MXene-Coated Nickel Ion-Exchanged ZIF Skeleton-Cavity Layered Double Hydroxides for Supercapacitors
Xing Chen, Kunyan Wang, Kun Xie, Haijun Tao, Yuqiao Wang
Abstract
A NiCo layered double hydroxide (LDH) has been regarded as a promising electrode material for supercapacitors. However, the low electronic conductivity, limited electroactive sites, and self-agglomeration hinder its large-scale application. Herein, MXene-coated nickel ion-exchanged ZIF skeleton-cavity LDHs (ZSC-LDH@MXene) were fabricated to enhance the electrochemical performance of NiCo LDHs. The ZSC-LDH@MXene integrated the advantages of various materials, providing abundant metal active sites and fast redox reaction kinetics and enhancing the specific capacity of the electrode. The MXene nanosheets can construct abundant conductive networks, enhancing the electronic conductivity of the NiCo LDH. The nanosheet-assembled ZIF skeleton-cavity structure can facilitate electron/ion transport, enlarge the electrolyte accessibility, and expose abundant electroactive sites. Furthermore, the hollow cavity can relieve the volume expansion during the charging/discharging cycles. Ultimately, the as-obtained ZSC-LDH@MXene electrode manifested a large specific capacity of 1029.6 C g–1 at 1 A g–1, a superior rate capability of 62.6% at 30 A g–1, as well as outstanding cycling performance with a 92.0% capacity retention at 10 A g–1 over 10,000 cycles. The assembled ZSC-LDH@MXene//AC hybrid supercapacitor exhibited a superb energy density of 43.7 W h kg–1 at 789 W kg–1.