Study On Preparation And Electrochemical Performance Of NiO-based Nanocomposites

Anode materials with high energy density and good rate capability are the key to improve overall performance of lithium-ion batteries.The theoretical capacity of graphite is only 372 mAhg-1.With the growing needs,to find a new generation of anode material is very important.Theoretical capacity of NiO is 718 mAhg-1,which is twice than that of commercial graphite,with high abundance and good chemical stability.However,NiO will produce 950%volume expansion during charging/discharging,low electrical conductivity,slow reaction kinetics and poor cycle stability hinder the commercialization.The porous nano-NiO can relieve volume expansion and shorten the Li+ transmission distance.In this paper,porous nano-NiO and its composite materials are prepared by a simple and cheap synthesis method,and its microstructure and electrochemical properties are studied.The electrochemical performance of acid-etching porous nano-NiO prepared by hydrothermal reaction is better than that of unetched NiO.By XRD,TEM and related electrochemical performance tests,it is found that nano-NiO materials have high purity,strong diffraction peaks,good crystallinity,uniform-particle size and good dispersibility.The discharge specific capacities of the first cycle and after 100 cycles of acid-etching nano-NiO at 100 mAg-1 current are 1393 mAhg-1 and 442 mAhg-1.The rate capability of acid-etching nano-NiO is better than that of unetched NiO.Nano-materials have less polarization,large surface area and high capacity which are helpful for improving electrochemical perform ance of lithium-ion batteries.One-step hydrothermal method to prepare NiO/SuperC composites with different molar ratios,cycle life and rate capability are better than the acid-etching nano-NiO materials.By XRD,TEM and related electrochemical performance tests,it can be known that there is no diffraction peaks of Ni and other impurities peaks.With the further increase of SuperC content,more carbon spheres appeare around NiO particles.NiO/SuperC(5/1)has the best rate capability.The specific capacity is 548 mAhg-1 at 2 Ag-1 high current cycling 10 cycles.When returning to 0.1 Ag-1,the capacity rises to 999.75 mAhg-1.The specific capacities of the first cycle and after 300 cycles of NiO/SuperC(1/5)at 100 mAg-1 current are 702/782 mAhg-1 and 439/459 mAhg-1.The SuperC molar ratio of NiO/SuperC composites increases,and the capacity retention rate of the battery increases.The reversibility is good,but the overall specific capacity decreases.The insufficient amount of addition and poor structural stability lead to large capacity decline.SuperC content has a great impact on the performance of the material.High-temperature calcination of glucose will form carbon layer.The NiO/C composite material prepared by a two-step hydrothermal method can improve the limitations of acid-etching nano-NiO with low first coulombic efficiency and large impedance,and increase the stability of the electrode structure.According to comprehensive analysis of XRD and TEM,NiO/C(0.10 mol/L)has good dispersibility and no impurities are introduced.The first cycle charge/discharge specific capacity at 100 mAg-1 is 892/1008 mAhg-1,and the coulombic efficiency is 88%.2 Ag-1 large current has 248 mAhg-1 capacity,returning to 0.1 Ag-1,and discharge capacity rises to 761 mAhg-1(>718 mAhg-1).NiO/C(0.15 mol/L)the first cycle charge/discharge capacity is 605/671mAhg-1.The charge/discharge specific capacity drops to 361/369 mAhg-1 after 180 cycles,and the capacity retention rate is 54.99%.On the one hand,carbon can alleviate volume expansion;on the other hand,too much carbon content will reduce the specific capacity.Therefore,choosing right glucose concentration is very important for improving battery performance.