Controllable synthesis of nickel bicarbonate nanocrystals with high homogeneity for a high-performance supercapacitor

Abstract

The electrochemical performance of supercapacitors might be associated with the homogeneous structure of the electrode materials. However, the relationship between the degree of uniformity for the electrode materials and the electrochemical performance of the supercapacitor is not clear. Herein, we synthesize two types of nickel bicarbonate nanocrystals with different degrees of uniformity to investigate this relationship. As the electroactive material, the nickel bicarbonate nanocrystals with a homogeneous structure could provide a larger space and offer more exposed atoms for the electrochemical reaction than the nanocrystals with a heterogeneous structure. The homogeneous nickel bicarbonate nanocrystals exhibit better electrochemical performance and show excellent specific capacitance (1596 F g at 2 A g and 1260 F g at 30 A g), which is approximately twice that of the heterogeneous nickel bicarbonate nanocrystals. The cycling stability for the homogeneity (∼80%) is higher than the inhomogeneity (∼61%) at a high current density of 5 A g.

One-Step Polyoxometalates-Assisted Synthesis of Manganese Dioxide for Asymmetric Supercapacitors with Enhanced Cycling Lifespan

“…Figure 4f shows the Nyquist plots of the MnO 2 in the frequency range from 10 −2 to 10 4 Hz. 51 All plots of S-3, S-4 and S-5 exhibited a semicircle connected to a straight line corresponding to high-frequency region and low-frequency region. From the partial enlarged images, it could be seen that the semicircle of S-3 was small compared with those of S-4 and S-5, which demonstrates that S-3 had fast charge transfer contributed to charge storage and electric conductivity processes.…”

“…Figure f shows the Nyquist plots of the MnO 2 in the frequency range from 10 –2 to 10 4 Hz . All plots of S-3, S-4 and S-5 exhibited a semicircle connected to a straight line corresponding to high-frequency region and low-frequency region.…”

Ni(HCO3)2 nanosheet/nickel tetraphosphate (Ni(P4O11)) nanowire composite as a high-performance electrode material for asymmetric supercapacitors

“…Since the function of asymmetric supercapacitors is dependent on their electrode materials, the development of new materials or improvement of the performance of existing materials have become viable strategies for achieving overall better performance of electrochemical capacitors [15]. Owing to their large theoretical specific capacity, high economic benefit and environmental compatibility, nickel compounds, especially Ni(HCO 3 ) 2 (denoted here as NiC) have been widely studied to obtain high-performance electroactive materials [16][17][18]. Notably, these works have often used NiC to construct composite electrodes with other materials such as conducting polymers, porous carbon spheres or graphene, which have favorable structures and excellent electrochemical performance [19][20][21].…”

Lithium effects on the mechanical and electronic properties of germanium nanowires

“…However, supercapacitors are more suitable for high power applications with long cycle lifes but at the cost of energy density [1]. The latter can be improved by changing conventional electrodes to nanostructured ones, without sacrificing their power capability and cyclability [4,5]. Ge has emerged as a promising Li-alloying material since bulk Ge has a high theoretical capacity of 1200 mAhg −1 [1,6], a working potential of 0.5 V with respect to the Li/Li + , it is electrically more conductive than silicon due to its small gap, and the Li diffusion is faster in comparison to bulk silicon [7][8][9][10].…”