Salt-Assisted Recovery of Sodium Metal Anodes for High-Rate Capability Sodium Batteries

Rechargeable sodium metal batteries are considered to be one of the most promising high energy density and cost-effective electrochemical energy storage systems. However, their practicality is constrained by the high reactivity of sodium metal anodes that readily brings about excessive accumulation of inactive Na species on the surface, either by chemical reactions with oxygen and moisture during electrode handling or through electrochemical processes with electrolytes during battery operation. Herein, this paper reports on an alkali, salt-assisted, assembly-polymerization strategy to recover Na activity and to reinforce the solid-electrolyte interphase (SEI) of sodium metal anodes. To achieve this, an alkali-reactive coupling agent 3-glycidoxypropyltrimethoxysilane (GPTMS) is applied to convert inactive Na species into Si-O-Na coordination with a self-assembly GPTMS layer that consists of inner O-Si-O networks and outer hydrophobic epoxides. As a result, the electrochemical activity of Na metal anodes can be fully recovered and the robust GPTMS-derived SEI layer ensures high capacity and long-term cycling under an ultrahigh rate of 30 C (93.1 mAh g^-1, 94.8% after 3000 cycles). This novel process provides surface engineering clues on designing high power density and cost-effective alkaline metal batteries.