Flexible Organic-Polyphosphates Interfacial Layer for Stable Lithium Metal Anode.

Lithium (Li) metal is regarded as a desired anode candidate for high-energy-density rechargeable battery systems in the future because of its high specific capacity and low redox potential. However, Li dendritic growth and volume expansion during cycling severely hinder its practical application. Herein, an artificial organophosphorus-inorganic Li hybrid flexbile solid electrolyte interphase (SEI) layer was designed by a prereaction between phytic acid (PA) and lithium hydroxide (LiOH) to generate metal chelates for quick Li⁺ conductivity. The organic-polyphosphate (PALi) layer not only can provide numerous channels for Li⁺ to migrate quickly but also can improve its lithiophilicity due to the uniform distribution of phosphorus (P) in the PALi layer; meanwhile, flexibility due to the existence of hydrogen bonds in the PALi layer effectively alleviates the effect of Li volume expansion on the SEI layer. Therefore, the PALi@Cu∥Li cells exhibit a high Coulombic efficiency of 98.85% over 500 cycles at a current density of 0.5 mA cm^-2, and the PALi@Cu-Li∥Li symmetrical cells also can maintain good cycling stability with low voltage hysteresis of 20 mV for 2000 h at a current density of 1 mA cm^-2. This organic-inorganic hybrid strategy provides a feasible way to fabricate a stable and efficient artificial SEI layer for the practical applications of Li metal batteries.