Non-aqueous lithium battery electrolyte and secondary lithium battery

Abstract

The present application relates to a kind of non-aqueous lithium battery electrolyte, mainly solve the non-aqueous lithium battery electrolyte due to the existence of multiple additives and the problem of non-aqueous lithium battery electrolyte instability, cannot long-term storage problem.The present application by adding lithium sulfamate in the non-aqueous lithium battery electrolyte containing multiple additives, can inhibit the decomposition of additive due to the interaction between each substance of non-aqueous lithium battery electrolyte, improve the stability of non-aqueous lithium battery electrolyte, so that non-aqueous lithium battery electrolyte can be long-term storage, while the secondary lithium battery prepared using the non-aqueous lithium battery electrolyte has better cycle performance.

Description

Technical Field

[0001] This invention relates to a non-aqueous lithium battery electrolyte and a secondary lithium battery. Background Technology

[0002] Electrolytes, a crucial component of lithium-ion batteries, consist of lithium salts and organic solvents. Current technologies often incorporate additives into electrolytes to enhance lithium-ion battery performance. As performance requirements for lithium-ion batteries become increasingly stringent, the variety of additives used in electrolytes has also increased. While the synergistic effect of multiple additives can improve lithium-ion battery performance, interactions can easily occur between different types of additives, and between additives and organic solvents or lithium salts. The more types of additives added, the more pronounced these interactions become, potentially leading to the decomposition of some or all of the additives. Furthermore, this decomposition worsens with prolonged electrolyte storage. Once additives decompose, a range of electrolyte properties deteriorate, ultimately impacting the performance of the lithium-ion battery. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a non-aqueous lithium battery electrolyte with good stability and excellent cycle performance, and a secondary lithium battery. The non-aqueous lithium battery electrolyte can also be stored for a long time even when it contains a variety of different additives.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] This invention provides a non-aqueous lithium battery electrolyte, which includes lithium salt, organic solvent, and additives. The additives include a first additive, a second additive, and a third additive. The first additive is selected from one or more fluorine-containing compounds. The second additive includes one or more vinyl sulfate and vinylene carbonate. The third additive is lithium aminosulfonate.

[0006] Preferably, the lithium aminosulfonate content in the non-aqueous lithium battery electrolyte is 0.1-0.5% by mass.

[0007] More preferably, the lithium aminosulfonate content in the non-aqueous lithium battery electrolyte is 0.1% to 0.3% by mass, for example, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, etc. A higher lithium aminosulfonate content effectively inhibits the decomposition of additives in the electrolyte. However, the solubility of lithium aminosulfonate in organic solvents is limited. Therefore, if the lithium aminosulfonate content is too high, it will cause lithium aminosulfonate to precipitate from the organic solvent, thereby affecting the performance of the electrolyte.

[0008] Preferably, the fluorinated compounds include fluoroethylene carbonate, lithium difluorooxalate borate, and lithium difluorosulfonyl imide.

[0009] More preferably, the fluoroethylene carbonate content in the non-aqueous lithium battery electrolyte is 0.5% to 2%, for example, it can be 0.5%, 0.8%, 1.0%, 1.3%, 1.5%, 1.8%, etc.

[0010] More preferably, the lithium difluorooxalate borate content in the non-aqueous lithium battery electrolyte is 0.5% to 2%, for example, it can be 0.5%, 0.8%, 1.0%, 1.3%, 1.5%, 1.8%, etc.

[0011] More preferably, the lithium bisfluorosulfonylimide in the non-aqueous lithium battery electrolyte has a mass content of 1-6%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, etc.

[0012] Preferably, the ethylene sulfate content in the non-aqueous lithium battery electrolyte is 0.5% to 2%, for example, it can be 0.5%, 0.8%, 1.0%, 1.3%, 1.5%, 1.8%, etc.

[0013] Preferably, the vinylene carbonate content in the non-aqueous lithium battery electrolyte is 0.5% to 2%, for example, it can be 0.5%, 0.8%, 1.0%, 1.3%, 1.5%, 1.8%, etc.

