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

<br/>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 [1-3]. Here, we demonstrate stable dis-/charge cycling of solid-state lithium-ion batteries combining a Li₃(CB₁₁H₁₂)₂(CB₉H₁₀) hydroborate electrolyte with a 4 V-class LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) cathode, exploiting the enhanced kinetic stability of the LiCB₁₁H₁₂-rich and LiCB₉H₁₀-poor electrolyte composition [4]. Cells with lithium metal and indium/lithium anodes achieve a discharge capacity at C/10 of ~145 mAh g^–1 at room temperature and ~175 mAh g^–1 at 60 °C. Indium/lithium cells retain 98% of their initial discharge capacity after 100 cycles at C/5 and 70% after 1000 cycles at C/2. Capacity retention of 97% after 100 cycles at C/5 and 75% after 350 cycles at C/2 is also achieved with a graphite anode without any excess lithium. The energy density per cathode composite weight of 460 Wh kg^–1 is on par with the best solid-state batteries reported to date.<br/><br/>[1] L. Duchêne, A. Remhof, H. Hagemann, D. Battaglia, Energy Storage Materials, 2020, 225, 782<br/>[2] L. Duchêne, R.-S. Kühnel, E. Stilp, E. Cuervo Reyes, A. Remhof, H. Hagemann, C. Battaglia, Energy & Environ. Science, 2017, 10, 2609<br/>[3] R. Asakura, D. Reber, L. Duchêne, S. Payandeh, A. Remhof, H. Hagemann, C. Battaglia, Energy & Environ. Science, 2020, 13, 5048<br/>[4] H. Braun, Ryo Asakura, A. Remhof, C. Battaglia, ACS Energy Lett. in press