Robust S-doped TiO_(2)@N,S-codoped carbon nanotube arrays as free-binder anodes for efficient sodium storage

Titanium dioxide(TiO_2) has been investigated broadly as a stable,safe,and cheap anode material for sodium-ion batteries in recent years.However,the poor electronic conductivity and inherent sluggish sodium ion diffusion hinder its practical applications.Herein,a self-template and in situ vulcanization strategy is developed to synthesize self-supported hybrid nanotube arrays composed of nitrogen/sulfur-codoped carbon coated sulfur-doped TiO_2 nanotubes(S-TiO_2@NS-C) starting from H_2 Ti_2 O_5-H_2 O nanoarrays.The S-TiO_2@NS-C composite with one-dimensional nano-sized subunits integrates several merits.Specifically,sulfur doping strongly improves the Na~+ storage ability of TiO_2@C-N nanotubes by narrowing the bandgap of original TiO_2.Originating from the nanoarrays structures built from hollow nanotubes,carbon layer and sulfur doping,the sluggish Na~+ insertion/extraction kinetics is effectively improved and the volume variation of the electrode material is significantly alleviated.As a result,the S-TiO_2@NS-C nanoarrays present efficient sodium storage properties.The greatly improved sodium storage performances of S-TiO_2@NS-C nanoarrays confirm the importance of rational engineering and synthesis of hollow array architectures with higher complexity.

Heterostructure of 2D MoSe_(2) nanosheets vertically grown on bowllike carbon for high-performance sodium storage

Transition metal dichalcogenides are attractive anode materials for sodium ion batteries(SIBs)due to their high theoretical capacity and large interlayer spacing.However,its practical application is hampered by the sluggish kinetics of Na^(+)insertion and structure collapse caused by Na^(+)insertion/deinsertion.Herein,the heterostructures of MoSe_(2) nanosheets vertically growing on bowl-like carbon(MoSe_(2)@C)are designed and prepared by a template method coupled with selenization treatment to boost storage sodium performance.The hollow and collapse could provide enough storage space for Na^(+)and alleviate the volume expansion during the charge/discharge processes.MoSe_(2) nanosheets vertically grown on carbon could expose more active sites for adsorbing Na^(+)to enhance the utilization rate of electrode materials.Moreover,building heterostructures by combining different phase components could facilitate Na^(+)diffusion and advance reaction kinetics.Benefiting from these merits,the bowl-like MoSe_(2)@C shows outstanding reversible capacity(356.8 mAh·g^(-1) after 1500 cycles at 1 A·g^(-1))and remarkable rate performance(249.9 mAh·g^(-1)10 A·g^(-1)).

MoSe_(2)/TiO_(2)heterostructure integrated in N-doped carbon nanosheets assembled porous core-shell microspheres for enhanced sodium storage

Engineering the structure and composition of electrode materials is one of the essential means for achieving excellent electrochemical performance.The rational design of Na+host materials is still a massive challenge for sodium ion batteries(SIBs).Herein,MoSe_(2)/TiO_(2)heterostructure is integrated with N-doped carbon nanosheets to assemble into hierarchical flowerlike porous core-shell microspheres(MoSe_(2)/TiO_(2)@N-C),which is firstly reported by room-temperature stirring coupled with vulcanization treatment.The cavity of the core-shell structure could provide enough storage space for Na+and alleviate the volume expansion during charge/discharge processes.The apertures between nanosheets provide a guarantee for the rapid penetration of electrolyte to enhance the utilization rate of electrode materials.Furthermore,building heterostructures by combining different phase structures can facilitate electron transfer and accelerate reaction kinetics.Benefiting from the synergistic contributions of structure and composition,MoSe_(2)/TiO_(2)@N-C as SIBs anode material shows better reversible capacities of 302.5 mAh·g^(-1)at 1 A·g^(-1)for 400 cycles and 217.4 mAh·g^(-1)at 4 A·g^(-1)for 900 cycles.Strikingly,the reversible capacities can be restored entirely to the initial level after a high current density cycle.