Electrochemical properties of TiP2O7 and LiTi2(PO4)3 as anode material for lithium ion battery with aqueous solution electrolyte

Some polyanionic compounds, e.g. TiP2O7 and LiTi2(PO4)3 with 3D framework structure were proposed to be used as anodes of lithium ion battery with aqueous electrolyte. The cyclic voltammetry properties TiP2O7 and LiTi2(PO4)3 suggested that Li-ion de/intercalation reaction can occur without serious hydrogen evolution in 5 M LiNO3 aqueous solution. The TiP2O7 and LiTi2(PO4)3 give capacities of about 80 mAh/g between potentials of −0.50 V and 0 V (versus SHE) and 90 mAh/g between −0.65 V and −0.10 V (versus SHE), respectively. A test cell consisting of TiP2O7/5 M LiNO3/LiMn2O4 delivers approximately 42 mAh/g (weight of cathode and anode) at average voltage of 1.40 V, and LiTi2(PO4)3/5 M LiNO3/LiMn2O4 delivers approximately 45 mAh/g at average voltage of 1.50 V. Both as-assembled cells suffered from short cycle life. The capacity fading may be related to deterioration of anode material.