Electrolyte for high-capacity lithium ion battery, preparation method and lithium ion battery

Abstract

The invention discloses an electrolyte for a high-capacity lithium ion battery. The electrolyte is prepared from an non-aqueous solvent, lithium hexafluorophosphate, an anode film forming additive, an air bulking inhibiting additive, a cathode surface film stabilizer and a moisture stabilizer; the anode film forming additive is prepared from one or two of fluoroethylene carbonate and vinylene carbonate which account for 1%-15% of the total mass of the electrolyte; the air bulking inhibiting additive is prepared from a sultone compound accounting for 0.5%-5% of the total mass of the electrolyte; the cathode surface film stabilizer is prepared from a lithium borate salt compound accounting for 0.2%-3% of the total mass of the electrolyte; the moisture stabilizer is prepared from one or two of triphenyl phosphite and triphenyl phosphate which account for 0.1%-1% of the total mass of the electrolyte. The electrolyte can improve the normal-temperature cycle performance and the high-temperature storage performance of the battery. Meanwhile, the invention discloses a preparation method of the electrolyte and the high-capacity lithium ion battery adopting the electrolyte.

Description

technical field [0001] The invention relates to the field of electrolytic solutions, in particular to an electrolytic solution for high-capacity lithium-ion batteries, a method for preparing the electrolytic solution, and a lithium-ion battery using the electrolytic solution. Background technique [0002] Lithium-ion battery has been a research hotspot in the field of new energy since it came out in 1999. It is widely used in electronic products such as mobile phones, digital cameras and notebook computers due to its advantages of high voltage, large capacity, no memory effect and long life. In addition, lithium-ion batteries are also directly applied to electric vehicles and hybrid electric vehicles as energy storage devices for alternative energy sources. With the development of technology, the requirements for the energy density of lithium batteries are getting higher and higher. [0003] Among the most commonly used cathode materials at present, when the nickel content...

AI Technical Summary

Problems solved by technology

[0006] In a lithium-ion battery system in which the high-nickel material is the positive electrode and the silicon-carbon composite material is the negative electrode, due to the increase of the Ni content in the high-nickel material, and during the charging process, with the increase of the charging voltage, the Ni on the surface of the high-nickel material positive electrode 3+ and Ni 4+ content increased due to the Ni 4+ It has strong oxidizing properties, not only reacts with the electrolyte, destroys the function of the electrolyte, but also may cause the cathode material to decompose and release O at a lower temperature. 2 , generate a lot of heat, and the electrolyte decomposes under high temperature conditions to generate a lot of gas, which brings safety hazards to the battery

At the same time, due to the strong water absorption of high-nickel materials, high-nickel materials are very easy to react with water in the environment during material production or cell preparation to form crystal water, which is difficult to remove when the cell is baked.

When the electrolyte is injected into the cell, the electrolyte easily reacts with the water in the material to decompose the electrolyte, which eventually leads to a decline in battery performance

Although the silicon-carbon composite negative electrode has a high specific capacity, due to the huge volume effect of silicon in the process of lithium intercalation and deintercalation, the SEI film on the surface of the negative electrode is continuously destroyed and regenerated, and at the same time, the silicon particles are broken or pulverized due to huge stress. , causing the active material on the silicon negative electrode to fall off, and the electrical contact between the active material and the current collector deteriorates, resulting in an increase in the internal resistance of the battery and poor battery performance

[0007] Chinese patent application CN201210263883.6 adopts carbonate solvent and triphenyl phosphate as additives, and Chinese patent application CN201480002062.4 adopts lithium difluorodioxalate phosphate, 1,3-propene sultone, (trimethylmethane Silyl) propyl phosphate and unsaturated esters as additives do not show effective normal temperature cycle performance, high temperature storage capacity retention rate and high temperature storage capacity recovery rate. Among them, the output of Chinese patent application CN201480002062.4 after its high temperature storage In terms of performance and low-temperature output performance testing, more emphasis is placed on short-term output effects, which cannot reflect the long-term charge-discharge performance of the battery

[0008] In view of the instability of the surface SEI film due to the strong oxidation, strong water absorption and large volume expansion of the silicon-carbon negative electrode of the high-nickel material in the lithium-ion battery system in which the high-nickel material is the positive electrode and the silicon-carbon composite material is the negative electrode, it is necessary to provide a An electrolyte that can be matched with a high-nickel positive electrode and a silicon-carbon composite negative electrode at the same time to solve the problems of poor cycle performance at room temperature, high-temperature storage capacity retention rate and high-temperature storage capacity recovery rate

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