Nitrogen-doped CNT on CNT hybrid fiber as a current collector for high-performance Li-ion capacitor

By Kanakaraj, Sathya Narayan; Hsieh, Yu-Yun; Adusei, Paa Kwasi; Homan, Bradley; Fang, Yanbo; Zhang, Guangqi; Mishra, Siddharth; Gbordzoe, Seyram; Shanov, Vesselin
Published in Carbon 2019

Abstract

In this work, we describe a scalable synthesis process of binder-free, nitrogen-doped carbon nanotubes (CNTs) on CNT fibers combining a solvothermal process with chemical vapor deposition (CVD). Li4Ti5O12 was selected as an example active material to evaluate the performance of the obtained current collector electrode, which achieved capacity retention after 1000 cycles at a 15C rate and a stable specific capacity of 144 mAhg?1 at 5C. We also report here the fabrication of an asymmetrical hybrid capacitor that exhibited a maximum specific energy of 0.296 mWhcm?2/0.019 Whcm?3/68 Whkg?1 at a specific power of 0.172 mWcm?2/0.011 Wcm?3/126 Wkg-1. It maintained specific capacitance of 0.0779 mWhcm?2/0.005 Whcm?3/17 Whkg?1 at a high specific power of 57.05 mWcm?2/3.719 Wcm?3/12,500 Wkg-1. The device exhibited a very stable cycling performance, retaining of its specific energy after 2000 cycles at 4 Ag-1 current density. The increase in specific power, energy and cycling performance was attributed to the porous network afforded by the nitrogen-doped CNTs and their strong binding with the active material Li4Ti5O12. The porous network enabled fast Li-ion diffusion paths while the pristine CNT allowed for fast electron transfer all in a fiber format, making it attractive as an electrode for wearable energy storage devices.

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