The direct crystallization of a closo-borate solid electrolyte from solution is demonstrated and applied to infiltrate porous battery electrodes fabricated by traditional slurry casting methods. Employing isopropanol as a solvent, we show that Na4(B12H12)(B10H10) crystallizes inside the open porosity of the electrodes with the appropriate crystal structure yielding high ionic conductivity (1 mS cm-1 at 25 °C) and providing efficient contact to the active materials. Very stable cycling is demonstrated at 30 °C for NaCrO2|Na-Sn half cells employing infiltrated NaCrO2 cathodes with mass loadings of ~7.7 mg cm-2 at rates up to 5C (4.5 mA cm-2). The all-solid-state cells exhibit remarkable cycling stability at moderate (70 MPa), and low (3 MPa) applied external pressure, retaining 95.6% and 85.9% of the initial capacity after 100 cycles at 0.5C respectively. A NaCrO2|Sn rocking-chair all-solid-state full cell with capacity-balanced infiltrated electrodes is also demonstrated. The more pronounced fading of the full cell is characterized with a three-electrode measurement and can be attributed to the poorer cyclability of Sn. This work bridges the gap between the attractive materials properties of closo-borate electrolytes and their integration into all-solid-state batteries facilitating their adoption in industrial cell production at scale.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)
- Energy Engineering and Power Technology