Hydrothermal synthesis of cathode materials

A number of cathodes are being considered for the next generation of lithium ion batteries to replace the expensive LiCoO₂ presently used. Besides the layered oxides, such as LiNi_yMn_yCo_1-2yO₂, a leading candidate is lithium iron phosphate with the olivine structure. Although this material is inherently low cost, a manufacturing process that produces electrochemically active LiFePO₄ at a low cost is also required. Hydrothermal reactions are one such possibility. A number of pure phosphates have been prepared using this technique, including LiFePO₄, LiMnPO₄ and LiCoPO₄; this method has also successfully produced mixed metal phosphates, such as LiFe_0.33Mn_0.33Co_0.33PO₄. Ascorbic acid was found to be better than hydrazine or sugar at preventing the formation of ferric ions in aqueous media. When conductive carbons are added to the reaction medium excellent electrochemical behavior is observed.