Direct regeneration of waste LiFePO4 cathode materials with a solid-phase method promoted by activated CNTs

Annually increasing electric vehicles will undoubtedly end in tremendous amount of waste LiFePO4 (LFP) batteries. In this work, a highly-efficient and easy-going solid-phase method is proposed for direct regeneration of the waste LFP cathode material (W-LFP). The W-LFP is successfully regenerated via heat treatment with the addition of Li2CO3, CNTs and glucose. After activation, the dispersibility of CNTs in water is improved, making it easier to mix well with other materials. Also, the hydroxyl and carboxyl groups on CNTs have a certain degree of reducibility, which is conducive to the reduction of Fe3+ to Fe2+. After subsequent heat treatment, the three-dimensional conductive network composed of CNTs greatly enhances the conductivity and the ionic diffusion coefficient of LFP, thereby improving its electrochemical performance. Meanwhile, the decay and regeneration mechanisms of LFP are investigated by characterization and electrochemical testing. The regenerated LFP achieves an excellent specific capacity of 155.47 mAh/g at 0.05 C, which is around 99% that of new LFP. Additionally, the costs of main consumption in the regeneration process only account for 33.7% the price of new LFP. This low-cost, high-value-added and solid-phase direct regeneration process is proved to have great economic and energy-saving potential, which is promising for recycling the waste LFP cathode materials.