Pseudocapacitive materials generally offer both high capacitance and high rate capability, which has stimulated great efforts in developing the materials system and related energy storage devices. In recent years, how...Pseudocapacitive materials generally offer both high capacitance and high rate capability, which has stimulated great efforts in developing the materials system and related energy storage devices. In recent years, however, with the extensive use of nanomaterials in batteries, fast redox kinetics comparable to pseudocapacitive have been achieved in many kinds of battery materials due to the much shortened ion diffusion lengths and highly exposed surface/interface as a result of nanosize effect. Consequently, the terms"pseudocapacitive materials" and "battery materials" are becoming more and more confusing. In this review, different opinions on the definition of pseudocapacitive materials and the evolution of the definitions as well as the resulting confusion will be firstly reviewed. Then, to accurately distinguish pseudocapacitive and battery materials, method with the consideration of both the electrochemical signatures(CVs and GCD) and quantitative kinetics analysis as a supplement is proposed. Finally, we end this review by discussing the possible device configurations of asymmetric supercapacitors and hybrid supercapacitors. The present review will help understanding the differences between pseudocapacitive materials and battery materials, and thus avoiding the definition confusion.展开更多
Pseudocapacitive materials that store charges via reversible surface or near-surface faradaic reactions are capable of overcoming the capacity limitations of electrical double-layer capacitors.Revealing the structure...Pseudocapacitive materials that store charges via reversible surface or near-surface faradaic reactions are capable of overcoming the capacity limitations of electrical double-layer capacitors.Revealing the structure–activity relationship between the microstructural features of pseudocapacitive materials and their electrochemical performance on the atomic scale is the key to build high-performance capacitor-type devices containing ideal pseudocapacitance effect.Currently,the high brightness(flux),and spectral and coherent nature of synchrotron X-ray analytical techniques make it a powerful tool for probing the structure–property relationship of pseudocapacitive materials.Herein,we report a comprehensive and systematic review of four typical characterization techniques(synchrotron X-ray diffraction,pair distribution function[PDF]analysis,soft X-ray absorption spectroscopy,and hard X-ray absorption spectroscopy)for the study of pseudocapacitance mechanisms.In addition,we offered significant insights for understanding and identifying pseudocapacitance mechanisms(surface redox pseudocapacitance,intercalation pseudocapacitance,and the extrinsic pseudocapacitance phenomenon in battery materials)by combining in situ hard XAS and electrochemical analyses.Finally,a perspective for further depth of understanding into the pseudocapacitance mechanism using synchrotron X-ray analytical techniques is proposed.展开更多
Nano Research volume 13,pages1686–1692(2020)Cite this article 210 Accesses 1 Citations Metrics details Abstract Fiber-shaped supercapacitors(FSCs),owing to their high-power density and feasibility to be integrated in...Nano Research volume 13,pages1686–1692(2020)Cite this article 210 Accesses 1 Citations Metrics details Abstract Fiber-shaped supercapacitors(FSCs),owing to their high-power density and feasibility to be integrated into woven clothes,have drawn tremendous attentions as a key device for flexible energy storage.However,how to store more energy while withstanding various types of mechanical deformation is still a challenge for FSCs.Here,based on a magnetron sputtering method,different pseudocapacitive materials are conformally coated on self-supported carbon nanotube aligned films.This fabrication approach enables a stretchable,asymmetric,coaxial fiber-shaped supercapacitors with high performance.The asymmetric electrode configuration that consists of CNT@NiO@MnOx cathode and CNT@Fe2O3 anode successfully extends the FSC’s electrochemical window to 1.8 V in an aqueous electrolyte.As a result,a high specific capacitance of 10.4 F·cm^−3 is achieved at a current density of 30 mA·cm^−3 corresponding to a high energy density of 4.7 mWh·cm^−3.The mechanical stability of the stretchable FSC is demonstrated with a sustainable performance under strains up to 75%and a capacitance retention of 95%after 2,000 cycles under 75%strain.展开更多
