A lithium ion battery electrolyte and a lithium ion battery containing the electrolyte

Abstract

The invention discloses a lithium-ion battery electrolyte, which comprises a non-aqueous organic solvent, a lithium salt and additives. The additives include a negative electrode film-forming additive, a positive electrode protection additive and compound A with a specific structure. The invention also discloses a lithium ion battery containing the lithium ion battery electrolyte. The present invention can satisfy the long cycle life of lithium-ion batteries by optimizing the electrolyte formula of lithium-ion batteries, especially under the synergistic effect of a unique combination of mixed lithium salts, negative electrode film-forming additives, positive electrode protection additives and compound A with a specific structure Requirements, while improving the storage performance of the battery, thereby improving the electrochemical performance of the lithium-ion battery.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery electrolyte and a lithium ion battery containing the electrolyte. Background technique [0002] High energy density ternary lithium-ion battery is the main development and application direction of power battery and energy storage products. At present, one aspect of improving energy density is to increase the proportion of nickel in the positive electrode material or to increase the working upper limit voltage of the positive electrode material. The increase of nickel content or the increase of working voltage will cause the thermal instability and surface activity of the positive electrode material to increase, and the surface of the positive electrode material will continue to react with the organic components in the electrolyte when the surface of the positive electrode material is exposed to the electrolyte, resulting in an increa...

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Problems solved by technology

[0003] At present, commercial products for high-nickel and high-voltage NCM ternary power battery electrolytes are still immature, and the main problems lie in the following aspects: (1) A particle interface may appear in the high-voltage system due to transitional delithiation or agglomerated single crystal in the later stage Powdered or agglomerated single crystals are separated, the internal resistance becomes larger, the battery capacity decays quickly, and high-temperature cycles are also prone to diving; (2) Metal oxides in a high oxidation state have strong oxidizing properties and can catalyze organic solvents and the decomposition of additives, resulting in the thickening of the positive CEI film and the increase of impedance, resulting in capacity attenuation; (3) the positive electrode material is prone to cracks during charge and discharge, and forms highly active oxygen with the release of lattice oxygen, It is easy to cause the battery to produce gas during use or storage, which shortens the service life of the battery and is accompanied by battery safety issues; (4) The high-nickel high-voltage positive electrode material is extremely strict in the production process of the battery and is sensitive to moisture (5) After the dissolution of transition metal nickel and manganese ions in the positive electrode material, on the one hand, it has the effect of catalytically decomposing the electrolyte, accelerating the consumption of the electrolyte, and on the other hand, it is easy to enter the negative electrode with the migration of charges to destroy the SEI film Cause the failure of the negative electrode; (6) The decomposition of lithium hexafluorophosphate in the battery system and the unstable components in the electrolyte in the high temperature environment is easy to produce HF, POF 3 and PF 5 , accelerating the damage to the electrolyte and interfacial film and causing battery failure

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