A sol-gel method in which alginate was used to help prepare carbon-coated LiNiPO4 nanocrystal aggregates with controllable surface area is reported. Nickel alginate prepared from NiCl2 and sodium alginate was blended with stoichiometric LiOH and H3PO4 to produce a single-source precursor gel. Calcining the gel in air at 400-800 degrees C produced LiNiPO4 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 degrees C was the optimal calcination temperature that gave LiNiPO4 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 LiMPO4 (M = Fe, Co, Mn).