Carbon dots confined nanosheets assembled NiCO_(2)S_(4)@CDs cross-stacked architecture for enhanced sodium ion storage

Na^(+)batteries(SIBs)have been emerging as the most promising candidate for the next generation of secondary batteries.However,the development of high-performance and cost-effective anode materials is urgently needed for the large-scale applications of SIBs.In this study,carbon dots confined bimetallic sulfide(NiCO_(2)S_(4))architecture(NiCO_(2)S_(4)@CDs)was proposed and synthesized from assembling nanosheets into cross-stacked superstructure and the subsequent confinement of carbon dots.This novel decussated structure assembly from nanosheets is greatly beneficial to the structure stability of electrode material during the successive charge/discharge processes.Besides,the CDs based carbon conductive network can enhance the electrical conductivity for facilitating the easy transport of electron/Na^(+).Benefitting from these advantages,NiCO_(2)S_(4)@CDs exhibits high-rate performance and an ultralong cycling life in SIBs.Specifically,the specific capacity of NiCO_(2)S_(4)@CDs can reach the discharge specific capacity as high as 568.9 mAh/g at 0.5 A/g,which can also maintain 302.7 m Ah/g after 750 cycles at 5.0 A/g.Additionally,ex-situ characterization techniques such as ex-situ XRD and ex-situ XPS were employed to further explore the sodium storage mechanism of the NiCO_(2)S_(4)@CDs anode.