Interfacial percolation enables high-conductivity lean-lithium oxychloride electrolytes for all-solid-state batteries

Inorganic solid-state electrolytes (SSEs) underpin the development of all-solid-state batteries (ASSBs), but their ionic conductivity relies heavily on Li-concentrated or even Li-stuffed materials, which not only elevates Li consumption but also compromises their (electro)chemical stability. Here, we establish an interfacial percolation strategy that enables high ionic conductivity at lean Li content, breaks the conventional dependence of ionic conductivity on high Li content, and allows tuning of electrolyte properties such as high-voltage stability. With a typical percolative SSE that consists of Ta2O5 nanocrystals embedded in an amorphous matrix (Ta2O5·a-LTOC), we demonstrate that, contrary to common perception, insulating dispersoids can lower Li concentration while increasing ionic conductivity by forming an interfacial percolation network. Ta2O5·a-LTOC achieves a high ionic conductivity of 15.2 mS cm−1 at a Li content of 1.46 wt% (6.4 mol L−1), together with high-voltage stability up to 4.8 V. As a result, ASSBs using Ta2O5·a-LTOC and high-nickel cathode materials deliver a long cycle life of 5000 cycles at 2 C, stable high-rate cycling of 4000 cycles at 6 C, and high-loading performance with an areal capacity > 3 mAh cm−2 and 80.4% capacity retention over 800 cycles. This interfacial percolation strategy provides a universal design route to lean-Li, highly conductive SSEs with tunable properties, thereby enabling high-energy and fast-charging ASSBs.