# Facile Synthesis of Inorganic Li2B12H12/LiI Solid Electrolytes for High‐Voltage All‐Solid‐State Lithium Batteries

## TL;DR

A new solid electrolyte for lithium batteries is developed with high conductivity and compatibility with high-voltage cathodes.

## Contribution

A novel hydroborate-based solid electrolyte with the highest reported ionic conductivity for its class is synthesized.

## Key findings

- The new electrolyte shows 0.75 mS cm−1 ionic conductivity at 25 °C.
- It enables stable cycling over 1000 hours with lithium metal anodes.
- It is compatible with high-voltage cathodes like LiCoO2 and NCM811.

## Abstract

Hydroborate‐based solid electrolytes (SEs), distinguished by their eco‐friendliness and non‐flammability have emerged as a research hotspot in energy storage research. Despite these advantages, their widespread adoption is constrained by insufficient ionic conductivity and poor high‐voltage compatibility. To overcome this challenge, a novel hydroborate SEs, 400‐0.6Li2B12H12‐0.4LiI (denoted as 400‐0.6B12‐0.4I), is engineered through a facile synthesis strategy combining high‐temperature processing (400 °C, 2 h, in Ar) and LiI doping. 400‐0.6B12‐0.4I exhibits an outstanding ionic conductivity up to 0.75 mS cm−1 at 25 °C, which is the highest level among the reported inorganic Li2B12H12‐based SEs so far. It also improves the cycling stability against lithium metal anodes, limits dendrite growth with a high critical current density of 5.0 mA cm−2, which enables the Li symmetrical cells to cycle over 1000 h at 25 °C with only 10 mV of overpotential. Moreover, it cycles well in cells using lithium anodes and various high voltage (>4 V vs Li+/Li) cathodes materials such as LiCoO2, NCM811, and LiMn2O4. The proposed 400‐0.6B12‐0.4I SEs offer valuable guidance for designing next‐generation lithium‐ion solid electrolytes with superior ionic conductivity, enhanced interfacial stability, and exceptional electrode compatibility.

A novel hydroborate‐based solid electrolytes (SEs), 400‐0.6Li2B12H12‐0.4LiI (denoted as 400‐0.6B12‐0.4I), all‐solid‐state lithium batteries is developed through facile ball milling process. 400‐0.6B12‐0.4I exhibits the highest ionic conductivity among the reported inorganic Li2B12H12‐based SEs so far. It also cycles well with Li anode over 1000 h and compatible with various high voltage cathodes using Li3InCl6 layer. The proposed 400‐0.6B12‐0.4I SEs offer valuable guidance for designing next‐generation all‐solid‐state lithium batteries.