A high temperature resistant lithium ion battery electrolyte

Abstract

The present invention belongs to the technical field of battery electrolytes, and proposes a high temperature resistant lithium ion battery electrolyte, including an electrolyte, a solvent and an additive, wherein the additive includes a first additive and a second additive, wherein the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, and the second additive is 3-pyridine boric acid methyliminodiacetate. The mass ratio of the first additive to the second additive is (3.3-5.8):1, and the mass ratio of the electrolyte to the solvent and the additive is (15-20):(50-65):(0.05-5). Through the above technical scheme, the problem of poor high temperature resistance of battery electrolytes in the prior art is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of battery electrolytes and relates to a high temperature resistant lithium ion battery electrolyte. Background Art

[0002] The electrolyte is one of the important components of the battery. It plays the role of transmitting ions between the positive and negative electrodes of the battery, and has an important impact on the battery's capacity, cycle performance, safety performance and other characteristics. The electrolyte mainly consists of two parts: organic solvent and electrolyte lithium salt. In order to improve battery performance, some auxiliary additives such as film-forming additives, flame retardant additives, and overcharge protection additives are often added to the lithium-ion battery electrolyte. Additives can improve one or several properties of the battery without changing the battery process and cost. They have the characteristics of small dosage, strong targeting, and fast onset.

[0003] During the use of lithium-ion batteries, the internal temperature can reach above 80°C during continuous charge and discharge, especially at high rate discharge. Under this temperature, ordinary electrolytes will decompose rapidly, causing battery performance to deteriorate and even damage. In order to ensure the performance of the battery at high temperatures, it is necessary to improve the high temperature stability of the electrolyte and reduce the decomposition of the electrolyte at high temperatures, thereby ensuring the safety of lithium-ion batteries at high temperatures. Summary of the invention

[0004] The present invention provides a high temperature resistant lithium ion battery electrolyte, which solves the problem of poor high temperature resistance of the battery electrolyte in the prior art.

[0005] The technical solution of the present invention is achieved in this way:

[0006] A high temperature resistant lithium ion battery electrolyte comprises an electrolyte, a solvent and an additive, wherein the additive comprises a first additive and a second additive, wherein the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, and the second additive is 3-pyridine boric acid methyliminodiacetate.

[0007] As a further technical solution, the 1,3,2,4-dioxathiazole-2,2-dioxide compound is selected from one or more of the compounds shown in formula I:

[0008]

[0009] R is a straight chain alkyl group of 1 to 6 carbon atoms or a phenyl group.

[0010] As a further technical solution, the mass ratio of the first additive to the second additive is (3.3-5.8):1.

[0011] As a further technical solution, the mass ratio of the electrolyte to the solvent and the additive is (15-20): (50-65): (0.05-5).

[0012] As a further technical solution, the electrolyte is one or more of LiPF6, LiBF4, LiSO3CF3, LiClO4, LiN(CF3SO2)2, and LiC(CF3SO2)3.

[0013] As a further technical solution, the solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propionate, ethyl propionate, propyl propionate, methyl trifluoroacetate, ethyl trifluoroacetate, and butyl trifluoroacetate.

[0014] The working principle and beneficial effects of the present invention are:

[0015] 1. In the present invention, the high temperature resistance of the battery electrolyte is significantly improved by optimizing the composition design of the battery electrolyte, so that the battery electrolyte of the present invention will not cause flatulence after being injected into the lithium ion battery and stored at 80°C for 7 days, and the battery capacity retention rate after storage at 80°C for 7 days is 97.68% to 98.83%, and the capacity retention rate at 100% discharge depth is significantly improved after 300 and 500 cycles at 80°C, which effectively solves the problem of poor high temperature resistance of the battery electrolyte in the prior art.

