Efficient stress alleviation and interface regulation in Cu₄SiP₈-CNT hybrid for ultra-durable Li and Na storage

In the search for new anode materials having a high theoretical capacity, satisfactory redox potentials, and inexpensive, abundant components for use in high-performance metal-ion batteries, ternary copper phosphosilicide (Cu₄SiP₈) is herein explored for the first time as a highly promising anode electrode material for Li-ion and Na-ion batteries (LIBs and NIBs). In a hybrid architecture with a defective carbon network, the nanoparticles can be fully embedded and robust chemical bonds permanently constructed, thus firmly protecting the integrity of the electrode against dramatic changes in volume, boosting electron/ion transport, and regulating the reaction pathways. Specifically, these work to inhibit the formation of undesirable LiP and crystalline Li_3.75Si phases in LIBs, promote the stable reaction of Si with Na⁺ in NIBs, and guarantee the reversible regeneration of Cu₄SiP₈ during recharging. Thus, the electrode delivered a first discharge capacity of 1764 mA h g⁻¹ (Coulombic efficiency; CE: 92.29%) at 0.1 A g⁻¹ and demonstrated superb capacity retention at 5 A g⁻¹ for 1200 cycles in an LIB. In an NIB, the hybrid electrode exhibited a high first discharge capacity and CE (796 mA h g⁻¹ and 81.78% at 0.1 A g⁻¹), outstanding cyclic stability (>700 cycles, >75% retention), and exceptional rate capability under symmetric/asymmetric conditions.