First Introduction of NiSe2 to Anode Material for Sodium-Ion Batteries: A Hybrid of Graphene-Wrapped NiSe2/C Porous Nanofiber.

Jung Sang Cho,Yun Chan Kang,Seung Yeon Lee

doi:10.1038/srep23338

Abstract

The first-ever study of nickel selenide materials as efficient anode materials for Na-ion rechargeable batteries is conducted using the electrospinning process. NiSe2-reduced graphene oxide (rGO)-C composite nanofibers are successfully prepared via electrospinning and a subsequent selenization process. The electrospun nanofibers giving rise to these porous-structured composite nanofibers with optimum amount of amorphous C are obtained from the polystyrene to polyacrylonitrile ratio of 1/4. These composite nanofibers also consist of uniformly distributed single-crystalline NiSe2 nanocrystals that have a mean size of 27 nm. In contrast, the densely structured bare NiSe2 nanofibers formed via selenization of the pure NiO nanofibers consist of large crystallites. The initial discharge capacities of the NiSe2-rGO-C composite and bare NiSe2 nanofibers at a current density of 200 mA g−1 are 717 and 755 mA h g−1, respectively. However, the respective 100th-cycle discharge capacities of the former and latter are 468 and 35 mA h g−1. Electrochemical impedance spectroscopy measurements reveal the structural stability of the composite nanofibers during repeated Na-ion insertion and extraction processes. The excellent Na-ion storage properties of these nanofibers are attributed to this structural stability.

Highlights

The first-ever study of nickel selenide materials as efficient anode materials for Na-ion rechargeable batteries is conducted using the electrospinning process
Subsequent selenization of these composite nanofibers at 300 °C under H2Se gas gives rise to the NiSe2-reduced graphene oxide (rGO)-C composite nanofibers, in which NiSe2 nanocrystals are uniformly distributed throughout the rGO-C composite nanofibers
Porous-structured NiSe2-rGO-C composite nanofibers with appropriate amounts of amorphous C were prepared by optimizing the composition of the organic polymers used in the electrospinning process

Summary

Introduction

The first-ever study of nickel selenide materials as efficient anode materials for Na-ion rechargeable batteries is conducted using the electrospinning process. In one of the few studies conducted, Ko et al used a spray pyrolysis process to fabricate yolk-shell-structured MoSe2 microspheres as an anode material for NIBs; these microspheres delivered a 50th-cycle discharge capacity of 433 mA h g−1 at a current density of 0.2 A g−1 27. To the best of our knowledge, nickel selenide (NiSe2) materials have not been investigated as anode materials for NIBs. Electrospinning is a simple and highly versatile method used for the preparation of one-dimensional nanostructures of various compositions[29,30,31,32]. In this study, NiSe2-reduced graphene oxide (rGO)-carbon composite porous nanofibers were prepared via an electrospinning and subsequent selenization process. The composite nanofibers composed of Ni salt, GO nanosheets, polystyrene (PS), and polyacrylonitrile (PAN) were transformed into the NiSe2-rGO-C composite nanofibers by using a simple selenization process

Methods

Results

Conclusion