Preparation method for difluorosulfimide lithium salt

The invention relates to the field of lithium batteries and lithium capacitors, in particular to a preparation method for difluorosulfimide lithium salt and application of the difluorosulfimide lithium salt. The preparation method for the difluorosulfimide lithium salt, provided by the invention, comprises the following steps: (1) performing fluorination reaction: synthetizing midbody difluorosulfimide from dichlorosulfimide and hydrogen fluoride under the action of a catalyst; (2) performing reaction between the difluorosulfimide obtained in the step 1 and alkaline lithium, and performing solid-liquid separation after the reaction to obtain an LiFSI product. The preparation method for the difluorosulfimide lithium salt, provided by the invention, is low in cost, few in by-product and simple in post-treatment, and the quality and the purity of the product are ensured, therefore the preparation method which is capable of obtaining the high-quality and high-purity product and is economic and practical is provided; the preparation method is suitable for industrial production.