The invention provides a bis(fluorosulfonyl)imide impurity removal and purification system and a bis(fluorosulfonyl)imide impurity removal and purification method. The system comprises a light-component stripping tank, a gas-liquid separator, a product buffer tank, an impurity removal reactor, and a film evaporator. The light-component stripping tank is connected to a reaction product liquid supply source. The gas-liquid separator is connected to the light-component stripping tank and also connected to the light-component product recovery device. The product buffer tank is connected to the light-component stripping tank and also connected to the gas-liquid separator. The impurity removal reactor is connected to the product buffer tank and also connected to an impurity removal reactant supply source. The film evaporator is connected to the impurity removal reactor, connected to a gas-phase separation system, and also connected to an impurity collection tank. The bis(fluorosulfonyl)imide impurity removal and purification system and the bis(fluorosulfonyl)imide impurity removal and purification method according to the invention make it possible to remove impurities from bis(fluorosulfonyl)imide continuously and efficiently and purify it.

The invention relates to a composition comprising a salt composed of a sodium cation and an anion of formula (II):

##STR00001## wherein R.sup.1 and R.sup.2 independently represent a fluorine atom or a perfluorinated group, the composition having a sulfamate ion content of from 0.1 to 3000 ppm by weight. The invention also relates to a process for preparing this composition and to an electrolyte comprising same.

The invention relates to a composition comprising a salt composed of a sodium cation and an anion of formula (II):

##STR00001## wherein R.sup.1 and R.sup.2 independently represent a fluorine atom or a perfluorinated group, the composition having an acetamide content of from 0.1 to 1000 ppm by weight. The invention also relates to a process for preparing this composition and to an electrolyte comprising same.

A method for preparing lithium bis(fluorosulfonyl)imide, includes reacting bis(fluorosulfonyl)imide with lithium carbonate in a mixed organic solvent to obtain lithium bis(fluorosulfonyl)imide after post-treatment. In the synthetic route of the lithium bis(fluorosulfonyl)imide, the reaction process stays at the stage of lithium bicarbonate, so there is little water in the reaction system, and it is very easy to recover the generated lithium bicarbonate. The process is simple and can be used to prepare lithium bis(fluorosulfonyl)imide of high quality at a high yield.

The present disclosure is provided with water removal and recovery system and method for lithium bis(fluorosulfonyl)imide. Specifically, the purification of lithium bis(fluorosulfonyl)imide crude products is achieved by two-stage thin film evaporators in series, thereby acquiring lithium bis(fluorosulfonyl)imide with sufficiently high purity with a relatively simple structure. The thin film evaporators themselves integrate the evaporation system and the condensation system, which not only simplifies the system configuration of connecting pipelines or tubs, but also lowers resistance and reduces the risk of system leakage. Furthermore, the solvents and water after evaporation can be effectively separated by a water separator, such that the content of organic phase solvents in the separated water is very low, and the content of water in the organic phase solvents is also very low. This allows for the maximum recovery of high-purity solvent for reuse, thereby facilitating the reduction of wastewater treatment costs.