Structure Design And Energy Storage Behavior Of High Specific Capacityas Anode Materials For Lithium-ion Batteries

Lithium ion battery?LIBs?has the advantages of light weight,small volume,high energy density and long service life,and is widely used.However,the current graphene lithium ion battery in circulation in the market cannot meet the needs of people due to its low theoretical capacity?372 mAh/g?.Transition metal sulfide?TMSs?is an important anode material for LIBs with a high theoretical capacity,more than three times that of graphite.In particular,tin disulfide?SnS₂?has a specific capacity of 1231mAh/g,which is the anode material with high energy density output of LIBs.However,in the process of Li⁺embedding/stripping,the volume expansion is caused,and even the electrode powder falls off,resulting in slow motion mechanics of metal sulfide ion transport and reduced conductivity.By adjusting its morphology and structure,and by combining Reduced Graphene Oxide?rGO?and Carbon Nanofibers?CNFs?with SnS₂,high-performance lithium storage materials were prepared.Specific results are as follows:SnS₂ nanometer sheet?NS?,SnS₂ nanometer flower?NF?and SnS₂NF@reduced go graphene?rGO?were synthesized by hydrothermal method.As the cathode material of LIBs for battery assembly test,SnS₂-NF@rGO composite material after 350 cycles,at 0.5 C has a reversible capacity of 525 mAh/g,at 2.0C has a reversible capacity of412.5 mAh/g,significantly improving the Li storage performance of SnS₂NS and SnS₂-NF.Detailed electrochemical impedance spectroscopy?EIS?analysis showed that the internal resistance of SnS₂-NF@rGO nanocomposites was greatly reduced due to the decrease of Warburg coefficient.The conductivity of SnS₂-NF@rGO after circulation is three times that of SnS₂-NS and SnS₂NF.Constant current intermittent titration?GITT?was used to test the diffusion coefficient of lithium ion D_Li+,indicating that the addition of rGO in SnS₂-NF@rGO could enhance the diffusion coefficient of Li⁺.Two-dimensional layered structure rGO can provide good electronic conductivity,and its composite material SnS₂-NF@rGO is more suitable for the anode material of high-performance lithium ion batteries.SnS nanofibers were prepared by sol-gel electrostatic spinning method from hydrothermal SnS₂ nanoflowers.SnS@CNF is directly used as the non-binder negative electrode of LIB,and the specific capacity is 595,465,354,267,200,129,74 and484mAh/g when the current density is 0.064,0.1,0.3,0.6,1.0,1.5,2.0 and 0.1a/g respectively.Such excellent electrochemistry is attributed to the fact that the nano-conductive carbon fiber network can not only buffer volume expansion,prevent the polymerization of active substances,but also improve the mobility of lithium ions(4.47×10^-7 cm²·s^-1),thus improving the electrochemical stability of stann-based sulfide.The above two modification methods can effectively reduce the internal resistance of the battery,increase the cycling stability of the battery,and contribute to effectively improving the lithium storage performance of the cathode material of the lithium ion battery.