Construction of Elastic and Conductive Channels for High-Rate and High-Areal-Capacity Sulfur Cathodes in All-Solid-State Lithium-Sulfur Batteries

All solid-state lithium-sulfur batteries (ASSLSBs) have attracted significant attention due to their enhanced safety and superior energy density. However, the considerable volume change during cycling poses a challenge, resulting in electrochemical-mechanical degradation. To address this issue, polypyrrole (PPy) is coated on a nitrogen-doped carbon nanotube (NCNT) network to exhibit suitable conductivity and compatibility with sulfide electrolyte. Functionally, PPy@NCNT provides a continuous and conductive pathway, reducing the tortuosity of charge transport. Mechanically, operando pressure measurements and atomic force microscopy (AFM) tests are conducted, demonstrating that the flexible and viscoelastic structure of PPy@NCNT can alleviate local stress. The axial pressure on the cathode can be reduced by 11% with a sulfur area capacity of 3 mg cm-2 at 30 degrees C. At a high areal mass loading of 4.5 mg cm-2, a high areal capacity of 6 mAh cm-2 (1348 mAh g-1, 1C = 1675 mA g-1) is achieved at 0.1C, maintaining stability over 300 cycles at 0.2C. Remarkably, it can achieve an areal capacity of over 8.8 mAh cm-2 and stable cycling even at 60 degrees C. This study, being the first to regulate mechano-electrochemical action in ASSLSBs with flexible conducting polymer, highlights the significance of integrating a continuous and elastic network into solid-state conversion-type cathodes. In all-solid-state lithium-sulfur batteries, the composite cathode necessitates a hierarchical control strategy. Integrating continuous flexible network polypyrrole@nitrogen-doped carbon nanotube (PPy@NCNT) into the sulfur composite cathode at the electrode level reduces the tortuosity of charge carriers and suppresses electrochemical-mechanical failures caused by significant volume changes. This enhancement facilitates improved capacity utilization of sulfur, enabling stable operation of the batteries. image