Synthesis and characterization of alginate-based sol-gel synthesis of lithium nickel phosphate with surface area control

Abstract

A sol-gel method in which alginate was used to help prepare carbon-coated LiNiPO 4 nanocrystal aggregates with controllable surface area is reported. Nickel alginate prepared from NiCl 2 and sodium alginate was blended with stoichiometric LiOH and H 3 PO 4 to produce a single-source precursor gel. Calcining the gel in air at 400-800 °C produced LiNiPO 4 nanocrystal aggregates with different levels of crystallinity, sizes, and surface areas. Powder X-ray diffraction, field-emission scanning electron microscopy, high-resolution transmission electron microscopy, and Brunauer-Emmett-Teller analyses collectively showed that 600 °C was the optimal calcination temperature that gave LiNiPO 4 with an average crystallite size of 43 nm, a surface carbon coating of 2-4 nm, and a surface area of 27.47 m 2 /g. The method allows simultaneous achievement of four features, namely, surface carbon coating, high crystallinity, control of primary particle size, and high surface area. Simple modification of the method would allow the production of a wider range of LiMPO 4 (M = Fe, Co, Mn).