A Research On Anode Material Of Nickel-Zinc Battery

With the depletion of ore energy and growing environmental problem, the development of new clean energy has become essential. As a clean, sustainable and efficient energy device, battery has been widely studied. Nickel-zinc battery has become the promising candidate for its characteristic of high energy density, high power, wide operating range and environmental-friendliness. However, Nickel-zinc is limited in widespread commercialization by its poor cycle life and low stability. It’s due to the dissolution of active materials, shape change of the Zn electrode and the formation of Zn dendrite. In many countries, amount of researchers have been improved battery performance with adding additives and incorporating the metal or metal oxide with high hydrogen over potential in zinc negative electrode. The zinc oxide composites have been successfully synthesized by doping iron, cobalt and nickel. Such composites can improve the nickel-zinc battery cycle stability and discharge capacity.By co-precipitation- hydrothermal method, we discussed the different reaction with different precipitating agent, p H value and raw materials containing different anions for synthesizing Zn O/Zn Fe2O4 composites. Using the precipitating agent mixed by Na OH and Na2CO3, the p H=10, Zn O/Zn Fe2O4 compounded by raw materials containing NO3- has a better performance. It gets a lower charge platform and higher discharge platform at the 10 th cycle with 567 m Ah/g, 545 m Ah/g and 538 m Ah/g discharge capacity as well as maintains high cycle stability at the first 20 cycle.Using the optimal synthesis conditions, the different iron content of Zn O/Zn Fe2O4 composites is synthesized. Using the XRD and LPDS technologies to investigate the structure, shows the iron content has a great influence on the Zn O/Zn Fe2O4 composites. Each composite material with different iron content has the characteristic peak of Zn O. With the increasing of iron content, characteristic peak areas decreased. When the iron content is less than 5% molar fraction, the iron is formed as Fe2O3 presents on the surface of the Zn O crystal structure; when iron molar fraction exceeds 5%, it presents in the form of Zn Fe2O4 on Zn O crystal interface. And it increases the stability and conductivity of Zn O crystal structure. When iron content is excessive, the structure of Zn O would be destroyed by the excessive Zn Fe2O4 and make Zn O be inactive and not discharged. In Tafel test, with a increasing of iron content, the corrosion potential of the electrode start positive shift and the corrosion current decreases; when iron content is 5%, the composite material obtain positive corrosion potential and the corrosion current is smaller than that of pure zinc oxide. In cyclic voltammetry, when the iron adds, the anodic peak moves toward the cathodic peak. When iron content is 20%, no obvious cathode peak. It indicates that the composite material can not have the reversible redox reactions any longer and cannot be a complete charge and discharge. This is also confirmed by the CV testing and constant current charge-discharging test. 5% of the iron content in the composite material exhibits the best performance in the constant current charge-discharge test and shows the lowest charge plateau and the highest discharge plateau in the 10 th cycle, it leads to a good cycling stability and obtained 545 m Ah/g discharge capacity. We also studied the effects of different conductive agent for battery performance. The results show that using a conductive polyaniline can reduce the internal resistance of charge and discharge of the battery effectively. Especially, the rechargeable internal resistance, make the battery showed a better stability. However, the increasing of polyaniline reduces the capacity of the battery.Nickel and cobalt are elements in the same family and period as iron, we also discussed the influence on Zn O/Zn Fe2O4 composites with the Nickel-iron doped and Cobalt-iron doped. XRD and LPDS show that nickel-iron incorporation has a few influences on the structure and particle size of the composite material. However, Cobalt-doped destructed the structure of Zn O/Zn Fe2O4, as the distribution of particle size in the material became uneven. In Tafel measurement, the cobalt iron-doped corrosion exhibited revised voltage, and the corrosion current increased compared with Zn O / Fe composites. CV tests shows that cathodic peak have a positive shift as anodic peak have a negative shift in nickel-iron doped and cobalt-iron doped composites, compare with those in Zn O / Fe. In the constant current charge-discharge test, the composite materials Zn O/Zn Fe2O4 which get from the co-doped nickel-iron, exhibit excellent cycle stability and discharge capacity. After 30 weeks, the discharge capacity was 533 m Ah/g and the capacity retention rate was 96.6%.