Construction of CoP/Mn ₂ P Heterojunctions via One‐Step Phosphorization Coupled With Hollow Hard Carbon Spheres as Supports: Enabling Ultrastable Long‐Cycle Sodium‐Ion Anodes Over a Wide Temperature Range

ABSTRACT Driven by global energy transition and sustainability, sodium‐ion batteries (SIBs) have emerged as key alternatives to lithium‐ion batteries for low‐to‐medium energy storage, because of abundant sodium resources and low cost. However, their commercialization is hindered by the lack of anodes with high capacity, fast kinetics, and long‐term stability. In this work, a bimetallic phosphide heterojunction hollow carbon sphere composite (DHC‐CoP/Mn 2 P@HG) was designed and synthesized via multidimensional structural and compositional engineering. A one‐step phosphorization strategy constructed the CoP/Mn 2 P heterojunction, whose interfacial electronic coupling alleviates poor conductivity and severe volume expansion compared to single‐metal phosphides. Hollow hard carbon spheres (HG) buffer volume variation and enable efficient electron transport, whereas dopamine hydrochloride‐derived N‐doped carbon enhances active sites and interfacial adhesion to suppress structural degradation. Electrochemical characterizations show that the DHC‐CoP/Mn 2 P@HG anode delivers a reversible capacity of 232 mAh g −1 after 13,000 cycles at 20 A g −1 (capacity retention ∼95%) and exhibits excellent temperature tolerance (negligible capacity decay after 300 cycles at −30°C or 500 cycles at 50°C). Density functional theory (DFT) calculations reveal interfacial charge rearrangement at the heterojunction, providing theoretical support for performance enhancement. This study establishes a novel paradigm for SIB anodes with wide temperature adaptability and ultralong cycle life, promoting the practical application of SIBs.