Design of Flexible Films Based on Kinked Carbon Nanofibers for High Rate and Stable Potassium-Ion Storage

Abstract

With the emergence of wearable electronics, flexible energy storage materials have been extensively studied in recent years. However, most studies focus on improving the electrochemical properties, ignoring the flexible mechanism and structure design for flexible electrode materials with high rate capacities and long-time stability. In this study, porous, kinked, and entangled network structures are designed for highly flexible fiber films. Based on theoretical analysis and finite element simulation, the bending degree of the porous structure (30% porosity) increased by 192% at the micro-level. An appropriate increase in kinking degree at the meso-level and contact points in entanglement network at the macro-level are beneficial for the flexibility of fiber films. Therefore, a porous and entangled network of sulfur-/nitrogen-co-doped kinked carbon nanofibers (S/N-KCNFs) is synthesized. The nanofiber films synthesized from melamine as nitrogen sources and segmented vulcanization exhibited a porous, kinked, and entangled network structure, and the stretching degree increased several times. The flexible S/N-KCNFs anode delivered a higher rate performance of 270 mAh g−1 at a current density of 2000 mA g−1 and a higher capacity retention rate of 93.3% after 2000 cycles. Moreover, the foldable pouch cell assembled by potassium-ion hybrid supercapacitor operated safely at large-angle bending and showed long-time stability of 88% capacity retention after 4000 cycles. This study provides a new idea and strategy for the flexible structure design of high-performance potassium-ion storage materials.

Stabilizing intermediate phases via the efficient confinement effects of the SnS2-SPAN fibre composite for ultra-stable half/full sodium/potassium-ion batteries

“…It is, therefore, a momentous breakthrough to design state-ofthe-art anode materials with simultaneous high energy density and long service life for SIBs and PIBs. [15][16][17][18][19] Considering the unique layered structure and high theoretical capacity of transition metal dichalcogenides (TMDs), [20][21][22] SnS 2 has garnered extensive interest due to its profoundly high theoretical capacity (1136 mA h g À1 ) and large interlayer distance (0.59 nm). This predominance makes SnS 2 stand out among anode materials for SIBs/PIBs.…”

“…It is, therefore, a momentous breakthrough to design state-of-the-art anode materials with simultaneous high energy density and long service life for SIBs and PIBs. 15–19…”

Dimensional engineering of anode materials for high performance potassium ion hybrid capacitor—A review

“…Second, the high aspect ratio geometry enables 1D nanostructured materials to be crosslinked into different high‐dimensional networks and to form flexible materials for wearable PIHC devices 47,48 . Among them, 1D nanostructured materials deposited on a 2D plane to form regular array structures have been studied extensively recently, including ZnO, CuO, Zn‐Ni‐Co oxide (ZNCO), etc 49‐52 .…”

“…46 Second, the high aspect ratio geometry enables 1D nanostructured materials to be crosslinked into different high-dimensional networks and to form flexible materials for wearable PIHC devices. 47,48 Among them, 1D nanostructured materials deposited on a 2D plane to form regular array structures have been studied extensively recently, including ZnO, CuO, Zn-Ni-Co oxide (ZNCO), etc. [49][50][51][52] 1D nanostructured materials allow the electrolyte to penetrate into the electrode materials more easily, thus promoting charge transfer and obtaining higher power and so on.…”

Reversible Oxygen-Rich Functional Groups Grafted 3D Honeycomb-Like Carbon Anode for Super-Long Potassium Ion Batteries

“…Potassium-ion batteries (PIBs) have been identified as the next generation of large-scale commercial electric energy storage systems due to the cheap potassium salts, lavish potassium resources, and high energy density [1][2][3][4]. Nevertheless, the sluggish diffusion kinetics of K + and the degradation of the structure due to the large radius of potassium (0.138 nm) hinder the development of anode electrodes of PIBs [5][6][7][8][9].…”