Lithium ion battery electrolyte additive, lithium ion battery electrolyte and lithium ion battery

Abstract

The application relates to the technical field of lithium ion batteries, and provides a lithium ion battery electrolyte additive, a lithium ion battery electrolyte and a lithium ion battery, wherein the additive comprises methanedisulfonic acid methylene ester and 2-allylphenyl allyl ether in a mass ratio of (0.1-1):(0.5-2); the lithium ion battery electrolyte comprises a lithium salt, an organic solvent and the additive; and the lithium ion battery comprises the lithium ion battery electrolyte. The combination of the methanedisulfonic acid methylene ester and the 2-allylphenyl allyl ether is used as the lithium ion battery additive, the two can participate in the electrode interface reaction in the battery charging and discharging process, the stable and dense interface film structure can be constructed on the negative electrode surface, the positive electrode interface stability is improved, and the electrolyte decomposition and the occurrence of the side reaction are effectively inhibited.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, specifically to a lithium-ion battery electrolyte additive, a lithium-ion battery electrolyte, and a lithium-ion battery. Background Technology

[0002] With the widespread application of lithium-ion batteries in electrochemical energy storage, electric vehicles, and other fields, their cycle life and long-term stability have received increasing attention. Especially under long-cycle conditions, the electrolyte inside the battery continuously participates in the electrode interface reaction, which can easily lead to the loss of active lithium, degradation of the electrode interface structure, and intensification of electrolyte decomposition side reactions, thereby causing capacity decay and increased internal resistance, seriously affecting the battery's service life and safety performance.

[0003] Currently, optimizing the electrolyte system is one of the important means to improve the cycle performance of lithium-ion batteries. By introducing functional additives into the electrolyte, stable solid electrolyte interphase (SEI) and positive electrode electrolyte interphase (CEI) films can be formed on the electrode surface, thereby inhibiting electrolyte decomposition, reducing side reactions, and improving interface stability. For example, additives such as fluoroethylene carbonate (FEC), vinylene carbonate (VC), ethylene sulfate (DTD), and 1,3-propane sulcolone (PS) have been widely used in commercial electrolyte systems, improving the cycle performance and rate performance of batteries to a certain extent.

[0004] However, the additives used in existing technologies are mostly single-function or single-reaction-pathways, and their effects in complex electrochemical environments are often limited. On the one hand, a single additive cannot simultaneously ensure both the stability of the negative electrode interface and the high voltage stability of the positive electrode, and is prone to gradual failure during long cycles. On the other hand, different additives may have competing reactions or mutual interference, leading to unstable interfacial film composition and thus affecting the long-term cycle performance of the battery. In addition, under harsh conditions such as high load and long cycles, traditional additive systems are unable to effectively suppress the continuous decomposition of the electrolyte and the evolution of the interfacial structure, and still cannot meet the requirements of high-performance lithium-ion batteries for long cycle life. Summary of the Invention

[0005] The present invention aims to solve the above-mentioned problems in the prior art and provide a lithium-ion battery electrolyte additive, a lithium-ion battery electrolyte, and a lithium-ion battery that can improve the cycle performance of lithium-ion batteries.

[0006] To achieve the above objectives, the first aspect of this application provides a lithium-ion battery electrolyte additive comprising methylene methane disulfonate and 2-allylphenylallyl ether in a mass ratio of (0.1~1):(0.5~2).

[0007] Preferably, the lithium-ion battery electrolyte additive described above is composed of methylene methane disulfonate and 2-allylphenyl allyl ether in a mass ratio of (0.1~1):(0.5~2).

[0008] Methylene methane disulfonate, as a sulfur-containing, highly polar additive, preferentially participates in interfacial reactions during electrochemical processes, facilitating the formation of a stable inorganic enriched interfacial layer on the electrode surface. This inhibits electrolyte decomposition and enhances interfacial stability. Simultaneously, 2-allylphenylallyl ether, containing an unsaturated allyl structure, readily undergoes reduction or polymerization reactions in the early stages of cycling, contributing to the formation of a flexible organic interfacial film on the negative electrode surface, reducing interfacial impedance and improving ion transport performance. When used in combination, these two components synergistically regulate interfacial film formation behavior during battery cycling, constructing a composite interfacial structure that combines stability and ion conductivity. This effectively suppresses side reactions and reduces continuous interfacial evolution, thereby significantly improving the cycle performance of lithium-ion batteries.

