Characterization of Nasicon-type Li3Fe2−2xTixMnx(PO4)3/C cathode materials

Nasicon-type Li3Fe2−2xTixMnx(PO4)3 (x = 0–0.2) cathodes were synthesized by a solid-state reaction route. The prepared powders were mixed with acetylene carbon using planetary milling to optimize the electrochemical performance. The galvanostatic charge/discharge test and the cyclic voltammetry (CV) indicated that both Li3Fe2(PO4)3/C and Li3Fe1.8Ti0.1Mn0.1(PO4)3/C cathodes showed two reversible redox phenomena at 2.8 and 2.7 V for Fe3+/Fe2+ couple versus Li/Li+ upon discharge. The plateau potential of Ti4+/Ti3+ versus Li/Li+ at 2.5 V is not observed because of the low content of Ti and the disturbance of Fe3+/Fe2+. In contrast, the plateau potential of Mn3+/Mn2+ versus Li/Li+ at 3.5 V is observed. In addition, the Li3Fe1.8Ti0.1Mn0.1(PO4)3/C cathode possessed higher reversibility and better capacity retention (122.3 mAh g−1 at C/20 in the first cycle, approaching the theoretical capacity of 128 mAh g−1, and close to 90.8 mAh g−1 at C/2 in the 20th cycle) than that of Li3Fe2(PO4)3/C cathode.