One Dimensional Porous Carbon And Si/C Anode Materials For Lithium Ion Batteries

Since the LIBs have been widely used in the field of demanding higher energydensity and higher power density, including various types of electrical vehicles (EVs)and energy storage for utility grids, there is a harsh demand on advanced LIBs withhigher energy density, higher power density, longer cycle life, higher safety and lowercost. To solve these problems, the one of critical factors is research and development ofanode materials with higher performance. In this work, we have studied the mostpromising anode materials of carbon and non-carbon based anode materials forone-dimensional porous carbon anodes and one-dimensional Si/C anodes respectively.Furthermore, we have improved not only their electrochemical properties through theway of transformation of carbon precursor, nitrogen-doping and micro-structural design,but also revealed the reasons and internal mechanisms of the promoted electrochemicalperformance.In this work, self-standing PI-derived one-dimensional porous carbon anodes werefirstly prepared by electrospining polyimide (PI) and in-situ generated sacrificial SiO2nanoparticles, along with the subsequent carbonization and post-etching. Comparedwith the polyacrylonitrile (PAN)-derived one-dimensional porous carbon anodes,PI-derived one-dimensional porous carbon anodes exhibited a higher specific surfacearea, well-developed microporous structure and superior electrochemical performance.And the outstanding electrochemical performance can be rationalized by the uniqueporous and higher specific surface area of PI-derived one-dimensional porous carbonanodes.Chemical doping of carbon materials with heteroatoms, such as nitrogen is anefficient way to tailor their chemical properties and improve their electrochemicalperformance. Self-standing one-dimensional nitrogen-doped porous carbon anodes weresuccessfully prepared by using incorporation of melamine and PAN via electrospinningfollowed by carbonization and activation. And we have also investigated the structureand electrochemical performance of one-dimensional nitrogen-doped porous carbonanodes influenced by diverse nitrogen-doping level and various activation processes. Itis found that the one-dimensional nitrogen-doped porous carbon anodes prepared byNH3treatments exhibited good nanofibrous morphology, relatively high-level nitrogen doping and well-developed microporous structure. Furthermore, as free-standing newanode materials in lithium-ion batteries (LIBs), they showed ultrahigh capacity of1323mAh g-1, which was higher than that of most other reported carbon-based anodematerials. The superior electrochemical performance can be ascribed to their uniquemicroporous structure, relatively high-level of nitrogen doping, one-dimensionalnanostructure and great amount of pyridinic nitrogen.Silicon possesses the highest theoretical capacity of4200mAh g-1. However, thepractical applications of it were restricted by its poor cycling stability, which resultedfrom the large volumetric expansion (～400%) of silicon anodes upon thecharge-discharge process. In this study, self-standing one-dimensional Si/C anodes withample space around the Si nanoparticles were easy, low-costly and safely synthesizedby using electrospining, dip-coating and along with the subsequent solidification andcarbonization. The structure, Si and C content of Si/C anodes can be effectively tuned toget superior electrochemical performance by merely varying the concentration of dipsolution.