Tunable and scalable synthesis of hierarchical porous nanocarbon/sulfur composite cathodes

Abstract

Hierarchical porous carbon nanofiber / sulfur composites (HPCNF / S), useful in the manufacture of lithium sulfur batteries are formed of a cathode having a hierarchical porous carbon nanofiber / sulfur (HPCNF / S) composite, a conductive additive, polyvinylidene fluoride binder and a foil current collector. The HPCNF is formed by electrospinning polyacrylonitrile / iron (III) acetylacetonate neat fibers from polymer precursor, stabilizing, carbonizing and acid etching to form porous CNFs, effecting chemical activation of porous CNF to form hierarchical porous carbon nanofibers (HPCNFs) and effecting encapsulation of sulfur in pores of HPCNFs by melt-diffusion. When used as a battery, the HPCNF / Scomposite functions as a cathode.

Description

[0001] Related application [0002] This patent application claims the priority of provisional patent application No. 62 / 493462 filed on July 6, 2016, which is assigned to the assignee of this application and submitted by the inventor, and its content is incorporated by reference Into this article. Technical field [0003] The invention relates to the synthesis of hierarchical porous carbon nanofibers (HPCNF) and a method for preparing hierarchical porous carbon nanofiber / sulfur (HPCNF / S) composite materials. In particular, the present disclosure relates to the application of HPCNF / S composite material as a cathode in a rechargeable lithium-sulfur battery (LSB). Background technique [0004] The ever-growing portable electronic device market requires energy storage systems with high energy / power density, long cycle performance, low cost and environmentally friendly characteristics. Among many electrochemical energy storage devices, lithium-ion batteries have occupied the electroni...

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Problems solved by technology

[0010] 1. CNFs evolved from direct carbonization of electrospun polymer precursors often exhibit poor electrical conductivity due to their lower degree of graphitization

[0011] 2. In addition, the vast majority of pores generated in CNFs are completely open or completely closed, which makes it difficult to control the diffusion of lithium polysulfides or the introduction of sulfur particles

[0012] 3. The sulfur loading in most sulfur / CNF composites is below 70 wt%

[0013] 4. It is difficult for the reported sulfur / CNF composite electrodes to achieve high rate performance and high power output at high current density

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