A New Class of Ternary Compound for Lithium-Ion Battery: from Composite to Solid Solution

Searching for high-performance cathode materials is a crucial task to develop advanced lithium-ion batteries (LIBs) with high-energy densities for electrical vehicles (EVs). As a promising lithium-rich material, Li2MnO3 delivers high capacity over 200 mAh g–1 but suffers from poor structural stability and electronic conductivity. Replacing Mn4+ ions by relatively larger Sn4+ ions is regarded as a possible strategy to improve structural stability and thus cycling performance of Li2MnO3 material. However, large difference in ionic radii of Mn4+ and Sn4+ ions leads to phase separation of Li2MnO3 and Li2SnO3 during high-temperature synthesis. To prepare solid-solution phase of Li2MnO3–Li2SnO3, a buffer agent of Ru4+, whose ionic radius is in between that of Mn4+ and Sn4+ ions, is introduced to assist the formation of a single solid-solution phase. The results show that the Li2RuO3–Li2MnO3–Li2SnO3 ternary system evolves from mixed composite phases into a single solid-solution phase with increasing Ru content. ...