according to the invention are used as electrolytes or electrolyte constituents in galvanic elements for example lithium ion batteries the following examples are intended to illustrate the invention without restricting its scope a membrane filtered fluoropolymer dss alfa laval pore size 0 15 u03bcm libob solution is used for all experiments the libob being produced as described in de c 19839030 production of solvate free libob crystallisate evaporative crystallisation crystallisate separation at approx 100 u00b0 c 5064 g of a 17 solution of libob in propylene carbonate pc having a water content of 230 ppm were evaporated at approx 8 to 10 mbar and approx 120 u00b0 c after distilling off approx 0 8 kg of pc the vacuum was broken for a short time and 1 g of libob crystallisate according to the invention was added during the course of the further vacuum distillation process the libob solution became turbid 2 34 kg of pc were distilled off in total the vacuum was broken and the suspension formed was cooled to 110 u00b0 c whilst stirring then the suspension was discharged onto a heatable sintered glass filter and filtered the filtration time was around 3 minutes the crystallisate was washed three times with 100 ml of preheated toluene each time and vacuum dried at a temperature of 80 to 90 u00b0 c yield 382.