Preparation method for lithium bis(fluorosulfonyl)imide including multiple ammonia source additions, electrolytic solution and secondary battery

A method for preparing lithium bis(fluorosulfonyl)imide, comprising

• (1) adding an organic solvent and an absorbent A to a reaction kettle, then adding part of an ammonia source, and finally adding SO2X2 and a remaining ammonia source simultaneously for reaction, to obtain a solution of a salt (SO2F—NH—SO2F)·A containing bis(fluorosulfonyl)imide and the absorbent A, wherein in the SO2X2, X is independently fluorine or chlorine;
• (2) performing filtration, concentration and washing on the solution obtained in step (1) to obtain a purified salt (SO2F—NH—SO2F)·A of the bis(fluorosulfonyl)imide and the absorbent A;
• (3) adding a lithium source to the purified salt (SO2F—NH—SO2F)·A of the bis(fluorosulfonyl)imide and the absorbent A obtained in step (2) for reaction to obtain a solution containing lithium bis(fluorosulfonyl)imide;
• and
• (4) performing dehydration, concentration, crystallization with a non-aqueous poor solvent, and drying on the solution obtained in step (3) to obtain the lithium bis(fluorosulfonyl)imide, wherein in step (1), a mass of the part of the ammonia source accounts for 3%-10% of a total mass of the ammonia source.