Ce3+ ion regulated CoNi-hydroxides for ultrahigh charge rate supercapacitors

Abstract

Due to the enlarged interlayer spacing of anion-inserted hydroxides and their increased surface area, the unique structure of double-layered hydroxides is often beneficial for electrochemical energy storage. This work demonstrates that Ce³⁺-regulated CoNi-layered double hydroxides (CoNi-LDHs) significantly enhance the kinetics of electron transfer and ion motion with increased layer positive charges and weakened O–H bonds. The Ce³⁺ addition enabled a high rate capacitance of 1000 F g⁻¹ at an ultrahigh charge rate of 50 A g⁻¹ compared with 1322 F g⁻¹ at 1 A g⁻¹. Served as Lewis acid sites, the substituting trivalent Ce³⁺ for Co²⁺ decreases the energy barrier of proton diffusion and promotes the fast charge storage kinetics by increasing the hole carrier concentration (6.74 × 10²⁴ cm⁻³). The fabricated supercapacitor device achieves a high energy density of 30 W h kg⁻¹ at a power density of 10 kW kg⁻¹ (40 A g⁻¹) based on the total mass of active materials. This work simultaneously enhanced intrinsic electronic conductivity and ion diffusion in an electrode by Ce³⁺ addition.