Electrolyte of high-voltage lithium ion battery

Abstract

The invention provides an electrolyte for a high-voltage lithium ion battery, and belongs to the field of a lithium ion battery. The electrolyte comprises a non-aqueous organic solvent, a lithium saltand an additive, wherein the non-aqueous organic solvent is an ester solvent, the mass percent of the non-aqueous organic solvent accounts for 95% or above, the lithium salt is LiPF6, the concentration of the lithium salt is (1.0-1.5)mol / L, the additive is a mixture of a dinitrile compound and a boron-containing compound, and the mass percent of the additive accounts for 1-5%. The electrolyte employing the mixture of the dinitrile compound and borate as an electrolyte additive is applicable to a high-voltage positive electrode material LiNi<0.5>Mn<1.5>O<4> system, it is found that the interface impedance of the lithium ion battery positive electrode material can be improved by such the electrolyte, and moreover, the cycle stability of the lithium ion battery under a normal temperature isimproved.

Description

technical field [0001] The invention belongs to the field of lithium-ion batteries, and relates to an electrolyte solution suitable for high-voltage lithium-ion batteries. Background technique [0002] Lithium-ion batteries have the advantages of high voltage, high specific energy, long cycle life and good safety. Since Sony commercialized them in the 1990s, lithium-ion batteries have been widely used in mobile phones, digital cameras and notes, etc. Portable devices, especially in recent years, have been widely used in large electric vehicles and energy storage devices, and the energy density requirements of lithium-ion batteries are also getting higher and higher. [0003] The use of high charge cut-off potential cathode materials is one of the main ways to increase the energy density of lithium-ion batteries. The high charge cut-off potential cathode materials mainly include LiNi 0.5 mn 1.5 o 2 (4.7V vs. Li / Li + ), LiCoPO 4 (4.8V vs. Li / Li + ) and LiNiPO 4 (5.1V vs...

AI Technical Summary

Problems solved by technology

[0004] However, the current commercial lithium-ion battery electrolytes mainly use carbonates and carboxylates as solvents. When the charging voltage of this type of electrolyte exceeds 4.5V, LiPF 6 Will accelerate the decomposition to generate HF and PF 5 , the former will react with the positive active material to dissolve metal ions in the electrolyte and cause capacity loss, while the latter will lead to oxidative decomposition or even polymerization of organic solvents such as ethylene carbonate, increasing the internal resistance of the battery and deteriorating its cycle performance

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