Deflecting lithium dendritic cracks in multi-layered solid electrolytes

Charging current densities of solid-state batteries with lithium metal anodes and ceramic electrolytes are severely limited due to lithium dendrites that penetrate the electrolyte leading to a short circuit. We show that dendrite growth can be inhibited by different crack deflection mechanisms when multi-layered solid electrolytes, such as Li₆PS₅Cl/Li₃ScCl₆/Li₆PS₅Cl and Li₆PS₅Cl/Li₁₀GeP₂S₁₂/Li₆PS₅Cl, are employed but not when the inner layer is Li₃PS₄. X-ray tomographic imaging shows crack deflection along mechanically weak interfaces between solid electrolytes as a result of local mismatches in elastic moduli. Cracks are also deflected laterally within Li₃ScCl₆, which contains preferentially oriented particles. Deflection occurs without lithium being present. In cases where the inner layers react with lithium, the resulting decomposition products can fill and block crack propagation. All three mechanisms are effective at low stack pressures. Operating at 2.5 MPa, multi-layered solid electrolytes Li₆PS₅Cl/Li₃ScCl₆/Li₆PS₅Cl and Li₆PS₅Cl/Li₁₀GeP₂S₁₂/Li₆PS₅Cl can achieve lithium plating at current densities exceeding 15 mA cm⁻².