[0009] In the aforementioned lithium-ion battery electrolyte, preferably, the methylene methane disulfonate content in the additive is 0.1-1 wt% of the total electrolyte mass, and the 2-allylphenylallyl ether content is 0.5-2 wt% of the total electrolyte mass.

[0010] Preferably, in the lithium-ion battery electrolyte described above, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

[0011] Preferably, in the above-mentioned lithium-ion battery electrolyte, the lithium salt content accounts for 5 to 20 wt% of the total mass of the electrolyte.

[0012] Preferably, in the lithium-ion battery electrolyte described above, the organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0013] Preferably, the electrolyte of the present invention may also contain other additives, such as one or more of fluoroethylene carbonate, vinylene carbonate, vinyl sulfate, 1,3-propane sulphol, lithium difluorophosphate, and lithium difluorooxalate, but the electrolyte must contain both methane disulfonate and 2-allylphenylallyl ether.

[0014] A third aspect of this application provides a lithium-ion battery, including the lithium-ion battery electrolyte as described above.

[0015] Compared with the prior art, this application has the following beneficial effects:

[0016] (1) In this invention, the combination of methylene disulfonate and 2-allylphenylallyl ether is used as an additive for lithium-ion batteries. During the charging and discharging process of the battery, the two can participate in the electrode interface reaction in a synergistic manner, which is beneficial to build a stable and dense interface film structure on the negative electrode surface and improve the stability of the positive electrode interface, thereby effectively suppressing the decomposition of electrolyte and the occurrence of side reactions.

[0017] (2) The present invention uses a combination of additives containing methylene disulfonate and 2-allylphenylallyl ether. Compared with single additives, the additive combination of the present invention can achieve a more stable interface regulation effect during cycling, reduce active lithium loss and interface impedance growth, and thus significantly improve the battery capacity retention rate and cycle life.

[0018] (3) The electrolyte of the present invention has good compatibility with existing commercial electrolyte systems, and does not require significant adjustments to existing battery manufacturing processes, thus having good application prospects. Detailed Implementation

[0019] To facilitate understanding of this application, the following description will be more comprehensive and detailed in conjunction with preferred embodiments, but the scope of protection of this application is not limited to the following specific embodiments.

[0020] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of this application.

[0021] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods, and all solvents used are of analytical grade.

[0022] Methylene methane disulfonate (CAS No.: 99591-74-9) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.; 2-allylphenyl allyl ether (CAS No.: 3383-05-9) was purchased from Bailingwei Technology Co., Ltd.; lithium hexafluorophosphate (CAS No.: 21324-40-3) was purchased from Shenzhen Xinzhoubang Technology Co., Ltd.; ethylene carbonate (CAS No.: 96-49-1), dimethyl carbonate (CAS No.: 616-38-6) and methyl ethyl carbonate (CAS No.: 623-53-0) were all purchased from Sinopharm Chemical Reagent Co., Ltd.

[0023] Polyolefin membrane: Celgard 2400 membrane, 25μm thick, single-layer PP material, 41% porosity, purchased from Celgard, USA; Commercial lithium iron phosphate cathode: areal density 12 mg / cm³ 2The active substance content was 95.4 wt%, purchased from Shenzhen Kejing Zhida Technology Co., Ltd. Commercial graphite anode: areal density 5.8 mg / cm³ 2 The active substance content is 95.5 wt%, purchased from Shenzhen Kejing Zhida Technology Co., Ltd.

[0024] In the following examples and comparative examples, room temperature refers to 25±2℃.

[0025] Example 1: The lithium-ion battery electrolyte of this embodiment, based on the mass of the electrolyte, is composed of: 12 wt% lithium hexafluorophosphate, 0.5 wt% methanedisulfonate, 1.0 wt% 2-allylphenylallyl ether, and the balance organic solvent (a mixed solvent composed of ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate in a mass ratio of 3:4:3).

