Architected continuum mixed ionic and electronic conducting alloy negative electrode for fast-charging all-solid-state lithium batteries

All-solid-state lithium batteries for electric vehicles require high specific power, challenged in thick negative electrodes by fragile conducting networks during volume changes and dendrite growth at high currents. We propose an In_0.38Sn_0.33Bi_0.29 ternary alloy negative electrode creating a mixed ionic-electronic conducting continuum that overcomes these limitations. The stepwise formation of multiple phases with sufficient mechanical robustness during Li-alloying effectively stabilizes the ionic and electronic conducting percolation by relieving stress concentration and minimizing crack propagation. The unique reversibility of the multiple phase changes during lithiation/delithiation ensures stable cycling performance. The In_0.38Sn_0.33Bi_0.29 negative electrode exhibits a high capacity of ~ 724 mAh g^-1 and a critical current density of 150 mA cm^-2 at 5.0 mAh cm^-2. The In_0.38Sn_0.33Bi_0.29 | |LiCoO₂ full cell with industry-level mass loading (6.49 mAh cm^-2) can retain 87.5% capacity over 1300 cycles at 4.0 C, delivering a jellyroll specific energy of 203.1 Wh kg^-1 and 670.6 Wh L^-1 at 5.0 C. The fast-charging capability is further validated by large-format pouch cells. The design principles can be extended to other negative electrode designs for solid-state batteries.