Highly Stable Sodium Metal Anodes for Sodium Batteries By Tactically Regulating the Solid Electrolyte Interphase

Abstract

Sodium (Na) metal holds great promise as an attractive anode material for grid-scale energy storage systems owing to its high theoretical specific capacity, low electrochemical potential, low cost and high natural abundance. However, its highly reactive nature with organic electrolyte leads to the formation of unstable solid electrolyte interphase (SEI) and dendritic/mossy Na growth. To overcome these issues, we present highly stable and dendrite-free Na metal anodes over a wide current range and long-term cycling via versatile tactical tunings of the SEI. Stable Na metal cycling in carbonate electrolyte without any additives over 100 cycles can be achieved at a current density up to 2 mA/cm2 with a high capacity of 3 mAh/cm2. In ether-based electrolyte, a superior cycling performance of Na anode can be achieved at a high current density up to 10 mA/cm2 and a capacity up to 5 mAh/cm2 over 100 cycles. Moreover, we found that despite the many similarities in the chemical and physical properties of lithium (Li) and Na, the strategy that was able to stabilize Li metal could not be directly applied to Na metal, but requires more meticulous investigations, thus providing new insights into understanding the differences between Li and Na systems.