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 LiNi 0.83 Co 0.14 Mn 0.03 O 2 (NCM) for Li 6 PS 5 Cl-type all-solid-state batteries is reported. A 10% Li 3 InCl 6 -coated NCM material was assembled into a 10% LIC@NCM/Li 6 PS 5 Cl/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 Li 6 PS 5 Cl 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 LI 6 PS 5 Cl during cycling, and the capacity increase at high rates is due to the reduction of the interfacial impedance between the cathode material and LI 6 PS 5 Cl solid electrolyte.