Metal Phosphide as Advanced Anode Materials for Rechargeable Sodium-/Potassium-ion Batteries

The continuous consumption of fossil fuel has raised the concerns over the depletion of fossil fuel and global warming. In light of this, renewable energy resources, such as wind and solar, have been developed and become the fastest-growing sources for power generation. Rechargeable batteries is crucial to mitigate the intermittent nature of solar and wind energy to achieve sustainability for the society. A suitable battery technology for the large scale energy storage application should be of high energy density and low cost. The limited and uneven distribution of lithium resource in the earth crust restricts the widely use of the state-of-the-art lithium ion batteries (LIBs) in large scale energy storage application. Sodium ion batteries (SIBs) and potassium ion batteries (PIBs) have attracted tremendous attention as promising alternatives to LIBs, thanks to the abundance of sodium and potassium in earth crust. In addition, the SIBs and PIBs production cost can be further reduced by using aluminium foil as current collector instead of copper foil in LIBs as the aluminium is proved to be stable to sodium/potassium even at low voltage range. The large sodium/potassium ion radius results in sluggish kinetics during electrochemical processes which make some successful LIBs anode materials unworkable for SIBs and PIBs. Although tremendous efforts have been devoted to the development of anode materials, there is still a long way to go to achieve feasible anode materials for SIBs and PIBs commercialization. Among the various proposed anode materials, including carbonaceous materials, alloy materials and metal sulphides. Metal phosphide is one of the most appealing anode materials for both SIBs and PIBs, because of its high theoretical capacity and suitable working voltage window. Nevertheless, metal phosphide undergoes large volume expansion during the cycling, leading to pulverization of the electrode materials and fast capacity fading during long-term cycling.