Biomass Derived Carbon/MoS₂ Composite As Anode Material For Sodium Ion Batteries

Lithium ion batteries（LIBs）have been widely used in our daily life.However,considering the scarcity of lithium resource,it might not meet the increasing demands on LIBs.Therefore,sodium-ion batteries（SIBs）have developed as a potential alternative to LIBs,especially for future energy storage in light of the abundant resource and low cost of Na ion.Unfortunately,the most popular anode in LIBs,graphite,delivers a low theoretical capacity for SIBs resulting from the large ionic radius of sodium.Therefore,exploring advanced material with high capacity and long term cycling performance for sodium ion batteries has attracted remarkable interest in researchers.On the other hand,the two-dimensional transition metal dichalcogenides MoS₂ has a larger d-space of layered structure（6.2?）than that of graphite（3.35?）,which has attracted widespread attention in recent years.However,the two-dimensional transition metal dichalcogenides MoS₂ usually delivers poor cycling stability and inferior rate capabilities due to the low conductivity of sulfides,large volume change and sluggish kinetics,which impels us to design novel high performance MoS₂ based anode material.Renewable biomass served as an environmentally friendly carbonaceous precursor can be applied to energy storage application,which has been extensively researched recently.In this dissertation,the MoS₂/C composites with different structure and characteristic are developed by using sodium lignosulfonate and natural chlorella as porogen and obsorb.The main contents of the research works include the following three aspects:Firstly,the sodium lignosulfonate was used for synthesizing HPCF via an electrospinning technique.And then the ultra-small few-layer MoS₂ nanostructure confined on hierarchical porous carbon fiber composite（FM-HPCF）was synthesized through nanocasting route by using novel hierarchical porous carbon fiber as a nanoreactor.When used as anode for SIBs,the FM-HPCF delivers an outstanding long-term cycling stability(211 mAh g^-1 at 1 A g^-1 after 3000 cycles).Secondly,a sustainable and easily method for the fabrication of few-layer MoS₂combined on N,P co-doped bio-carbon is developed by using natural chlorella as obsorb and carbon precursor for sodium ion batteries.Few-layer MoS₂-N/P-carbon composite is facilely synthesized by the biosorption of chlorella and a subsequent calcination process.This bio-carbon made from chlorella can act as a nanoreactor to prevent the MoS₂nanoparticles from reuniting during the calcination process.Besides,the N,P co-doped bio-carbon enhances the conductivity of this composite.When used as anode for sodium ion batteries,it shows high rate capability and outstanding long cycling performance(175mAh g^-1 after 2000 cycles at 5 A g^-1).Finally,based on the synthesis of MoS₂-N/P-C,the 1T-MoS₂ can be induced when the tin introduced into the lattice of 2H-MoS₂.It can find that the increasing contents of1T-MoS₂ is increased with the doping contents of tin and the introducing superabundant Sn doped in 2H-MoS₂ will led to the formation of SnS.Electrochemical performance test results show that the TH-MoS₂-2 sample exhibited the best electrochemical performance when the Sn doping amount is 20%.TH-MoS₂-2 showed high reversible capacities of647 and 167 mAh g^-1 at current density of 0.05 and 15 A g^-1,respectively.The super high rate performance is mainly result from the rich grain boundaries between few-layer structure of 1T-2H-MoS₂ and the N/P co-doping bio-cabron.