Interfacial Engineering of Nickel Boride/Metaborate and Its Effect on High Energy Density Asymmetric Supercapacitors

Abstract

Solid materials with special atomic and electronic structures are deemed desirable platforms for establishing clear relationships between surface/interface structure characteristics and electrochemical activity. In this work, nickel boride (Ni x B) and nickel boride/graphene (Ni x B/G) are chosen as positive materials of supercapacitors. The Ni x B/G displays higher specific capacitance (1822 F g–1) than that of Ni x B (1334 F g–1) at 1 A g–1, and it still maintains 1179 F g–1 at 20 A g–1, suggesting the high rate performance. The asymmetric supercapacitor device (Ni x B/G//activated carbon) also delivered a very high energy density of 50.4 Wh kg–1, and the excellent electrochemical performance is ascribed to the synergistic effect of Ni x B, Ni­(BO2)2, and graphene that fully enhances the diffusion of OH– and the electron transport. During the cycles, the prepared ultrafine Ni x B nanoparticles will be gradually in situ converted into β-Ni­(OH)2 which has a smaller particle size than that prepared by other methods. This will enhance the utilization of Ni­(OH)2 and decrease the ion diffusion distance. The electron deficient state of B in Ni­(BO2)2 amorphous shell will make it easy to accept extra electrons, enhancing the adsorption of OH– at the shell surface. Moreover, Ni­(BO2)2 makes strong adhesion between Ni x B (or β-Ni­(OH)2) and graphene and protects the core structure in a stable state, extending the cycle life. The above properties of Ni x B/G endow the electrode good capacitive performance.

2‐nm‐Thick NiCo LDH@NiSe Single‐Crystal Nanorods Grown on Ni Foam as Integrated Electrode with Enhanced Areal Capacity for Supercapacitors

“…The intersection on the real axis at the high‐frequency region is called equivalent series resistance ( R ESR ), which is the sum of ionic resistance of the electrolyte, inherent resistance of the active material and contact resistance at the active material/collector interface . The diameter of the semicircle is closely related to the charge transfer resistance ( R ct ) at the electrode material/electrolyte interface . The slightly tilted line at low‐frequency region represents the Warburg resistance ( Z w ), which is related to ion diffusion/migration in the electrolyte.…”

Metal–Organic Framework‐Derived Anode and Polyaniline Chain Networked Cathode with Mesoporous and Conductive Pathways for High Energy Density, Ultrafast Rechargeable, and Long‐Life Hybrid Capacitors

“…f) Ragone plot at different current densities compared with previous dual-carbon hybrid ion capacitors, [48,49] nonaqueous LICs, [50][51][52][53][54] and aqueous HES. [55][56][57][58][59][60] In addition, the galvanostatic measurements showed a linear increase of the specific capacity at the potential between 1.6 and 4.5 V ( Figure S24 and Table S6, Supporting Information), supporting that PANI@rGO could play as a high-rate and highcapacity cathode structure. Additionally, Figure S25, Supporting Information, shows that PANI@rGO leads to electrochemical stability without morphology change even after 10 000 times of charge-discharge cycles.…”

Rapid and Controllable Synthesis of Nanocrystallized Nickel‐Cobalt Boride Electrode Materials via a Mircoimpinging Stream Reaction for High Performance Supercapacitors

“…The generated borate‐containing Ni‐Co (oxy)‐hydroxides outer layers accelerated the adsorption of OH − and provided abundant active sites, while the conductive nanocrystallized Ni‐Co borides core provided effective charge transfer, which ensured the excellent supercapacitive performance of NCB composites. The possible reaction mechanism of NCB could be expressed as follows (using M 2+ instead of Ni 2+ /Co 2+ to simplify the equations) [ 19 ] …”

“…Guo and co‐workers demonstrated that the metal borates shells can protect the metal borides core structure in a stable state and hence extend the cycle life of supercapacitors. [ 19 ] MISR composes of two steel capillaries (the inner diameter = 0.6 mm) connected with a commercial T‐junction (its geometrical structure is shown in Figure S1, Supporting Information), but no capillary is connected to the T‐junction outlet, which provides a big‐sized outlet channel to achieve a normal pressure within the T‐junction chamber and also reduce the blockage problem significantly during the precipitation. Two reactant streams are ejected along the same axis in the opposite direction and collide halfway within the T‐junction chamber at rapid velocities, thus creating a high energy dissipation region for the intensified micromixing and uniform supersaturation level.…”