Self-assembled synthesis of waxberry-like open hollow NiCo2S4 with enhanced capacitance for high-performance hybrid asymmetric supercapacitors

Optimizing electrode materials performance and improving the energy density of supercapacitors is a hot research topic. The complex hollow sphere structure material, as a supercapacitor electrode material, provides more redox active sites and volume expansion space during the electrochemical energy storage process, which has the potential to assemble high performance supercapacitors. Herein, a novel nickel cobalt sulfide and carbon nanotube composite are successfully prepared by the Kirkendall effect. The yolk−shell-structured nickel cobalt sulfide and carbon nanotube composite exhibits superior electrochemical performance as the positive electrode of the hybrid supercapacitor. The hybrid supercapacitor has a specific capacity of 603 C g −1 at 1 A g −1 , and the capacity retention rate is as high as 67.4% from 1 to 15 A g −1 . Moreover, the assembled hybrid supercapacitor has an energy density of 45.35 Wh kg −1 . After 8000 cycles, the capacitance retention rate is 91.33%, and the columbic efficiency is 96.15%. Its excellent electrochemical performance is mainly attributed to the excellent conductivity of carbon nanotubes as the supporting skeleton and conducting network, which effectively inhibits the aggregation of nanospheres, exposes more active sites, and facilitates the rapid transmission of ions/electrons, thereby obtaining high specific capacity and rate performance.

Section: Resultsmentioning

confidence: 77%

Yolk–Shell Structured Nickel Cobalt Sulfide and Carbon Nanotube Composite for High-Performance Hybrid Supercapacitors

Deng

Wang

et al. 2021

“…The capacitive contributions of the Co(OH) 2 /CNT-WCS electrodes were estimated to be 40.5, 47.3, 52.4, 56.0, and 58.9% at 0.2, 0.4, 0.6, 0.8, and 1.0 mV s –1 , respectively (Figure e). The response time of ion diffusion decreases at higher scan rates, so as the scan rate increases, the percentage of capacitance contribution increases . The shaded portion of Figure f shows the approximately 58.9% contribution of capacitance at 1.0 mV s –1 .…”

Section: Resultsmentioning

confidence: 98%

Cobalt Hydroxide Nanosheets Grown on Carbon Nanotubes Anchored in Wood Carbon Scaffolding for High-Performance Hybrid Supercapacitors

Wang

et al. 2021

A novel green and sustainable self-supporting electrode for an excellent performance hybrid supercapacitor (HSC) based on hybridizing Co(OH)2 nanosheets with carbon nanotube (CNT) arrays in wood carbon scaffolding made of Chinese fir waste is designed. The composite electrode has an area specific capacity as high as 4.17 mA h cm–2 due to the synergy of the wood carbon scaffolds, CNTs, and Co(OH)2 nanosheets. The HSC constructed with the composite electrode and the CNT/carbonized wood electrode obtains a specific capacitance of 2.88 F cm–2, and after 11,000 cycles, the capacity retention rate of the HSC is still 97.8%, and its maximum energy and power density are 0.78 mW h cm–2 and 34.40 mW cm–2, respectively. The in situ growth of CNTs in carbonized wood can avoid aggregation and provide fast electron-transfer paths, and CNTs are wrapped by Co(OH)2 nanosheets by electrochemical deposition to obtain excellent electrochemical energy storage performance. This novel family of wood-derived materials represents a general and abundant candidate toward real-world energy storage applications.

“…Nevertheless, the electrical conductivity of binary transition-metal compounds is poor, which prevents further application. To improve the performance of electrode materials, a great effort has been made to design ternary transition metal compounds, such as NiCo 2 O 4 , NiMoO 4 , NiCo 2 S 4 , CuCo 2 S 4 , and NiMoP . These mixed metal centers with different valence states can provide considerable electronic conductivity and feasible electrochemical performance, but ternary metal compounds decrease the charging–discharging speed and the stability of the device .…”

Section: Introductionmentioning

confidence: 99%

Multidimensional Carbon-Modified NiCo₂O₄/Ni–Co–S Nanocomposite Electrode Material for High-Energy Asymmetric Supercapacitors

Sun

et al. 2021

The synergistic effect of the electrochemical double-layer and pseudocapacitance electrode materials has been extensively used to improve the performance of composite electrodes for supercapacitors (SCs). However, the energy density of SCs is still unsatisfactory for practical utilization. Herein, a C-NiCo 2 O 4 /C@Ni−Co−S electrode is ingeniously devised through coupling the interior of 0D/2D carbon-modified NiCo 2 O 4 and the external sheath of Ni−Co−S nanosheets. The 0D carbon quantum dot doping can effectively avoid the agglomeration of NiCo 2 O 4 nanoparticles and improve the electronic conductivity. 2D carbon as the intermediate layer can ameliorate the physical/chemical stability of the electrode. Ni−Co−S nanosheets can improve the areaspecific capacitance of the electrode and thus enhance the energy density of the device. As expected, the C-NiCo 2 O 4 /C@Ni−Co−Selectrode delivers an outstanding specific capacitance of 2396 F g −1 (7.9 F cm −2 ) at 3 A g −1 and excellent cycling stability (92% after 10 000 cycles). Furthermore, a quasi-solid-state asymmetric supercapacitor (ASC) using C-NiCo 2 O 4 /C@Ni−Co−S as positive electrode and active carbon (AC) as negative electrode exhibits a high energy density of 95 Wh kg −1 at 0.9 kW kg −1 and an excellent cycle performance. Our work reveals that this reasonable structure design is very effective for achieving a high-performance positive electrode for practical SC applications.