超级电容器中高性能m-MnMoO4纳米线/3D石墨烯复合结构储能机制研究

Monoclinic manganese molybdate (m-MnMoO4) electrode materials used in advanced supercapacitors have received fascinating attention for high-efficient renewable energy storage and conversion, owing to its high theoretical capacity (3503 F g-1). However, in practical supercapacitors, the drawbacks of very low energy conversion efficiency (only η= 5.3-65.6%) are associated with three fundamental scientific issues: (1) m-MnMoO4 material always remains a great challenge for the restriction of electronic conduction at a high-rate discharging condition; (2) the slow speed of ion transport with sluggish kinetics between electrodes in traditional electrolytes; and (3) the ambiguous understanding of complex reaction mechanism in electrochemical stages. . To solve these vital problems, m-MnMoO4 nanowires/3D graphene nanocomposites with a novel construction can be successfully achieved to design the highly efficient microwave-irradiation approach in the project, and then focus on the exploration of the electrochemical reversible mechanism in supercapacitor. Besides, density functional theory (DFT) calculations provide a further comprehension and accurate prediction of m-MnMoO4 nanowires/3D graphene structural details and energy conversion/storage mechanism in supercapacitors. The nanocomposites demonstrate unique promising performances to combine the improved electrical double-layer and redox supercapacitors, which can enhance the high electronic conductivity of ultrafine m-MnMoO4 nanowires with high specific surface area, and avoid the agglomeration of 3D graphene. To satisfy the critical requirements in capacitors at a high–rate discharge, an outstanding Li2SO4-based electrolyte is applied to dramatically increase the high ionic conductivity, electrochemical stability over a wide working voltage, and power density, giving a new insight into confirm the intrinsic regulations of the electrochemical system. Moreover, it is widely recognized that the rapid charge transport mechanism of the nanomaterials is systematically researched via in-situ Raman technology and in-situ XRD analysis for monitoring the continuous evolutions of micro-architecture properties at different stages. Especially, the in-situ Raman spectroscopic platform strategy reported here is amenable for manipulating the m-MnMoO4 nanowires/3D graphene nanoelectrodes to obtain optimum properties of supercapacitors at a large current density and a wide range of temperature. The project can provide a good platform for further revealing the close-relationship between the crucial preparing parameters, phase, topology and the overall supercapacitor properties. In summary, the innovation of project aims at the fundamental scientific challenges of m-MnMoO4 nanowires/3D graphene nanomaterials to dramatically elevate supercapacitor performances with good energy efficiency, high power density and energy density, and excellent long-term cycling.

钼酸锰(m-MnMoO4)是超级电容器中能量高效清洁利用的潜在电极材料，其理论比容高达3503 Fg-1，但实际利用率偏差(仅5.3-65.6%)，原因是电子传导不佳、离子传输受阻、且储能机制不清。鉴于尚存科学问题，项目拟研究高性能m-MnMoO4纳米线/3D石墨烯复合结构超级电容器储能机制。借助第一性原理计算模拟微结构、推测可能储能机制。利用微波辐射法在3D石墨烯组装阵列m-MnMoO4纳米线，发挥结构协同效应，优化电子传导性；探明新型Li2SO4基复配电解液，改善离子传输性；采用原位XRD、原位电化学拉曼揭示不同电压过渡态的晶体结构和电子结构演变历程，剖析储能机制。结合理论和实验结果，科学阐明储能机制，归纳成分、形貌、机制与性能的本质规律。项目创新点旨在开辟m-MnMoO4纳米线/3D石墨烯的理论模拟、材料设计、电化学机理研究的新局面，为超级电容器性能提升奠定理论和实验基础。

超级电容器是借助电极材料实现清洁能量高效储存与清洁利用的可逆器件，其利用电解液和双电极之间的氧化还原反应或双电层效应完成高电流密度下电荷快速储存与转化。MnMoO4材料性能提升空间最大，其主要问题是该材料的电导率较差。本项目在已取得良好工作基础上，围绕结构调控和性能优化的关键问题，研制出了MnMoO4电池材料来提高电导率、且避免高导电性和高比表面石墨烯团聚、以改善电子传导与离子传输性能。已取得了一批有创新性的系列成果。