三维纳米多孔MnO2储能结构的激光复合制备新方法及其结构功能一体化研究

We propose a new laser-hybrid fabrication method to achieve a novel three-dimensional nanoporous MnO2 structure for high-efficiency energy storage applications. We also investigate the scientific issues underlying the integration of structure and function of the proposed nanostructure. Currently, the fabrication of MnO2 nanostructure involves depositing premade nanoscale MnO2 elements onto a base material, forming a thin membrane mechanically bonded to the base. We hereby propose a new approach. First, a mixed metal powder (one element is Mn) is laser-deposited onto the base and forms a bulky layer. Then, through dealloying, the other elment is etched away from the alloy leaving innumerable nanoscale voids, while the remaining Mn is oxidized to become MnO2, resulting in a three-dimensional network consisting of nanopores and MnO2 nanoskeletons. The achieved nanostructure significantly increases the specific surface area and hence the energy storage efficiency. In the mean time, a three-dimensional structure with considerable thickness is obtained that distinguishes from its thin film counterpart, realizing structuralization as well as functionalization of the material. Additionally, the fabricated nanostructure forms a metallurgic bonding to the base, avoiding the compromise in device performance caused by mechanical bonding. Recently, three-dimensional nanoporous metal Mn structure has been achieved in our group. Therefore, the successful development of such fabrication method for MnO2 with a similar nanostructure is highly promising and bears practical significance for energy storage applications.

本项目提出通过激光复合制备新方法,获得一种全新的三维纳米多孔MnO2高性能储能结构,并探究其结构与功能一体化方面的科学问题.纳米MnO2结构被广泛应用于储能技术,其制备多采用在基底上沉积预制的纳米MnO2基本单元的方法,从而获得与基底机械结合的纳米MnO2薄膜.我们提出一种全新的思路：利用激光将混合的两种金属粉末（一种是Mn）沉积在基底上形成合金层,通过脱合金法腐蚀合金层中的另一组元,生成的金属Mn单质在扩散生长的同时被氧化为MnO2,最终形成由纳米孔洞和纳米MnO2骨架组成的三维网状结构.该三维网状结构具有很高的比表面积,极大提高了储能效率,同时又获得了区别于薄膜的具有相当厚度的三维结构体,实现了结构功能一体化.此外,该结构与基底间实现了冶金结合,弥补了机械结合存在的性能折损.课题组前期用该方法已研制出三维纳米多孔金属Mn,因此用该法制备MnO2储能结构具有可行性和重大的现实意义.

MnO2和MnCO3作为能源器件的电极材料受到广泛关注，其功能结构的一体化制备一直是目前研究的重点和难点。本项目针对这一难点，采用激光沉积-脱合金复合方法，开展了以下研究：（1）激光沉积-脱合金复合制备技术的理论机制研究；（2）激光沉积-脱合金复合制备纳米多孔MnO2研究；（3）激光沉积-脱合金复合制备MnCO3微球研究。取得的研究结果包括：（1）确立激光沉积的加工结果对脱合金加工结果的遗传影响，建立激光沉积技术与脱合金技术共同作用时的理论机制；（2）制备了纳米多孔MnO2和MnCO3微球；（3）提出了纳米多孔MnO2和MnCO3微球的形成机制，Cu的溶解和Mn的钝化形成纳米多孔MnO2，MnCO3微球的形成包含形核和长大；（4）探索了纳米多孔MnO2和MnCO3微球的性能及潜在应用，纳米多孔MnO2具有良好的高温稳定性能，MnCO3微球呈现赝电容特性和较好的可逆性。本研究的成果初步实现了能源器件电极的功能结构一体化制备。