摘要
Cation disorder presents a compelling strategy to simultaneously tailor lattice dynamics, electronic structure, and ion transport in alloy-type anode materials. Herein, a Ge-Sn co-substituted chalcogenide, Cu2Sn0.5Ge0.5S3, is designed that leverages compositional disorder to activate synergistic phonon-electron-ion coupling for high-performance potassium-ion storage. Isovalent substitution of Sn with Ge induces pronounced lattice distortion and coordination asymmetry, generating dual-frequency phonon modes that combine soft Sn-derived vibrations with Ge-induced rigidity. This engineered phononic landscape facilitates stress-adaptive structural responses, effectively accommodating large volume changes during cycling. Simultaneously, disrupted cation ordering introduces band tail states and enhances electronic delocalization, increasing the DOS near E F (transport-relevant) and thereby facilitating charge transfer. Density functional theory calculations reveal a shallow d-band center (-4.38 eV), which enhances orbital overlap with K2Sx intermediates, promotes interfacial adsorption, and accelerates redox kinetics. Additionally, a low K+ adsorption energy (-0.568 kcal mol-1) and the emergence of low-electron-density regions contribute to fast K+ migration and efficient charge transfer. These combined effects yield a high reversible capacity (503.1 mAh g-1), excellent rate capability (10 A g-1), a high K+ diffusion coefficient (6.17 x 10-9 cm2 s-1), and stability over 2000 cycles, establishing Cu2Sn0.5Ge0.5S3 as a model system for stress-resilient and kinetically optimized potassium-ion batteries.