On the Ni0.75Ti1.5Fe0.5(PO4)3/C NASICON-type electrode material

The effect of titanium chemical substitution with iron, coupled with introducing additional Ni2+ ions in the M1 site, on the electrochemical and structural properties of the previously studied Ni0.5Ti2(PO4)3 (NTP@C) material is investigated in this manuscript. The new Ni0.75Fe0.5Ti1.5(PO4)3/C (NFTP@C) composition is prepared via the conventional sol-gel method and tested as new electrode material for lithium-ion batteries. In the voltage range of 1.85?3.0 V, the NFTP@C electrode delivered a first discharge capacity around 118 mAh.g?1 at a slow current rate of 0.1C (6.25 mA g?1). unlike the NTP@C, when the new NFTP@C electrode is cycled at faster current rates such as 5C (312.56 mA g?1), the capacity dropped to about 65 mAh.g?1 which represents only 55% of the capacity obtained at 0.1C (6.25 mA g?1) but with a columbic efficiency of more than 99%. When long-term cycling performance stability was investigated, a remarkable stability was achieved revealing the positive influence of iron together with the extra Ni2+ ions in the M1 site, preserving the structural stability during the intercalation process of Li+ ions. A capacity retention of about 95% was obtained after 500 cycles at the current rate of 0.5C (31.26 mA g?1). When NFTP@C was cycled in the voltage window 0.5?3.0 V, an average specific capacity of around 350 mAh.g?1 was achieved at the current rate of 0.1C resulted out of the decomposed NASICON structure.

Automated summary

The new NFTP@C electrode showed good initial discharge capacity and high coulombic efficiency, but the capacity dropped at faster current rates. In long-term cycling tests, iron and additional Ni2+ ions helped maintain structural stability and improve capacity retention.