Influence Of Sb₂SnO₅ Modified Carbon Fibers And LiTaO₃ Modified PP Separator On Lithium Anode

Lithium metal anode is one of the most ideal anodes for the next generation of high energy density secondary batteries due to its high energy density(?3860 m Ah g^-1)and low electrochemical potential(-3.040 V vs.SHE).However,the practical application of lithium metal batteries has been severely hindered by several challenges,such as lithium dendrite growth,unstable solid electrolyte interphase,and volume expansion effects.Considering these problems,two strategies have been proposed to improve the electrochemical performance of lithium metal anode:constucting a"strong bone"(modification of lithium anode)and building a"solid armor"(modification of separator).Firstly,porous carbon fiber/lithium composite anode modified by 3D nano-Sb₂SnO₅(CF/ATO-Li)was designed to construct a"strong bone"for the metal lithium anode.The CF/ATO-Lidemonstrates improved cycling stability and safety of the lithium metal anode.The CF/ATO-Li||Licells show stable cycles with a low overpotential(12 m V)after cycling for 1000 h at 1 m A cm^-2 and 1 m Ah cm^-2.CF/ATO-Li||LFP cells and CF/ATO-Li||NCM811 cells also exhibit significantly improvement in cycle capacity and coulomb efficiency.The mechanism analysis shows that the CF frame,an internally connected three-dimensional conductive sub-network,can homogenize the electric field distribution and reduce the current density;the CF/ATO three-dimensional composite framework can provide enough space for the deposition of lithium and induce the uniform nucleation of Lideposition,thereby inhibiting the growth of lithium dendrites.Secondly,PP separator modified by LiTaO₃(LTO)was prepared to bulid a"solid armor"for the metal lithium anode.The LTO/PP separator,which has good mechanical stability and flexibility,can greatly enhance the electrochemical performance of lithium metal anode.The Li||Cu cells exhibit stable cycles for more than 600 cycles at 1m A cm^-2 and 1 m Ah cm^-2,and for more than 160 cycles at 1 m A cm^-2 and 4 mAh cm^-2.The Li||S cells retain a discharge capacity of 838.5 m Ah g^-1 after 100 cycles even at a high sulfur content of 2.5 mg cm^-2 and low electrolyte of 7 u L mg^-1.Further investigations show that the dehydrogenation and fluorination of LTO and PVDF is favorable to the formation of high-quality SEI film.Moveover,LTO can promote the dissociation of LiTFSI,inhibit the shuttle effect in Li||S cells,and prevent the lithium dendrite growth.Finally,LTO/PP separator improves the stability,safety and dynamic performance of the batteries.The research results of this thesis show that the challenges of lithium metal batteries need to be solved from a systematic perspective.Improving electric field distribution inside anode and enhancing functionality of separator are effective ways to inhibit the lithium dendrite growth,stabilize the SEI layer,and suppress the volume expansion effects.Combined with the facile synthesis,the above studies are expected to promote the practical application of lithium metal batteries.