Boosting Pseudocapacitive Behavior of Supercapattery Electrodes by Incorporating a Schottky Junction for Ultrahigh Energy Density

Pseudo-capacitive negative electrodes remain a major bottleneck in the development of supercapacitor devices with high energy density because the electric double-layer capacitance of the negative electrodes does not match the pseudocapacitance of the corresponding positive electrodes.In the present study,a strategically improved Ni-Co-Mo sulfide is demonstrated to be a promising candidate for high energy density supercapattery devices due to its sustained pseudocapacitive charge storage mechanism.The pseudocapacitive behavior is enhanced when operating under a high current through the addition of a classical Schottky junction next to the electrode-electrolyte interface using atomic layer deposition.The Schottky junction accelerates and decelerates the diffusion of OH-/K+ions during the charging and discharging processes,respectively,to improve the pseudocapacitive behavior.The resulting pseudocapacitive negative electrodes exhibits a specific capacity of 2,114 C g^(-1)at 2 A g^(-1)matches almost that of the positive electrode’s 2,795 C g^(-1)at 3 A g^(-1).As a result,with the equivalent contribution from the positive and negative electrodes,an energy density of 236.1 Wh kg^(-1)is achieved at a power density of 921.9 W kg^(-1)with a total active mass of 15 mg cm-2.This strategy demonstrates the possibility of producing supercapacitors that adapt well to the supercapattery zone of a Ragone plot and that are equal to batteries in terms of energy density,thus,offering a route for further advances in electrochemical energy storage and conversion processes.

Mixed-phase composites derived from cobalt terephthalate as efficient battery-type electrodes for high-performance supercapattery

Interfacial engineering of two-dimensional(2D)monometallic phosphides enables remarkable structural and electrochemical properties in energy storage devices.Herein,2D nanosheets(NSs)of FeP_(2)/Co_(2) P were grown on Ni-foam(FCP)using a solution-based and phosphorization approach to be used as freestanding for high-performance energy storage devices.An effective phosphorization strategy is successfully de-veloped to improve the overall crystalline phase,tailor the morphology,and boost the electrochemical performances of electrodes.The FCP NSs electrode exhibits a battery-type redox behavior with a maxi-mum high areal capacity of 1.96 C cm^(-2) at 4 mA cm^(-2) in 6 M KOH aqueous electrolyte compared to the other counterparts.The superior electrochemical performance was achieved by increasing the electroac-tive sites and high conductivity via surface tailoring and fast redox reactions.Moreover,a supercapattery was assembled utilizing FCP and activated carbon(AC)electrodes and it revealed maximum specific en-ergy(E_(s))and specific power(P_(s))of 41.2 Wh kg^(-1) and 7578 W kg^(-1) with good cycling stability of 91%after 10,000 cycles at 5 A g^(-1).Eventually,the supercapattery has been explored in practical applications by lighting up light-emitting diodes(LEDs),representing the real-time performance of superior energy storage devices.

A novel Li-ion supercapattery by K-ion vacant ternary perovskite fluoride anode with pseudocapacitive conversion/insertion dual mechanisms

An innovative K+vacant ternary perovskite fluoride(K_(0.89)Ni_(0.02)Co_(0.03)Mn_(0.95)F_(3.0),KNCMF-3#)anode was designed for advanced Li-ion supercapattery(i.e.,Li-ion capacitors/batteries,LIC/Bs).Owing to the conversion/insertion dual mechanisms and fast pseudocapacitive con-trol dynamics,the KNCMF-3#electrode exhibits superior electrochemical performance,especially the excellent cycle performance(467%(229 mAh·g^(-1))/1000 cycles/2 A·g^(-1)).Moreover,the hybrid KNCMF-3#/reduced gra-phene oxide(rGO)electrode can further increase the electrochemical performance(217-97 mAh·g^(-1)/0.1-3.2 A·g^(-1),150%(197 mAh·g^(-1))/1000 cycles/2 A·g^(-1)).Also,a novel capacitor/battery cathode,activated carbon(AC)+LiFePO_(4)+graphene(AC+LFP+G),exhibits impres-sive performance(128-82 mAh·g^(-1)/0.1-3.2 A·g^(-1),84%/1000 cycles/2 A·g^(-1)).By the synergistic optimization of anode and cathode,the Li-ion supercapattery KNCMF-3#@rGO//AC+LFP+G demonstrates remarkable per-formance,for example,111.9-23.8 Wh·kg^(-1)/0.4-8.0 kW·kg^(-1)/82%/2000 cycles/5 A·g^(-1)/0-4 V,which is superior to KNCMF-3#//AC LICs,KNCMF-3#@rGO//AC LICs,KNCMF-3#//AC+LFP+G LIC/Bs.In all,the novel Li-ion supercapattery idea adds a promising per-spective to develop advanced energy storage devices.

