Enhanced rate and specific capacity in nanorod-like core-shell crystalline NiMoO_(4)@amorphous cobalt boride materials enabled by Mott-Schottky heterostructure as positive electrode for hybrid supercapacitors

The supercapacitor electrode materials suffer from structure pulverization and sluggish electrode kinetics under high current rates.Herein,a unique NiMoO_(4)@Co-B heterostructure composed of highly conductive Co-B nanoflakes and a semiconductive NiMoO_(4) nanorod is designed as an electrode material to exert the energy storage effect on supercapacitors.The formed Mott-Schottky heterostructure is helpful to overcome the ion diffusion barrier and charge transfer resistance during charging and discharging.Moreover,this crystalline-amorphous heterogeneous phase could provide additional ion storage sites and better strain adaptability.Remarkably,the optimized NiMoO_(4)@Co-B hierarchical nanorods(the mass ratio of NiMoO_(4)/Co-B is 3:1)present greatly enhanced electrochemical characteristics compared with other components,and show superior specific capacity of 236.2 mA h g^(-1)at the current density of 0.5 A g^(-1),as well as remarked rate capability.The present work broadens the horizons of advanced electrode design with distinct heterogeneous interface in other energy storage and conversion field.

Hollow Carbon Microspheres/MnO_2 Nanosheets Composites:Hydrothermal Synthesis and Electrochemical Behaviors

This article reported the electrochemical behaviors of a novel hollow carbon microspheres/manganese dioxide nanosheets(micro-HC/nano-MnO2) composite prepared by an in situ self-limiting deposition method under hydrothermal condition. The results of scanning electron microscopy reveal that MnO2 nanosheets homogeneously grow onto the surface of micro-HC to form a loose-packed microstructure. The quantity of MnO2 required in the electrode layer has thereby been reduced significantly, and higher specific capacitances have been achieved. The micro-HC/nano-MnO2 electrode presents a high capacitance of 239.0 F g-1 at a current density of 5 m A cm-2, which is a strong promise for high-rate electrochemical capacitive energy storage applications.

Liquid phase synthesis of dendritic nickel carbide alloy with high conductivity for advanced energy storage

Alloy materials have attracted increasing attentions because they possess superior electrical conductivity which can contribute to excellent electrochemical performance. Herein a dendritic Ni;C alloy material has been prepared by the pyrolysis of nickel acetylacetonate employing oleylamine as a reductant and 1-octadecene or octadecane as the solvent. The current–voltage curves indicating that the electrical conductivity of Ni;C is higher than that of nickel oxide. Electrochemical testing indicates that a high specific capacity of 390 C/g is found in alkaline electrolyte at 0.5 A/g, and deliver excellent rate characteristic as well as cycle life. The excellent electrochemical performance may be attributed to its high electrical conductivity and dendritic nanostructure that can promote diffusion of electrolyte ions. In addition, the AC//Ni;C asymmetric supercapacitor has been assembled at a cell voltages between 0 and 1.6 V, achieving a maximum energy density of 37 Wh/kg（at a power density of 0.3995 k W/kg）, and this manifests that the Ni;C alloy is a promising electrode material for electrochemical energy storage.

Electrolyte effect on electrochemical behaviors of manganese fluoride material for aqueous asymmetric and symmetric supercapacitors

Exploring wide voltage window materials is not only an available measure to enhance the energy density of hybrid supercapacitor(HSCs),but also avoids the dynamic mismatch caused by different energy storage mechanisms of two electrodes in assembled symmetrical HSC.However,there are few reports about the wide potential window materials except Bi_(2)O_(3)and VO_(2).Therefore,the MnF_(2)synthesized by solvothermal reaction was served as the electrode for HSC.The MnF_(2)exhibited electrochemical activity in alkaline solution in three-electrode system,especially with a wide potential window from-0.8 to+0.5 V in 2 mol·L^(-1)NaOH.Furthermore,the assembled MnF_(2)//MnF_(2)symmetrical HSC had a potential window of 1.5 V,and it exhibited outstanding long-cycle capability.Meanwhile,when MnF_(2)was taken as the negative and positive respectively,the potential windows of asymmetric devices CoMoO_(4)//MnF_(2)and MnF_(2)//Activated Carbon(AC)could reach 1.3 and 1.45 V,respectively,showing excellent cycle stability.This work shows that MnF_(2)material has great research value in HSC,and provides a new research direction for developing high-performance devices.

Investigating metal-organic framework as a new pseudo-capacitive material for supercapacitors

A new application of metal organic framework （MOF） as a pseudo-capacitive material for supercapacitors is investigated. To this end, a simple nickel-based MOF, formulated Ni3（btc）2.12H2O, is synthesized via a hydrothermal reaction. As an electro-active material, such nickel-based MOF exhibits superior pseudo- capacitive behavior in KOH aqueous electrolyte with a high specific capacitance of 726 F g-1. Also, it displays good electrochemical stability with 94.6% of the initial capacitance over consecutive 1000 cycles. In addition, a simple asymmetric supercapacitor with a high energy density of 16.5 Wh kg-1 is successfully built using the nickel-based MOF as positive electrode and commercial activated carbon as negative electrode in KOH electrolyte.

Synthesis of Co-Ni oxide microflowers as a superior anode for hybrid supercapacitors with ultralong cycle life

Li-ion hybrid capacitors（LIHCs）,composing of a lithium-ion battery（LIB） type anode and a supercapacitor（SC） type cathode,gained worldwide popularity due to harmonious integrating the virtues of high energy density of LIBs with high power density of SCs.Herein,nanoflakes composed microflower-like Co-Ni oxide（CoNiO） was successfully synthesized by a simple co-precipitation method.The atomic ratio of as-synthesized CoNiO is determined to be 1：3 through XRD and XPS analytical method.As a typical battery-type material,CoNiO and capacitor-type activated polyanilinederived carbon（APDC） were used to assemble LIHCs as the anode and cathode materials,respectively.As a result,when an optimized mass ratio of CoNiO and APDC was 1：2,CoNiO//APDC LIHC could deliver a maximum energy density of 143 Wh kg^-1 at a working voltage of 1-4 V.It is worth mentioning that the LIHC also exhibits excellent cycle stability with the capacitance retention of -78.2%after 15,000 cycles at a current density of 0.5 A g^-1.

Perovskite fluoride NaNiF_(3) with hollow micron sphere structure as anode for Li-ion hybrid capacitors

Lithium-ion hybrid capacitors(LIHCs) are gaining more attention and applications because they break the performance limitations of supercapacitors(SCs) and lithium-ion batteries(LIBs).However,the difference of energy storage mechanism between anode and cathode is a problem that must be faced by Li-ion hybrid capacitors.The selection of suitable anode and cathode materials is one of the effective ways to solve this problem.Here,we synthesized hollow spherical perovskite fluoride NaNiF3 by a simple and safe method.The specific capacity of NaNiF3 is 142 mAh·g^(-1) at 0.1 A·g^(-1) for 1000 cycles.The mechanism in the cycling of NaNiF3 electrodes was investigated using ex situ X-ray photoelectron spectroscopy(XPS),which is typical of the conversion reaction.Meanwhile,the NaNiF_(3)//activated carbon(AC) Li-ion hybrid capacitor assembled and showed better energy density(69 Wh·kg^(-1)) and power density(5699 W·kg^(-1)).Its capacity retention after long cycling was 79%.The use of NaNiF3 expands the choice of electrode materials for LIHCs and extends their practical applications.