Investigation of Garnet Solid Electrolyte-Layered Oxide Cathode Interfaces Towards Cylindrical High-Performance Li-Ion Batteries

Abstract

Even though the Ni-rich cathode materials (Ni content > 60%), providing high energy density and high capacity, can draw much attention for advanced lithium-ion battery (LIB) community and industry, several drawbacks such as poor structural stability, thermal stability, and capacity fading still restrict their scalable application. Herein, the trace amount of garnet Li7La3Zr2O12 (LLZO) oxide solid-state electrolyte was introduced on the LiNi0.8Mn 0.1 Co0.1O2 (NMC811) cathode as a scaffolding interfacial layer on NMC particles via a one-step solvent-free mechanofusion process. The interfacial La-Ni exchange after mechanofusion was investigated by the extended X-ray absorption fine structure (EXAFS) measurement. Subsequently, the in situ X-ray diffraction was used to investigate the crystallographic evolution during the charge-discharge process. The NMC-LLZO cathode exhibits excellent rate capability and cycling performance, especially at high current density. The LLZO interfacial layer was found to be able to delay Li insertion into NMC bulk which in turn led to a better Li distribution and higher rate capability over pristine NMC. The practical applications of NMC-LLZO are also presented in 2.5 Ah 18650-format lithium-ion batteries. The cells can perform from C/10 to 1C with only 16% capacity reduction and remain 80% retention after cycled up to 500 cycles at a high current density of 1C compared to 40% of NMC cells. Keywords: LiNi0.8Mn0.1Co0.1O2, Lithium-ion batteries, Oxide solid-state electrolyte, Scaffolding layer, High current density