Aqueous synthesis of Li2MnAO4/C (A = Si, Ge) as positive electrode active materials for lithium-ion batteries by acid-base reaction

Polyanion-type positive electrode active materials such as LiFePO4 are promising materials for high-safety lithium-ion batteries because of their highly stable anion structure. However, polyanion-based positive electrode active materials with high energy densities and good safety features are more desirable than LiFePO4 at present. Among the polyanionic materials, Li(2)MAO(4) (M = Mn, Fe; A = Si, Ge) systems have high theoretical capacities owing to their two-electron redox in many cases, and these materials are synthesized using sol-gel or solid-phase methods. This study provides a more simple and environmentally friendly method for the aqueous synthesis of Li(2)MAO(4) via an acid-base reaction. The material could be simultaneously composited with carbonized carbon. Li2MnGexSi1-xO4/C (x = 0, 0.5, 1.0) and metal substituted Li2Mn0.8Fe0.2SiO4/C and Li2Mn0.8Fe0.2GeO4/C were successfully prepared, and showed discharge capacities of 195 mA h g(-1) and 178 mA h g(-1), respectively, at 0.13 mA cm(-2) and 25 degrees C. Thus, the developed method can be effectively used to fabricate polyanion-type positive electrode active materials.

Automated summary

Polyanion-type positive electrode active materials, such as LiFePO4, are considered promising for high-safety lithium-ion batteries due to their highly stable anion structure. However, there is a demand for polyanion-based positive electrode active materials with high energy densities and good safety features. In this study, a simple and environmentally friendly method for the aqueous synthesis of Li(2)MAO(4) via an acid-base reaction is proposed. The results show that the method can effectively fabricate polyanion-type positive electrode active materials.