Unmasking the intrinsic cycling evolution of manganese 1,3,5-benzenetri-carboxylate metal organic framework Li-battery anodes using additive-free alternating current electrophoretic deposition thin films

초록

Metal-organic framework (MOF) anodes can undergo substantial electrochemical and interfacial evolution during repeated lithiation/delithiation, yet these changes are often obscured in conventional slurry electrodes by polymer binders, conductive carbon, and complex composite architectures. Here, we report binder- and conductive-additive-free manganese 1,3,5-benzenetricarboxylate (Mn-BTC) thin-film anodes fabricated by alternating current electrophoretic deposition (AC-EPD) as a clean platform for directly probing cycling-induced evolution in an intrinsic MOF electrode. The additive-free thin-film configuration enables the electrochemical response of Mn-BTC and its evolving electrode/electrolyte interface to be monitored with minimal contribution from inactive components. During long-term cycling, the Mn-BTC electrode exhibits pronounced electrochemical activation, with the reversible capacity increasing by approximately fourfold rather than undergoing conventional capacity fading. This activation is accompanied by clear evolution of charge-discharge and dQ/dV profiles, indicating the progressive development of additional reversible Li-storage pathways. Kinetic analyses reveal enhanced pseudocapacitive contribution and improved Li+ transport after cycling, while electrochemical impedance spectroscopy fitting shows a decrease in charge-transfer resistance from 3493 to 42 Omega and an increase in apparent Li+ diffusivity from 7.1 & times; 10-13 to 2.0 & times; 10-12 cm2s-1. Post-cycling scanning electron microscopy and x-ray photoelectron spectroscopy further support interfacial and morphological reconstruction of the MnBTC electrode. These results demonstrate that repeated cycling progressively activates the Mn-BTC framework by improving electrochemical accessibility, interfacial charge transfer, and ion transport. This work highlights AC-EPD as an effective additive-free platform for directly observing cycling-induced interfacial and kinetic evolution in MOF-based battery electrodes.

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