Boosting Ion Conduction and Moisture Stability Through Zn2+ Substitution of Chloride Electrolytes for All‐Solid‐State Lithium Batteries

A soft acidic Zn²⁺ doping strategy is used to achieve high-performance Zr-based chloride SEs with excellent ionic conductivity and superior moisture stability. The optimized ionic conductivity of Li_2.4Zr_0.8Zn_0.2Cl₆ (x = 0.2) reaches a value as high as 1.13 mS cm⁻¹ at 30 °C. Furthermore, the LZZC also demonstrates impressive moisture stability, maintaining its structural integrity after exposure to moist air. The atomic-scale mechanism underlying the impact of Zn²⁺ doping on moisture stability of LZC is revealed by DFT calculations. The assembled LCO|LZZC-LPSC|Li-In cell delivers a high-rate performance and long cycling life (>84% capacity after 400 cycles at 0.5C). Moreover, the NCM811|LZZC-LPSC|Li-In ASSLBs show a high initial capacity of 165.2 mAh g⁻¹ and great cycling performance (135 mAh g⁻¹ after 600 cycles at 0.3 C).

Abstract

The recently emerged chloride solid electrolytes have garnered significant attention due to their superior ionic conductivity, wide electrochemical stability window, and exceptional compatibility with high-voltage oxide cathodes. Nevertheless, the currently cost-effective Zr-based chloride solid electrolytes face significant challenges, including low ionic conductivity and poor moisture stability. Herein, a versatile Zn²⁺-doped Zr-based chloride electrolyte is presented, designed to meet the aforementioned requirements. The optimized Li_2.4Zr_0.8Zn_0.2Cl₆ exhibits an improved ionic conductivity of 1.13 mS cm⁻¹ at 30 °C. Simultaneously, the Li_2.4Zr_0.8Zn_0.2Cl₆ also demonstrates impressive moisture stability, maintaining its structural integrity after exposure to humid air. The mechanism underlying the enhanced moisture stability of Li_2.4Zr_0.8Zn_0.2Cl₆ is further elucidated by density functional theory calculations. Most notably, whether coupled with LiCoO₂ or LiNi_0.8Mn_0.1Co_0.1O₂ cathodes, Li_2.4Zr_0.8Zn_0.2Cl₆-based all-solid-state batteries demonstrate exceptional cycling stability and rate performance. This high ionic conduction and moisture-resistant chloride electrolyte holds great promise for significantly advancing the commercialization of all-solid-state lithium batteries.