Hybrid sodium-ion capacitors(SICs)bridge the gap between the supercapacitors(SCs)and batteries and have huge potential applications in large-scale energy storage.However,designing appropriate anode materials with fast...Hybrid sodium-ion capacitors(SICs)bridge the gap between the supercapacitors(SCs)and batteries and have huge potential applications in large-scale energy storage.However,designing appropriate anode materials with fast kinetics behavior as well as long cycle life to match with the cathode electrodes remains a crucial challenge.Herein,Nb2O5 nanotubes and nanowire-to-nanotube homo-junctions were directly grown on the carbon cloth(CC)via a simple hydrothermal process through regulating the pH value of solution.The as-prepared Nb2O5@CC nanotubes displayed a high reversible capacity of 175 mA hg-1 at the current density of 1Ag-1 with the coulombic efficiency of 97%after 1500 cycles.Besides,the SICs fabricated with Nb2O5@CC and activated carbon(AC)electrode materials showed a high energy density of 195 W h kg-1 at 120 W kg-1,a power density of 7328 W kg-1 at 28 W hkg-1and 80%of the capacitance retention after 5000 cycles.Additionally,the flexible SIC devices can operate normally at various bendable conditions.The Nb2O5@CC nanotubes in this work can be promising electrode materials in flexible and wearable energy storage devices.展开更多
Although organic electrode materials have merits of abundant resources,diverse structures and environmental friendliness,their performance for electrochemical energy storage is far insufficient.In this work,a thiourea...Although organic electrode materials have merits of abundant resources,diverse structures and environmental friendliness,their performance for electrochemical energy storage is far insufficient.In this work,a thiourea-based polyimide/reduced graphene oxide(PNTCSA/RGO)composite was synthesized via a condensation polymerization method.As a cathode material in lithium-ion batteries,excellent performance is demonstrated with high reversible capacity(144.2 mA h g^−1),high discharge voltage(∼2.5 V),and long cycling life(over 2000 cycles at 500 mA g^−1),which are comparable to those of other well documented in organic electrodes.Encouraging electrochemical performance is also demonstrated for sodium ion batteries(a cycling life of 800 cycles at 500 mA g^−1),while poor performance is delivered in potassium ion batteries.Theoretical studies reveal that the active sites are carbonyl groups for all alkali ions but one inserted alkali metal ion is shared by two carbonyl groups from the two neighbor units.More importantly,K ions have stronger interaction with S atoms than Li/Na ions,which may lead to poor structure reversibility and account for the poor cycling performance.Our findings provide a fundamental understanding of polyimide based polymer electrodes and help to design and develop high performance organic electrode materials for alkali metal ion batteries.展开更多
基金supported by the National Natural Science Foundation of China(5167230851972025 and 61888102)。
文摘Hybrid sodium-ion capacitors(SICs)bridge the gap between the supercapacitors(SCs)and batteries and have huge potential applications in large-scale energy storage.However,designing appropriate anode materials with fast kinetics behavior as well as long cycle life to match with the cathode electrodes remains a crucial challenge.Herein,Nb2O5 nanotubes and nanowire-to-nanotube homo-junctions were directly grown on the carbon cloth(CC)via a simple hydrothermal process through regulating the pH value of solution.The as-prepared Nb2O5@CC nanotubes displayed a high reversible capacity of 175 mA hg-1 at the current density of 1Ag-1 with the coulombic efficiency of 97%after 1500 cycles.Besides,the SICs fabricated with Nb2O5@CC and activated carbon(AC)electrode materials showed a high energy density of 195 W h kg-1 at 120 W kg-1,a power density of 7328 W kg-1 at 28 W hkg-1and 80%of the capacitance retention after 5000 cycles.Additionally,the flexible SIC devices can operate normally at various bendable conditions.The Nb2O5@CC nanotubes in this work can be promising electrode materials in flexible and wearable energy storage devices.
基金This work was financially supported by the National Natural Science Foundation of China(51672188 and 21703036).
文摘Although organic electrode materials have merits of abundant resources,diverse structures and environmental friendliness,their performance for electrochemical energy storage is far insufficient.In this work,a thiourea-based polyimide/reduced graphene oxide(PNTCSA/RGO)composite was synthesized via a condensation polymerization method.As a cathode material in lithium-ion batteries,excellent performance is demonstrated with high reversible capacity(144.2 mA h g^−1),high discharge voltage(∼2.5 V),and long cycling life(over 2000 cycles at 500 mA g^−1),which are comparable to those of other well documented in organic electrodes.Encouraging electrochemical performance is also demonstrated for sodium ion batteries(a cycling life of 800 cycles at 500 mA g^−1),while poor performance is delivered in potassium ion batteries.Theoretical studies reveal that the active sites are carbonyl groups for all alkali ions but one inserted alkali metal ion is shared by two carbonyl groups from the two neighbor units.More importantly,K ions have stronger interaction with S atoms than Li/Na ions,which may lead to poor structure reversibility and account for the poor cycling performance.Our findings provide a fundamental understanding of polyimide based polymer electrodes and help to design and develop high performance organic electrode materials for alkali metal ion batteries.
