A high-pressure enabled high-entropy (CrFeCoNiMn)4S5 composite anode for enhanced durability and high-rate sodium-ion batteries†

Abstract

Transition metal sulfides (TMS) have gained attention as promising anode materials for sodium-ion batteries (SIBs) due to their low cost and high theoretical capacity. However, their cycling stability is often compromised by the sodium polysulfide (NaPS) shuttle effect. In this study, we synthesize metal sulfides with a new monoclinic structure, including Cr₄S₅ (CS), (CrFeNi)₄S₅ (CFNS), and high-entropy (CrFeCoNiMn)₄S₅ (HES), using a high-pressure, high-temperature (HPHT) technique. These sulfides are then combined with carbon nano-onions (CNOs) through high-energy mechanical milling to form the composite HES@CNOs. The HES@CNOs composite demonstrates exceptional fast-charging performance and cycling stability, achieving a specific capacity of 352.2 mA h g⁻¹ and retaining over 82.1% after 3800 cycles at 10 A g⁻¹. This performance surpasses that of conventional sulfide-based anodes. The enhanced properties are attributed to the specific high-entropy structure, which promotes efficient sodium ion diffusion and improves the electronic conductivity. Additionally, optimizing the cut-off voltage to 0.3 V mitigates the NaPS shuttle effect, resulting in improved capacity retention and cycling stability. Structural analyses show minimal degradation, further confirming the reversible nature of sodium storage within the HES@CNOs composite. The present work highlights the potential of high-entropy materials to enhance the SIB performance and offers a strategy to address common challenges in metal-ion batteries.