Golden Bristlegrass‐Like Hierarchical Graphene Nanofibers Entangled with N‐Doped CNTs Containing CoSe<sub>2</sub> Nanocrystals at Each Node as Anodes for High‐Rate Sodium‐Ion Batteries
Min Su Jo, Jae Seob Lee, Sun Young Jeong, Sun Young Jeong, Jae‐Kwang Kim, Yun Chan Kang, Dong‐Won Kang, Sang Mun Jeong, Sang Mun Jeong, Jung Sang Cho
Abstract
Abstract Golden bristlegrass‐like unique nanostructures comprising reduced graphene oxide (rGO) matrixed nanofibers entangled with bamboo‐like N‐doped carbon nanotubes (CNTs) containing CoSe 2 nanocrystals at each node (denoted as N‐CNT/rGO/CoSe 2 NF) are designed as anodes for high‐rate sodium‐ion batteries (SIBs). Bamboo‐like N‐doped CNTs (N‐CNTs) are successfully generated on the rGO matrixed nanofiber surface, between rGO sheets and mesopores, and interconnected chemically with homogeneously distributed rGO sheets. The defects in the N‐CNTs formed by a simple etching process allow the complete phase conversion of Co into CoSe 2 through the efficient penetration of H 2 Se gas inside the CNT walls. The N‐CNTs bridge the vertical defects for electron transfer in the rGO sheet layers and increase the distance between the rGO sheets during cycles. The discharge capacity of N‐CNT/rGO/CoSe 2 NF after the 10 000th cycle at an extremely high current density of 10 A g −1 is 264 mA h g −1 , and the capacity retention measured at the 100th cycle is 89%. N‐CNT/rGO/CoSe 2 NF has final discharge capacities of 395, 363, 328, 304, 283, 263, 246, 223, 197, 171, and 151 mA h g −1 at current densities of 1, 2, 4, 6, 8, 10, 12, 14, 16, 18, and 20 A g −1 , respectively.