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

Abstract

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 ₂(-ACl)-A ₂ZrCl ₆ (A = Li or Na) that demonstrate improved ionic conductivities at 30 °C, from 0.40 to 1.3 mS cm ⁻¹ and from 0.011 to 0.11 mS cm ⁻¹ for Li ⁺ and Na ⁺, respectively, compared to A ₂ZrCl ₆, and improved compatibility with sulfide solid electrolytes. The mechanochemical method employing Li ₂O 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 ⁶Li 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 Li ₂ZrCl ₆, the fluorinated ZrO ₂−2Li ₂ZrCl ₅F HNSE shows improved high-voltage stability and interfacial compatibility with Li ₆PS ₅Cl 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||LiNi _0.88Co _0.11Mn _0.01O ₂ all-solid-state lab-scale cell operating at 30 °C and 70 MPa and capable of delivering a specific discharge of 115 mAh g ⁻¹ after almost 2000 cycles at 400 mA g ⁻¹.

Abstract

Compositional tuning is a standard procedure to improve the ionic conductivity of inorganic superionic conductors. Here, the authors report (electro)chemical stable composite halide solid electrolytes applying a nanostructure approach that promotes interfacial superionic conductivity.