Guanidinium type ionic liquid electrolyzing solution for lithium secondary cell

Abstract

The invention discloses guanidinium salt ionic liquid electrolyte for a lithium secondary battery. The guanidinium salt ionic liquid electrolyte consists of guanidnium salt ionic liquid, lithium salts and an organic electrode solvent. The guanidinium salt ionic liquid electrolyte for the lithium secondary battery has the advantages of small viscosity, satisfactory electrochemical stability, excellent charge-discharge performance (in particular under big multiplying power), high coulomb efficiency, etc. As the melting point of the electrolyte is low, the invention can be used at low temperatures; as the steam pressure is extremely low, the invention does not volatilize after being heated so as to avoid the expansion and explosion of electromagnetic devices; and as the electrolyte is not easy to be combusted, the safety and stability of the invention is high. The granidinium salt ionic liquid electrolyte is composed of N,N,N',N'-tetramethyl-N'', N''-diethyl granidinium salt ionic liquid, lithium di(trifluoromethyl sulfuryl) imide with the molarity of 0.4mol / L and vinylene carbonate (the weight ratio of the vinylene carbonate and a ionic liquid is 1 to 20); in the button cell with LiCoO electrode as a positive electrode, when the charging and discharging multiplying power is 0.5C, the initial capacity of the battery is 128Ah / mg and after fifty times of cycles of charging and discharging processes, and the capacity is 118Ah / g so the conservation rate of the capacity is 92.2 percent.

Description

technical field [0001] The invention relates to an electrolytic solution for batteries, in particular to a guanidinium salt ionic liquid electrolytic solution for lithium secondary batteries. Background technique [0002] Lithium secondary batteries have been widely used due to their excellent battery performance such as high voltage, large specific energy, and long cycle life. With the continuous expansion of the application field of lithium secondary batteries, its safety hazards are becoming increasingly prominent. As an important part of the battery, the properties of the electrolyte directly affect the working current, voltage, service life and safety of the battery. [0003] At present, commercial lithium secondary batteries all use a mixed electrolyte composed of organic solvents and salts. Under high temperature conditions, organic solvents are easily vaporized so that their safety cannot be guaranteed. Simply using a high-boiling-point solvent will not fundamenta...

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Problems solved by technology

Patent US20030211389 proposes a mixture of guanidinium salt-containing ionic liquid and lithium salt as an electrolyte to be applied to various electrochemical devices, including lithium secondary batteries, but only composed of guanidine salt ionic liquid and lithium salt. The liquid will continue to decompose during the charging and discharging process of the lithium secondary battery at a high rate (0.5C and above), resulting in a relatively fast decay in the capacity of the battery and a short life (such as figure 2 shown)

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