Synergistic halide-sulfide hybrid solid electrolytes for Ni-rich cathodes design guided by digital twin for all-solid-State Li batteries

Halide solid electrolytes are a promising candidate for all-solid-state Li batteries (ASLBs) owing to their mechanical sintering ability and excellent (electro)chemical oxidation stability. However, these advantages are counteracted by the lower Li⁺ conductivities and higher specific densities compared with those of sulfides. Herein, a novel halide-sulfide hybrid catholyte design for Ni-rich layered oxide cathodes for ASLBs is reported. In a hybrid catholyte, Li₃YCl₆ (0.40 mS cm⁻¹) coatings protect the surface of Li[Ni_0.88Co_0.11Al_0.01]O₂ while Li₆PS₅Cl (1.80 mS cm⁻¹) serves as a Li⁺ highway. Li[Ni_0.88Co_0.11Al_0.01]O₂ cathodes with an optimal fraction of Li₃YCl₆, 10 wt% with respect to Li [Ni_0.88Co_0.11Al_0.01]O₂, substantially outperform electrodes using either Li₆PS₅Cl or Li₃YCl₆ in terms of capacity (202 vs. 171 or 191 mA h g⁻¹ at 0.1C, respectively), initial Coulombic efficiency, rate capability, and cycling performance. The superiority of Li₃YCl₆ for interfacial stability in the Li₃YCl₆-coated electrode to the electrode without Li₃YCl₆ is confirmed by complementary analysis. Moreover, the digital twin model is successfully established and reveals electrically isolated Li[Ni_0.88Co_0.11Al_0.01]O₂ particles when 14 wt% Li₃YCl₆ is used. This insight leads to the development of a mixed conductor coating consisting of Li₃YCl₆ and carbon, further enhancing the performance: e.g., 134 vs. 53 mA h g⁻¹ at 2C.