylpropyl p-toluenesulfonate, 1,3-propylene glycol-di-m-toluenesulfonate and n-butyl p-toluenesulfonate.

[0020] According to some embodiments of the present invention, the structural formula of 4-methylbenzenesulfonate is shown in II:

[0021]

[0022] According to some embodiments of the present invention, the structural formula of isopentyl p-toluenesulfonate is shown in III:

[0023]

[0024] According to some embodiments of the present invention, the structural formula of isobutyl o-toluenesulfonate is shown in IV:

[0025]

[0026] According to some embodiments of the present invention, the structural formula of sec-butyl p-toluenesulfonate is shown in V:

[0027]

[0028] According to some embodiments of the present invention, the structural formula of 3,3-dimethylbutyl 4-methylbenzenesulfonate is shown in VI:

[0029]

[0030] According to some embodiments of the present invention, the structural formula of 2,2-dimethyl propyl p-toluenesulfonate is shown in VII:

[0031]

[0032] According to some embodiments of the present invention, the structural formula of the 1,3-propylene glycol-di-m-toluenesulfonate is shown in VIII:

[0033]

[0034] According to some embodiments of the present invention, the structural formula of n-butyl p-toluenesulfonate is shown in IX:

[0035]

[0036] According to some embodiments of the present invention, the carbonate organic solvent includes: cyclic carbonate and linear carbonate.

[0037] According to some embodiments of the present invention, the cyclic carbonate includes at least one of ethylene carbonate, ethylene glycol propylene ether, propane carbonate and butane carbonate.

[0038] According to some embodiments of the present invention, the linear carbonate includes one of diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate.

[0039] According to some embodiments of the present invention, the carboxylate organic solvent includes at least one of ethyl acetate, propyl acetate, ethyl propionate and propyl propionate.

[0040] According to some embodiments of the present invention, the organic solvent includes: ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate and ethyl propionate.

[0041] According to some embodiments of the present invention, the organic solvent comprises a volume ratio of ethylene carbonate: ethyl methyl carbonate: dimethyl carbonate: ethyl propionate of 2:4:2:2.

[0042] Ethylene carbonate is an essential organic solvent for film formation, and its dielectric constant is high, but its melting point is 35-38°C, and it will crystallize under low temperature conditions, so the amount should not be too much; ethyl methyl carbonate has a lower viscosity and a low melting point (-73.3°C); in addition, dimethyl carbonate also has a lower viscosity and a higher conductivity than ethyl methyl carbonate, but its melting point is 2-4°C, and it is easy to produce gas under high pressure and high temperature, so the amount added needs to be controlled; finally, ethyl propionate has good low temperature performance, a low melting point, and a high dielectric constant, but it is easy to decompose under high pressure, so the amount also needs to be controlled. The above ratio can achieve the effect of low temperature resistance of the solvent system.

[0043] The HOMO energies of EC (ethylene carbonate), EMC (ethyl methyl carbonate), DMC (dimethyl carbonate) and PTSM molecules are -8.445, -8.164, -8.21, -7.446, and the LUMO energies are 0.702, 0.843, 0.221, -1.414, respectively. Therefore, during the charge and discharge process, PTSM additives will preferentially decompose with solvent molecules to form electrolyte interface films containing sulfur compounds, such as ROSO2Li, Li2SO3 and Li2S. In addition, the aromatic radicals produced by the oxidative decomposition of PTSM will polymerize on the surface of the positive electrode to form a biphenyl structure. In the process of passivation, not only the positive electrode / electrolyte interface is stabilized, but also the conjugated structure of the benzene ring improves the conductivity and reduces the impedance of the interface. On the surface of the graphite negative electrode, when it is reduced when receiving electrons, the OS bond in PTSM is more easily broken. Through the reduction and decomposition of PTSM, sulfone radicals are generated to react with alkyl radicals, lithium ions and other substances to form sulfur-containing compounds, such as Li2S, Li2SO3 and alkyl sulfonate lithium. These sulfates have low solubility in carbonate-based electrolytes and can stably exist on the electrode interface. They also have high ionic conductivity, which is conducive to the diffusion of lithium ions through the SEI layer, and also prevents the excessive reduction and decomposition of carbonate solvents on the negative electrode graphite surface. Therefore, a stable, thin and dense solid SEI electrolyte interface film is formed at the interface of the graphite negative electrode of the lithium-ion battery, which can reduce the capacity loss caused by the loss of solvent and active lithium during the battery cycle, and reduce the interface impedance under low temperature environment. At the same time, the SEI film effectively inhibits the formation of lithium dendrites caused by charging under low temperature conditions, and significantly reduces the gas production behavior caused by the deposition of active lithium and the reaction with the electrolyte. PTSM can not only effectively reduce the decomposition of the electrolyte and the structural changes of the electrode, but also reduce the electrode interface impedance, allowing lithium ions to pass through the electrode interface faster. Therefore, lithium-ion batteries containing PTSM show better cycle performance. This makes the electrolyte containing PTSM have a broader application prospect in LiFePO4 batteries.

