Vertically Aligned NiCo2O4 Nanosheet-Encapsulated Carbon Fibers as a Self-Supported Electrode for Superior Li+ Storage Performance.

Yongchao Liu,Qinglong Jiang,Jintian Jiang,Yanyan Yuan,Chao Yan

doi:10.3390/nano9091336

Abstract

Binary transition metal oxides (BTMOs) have been explored as promising candidates in rechargeable lithium-ion battery (LIB) anodes due to their high specific capacity and environmental benignity. Herein, 2D ultrathin NiCo2O4 nanosheets vertically grown on a biomass-derived carbon fiber substrate (NCO NSs/BCFs) were obtained by a facile synthetic strategy. The BCF substrate has superior flexibility and mechanical strength and thus not only offers a good support to NCO NSs/BCFs composites, but also provides high-speed paths for electron transport. Furthermore, 2D NiCo2O4 nanosheets grown vertically present a large contact area between the electrode and the electrolyte, which shortens the ions/electrons transport distance. The nanosheets structure can effectively limit the volume change derived from Li+ insertion and extraction, thus improving the stability of the electrode material. Therefore, the synthesized self-supporting NCO NSs/BCFs electrode displays excellent electrochemical performance, such as a large reversible capacity of 1128 mA·h·g−1 after 80 cycles at a current density of 100 mA·g−1 and a good rate capability of 818.5 mA·h·g−1 at 1000 mA·g−1. Undoubtedly, the cheap biomass carbon source and facile synthesis strategy here described can be extended to other composite materials for high-performance energy-storage and conversion devices.

Highlights

The use of renewable clean energy has promoted the development of energy storage systems (ESSs), especially rechargeable lithium-ion batteries (LIBs), which are widely used in smart appliances, medical devices, and urban buses due to their long life cycle, high power density, and environmental friendliness [1–3]
We developed a facile strategy to fabricate a film substrate from biomass-derived carbon fibers (BCFs) using a plant fiber mask as a carbon source and a two-step heat treatment
A metal lithium foil was employed as a reference and counter electrode, a microporous membrane (Gelgard 2500) was used as the separator, and the electrolyte was composed of 1 M LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC)/diethyl carbonate (DEC) (1:1:1, vol%)

Summary

Introduction

The use of renewable clean energy has promoted the development of energy storage systems (ESSs), especially rechargeable lithium-ion batteries (LIBs), which are widely used in smart appliances, medical devices, and urban buses due to their long life cycle, high power density, and environmental friendliness [1–3]. High-flexibility self-supported electrodes have been obtained by replacing the metal conductive substrates with carbon fiber cloth. The plant fiber mask has excellent elasticity and is an artificial product of various plant fibers characterized by good electrical conductivity and flexibility after carbonization It is an ideal conductive substrate material for energy storage electrodes. The remarkable performances are mainly attributed to the synergistic properties of ultrathin 2D NiCo2O4 nanosheets and highly conductive and flexible BCF substrate, providing ready access pathways for rapid Li+ diffusion, excellent mechanical strength, and good stability. This work highlights an interesting strategy for the rational preparation of low-cost, highly flexible, biomass-derived carbon fiber substrates and 2D ultrathin nanosheets for self-supported, flexible electrode materials (NCO NSs/BCFs) for high-performance LIBs

Synthesis of a Biomass-Derived Carbon-Fiber Film

Characterization Methods

Electrochemical Measurement

Results and Discussion