Pitch-derived soft carbon composite with hard carbon fibers for high-rate and long-cycling K+storage

沥青衍生软碳与硬碳纤维复合实现高倍率和长循环的K+存储

Potassium-ion batteries(KIBs)have been seen as a competitive alternative to lithium-ion batteries(LIBs)due to their natural abundance,low cost and rocking chair-like operating mechanism similar to LIBs.Soft carbon has a lower voltage plateau compared to hard carbon and an easily modulated lattice structure compared to graphite,which provides particular advantages in KIBs anodes.Pitch has attracted much attention as a simple,readily available and inexpensive precursor for soft carbon,but its structure is easily damaged during cycling.Herein,the flexible film Pitch@CNF are prepared by uniformly winding reticulated carbon fibers on the surface of pitch-soft carbon via electrostatic spinning technique,which not only enables the pitch to maintain its structure well during cycling and withstand the volume expansion upon K+insertion,but also is conducive to ionic transport of the three-dimensional reticulated structure.Meanwhile,the abundant pores on the carbon fibers can provide more K+active sites.The prepared flexible self-supporting films can be used directly as electrodes without the addition of binders and conductive agents.The reversible capacity is 290 mAh·g^(-1)at a current density of 0.1 A·g^(-1),and the capacity retention rate is 83%after 500 cycles.

钾离子电池(KIBs)因其天然丰富的资源、较低的成本以及与锂离子电池类似的摇椅式运行机制,一直被视为锂离子电池(LIBs)的替代品.作为KIBs负极,软碳与硬碳相比电压平台更低,与石墨相比晶格结构易于调节.沥青作为一种简单、易于获得且价格低廉的软碳前体备受关注,但其结构在循环过程中很容易受到破坏.文中通过静电纺丝技术在沥青软碳表面均匀缠绕网状碳纤维,制备了柔性薄膜Pitch@CNF,其不仅使沥青在循环过程中能很好地保持结构,缓解K+插层时的体积膨胀,而且三维网状结构有利于离子传输,碳纤维上丰富的孔隙能提供更多的K~+活性位点.制备的柔性自支撑薄膜可直接用作电极,无需添加粘合剂和导电剂.在电流密度为0.1 A·g^(-1)时,可逆容量为290 m Ah·g^(-1),循环500次后容量保持率为83%.