Unveiling Solid-State Electrochemical Oxidation of LiBH₄ and Li₂B₁₂H₁₂ for High-Voltage All-Solid-State Batteries
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2025-07-14
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Journal Article
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Abstract
Hydridoborates are an emerging class of solid electrolytes that offer high ionic conductivity, low density, solution processability, compatibility with metallic anodes, and high oxidative stability. Notably, certain Li⁺ or Na⁺ solid electrolytes, consisting of two different cage-like closo-hydridoborate anion species, are compatible with 4 V-class cathodes by forming a sufficiently ion-conductive, passivating interphase. However, the nature of their electrochemical decomposition products and their dependence on electrochemical potentials remain unclear. In this combined theoretical and experimental study, we demonstrate the solid-state electrochemical oxidation of LiBH₄ to Li₂B₁₂H₁₂ above 2.0 V vs Li⁺/Li and provide evidence for the successive oxidation of closo-[B₁₂H₁₂]²⁻ anions to larger H-interconnected closo-clusters. This supports the observed trend that larger clusters formed via oxidation are stabilized at higher electrochemical potentials. Notably, the oxidation process from LiBH₄ toLi₂B₁₂H₁₂ proceeds through the formation of a highly conductive [BH₄]⁻–[B₁₂H₁₂]²⁻ mixed phase, indicating the potential for in situ formation of mixed-anion hydridoborates directly within all-solid-state cells. These insights into solid-state electrochemical decomposition at the solid-solid interfaces are transferable to other hydridoborate systems, regardless of cation species or anion structures, contributing to developing cathode design strategies for high-voltage all-solid-state batteries.
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8 (13)
Pages / Article No.
9637 - 9645
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American Chemical Society
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Subject
all-solid-state batteries; solid electrolytes; lithium-ion conductors; hydridoborates; borohydrides; first-principles calculations; electrochemical stability