Stabilizing High-Voltage Lithium-Ion Battery Cathodes Using Functional Coatings of 2DTungsten Diselenide

Functional surface coatings were applied on high voltagespinel (LiNi0.5Mn1.5O4; LNMO) and Ni-rich (LiNi0.85Co0.1Mn0.05O2;NCM851005) NCM cathode materials using few-layered 2H tungstendiselenide (WSe2). Simple liquid-phase mixing with WSe2in 2-propanoland low-temperature (130 degrees C) heat treatment in nitrogenflow dramaticallyimproved electrochemical performance, including stable cycling, high-rateperformance, and lower voltage hysteresis in Li coin cells at 30 and 55 degrees C.Significantly improved capacity retention at 30 degrees C[Q401/Q9of 99% vs 38%for LNMO andQ322/Q23of 64% vs 46% for NCM851005] indicated efficientfunctionality. TEM and XPS clarified the coating distribution andcoordination with the cathode surface, while postcycling studies revealedits sustainability, enabling lower transition metal dissolution and minormorphological deformation/microcrack formation. A modified and stableSEI was apparently formed owing to W and Se deposition on the Li anodeduring cycling. The synergistic functionalization provided a significant dual benefit of cathodic and anodic stability.