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

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–C 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 0.1 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 675 W kg−1. This work highlights the critical role of multi-phase interfacial engineering in simultaneously improving ICE and long-term cycling stability of SnO2–based anodes.