Microstructure-Controlled Electronic Percolation and Interfacial Conversion in Fe(II)-Tartrate/Carbon Anodes: A Three-Dimensional Chemical-Physics Framework

The electrochemical response of conversion-type anodes emerges from strongly coupled electronic, ionic, interfacial, and structural processes whose characteristic length scales extend from nanoscale tunnelling contacts to the electrode microstructure. A three-dimensional microstructure-resolved chemical-physics framework is developed to elucidate how conductive-carbon topology governs lithiation in Fe(II)-tartrate/carbon composite anodes. The reconstructed electrode explicitly resolves active particles, carbon agglomerates, binder-covered interfaces, electrolyte-filled pores, and drying-induced cracks, while coupling resistance-dependent electronic tunnelling, concentrated-solution ion transport, solid-state lithium diffusion, sequential conversion reactions, solid–electrolyte interphase growth, and progressive contact degradation. Stochastic reconstruction reveals that the geometric carbon-percolation threshold is 0.069 for a homogeneous network, with a 95% confidence interval of 0.065–0.073, whereas strong carbon aggregation shifts the threshold to 0.101. Importantly, formation of a spanning conductive pathway does not coincide with complete electrochemical accessibility, demonstrating that geometric connectivity and reactive utilization represent physically distinct states. Across the investigated composition range, active-material utilization increases from 0.14 to 0.94 while electronic polarization decreases from 226 to 12 mV. Validation against independent structural, conductivity, impedance, and galvanostatic measurements gives an aggregate mean absolute percentage error of 7.5%. The results establish a mechanistic connection between stochastic carbon-network organization, interfacial charge transport, and conversion kinetics, providing a chemical-physics basis for rational design of high-capacity conversion electrodes.

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