First exploration of freestanding and flexible Na_2+2xFe_2−x(SO₄)₃@porous carbon nanofiber hybrid films with superior sodium intercalation for sodium ion batteries

Abstract

The design of a freestanding electrode is the key to the development of energy storage devices with superior electrochemical performance and mechanical durability. Herein, we propose a highly-scalable strategy for the facile synthesis of a freestanding alluaudite NaFe(SO)@porous carbon-nanofiber hybrid film, which is used as a self-supported and flexible electrode for sodium ion batteries. By the combined use of electrospinning and electrospraying, the freestanding hybrid film is constructed in the form of sulfate nanoparticles enwrapped in highly porous graphitic-like carbon-nanofibers. The multimodal porous architecture of the freestanding hybrid film ensures its superiority in mechanical flexibility and structural stability during repeated electrochemical processes, which meets the long-standing challenge of practical application. Moreover, both the highly conductive and porous framework and the nanoscale particles are favorable for promoting fast electron/ion transport capability. Compared with other carbon based supports such as graphene (GA), carbon nanotubes (CNTs) and active carbons (ACs), the flexible carbon nanofiber shows better interaction with electrochemical active materials and superior electrochemical properties. It retains over 95% of the capacity after five hundred cycles at alternate rates of 40C and 5C, which demonstrates the superior ultralong time and high-rate cycling capability. Therefore, the present work provides a facile and highly scalable strategy for the design and fabrication of high-performance freestanding sulfate cathodes for advanced sodium ion batteries.

1D Nanomaterials: Design, Synthesis, and Applications in Sodium–Ion Batteries

“…Copyright 2017, Wiley‐VCH. e–h) Schematic of the synthetic approach for Na 2 + 2 x M 2 x (SO 4 ) 3 @PCNF hybrid film . Copyright 2016, Royal Society of Chemistry.…”

“…Among sulfate‐based materials, the alluaudite‐type Na 2 Fe 2 (SO 4 ) 3 have gained extensive attention due to its higher operating potential with 3.8 V (vs Na + /Na) and high theoretical energy density . Deng and co‐workers explored the off‐stoichiometric member of Na 2 + 2 x Fe 2 − x (SO 4 ) 3 . They constructed Na 2 + 2 x Fe 2 − x (SO 4 ) 3 @porous carbon nanofibers (PCNF) hybrid film by combining electrospinning with electrospraying method.…”

Recent Advances in Nanowire‐Based, Flexible, Freestanding Electrodes for Energy Storage

“…[14] To generate porosity,t emplate molecules, such as small organic molecules,i norganic molecules and metal-organic frameworks (MOFs), are commonlya dded to the precursor solution. [13,15] MOF templates, during the sintering process, can form ac ombination of macro-,m eso-,a nd micropores in the fiber. [13,15] MOF templates, during the sintering process, can form ac ombination of macro-,m eso-,a nd micropores in the fiber.…”

Flexible Na batteries

“…D, Flexible Na-based electrolytes collector surface, making them very rigid and bulky. 36 This F I G U R E 2 Flexible cathodes for flexible Na batteries. The commonly used cathode materials in NIBs, particularly transition metal oxides, should be prepared though a hightemperature (>850 C) quenching process in air or an inert gas environment.…”