Lithium Azides Induced SnS Quantum Dots for Ultra-Fast and Long-Term Sodium Storage

Construction of Co9S8@C-MoS2 heterostructure for fast charging and superior long-term cycling performance of sodium ion batteries

Cobalt sulfide (Co9S8) is a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical capacity, cost-effectiveness, and environmental friendliness. Unfortunately, the inevitable structural deterioration induced by the huge volume changes during the discharge/charge cycles leads to poor cycle performance and rate capability when evaluated as the anode material for SIB. Herein, we designed a Co9S8@C-MoS2 heterostructure with abundant heterointerface and hollow structure. In the designed hybrid architecture, the self-supporting hollow carbon scaffold can provide sufficient space for volume expansion caused by Na+ insertion, and the abundant heterointerface can accelerate ion-diffusion and electron transfer kinetics and dissipate the internal stress induced by volume expansion during the sodiation/desodiation process. As expected, the Co9S8@C-MoS2 composite shows excellent sodium storage performance. Specifically, the Co9S8@C-MoS2 composite displays excellent long-term cycling life (a high capacity of 429.4 mAh g-1 is maintained after 1500 cycles at 5.0 A/g), and superior rate performance (412.6 mAh g-1 is achieved even at 10.0 A/g).

Rod-like Ni-CoS2@NC@C: Structural design, heteroatom doping and carbon confinement engineering to synergistically boost sodium storage performance

Currently, conversion-type transition metal sulfides have been extensively favored as the anodes for sodium-ion batteries due to their excellent redox reversibility and high theoretical capacity; however, they generally suffer from large volume expansion and structural instability during repeatedly Na+ de/intercalation. Herein, spatially dual-confined Ni-doped CoS2@NC@C microrods (Ni-CoS2@NC@C) are developed via structural design, heteroatom doping and carbon confinement to boost sodium storage performance of the material. The morphology of one-dimensional-structured microrods effectively enlarges the electrode/electrolyte contact area, while the confinement of dual-carbon layers greatly alleviates the volume change-induced stress, pulverization, agglomeration of the material during charging and discharging. Moreover, the introduction of Ni improves the electrical conductivity of the material by modulating the electronic structure and enlarges the interlayer distance to accelerate Na+ diffusion. Accordingly, the as-prepared Ni-CoS2@NC@C exhibits superb electrochemical properties, delivering the satisfactory cycling performance of 526.6 mA h g-1 after 250 cycles at 1 A g-1, excellent rate performance of 410.9 mA h g-1 at 5 A g-1 and superior long cycling life of 502.5 mA h g-1 after 1,500 cycles at 5 A g-1. This study provides an innovative idea to improve sodium storage performance of conversion-type transition metal sulfides through the comprehensive strategy of structural design, heteroatom doping and carbon confinement.

Interface engineering of metal sulfides-based composites enables high-performance anode materials for sodium-ion batteries

Metal sulfides (MSs) have attracted much attention as anode materials for sodium-ion batteries (SIBs) due to their high sodium storage capacity. However, the unsatisfactory electrochemical performance induced by the huge volume change and sluggish kinetics hampered the practical application of SIBs. Herein, guided by the heterostructure interface engineering, novel multicomponent metal sulfide-based anodes, including SnS, FeS, and Fe3N embedded in N-doped carbon nanosheets (SnS/FeS/Fe3N/NC NSs), have been synthesized for high-performance SIBs. The as-prepared SnS/FeS/Fe3N/NC NSs with abundant heterointerfaces and high conductivity of N-doped carbon nanosheet matrix can shorten the Na+ diffusion path and promote reaction kinetics during the sodiation/desodiation process. Moreover, the presence of Fe3N can promote the reversible conversion of SnS and FeS during the cycling process. As a consequence, when evaluated as anode materials for SIBs, the SnS/FeS/Fe3N/NC NSs can maintain a high sodium storage capacity of 473.6 mAh g-1 after 600 cycles at 2.0 A g-1 and can still provide a high reversible capacity of 537.4 mAh g-1 even at 5.0 A g-1 This discovery offers a novel strategy for constructing metal sulfide-based anode materials for high-performance SIBs.