[0016] 2. In the present invention, the first additive and the second additive in a specific mass ratio in the battery electrolyte are synergistically matched, which significantly improves the thermal stability of the battery electrolyte, so that the battery electrolyte of the present invention has good high temperature resistance, thereby improving the safety and characteristics of the lithium battery at high temperatures. DETAILED DESCRIPTION

[0017] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Example 1

[0019] A high temperature resistant lithium ion battery electrolyte comprises an electrolyte, a solvent and an additive in a mass ratio of 15:50:3, wherein the electrolyte is LiPF6, the solvent is ethylene carbonate, the additive is composed of a first additive and a second additive in a mass ratio of 3.3:1, the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, the second additive is 3-pyridine boric acid methyliminodiacetate, and the 1,3,2,4-dioxathiazole-2,2-dioxide compound has the following structural formula II:

[0020]

[0021] Example 2

[0022] A high temperature resistant lithium ion battery electrolyte comprises an electrolyte, a solvent and an additive in a mass ratio of 15:50:3, wherein the electrolyte is LiPF6, the solvent is ethylene carbonate, the additive is composed of a first additive and a second additive in a mass ratio of 3.3:1, the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, the second additive is 3-pyridine boric acid methyliminodiacetate, and the 1,3,2,4-dioxathiazole-2,2-dioxide compound has the following structural formula III:

[0023]

[0024] Example 3

[0025] A high temperature resistant lithium ion battery electrolyte comprises an electrolyte, a solvent and an additive in a mass ratio of 15:50:3, wherein the electrolyte is LiPF6, the solvent is ethylene carbonate, the additive is composed of a first additive and a second additive in a mass ratio of 3.3:1, the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, the second additive is 3-pyridine boric acid methyliminodiacetate, and the 1,3,2,4-dioxathiazole-2,2-dioxide compound has the following structural formula V:

[0026]

[0027] Example 4

[0028] A high temperature resistant lithium ion battery electrolyte comprises an electrolyte, a solvent and an additive in a mass ratio of 4:13:1, wherein the electrolyte is LiSO3CF3, the solvent is propylene carbonate, and the additive is composed of a first additive and a second additive in a mass ratio of 3.3:1, the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, the second additive is 3-pyridine boric acid methyliminodiacetate, and the 1,3,2,4-dioxathiazole-2,2-dioxide compound has the following structural formula II:

[0029]

[0030] Example 5

[0031] A high temperature resistant lithium ion battery electrolyte comprises an electrolyte, a solvent and an additive in a mass ratio of 15:50:0.05, wherein the electrolyte is LiN(CF3SO2)2, the solvent is ethyl methyl carbonate, the additive is composed of a first additive and a second additive in a mass ratio of 5:1, the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, the second additive is 3-pyridine boric acid methyliminodiacetate, and the 1,3,2,4-dioxathiazole-2,2-dioxide compound has the following structural formula II:

[0032]

[0033] Example 6

[0034] A high temperature resistant lithium ion battery electrolyte comprises an electrolyte, a solvent and an additive in a mass ratio of 18:60:1, wherein the electrolyte is LiBF4, the solvent is ethyl propionate, and the additive is composed of a first additive and a second additive in a mass ratio of 4:1, the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, the second additive is 3-pyridine boric acid methyliminodiacetate, and the 1,3,2,4-dioxathiazole-2,2-dioxide compound has the following structural formula II:

[0035]

[0036] Example 7

[0037] A high temperature resistant lithium ion battery electrolyte comprises an electrolyte, a solvent and an additive in a mass ratio of 15:50:2, wherein the electrolyte is LiPF6, the solvent is methyl trifluoroacetate, the additive is composed of a first additive and a second additive in a mass ratio of 4.5:1, the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, the second additive is 3-pyridine boric acid methyliminodiacetate, and the 1,3,2,4-dioxathiazole-2,2-dioxide compound has the following structural formula II:

[0038]

[0039] Example 8

[0040] A high temperature resistant lithium ion battery electrolyte comprises an electrolyte, a solvent and an additive in a mass ratio of 5:20:1, wherein the electrolyte is LiClO4, the solvent is propyl propionate, and the additive is composed of a first additive and a second additive in a mass ratio of 5.8:1, the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, the second additive is 3-pyridine boric acid methyliminodiacetate, and the 1,3,2,4-dioxathiazole-2,2-dioxide compound has the following structural formula II:

[0041]

