Preparation and electrochemical performances of submicro-TiP2O7 cathode for lithium ion batteries

The TiP2O7 with a cubic 3 x 3 x 3 superstructure was synthesized by a liquid-assisted solid-state reaction, and characterized by x-ray diffraction, scanning electron microscopy, cyclic voltammogram, galvanostatic charge/discharge testing, and electrochemical impedance spectroscopy (EIS) technique. The results showed that there was only one step of intercalation into TiP2O7, corresponding to a pair redox (E (Li/Li) (+) = 2.74/2.48 V). The initial discharge capacity of TiP2O7 was 110 mAh/g at a current density of 15 mA/g, and the capacity retention was 76.12 % of the initial discharge capacity after 100 cycles. The EIS of TiP2O7 electrode consisted of two semicircles in organic electrolyte, which was attributed to SEI resistance as well as the contact resistance, and charge transfer process, respectively. A suitable model was proposed to explain the impedance response of the insertion TiP2O7 material of lithium ion batteries.