EC-free lithium ion battery electrolyte suitable for high nickel-silicon carbon system

Abstract

The invention discloses an EC-free lithium ion battery electrolyte suitable for a high nickel-silicon carbon system, and relates to the technical field of lithium-ion batteries. The electrolyte comprises an electrolyte lithium salt, a non-aqueous organic solvent and an additive, wherein the additive comprises a sulfur-nitrogen compound additive A with a structure shown in a formula 1 and a conventional film-forming additive, cyclic ester in the solvent system comprises propylene carbonate (PC) and fluoroethylene carbonate (FEC), and linear ester comprises at least one of dimethyl carbonate, diethyl carbonate (DEC) and ethyl methyl carbonate. According to the electrolyte disclosed by the invention, a synergistic effect generated by combined use of the additive A and the conventional additive is utilized; an electrolyte capable of effectively improving the performance of the high nickel-silicon carbon system lithium ion power battery is provided, and the electrolyte has good electrochemical properties such as cycle performance, rate capability and storage performance under high-temperature and low-temperature conditions, so that the problem of gas production of an existing high nickel-silicon carbon system under high voltage is solved.

Description

Technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to an electrolyte suitable for high nickel-silicon carbon system EC-free lithium ion batteries. Background technique [0002] As new energy vehicles demand high capacity and high endurance of lithium-ion batteries, higher requirements are put forward for the energy density and safety of lithium-ion power batteries. [0003] Contrast with Chinese patent CN201510952221.3, which is suitable for silicon carbon anode lithium ion battery electrolyte and silicon carbon anode lithium ion battery. The internal record says: the lithium ion battery electrolyte is composed of non-aqueous organic solvent, lithium salt and additives. Including fluoroethylene carbonate, tris(trimethylsilane) borate and the sulfate compound represented by structural formula (1) or (2). Compared with the prior art, the present invention adopts the combination of the above three additives Using the resulting ...

AI Technical Summary

Problems solved by technology

[0003] Compared with Chinese patent CN201510952221.3, an electrolyte suitable for silicon-carbon negative electrode lithium-ion batteries and silicon-carbon negative electrode lithium-ion batteries has internal records: wherein the lithium-ion battery electrolyte is composed of non-aqueous organic solvents, lithium salts and additives, additives Including fluoroethylene carbonate, tris(trimethylsilane) borate and sulfuric acid ester compounds shown in structural formula (1) or (2), compared with the prior art, the present invention through the combination of the above three additives Using the synergistic effect produced, the ability to change and control the composition and stability of SEI is achieved. The formed SEI film has an overall smaller impedance and the stability of its composition and structure, thereby greatly improving the reversible capacity and capacity of silicon-carbon negative lithium-ion batteries. The actual discharge capacity, so that the battery has good cycle performance and good high and low temperature performance, to ensure that the battery can be used in a wide range of ambient temperature, can not be better satisfied, can not solve the problem of graphite in PC and silicon carbon negative electrodes Component incompatibilities

[0004] Compared with Chinese patent CN201810629475.5, a silicon-carbon system lithium-ion battery electrolyte and a silicon-carbon system lithium-ion battery, it is internally recorded that: compounds including nitrile compounds, propylene sulfite and tetramethyldiamine compounds are used as electrolytic Liquid additives, these additives work together to make the electrolyte film form on the surface of the cathode, reduce the oxidation of the solvent, and improve the cycle performance of the high-voltage matching silicon-carbon negative electrode. Up to 4.5V, and the lithium ion conductivity of the electrolyte is high; the thickness expansion and internal resistance increase are small, the remaining capacity and recoverable capacity are high; high and low temperature discharges have higher capacity retention; and high safety, tested in a hot box No fire, no explosion, no good solution to the problem of battery flatulence

[0005] In order to meet the demand for high energy density of lithium-ion batteries, the high nickel-silicon carbon system is currently considered to be the most promising battery system. On the one hand, ethylene carbonate is unstable at high pressure; on the other hand, high-nickel materials usually undergo oxygen evolution at high potentials, which accelerates the oxidative decomposition of EC to produce gas, and eventually leads to a change in the stability of the battery interface. Poor, increased impedance and reduced battery performance

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