Leaf-inspired design of mesoporous Sb_(2)S_(3)/N-doped Ti_(3)C_(2)T_(x) composite towards fast sodium storage

Owing to excellent conductivity and abundant surface terminals,MXene-based heterostructures have been intensively investigated as energy storage materials.However,elaborate design of the structure and composition of MXene-based hybrids towards superior electrochemical performance is still challenging.Herein,we present an ingenious leaf-inspired design for preparing a unique Sb_(2)S_(3)/nitrogen-doped Ti_(3)C_(2)T_(x)MXene(L-Sb_(2)S_(3)/Ti_(3)C_(2))hybrid.In-situ TEM observations reveal that the leaflike Sb_(2)S_(3)nanoparticles with numerous mesopores can well relieve the large volume changes via an inward pore filling mechanism with only 20%outward expansion,whereas highly conductive N-doped Ti_(3)C_(2)T_(x)nanosheets can serve as the robust mechanical support to reinforce the structural integrity of the hybrid.Benefiting from the structural and constituent merits,the L-Sb_(2)S_(3)/Ti_(3)C_(2)anode fabricated exhibits a fast sodium storage behavior in terms of outstanding rate capability(339.5 mA h g^(-1)at 2,000 mA g^(-1))and high reversible capacity at high current density(358.2 mA h g^(-1)at 1,000 mA g^(-1)after 100 cycles).Electrochemical kinetic tests and theoretical simulation further manifest that the boosted electrochemical performance mainly arises from such a unique leaf-like Sb_(2)S_(3)mesoporous nanostructure with abundant active sites,and enhanced Na^(+)adsorption energy on the heterojunction formed between Sb_(2)S_(3)nanoparticles and Ti_(3)C_2)matrix.

In-situ conversion growth of carbon-coated MoS_(2)/N-doped carbon nanotubes as anodes with superior capacity retention for sodium-ion batteries

Layered structure MoS_(2) nanosheets have shown great potential for energy storage applications.However,the methodology for elaborately controllable growth of MoS_(2) onto carbonaceous matrix for promoting the electrochemical performance is highly desirable.Herein,a high-effective,all-in-one in-situ conversion growth strategy has been proposed to construct a stable sandwich-type nanostructure.The formation of the optimized C-MoS_(2)/NCNTs product undergoes a dissolution-recrystallization process,in which ultra-thin carbon layer-coated MoS_(2) nanosheets densely assembled onto the surface of polyimide(PI)derived N-doped carbon nanotubes(CNTs).Theoretical simulation reveals that MoS_(2) nanosheets possessing an expanded interlayer spacing of 0.92 nm can greatly reduce the barrier energy of Na ions mitigation.Ac-cordingly,the as-made C-MoS_(2)/NCNTs anode delivers superior cycling stability(82%capacity retention after 400 cycles at 1 A g^(−1))and rate performance(348 mAh g^(−1) at 2 A g^(−1)).The results demonstrate that the expanded MoS_(2) interlayer distance,ultrathin outer carbon coating,and N-doped CNTs matrix together accounts for the outstanding sodium storage capability for the C-MoS_(2)/NCNTs electrode.