High‐Performance Flexible Freestanding Anode with Hierarchical 3D Carbon‐Networks/Fe₇S₈/Graphene for Applicable Sodium‐Ion Batteries

Abstract

Sodium‐ion batteries (SIBs) have gained tremendous interest for grid scale energy storage system and power energy batteries. However, the current researches of anode for SIBs still face the critical issues of low areal capacity, limited cycle life, and low initial coulombic efficiency for practical application perspective. To solve this issue, a kind of hierarchical 3D carbon‐networks/Fe7S8/graphene (CFG) is designed and synthesized as freestanding anode, which is constructed with Fe7S8 microparticles well‐welded on 3D‐crosslinked carbon‐networks and embedded in highly conductive graphene film, via a facile and scalable synthetic method. The as‐prepared freestanding electrode CFG represents high areal capacity (2.12 mAh cm−2 at 0.25 mA cm−2) and excellent cycle stability of 5000 cycles (0.0095% capacity decay per cycle). The assembled all‐flexible sodium‐ion battery delivers remarkable performance (high areal capacity of 1.42 mAh cm−2 at 0.3 mA cm−2 and superior energy density of 144 Wh kg−1), which are very close to the requirement of practical application. This work not only enlightens the material design and electrode engineering, but also provides a new kind of freestanding high energy density anode with great potential application prospective for SIBs.

Promoting Highly Reversible Sodium Storage of Iron Sulfide Hollow Polyhedrons via Cobalt Incorporation and Graphene Wrapping

“…For S 2p spectra (Figure e), a pair of peaks at lower binding energy (blue color) correspond to the sulfide (S 2− ), and those at higher binding energy (purple color) are related to the S n 2− , which may be generated by the minor oxidation of S 2− . Additionally, the weak and broad peak at 168 eV (orange color) should correspond to the sulfur species at higher oxidation state (SO x ) . For CoFeS@rGO composite, an obvious peak of Co 2p indicates the successful Co substitution in iron sulfide (Figure S8b, Supporting Information).…”

“…c) Rate performances at various current densities. d) Rate comparison between CoFeS@rGO and reported iron sulfide‐based electrodes . e) Long‐term cycling performance at 1000 mA g −1 .…”

General and Scalable Fabrication of Core–Shell Metal Sulfides@C Anchored on 3D N‐Doped Foam toward Flexible Sodium Ion Batteries

“…Thereafter, it is proposed to further optimize the electrochemical performances by constructing self‐standing and binder‐free TMSs/carbon nanocomposites grown on conductive backbones. Recently, flexible free‐standing Fe 1‐ x S@PCNWs/rGO and carbon/Fe 7 S 8 /graphene anodes exhibit high capacities and excellent cycle stabilities. Unfortunately, these composites are generally prepared by a complicated and tedious process.…”

Hollow Structure VS2@Reduced Graphene Oxide (RGO) Architecture for Enhanced Sodium‐Ion Battery Performance

“…[11,12] In addition, SIBs have similar chemistry intercalation mechanism with LIBs, which are based on the reversible Na ions intercalation/deintercalation in the positive and negative electrodes during discharge and charge process. [13,14] Generally, favorable anode materials with long life, great cycling stability and high rate performance, are the most important factors for the commercial development of SIBs. [15] Up to now, several materials have been devoted to improve the outstanding electrochemical properties of anode materials in SIBs, including carbon-based materials, alloy materials and transition metal-based materials.…”