Hydroborate Solid-State Lithium Battery with High-Voltage NMC811 Cathode

Abstract

Hydroborate solid electrolytes offer high ionic conductivity and are stable in contact with alkali metal anodes but are challenging to integrate into batteries with high-voltage cathodes. Here, we demonstrate stable dis-/charge cycling of solid-state Li batteries combining a Li₃(CB₁₁H₁₂)₂(CB₉H₁₀) hydroborate electrolyte with a 4 V-class LiNi₀.₈Mn₀.₁Co₀.₁O₂ (NMC811) cathode, exploiting the enhanced kinetic stability of the LiCB₁₁H₁₂-rich and LiCB₉H₁₀-poor electrolyte composition. Cells with Li metal and InLi anodes achieve a discharge capacity at C/10 of ∼145 mAh g⁻¹ at room temperature and ∼175 mAh g⁻¹ at 60 °C. InLi cells retain 98% of their initial discharge capacity after 100 cycles at C/5 and 70% after 1000 cycles at C/2. Capacity retentions of 97% after 100 cycles at C/5 and 75% after 350 cycles at C/2 are also achieved with a graphite anode without any excess Li. The energy density per cathode composite weight of 460 Wh kg⁻¹ is on par with the best solid-state batteries reported to date.