Heterojunction and carbon coating dual strategy mechanism: WSe2/NiSe@C nanosheets for efficient sodium storage

Based on the design strategy of heterojunction and carbon coating, a nanosheet structure composed of heterojunction bimetallic selenide and carbon layer (denoted as WSe2/[email protected]) was successfully designed and synthesized. The creation of heterojunctions structure can benefit adjusting the electron structure and accelerate migration rate of ions, which provides the possibility to improve reaction kinetics of sodium storage. In addition, in order to alleviate the matter of material volume pulverization during charging and discharging, a method of carbon coating is proposed to solve the problem. As expected, WSe2/[email protected] showed superior sodium storage property. In the sodium ion half-cell, WSe2/[email protected] delivered sustainable discharge specific capacity (535.2 mAh g−1), outstanding rate performance, prominent initial Coulombic efficiency (78.1%) and excellent cycling capacity (361.3 mAh g−1 after 100 cycles) at 0.5 A g−1. More surprisingly, when the WSe2/[email protected] is applied to the full sodium ion cell, it can maintain 105 mAh g−1 after 200 cycles at 0.5 A g−1, showing remarkable practical application value.