ELECTROCHEMICAL CHARACTERISTICS OF LiFePO4, RECOVERED AFTER BATTERY DEGRADATION

Abstract

Due to the ability of LiFePO4 (LFP) to be charged with large currents, LFP batteries are widely used in household appliances and elect­ric vehicles, so the recycling of spent LFP batteries becomes an urgent need. First, they contain toxic components of electrolyte that cannot be buried in landfills; secondly, the cost of lithium which contains in the electrode material continuously increases, and therefore its return to circulation is profitable and expe­dient. To achieve this goal, much attention is paid to hydrometallurgical processing based on the chemical extraction of Li2CO3 and FePO4 during the regeneration of the electrode material. Here we report on the wet chemistry recycling of used LFP batteries. The main task of the work was to simplify the LiFePO4 regene­ration process by leaching with a solution of citric acid due to the elimination of the stage of isolation of Li2CO3 and FePO4, i.e. without selective separation of the filtrate components. The source of spent LiFePO4 was an industrial lithium iron phosphate battery failed due to an internal short circuit. It was found that using citric acid in the ratio H3Cit:LiFePO4=0.5:1, it is possible to efficiently and quickly separate the electrode material from the aluminum current collector. Further pyrolysis and heat treatment of the citrate solution makes it possible to obtain a high-purity LiFePO4/C composite material without extraneous impurities, except for amorphous carbon, which is formed during the pyrolysis of iron (II) and lithium citrates and the thermal decomposition of the binding material in an inert atmosphere. The specific capacity of the LiFePO4/C composite material recovered by the proposed method (145 mA∙h/g) insignificantly differs from that of commercial analogues. This, in our opinion, indicates good prospects of the lithium-iron phosphate regeneration method proposed in this paper.