Preparation method of high-purity lithium salt by mixing in a predetermined ratio and its application

摘要

PROBLEM TO BE SOLVED: To provide a method for producing a high purity lithium salt and a lithium ion battery containing the lithium salt. SOLUTION: A step of purifying industrial lithium oxalate and a step of reacting lithium oxalate with boron trifluoride/ethyl ether to obtain a mixed reaction solution of lithium difluoro(oxalato)borate and lithium tetrafluoroborate are obtained. Then, a step of a synthetic reaction of purifying with a purification auxiliary filtration membrane, a step of concentrating and crystallizing the reaction solution, and a step of purifying and drying the mixed lithium salt are included. The high-purity lithium salt of the present invention is a mixed lithium salt containing lithium difluoro(oxalato)borate and lithium tetrafluoroborate at a predetermined molar ratio of 1:1 and can be applied to a non-aqueous electrolytic solution for a lithium ion battery. [Selection diagram] Figure 1