部分氧化纳米钴镍合金泡沫的制备及空气电极性能研究

The stability of air electrode is the bottleneck of lithium-air batteries. Carbon based air electrodes are generally employed in the current metal air batteries, which unavoidably causes the problem of carbon corrosion leading to the considerably deteriorated cycle life and reduced coulumbic efficiency. This project aims to investigate the fabrication methodologies and electrochemical properties of partially oxidized Co-Ni nanoalloy foams as self-supporting carbon-free air electrode for Li-air batteries. This novel nanoalloy foam possesses several advantages that can perfectly satisfy the requirement of ideal air electrode, like carbon-free, self-supporting, ultralow density, high specific surface area, high electronic conductivity, large electrochemical window, capability of withstanding large volume change, and ultrahigh electrocatalytic activity for oxygen reduction and evolution reaction, etc. In this project, chitosan-Co-Ni nanoalloy composite foams will be firstly prepared by an electroless plating method by using the chitosan nanofiber nonwoven fabric that has been successfully prepared in our lab as a template. After plating, the chitosan supramolecular aerogels will be simply degraded by heating, resulting in a highly porous and free-standing Co-Ni nanoalloy foams. During this thermal decomposition procedure, Ni-Co composite oxide will be simultaneously formed on the very surface of the Co-Ni nanoalloy serving as passivation layer protecting the further oxidation of CoNi nanoalloy foam. We will devote to understanding the diffusion and co-reduction of cobalt and nickel ions upon the chitosan nanofiber aerogel during the electroless process; the pyrolysis mechanism of chitosan and formation mechanism of Co-Ni composite oxides on the nano-alloy foam surface; and the structural evolution of the partially oxidized Co-Ni nanoalloy foam and the formation and decomposition mechanism of byproducts inside the air electrode during charging and discharging; in combination with the theoretical simulation of oxygen adsorption and decomposition on the partially oxidized cobalt-nickel nanoalloy surface. The central objective of this project is to prepare a high performance air electrode based on partially oxidized cobalt-nickel nanoalloy foams. The outcomes of this research will be significant in opening a novel avenue for the general preparation of new generation of high performance and ultrastable air electrodes for metal-air batteries.

空气电极稳定性是锂空气电池的瓶颈，目前广泛采用的含碳空气电极存在碳腐蚀问题，会降低电池寿命和效率。本项目拟开展部分氧化纳米钴镍合金泡沫的制备方法及空气电极性能研究。该新型纳米金属泡沫具有可以满足理想空气电极的诸多优点，如不含碳、自支撑、比重轻、大比表面、导电率高以及催化活性高等。研究方案是以本实验室已成功合成的壳聚糖纳米纤维气凝胶无纺布为模版，利用化学镀的方法制备壳聚糖-钴镍合金泡沫，进一步利用控制热解法制备部分氧化纳米钴镍合金泡沫。将重点研究化学镀过程中，钴镍金属离子在壳聚糖气凝胶表面的扩散及原位共沉积原理；热解过程中，壳聚糖的分解及纳米合金泡沫表面氧化物的形成机制；锂空气电池充放电过程中，合金泡沫电极的结构和充放电产物演变机制; 氧气在部分氧化钴镍合金表面吸附和分解理论模拟计算。目标是建立部分氧化纳米钴镍合金泡沫的合成方法，为制备新一代高活性长寿命金属空气电池用空气电极材料开拓新思路。

可充锂空气电池具有超高理论能量密度(>3500Wh kg-1)，在电动汽车、电动工具和大规模储能领域具有非常诱人的应用前景。空气电极是锂离子、电子和氧气的三维传输和电化学反应的场所。空气电极的表现直接决定了的电池的性能。因此，制备获得高性能低成本的空气电极材料至关重要。本项目通过静电纺丝方法制备了钴、镍、锰及其氧化物/复合氧化物的三维多孔电极材料。通过调控金属前驱体比例，活性位点与载体的界面，优化造孔条件，控制煅烧温度，使电化学性能有了较大的提高。另外，通过金属有机框架材料（MOF）沸石咪唑酯骨架材料（ZIF）为前驱体，调控不同金属比例及煅烧条件制备出了的CuNi/C，CuMn@NHC电极材料，并得到了出色的氧还原性能。利用NH2-MIL-125(Ti)基MOF为前驱体，利用MOF中的氨基在热分解过程中锚定Cu单原子金属制备了在TiO2/C 负载单原子催化剂，并表现出出色的电化学性能和稳定性。此外，利用壳聚糖生物高聚物水凝胶为载体的获得表面部分氧化的Mn/Co双活性位点修饰碳载体，使高活性的Mn/Co高效、均匀地结合在一起，促进了电化学活性。通过与石墨烯的复合，使获得的氧化物基La0.8Sr0.2MnO3催化剂的性能有了提升。项目深入分析了电极的微观结构，组成成分,界面与电化学器件性能的构效关系。本项目研究结果为开发高性能低成本的空气电极材料积累了科学依据。本项目共发表论文48篇，申请和授权技术发明专利3项，培养毕业博士研究生2名，硕士研究生5名，培养出站博士后4名。