[0014] According to some specific and preferred embodiments, the additives include fluoroethylene carbonate, lithium difluorooxalate borate, lithium difluorosulfonyl imide, ethylene sulfate, vinylene carbonate, and lithium aminosulfonate.

[0015] Preferably, the lithium salt is selected from one or more of LiPF6, LiTFSI, LiBF4, LiClO4, LiCH3SO3, LiSCN, LiNO3, LiO3SCF2CF3, LiAsF6, and LiAlCl4.

[0016] More preferably, the concentration of the lithium salt in the non-aqueous lithium battery electrolyte is 0.5–2 mol / L.

[0017] Preferably, the organic solvent is selected from one or more of carbonates, carboxylic esters, ethers, and sulfones.

[0018] More preferably, the carbonate is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and propylene carbonate.

[0019] More preferably, the carboxylic acid ester is one or more selected from methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, ethyl propionate, methyl butyrate, and ethyl butyrate.

[0020] More preferably, the ether is selected from one or more of dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, and 1,3-dioxolane.

[0021] More preferably, the sulfone is selected from one or more of dimethyl sulfoxide, sulfolane, and dimethyl sulfone.

[0022] According to some preferred embodiments, the organic solvent includes ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, and propylene carbonate, wherein the mass ratio of ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate, and propylene carbonate is (1-3):(3-6):(1-2):1.

[0023] A second aspect of the present invention provides a secondary lithium battery comprising the non-aqueous lithium battery electrolyte as described above.

[0024] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art:

[0025] The non-aqueous lithium battery electrolyte of this invention has good stability and can be stored for a long time under certain conditions without deterioration due to the decomposition of additives. At the same time, the secondary lithium battery made using this non-aqueous lithium battery electrolyte has better cycle performance. Detailed Implementation

[0026] To improve battery performance, an increasing variety of additives are being applied to non-aqueous lithium-ion battery electrolytes. However, with the increasing number of additives, interactions between the various substances in the electrolyte can easily occur, leading to the decomposition of some substances, especially additives. The longer the electrolyte is stored, the more severe the decomposition. This invention unexpectedly discovered that by adding lithium sulfamate to a non-aqueous lithium-ion battery electrolyte, the decomposition of additives caused by interactions between the various substances in the electrolyte can be suppressed, thus improving the stability of the electrolyte and enabling long-term storage. Furthermore, secondary lithium-ion batteries made using this electrolyte exhibit better cycle performance.

[0027] This invention provides a non-aqueous lithium battery electrolyte, comprising lithium salt, organic solvent, and additives. The additives include a first additive, a second additive, and a third additive. The first additive is selected from one or more fluorine-containing compounds; the second additive includes one or more vinyl sulfate and vinylene carbonate; and the third additive is lithium aminosulfonate.

[0028] According to some specific and preferred embodiments, a non-aqueous lithium battery electrolyte includes a lithium salt, an organic solvent, and additives, wherein the additives include fluoroethylene carbonate, lithium difluorooxalate borate, lithium difluorosulfonyl imide, ethylene sulfate, vinylene carbonate, and lithium aminosulfonate, and the mass content of lithium aminosulfonate in the non-aqueous lithium battery electrolyte is 0.1-0.5%.

[0029] The solution of the present invention has at least the following advantages:

[0030] (1) The non-aqueous lithium battery electrolyte of the present invention has good stability and excellent cycle performance, and can be stored for a long time (30 days or more) at 10°C.

[0031] (2) Electrolytes are usually prepared in a closed glove box and immediately injected into the battery pack for use after preparation. Generally, they are prepared on demand. The solution of this invention can suppress the decomposition caused by the combined use of multiple additives, so that the non-aqueous lithium battery electrolyte can not only be stored, but also stored for a long time. This eliminates the need for on-demand preparation of the non-aqueous lithium battery electrolyte, providing convenience for the preparation of secondary lithium batteries.