[0044] The reduction decomposition mechanism of PTSM additives is as follows:

[0045]

[0046] In summary, the use of PTSM additives in LiFePO4 batteries can improve the cycle capacity retention rate of lithium-ion batteries under low temperature conditions and reduce the gas production during low-temperature cycles.

[0047] According to some embodiments of the present invention, the electrolyte lithium salt includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

[0048] According to a second aspect of the present invention, a method for preparing an electrolyte with improved low-temperature performance comprises mixing raw materials for preparing the electrolyte.

[0049] According to some embodiments of the present invention, the preparation method comprises:

[0050] S1. In a glove box filled with high-purity argon, the moisture in the glove box is controlled to be below 1 ppm, and the following components are weighed in parts by weight: 70-80 parts of carbonate organic solvent, 10-20 parts of carboxylate organic solvent, 10-15 parts of electrolyte lithium salt, and 0.5-5 parts of PTSM additive;

[0051] S2. The electrolyte lithium salt, the carbonate organic solvent and the carboxylate organic solvent are stirred to form a uniform solution;

[0052] S3. Add the PTSM additive to the uniform solution described in step S2, stir evenly to obtain the electrolyte, and use a conductivity meter to measure the ion conductivity at room temperature before use.

[0053] According to some embodiments of the present invention, the mixing process is performed in a glove box, and environmental indicators in the glove box include H2O≤1ppm, O2≤1ppm.

[0054] According to a third aspect of the present invention, a lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator and the electrolyte.

[0055] According to some embodiments of the present invention, the lithium ion battery comprises a lithium iron phosphate lithium ion battery.

[0056] According to some embodiments of the present invention, the negative electrode includes at least one of soft carbon, hard carbon, artificial graphite, natural graphite, silicon-oxygen negative electrode, silicon-carbon negative electrode and lithium metal.

[0057] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0059] Figure 1 is a comparison chart of the capacity retention rate of the embodiment of the present invention and the comparative example in low temperature cycle;

[0060] Figure 2 It is a comparison chart of the capacity retention rate of the embodiment of the present invention and the comparative example under normal temperature cycle. DETAILED DESCRIPTION

[0061] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0062] Example 1

[0063] This embodiment provides an electrolyte with improved low temperature performance and a preparation method thereof. The contents of the components in this embodiment are shown in Table 1. The preparation method of the electrolyte is as follows:

[0064] S1. In a glove box filled with high-purity argon, control the moisture in the glove box to be below 1 ppm. First, weigh the components shown in Table 1 respectively;

[0065] S2. dissolving the electrolyte lithium salt in a non-aqueous organic solvent and stirring to form a uniform solution;

[0066] S3. Adding the PTSM additive to the uniform solution of step S2, stirring evenly to obtain the electrolyte, and measuring the ionic conductivity at room temperature using a conductivity meter can be used;

[0067] The PTSM additive in this embodiment is 4-propyl methylbenzenesulfonate.

[0068] Example 2

[0069] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Embodiment 1 is that the mass percentages of the components are different, as shown in Table 1, and the other conditions are the same.

[0070] Example 3

[0071] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Embodiment 1 is that the mass percentages of the components are different, as shown in Table 1, and the other conditions are the same.

[0072] Example 4

[0073] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Embodiment 1 is that the mass percentages of the components are different, as shown in Table 1, and the other conditions are the same.

[0074] Example 5

[0075] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Embodiment 1 is that the mass percentages of the components are different, as shown in Table 1, and the other conditions are the same.

[0076] Example 6

[0077] This embodiment provides an electrolyte with improved low temperature performance and a preparation method thereof. The difference between this embodiment and embodiment 1 is that the mass percentages of the components are different, the PTSM additive is isobutyl o-toluenesulfonate, as shown in Table 1, and the other conditions are the same. As shown in Table 1, the other conditions are the same.

[0078] Example 7

[0079] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Example 6 is that the PTSM additive is isoamyl p-toluenesulfonate, as shown in Table 1, and the other conditions are the same.

[0080] Example 8

[0081] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Example 6 is that the PTSM additive is 2,2-dimethylpropyl p-toluenesulfonate, as shown in Table 1, and the other conditions are the same.

[0082] Example 9

[0083] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Example 6 is that the PTSM additive is sec-butyl p-toluenesulfonate, as shown in Table 1, and the other conditions are the same.

[0084] Example 10

[0085] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Example 6 is that the PTSM additive is 3,3-dimethylbutyl 4-methylbenzenesulfonate, as shown in Table 1, and the other conditions are the same.

