Vacancy-Engineered High-Conductivity Chloride Solid-State Electrolytes for Long-Life All-Solid-State Batteries
Rechargeable lithium-ion batteries (LIBs) are ubiquitous in portable electronics and electric vehicles, yet their flammable liquid electrolytes pose safety hazards and limit energy density. All-solid-state batteries (ASSBs) with solid-state electrolytes (SSEs) offer enhanced safety and higher energy density. Among SSEs, metal chloride SSEs (Li aMCl b, M = In, Y, Er) combine high ionic conductivity, mechanical deformability, and compatibility with high-voltage cathodes. However, their ionic conductivity and anode stability require improvement. Here, we introduce pentavalent Ta5+ doping into Li3InCl6 (LIC) to engineer Li+ vacancies via charge compensation, yielding Li3−2xIn1−xTaxCl6 (LITxC, 0 ≤ x ≤ 0.6). Ta5+ incorporation efficiently increases Li+ vacancy content without disrupting the cubic close packing (ccp) structure. The optimized composition, Li2.4In0.7Ta0.3Cl6 (LIT0.3C), achieves an ionic conductivity of 2.19 mS cm−1 at 30 °C and a low activation energy of 0.273 eV, balancing vacancy concentration and Li+ content. Ta5+ doping also enhances kinetic stability against the anode. ASSBs with LIT0.3C demonstrate excellent cycling stability: Ni90 cathodes retain 72.3% capacity after 1000 cycles at 0.5 C, while NCM523 cathodes retain 84.1% after 500 cycles at 0.2 C and 80.7% after 1000 cycles. These results highlight a practical strategy for improving chloride SSE performance, offering new insights for high-performance ASSB design.