Synthesis of Li excess LiFePO₄/C using iron chloride extracted from steel scrap pickling

Olivine-type Li rich Li_1+xFePO₄/C composites are synthesized by a solid state reaction process using premilled Li ₂CO₃ and pre-synthesized amorphous FePO ₄·xH₂O powders. The amorphous FePO ₄·xH₂O powders are prepared from an industrial waste liquid (by-product), a FeCl₃ (38%) solution, via a precipitation process. In addition, lithium carbonate is pre-milled using a high energy nano mill to control particle sizes and shape differences for enhancing the reaction activity in the starting materials. The main purpose of this study is to investigate the effect of excess Li on the electrochemical properties of LiFePO₄ cathode materials. The pre-synthesized FePO₄ powders are mixed with pre-milled lithium carbonate and glucose (8 wt%) using a ball-mill process. The structural characteristics of the Li _1+xFePO₄/C composites are examined by XRD and SEM. To investigate the effect of excess Li content on the electrochemical properties in Li_1+xFePO₄/C composites, a Li[LiPF₆ (Ethylene carbonate + Dimethyl carbonate)] Li_1+xFePO₄/C model cell is used. It is demonstrated that the 1% Li rich Li/[Li_1.01FePO ₄/C] cell exhibits the best electrochemical performance and delivers an initial discharge capacity of 161 mAhg^-1, which is 25 mAhg ^-1 higher than that of the Li/[LiFePO₄/C] cell.