Enhancing heterojunction interface charge transport efficiency in NiCo-LDHs@Co/CoO-CNFs for high-performance asymmetric and zinc-ion hybrid supercapacitors

Abstract

The lack of active groups and poor dispersion of pristine carbon substrates lead to their inability to composite with other materials effectively, so that the electron transfer between them is inefficient. Therefore, in order to design carbon-based composites with high conductivity and electrochemical properties, the electron transfer between them must be enhanced first. Herein, the Co/CoO quantum dots doped carbon nanofiber (Co/CoO–CNF) materials with mesopore, high degree of graphitization and mechanical flexibility are synthesized via an electrospinning method. Then, ultrathin NiCo-LDHs are uniformly loaded on the Co/CoO-CNFs in situ to form NiCo-LDHs@Co/CoO-CNFs. Benefiting from the Fermi energy level difference and heterointerface between Co/CoO-CNFs (E_F = −4.44 eV) and NiCo-LDHs (E_F = −2.12 eV), electrons can be tansfered rapidly from NiCo-LDHs to Co/CoO-CNFs during the electrochemical reaction, so that NiCo-LDHs@Co/CoO-CNFs exhibit the excellent specific capacitance of 2055 F g⁻¹ at 1 A g⁻¹. When using in a flexible asymmetric supercapacitor, NiCo-LDHs@Co/CoO-CNFs shows a high energy density of 54.0 W h kg⁻¹ at 760.0 W kg⁻¹. Furthermore, assembled as the Zn-ion hybrid supercapacitor, NiCo-LDHs@Co/CoO-CNFs can also display an ultra-high energy density of 108 W h kg⁻¹ at 914.8 W kg⁻¹, as well as outstanding work durability (the capacitance of 98.2 % after 10,000 cycles).