Boron-doped mixed-halide argyrodite electrolytes for stable all-solid-state lithium metal batteries

Sulfide-based all-solid-state lithium metal batteries (ASSLMBs) are promising candidates for high-energy-density energy storage systems owing to high ionic conductivity (10⁻³–10⁻² S cm⁻¹) and favorable mechanical compliance of the sulfide solid electrolyte. Nevertheless, severe interfacial instability between sulfide electrolytes and lithium metal anodes, coupled with rampant lithium dendrite propagation, severely hinders their practical deployment. Herein, we rationally design a series of site-selective boron (B)-doped mixed-halide (Cl⁻/Br⁻) argyrodite sulfide electrolytes to simultaneously boost Li⁺ transport kinetics and stabilize the electrolyte-Li metal interface. Benefiting from B-induced optimized local crystal coordination and accelerated interfacial Li⁺ migration, the optimal B-doped electrolyte delivers a high ionic conductivity of 7.53 mS cm⁻¹, alongside drastically enhanced air tolerance and durable Li plating/stripping reversibility. Symmetric Li| electrolyte |Li cells sustain stable cycling for over 500 h at 1 mA cm⁻²/1 mAh cm⁻². When paired with Li metal anodes, full ASSLMBs exhibit substantially enhanced rate capability and long-term cyclability, retaining 75.3% of their initial capacity after 800 cycles at 1 C. Even under elevated temperature (50 °C) and high current rate (5 C), the cell maintains 68.2% capacity retention over 2000 cycles. This work establishes a feasible strategy to mitigate interfacial degradation, paving the way for scalable manufacturing of high-performance sulfide-based ASSLMBs.