Mechanical Behavior and Dendrite Resistance of closo-Hydroborate Solid Electrolyte

Stack pressure and mechanical robustness are two important parameters needed to tackle the interfacial instability of solid-state batteries. Here, the mechanical behavior of Na4(CB11H12)2(B12H12), as solid electrolyte at the interface with Na anode, is reported. The solid electrolyte is tested as function of stack pressure and different current densities, revealing a critical current density of 0.6 mA cm−2 at room temperature and an optimal stack pressure of 1.5 MPa. These findings are achieved, thanks to the adoption of a multilayer approach, demonstrating the powerfulness of hydroborates to compensate chemical and electrochemical instability, simply employing different complex hydride polyanions that change locally the electrochemical properties while preserving structural and chemical coherence.