Boosting the interfacial superionic conduction of halide solid electrolytes for all-solid-state batteries.

Designing highly conductive and (electro)chemical stable inorganic solid electrolytes using cost-effective materials is crucial for developing all-solid-state batteries. Here, we report halide nanocomposite solid electrolytes (HNSEs) ZrO(-ACl)-AZrCl (A = Li or Na) that demonstrate improved ionic conductivities at 30 °C, from 0.40 to 1.3 mS cm and from 0.011 to 0.11 mS cm for Li and Na, respectively, compared to AZrCl, and improved compatibility with sulfide solid electrolytes. The mechanochemical method employing LiO for the HNSEs synthesis enables the formation of nanostructured networks that promote interfacial superionic conduction. Via density functional theory calculations combined with synchrotron X-ray and Li nuclear magnetic resonance measurements and analyses, we demonstrate that interfacial oxygen-substituted compounds are responsible for the boosted interfacial conduction mechanism. Compared to state-of-the-art LiZrCl, the fluorinated ZrO-2LiZrClF HNSE shows improved high-voltage stability and interfacial compatibility with LiPSCl and layered lithium transition metal oxide-based positive electrodes without detrimentally affecting Li conductivity. We also report the assembly and testing of a Li-In||LiNiCoMnO all-solid-state lab-scale cell operating at 30 °C and 70 MPa and capable of delivering a specific discharge of 115 mAh g after almost 2000 cycles at 400 mA g.