Hydroborate-Based Solid Electrolytes for All-Solid-State Batteries

Abstract

Hydroborates, i.e. ionic salts of boron-hydrogen compounds, are an emerging material class of solid electrolytes for all-solid-state batteries.In particular, some of the metal hydroborates (≠ neutral hydroboranes) featuring three-dimensional anion clusters exhibit exceptional thermal and (electro)chemical stability, and liquid-like ionic conductivity with a unique ion conduction mechanism. These characteristics enable the fabrication of competitive all-solid-state cells with stable battery cycling performance. This chapter reviews the attractive material properties of hydroborates and their implementation as highly conductive solid electrolytes in all-solid-state batteries.

Li4B10H10B12H12 as solid electrolyte for solid-state lithium batteries

“…They generally exhibit high thermal and chemical stability, so mechanical properties enabling cold pressing, solution processability, and low toxicity. 6,7 As solid electrolytes, they exhibit a cation transference number of almost unity due to an immobile anion framework. 8,9 Hydridoborates typically reach ionic conductivities of the order of 0.01-0.1 S cm −1 in their high-temperature disordered phases, while exhibiting much lower conductivities (below 10 −7 S cm −1 ) at room temperature.…”

“…They generally exhibit high thermal and chemical stability, soft mechanical properties enabling cold pressing, solution processability, and low toxicity. 6,7 As solid electrolytes, they exhibit a cation transference number of almost unity due to an immobile anion framework. 8,9…”

On the Local Structure in Ordered and Disordered Closo-hydroborate Solid Electrolytes

“…Na + closo -hydroborates have recently garnered increasing research interest as solid electrolytes for all-solid-state battery applications. − This solid electrolyte class combines several desirable properties for the implementation in solid-state batteries, such as high room-temperature ionic conductivity, low density, good mechanical processability and low toxicity. , Especially, the reports of 3 and 4 V all-solid-state Na batteries employing Na + hydroborate solid electrolytes have highlighted the relevance and applicability of these materials for energy storage technologies. , …”

Elucidating the pressure-induced enhancement of ionic conductivity in sodium closo-hydroborate electrolytes for all-solid-state batteries

“…and Na/Na ? ), low gravimetric densities (B 1.2 g cm -3 ); high thermal and chemical stability, soft mechanical properties enabling cold pressing, solution processability and low toxicity [1,2]. Hydroborates typically undergo order/disorder phase transitions from a phase with low cation conductivity to a phase with high cation conductivity at elevated temperatures.…”