[0026] The method for preparing the lithium-ion battery electrolyte in this embodiment involves mixing the components in the above-mentioned formulation at uniform concentrations under a dry, inert atmosphere (nitrogen) to obtain the lithium-ion battery electrolyte.

[0027] Example 2: The only difference between the lithium-ion battery electrolyte in this embodiment and that in Example 1 is the content of additives. In this embodiment, the mass content of methylene disulfonate is 0.3 wt%, and the mass content of 2-allylphenylallyl ether is 0.8 wt%. Everything else is the same as in Example 1.

[0028] Example 3: The only difference between the lithium-ion battery electrolyte in this embodiment and that in Example 1 is the content of additives. In this embodiment, the mass content of methylene disulfonate is 0.8 wt%, and the mass content of 2-allylphenylallyl ether is 1.5 wt%. Everything else is the same as in Example 1.

[0029] Example 4: The only difference between the lithium-ion battery electrolyte in this embodiment and that in Example 1 is the content of additives. In this embodiment, the mass content of methylene disulfonate is 0.1 wt%, and the mass content of 2-allylphenylallyl ether is 1.0 wt%. Everything else is the same as in Example 1.

[0030] Example 5: The only difference between the lithium-ion battery electrolyte in this embodiment and that in Example 1 is the content of additives. In this embodiment, the mass content of methylene disulfonate is 1.0 wt%, the mass content of 2-allylphenylallyl ether is 1.0 wt%, and the rest is the same as in Example 1.

[0031] Example 6: The only difference between the lithium-ion battery electrolyte in this embodiment and that in Example 1 is the content of additives. In this embodiment, the mass content of methylene disulfonate is 0.5 wt%, and the mass content of 2-allylphenylallyl ether is 2.0 wt%. Everything else is the same as in Example 1.

[0032] Example 7: The only difference between the lithium-ion battery electrolyte in this embodiment and that in Example 1 is the content of additives. In this embodiment, the mass content of methylene disulfonate is 0.1 wt%, and the mass content of 2-allylphenylallyl ether is 0.5 wt%. Everything else is the same as in Example 1.

[0033] Example 8: The only difference between the lithium-ion battery electrolyte in this embodiment and that in Example 1 is the content of additives. In this embodiment, the mass content of methylene disulfonate is 1.0 wt%, and the mass content of 2-allylphenylallyl ether is 2.0 wt%. Everything else is the same as in Example 1.

[0034] Comparative Example 1: The lithium-ion battery electrolyte in this comparative example differs from that in Example 1 in that it does not contain methylene methane disulfonate and 2-allylphenylallyl ether; otherwise, it is the same as that in Example 1.

[0035] Comparative Example 2: The lithium-ion battery electrolyte in this comparative example differs from that in Example 1 in that it contains only 0.5 wt% methanedisulfonate in the additives and does not contain 2-allylphenylallyl ether; otherwise, it is the same as in Example 1.

[0036] Comparative Example 3: The lithium-ion battery electrolyte in this comparative example differs from that in Example 1 in that it contains only 1.0 wt% 2-allylphenylallyl ether as an additive and does not contain methylene methane disulfonate; otherwise, it is the same as in Example 1.

[0037] Comparative Example 4: The lithium-ion battery electrolyte in this comparative example differs from that in Example 1 in that the additive composition is 0.5 wt% methanedisulfonate and 1.0 wt% vinylene carbonate, and it does not contain 2-allylphenylallyl ether. The rest is the same as in Example 1.

[0038] Comparative Example 5: The lithium-ion battery electrolyte in this comparative example differs from that in Example 1 in that the additive composition is 1.0 wt% of 2-allylphenylallyl ether and 0.5 wt% of fluoroethylene carbonate, and does not contain methylene disulfonate; otherwise, it is the same as in Example 1.

[0039] Preparation of lithium-ion batteries: The lithium-ion battery electrolytes from Examples 1-8 and Comparative Examples 1-5 were respectively combined with commercial lithium iron phosphate cathodes, commercial graphite anodes, and commercial polyolefin separators to form lithium-ion batteries.