[0086] Embodiment 11

[0087] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Example 6 is that the PTSM additive is p-1,3-propylene glycol-di-m-toluenesulfonate, as shown in Table 1, and the other conditions are the same.

[0088] Example 12

[0089] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Example 6 is that the PTSM additive is n-butyl p-toluenesulfonate, as shown in Table 1, and the other conditions are the same.

[0090] Example 13

[0091] This embodiment provides an electrolyte with improved low-temperature performance and a preparation method thereof. The difference between this embodiment and Example 6 is that the ratio of the solvents is EC:EMC:DMC is 2:4:4, excluding EP, as shown in Table 1, and the other conditions are the same.

[0092] Comparative Example 1

[0093] This comparative example provides an electrolyte with improved low-temperature performance. The difference between this comparative example and Example 1 is that the comparative example does not include PTSM additives, and the other conditions are the same as those of Example 1.

[0094] Comparative Example 2

[0095] This comparative example provides an electrolyte with improved low-temperature performance. The difference between this comparative example and Example 1 is that the mass percentage of the PTSM additive is 0.5%, and the other conditions are the same as those of Example 1.

[0096] Comparative Example 3

[0097] This comparative example provides an electrolyte with improved low-temperature performance. The difference between this comparative example and Example 6 is that the mass percentage of the PTSM additive is 4%, and the other conditions are the same as those of Example 6.

[0098] Test Case

[0099] In the low-temperature long-cycle lithium iron phosphate battery system containing PTSM additives described in the present invention, LiFePO4 is used as the positive electrode active material, artificial graphite is used as the negative electrode, and the electrolyte containing the additive PTSM is used as the electrolyte to prepare the lithium iron phosphate battery. After the lithium battery is divided into components, the low-temperature (-20°C) and normal temperature (25°C) performance tests are carried out.

[0100] Low temperature (-20℃) performance test: In a constant temperature test box, the test temperature is -20℃, charge to 3.65V at 0.2C constant current and constant voltage, the current is less than 0.03A, leave it for 5 minutes, then discharge to 2.1V at 0.5C constant current, follow this step for 100 cycles, record the first cycle 0.5C discharge capacity C1 and the 100th cycle discharge capacity C2 step by step, low temperature cycle capacity retention rate calculation = C2 / C1*100%.

[0101] Room temperature (25℃) performance test: In a constant temperature test box, the test temperature is 25℃, charge to 3.65V with 1C constant current and constant voltage, the current is less than 0.03A, leave it for 5 minutes, then discharge to 2.1V with 1C constant current, follow this step to cycle 3000 times, record the first cycle 1C discharge capacity C3 and the 3000th cycle discharge capacity C4 step by step, 25℃ cycle capacity retention rate = C4 / C3*100%.

[0102] As an example, the lithium salt content in the following examples and the comparative examples is fixed, wherein the amount of lithium hexafluorophosphate lithium salt is 9%, the amount of lithium bis(fluorosulfonyl)imide is 3%, and the organic solvent is appropriately adjusted according to the amount of the bifunctional additive PTSM. The PTSM additive in Comparative Example 2 and Examples 1-5 is 4-methylbenzenesulfonate propyl ester, the PTSM additive in Example 6 is isobutyl o-toluenesulfonate, the PTSM additive in Example 7 is isopentyl p-toluenesulfonate, and the PTSM additive in Example 8 is 2,2-dimethyl p-toluenesulfonate propyl ester.

[0103] The mass fractions listed in the following Table 1 are the mass fractions of each component in the electrolyte.

[0104] Table 1 Effects of different contents of new additive components on battery cycle and storage performance

[0105]

[0106] The test results of low temperature cycle performance and room temperature cycle performance are shown in Table 1. The functional additive PTSM can effectively improve the low temperature and room temperature cycle performance of LiFePO4 lithium ion batteries. After 100 cycles of charge and discharge at 0.2C / 0.5C at -20°C, the cycle capacity retention rate of the embodiment containing the additive PTSM increased from 37.32% of the comparative example 1 without this additive to 88.02%; after 3000 cycles of charge and discharge at 1C at 25°C, the cycle capacity retention rate increased from 50.21% to 94.20%. In addition, the experiment found that the increase in battery thickness after the experimental group containing the additive was also smaller than that of the control group without PTSM. The above data and phenomena fully demonstrate that PTSM additives effectively form the CEI film on the positive electrode side and the SEI film on the negative electrode side during the low-temperature and room-temperature charge-discharge cycle of the LiFePO4 battery, while the film formed by the control group relying only on EC and electrolyte cannot withstand the test of charge-discharge cycles; the additive PTSM has a more obvious improvement on the cycle performance in the concentration range of 0.5%-2%, and insufficient dosage leads to poor film formation effect. Exceeding the dosage threshold will make the film thickness too large and increase the internal resistance. Therefore, within a certain range, this additive can achieve maximum benefits. The low-temperature cycle capacity retention rate of the embodiments and comparative examples of the present invention is as follows: Figure 1As shown; the room temperature cycle capacity retention rate of the embodiments of the present invention and the comparative examples is as follows Figure 2 shown.