[0032] The present invention will be further described below with reference to embodiments. However, the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to different requirements of specific applications, and the implementation conditions not specified are conventional conditions in the industry. The technical features involved in the various embodiments of the present invention can be combined with each other as long as they do not conflict with each other.

[0033] In their actual research, the inventors discovered that when multiple additives are added to the electrolyte, interactions occur between these additives, leading to changes in the electrolyte system. The relevant research is as follows.

[0034] Compare with Example 1

[0035] Preparation of basic electrolyte:

[0036] A basic electrolyte was prepared by dissolving lithium salt LiPF6 in a mixed solvent of ethylene carbonate / ethyl methyl carbonate / dimethyl carbonate / propylene carbonate (mass ratio 25 / 50 / 15 / 10), wherein the concentration of LiPF6 was 1 mol / L.

[0037] Compare with Example 2-13

[0038] The difference from Comparative Example 1 is that the basic electrolyte also contains the additives shown in Table 1 below. Unless otherwise specified, FEC refers to fluoroethylene carbonate, VC refers to vinylene carbonate, LiFSI refers to lithium difluorosulfonylimide, LiODFB refers to lithium difluorooxalate borate, DTD refers to vinyl sulfate, and PS refers to 1,3-propanesulfonate lactone.

[0039] Table 1

[0040] Compare with Example 1 / / / / / / Compare with Example 2 0.50％ / / / / / Compare with Example 3 / 0.50％ / / / / Compare with Example 4 / / 5.00％ / / / Compare with Example 5 / / / 0.50％ / / Compare with Example 6 / / / / 0.50％ / Compare with Example 7 0.50％ / / 0.50％ / / Compare with Example 8 0.50％ / 5.00％ / / / Compare with Example 9 0.50％ / 5.00％ 0.50％ / / Compare with Example 10 0.50％ 0.50％ 5.00％ 0.50％ / / Compare with Example 11 0.50％ 0.50％ 5.00％ / 0.50％ / Compare with Example 12 0.50％ 0.50％ 5.00％ 0.50％ 0.50％ / Compare with Example 13 0.50％ 0.50％ 5.00％ 0.50％ 0.50％ 0.50％

[0041] The electrolytes in Comparative Examples 1-13 were stored at 10°C, and the contents of H2O and HF in the electrolytes were tested at different storage times. The results are shown in Table 2 below.

[0042] Table 2

[0043]

[0044]

[0045] As shown in Table 2, the HF content in the electrolyte increases with the increase of the number of additives, especially when FEC, VC, LiFSI, LiODFB, and DTD are present in the electrolyte simultaneously, where the increase in HF is particularly severe. Furthermore, the increased content of H2O and / or HF in the electrolyte leads to a decline in battery performance and may even render the electrolyte unusable.

[0046] The component content of the electrolyte in some control examples was analyzed under different storage times, and the results are shown in Table 3.

[0047] Table 3

[0048]

[0049] As shown in Table 3, when FEC, VC, LiFSI, LiODFB and DTD are present in the electrolyte at the same time, the decomposition of FEC, LiFSI and LiODFB is particularly severe.

[0050] This invention inhibits electrolyte degradation by adding lithium aminosulfonate, and the inhibitory effect improves with increasing lithium aminosulfonate content. Related research is as follows.

[0051] Examples 1 to 3

[0052] The difference from Comparative Example 1 is that the electrolyte also includes the additives shown in Table 4 below.

[0053] Table 4

[0054] Example 1 0.50％ 0.50％ 5.00％ 0.50％ 0.50％ 0.10％ Example 2 0.50％ 0.50％ 5.00％ 0.50％ 0.50％ 0.20％ Example 3 0.50％ 0.50％ 5.00％ 0.50％ 0.50％ 0.30％

[0055] The electrolytes from Examples 1 to 3 were stored at 10°C, and the contents of H2O and HF in the electrolytes were tested at different storage times. The results are shown in Table 5 below.

[0056] Table 5

[0057]

[0058] It can be seen that the addition of lithium aminosulfonate can inhibit the deterioration of the electrolyte, and the inhibitory effect becomes better with the increase of the amount added.

