碳气凝胶活化对于电极嵌锂性能的影响

碳气凝胶由于其对于可充电锂离子电池的高能嵌锂特性, 近年来受关注程度逐渐增加. 碳气凝胶以间苯二酚-甲醛在碳酸钠催化下, 通过溶胶-凝胶工艺、常压干燥技术、碳化、活化后制得. 经CO₂气体活化后的碳气凝胶结合了无定型和纳米多孔结构的优点, 在材料原有基础上丰富了多孔结构, 增加了嵌锂点位. 其中, 微孔提供了高比表面积和孔体积以容纳锂及其化合物; 介孔则提供了锂离子大量传输的通道, 从而使得电极具有更高的离子电导率. 这些微结构的优化使材料获得了更高的嵌锂比容量. 此外, 活化碳气凝胶显示了2032 m²·g^-1的比表面积. X射线衍射(XRD)和扫描电子显微镜(SEM)的测试结果分别表明了其无定型特质以及纳米颗粒的网络状骨架. 该材料在首次和第50次恒流充放电(50 mA·g^-1)循环的嵌锂容量分别为3870和352 mAh·g^-1, 对应的可逆容量分别为658 和333 mAh·g^-1. 表明了CO₂活化对于改善碳气凝胶嵌锂性能的可行性, 且对于其它多孔电极材料的制备及特性优化提供了一种途径.

Effect of Carbon Aerogel Activation on Electrode Lithium Insertion Performance

Carbon aerogels have received much recent attention as high-capacity insertion anodes for rechargeable lithium ion batteries. Carbon aerogels were synthesized from resorcinol-formaldehyde with a sodium carbonate catalyst via a sol-gel process, ambient drying, carbonization, and activation. Gaseous CO₂-activated carbon aerogels combined the advantages of amorphous and nanoporous structures, with richer porous structures and more lithium insertion points than conventional carbon aerogels. Microporosity analysis indicated a high surface area, and the pore volume effectively retained lithium and its compounds. The mesoporosity allowed the mass transport of Li+ and conferred high ionic conductivity to the electrode. These improvements led to a higher lithium insertion capacity, and the activated carbon aerogel exhibited a specific surface area of 2032 m²·g^-1. X-ray diffraction (XRD) and scanning electron microscopy (SEM) revealed an amorphous structure and nanoparticle network skeleton, respectively. Lithium insertion capacities of 3870 and 352 mAh·g^-1 were exhibited in the 1st and 50th galvanostatic discharge-charge (50 mA·g^-1) cycles, respectively. This corresponded to irreversible capacities of 658 and 333 mAh·g^-1, respectively. This work demonstrates the feasibility of CO₂ activation for improving lithium insertion performance in carbon aerogels, and provides preparation and optimization procedures for other porous electrode materials.