Design And Synthesis Of 3D Carborn Composited With Nanomaterials As Anode For Lithium Ion Batteries

Li-ion batteries have been widely used due to their good cyclic stability,high energy density,low memory effect,low self-discharge rate and ecoenvironmental properties.Currently,the main commercial anode materials are graphite materials.However,graphite materials have a low theoretical capacity(372 m Ah g^-1),which can't meet the demand of electric vehicles and hybrid electric vehicles.Therefore,it is very important to develop lithium ion batteries which have higher specific capacity and excellent cyclic stability.Recently,Germanium and tin have drawn much attention due to their high theoretical specific capacity(1600 m Ah g^-1 of Ge,933 m Ah g^-1 of Sn).but they suffer from rapid capacity fading because of large volume expansion occuring during cycling process.Therefore,it is necessary to design and synthesize materials with new stuctures to obtain anode materials.Based on the former research,in this paper,Na₂Ge₄O₉ nanoparticles encapsulated in 3D carbon networks and Flower-like SnS₂ composite with 3D bacterial cellulose materials were designed and synthesized.Thanks for the 3D carbon networks can offer more space to relief volume expansion,the as-prepared composites show better cyclic stability and rate capability:1.The composite of Na₂Ge₄O₉ nanoparticles encapsulated in 3D carbon networks was synthesized successfully in a Na Cl-templated method.The unique 3D interconnected carbon networks and sodium in Na₂Ge₄O₉ effectively buffer volume expansion and prevent the aggregation of active materials.Furthermore,the thin carbon networks?3-4 nm in thickness?can improve the conductivity of anodes and enhance the diffusion of Li+.Thus,the obtained material showed high specific capacity of ⁸00 m Ahg^-1 in the range of 0.2-1 A g^-1 and a retention of 81.2 % after 1000 cycles.And it still kept a specific capacity of ⁵00 m Ah g^-1 even at 20 A g^-1.Bacterial cellulose,a biomass material,have been reported can be calcinated to obtain 3D carbon structure,and the as-prepared material shows excellent electricity.In this paper,a flower-like SnS₂ composite with 3D bacterial cellulose composite was synthesized in a simple hydrothermal method.The composite displayed high specific capacity and a retention of 92 % after 1500 cycles even at ultra-high current density of 10 A g^-1 and 20 A g^-1.The enhanced electrochemical performance can attribute to the synergistic effect of the 3D carbon structure and the unique SnS₂ nanosheets,which offered new ways to commercial anode materials for lithium ion batteries.