Constructing melamine coating convertible into solid electrolytes to enhance the electrochemical performance of Li2ZnTi3O8 anode

Abstract

Melamine (MA) has some desirable functional groups convertible into solid electrolytes with enhanced ionic conductivity. Herein, a simple hydrothermal method is adopted to modify Li2ZnTi3O8 (LZTO) with MA for optimizing the electrochemical behaviors. After the hydrothermal treatment at 200 °C for 12 h, the modified products demonstrate alleviated polarization, high capacity, and excellent cyclability. At a mass ratio of 1:0.05 for LZTO to melamine, the product reveals superior Li-ion diffusion, low impedance, and optimal rate performance (delivering capacities of 202.4, 196.3, 182.3, 174.4, and 165.3 mAh/g at 0.1, 0.2, 0.4, 0.8, and 1.6 A/g, respectively). Combined the performance with structure and composition, the MA coating gradually evolves into solid electrolytes of Li3N and LiNxOy with high ionic conductivity in the initial lithiation process; meanwhile, the oxygen vacancies introduced in LZTO accompanied with the occurrence of LiNxOy facilitate electron and ion conductance, thus responsible for the promoted electrochemical performance of LZTO. More importantly, by virtue of the enhanced cyclability of the MA-modified LZTO, the reaction mechanism of LZTO during long-term cycling is made clear.