Unveiling the Capacity Enhancement Mechanism of Carbon Interlayers in Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries hold prominent advantages of high theoretical energy density of 2600 Wh kg⁻¹ but suffer from insufficient sulfur conversions. Introducing carbon interlayers is an effective strategy especially in increasing the discharge capacity in coin cells. Nevertheless, the underlying capacity enhancement mechanism afforded by carbon interlayers remains unclear, hindering their further optimization and application in practical devices. Herein, different geometric configurations of carbon interlayers are designed to unveil the actual capacity enhancement mechanism. Through correlating the dead zone area of coin cells with the capacity enhancement afforded by carbon interlayers, re-utilization of the lithium polysulfides diffused into the coin cell dead zones is identified as the primary cause while carbon interlayers are less effective in nearly dead-zone-free pouch cells. Therefore, carbon interlayers are more suitable as a platform for convenient and rapid activity evaluation of electrocatalysts tailored for Li–S batteries. This work re-recognizes the working mechanism and practical applicability of carbon interlayers and guides rational employment of carbon interlayers in developing advanced Li–S batteries.