[0040] The lithium-ion batteries prepared above were subjected to performance tests, including room temperature cycle performance tests, high temperature cycle performance tests, and rate performance tests. Among these: Battery room temperature cycle performance test: The test conditions were as follows: within the voltage range of 2.5~3.65 V, the batteries were first activated 3 times at a rate of 0.1C, and then charged and discharged at a rate of 0.5C. The capacity retention rate after 100 cycles was recorded. The test results are shown in Table 1. As can be seen from Table 1, the capacity retention rate of the batteries in Examples 1-3 of this invention after 100 cycles is significantly higher than that of the comparative system, indicating that the combined use of methylene methane disulfonate and 2-allylphenylallyl ether can effectively improve the stability of the electrode / electrolyte interface, reduce side reactions during cycling, and thus significantly improve the cycle performance of the battery. Although the cycle performance of Examples 4-6 was slightly lower than that of Examples 1-3, it was still better than that of the comparative system. In Examples 7-8, the cycle performance was further reduced due to at least two parameters deviating from the optimal range, but it still showed a certain improvement effect, indicating that the additive combination of this invention has good applicability.

[0041] Electrolyte high-temperature cycling performance test: The test conditions were as follows: at 45℃, within a voltage range of 2.5~3.65 V, the electrolyte was first activated three times at a rate of 0.1C, and then charged and discharged at a rate of 0.5C. The capacity retention rate after 100 cycles was recorded. The test results are shown in Table 1. As can be seen from Table 1, under high-temperature cycling conditions, the capacity retention rate of the embodiment of the present invention is significantly better than that of the comparative system. This indicates that the additive combination of the present invention can still maintain good interfacial stability at higher temperatures, inhibit electrolyte decomposition and continuous degradation of the electrode interface, thereby improving the high-temperature cycling performance of lithium-ion batteries.

[0042] Battery rate performance test: The test conditions were as follows: at 25℃, within a voltage range of 2.5~3.65 V, the battery was first activated three times at a 0.1C rate, and then charged and discharged at 1C and 2C rates respectively. The discharge specific capacity retention rate at different rates was recorded, and the test results are shown in Table 1. As can be seen from Table 1, the embodiments of the present invention exhibited high discharge specific capacity under different rate conditions, indicating that the additive combination of the present invention is beneficial to improving the battery interface transport characteristics and reducing polarization, thereby improving the battery rate performance.

[0043] Table 1: Electrochemical performance of lithium-ion batteries prepared with electrolytes from various examples and comparative examples

[0044] The above are merely preferred embodiments of this application. It should be noted that this application is not limited to the above embodiments. For those skilled in the art, several improvements and modifications can be made without departing from the principles of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should also be considered within the scope of protection of this application.

Claims

1. A lithium-ion battery electrolyte additive, characterized in that, It includes methylene methane disulfonate and 2-allylphenylallyl ether in a mass ratio of (0.1~1):(0.5~2).

2. The lithium-ion battery electrolyte additive according to claim 1, characterized in that, It consists of methylene methane disulfonate and 2-allylphenylallyl ether in a mass ratio of (0.1~1):(0.5~2).

3. A lithium-ion battery electrolyte, comprising a lithium salt, an organic solvent, and additives, characterized in that, The additive includes the lithium-ion battery electrolyte additive as described in claim 1 or 2.

4. The lithium-ion battery electrolyte according to claim 3, characterized in that, The additive contains methylene methane disulfonate at a mass content of 0.1 to 1 wt% of the total electrolyte mass, and 2-allylphenylallyl ether at a mass content of 0.5 to 2 wt% of the total electrolyte mass.

5. The lithium-ion battery electrolyte according to claim 3, characterized in that, The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium bis(trifluoromethanesulfonyl)imide, and lithium bis(fluorosulfonyl)imide.

6. The lithium-ion battery electrolyte according to claim 3, characterized in that, The lithium salt accounts for 5 to 20 wt% of the total mass of the electrolyte.

7. The lithium-ion battery electrolyte according to claim 3, characterized in that, The organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate.

8. A lithium-ion battery, characterized in that, Includes the lithium-ion battery electrolyte as described in any one of claims 3 to 7.

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