Phase Transition Induced Synthesis of Layered/Spinel Heterostructure with Enhanced Electrochemical Properties

A one-step synthesis of Li-rich layered materials with layered/spinel heterostructure has been systematically investigated. The composites are synthesized by a polyol method followed with an annealing process at 500–900 °C for 12 h. A spinel to layer phase transition is considered to take place during the heat treatment, and the samples obtained at different temperatures show diverse phase compositions. An “Li-rich spinel phase decomposition” phase transition mechanism is proposed to explain the formation of such a heterostructure. The electrochemical properties of the heterostructure are found to be associated with the ratio of spinel to layer phases, the leach out of rock salt phase, and the change of crystallinity and particle size. Product with improved cyclic and rate performance is achieved by annealing at 700 °C for 12 h, with a discharge capacity of 214 mA h g−1 remaining at 0.2 C after 60 cycles and discharge capacity of about 200 mA h g−1 at 1 C.