Facile assembly of cobalt-nickel double hydroxide nanoflakes on nitrogen-doped hollow carbon spheres for high performance asymmetric supercapacitors

Abstract

Cobalt-nickel double hydroxide has high theoretical specific capacity and electrochemical activity but undergoes poor rate performance and cycle stability. Herein, cobalt-nickel double hydroxide/nitrogen-doped hollow carbon spheres (CoNi-DH/NHCS) hybrids with a hollow structure were fabricated via a simple deposition method at room temperature. Structural analysis confirmed that ultrathin CoNi-DH nanosheets with hydrotalcite structure were grown on the surface of NHCS. The presence of NHCS can adapt to volume changes during repeated charge-discharge procedures and improve stability. In addition, owing to the accelerated ions diffusion in the ultrathin nanosheets and improved conductivity, the electrode with a cobalt content of 15% presents the highest specific capacity (578 C g −1 at 1 A g −1 ) as well as brilliant rate capacity (76.54%, 1–20 A g −1 ). The all-solid-state asymmetric supercapacitor 15CoNi-DH/NHCS‖NHCS depicts a superior energy density of 27.51 Wh kg −1 at 800 W kg −1 as well as distinguished cycle stability of 91.65% reservation after 10000 cycles. • CoNi-DH/NHCS hybrids were obtained by a facile deposition method. • The hollow structure can adapt to volume changes during charge-discharge procedure. • A specific capacity of 578 C g −1 was obtained for the CoNi-DH/NHCS at 1 A/g. • The asymmetric supercapacitor delivers high stability of 91.65% after 10,000 cycles.