Application Of Carbon-based Composites In Lithium Batteries

In new type of electrode materials,lithium metal as an ideal anode materials because of low oxidation reduction potential(-3.04 V vs.standard hydrogen electrode potential)and ultra-high theoretical specific capacity(3860 m Ah/g),elemental sulfur as an ideal cathode material due to high theoretical energy density of(2600 Wh/kg)and high theoretical specific capacity of sulfur(1675 m Ah/g).However,the problems of lithium dendrites and the shuttle effect have hampered the development of lithium-metal batteries and lithium-sulfur(Li-S)batteries.In order to inhibit the growth of lithium dendrites,a bacterial cellulose@graphene(BC@GE)composite anode was fabricated by in situ method,its abundant nitrogen functional groups provide lithiumphilic sites,large specific surface area disperses the current density,and the strong three-dimensional skeleton eases volume expansion during cycling.Besides,the porous traits and high conductive GE sheets promote the rapid transportation of electrons and ions.Therefore,the cells present a higher Coulombic efficiency of 97.1%after 800 cycles,and the resultant Li Fe PO₄ full battery exhibits a high specific capacity of 111 m Ah/g after 1100 cycles.To solve the problem of shuttle effect,a polysulfide trapping interlayer was prepared by coating a nature polymer of konjac glucomannan(KGM)on carbon nanofiber(CNF)using a simple polymer coating meathod.XPS analysis and visualization experiments have proved that the oxygen-containing functional groups of KGM can adsorb polysulfide.The polymer coating quality was improved by modyfing the solvent for KGM.Finalliy,the battery with mixed-solvent based KGM@CNF interlayer presents the best cycling performance with a high specific capacity of 698m Ah/g over 400 cycles.Based on this,we further taken another measure of using the BC@GE anode with 8 m Ah/cm² Li instead of conventional traditional lithium metal anode.By the double optimization of cathode and anode,the Li-S battery simultaneously realizes the purpose of inhibiting lithium dendrites and retarding the polysulfide shuttle effect.