Pseudocapacitive charge storage in ultrathin NiCo-metal organic framework-derived NiCo2O4 Li-metal batteries

초록

This study presents the development of ultrathin NiCo-metal-organic-framework (MOF)-derived NiCo2O4 electrodes using an additive-free alternating current electrophoretic deposition (AC-EPD) method, offering a test platform to probe the electrode/electrolyte interface without bulk effects or other limiting factors. The ultrathin morphology ensures high surface-to-volume ratio, excellent lithium (Li)-ion accessibility, and minimized diffusion limitations. Electrochemical characterization revealed dominant pseudocapacitive charge storage, contributing 88 % of the surface capacitive effects, and high-rate performance enabled by efficient Li ion diffusivity, as demonstrated by a diffusion coefficient of 5.5 x 10-10 cm2 center dot s-1. Analysis of b-values from cyclic voltammetry confirmed that surface capacitive contributions are the primary mechanism at both oxidation (b = 0.89) and reduction (b = 0.98) potentials. The porous structure and nanoscale particle distribution in the AC-EPD NiCo-MOF derived NiCo2O4 electrode, combined with its pseudocapacitive behavior, significantly enhance lithium-ion storage capabilities, ensuring stability at high charge/discharge rates. These findings underscore the potential of NiCo-MOF-derived electrodes for high-performance lithium-ion batteries while offering a powerful platform for studying interfacial electrochemical processes critical for next-generation energy storage technologies.

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