Transition metal sulfide and phosphide for high performance lithium and sodium storage

The ever-growing demand for electrical energy storage (EES) devices is creating great opportunities. Especially for the rechargeable ion batteries, great success has been achieved during the last two decades. Since the 1990s, the lithium ion batteries (LIBs) have been commercialized and come to dominate the market owing to their high safety, stability, and capability of storing and converting clean energy to provide a constant power supply. For them to acquire high energy density and improved cycling performance, however, modification and new designs for electrode materials are still a task for researchers. In the meanwhile, due to limited lithium resources, it is desirable to find an alternative for next generation EES devices. Sodium ion batteries (SIBs) have emerged as one of the most promising candidates because sodium containing compounds are abundant and have cheap raw materials. Compared to the Li-ion battery system, sodium possesses a larger ionic radius (1.06 Å for Na+ versus 0.76 Å for Li+) and about 300 mV higher reduction potential than lithium. In lithium containing compounds, lithium can exist in octahedral or tetrahedral coordination. Sodium rarely has the tetrahedral coordination but prefers octahedral and prismatic coordination...