Improvement of the electrochemical performance by partial chemical substitution into the lithium site of titanium phosphate-based electrode materials for lithium-ion batteries: LiNi0.25Ti1.5 Fe0.5(PO4)3

Partial lithium substitution with nickel (0.25 of Ni2+ ion) in the previously reported Li1.5Fe0.5Ti1.5(PO4)3/C (LFTP@C) was performed to improve its structural and electrochemical properties. The new LiNi0.25Fe0.5Ti1.5(PO4)3/C (LNFTP@C) material was then tested as electrode for lithium ion batteries. In the voltage window 1.85V–3.0 V vs. Li+/Li, attractive electrochemical performances were obtained, mostly in terms of rate capability performance. At a current rate of 0.1C (6.6 mAg−1), the material delivered a capacity of around 120 mAhg−1, while at 5C, we observed a slight drop of the specific capacity reaching a value of 108 mAhg−1. Long-term cycling performance stability was also tested demonstrating a remarkable capacity decrease during the last 500 cycles. The capacity retention decreased from 94% to 91% after 500 cycles to about 77% and 74% after 1000 cycles at fast current rates of 5C (329.8 mAg−1) and 10C (659.6 mAg−1), respectively. In the wider voltage window, an average specific capacity of around 380 mAhg−1 was attained at a slow current rate of 0.1C.