Challenges and key parameters in exploring the cyclability limitation of practical lithium–sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries have become the most promising candidates for next-generation power storage technologies owing to their ultrahigh energy density and low cost. However, practical Li–S batteries, operated under harsh conditions with high sulfur loading, low electrolyte-to-sulfur (E/S) ratio and low negative-to-positive capacity ratio (N/P), are significantly impeded by several inherent drawbacks, including the shuttle effect of polysulfide intermediates, short lifespan, and sluggish reaction kinetics. Herein, we systematically summarize and analyze the cyclability of Li–S batteries with an areal capacity over 5 mA h cm⁻², and particularly pay great attention to the key parameters of high-sulfur-loading cathodes tested under low E/S ratio (E/S ≤5 μL mg⁻¹) and N/P ratio (N/P ≤5) circumstances to point out key strategies for the optimization of electrochemical performance. We clarify the development roadmap, analyze related scientific challenges, standardize the electrochemical test conditions of practical sulfur cathodes and uncover the cyclability limits to promote the industrialized process of lithium–sulfur batteries. We systematically summarize the current Li–S pouch batteries with considerable performance under practical conditions and also emphasize the failure mechanism analysis. Consequently, this review not only provides various thresholds of electrochemical properties in both coin cells and pouch cells but also offers feasible devices to facilitate practical and commercial applications of lithium–sulfur batteries in the near future.