Pre-intercalated Sodium Ions Enhance Sodium Storage of MoS₂ Anode by Mitigating Structural Dissociation

Molybdenum disulfide (MoS₂) is a promising anode for sodium-ion batteries (SIBs) due to its high theoretical capacity and layered structure. However, a poor reversible conversion reaction and a low initial Coulombic efficiency (ICE) limit its practical application. This study systematically investigated the potential of pre-intercalated sodium ions molybdenum disulfide (Na-MoS₂) as an anode material for SIBs. Because of the mitigation of MoS₂ structural dissociation and effective replenishment of active sodium ions, Na-MoS₂ delivered an outstanding capacity of 507.7 mAh g^-1 after 2000 cycles at 5 A g^-1, along with an ICE of 95.30%. Pre-intercalating sodium ions can expand interlayer spacing and modulate electronic structure, allowing Na-MoS₂ to have greater tolerance to the electrochemical intercalation/extraction process. Furthermore, the conversion reaction of Na-MoS₂ has a higher Gibbs free energy, implying its structural dissociation is thermodynamically unfavorable. This work provides a new perspective on the study of transition metal dichalcogenide electrode materials for SIBs.