梯度孔增强纳米多孔合金@固溶氧化物/集流体一体化电极制备及其协同储能机理

Pseudocapacitors have high theoretical specific capacitance, but the poor conductivity and stability of the traditional electrodes lead to unsatisfactory energy storage behavior. In order to construct high strength, high conductivity and high efficiency pseudocapacitive electrodes by means of solid solution doping and 3D bicontinuous metal bonding and gradient pore reinforcing, the sandwiched Mn-rich alloy/current collector precursor, metallurgically bonded by hot rolling, is dealloyed partially and then annealed to form a sub-micron porous protective layer with good mechanical property on the surface of the precursor, which is then completely dealloyed and electrochemically polarized and annealed for structural regulation of oxides to prepare sandwiched gradient pore reinforced nanoporous alloy@solid solution oxide/current collector composite electrode. The influence factors and mechanism of metallurgical bonding, dealloying pore forming, pore coarsening and self-oxidation by electrochemical polarization process are investigated to ascertain the tuning ways of the fabrication of gradient pore reinforced nanoporous alloy@oxide. The effects of gradient pore structure, composition and structure of alloy and self-grown oxide and their interface property on the strength and electrochemical property of the composite electrodes are studied. the key factors affecting the electrochemical performance of composite electrode, the establishment of energy storage model and the elucidation of its mechanism are discussed, combined with theoretical calculation. The results are expected to provide theoretical guidance and technical approach for the development and application of nanoporous metals based energy storage devices with high performance.

赝电容超级电容器具有高的理论比电容，但传统电极导电性及稳定性差导致其储能行为不理想。本课题以构建高强、高导、高效能赝电容电极为目标，以固溶掺杂、三维双连续金属复合及梯度孔强化为手段，采用热轧复合制备三明治结构富锰合金/集流体前驱体，对前驱体表层脱合金和退火处理，使其表面形成有良好力学性能亚微米级多孔金属保护层，再继续完全脱合金和电化学极化氧化，并退火调控氧化物结构，制得三明治结构梯度孔增强纳米多孔合金@固溶氧化物/集流体一体化复合电极。研究冶金结合、脱合金造孔、孔长大和自氧化过程的影响因素和作用机理，探明制备梯度孔增强纳米多孔合金@氧化物的调控途径；研究梯度孔结构、合金及自生长氧化物成分、结构、氧空位及界面特征对复合电极强度和电化学性能的影响；结合理论计算，探讨影响其电化学性能的关键因素，建立储能模型并阐明机理。该研究结果可为基于纳米多孔金属的高性能储能器件开发应用提供理论指导和技术途径。

电化学储能已成为应对能源危机和环境污染的关键技术之一，过渡金属具有丰富的可变价态可实现高效电化学储能。但大部分过渡金属氧化物属于半导体或绝缘体，且氧化还原过程往往伴随着较大的体积变化，从而影响电极结构和性能的稳定。本项目通过纳米多孔合金电化学极化自氧化处理在合金表面原位自生一薄层羟基氧化物，获得核壳结构纳米多孔合金@氧化物自支撑电极，氧化物与基底通过刃型位错形成小角度晶格错配，有利于界面电子传输和结构稳定。基于具有相似功函数的NiMn合金，系统研究了第三元素M（Ti、V、Cr、Fe、Co、Cu）掺杂对NiMMn三元合金自生氧化物电子结构和电化学性能的影响，具有较窄带隙(-2.3 eV)的NiCoMn固溶氧化物具有最优的赝电容性能，自支撑电极的体积比电容和能量密度在电流密度为1A cm-3时可达2012F cm−3和145mWh cm−3；电化学极化造成的原子重构优化了固溶氧化物的电子结构，抑制了水分解，使其工作电压可以达到1.4V以上；结合高分辨电镜和密度泛函理论，揭示了OH−会优先吸附于(001)和(111)活性晶面，Co掺杂激发了更多活性面的暴露，有利于OH−的吸附，从而获得最优的比电容。同时，本项目开展了复合电极的工程制造技术研究，采用合金铸造加工+复合轧制技术制备集成集流体的“三明治”结构复合带材，然后脱合金+自氧化处理批量制备一体式复合电极。电极片力学性能满足商用电池组装工艺要求，器件能量密度达到116mWh cm−3（相对于双电极体积），高于项目设定目标。此外，项目还研究了纳米多孔合金自燃+低温退火技术制备含空位缺陷和金属掺杂的纳米多孔合金@氧化物复合电极用于锂离子电池负极，复合电极的面积比容量（9.48mAh cm-2）远高于商用石墨负极。本项目研发的一体式复合电极不仅适用于赝电容器、锂离子电池等储能器件，还有望应用于电解水催化电极等电催化领域。