Introducing oxygen vacancies for improving the electrochemical performance of Co9S8@NiCo-LDH nanotube arrays in flexible all-solid battery-capacitor hybrid supercapacitors

In this work, rich oxygen vacancies are obtained in Co9S8@NiCo-LDH core-shell nanotube arrays (NTAs), which boost its electrochemical energy storage performance. The flexible carbon cloth (CC) supported Co9S8@NiCo-LDH NTAs are synthesized by situ growth and electrodeposition method. After reacting with NaBH4, the rich oxygen vacancies are generated in NiCo-LDH nanosheets to obtain Co9S8@oxygen vacancies-NiCo-LDH NTAs (Co9S8@OV-NiCo-LDH NTAs). These oxygen vacancies increase the charge transfer rate in the multi-level redox processes and make the electrochemical performance improve sharply. At a current density of 0.5 A g−1, the mass specific capacity of Co9S8@OV-NiCo-LDH NTAs is up to 1335 C g−1, which is more than four times higher than that of the untreated Co9S8@NiCo-LDH NTAs. In addition, with the prepared Co9S8@OV-NiCo-LDH core-shell NTAs as a positive electrode, along with the negative electrode of activated carbon (AC), a high-performance flexible all-solid battery-capacitor hybrid supercapacitors (HSC) device is assembled. The maximum energy density is up to 101.1 Wh kg−1 when the power density is 800 W kg−1.