Study Of Porous Si-Baced Anode Materials For Lithium-Ion Batteries

Si/C composite has been regarded as a promising material for next generation anode materials with high power density and good electrical conductivity in lithium-ion batteries(LIBs).In recent years,scientific researchers have already conducted a lot of researches on Si/C composite materials,and the research methods have been relatively mature.However,facile and scalable approach to synthesize high-performance Si/C material still remains a huge challenge.In this paper,we are developing a production route that can be scaled up and produced at low cost.Micro-sized continuous porous Si/C(PSi/C)composite materials have been easily fabricated by industrially scalable microemulsion approach and magnesium thermal reduction.The research contents and results are as follows:(1)Si@SiO2 clusters were synthesized from commercial Si and SiO2 nanoparticles,and then amorphous carbon layer was coated on the surface by sol-gel method.Finally,the SiO2 sacrificial layer was etched to synthesize continuous three-dimensional(3D)PSi/C composite.The continuous 3D hollow carbon shells not only improve the electrical conductivity,but also accommodate the significant volume expansion during lithiation/delithiation of Si,leading to high cyclic stability and conductivity of this composite.Thus,the PSi/C composites presented a reversible specific capacity as high as 812.76 mAh g-1 at 1 A g-over 100 cycles with good capacity retention.There is more than 87%of the charge capacity is remained from the 4 th to the 100 th cycle at a rate of 2 A g-1,which shows that the material has excellent rate performance.(2)Nano-sized SiO2 was synthesized with tetraethyl orthosilicate(TEOS)as Si source,and then synthesize SiO2 clusters by microemulsion method.After amorphous carbon layer was coated on the surface,the PSi/C composite was obtained from subsequent magnesium thermal reduction process.Different from the above structure,Si particles and holes in the PSi/C composite are covered by the carbon layer simultaneously,and the holes can effectively buffer the volume expansion of Si during cycling.The interconnected carbon shell and porous structure provide suitable path for the transport of Li+,allowing the anode to maintain a capacity retention of more than 65%from the 4 th to the 100 th cycle at a current density of 1 A g-1,indicating that it has better cycling stability.