Stabilizing cathode-electrolyte interphase of LiNi0.5Mn1.5O4 high-voltage spinel by blending garnet solid electrolyte in lithium-ion batteries

This work presents a strategy of blending Li6.7La3Zr1.7Ta0.3O12 (LLZT) garnet solid electrolyte into LiNi0.5Mn1.5O4 (LNMO) high-voltage spinel cathode to enhance electrochemical performances and stabilities of electrode/electrolyte interphase layers in full-cells. Among a series of samples, 5 wt% LLZT blended LNMO delivered improved capacity, cycle life, and rate capability compared with a bare LNMO. The improvement mechanism of LLZT blended cathode can be explained in two folds. First, LLZT contacts with LNMO and improves Li+ transport properties of the cathode-electrolyte interphase (CEI) layer, as evidenced by electrochemical impedance spectroscopy (EIS) and distribution of relaxation time (DRT) analyses. Second, LLZT can scavenge moisture/proton in the electrolyte, oxidative decomposition products from the electrolyte, and suppress the degradation of CEI and solid-electrolyte interphase (SEI) layers during extended cycles, as evidenced by X-ray photoelectron spectroscopy (XPS). As a result, the 5 wt% LLZT blended LNMO cathode delivered a stable electrochemical performance even in the presence of 5000 ppm moisture (and thus HF) in an electrolyte. In contrast to the traditional surface coating methods, the solid-electrolyte blending approach is cost-effective, manufacturing/environmentally friendly, and thereby can serve as a practical pathway for improving the performances and stability of current battery cells for EV and small electronics.