Strongly coupled C@SiOx/MoSe2@NMWCNT heterostructures as anodes for Na+ batteries with excellent stability and capacity

Abstract

Silicon and silicon oxide have become the most prospective anode materials, but the volume variations during charging and discharging have greatly hindered their practical applications. Herein, we constructed a highly ordered, dispersed silicon-molybdenum composite, C@SiO_x/MoSe₂@NMWCNT, with a three-layer heterojunction structure. In this approach, molybdenum pentachloride (MoCl₅) reacts with ethylene glycol to form an ethylene glycol-based organomolybdenum complex, which then undergoes a reaction with triphenylchlorosilane, effectively bridging silicon and molybdenum to form an organometallic compound. After in situ selenization and carbonization, the formed SiO_x is dispersed in the framework of MoSe₂ nanoflaps to form a SiO_x/MoSe₂ composite structure. It is then adsorbed onto carbon nanotubes (NMWCNTs) with nitrogen-containing active sites, forming a three-layer heterojunction structure with the outer carbon layer. When used as a sodium-ion battery (SIB) anode, C@SiO_x/MoSe₂@NMWCNT exhibits an initial discharge-specific capacity (1315 mA h g⁻¹ at 0.1 A g⁻¹) and a high capacity of 526 mA h g⁻¹ after 300 cycles at 0.5 A g⁻¹, demonstrating excellent long-cycle stability. When the current density reaches 5 A g⁻¹, the specific capacity remains at 415 mA h g⁻¹ after 1000 cycles and 353 mA h g⁻¹ after 3000 cycles. Even under a high current density of 10 A g⁻¹, the material maintains remarkable cycling stability, delivering a capacity of 177.79 mA h g⁻¹ after 3000 cycles, illustrating the high potential of silicon for use in SIBs.