[0042] Example 9

[0043] A high temperature resistant lithium ion battery electrolyte comprises an electrolyte, a solvent and an additive in a mass ratio of 15:50:3, wherein the electrolyte is LiC(CF3SO2)3, the solvent is ethyl methyl carbonate, and the additive is composed of a first additive and a second additive in a mass ratio of 3.3:1, the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, the second additive is 3-pyridine boric acid methyliminodiacetate, and the 1,3,2,4-dioxathiazole-2,2-dioxide compound has the following structural formula II:

[0044]

[0045] Comparative Example 1

[0046] The difference between this comparative example and Example 1 is that the additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound of the following structural formula II:

[0047]

[0048] Comparative Example 2:

[0049] The difference between this comparative example and Example 1 is that the additive is 3-pyridine boric acid methyliminodiacetate.

[0050] After the electrolytes of Examples 1 to 9 and Comparative Examples 1 to 2 were injected into lithium cobalt oxide / graphite system lithium batteries, the 80°C high temperature test data are shown in Table 1:

[0051] Table 1 80℃ high temperature storage performance of batteries

[0052] project 80℃, 7 days, whether there is bloating 80℃, capacity retention after 7 days % Example 1 no 98.55 Example 2 no 97.68 Example 3 no 98.46 Example 4 no 98.71 Example 5 no 97.92 Example 6 no 98.37 Example 7 no 98.83 Example 8 no 98.45 Example 9 no 98.29 Comparative Example 1 yes 90.16 Comparative Example 2 yes 90.27

[0053] As can be seen from Table 1, after the electrolytes of Examples 1 to 9 were injected into lithium ion batteries and stored at 80°C for 7 days, no flatulence occurred, and the battery capacity retention rate after storage at 80°C for 7 days was 97.68% to 98.83%. However, after the electrolytes of Comparative Examples 1 to 2 were injected into lithium ion batteries and stored at 80°C for 7 days, flatulence occurred, and the battery capacity retention rate after storage at 80°C for 7 days was only 90.16% to 90.27%, indicating that the battery electrolyte of the present invention significantly improves the capacity retention rate of the battery at high temperatures.

[0054] After the electrolytes of Examples 1 to 9 and Comparative Examples 1 to 2 were injected into lithium cobalt oxide / graphite system lithium batteries, the 80°C high temperature cycle capacity retention data were shown in Table 2:

[0055] Table 2 80℃ battery high temperature cycle capacity retention performance

[0056]

[0057] It can be seen from the data in Table 2 that compared with the electrolytes of Comparative Examples 1 to 2, after using the electrolytes of Examples 1 to 9, the battery is cycled 300 times and 500 times at a high temperature of 80°C and the capacity retention rate at 100% discharge depth is significantly improved, indicating that the electrolyte of the present invention has good thermal stability and good high temperature resistance, thereby improving the safety and characteristics of the lithium battery at high temperatures.

[0058] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high temperature resistant lithium ion battery electrolyte, characterized in that: The invention comprises an electrolyte, a solvent and an additive, wherein the additive comprises a first additive and a second additive, wherein the first additive is a 1,3,2,4-dioxathiazole-2,2-dioxide compound, and the second additive is 3-pyridine boric acid methyliminodiacetate; The 1,3,2,4-dioxathiazole-2,2-dioxide compound is selected from one or more of the compounds shown in formula I: R is a straight chain alkyl group of 1 to 6 carbon atoms or a phenyl group.

2. A high temperature resistant lithium ion battery electrolyte according to claim 1, characterized in that: The mass ratio of the first additive to the second additive is (3.3-5.8):

1.

3. A high temperature resistant lithium ion battery electrolyte according to claim 1, characterized in that: The mass ratio of the electrolyte to the solvent and the additive is (15-20): (50-65): (0.05-5).

4. The high temperature resistant lithium ion battery electrolyte according to claim 1, characterized in that: The electrolyte is one or more of LiPF6, LiBF4, LiSO3CF3, LiClO4, LiN(CF3SO2)2, and LiC(CF3SO2)3.

5. The high temperature resistant lithium ion battery electrolyte according to claim 1, characterized in that: The solvent is one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propionate, ethyl propionate, propyl propionate, methyl trifluoroacetate, ethyl trifluoroacetate, and butyl trifluoroacetate.

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