Ternary MOF‑Based Redox Active Sites Enabled 3D‑on‑2D Nanoarchitectured Battery‑Type Electrodes for High‑Energy‑Density Supercapatteries

Designing rationally combined metal-organic frameworks(MOFs)with multifunctional nanogeometries is of significant research interest to enable the electrochemical properties in advanced energy storage devices.Herein,we explored a new class of binderfree dual-layered Ni-Co-Mn-based MOFs(NCM-based MOFs)with three-dimensional(3D)-on-2D nanoarchitectures through a polarityinduced solution-phase method for high-performance supercapatteries.The hierarchical NCM-based MOFs having grown on nickel foam exhibit a battery-type charge storage mechanism with superior areal capacity(1311.4μAh cm^−2 at 5 mA cm^−2),good rate capability(61.8%;811.67μAh cm^−2 at 50 mA cm^−2),and an excellent cycling durability.The superior charge storage properties are ascribed to the synergistic features,higher accessible active sites of dual-layered nanogeometries,and exalted redox chemistry of multi metallic guest species,respectively.The bilayered NCM-based MOFs are further employed as a battery-type electrode for the fabrication of supercapattery paradigm with biomass-derived nitrogen/oxygen doped porous carbon as a negative electrode,which demonstrates excellent capacity of 1.6 mAh cm^−2 along with high energy and power densities of 1.21 mWh cm^−2 and 32.49 mW cm^−2,respectively.Following,the MOF-based supercapattery was further assembled with a renewable solar power harvester to use as a self-charging station for various portable electronic applications.

Comprehensive Insight into the Mechanism, Material Selection and Performance Evaluation of Supercapatteries

Electrochemical energy storage devices(EESs)play a crucial role for the construction of sustainable energy storage system from the point of generation to the end user due to the intermittent nature of renewable sources.Additionally,to meet the demand for next-generation electronic applications,optimizing the energy and power densities of EESs with long cycle life is the crucial factor.Great e orts have been devoted towards the search for new materials,to augment the overall performance of the EESs.Although there are a lot of ongoing researches in this field,the performance does not meet up to the level of commercialization.A further understanding of the charge storage mechanism and development of new electrode materials are highly required.The present review explains the overview of recent progress in supercapattery devices with reference to their various aspects.The di erent charge storage mechanisms and the multiple factors involved in the performance of the supercapattery are described in detail.Moreover,recent advancements in this supercapattery research and its electrochemical performances are reviewed.Finally,the challenges and possible future developments in this field are summarized.

Charge Storage Properties of Aqueous Halide Supercapatteries with Activated Carbon and Graphene Nanoplatelets as Active Electrode Materials

Device level performance of aqueous halide supercapatteries fabricated with equal electrode mass of activated carbon or graphene nanoplatelets has been characterized.It was revealed that the surface oxygen groups in the graphitic structures of the nanoplatelets contributed toward a more enhanced charge storage capacity in bromide containing redox electrolytes.Moreover,the rate performance of the devices could be linked to the effect of the pore size of the carbons on the dynamics of the inactive alkali metal counterion of the redox halide salt.Additionally,the charge storage performance of aqueous halide supercapatteries with graphene nanoplatelets as the electrode material may be attributed to the combined effect of the porous structure on the dynamics of the non-active cations and a possible interaction of the Br^(-)/(Br_(2)+Br^(-)_(3))redox triple with the surface oxygen groups within the graphitic layer of the nanoplatelets.Generally,it has been shown that the surface groups and microstructure of electrode materials must be critically correlated with the redox electrolytes in the ongoing efforts to commercialize these devices.

Two-dimensional porous zinc cobalt sulfide nanosheet arrays with superior electrochemical performance for supercapatteries

Unique two-dimensional(2D)porous nanosheets with overwhelmingly rich channels and large specific surface area exhibit superior electrochemical capacitance performance,as compared to the conventional zero-and one-dimensional counterparts.As ternary transition metal sulfides(TMSs)are well recognized for their high electrochemical activity and capacity,and the replacement of oxygen with sulfur may result in high stability and flexible properties of the nanomaterials,as compared to transition metal oxides,herein we report the synthesis of 2D porous nanosheet arrays of Zn_(x)Co_(1-x)S(x=0,0.25,0.5,0.75,and 1)via a facile hydrothermal process.Due to the synergistic effect of the metal components and a unique 2D porous structure,the Zn_(0.5)Co_(0.5)S electrode was found to stand out as the best among the series,with a high specific capacity of 614 C g^(-1)at 1 A g^(-1)and excellent cycle retention rate of 90%over 10,000 cycles at 10 A g^(-1).Notably,a supercapattery based on a Zn_(0.5)Co_(0.5)S positive electrode and an activated carbon(AC)negative electrode(Zn_(0.5)Co_(0.5)S//AC)was found to display a 1.6 V voltage window,a 61 mA h g^(-1)specific capacity at 1 A g^(-1),a 49 Wh kg^(-1)energy density at 957 W kg^(-1)power density,and excellent cycling performance(88%over 10,000 cycles),suggesting tremendous potential of Zn_(0.5)Co_(0.5)S in the development of high-performance supercapattery devices.