Electrolyte solution and secondary battery

Abstract

The invention provides an electrolyte solution, comprising an organic solvent, lithium salt and an additive, wherein the additive comprises an additive 1 and an additive 2, the additive 1 is a compound having a nitrile group and a double bond structure, and its general formula is shown in description; and R1, R2, R3, R4, R5, R6 and R7 in the general formula are substituent groups such as hydrogen,alkyl group, phenyl group, alkenyl, fluorinated alkyl and halogen independently. The nitrile group can be subjected to complexation with the surface of a positive electrode, the olefin part can be subjected to polymerization reaction, and a cyclic structure can control the degree of polymerization, thereby controlling the density of the complexed nitrile group, forming a stable and well-proportioned SEI film, inhibiting side reactions of the electrolyte solution and the positive electrode material at a high temperature or high voltage, and improving cell gas production, storage and cycling performance.

Description

technical field [0001] The invention relates to the technical field of lithium-ion secondary batteries, in particular to an electrolyte and a secondary battery, and more specifically to an electrolyte applied to a lithium-ion secondary battery and the secondary battery. Background technique [0002] Lithium-ion batteries have the characteristics of long cycle life, high specific energy, short charging time, small size, and light weight. They are widely favored by people and have been widely used in electronic products. At present, with the continuous improvement of lithium-ion battery capacity requirements for electrical equipment, people's expectations for improving the energy density of lithium-ion batteries are getting higher and higher. For ternary cathode materials, increasing the nickel content or increasing the working voltage can effectively increase the energy density of the cell, but at the cost of intensifying the side reactions between the cathode material and th...

AI Technical Summary

Problems solved by technology

For ternary cathode materials, increasing the nickel content or increasing the working voltage can effectively increase the energy density of the cell, but at the cost of intensifying the side reactions between the cathode material and the electrolyte, and deteriorating the gas production, storage and cycle performance of the cell

Chinese patent CN102244296B lithium-ion battery and its electrolyte discloses an electrolyte, pointing out that adding saturated fatty nitrile compounds such as succinonitrile and adiponitrile in the electrolyte can improve the electrode / electrolyte interface and reduce the solvent loss in the electrolyte. Decomposition, thereby reducing the amount of gas produced in the battery, improving the high-temperature storage performance, safety performance and cycle performance of the battery; Chinese patent CN 105140562 A an electrolyte containing phthalonitrile and a lithium-ion battery using the electrolyte, pointing out that in electrolysis Add 0.01% to 5% phthalonitrile compound in the solution, the acetonitrile group (-C-CN) on the benzene ring can complex with the metal ion in the positive electrode active material, reduce the decomposition of the electrolyte, inhibit the dissolution of the metal ion, and protect The positive electrode improves the high-temperature performance of the battery. However, under high-temperature or high-voltage systems, the oxidation of the positive electrode is enhanced. After the conventional electrolyte, including the electrolyte in the above invention, is in contact with the positive electrode, it is easily oxidized and decomposed, thereby causing the battery to swell and saturate. The film-forming ability of the complexation between nitrile and the surface of the positive electrode is slightly insufficient, which cannot effectively reduce the gas production of the battery cell

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