Role of anions on structure and pseudocapacitive performance of metal double hydroxides decorated with nitrogen-doped graphene

Abstract

Electrochemical capacitors (EC) bear faster charge-discharge; however, their real applications are still on a long away due to lower capacitance and energy densities which mainly arise from simple surface charge accumulation or/and reaction. Here, a novel synthesis strategy was designed to obtain the purposeful hybrids of nickel cobalt double hydroxide (NiCoDH) with genetic morphology to improve their electrochemical performance as electrode of EC. Nanostructures of metal hydroxides were grown on t he nitrogen-doped graphene (NG) sheets by utilizing defects as nucleation sites and their composition was optimized both by tuning the ratio of Ni:Co as well as the counter halogen and carbonate anions to improve the porosity, stabilize the structure and mediate the redox reaction. The growth of the hybrids was guided by the Co ions through topochemical transformation supported by hoping charge transfer process and olation growth. NG overcoating successfully protects the nanostructure of NiCoDH during electrochemical test and enhances overall conductivity of the electrode, improving the mass and ionic transportations. As a result, the hybrid exhibits excellent capacitance of 2925 F g −1 at 1 A g −1 , as well as long cyclic stability of 10,000 cycles with good capacity retention of 90% at 16 A g −1 . Furthermore, the hybrid shows excellent energy and power densities of 52 Wh kg −1 and 3191 W kg −1 , respectively at discharge rate of 16 A g −1 . It is expected that this strategy can be readily extended to other metal hydroxides, oxides and sulphides to improve their electrochemical performances.

Binary NiCu layered double hydroxide nanosheets for enhanced energy storage performance as supercapacitor electrode

“…Nevertheless, experimentally the electrochemical properties of NiLDH such as specific capacitance and rate capability are normally unsatisfactory due to the poor conductivity and fragile crystalline structure of the material. One approach to solve this problem is through introduction of additional metal ions such as cobalt and aluminium to make binary LDH [13][14][15][16]. As an earth-abundant element, Cu based hydroxide materials recently received limited interest in application in SCs [17][18][19][20].…”

Novel Pliable Electrodes for Flexible Electrochemical Energy Storage Devices: Recent Progress and Challenges

“…[9] Flexible LIBs and SCs have the same charge storage mechanism as conventional LIBs or SCs and are popularly used in electronics, electric vehicles (EV) and hybrid electric vehicles (HEV). [10] Under external loadings, battery materials undergo mechanical deformations including bending, twisting, compressing and as well stretching, which can seriously affect the inherent structure of the electrode materials along with electrode/electrolyte transport properties. [11] Recently, good progress has been made in the development of core components of flexible LIBs and SCs (electrode materials, electrolytes and current collector).…”

Recent advancements in metal organic framework based electrodes for supercapacitors

“…Graphene and carbon nanotubes are widely investigated conductive fillers to the supercapacitor electrodes due to their superior electrical conductivity and large SSA [96,97]. Moreover, the two dimensional (2D) structure of graphene and one dimensional (1D) structure of carbon nanotubes can serve as the substrate due to the excellent mechanical and chemical stability.…”