High Lithium-Ion Conductivity, Halide-Coated, Ni-Rich NCM Improves Cycling Stability in Sulfide All-Solid-State Batteries

All-solid-state batteries attract significant attention owing to their potential to realize an energy storage system with higher safety and energy density. In this work, a halide electrolyte coating with high lithium-ion conductivity obtained by mechanical coating under n-heptane solvent and annealing at 200 °C of Ni-rich LiNi0.83Co0.14Mn0.03O2 (NCM) for Li6PS5Cl-type all-solid-state batteries is reported. A 10% Li3InCl6-coated NCM material was assembled into a 10% LIC@NCM/Li6PS5Cl/In all-solid-state battery with an initial charge capacity of 201.3 mAh g–1, a discharge specific capacity of 158.7 mAh g–1, and a Coulombic efficiency of 79.06%. After 100 cycles at room temperature at 0.1C current density, the capacity retention was 92% and the capacity retention was 72% after 270 cycles. In comparison, all-solid-state batteries using matched Li6PS5Cl and untreated NCM had a capacity retention rate of 53% after 100 cycles at 0.1C under the same charge/discharge regime and environment. It is indicated that the cycling performance and rate performance of the NCM material significantly improve after the 10% LIC coating. In this paper, X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), high-resolution high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), and other tests and analyses confirmed the following: the pregenerated interfacial layer of approximately 2 nm on the surface of NCM after the 10% halide solid electrolyte coating improves the structural stability of the material during charging and discharging, the LIC coating layer slows down the decomposition of LI6PS5Cl during cycling, and the capacity increase at high rates is due to the reduction of the interfacial impedance between the cathode material and LI6PS5Cl solid electrolyte.