MnO2基水系锌离子电池正极材料合成及离子共嵌入机制研究

Recently, energy and environmental problems have become increasingly serious. The aqueous Zn-ion batteries have become an important development direction for large-scale storage batteries in the future due to its high safety and low cost. Manganese-based oxides show high theoretical capacity, abundant reserves and environmental-friendly, making them promising cathode materials for aqueous Zn-ion batteries. However, there are still some controversies about the zinc storage mechanism of aqueous zinc ion battery. In recent years, the mechanism of co-insertion of zinc ions and hydrogen ions into manganese dioxide pore channels or layers has been widely recognized, but the research on the co-insertion mechanism is still insufficient. We aim to reveal the co-insertion mechanism of manganese dioxide as cathode material of aqueous zinc ion battery during charge/discharge. Via synthesizing a serious of manganese dioxide materials with various phase and different pre-inserting ions and adjusting the ion type and concentration of electrolyte, we plan to reveal the influence of the hole size of manganese dioxide, pre-inserting ions or H2O as well as electrolyte to the insertion rate, proportion and degree of zinc ion and hydrogen ion co-insertion, so as to complement and perfect the zinc storage mechanism of manganese dioxide as cathode material of aqueous zinc ion batteries. On this basis, the high-performance cathode materials of aqueous zinc ion batteries will be selected to provide a theoretical basis and technical support for the preparation of aqueous Zn-ion battery materials with high specific capacity and long cycle life.

近年来，能源环境问题日益严重，水系锌离子电池因其高安全性、低成本等特点，成为未来大规模储能电池的重要发展方向。二氧化锰具有较高的理论容量且储量丰富，环境友好，是很有前景的水系锌离子电池正极材料，然而报道中关于水系锌离子电池的储锌机理仍然存在一些争议。近年来，锌离子与氢离子共嵌入二氧化锰孔道或层间的机制得到了较为广泛的认可，但对此共嵌入机制的研究还不够充分。本项目旨在研究并揭示二氧化锰在作为水系锌离子电池的正极材料在充放电过程中的离子共嵌入机制。通过合成一系列不同物相和预嵌入离子的二氧化锰材料并调节电解液离子类型和浓度，研究二氧化锰孔道尺寸、预嵌入离子或结晶水、电解液等对锌离子和氢离子共嵌入速率、比例和程度的影响规律，从而补充和完善二氧化锰作为水系电池正极材料的储锌机制。在此基础上筛选出性能优异的锌离子电池正极材料，为组装出高比容量、长循环寿命的水系锌离子电池提供理论基础和技术支持。

锰基氧化物具有较高的理论容量、且锰储量丰富、成本低廉、环境友好，成为具有研究前景的锌离子电池正极材料。但锰基氧化物的容量衰减、储锌机制不明确等原因，限制了其进一步应用。本项目揭示了MnO2正极材料不同物相对氢离子和锌离子嵌入过程的影响。层状结构的δ-MnO2具有较高的比容量，而孔道结构的β-MnO2具有更好的循环稳定性，两种MnO2物相的比容量差别主要来自于第一个放电阶段的H+嵌入。为了缓解MnO2材料在Zn2+/H+嵌入过程中的锰溶解问题，在α-MnO2纳米棒外原位生成导电聚合物聚吡咯（Ppy），得到α-MnO2@Ppy核壳结构，有效提高材料的循环稳定性。此外，本项目选择与锰基氧化物体系相近的钒基氧化物，研究缺陷对钒基氧化物电化学性能的影响。氧空位作为常见的阴离子缺陷，能够调节钒基氧化物材料的晶体结构，减轻锌离子与氧化物晶格间的静电相互作用，提供更多的锌离子嵌入活性位点，从而提高材料的锌离子传输效率和储锌容量，但氧空位浓度过高容易导致材料活性位点减少和结构坍塌，降低循环稳定性。本项目通过研究物相、包覆、缺陷等对锰基、钒基氧化物电化学性能和离子嵌入机制的影响，对氧化物正极材料的储锌机制进行补充，并筛选出几种高比容量、长循环寿命的正极材料，为进一步开发综合性能优异的水系锌离子电池正极材料提供理论基础和技术支持。