Synthesis of LiNiPO4 via citrate sol–gel route

In this paper, LiNiPO4 powders were prepared by sol gel method using citric acid as chelating agent. The article investigated the effect of annealing temperature and citric acid: Li molar ratio (cit/Li) on the structure and electrochemical properties of LiNiPO4 material. The results indicated that pure Pnma LiNiPO4 phase was synthesized at 700 and 800 °C. It was found that the increase of annealing temperature and cit/Li induced rod-to-sphere transition. The particles sizes increased with increasing annealing temperature, while the particles sizes were increasing firstly and then decreasing with increasing the ratio of cit/Li. Decreasing particles sizes had an advantage of both decreasing the charge transfer resistance (Rct) and improving the reversible capacity of pure olivine LiNiPO4 samples. Spherical particles (100–200 nm) prepared at 700 °C with cit/Li molar ratio of 2:1 were found to have low resistance, high electrochemical reversibility, cycle stability.