Binder-free carbon fiber-based lithium-nickel-manganese-oxide composite cathode with improved electrochemical stability against high voltage: Effects of composition on electrode performance

Abstract

A binder-free nickel-manganese-based cathode is developed using carbon fibers as current collector via a low-temperature sequential process including electrodeposition, hydrothermal reaction, and calcination. The physical and electrochemical properties of the fiber-type cathodes are found to depend significantly on the Mn:Ni molar ratio and calcination temperature. The typical cathode material exhibits flake-like morphology and is composed of spinel LiMn2O4 (LMO), LiNi0.5Mn1.5O4 (LNMO), and lithium-rich layered Li2MnO3 (LRL–LMO), forming an LMO/LNMO composite. During electrochemical evaluation under high voltage operation at 2.5–4.9 V, the fiber-type LMO/LNMO cathode shows discharge capacity of ∼140 mAh g−1 with enhanced discharge voltage and stable cycle performance with over 98% capacity retention after 50 cycles. The capacity of fiber-type LMO cathode decays from 120 mAh g−1 with cycling (2.5–4.9 V), and begins to fail at the 12th cycle. Hence, the spinel LNMO can function as a framework to stabilize the LMO/LNMO composite material against high voltage. Fiber-type LMO/LNMO cathode benefits from the integrated electrochemical characteristics of spinel LMO, LNMO, and LRL-LMO, leading to improved electrode performance.