Ni-Co Alloy Hollow Nanoprisms Prepared By Electro Spinning And Its Lithium Storage Performance

The development of high-energy-density,low-cost,and safe energy storage devices is an attractive topic in modern society,which could completely change the way of life of mankind.Because of its extremely high theoretical specific capacity and extremely low redox potential,metallic lithium(Li)is regarded as the best choice for the next generation of high-performance anode materials.However,the dendrites produced by the uncontrollable deposition of the lithium negative electrode during the charge-discharge cycle pose a threat to the safety of the battery.In addition,the huge volume changes caused by Li plating/stripping lead to the production of dead Li,which finally reduce the cycle life.Carbon-based materials have attracted much attention as host materials to guide the deposition of lithium metal and inhibit the growth of lithium dendrites due to their low density,high surface area,high conductivity,and adjustable characteristics.However,the integral structures of carbon host need further optimization to modify the interface properties at the micro/nano scale.In this thesis,three carbon-based materials are prepared based on electrospinning technology as host materials for non-dendritic lithium metal anodes,and the metal lithium plating morphology are characterized and the electrochemical performances are compared.The specific contents are as follows:(1)Polyacrylonitrile(PAN)based three-dimensional carbon skeleton materials(CF)were prepared by electrospinning and the following two-stage high temperature annealing.After the introduction of nickel-cobalt bimetallic particles to act as nucleation sites,and finally obtains three-dimensional Ni-Co based carbon fiber materials(NC@CF)and the morphology characterizations and electrochemical properties of the above two materials were tested before and after lithium metal plating/stripping,the electrode materials modified by doping of lithiophilic groups achieved long cycles up to 200 h with low voltage hysteresis,and showed 90%high capacity retention after 120 cycles with LiFePO4 cathode.(2)The nickel-cobalt acetate hydroxide prepared by modified precipitation reaction was selected as precursors.The electrospinning process and two-stage high-temperature annealing treatments were used to prepare a hierarchical hollow fiber with a lotus root-like porous structure,namely Ni-Co hollow nanoprisms/carbon fibers materials(NCH@CF).By combining the hollow structure design with lithiophilic interface components,it enables a very stable Li metal anode with a low voltage hysteresis during repeated Li plating/stripping for 1200 h at the current density of 1 mA cm-2 and a stable cycle life for 150 cycles with a remarkable capacity retention of 90%with LiFePO4 cathode.