Enhancing Conversion Reversibility and Initial Coulombic Efficiency of SnO₂ Anodes via NiO/Ni-Carbon Interfacial...

Low initial Coulombic efficiency (ICE), caused by irreversible conversion reactions and excessive lithium consumption, remains a critical challenge for SnO₂-based anodes. In this work, we rationally construct a SnO₂-NiO/Ni-Carbon composite via a metal-organic framework (MOF)-derived strategy, in which SnO₂ nanoparticles are integrated with NiO/Ni heterophases embedded in a conductive carbon matrix. The interface-rich architecture enables synergistic regulation of conversion/alloying reactions and interfacial Li⁺ storage, thereby mitigating irreversible Li consumption in the first cycle. Benefiting from the strengthened interfacial interactions, the optimized SnO₂-NiO/Ni-Carbon electrode delivers an initial discharge capacity of 1102 mAh g^-1 and an initial charge capacity of 1035.1 mAh g^-1, corresponding to a high ICE of 93.9%. In addition, a reversible capacity of 1184.5 mAh g^-1 is maintained after 180 cycles at 0.2 A g^-1, demonstrating enhanced structural stability. Voltage-resolved electrochemical analysis suggests that the NiO/Ni heterointerfaces contribute to stabilizing the conversion reactions of SnO₂ and tailoring the early-stage interphase evolution. Density functional theory (DFT) calculations further reveal enhanced Li adsorption affinity at the SnO₂-NiO/Ni interfacial configurations (as a comparative descriptor), supporting the experimental observations. Furthermore, a lithium-ion capacitor assembled with the SnO₂-NiO/Ni-Carbon anode and activated carbon cathode exhibits an energy density of 183.9 Wh kg^-1 at a power density of 220 W kg^-1. This work highlights the critical role of multiphase interfacial engineering in simultaneously improving ICE and long-term cycling stability of SnO₂-based anodes.