Flexible aqueous asymmetric capacitor with SiC-decorated boron-doped graphene cathode and core–shell SiC@graphene anode

Abstract

• Core-shell SiC@graphene (Gr) nanoparticles were synthesized as an anode material. • B-doped graphene (BGr) nanosheets embedded with SiC nanoparticles were synthesized. • SiC-BGr electrocatalyzed the NiOOH/NiO redox reaction to improve pseudocapacitance. • SiC-BGr cathode showed the maximum specific capacitance of 1803 mF cm −2 at 4 mA cm −2 . • Aqueous SiC-BGr//SiC@Gr capacitor showed high working voltage and stability. Flexible aqueous pseudocapacitors have the advantages of high specific capacitance, high safety, low cost, and fast ion diffusion. However, the development of such devices is a challenge because of the low stability of the active material and the high interface resistance of the current collector-active material. In this study, we used silicon carbide (SiC)-boron-doped graphene (BGr) nanosheets and core–shell SiC@Gr nanoparticles as the cathode and anode, respectively, and constructed a flexible aqueous asymmetric capacitor (ASC) with a 3 M NaOH/carboxymethyl cellulose hydrogel as the electrolyte. In an aqueous NaOH solution, the optimized SiC-BGr cathode showed a specific capacitance of 1384.3 mF cm −2 (461.4 F g −1 ) at the current density of 3 mA cm −2 (1 A g −1 ), and the core–shell SiC@Gr anode showed a wide potential window of −1.0–0 V. The as-assembled ASC device had a high working voltage of 1.4 V, delivered an excellent capacitance of 337.1 mF cm −2 , and retained 86% of its initial capacitance after 10 000 cycles. Furthermore, the ASC also showed high energy density (57.3 μWh cm −2 ), high power density (6536.9 μW cm −2 ), high bending stability, and applicability at a low temperature of −20 °C. Thus, the preparation of novel SiC-Gr materials can promote the development of flexible aqueous capacitors with high working voltage and good temperature adaptability for application in the field of wearable electronic devices with safety, strong environmental adaptability, and reliable performance.