喷雾干燥构筑三维多孔导电骨架/MnC2O4复合微球及其储锂性能

MnC2O4 is a high-capacity and low-cost anode material for lithium-ion batteries, but its conductivity and rate performance need to improve. To improve the conductivity and rate performance, we will use spray-drying method to prepare a 3D porous conductive skeleton/MnC2O4 composite microspheres using conductive carbon black, carbon nanotubes or graphene as the conductive matrix materials. This proposal will focus on the critical problem of the design and construction of the porous structure and its electrochemical performance and solve it.. In this proposal, Atomic force microscopy (AFM) and Spherical aberration corrected Transmission Electron Microscope (STEM) will be applied to investigate the nucleation and growth mechanism of conductive coated MnC2O4·2H2O nanocomposites at the atomic and molecular level, leading to an ability to control their morphologies and the structures at the atomic and molecular level. A dimensional analysis method will be developed to investigate the formation process of the porous structure of the conductive skeleton/MnC2O4 microspheres in the spray drying processes, which will reveal the mechanisms of the heat and mass transport to control the porous structure. The effects of porous structure on lithium storage properties and the transport behaviors of electrolyte, ion and electron will be studied by CV, EIS, GITT and PITT, etc., which will be used to elucidate the mechanism of the lithium storage enhanced by porous structures. Based on the above studies, we will establish the relationship between the preparation process, porous structure and properties of conductive skeleton/MnC2O4 composite microspheres. These results will serve as guides for the design and control of the porous structure and electrochemical performance of conductive skeleton/MnC2O4 composite microspheres, which will result in their controllable preparation. . This study can not only provide theoretical guidance and technical support for the application and development of manganese oxalate anode materials, but also provide new ideas and scientific references for other porous electrode materials.

MnC2O4是一种高容量的廉价锂离子电池负极材料，但电导率低、倍率性能差。本项目以导电碳黑、碳纳米管、石墨烯为导电骨架材料，用喷雾干燥构筑导电性能和倍率性能优良的三维多孔导电骨架/MnC2O4复合微球，关键是孔结构与性能的设计与控制。用原子力显微镜和球差透射电镜在原子分子尺度研究导电相包覆MnC2O4·2H2O纳米复合粒子的成核生长机制，实现在原子分子水平对其形态结构进行控制。用量纲分析法研究喷雾干燥中微球多孔结构的形成规律，揭示传热传质调控孔结构的机制。用CV、EIS、GITT、PITT等研究多孔结构对储锂性能、电解液、离子和电子输运的影响，阐明多孔结构强化储锂的机理。建立微球制备工艺、多孔结构与储锂性能间的关系，指导多孔结构与性能的设计和控制，实现微球的可控制备。本研究不仅能为MnC2O4负极材料的应用和发展提供理论指导和技术支撑，而且也能为其它多孔电极材料的研究提供新思路和科学参考。

MnC2O4是一种高容量的廉价锂离子电池负极材料，但电导率低和充放电过程中体积变化导致其性能差。本项目通过调控草酸锰结晶生长设计形貌和与MWCNT复合构建3D多孔导电网络，增强电导率低和舒缓体积变化的影响，提高电化学性能。T型微反应器内高速流体（18.75 m·s-1）流经一维草酸锰团聚物内部空隙时，产生的高速流体作用力在径向剥离初级颗粒和轴向压缩初级颗粒，在团聚物内流动方向形成新的流动通道，在短时间（2.7s）形成多孔草酸锰微管。微波溶剂热中草酸锰棒的形成遵循溶解-重结晶-熟化机制。柠檬酸阴离子的强配位能力和选择性吸附能减缓锰离子的释放速率，促进纳米棒的形成，而纳米棒通过氢键和静电作用组装成束。微波溶剂热制备的草酸锰束在10 A/g下循环2000次的放电容量为615mAh/g，保持率95.2%。锰离子与MWCNT表面电荷通过静电作用形成的络合物可作为成核生长位点诱导形成草酸锰棒，同时MWCNT的柔性使其在棒状结构中卷曲缠绕并包裹在表面，脱除结晶水后在内部形成三维多孔纳米导电网络。喷雾干燥中颗粒内部吸附水汽化后留下多孔结构，吸附水汽化体积膨胀和逸出对颗粒内部一次粒子产生作用力，其累积效果（冲量）决定了颗粒能否破碎-团聚形成新颗粒。当干燥温度过低或过高时，吸附水蒸发作用力过小或作用时间过短小，其冲量小不足以克服颗粒内部粘附力冲量，颗粒不会破碎，保持初始形貌。只有在合适干燥温度下，吸附水蒸发作用力冲量才能大于颗粒内部粘附力冲量，棒状颗粒的一次粒子被剥离，重新团聚成褶皱MnC2O4/MWCNT多孔球。用响应面方法研究喷雾干燥温度、浆料流量、浆料浓度及其相互作用对MnC2O4/MWCNT球的放电比容量和保持率的影响，建立了它们与喷雾干燥工艺间的定量关系，优化了喷雾干燥工艺。本研究不仅可为设计性能优良多孔MnC2O4提供理论指导和技术支撑，也可为其它多孔电极材料的研究提供借鉴和参考。