Preparation And Electrochemical Performance Of Spherical Hollow Carbon And Spherical Silicon/Carbon As Anode For High-performance Lithium Ion Batteries

At present,the relatively low energy density and poor rate performance of commercial lithium ion batteries?LIBs?,makes it no longer meet the requirements of a series of high and new electronic equipment in power requirement.The emergences of new energy vehicles greatly promote the development of a new generation of LIBs with high performance.These high-performance LIBs generally have a higher capacity,good performance and long cycle capacity,which can improve the endurance ability for new energy vehicles.Macroporous mesoporous hollow carbon spheres?MMHCSs?with high specific surface area(396 m² g^-1)was successfully prepared by silica template method.The macropore can shorten the diffusion distance of Li⁺in electrode and reduce the concentration polarization during the reaction.The mesoporous not only can improve the effective contact area between electrolyte and active material,but also improve the electrochemical activity of the electrode reaction.In addition,the low graphitization of carbon materials prepared by organics pyrolysis at high temperature method,having a lot of microporous which can provides more space for Li⁺insertion.The initial discharge capacity of MMHCSs is 1650 mAh g^-1 and the reversible capacity is 500 after 20 cycles and the retention capacity is 96%after 400 cycles.MMHCSs electrode also can stably output the reversible capacity of 180 mAh g^-1 even at a current density of 60 A g^-1.Silicon/carbon nanotube hollow sphere composites?Si/CNCs?are prepared by water-in-oil emulsion technique with 75 wt.%loading amount of silicon.CNCs with unique hollow sphere structure as a 3D interconnected conductive network skeleton,and characteristic of cross-linked carbon nanotubes?CNTs?can improve the flexibility,strength and conductivity of the electrode.On the other hand,Si/CNCs can not only alleviate the volume expansion of the Si during the charge/discharge process,but also effectively improve the electrochemical activity.Such Si/CNCs electrode with the unique structure achieves a high initial discharge specific capacity of 2950 mAh g^-1 and maintains of reversible capacity of 1226 mAh g^-1 over 100 cycles at the current density of 0.5 A g^-1,as well as outstanding rate performance of 547 mAh g^-1 at 10 A g^-1.