Fabrication And Electrochemical Performance Of MnS-Carbon Composites As Anode For Lithium/Sodium Ion Batteries

Due to high output voltage,little self discharge,long calendar life,safety,and so forth,lithium-ion battery(LIB)has dominated the battery market for portable electronics and electric vehicles and is seeking a participant opportunity in the large-scale energy storage systems market.The LIB with high energy density and large output power is ever-increasing demanded due to the large using of electrical vehicles.There has been a growing concern regarding the sustainability and the cost increase of LIB due to the low abundance of Li in the earth's crust.Sodium-ion battery(SIB)is considered as one of the most promising energy storage devices for large-scale energy storage systems owing to the natural abundance of sodium resource,low cost,and basically similar components and working mechanisms to LIB.As an important component,electrode materials play a crucial role in the performance of LIB/SIB.Therefore,it is critical to developing electrode materials with optimal electrochemical performance and low cost for the developing of LIB/SIB.With high theoretical capacity of 616 m Ah g^-1,environmental friendliness,earth abundance,and low cost,MnS is considered to be one of the promising anode materials for LIB/SIB.However,the low electrical conductivity and large volume change of MnS limit its applications in LIB/SIB.Designing nanostructure and carbon hybridization can effectively improve the electrochemical performance for MnS as anode material for LIB/SIB.The work mainly focuses on the combination between MnS with special nanostructure and different carbon materials in this article,and effectively enhances the capacity and cycling stability.Details are as following:First,the carbon coated MnS composites were synthesized with different carbon sources.The electrical conductivity and electrochemical performance,to a certain extent,are improved.At the current density of 200 m A g^-1,the reversible specific capacities of MnS/C composites remain 120 m Ah g^-1(L-cysteine)and 164 m Ah g^-1(glucose)after 50 cycles,whereas the reversible specific capacity of pure MnS is only67 m Ah g^-1.However,compared to the high theoretical capacity of MnS,we should put more effort.Second,we synthesized MnS/CNTs composites by one-step solvothermal method with different weight ratios of MnS to CNTs.When the weight ratio of MnS to CNTs is 2:1,the MnS microspheres homogeneously disperse in the 3D interlaced CNTs network,meanwhile,the CNTs make the independent MnS microspheres interconnect with each other and form an integrative and uniform conductive network.And the MnS/CNTs(2:1)composite exhibits good cycling stability at the current density of1000 m A g^-1,the storage lithium capacity can remain 602 m Ah g^-1 after 1000 cycles.The excellent electrochemical performance can be ascribed to the synergistic effect between the MnS hollow microspheres and the 3D CNTs network:the hollow structure can effectively facilitate the diffusion of Na⁺and improve the contact area between the electrode and electrolyte,and the 3D CNTs network can effectively enhance electrical conductivity,shorten ion diffusion distance,accommodate the volume change,and keep the integrity of electrode.Third,we also tested MnS/CNTs composites electrodes'performance in SIB.As above,MnS/CNTs composite exhibits better electrochemical performance with the weight ratio 2:1 of MnS to CNTs.After 100 cycles,the MnS/CNTs(2:1)electrode remains a reversible specific capacity of 275 m Ah g^-1 at the current density of 100 m A g^-1.With improved rate performance,the MnS/CNTs(2:1)electrode can deliver 190m Ah g^-1 and 170 m Ah g^-1 specific capacities at the current densities of 800 m A g^-1and1000 m A g^-1,respectively.