Tailored synthesis of molybdenum-selenide/selenium/sodium-molybdate hybrid composites as a promising anode for lithium-ion and sodium-ion batteries

Novel molybdenum-selenide/selenium/sodium-molybdate hybrid composites, denoted MoxSey@Na2MoO4, are synthesized and demonstrated superior electrochemical properties for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). For instance, MoxSey@Na2MoO4-1 h delivers a reversible capacity of 1228 mAh g−1 in LIBs, 400 mAh g−1 in SIBs after 150 cycles. This outstanding electrochemical performance is attributed to the hybrid composite’s unique structures that are characterized by the presence of sheet structures as well as amorphous phase and heterostructures. The sheet structures and amorphous phases are beneficial to mitigate volume expansion and enhance reaction kinetics, while the heterostructures possess several components serving as spacers between the sheets. These microstructural features lead to prevent the collapse of sheet structures during cycling, and to improve the accessibility of electrolytes as well as to enhance Li+/Na+-ion storage abilities between the sheets. This synergistic effect promotes stabilizing the structure of the active materials and accelerating the kinetics of the reactions, resulting in excellent electrochemical properties for both Li-ion and Na-ion storage. Furthermore, the significant electrochemical behavioral differences between Li+ and Na+-ions in MoxSey@Na2MoO4 materials are studied and understood by investigating Li+/Na+-ion diffusion phenomena in this work. The results indicate that MoxSey@Na2MoO4 materials have great potential as anodes for both LIBs and SIBs.