Because of the intensified electrochemical activities,mixed metal oxides as a representative for pseudocapacitive materials play a key role for high performance supercapacitor electrodes.Nevertheless,low ion and elect...Because of the intensified electrochemical activities,mixed metal oxides as a representative for pseudocapacitive materials play a key role for high performance supercapacitor electrodes.Nevertheless,low ion and electron transfer rate and poor cycling performance in the electrode practically restrict further promotion of their electrochemical performance.In order to offset the defect,a novel copper(Cu)foamsupported nickel molybdate nanosheet decorated carbon nanotube wrapped copper oxide nanowire array(NiMoO4 NSs-CNTs-CuO NWAs/Cu foam)flexible electrode is constructed.The as-prepared electrode demonstrates a unique core-shell holey nanostructure with a large active surface area,which can provide a large number of active sites for redox reactions.Besides,the CNTs networks supply improved conductivity,which can hasten electron transport.Through this simple and efficient design method,the spatial distribution of each component in the flexible electrode is more orderly,short and fast electron transport path with low intrinsic resistance.As a result,the NiMoO4 NSs-CNTs-CuO NWAs/Cu foam as an adhesiveless supercapacitor electrode material exhibits excellent ene rgy storage perfo rmance with high specific areal capacitance of 23.40 F cm^(-2)at a current density of 2 mA cm^(-2),which outperforms most of the flexible electrodes re ported recently.The assembled asymmetric supercapacitor demonstrates an energy density up to 96.40 mW h cm^(-3)and a power density up to 0.4 W cm^(-3)under a working voltage window of 1.7 V.In addition,outstanding flexibility of up to 100°bend and good cycling stability with the capacitance retention of 82.53%after 10,000 cycles can be obtained.展开更多
Although pseudocapacitive manganese dioxide(MnO_(2))integrates the high-power merit of carbonaceous materials with the high-energy merit of battery-type materials,it still has a long way to go in achieving a more sati...Although pseudocapacitive manganese dioxide(MnO_(2))integrates the high-power merit of carbonaceous materials with the high-energy merit of battery-type materials,it still has a long way to go in achieving a more satisfactory balance of higher energy and power density,and in decoupling the relationship of structural characteristics with energy storage performance.To realize such goals,a bottom-up[WO_(6)]-perturbed[MnO_(6)]assembly strategy has been developed here due to their similar structure,yet mismatched lattice parameters.This facile protocol is capable of finely controlling the morphology and crystal structure of MnO_(2)by adjusting its internal[WO_(6)]concentration.Therefore,the as-prepared W_xMnO_(2)is treated as an ideal platform to scrutinize the correlations of the structure with the energy storage performance.The operando Raman spectra and finite element analysis have fully demonstrated the superiority of the locally ordered defects-enriched structure of W_(0.02)-MnO_(2),which could reach a favorable balance between the ion diffusion equilibrium time and the number of active sites.As a result,the W_(0.02)-MnO_(2)is able to deliver a high capacitance of 292 F·g^(-1)at a current density of 1 A·g^(-1)and a remarkable rate performance with a 60%capacity retention at a current density of 50 A·g^(-1).The further unveiled structure-performance relationship provides a guideline for the design of better pseudocapacitive energy storage devices.展开更多
基金supported by grants from the National Natural Science Foundation of China(Grant Nos.51672205,51872104 and 21673169)the National Key R&D Program of China(Grant No.2016YFA0202602)+1 种基金the Research Start-Up Fund from Wuhan University of Technologythe Fundamental Research Funds for the Central Universities(WUT:2016IVA083,2017IB005,185220011)
文摘Pseudocapacitive materials generally offer both high capacitance and high rate capability, which has stimulated great efforts in developing the materials system and related energy storage devices. In recent years, however, with the extensive use of nanomaterials in batteries, fast redox kinetics comparable to pseudocapacitive have been achieved in many kinds of battery materials due to the much shortened ion diffusion lengths and highly exposed surface/interface as a result of nanosize effect. Consequently, the terms"pseudocapacitive materials" and "battery materials" are becoming more and more confusing. In this review, different opinions on the definition of pseudocapacitive materials and the evolution of the definitions as well as the resulting confusion will be firstly reviewed. Then, to accurately distinguish pseudocapacitive and battery materials, method with the consideration of both the electrochemical signatures(CVs and GCD) and quantitative kinetics analysis as a supplement is proposed. Finally, we end this review by discussing the possible device configurations of asymmetric supercapacitors and hybrid supercapacitors. The present review will help understanding the differences between pseudocapacitive materials and battery materials, and thus avoiding the definition confusion.
