Anode Material Options Toward 500 Wh kg⁻¹ Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) battery is identified as one of the most promising next-generation energy storage systems due to its ultra-high theoretical energy density up to 2600 Wh kg⁻¹. However, Li metal anode suffers from dramatic volume change during cycling, continuous corrosion by polysulfide electrolyte, and dendrite formation, rendering limited cycling lifespan. Considering Li metal anode as a double-edged sword that contributes to ultrahigh energy density as well as limited cycling lifespan, it is necessary to evaluate Li-based alloy as anode materials to substitute Li metal for high-performance Li–S batteries. In this contribution, the authors systematically evaluate the potential and feasibility of using Li metal or Li-based alloys to construct Li–S batteries with an actual energy density of 500 Wh kg⁻¹. A quantitative analysis method is proposed by evaluating the required amount of electrolyte for a targeted energy density. Based on a three-level (ideal material level, practical electrode level, and pouch cell level) analysis, highly lithiated lithium–magnesium (Li–Mg) alloy is capable to achieve 500 Wh kg⁻¹ Li–S batteries besides Li metal. Accordingly, research on Li–Mg and other Li-based alloys are reviewed to inspire a promising pathway to realize high-energy-density and long-cycling Li–S batteries.