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

Abstract

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. LiMnxFe1-xPO4 can combine the advantages of good rate capability of LiFePO4 and high voltage of LiMnPO4, thus attracting more attentions. Herein, LiMnxFe1-xPO4/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 FePO4 process. The results show that LiMnxFe1-xPO4/C (x = 0, 0.05, 0.1 and 0.2) powders appear as the irregular particles with 100–300 nm in size, and Mn2+ partly substituted at Fe2+ site. Especially, optimal 10 % Mn2+-doping improves the voltage plateau and energy density of LiFePO4/C. In detail, LiMn0.1Fe0.9PO4/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 LiFePO4/C cathode, LiMn0.05Fe0.95PO4/C cathode and LiMn0.2Fe0.8PO4/C cathode due to high diffusion coefficient (8.36 × 10−14 cm2/s) and wider ionic diffusion channels of LiMn0.1Fe0.9PO4/C. The capacity retention rate of LiMn0.1Fe0.9PO4/C remains 91.0 % even after 500 cycles at 1.0C. Seemingly, optimal 10 % Mn2+-doping can indeed improve the reversible capacity and cyclic performance of LiFePO4 cathode mainly due to lower charge transfer impedance and widen Li ion diffusion channel.