Li1.5La1.5MO6 (M=W6+, Te6+) as a new series of lithium-rich double perovskites for all-solid-state lithium-ion batteries

Solid-state batteries are a proposed route to safely achieving high energy densities, yet this architecture faces challenges arising from interfacial issues between the electrode and solid electrolyte. Here we develop a novel family of double perovskites, Li1.5La1.5MO6 (M=W6+, Te6+), where an uncommon lithium-ion distribution enables macroscopic ion diffusion and tailored design of the composition allows us to switch functionality to either a negative electrode or a solid electrolyte. Introduction of tungsten allows reversible lithium-ion intercalation below 1V, enabling application as an anode (initial specific capacity >200 mAh g(-1) with remarkably low volume change of similar to 0.2%). By contrast, substitution of tungsten with tellurium induces redox stability, directing the functionality of the perovskite towards a solid-state electrolyte with electrochemical stability up to 5V and a low activation energy barrier (<0.2eV) for microscopic lithium-ion diffusion. Characterisation across multiple length- and time-scales allows interrogation of the structure-property relationships in these materials and preliminary examination of a solid-state cell employing both compositions suggests lattice-matching avenues show promise for all-solid-state batteries. The development of the all solid-state battery requires the formation of stable solid/solid interfaces between different battery components. Here the authors tailor the composition to form both electrolyte and anode from the same novel family of perovskites with shared crystal chemistry.