弹性插层碳材料的制备及其储能性质的研究

Dual-ion energy storage system is a new opportunity to make high energy density compatible with high power density, where cations and anions from the electrolyte are both utilized for intercalation/de-intercalation to store/release energy. This unique mechanism can offer high working potential and realize fast charge/discharge response. Due to the mismatch of electrolyte ion size and interlayer spacing of active material, such system shows low specific capacitance and poor cycling stability. Therefore, this project aims to synthesize elastic carbon materials with tunable structures for ion intercalation/de-intercalation and to further investigate the energy storage mechanism. Various methods such as combining plasma enhanced chemical vapor deposition with magnetron sputtering and electrochemistry are utilized to synthesize the elastic carbon materials; physical/chemical properties and structure variations of active materials during charge/discharge cycles are investigated by in-situ characterization methods; dual-ion energy storage devices with high performance are finally achieved by further optimizing parameters, rationally designing the configuration and matching both electrodes. Up to now, there have been no reports using elastic carbon materials with tunable structures in dual-ion energy storage systems. The tunable, elastic carbon materials synthesized in this project are expected to show excellent electrochemical properties and the potential to fabricate energy storage devices with high energy density, high power density and high stability.

双离子插层储能体系是利用电解液中的阴、阳离子在正、负电极同时进行插层反应的新体系。因为其独特的储能方式可实现高工作电压和快速充放电，所以该体系可将高能量密度和高功率密度有效地结合起来。但是目前插层电极材料的容量低、稳定性差，其根本原因是插层离子尺寸与电极结构的不匹配。因此，本项目拟制备层间结构可调控的弹性插层碳材料并探究其储能机制。采用等离子体增强化学气相沉积与磁控溅射结合、电化学方法等多种手段制备弹性碳材料电极，并构建原位表征手段追踪离子迁移以及对电极结构的影响；通过优化器件构型，合理匹配正负极材料，设计高性能双离子插层储能器件。制备具有弹性、层间结构可调控的碳基插层材料，并将其应用于双离子插层储能器件中，国内外未见报道。本项目拟制备具有大容量、高倍率性和性能稳定的插层材料，最终构筑兼具高能量密度、高功率密度和高稳定性的双离子插层储能器件。

双离子插层储能体系利用独特的储能方式可实现高工作电压和快速充放电,同时获得高能量密度和高功率密度。本项目以制备层间结构可调控的弹性插层碳材料为核心，探究了电解液离子与插层电极材料的相互作用，并构筑了兼具高能量密度、高功率密度和高稳定性的双离子插层储能器件。具体研究内容如下：（1）通过阴离子预嵌入和电催化析氧反应相结合的方法，扩大了碳纤维纸电极的层间距、引入了介孔结构和含氧官能团。缓解了离子的聚集状况，同时降低了PF- 6的离子吸附能，并加速了PF- 6在电极中的扩散动力学，从而提高了反应速率、电极容量和循环稳定性。这种方法有效解决了载荷离子与电极材料尺寸失配的问题，为制备弹性插层碳材料提供了广阔思路。（2）新型层状材料展示出了插层储能的巨大潜力。我们通过化学刻蚀法成功合成了Ti3C2Tx，这种MXene材料层间距与离子液体电解质中的阳离子尺寸相匹配，并体现出了优良的插层储能性能。以此为电极，设计了MXene-石墨双离子电池构型，最大能量密度达到40 Whkg-1，最大功率密度达到1608Wkg-1。Ti3C2Tx解决了载荷离子与插层材料的尺寸及正负极失配的问题，对进一步提高双离子插层储能体系性能具有重大意义。（3）如何将两种不同的层状材料复合而不堵塞层间空间和减少活性表面是制备插层电极材料的难题。我们报导了一种两步制备Ni-MOF@Co(OH)2垂直阵列的方法：首先采用溶剂热法在泡沫镍上生长垂直取向的Ni-MOF-24纳米片，然后在Ni-MOF-24片上电沉积Co(OH)2。垂直的取向提高了电极的导电性，同时暴露出了更多的电化学活性表面。在电流密度为2Ag-1的条件下， 其比电容可达到1448Fg-1。Ni-MOF@Co(OH)2和活性炭构筑的混合型超级电容器能输出22400Wkg-1的功率密度和45.7Whkg-1的能量密度。经过8000次循环后，其容量保持率为87.3%。该策略解决了电极低导电性和取向杂乱的问题，为制备复合型插层电极材料提供了方法。