An electrolyte for improving cycle performance and low-temperature discharge performance of a lithium ion battery

Abstract

The application discloses an electrolyte for improving the cycle performance and low-temperature discharge performance of a lithium ion battery. The battery electrolyte comprises an electrolyte, an organic solvent and a composite functional additive; the composite functional additive is a combination additive of lithium carbonate, methanedisulfonate methylene and vinylene carbonate. The composite functional additive can improve the cycle performance, low-temperature performance and safety performance of the battery, especially for the lithium ion battery with graphite, single-crystal silicon and graphite composite material or silicon monoxide and graphite composite material as the negative electrode material, can improve the capacity retention rate in the whole cycle life stage, and makes the battery have high safety, excellent cycle stability and low-temperature performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to an electrolyte that improves the cycle performance and low-temperature discharge performance of lithium-ion batteries. Background Technology

[0002] In today's information age, lithium-ion batteries have attracted widespread attention from researchers due to their unique advantages. From digital products to electric vehicles and large-scale energy storage, lithium-ion batteries are playing an increasingly important role in people's daily lives. With the development of technology, people have placed higher demands on the performance of lithium-ion batteries, which are developing towards higher energy density, longer cycle life, and lower prices.

[0003] A stable interfacial film formed on the electrode surface can effectively reduce the occurrence of side reactions at the electrode-electrolyte interface, thereby improving battery life. Using electrolyte additives is an effective way to improve the interfacial film and is widely used in the battery industry. By adding appropriate additives to the electrolyte, a stable interfacial film can be generated at the positive and negative electrode interfaces, effectively improving the battery's cycle performance. Summary of the Invention

[0004] The purpose of this invention is to provide an electrolyte that improves the cycle performance and low-temperature discharge performance of lithium-ion batteries.

[0005] An electrolyte for improving the cycle performance and low-temperature discharge performance of lithium-ion batteries, the battery electrolyte comprising an electrolyte, an organic solvent, and a composite functional additive; the organic solvent is a non-aqueous organic solvent, and the non-aqueous organic solvent is at least one selected from carbonates, carboxylic esters, propionic esters, fluoroethers, and halogenated aromatic hydrocarbons; the composite functional additive is a combination additive of lithium carbonate (Li2CO3), methylene disulfonate (MMDS), and vinylene carbonate (VC).

[0006] The carbonate is at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate.

[0007] The carboxylic acid ester is at least one of propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate, and ethyl butyrate.

[0008] The propionate is at least one of methyl propionate, ethyl propionate, and propyl propionate.

[0009] The fluoroether is a fluoroether containing 7 or fewer carbon atoms in its molecule.

[0010] The halogenated aromatic hydrocarbon is at least one selected from monofluorobenzene, difluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene, 2-fluorotoluene, and 2,4-dichlorotrifluorotoluene.

[0011] Based on the total mass of the battery electrolyte (100%), the lithium carbonate content is 0.01–0.5% by mass, the vinylene carbonate content is 1–3% by mass, and the methylene disulfonate content is 0.1–1.5% by mass.

[0012] The electrolyte is a lithium salt.

[0013] The lithium salt includes any one or a combination of at least two of LiClO4, LiPF6, LiBF4, LiTFSI, LiFSI, LiBOB, LiODFB, LiCF3SO3, or LiAsF6.

[0014] The electrolyte is composed of the following components by weight percentage: 8-49% electrolyte, 51-92% non-aqueous organic solvent, and 1.11-5% composite functional additives.

[0015] The beneficial effects of this invention are as follows: This invention utilizes lithium carbonate, methylene methane disulfonate, and vinylene carbonate as composite functional additives, which can improve the cycle performance, low-temperature performance, and safety performance of batteries. In particular, for lithium-ion batteries with graphite, composite materials of monocrystalline silicon and graphite, or composite materials of silicon suboxide and graphite as the negative electrode material, it can improve the capacity retention rate throughout the entire cycle life, giving them high safety, excellent cycle stability, and low-temperature performance. Detailed Implementation

[0016] To facilitate understanding of the present invention, a more comprehensive description will be given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0017] In the following embodiments, the positive electrode uses PVDF-S5130 binder, Super-P / KS-6 composite conductive agent (mass ratio Super-P:KS-6 = 2:1), lithium nickel cobalt manganese oxide (NCM622) ternary positive electrode material, and NMP (N-methyl-2-pyrrolidone) solvent. The negative electrode uses artificial graphite (model Shanshan P15), Super-P conductive agent, CMC solvent, H2O, and SBR binder as raw materials, and the slurry is prepared by wet slurry preparation process. The positive electrode viscosity was adjusted to 10000–13000 mPa·s, and the negative electrode viscosity was adjusted to 1500–3000 mPa·s. The designed N / P ratio was 1.12, and the capacity was 1671 mAh. The process involved coating, slicing, rolling, slitting, drying at 140°C for 8 hours, applying adhesive tape, winding the cells, drying at 80°C for 48 hours, and then filling and sealing the lithium-ion batteries according to different electrolyte formulations. The process included resting for 24 hours, formation, first final sealing, aging, and second final sealing to prepare lithium-ion soft-pack batteries. The cycle performance and safety performance of the batteries were then tested.

