Abstract
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 1 V, enabling application as an anode (initial specific capacity >200 mAh g-1 with remarkably low volume change of ∼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 5 V and a low activation energy barrier (<0.2 eV) 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.
Highlights
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
To further demonstrate this chemical adjustment and how it pertains to property tuning, we report a tellurium analogue, which displays promising solid-electrolyte capabilities
Diffraction data from three target compositions Li1.5La1.5WO6, Li1.5La1.5TeO6 and Li1.5La1.5W0.5Te0.5O6 could readily be indexed using a monoclinically distorted variant of the perovskite structure. This distortion commonly arises from a combination of cation ordering over the octahedral sites and a tilting of the oxide octahedral to reduce the size of the large A-site interstice to better match the bonding requirements of A cations that are smaller than optimal
Summary
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. A lack of reliable solid-state electrolytes is currently hampering the development of all-solid-state batteries and complexities of delivering high Li-ion diffusion at the electrode–electrolyte interface mean that there is a pressing need for new families of functional solid-state materials to fulfil this role[7,8,9]. To address this challenge, we have turned to the perovskite family of compounds, where the prototype cubic structure possesses the formula unit ABO3, with A-site metal cations 12coordinated to oxygen and B-site cations octahedrally coordinated by 6 oxygen atoms. We have serendipitously discovered a lithium tungstate double perovskite, which has been independently identified by another group[19]
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