A Tubular Sandwich-Structured CNT@Ni@Ni₂(CO₃)(OH)₂ with High Stability and Superior Capacity as Hybrid Supercapacitor

Abstract

Development of highly stabile battery-type electrode materials with superior capacity has been a critical challenge for hybrid supercapacitors. We report a high-performance electrode material, tubular sandwich-structured CNT@Ni@Ni 2 (CO 3 )(OH) 2 , synthesized via a scalable, dynamic, controlled in situ reduction− chemical deposition process. Applied as a battery-type electrode material, this novel nanostructure exhibits excellent electrochemical stability, majorly attributed to the Ni midshell serving a dual role as "capacity supplement" and "electron highway", which, to our knowledge, was incorporated into the nanocomposite electrodes for the first time. Also benefiting from the high conductivity of carbon nanotubes (CNTs) and the high capacity of the amorphous NiOOH ultrathin film [converted from the Ni 2 (CO 3 )(OH) 2 outer shell], the resulting CNT@Ni@Ni 2 (CO 3 )(OH) 2 material as a battery-type electrode achieves a superior capacity of 221 mAh•g −1 at 5 A•g −1 with 76% capacity retention at 50 A•g −1 and maintains 81% capacity after 9000 cycles at 5 A•g −1 . An advanced aqueous hybrid supercapacitor using activated carbon and CNT@Ni@Ni 2 (CO 3 )(OH) 2 nanocomposite as the negative and positive electrodes, respectively, delivers a high energy density of 179 Wh•kg −1 at a power density of 2880 W•kg −1 with capacitance retention in excess of 85% over 5500 cycles. The outstanding performance demonstrates its practical potential in advanced hybrid supercapacitors.

Bioinspired sea-sponge nanostructure design of Ni/Ni(HCO3)2-on-C for a supercapacitor with a superior anti-fading capacity

“…As shown in Fig. 4A 3 , the O 1s peak can be deconvoluted into two peaks at 531.7 eV and 532.5 eV, which are assigned to the bonds of HCO 3and C-OH, proving that the Ni( 11 which can well-explain the results from the TG measurement. These new bonds play important roles in the electrochemical processes.…”

“…[6][7][8][9] However, it often shows a poor cycling life, due to its sluggish reaction kinetics and structural degradations of electrode nanomaterials in the charge-discharge processes. [10][11] Therefore, the power density and cyclability of the pseudocapacitors were often sacrificed in order to increase their energy densities.…”

Carbon Transition‐metal Oxide Electrodes: Understanding the Role of Surface Engineering for High Energy Density Supercapacitors

“…Among the various hybrid electrode materials, C-TMO composite has gained particular interest since it combines the advantages of both components while reducing their shortcomings. [36,60,[72][73][74][75] Here, we present recent development on the preparation of C-TMO composite material as an active electrode towards SCs. This section will give insight on the specific role of carbon as well as TMOs, with particular emphasis on the carbon as active support, core element, and conductive substrate.…”

“…Chen et al fabricated tubular sandwich-structured CNT@Ni@Ni 2 (CO 3 )(OH) 2 with the assistance of carboxyl and hydroxyl groups available on the surface of pre-treated CNT. [73] These functional groups immobilized the Ni 2 + ions to induce the formation of robust CNT@Ni core-shell nanotubes backbone, before utilizing it as a support for succeeding chemical deposition as shown in Figure 4(b). Aside from typical strong acids used for treating CNT, deoxy-ribonucleic acid (DNA) has also been utilized to assist the dispersion of CNTs in aqueous solutions and to ensure high mass loading of metal oxides.…”

“…(b) Schematic illustration of the synthesis of CNT@Ni@Ni 2 (CO 3 )(OH) 2 nanocomposites. Reproduced with permission from ref., [73] Copyright 2017, American Chemical Society. (c) Synthesis process of the CMK-3-P-Fe 2 O 3 and CMK-3-Fe 2 O 3 hybrids.…”