[0107] The electrolyte additives currently used in low-temperature long-cycle lithium iron phosphate batteries are generally two or more. In comparison, the use of a single PTSM-type functional additive can also effectively improve the battery's cycle and room temperature storage performance. This is because PTSM molecules have a higher HOMO potential and a lower LUMO potential than carbonate organic solvents. Therefore, during the charge and discharge process, PTSM additives will preferentially decompose with solvent molecules to form an electrolyte interface film containing sulfur compounds, such as ROSO2Li, Li2SO3 and Li2S. In addition, some aromatic free radicals produced by PTSM oxidation and decomposition will polymerize on the positive electrode surface of the LiFePO4 material to form a biphenyl structure. In the process of passivation, not only the positive electrode / electrolyte interface is stabilized, but also the conjugated structure of the benzene ring improves the conductivity and reduces the impedance of the interface. On the surface of the graphite negative electrode, when it is reduced when receiving electrons, the O18-S15 bond in PTSM is more likely to break. Through the reduction and decomposition of PTSM, sulfone radicals are generated to react with alkyl radicals, lithium ions and other substances to form sulfur-containing compounds, such as Li2S, Li2SO3 and alkyl sulfonate lithium. These sulfates have low solubility in carbonate-based electrolytes and can stably exist on the electrode interface. They also have high ionic conductivity, which is conducive to the diffusion of lithium ions through the SEI layer, and also prevents excessive reduction and decomposition of carbonate solvents on the negative electrode graphite surface. Therefore, a stable, thin and dense solid SEI electrolyte interface film is formed at the interface of the graphite negative electrode of the LiFePO4 battery, which can reduce the capacity loss caused by the loss of solvent and active lithium during the battery cycle, and reduce the interface impedance in low temperature environments.

[0108] In order to better understand the present invention, the present invention is described more comprehensively below, and specific embodiments of the present invention are provided. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0109] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention. In addition, the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

Claims

1. An electrolyte with improved low temperature performance, characterized in that: In parts by weight, the raw materials for preparing the electrolyte include 0.6 to 5 parts of PTSM additives, 80 to 90 parts of organic solvents and 10 to 15 parts of electrolyte lithium salts; The organic solvent includes: carbonate organic solvent and carboxylate organic solvent; The structural formula of the PTSM additive is shown in Formula I: R is selected from F, Br, HSO3, p-CH3-C6H4-SO2, an alkane or cycloalkane having 1 to 6 carbon atoms; 2. The electrolyte according to claim 1, characterized in that The PTSM additives include at least one of propyl 4-methylbenzenesulfonate, isoamyl p-toluenesulfonate, isobutyl o-toluenesulfonate, sec-butyl p-toluenesulfonate, 3,3-dimethylbutyl 4-methylbenzenesulfonate, 2,2-dimethylpropyl p-toluenesulfonate, 1,3-propylene glycol-di-m-toluenesulfonate and n-butyl p-toluenesulfonate.

3. The electrolyte according to claim 1, characterized in that The carbonate organic solvent includes: cyclic carbonate and linear carbonate.

4. The electrolyte according to claim 3, characterized in that The cyclic carbonate includes at least one of ethylene carbonate and propylene carbonate; preferably, the linear carbonate includes one of diethyl carbonate, dimethyl carbonate and ethyl methyl carbonate.

5. The electrolyte according to claim 1, characterized in that The carboxylate-based organic solvent includes at least one of ethyl acetate, propyl acetate, ethyl propionate and propyl propionate.

6. The electrolyte according to claim 1, characterized in that The electrolyte lithium salt includes at least one of lithium hexafluorophosphate and lithium bis(fluorosulfonyl)imide.

7. A method for preparing an electrolyte with improved low temperature performance as claimed in any one of claims 1 to 6, characterized in that: The preparation method comprises mixing raw materials for preparing the electrolyte.

8. The preparation method according to claim 7, characterized in that: The mixing process is carried out in a glove box, and the environmental indicators in the glove box include: H2O≤1ppm, O2≤1ppm.

9. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator and the electrolyte according to any one of claims 1 to 6.

10. The lithium ion battery according to claim 9, characterized in that: The negative electrode includes at least one of soft carbon, hard carbon, artificial graphite, natural graphite, silicon-oxygen negative electrode, silicon-carbon negative electrode and lithium metal.

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