[0018] Example 1

[0019] An NCM622 / artificial graphite battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is a non-aqueous electrolyte and the total weight of the non-aqueous electrolyte is 100%, containing the components shown in Table 1 Example 1 by mass percentage and 13.75% LiPF6 salt.

[0020] Example 2

[0021] An NCM622 / artificial graphite battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is a non-aqueous electrolyte and the total weight of the non-aqueous electrolyte is 100%, containing the components shown in Table 1 Example 2 by mass percentage and 13.75% LiPF6 salt.

[0022] Example 3

[0023] An NCM622 / artificial graphite battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is a non-aqueous electrolyte and the total weight of the non-aqueous electrolyte is 100%, containing the components shown in Table 1 Example 3 by mass percentage and 13.75% LiPF6 salt.

[0024] Example 4

[0025] An NCM622 / artificial graphite battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is a non-aqueous electrolyte and the total weight of the non-aqueous electrolyte is 100%, containing the components shown in Table 1 Example 4 by mass percentage and 13.75% LiPF6 salt.

[0026] Example 5

[0027] An NCM622 / artificial graphite battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is a non-aqueous electrolyte and the total weight of the non-aqueous electrolyte is 100%, containing the components shown in Table 1 Example 5 by mass percentage and 13.75% LiPF6 salt.

[0028] Comparative Examples 1-6

[0029] An NCM622 / artificial graphite battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the electrolyte is a non-aqueous electrolyte and the total weight of the non-aqueous electrolyte is 100%, containing the components shown in the mass percentages of Comparative Examples 1-6 in Table 1 and 13.75% LiPF6 salt.

[0030] Table 1

[0031]

[0032]

[0033] Lithium-ion batteries prepared using 622 nickel-cobalt-manganese ternary material as the positive electrode material and the electrolyte formulations of Examples 1 to 5 and the comparative example were tested for cycle performance, high-temperature storage performance and low-temperature discharge performance. The test results are shown in the table below.

[0034] Table 2. Room temperature cycling performance of lithium-ion batteries prepared with electrolytes from the examples and comparative examples.

[0035]

[0036] Table 3. Low-temperature discharge performance of lithium-ion batteries prepared with electrolytes from the examples and comparative examples.

[0037]

[0038]

[0039] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. An electrolyte for improving cycle performance and low-temperature discharge performance of a lithium-ion battery, characterized by comprising: The electrolyte comprises an electrolyte, an organic solvent and a composite functional additive; the organic solvent is a non-aqueous organic solvent, the non-aqueous organic solvent is at least one of carbonates, carboxylic acid esters, fluorine ethers and halogenated aromatic hydrocarbons; the composite functional additive is a combination of lithium carbonate, methanediyl bis(methanesulfonate) and vinylene carbonate; The mass percentage of the lithium carbonate is 0.01-0.5%, the mass percentage of the vinylene carbonate is 1-3%, and the mass percentage of the methanediyl bis(methanesulfonate) is 0.1-1.5%, based on the total mass of the electrolyte being 100%.

2. The electrolyte for improving cycle performance and low-temperature discharge performance of a lithium-ion battery according to claim 1, wherein The carbonates are at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate and methyl ethyl carbonate.

3. The electrolyte for improving cycle performance and low-temperature discharge performance of a lithium-ion battery according to claim 1, wherein The carboxylic acid esters are at least one of propyl butyrate, propyl acetate, isopropyl acetate, butyl propionate, isopropyl propionate and ethyl butyrate.

4. The electrolyte for improving cycle performance and low-temperature discharge performance of a lithium-ion battery according to claim 1, wherein The fluorine ethers are fluorine ethers containing 7 carbons or less in the molecule.

5. The electrolyte for improving cycle performance and low-temperature discharge performance of a lithium-ion battery according to claim 1, wherein The halogenated aromatic hydrocarbons are at least one of monofluorobenzene, difluorobenzene, 1,3,5-trifluorobenzene, trifluorotoluene and 2,4-dichlorotrifluorotoluene.

6. The electrolyte for improving cycle performance and low-temperature discharge performance of a lithium-ion battery according to claim 1, wherein The electrolyte is a lithium salt.

7. The electrolyte for improving cycle performance and low-temperature discharge performance of a lithium-ion battery according to claim 6, wherein The lithium salt comprises any one or a combination of at least two of LiClO4, LiPF6, LiBF4, LiTFSI, LiFSI, LiBOB, LiODFB, LiCF3SO3 and LiAsF6.

8. The electrolyte for improving cycle performance and low-temperature discharge performance of a lithium-ion battery according to claim 1, wherein The electrolyte is composed of the following components in the following weight percentages: electrolyte 8-49%, non-aqueous organic solvent 51-92% and composite functional additive 1.11-5%.

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