Structural changes upon lithium insertion in Ni _0.5TiOPO ₄

Nickel titanium oxyphosphate Ni _0.5TiOPO ₄ (NTP), was prepared by co-precipitation route. Its structure was determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic system, S.G: P2 ₁/c [a = 7.333(1), b = 7.316(2), c = 7.339(2), β = 119.62(3)°, Z = 4, R ₁ = 0.0142, wR ₂ = 0.0429]. The structure might be described as a {TiOPO ₄} framework made of corner-sharing [TiO ₆] octahedra chains running parallel to [0 0 1] and cross linked by phosphate [PO ₄] tetrahedral, where half of octahedral cavities created are occupied by Ni atoms, and the other half of octahedral sites are vacant. During the first discharge, the NTP electrode delivered a capacity of 530 mAh/g, upon cycling within 0.5-4 V. To understand the electrochemical reaction mechanism using different characterization techniques viz. in situ synchrotron diffraction. Reciprocal magnetic susceptibility (χ ^-1) of NTP, between 4 and 300 K, shows an almost linear behavior and can be fitted by the simple Curie-Weiss law.