Liquid electrolyte formulation for lithium metal secondary battery and lithium metal secondary battery comprising said liquid electrolyte formulation

A process for preparing a liquid electrolyte formulation for a lithium metal secondary battery comprising:

• a conductive lithium salt which is selected from the group consisting of LiTFSI, LiFSI, LiCl, LiF, LiCN, LiC2N3, LiN3, LiNO2, LiNO3, LiBF4, LiPF6, LiAsF6, LiSbF6, and LiAlCl4,
• a first ionic liquid having the formula (CATION)FSI, wherein CATION is selected from the group consisting of alkyl pyrollidinium and alkyl piperidinium,
• a second ionic liquid as anti-corrosion agent, said second ionic liquid having the formula (CATION)(ANION) where (CATION) is defined as above and (ANION) is an anion comprising at least one nitrile functionality,
• wherein said process comprises the steps of:
• a) dissolving the conductive lithium salt in the first ionic liquid to obtain a mixture
• b) heating the mixture of step a) at a temperature comprised between 50° C. and 130° C.
• c) optionally adding the stabilizer
• d) adding to the mixture of step b) or step c) the second ionic liquid while maintaining a temperature comprised between 50° C. and 130° C.
• e) stirring the mixture of step d) while maintaining a temperature comprised between 50° C. and 130° C. until the mixture is completely free of suspended matter
• f) cooling the mixture of step e) to room temperature.