Strain-coordination strategy enabling long-cycling all-solid-state lithium-sulfur batteries.

Abstract

All-solid-state lithium-sulfur batteries offer high energy density and enhanced safety. However, their practical application is hindered by high external operating pressure to mitigate mechano-chemical failures at interfaces. Here we show a strain-coordination strategy that leverages the opposite volume changes of electrodes during cycling to reduce electrode-level stress evolution and the external pressure required for stable operation. Using an FeS₂ positive electrode and a prelithiated Si negative electrode as a representative system, we modulate the Li-to-Si ratio to achieve a near-zero-strain effect, where the expansion of FeS₂ and the contraction of Li₂Si partially counterbalance each other. This self-compensated electrode configuration mitigates mechano-electrochemical degradation under reduced pressure. As a result, the all-solid-state lithium-sulfur batteries deliver a discharge capacity of 868.4 mAh g^⁻1 at 15 MPa. Under 100 MPa, the cells achieve an areal capacity of 21.7 mAh cm^⁻2, and cycle life 4500 cycles at 1 C (60 min) and 140,000 cycles at 15 C (4 min). Furthermore, low-pressure all-solid-state pouch cells achieve stable cycling over 500 cycles at 15 MPa. This strain-coordination strategy provides an approach for enabling stable operation of all-solid-state batteries under reduced external pressure.