基金financialy supported by National Key R&D Program of China(2022YFB2402600)the National Natural Science Foundation of China(22279166)+1 种基金the Research Start-up Funds from Sun Yat-Sen University(200306)the Fundamental Research Funds for the Central Universities,Sun Yat-Sen University(22qntd0101 and 22dfx01)
文摘Pseudocapacitive materials that store charges via reversible surface or near-surface faradaic reactions are capable of overcoming the capacity limitations of electrical double-layer capacitors.Revealing the structure–activity relationship between the microstructural features of pseudocapacitive materials and their electrochemical performance on the atomic scale is the key to build high-performance capacitor-type devices containing ideal pseudocapacitance effect.Currently,the high brightness(flux),and spectral and coherent nature of synchrotron X-ray analytical techniques make it a powerful tool for probing the structure–property relationship of pseudocapacitive materials.Herein,we report a comprehensive and systematic review of four typical characterization techniques(synchrotron X-ray diffraction,pair distribution function[PDF]analysis,soft X-ray absorption spectroscopy,and hard X-ray absorption spectroscopy)for the study of pseudocapacitance mechanisms.In addition,we offered significant insights for understanding and identifying pseudocapacitance mechanisms(surface redox pseudocapacitance,intercalation pseudocapacitance,and the extrinsic pseudocapacitance phenomenon in battery materials)by combining in situ hard XAS and electrochemical analyses.Finally,a perspective for further depth of understanding into the pseudocapacitance mechanism using synchrotron X-ray analytical techniques is proposed.
基金supported by the National Natural Science Foundation of China(51673117 and 21805193)the Science and Technology Innovation Commission of Shenzhen(JSGG20160226201833790,JCYJ20170818093832350,JCYJ20170818112409808 and JSGG20170824112840518)China Postdoctoral Science Foundation(2017M622786,2017M622787 and 2019M653067)。
基金This work was financially supported by the National Key R&D Program of China(No.2016YFB0100100)the National Natural Science Foundation of China(Nos.21433013,U1832218,and 21975140).
文摘Nano Research volume 13,pages1686–1692(2020)Cite this article 210 Accesses 1 Citations Metrics details Abstract Fiber-shaped supercapacitors(FSCs),owing to their high-power density and feasibility to be integrated into woven clothes,have drawn tremendous attentions as a key device for flexible energy storage.However,how to store more energy while withstanding various types of mechanical deformation is still a challenge for FSCs.Here,based on a magnetron sputtering method,different pseudocapacitive materials are conformally coated on self-supported carbon nanotube aligned films.This fabrication approach enables a stretchable,asymmetric,coaxial fiber-shaped supercapacitors with high performance.The asymmetric electrode configuration that consists of CNT@NiO@MnOx cathode and CNT@Fe2O3 anode successfully extends the FSC’s electrochemical window to 1.8 V in an aqueous electrolyte.As a result,a high specific capacitance of 10.4 F·cm^−3 is achieved at a current density of 30 mA·cm^−3 corresponding to a high energy density of 4.7 mWh·cm^−3.The mechanical stability of the stretchable FSC is demonstrated with a sustainable performance under strains up to 75%and a capacitance retention of 95%after 2,000 cycles under 75%strain.
