Method for efficiently removing fluorine from spent lithium battery

Disclosed is a method for efficiently removing fluorine from a spent lithium battery. The method comprises: mixing aluminum and a sodium hydroxide solution for reaction to obtain a sodium metaaluminate solution; introducing sulfuric acid into the sodium metaaluminate solution, and stirring to react at a certain temperature to obtain a fluorine removal agent; adding a sodium fluoroaluminate seed crystal and the fluorine removal agent into an impurity-removed battery powder leaching solution, introducing a sodium carbonate solution at the same time, performing reaction at a certain temperature, controlling the pH value of a reaction endpoint, and performing solid-liquid separation after the reaction is finished to obtain a fluorine-removed liquid and filter residues; and adding the sodium hydroxide solution into the filter residues for reaction, and performing solid-liquid separation to obtain a filtrate containing fluorine and aluminum, and insoluble residues. According to the present invention, fluorine removal is induced by adding the sodium fluoroaluminate seed crystal; and during fluorine removal, the seed crystal sodium fluoroaluminate is firstly added into the battery leaching solution, and by means of induction of the seed crystal, combination of fluorine and aluminum in the solution can be accelerated to generate sodium hexafluoroaluminate, the reaction time is shortened, the fluorine removal efficiency is improved, and fluorine in the solution can be removed to be lower than 20 mg/L, thereby achieving the purpose of deep fluorine removal.