Oxygen-vacancy-rich cobalt–aluminium hydrotalcite structures served as high-performance supercapacitor cathode

Abstract

The combination of large energy density and high power density is the optimized model for supercapacitors. However, due to the sluggish charge transfer and ion diffusion, cobalt-aluminium hydrotalcite (CoAl LDHs) electrode materials currently deliver barely satisfactory performance. Oxygen vacancies have been reported to have positive facilitation to the electrochemical property of the hydrotalcite-like materials. In this work, the proportion of oxygen vacancies in CoAl LDHs was increased by NaBH₄ treatment, which improved the electrochemical energy storage performance of pristine CoAl LDHs, while prolonged treatment will damage the internal structure of the material and is not conducive to the improvement of electrochemical performance. Consequently, the acquired CoAl LDHs-0.5 delivers a high specific capacity of 799.2 F g⁻¹ at a current density of 1 A g⁻¹ and maintains 81.1% capacity as the current density up to 20 A g⁻¹, which exhibited higher performance than pristine CoAl LDHs and the most reported CoAl LDH-based materials. Besides, the asymmetric supercapacitor (ASC) was fabricated using CoAl LDHs-0.5 and commercial activated carbon (AC) as the positive and negative electrodes, respectively, which exhibits a maximum energy density of 28.9 W h kg⁻¹ at a power density of 523.5 W kg⁻¹ and retains 73.3% of the initial capacity after 5000 cycles at a current density of 5 A g⁻¹. This work provides an ingenious strategy and builds confidence in the further application of CoAl LDHs in electrode materials of supercapacitors.