基金supported by the National Natural Science Foundation of China(Nos.51673117,51973118,and 21805193)the Science and Technology Innovation Commission of Shenzhen(Nos.JCYJ20170818093832350,JCYJ20170818112409808,JSGG20170824112840518,JCYJ20180507184711069,JCYJ20170818100112531,JCYJ20170817094628397,and JCYJ20180305125319991)+1 种基金the Key-Area Research and Development Program of Guangdong Province(Nos.2019B010929002 and 2019B010941001)the China Postdoctoral Science Foundation(No.2019M650212)。
文摘Because of the intensified electrochemical activities,mixed metal oxides as a representative for pseudocapacitive materials play a key role for high performance supercapacitor electrodes.Nevertheless,low ion and electron transfer rate and poor cycling performance in the electrode practically restrict further promotion of their electrochemical performance.In order to offset the defect,a novel copper(Cu)foamsupported nickel molybdate nanosheet decorated carbon nanotube wrapped copper oxide nanowire array(NiMoO4 NSs-CNTs-CuO NWAs/Cu foam)flexible electrode is constructed.The as-prepared electrode demonstrates a unique core-shell holey nanostructure with a large active surface area,which can provide a large number of active sites for redox reactions.Besides,the CNTs networks supply improved conductivity,which can hasten electron transport.Through this simple and efficient design method,the spatial distribution of each component in the flexible electrode is more orderly,short and fast electron transport path with low intrinsic resistance.As a result,the NiMoO4 NSs-CNTs-CuO NWAs/Cu foam as an adhesiveless supercapacitor electrode material exhibits excellent ene rgy storage perfo rmance with high specific areal capacitance of 23.40 F cm^(-2)at a current density of 2 mA cm^(-2),which outperforms most of the flexible electrodes re ported recently.The assembled asymmetric supercapacitor demonstrates an energy density up to 96.40 mW h cm^(-3)and a power density up to 0.4 W cm^(-3)under a working voltage window of 1.7 V.In addition,outstanding flexibility of up to 100°bend and good cycling stability with the capacitance retention of 82.53%after 10,000 cycles can be obtained.
基金financially supported by the National Natural Science Foundation of China(Nos.22105164 and 21875205)the National Natural Science Foundation of Hebei Province(No.B2022203009)+1 种基金Hebei Province Foundation for the National Natural Science Foundation(No.206Z4404G)the subsidy for Hebei Key Laboratory of Applied Chemistry after Operation Performance(No.22567616H)。
文摘Although pseudocapacitive manganese dioxide(MnO_(2))integrates the high-power merit of carbonaceous materials with the high-energy merit of battery-type materials,it still has a long way to go in achieving a more satisfactory balance of higher energy and power density,and in decoupling the relationship of structural characteristics with energy storage performance.To realize such goals,a bottom-up[WO_(6)]-perturbed[MnO_(6)]assembly strategy has been developed here due to their similar structure,yet mismatched lattice parameters.This facile protocol is capable of finely controlling the morphology and crystal structure of MnO_(2)by adjusting its internal[WO_(6)]concentration.Therefore,the as-prepared W_xMnO_(2)is treated as an ideal platform to scrutinize the correlations of the structure with the energy storage performance.The operando Raman spectra and finite element analysis have fully demonstrated the superiority of the locally ordered defects-enriched structure of W_(0.02)-MnO_(2),which could reach a favorable balance between the ion diffusion equilibrium time and the number of active sites.As a result,the W_(0.02)-MnO_(2)is able to deliver a high capacitance of 292 F·g^(-1)at a current density of 1 A·g^(-1)and a remarkable rate performance with a 60%capacity retention at a current density of 50 A·g^(-1).The further unveiled structure-performance relationship provides a guideline for the design of better pseudocapacitive energy storage devices.
