Multi-cations doped LiVPO₄ F cathode for lithium-ion batteries

The multi-cations doped LiVPO₄F, nominally Li_0.97Cr_0.01V_0.95Al_0.01Nb_0.02PO₄F_0.97, is prepared by Chromium (Cr) doping on lithium site and Al-Nb co-doping on vanadium site via a conventional carbothermal reduction (CTR) route. The crystallographic lattice volume, particle size and morphology are not obviously changed comparing with un-doped LiVPO₄F. However, the high rate and lifetime cycling performances are noticeably improved although the capacities at very low currents are slightly decreased. The reversible capacity at 1/10 C, 1 C, 2 C and 4 C of the pristine LiVPO₄F is 143 mA h g^-1, 99 mA h g^-1, 86 mA h g^-1 and 70 mA h g^-1, respectively, while that of the doped counterpart is 138 mA h g^-1, 102 mA h g^-1, 95 mA h g^-1 and 82 mA h g^-1, respectively. The capacity retention after 100 galvanostatic cycles at 1.5 C is enhanced from 85.4% to 90.9% by such multi-cations doping. Moreover, the initial coulombic efficiency is significantly increased from 81.8% to 90.3% as well.