Anchoring Atomic Phosphorus in a Mixed Occupancy Cu─S Framework for Ultra‐Stable and High‐Rate Sodium Storage

Phosphorus (P) possesses an ultrahigh theoretical capacity of 2596 mAh g^-1, making it the most promising anode material for sodium-ion batteries. However, Na⁺ storage in P anodes encounters considerable technical challenges, such as low conductivity, substantial volume expansion, and poor reaction kinetics. Herein, a novel strategy was proposed that embedding P into a conductive and rigid Cu─S framework to fabricate a novel anode CuPS₂ with Cu and P atoms in occupancy at the same lattice site with a 50% probability each, achieving ultra-stable and high-rate Na⁺ storage. In situ and ex situ analyses reveal the multi-step reversible reaction processes during the charging (formation of CuPS₂) and discharging (precipitation of molecular-level dispersed NaP in the ionic/electronic-conductive (Na₃₊ _x)CuS₂ matrix) processes. The rigid and conductive (Na₃₊ _x)CuS₂ matrix maintains the phase consistency and structural stability of the anode, suppresses the migration and aggregation of intermediate products during Na⁺ storage process, and improves the reaction kinetics of Na⁺ storage. Consequently, the rationally designed CuPS₂ anode with Cu and P mixed occupancy achieves a high capacity of 583.8 mAh g^-1 at 0.2 A g^-1 and an ultra-stable and high-rate Na⁺ storage capability (370 mAh g^-1 at 5 A g^-1 after 11 000 cycles with 90% capacity retention).