Flexible Conductive Anodes Based on 3D Hierarchical Sn/NS-CNFs@rGO Network for Sodium-Ion Batteries

Abstract

HIGHLIGHTS • 3D hierarchical conductive Sn quantum dots encapsulated in N,S co-doped carbon nanofibers sheathed within rGO scrolls (Sn/NS-CNFs@rGO) were prepared through an electrospinning process. • Flexible Sn/NS-CNFs@rGO electrode exhibits superior long-term cycling stability and high-rate capability in sodium-ion batteries. ABSTRACT Metallic Sn has provoked tremendous progress as an anode material for sodium-ion batteries (SIBs). However, Sn anodes suffer from a dramatic capacity fading, owing to pulverization induced by drastic volume expansion during cycling. Herein, a flexible three-dimensional (3D) hierarchical conductive network electrode is designed by constructing Sn quantum dots (QDs) encapsulated in one-dimensional N,S codoped carbon nanofibers (NS-CNFs) sheathed within two-dimensional (2D) reduced graphene oxide (rGO) scrolls. In this ingenious strategy, 1D NS-CNFs are regarded as building blocks to prevent the aggregation and pulverization of Sn QDs during sodiation/desodiation, 2D rGO acts as electrical roads and "bridges" among NS-CNFs to improve the conductivity of the electrode and enlarge the contact area with electrolyte. Because of the unique structural merits, the flexible 3D hierarchical conductive network was directly used as binder-and current collectorfree anode for SIBs, exhibiting ultra-long cycling life (373 mAh g −1 after 5000 cycles at 1 A g −1), and excellent high-rate capability (189 mAh g −1 at 10 A g −1). This work provides a facile and efficient engineering method to construct 3D hierarchical conductive electrodes for other flexible energy storage devices.

In‐plane Defect Engineering Enabling Ultra‐stable Graphene Paper‐based Hosts for Lithium Metal Anodes

“…The result is also in accordance with that of XRD patterns. In Figure 2(e, f) and Figure S6(b, c), the C 1s peak shows the coexistence of three major characteristic peaks at about 284.84, 286.94 and 288.55 eV, which agree with C−C, C−O and O−C=O functional groups, respectively [44,45] . However, the intensity of oxygen‐containing functional groups of sparked rGO, HrGO‐1, HrGO‐2 and HrGO‐4 films is lower than that of pristine GO, HGO‐1, HGO‐2 and HGO‐4 films, indicating that the oxygen‐containing functional groups are expelled by spark reaction.…”

Tin‐Based Anode Materials for Stable Sodium Storage: Progress and Perspective

“…Many efforts have focused on constructing 3D structures. [91,92] For instance, Chen et al [91] developed graphitic porous carbon nanocages (PCNCs) in which Sn nanoparticles were encapsulated by a template-assisted CVD and in-site reduction method. The PCNCs could restrict Sn particle aggregation and provide sufficient buffering space for volume expansion, as shown in Figure 8a.…”

“…Theoretical calculations showed that a strong bond forms between amorphous carbon black and Na 15 Sn 4 during cycling, which accelerates bare Sn electrode pulverization, whereas graphitic carbon layers in the electrodes show weak interactions with Na 15 Sn 4 and are more favorable to the cycling performance by preventing CNC‐Sn electrode pulverization. As a result, the PCNCs‐Sn exhibited a high reversible capacity of 828 mA h g −1 at 0.047 C and a long cycle life up to 1000 cycles even at 3 C. More recently, a flexible 3D hierarchical conductive network electrode that consists of 0D Sn quantum dots, 1D N, S‐doped carbon nanofibers and 2D RGO was designed (denoted Sn/NS‐CNFs@RGO) , [ 92 ] as shown in Figure 8e. Because of the restriction and buffering effects of NS‐CNFs and RGO materials, severe Sn particle agglomeration and volume changes during cycling were hindered.…”

“…e) TEM image and schematic illustration of enhanced transport mechanism of Na + and e − ; f) rate performance; and g) long-term cycle stability at a current density of 1000 mA g −1 . e-g) Reproduced under the terms of the CC-BY Creative Commons Attribution 4.0 International license (https://creativecommons.org/licenses/by/4.0) [92]. Copyright 2019, The Authors, published by Springer Nature.…”

3D Carbon Networks: Design and Applications in Sodium Ion Batteries

“…At present, the multiphase nanocomposites prepared by encapsulation strategies were expected to be of satisfactory reversible capacity. As shown in Figure 11A(a–b), a flexible 3D hierarchical composite membrane electrode (Sn/NS‐CNFs@rGO) has been fabricated with Sn NPs encapsulated in N,S co‐doped CNFs sheathed within rGO scrolls [99b] . The introduction of N and S atoms in CNFs brings more defects, which help enhance electronic conductivity and offer more active sites for storage of sodium ions.…”