Improving the interfacial stability, conductivity, and electrochemical performance of Li2MoO3@g-C3N4 composite as a promising cathode for lithium-ion battery

Abstract

Li-rich layered Li2MoO3 (LMO) materials are one promising cathode materials for Li-ion batteries due to their high theoretical capacity and without oxygen evolution. However, the poor electrical conductivity and air instability have limited its application as a cathode material for lithium-ion battery. To solve these problems, Li2MoO3/g-C3N4 composites were successfully constructed by combining the molten salt and ball milling methods. Carbon nitride (g-C3N4) with an abundant nitrogen-containing carbon framework contains a large number of “hole” defects and double-bonded nitrogen vacancy edges, which are favorable for the adsorption and diffusion of Li ions. In addition, density functional theory (DFT) calculations revealed that a stable interface can be formed between g-C3N4 and LMO, which also leads to the improvement of the electronic conductivity and the reduction of interfacial impedance of the composite. Therefore, the electrochemical performance of the composite material is significantly improved. The discharge capacity of GLMO-5 at a current density of 1700 mA g−1 is 64.6 mAh/g, which is much greater than the value (29.9 mAh/g) of the original LMO sample under the same conditions. EIS further shows that GLMO-5 has the highest discharge capacity with a DLi+ value of 1.94 × 10−14 cm2 s−1. These results indicate that constructing LMO-based composites with a highly stable layered material containing unsaturated functional groups should be an effective strategy to enhance the interfacial stability, electronic conductivity, and thus the electrochemical performances of the cathode materials.