The Preparation Of A-MNO₂ And Its Application In Secondary Zinc Manganese Battery And Oxygen Electrode

With the development of electronic technology, zinc manganese battery, as the historic and the most developed product, whose demand and production have been rising year by year. However, zinc manganese battery on the market is basically primary battery. The discard of a large number of zinc manganese batteries is not only a waste of resource, but also the cause of serious pollution to the environment. Therefore, it is extremely urgent to explore and study the secondary zinc manganese battery with a good cycle performance and a high charge-discharge specific capacity. In this paper, the experiment synthesized λ-MnO2 with a spinel structure. And the electrochemical experiments show that in the mixed salt solution of partially acid, X-MnO2 has an excellent rechargeable performance. On this basis, λ-MnO2 used as the positive pole study of the secondary zinc manganese battery has been researched. In addition, among the chemical power, fuel cell, as a new energy battery, shows broad prospects for development with the advantages of high efficiency, cleaning, safety, etc. However, the bottleneck of this battery is mainly oxygen electrode catalyst. The research on low cost and high catalytic activity catalyst is necessary to realize fuel cell’s commercialization. Research showed that the oxygen catalyzing of manganese dioxide is "quasi four-electron oxygen reduction catalysis process", and manganese dioxide is considered to be an oxygen reduction catalyst that could replace noble metal. The high specific surface area and large pore size of the synthesized λ-MnO2 showed that the crystal stands a good chance to be a well performed catalyst. In this paper, synthesized λ-MnO2 is studied as oxygen electrode catalyst. The main content and innovation points of the paper are as follows:1. First of all, use high temperature solid phase method to produce precursor LiMn₂O₄, then λ-MnO2 is synthesized by the treatment of LiMn2O4 with dilute acid solution. Through a series of tests, the optimum synthesis conditions are determined as follows:constantly and mechanically stir and process the precursor for 12 h in 0.2 mol/L dilute hydrochloric acid under normal temperature. Compared with the precursor LiMn2O4, both the crystal plane spacing and the crystal cell parameters of X,-MnO2 are decreased. And a slight contraction in unit cells is also showed up.2. Applied the synthesized 3-D spinel structure of λ-MnO2 to secondary zinc manganese battery. The λ-MnO2 electrode shows high specific capacity, good coulombic efficiency and rate ability in 1 mol/L Li2SO4+1 mol/L ZnSO4 electrolyte. Electrochemical test results showed that the electrochemical reaction of battery is diffusion controled. Compared with the traditional alkaline zinc manganese battery, the discharge voltage of the battery（1.5～2.1 V） is 0.8 V higher than the discharge voltage of zinc manganese battery （0.6～1.5 V）. Batteries have better cycle life. In the 1000th charge and discharge cycle, the specific capacity is 99.0 mAh/g, attenuated to 77.28% of the first cycle. Ratio experimental results showed that when charging and discharging under 20C, the battery still had 38.3 mAh/g discharge specific capacity, which can satisfy the rapidly-changing power supply network.3. Used the sol-gel method to synthesize the perovskite La0.8Ce0.2MnO3 powder, which had been applied to the λ-MnO2’s oxygen electrode catalyzing as a doping agent. The results showed that there was obvious improvement in catalytic performance of the synthesized λ-MnO2 compared with electrolytic manganese dioxide products. When λ-MnO2 mixed with La0.8Ce0.2MnO3, due to synergistic effect, a significant improvement is showed up compared with pure λ-MnO₂. And when the doping agent meets the proportion of λ-MnO2:La0.8Ce0.2MnO3=10:1, the catalytic performance is optimal.