Stabilized Solid Electrolyte Interphase Layer Enabled by a Phosphorus-Containing Surface Complex on ZIF-8 for Fast-Charging Lithium-Ion Batteries

ZIF-8-derived hard carbon materials exhibit a significant advantage in lithium-ion batteries as anodes, characterized by their high theoretical specific capacity. However, their practical application is limited by issues such as rapid capacity fade and poor cycle stability, primarily due to the instability of the solid electrolyte interphase layer. In this study, using ZIF-8 as a precursor, we constructed a phosphorus-containing surface complex on hard carbon via a sulfur-bridged method. This functionalized surface acts as a robust template to chemically regulate the in situ formation of a crystalline Li3P-rich solid electrolyte interphase during the initial lithiation. The highly conductive Li3P phase significantly lowers the energy barrier for Li+ desolvation and accelerates interfacial transport kinetics, which we identify as the mechanistic origin of the enhanced fast-charging capability. The modified hard carbon exhibited an outstanding electrochemical performance: in half-cell tests, the material delivered a discharge capacity of 403.3 mAh/g and 70.2% initial Coulomb efficiency at 1 A/g with negligible capacity loss over 400 cycles, and at 3 A/g, it retained 76.9% of its capacity after 1000 cycles, both significantly superior to conventional graphite and unmodified hard carbon. In full-cell tests, the assembled LiNi0.8Co0.1Mn0.1O2//HC-S-P5 full cells maintained an 80% capacity retention after 1400 cycles at 5C. In-depth characterizations, including in situ Raman, X-ray photoelectron spectroscopy, and theoretical calculations, revealed that the enhanced performance is attributed to the formation of a stable SEI layer on the surface of the hard carbon, which effectively suppresses interfacial side reactions and improves Li+ diffusion kinetics and overall cycle stability. This work demonstrates an approach to the design and application of hard carbon materials in high-energy lithium-ion batteries, as well as potential extensions to sodium-ion batteries and high-rate secondary batteries.