Cobalt Doping To Boost the Electrochemical Properties of Ni@Ni₃S₂ Nanowire Films for High‐Performance Supercapacitors

Abstract

Metal sulfides have aroused great interest for energy storage. However, their low specific capacities and inferior rate capabilities hinder their practical applications. In this work, a facile cobalt-doping process is used to boost the electrochemical performance of Ni@Ni S core-sheath nanowire film electrodes for high-performance electrochemical energy storage. Co ions are doped successfully and uniformly into Ni S nanosheets through a facile ion-exchange process. The electrochemical properties of film electrodes are improved greatly, and an ultrahigh volumetric capacity (increased from 105 to 730 C cm at 0.25 A cm ) and excellent rate capability are obtained after Co is doped into Ni@Ni S core-sheath nanowires. A hybrid asymmetric supercapacitor with Co-doped Ni@Ni S as the positive electrode and graphene-carbon nanotubes as the negative electrode is assembled and exhibits an ultrahigh volumetric capacitance of 142 F cm (based on the total volume of both electrodes) at 0.5 A cm and excellent cycling stability (only 3 % capacitance decrease after 5000 cycles). Moreover, the volumetric energy density can reach 44.5 mWh cm , which is much larger than those of thin-film lithium batteries (1-10 mWh cm ). These results may provide useful insights for the fabrication of high-performance film electrodes for energy-storage applications.

Porous Ultrathin NiSe Nanosheet Networks on Nickel Foam for High‐Performance Hybrid Supercapacitors

“…To evaluate the practical application potential of the put-NiSe NNs electrode, an HSC device was fabricated using the put-NiSeN Ns and porous carbon (PC, the capacitive performance of the anode PC electrode is shown in Figure S8) electrode as the cathode and anode,r espectively.T he CV curvesa t5 0mVs À1 within different voltage window are shown in Figure 6a.C hoosing0 -1.7 Vast he most appropriate voltage window, typical CV curves of the put-NiSe NNs//PC HSC device at various scan rates are shown in Figure 6b,i ndicating the synergistic effect of the combined battery and EDLC performance. [27] As anticipated, nearly symmetricald ischargechargec urves were observed in the GCD curves at all given currentd ensities (Figure 6c), showinge xcellent electrochemical reversibility.T he calculated specific capacitances from the GCD curvesare illustrated in Figure 6d.Ahigh specific capacity of 78.4 mAh g À1 was obtained at ac urrento f0.5 Ag À1 .T he corresponding Ragone plots of the put-NiSe NNs//PC HSC device derived from the discharge curves are presented in Figure 6e, showingh igh energy densities of 66.6 Wh kg À1 at 425 Wkg À1 , ChemSusChem 2020, 13,260 -266 www.chemsuschem.org 46.5 Wh kg À1 at 1700 Wkg À1 ,a nd 25.7 Wh kg À1 even at ah igh power density of 8500 Wkg À1 .T hese values were significantly higher than the best energy density of most hybrid systems reported previously,f or example, 40 Wh kg À1 for ultrathin and porousN i 3 S 2 /CoNi 2 S 4 3D network, [29] 52.6 Wh kg À1 for Ni-Co oxide onions, [40] 28.5 Wh kg À1 for CoNi-MOF [28] (Figure 6e and Ta ble S1) [14,29,[41][42][43][44][45] In addition to high capacitance and energy density,l ong cycle life and reliable cycling stability are also crucial factorsfor evaluating the performance of supercapacitors. We evaluated the cycling stability of the put-NiSe NNs//PC HSC deviceb ya n uninterrupted GCD test at ah igh current density of 5.0 Ag À1 .…”

“…Fabrication of TM-compound-based nanomaterials (e.g., MoN nanoparticles, [25] self-supportedZ nNiCo-Pn anosheets, [26] Ni@Ni 3 S 2 Nanowire Films, [27] CoNi-MOF [28] )o nc onductive substrates (e.g.,n ickel foam,c arbon fibers paper,o rc arbon cloth) has been regardeda sa ne ffective meanst oe nhancec apacitive performance, mainly attributed to the following merits: (1) Electrode materials directly grown on conductive substrates can be already used as the electrodes in capacitors without the addition of any nonconductive binder,w hichi sp referred for their electrochemical performance because the presenceo f binder particlesc an reduce the ion diffusion and charget ransfer between electrode materials and substrates. [29] (2) In this way,the electrode materials are much more robust on the substrates, benefiting from al ong cyclel ife during the electrochemicalp rocess.…”

One‐step Synthesis of Self‐standing Ni3S2/Ni2P Heteronanorods on Nickel Foam for Efficient Electrocatalytic Hydrogen Evolution over a Wide pH Range

“…The survey spectrum (Figure a) of Ni‐S−P NRs/NF confirms the presence of Ni, S and P in the sample. The C and O may come from the reference and the exposure of the sample to the atmosphere ,. No other impurities were observed.…”

Fabrication of a Mo‐Doped Strontium Cobaltite Perovskite Hybrid Supercapacitor Cell with High Energy Density and Excellent Cycling Life

“…Broadly, SCs store charge through two mechanisms, that is, either electrochemical double layer capacitance (EDLC)o rp seudocapacitance (PC). [17] As the electrode materialp lays a decisive role in shaping the ultimate performance of asupercapacitor( or the energy storaged evice), al ot of research is carried out in this area of science, highlighting the use of novel materials with the aim of developing efficient energy storage systems. [6][7][8][9][10][11] Unlike carbon materials,t he transition metal oxides/hydroxides possess high specific capacitance as ar esult of faradaicr eactions occurring on the surface/subsurfacer egions.N evertheless, these are unable to meet the performance of asupercapacitor owing to low electrical conductivity and poor cycling stability.…”