Synthesis And Electrochemical Performance Study Of Tin-Based Chalcogenides Anode Materials For Lithium/Sodium-ion Batteries

Lithium ion batteries?LIBs?are currently the most concerned research hotspot in energy storage field,and meanwhile the most widely used energy storage devices.Anode materials,which serve as the key material for LIBs,play a critical role in overall electrochemical performance of LIBs.Currently,the commercial anode material for LIBs is graphite,which fail to meet the requirement of next-generation high performance LIBs because of the low lithium storage capacity.Sodium ion battery?SIB?,of which the mechanism is similar to that of LIBs,are still hindered by the unsatisfied anode because the traditional graphite cannot be applied in SIBs.Based on above consideration,the research focus is shifted to alloy-type anode,among which tin chalcogenides?SnS₂ and SnS?have been extensively studied in merit of their high theoretical capacity and unique two-dimensional layer structure.However,the large volume change during cycling process lead to the poor cycling performance of SnS₂ and SnS.Hence,this thesis will focus on designing and exploring the effective strategy to improve the cycling performance of SnS₂ and SnS anode materials for Li/Na ion batteries,and thus improve the overall Li/Na ion storage properties of tin chalcogenides anode materials.1.A one-pot calcination method is developed to fabricate SnS/C-CP free-standing electrode for Li ion battery.After calcination process,the low-cost filter paper with high adsorption capacity is converted into carbon paper with three-dimensional conductive network which can boost the charge transfer kinetic.The ultrathin carbon layer is served as protective layer,suppressing the volume change of SnS nanoparticles during cycling process.The SnS/C-CP free-standing anode can deliver a reversible capacity of 696.2 mAh g^-1 at 0.5 A g^-1 after 200 cycles.At high rate(2.0 A g^-1),the SnS/C-CP can deliver reversible capacity of562.3 mAh g^-1.Such excellent electrochemical performance,low cost and simplicity may promote the practical application of SnS/C-CP as free-standing anode for LIBs.2.A novel and efficient strategy to improve the cycling stability of alloy-type anodes for LIBs is explored.SnS₂,served as the most typical alloy-type anode materials,is investigated.By annealing the TiO₂ nanotube at N₂/H₂ atmosphere,the oxygen defects on the surface of TiO₂ are created.PPy encapsulated SnS₂ nanosheets are stabilized on the surface of TiO₂ and the as-synthesized H-TiO₂@SnS₂@PPy anode exhibits unprecedented cycling stability,delivering reversible capacity of 508.7 mAh g^-1 at 2.0 A g^-1 after 2000 cycles with the capacity retention of 89.7%.It has been proven by both experimental results and theoretical calculations that defect-rich TiO₂ has stronger affinity to SnS₂,compared to defect-poor TiO₂,and thus make the electrode structure more stable and effectively extend the cycle life.3.A novel and facile one-pot annealing method is applied to synthesize SnS₂@3DRGO composite anode for SIBs.By modifying the surface of graphene and making it positive charge,the uniform distribution of SnS₂ nanoparticles in 3DRGO network can be achieved after calcination.Benefiting from the three-dimensional conductive network of 3DRGO,the volume variation of SnS₂ can be suppressed.Compared with pure SnS₂ electrode,SnS₂@3DRGO display reversible capacity of 401.1 mAh g^-1,delivering an excellent long cycling performance with a capacity retention rate of 75.4% after 700 cycles at 2 A g^-1.Meanwhile,as for rate ability,the composite deliver high reversible capacity of 608.6,540.9,502.7 and 449.3 mAh g^-1 at 1.0,2.0,3.0 and 5.0 A g^-1,respectively.