A method of forming a polyanion active material that includes providing a carbon source, providing a mobile ion source, providing an active metal material, providing a network material, providing a flux material, and mixing the various materials. In one aspect, the mixing step may include grinding or pulverizing materials to a uniform fine mixture. In one aspect, a ball mill may be utilized to mix the components. Following the mixing of the materials, the mixture is heated to a predetermined temperature in a non-oxidizing atmosphere to form a reaction product. In one aspect, the mixture is heated to a temperature above a melting temperature of the flux material. In this manner, the flux material provides a medium in which the various reactants may react to form the desired reaction product. Following the heating of the mixture the reaction product is washed, forming a carbon coated polyanion active material. Also disclosed is a polyanion active material that includes the in situ reaction product of a carbon source, mobile ion source, active metal material, network material, and a flux material wherein the polyanion active material includes a carbon coating formed thereon.