High Li-storage performances of LiMnxFe1-xPO4/C (x = 0, 0.05, 0.1 and 0.2) cathodes derived from spent Li foil, expired manganese gluconate and rust

The waste materials may result in the environment pollution and the rapid consumption of the non-renewable natural resources if they aren't reasonably recycled in time. LiMn x Fe 1-x PO 4 can combine the advantages of good rate capability of LiFePO 4 and high voltage of LiMnPO 4 , thus attracting more attentions. Herein, LiMn x Fe 1-x PO 4 /C (x = 0, 0.05, 0.1 and 0.2) powders are prepared from three wastes (spent Li foil, expired manganese gluconate and rust) by FePO 4 process. The results show that LiMn x Fe 1-x PO 4 /C (x = 0, 0.05, 0.1 and 0.2) powders appear as the irregular particles with 100–300 nm in size, and Mn 2+ partly substituted at Fe 2+ site. Especially, optimal 10 % Mn 2+ -doping improves the voltage plateau and energy density of LiFePO 4 /C. In detail, LiMn 0.1 Fe 0.9 PO 4 /C cathode delivers the specific discharge capacity of 159.3 mAh/g at 0.2C and 137.7 mAh/g at 1.0C, higher than those of LiFePO 4 /C cathode, LiMn 0.05 Fe 0.95 PO 4 /C cathode and LiMn 0.2 Fe 0.8 PO 4 /C cathode due to high diffusion coefficient (8.36 × 10 −14  cm 2 /s) and wider ionic diffusion channels of LiMn 0.1 Fe 0.9 PO 4 /C. The capacity retention rate of LiMn 0.1 Fe 0.9 PO 4 /C remains 91.0 % even after 500 cycles at 1.0C. Seemingly, optimal 10 % Mn 2+ -doping can indeed improve the reversible capacity and cyclic performance of LiFePO 4 cathode mainly due to lower charge transfer impedance and widen Li ion diffusion channel.