Red Phosphorus@SnSe 0.5 S 0.5 Core‐Shell Heterostructure Enables Superior Sodium Storage via Synergistic Ion Diffusion and Polyphosphides Trapping

Abstract Red phosphorus (RP) has emerged as a highly promising anode material for sodium‐ion batteries (SIBs), mainly due to its affordability, remarkable theoretical specific capacity (≈2600 mAh g⁻¹), and relatively low sodiation voltage (≈0.4 V versus Na/Na⁺). However, the widespread application of RP is severely limited by several inherent drawbacks, including its poor electronic conductivity, dissolution of polyphosphides during cycling, and substantial volumetric expansion that occurs upon sodiation. To address these challenges, a novel core‐shell heterostructure of RP@SnSe 0.5 S 0.5 is developed and anchored onto 3D N‐doped graphene (3DNG) layer using a simple solvothermal synthesis method. Both experimental results and first‐principles calculations demonstrate that the improved electrochemical performance can be primarily attributed to the increased ion diffusion facilitated by the heterostructure interface and the strong chemical interaction with polyphosphides, which stabilize the RP during cycling. The RP@SnSe 0.5 S 0.5 /3DNG exhibits a high‐rate capacity of 492.7 mAh g⁻¹ at 10 A g⁻¹, and it maintains a remarkable 96.9% of its initial capacity after 1500 cycles, showcasing its unprecedented cycling stability. This study highlights the potential of tailoring advanced heterostructures and support matrices for designing high‐performance P‐based anode materials in SIBs applications.