Enhancing cycling stability of transition metal-based layered double hydroxides through a self-sacrificial strategy for hybrid supercapacitors

Transition metal-based layered double hydroxides (LDH) are attractive electrode materials for super-capacitors (SCs) owing to their advantage of high theoretical specific capacity. However, the material structure of most LDHs fails to sustain long charge/discharge cycling of the device, leading to a short lifespan. Herein, we demonstrate a self-sacrificial strategy to boost the cyclability of Ni-Co LDH nano-sheet arrays for SCs by using electrochemically inert Zn cation as a sacrificial agent (Zn-Ni-Co LDH). At an optimal content of Zn incorporation, a maximum specific capacity of 231.7 mAh g(-1) (at 1 A g(-1)) and a capacity increment of over 500% after 20, 000 charge/discharge cycling test at 20 A g(-1) have been obtained. For practical application, a hybrid SC based on Zn-Ni-Co LDH material demonstrated a high energy density of 40.3 Wh kg(-1) and a high power density of 16.1 kW kg(-1), along with extraordinary cycling stability of over 20, 000 cycles. Measurements by ex-situ synchrotron X-ray absorption spectroscopy (XAS) and other characterization techniques like EDS and TEM have shown a gradual loss of Zn from the electrode during the charge/discharge process, which not only helps to create free space to maintain the material microstructure but also exposes more active sites for electrochemical reaction. The findings in this work provide new avenues towards the fabrication of robust electrode materials for advanced SCs with both high energy density and cycling stability. (C) 2019 Elsevier Ltd. All rights reserved.