[0059] The component content of the electrolyte in some control examples was analyzed for different storage times, and the results are shown in Table 6.

[0060] Table 6

[0061]

[0062]

[0063] It is evident that the addition of lithium aminosulfonate can inhibit the decomposition of additives, thereby inhibiting the degradation of the electrolyte.

[0064] After the electrolytes of the above comparative examples and embodiments were prepared, they were immediately injected into the same batch of lithium cobalt oxide pouch batteries (1.1Ah LCO / graphite, purchased from Xi'an Serfu) to prepare lithium cobalt oxide batteries. The batteries were then subjected to 1C cycle tests at room temperature (25°C) at 2.75-4.2V. The test results are shown in Table 7.

[0065] Table 7

[0066] Compare with Example 1 86.2 Compare with Example 2 89.3 Compare with Example 3 90.2 Compare with Example 4 90.1 Compare with Example 5 89.2 Compare with Example 6 88.6 Compare with Example 7 92.3 Compare with Example 8 92.1 Compare with Example 9 93.2 Compare with Example 10 93.9 Compare with Example 11 93.6 Compare with Example 12 95.3 Compare with Example 13 96.3 Example 1 97.2 Example 2 97.5 Example 3 98.2

[0067] After the electrolytes of the above comparative examples and embodiments were prepared, they were stored at 10°C for 10 days and then injected into the same batch of lithium cobalt oxide soft-pack batteries to obtain lithium cobalt oxide batteries. The batteries were then subjected to a 1C cycle test at room temperature (25°C) at 2.75-4.2V. The test results are shown in Table 8.

[0068] Table 8

[0069] Example 1 96.9 Example 2 97.6 Example 3 98.0

[0070] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A non-aqueous lithium battery electrolyte, wherein the non-aqueous lithium battery electrolyte comprises lithium salt, organic solvent and additives, characterized in that: The additives include fluoroethylene carbonate, lithium difluorooxalate borate, lithium difluorosulfonyl imide, ethylene sulfate, vinylene carbonate, and lithium aminosulfonate. The fluoroethylene carbonate has a mass content of 0.5-2% in the non-aqueous lithium battery electrolyte, the lithium difluorooxalate borate has a mass content of 0.5-2% in the non-aqueous lithium battery electrolyte, the lithium difluorosulfonyl imide has a mass content of 1-6% in the non-aqueous lithium battery electrolyte, the ethylene sulfate has a mass content of 0.5-2% in the non-aqueous lithium battery electrolyte, the vinylene carbonate has a mass content of 0.5-2% in the non-aqueous lithium battery electrolyte, and the lithium aminosulfonate has a mass content of 0.1-0.5% in the non-aqueous lithium battery electrolyte.

2. The non-aqueous lithium battery electrolyte according to claim 1, characterized in that: The lithium aminosulfonate content in the non-aqueous lithium battery electrolyte is 0.1~0.3% by mass.

3. The non-aqueous lithium battery electrolyte according to claim 1, characterized in that: The lithium salt is selected from one or more of LiPF6, LiTFSI, LiBF4, LiClO4, LiCH3SO3, LiSCN, LiNO3, LiO3SCF2CF3, LiAsF6, and LiAlCl4; and / or, The concentration of the lithium salt in the non-aqueous lithium battery electrolyte is 0.5–2 mol / L.

4. The non-aqueous lithium battery electrolyte according to claim 1, characterized in that: The organic solvent is selected from one or more of carbonates, carboxylic acid esters, ethers, and sulfones; The carbonate is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and propylene carbonate. The carboxylic acid ester is one or more selected from methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, ethyl propionate, methyl butyrate, and ethyl butyrate. The ether is selected from one or more of dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, and 1,3-dioxolane; The sulfone is selected from one or more of dimethyl sulfoxide, sulfolane, and dimethyl sulfone.

5. A secondary lithium battery, characterized in that: Includes the non-aqueous lithium battery electrolyte as described in any one of claims 1 to 4.

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