Abstract

In this work, a graphene-enhanced LiCo0.525Ni0.475O2 (LCNOG) cathode was synthesized by self-propagating high-temperature synthesis and the effects of annealing at 650–850 °C were investigated. Sharper X-ray diffraction peaks showed enhanced crystallization with an increase in average crystallite size from 28 nm to 56 nm after annealing at 850 °C. LCNOG annealed at 850 °C delivered a high capacity of over 2030 J compared to 1280 J, with a near ideal coulombic efficiency of 99.5 % and long cycle stability. The acceleration of kinetics is evidenced by more favorable redox peak positions in voltammetry and a 5-fold lower interfacial resistance in electrochemical impedance spectroscopy. The improved performance is due to the larger grain size, higher crystallinity, increased conductivity and graphene-induced diffusion facilitation. The relationship between crystallinity and cathodic properties provides critical insight into cathode design. The exceptional performance achieved by tailoring crystallinity through annealing makes LCNOG a potential material for high-voltage cathodes for lithium-ion technology.

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