Sodium superionic conductor(NASICON)-type materials are promising cathodes for sodium-ion batteries due to their stable multi-channel frameworks and exceptional ionic conductivity.Among them,Na_(3)V_2(PO_4)_(2)F_(3)(N...Sodium superionic conductor(NASICON)-type materials are promising cathodes for sodium-ion batteries due to their stable multi-channel frameworks and exceptional ionic conductivity.Among them,Na_(3)V_2(PO_4)_(2)F_(3)(NVPF)has attracted significant attention.However,the low electronic conductivity and phase impurities limit its sodium storage capability.Herein,we present a Fe and Mn dual-doped NVPF(FM-NVPF)cathode with improved phase purity,electronic conductivity,and electrochemical activities.Detailed ex-situ analyses and density functional theory calculations reveal that Fe and Mn dopants induce defect energy levels and modulate the electronic structure,resulting in a direct-to-indirect bandgap transition in NVPF,which in turn increases carrier concentration and lifetime,accelerates ionic/electronic transport,and improves structural stability.As a result,the FM-NVPF cathode delivers a high capacity of 126.6 mAh g^(-1)at 0.1 C(1 C=128 mAh g^(-1))and outstanding high-rate capability of 67.6 mAh g^(-1)at 50 C,corresponding to 1.2 min per charge.Furthermore,Na ion full cells assembled with the FM-NVPF cathodes and hard carbon anodes exhibit a high energy density of about 175 Wh kg^(-1)_(cathode+anode mass)and appealing cyclic stability.This work provides an efficient strategy for developing high-purity and high-performance NVPF cathode materials for advanced sodium-ion batteries.展开更多
Rechargeable lithium-sulfur batteries have been regarded as the promising next generation energy storage system due to their overwhelming advantages in energy density.However,their practical implementations are hinder...Rechargeable lithium-sulfur batteries have been regarded as the promising next generation energy storage system due to their overwhelming advantages in energy density.However,their practical implementations are hindered by severe capacity fading and low sulfur utilization,which are caused by polysulfide shuttling and the insulating nature of sulfur.Herein,sulfur-embedded porous multichannel carbon nanofibers coated with MnO2 nanosheets(CNFs@S/MnO2)are rationally designed and fabricated as cathode for lithiumsulfur battery.The high conductivity of porous multichannel carbon nanofibers facilitates the kinetics of electron and ion transport in the electrodes,and the porous structure encapsulates and sequesters sulfur in its interior void space to physically retard the dissolution of high-order polysulfides.Moreover,the MnO2 shell exhibits a combination of physical and chemical adsorption for high-order polysulfides,which could sequester polysulfides leaked from the carbon matrix after long-time charge/discharge cycles,resulting in enhanced cyclic stability.As a result,the electrode delivers a specific capacity of 1286 m A h g^-1 at 0.1 C and 728 m A h g^-1 at 3 C.And the capacity could remain 774 m A h g^-1 after 600 cycles at 1 C.展开更多
基金supported by the Innovation and Technology Fund-Innovation and Technology Support Program(ITF-ITSP)(Project No.ITS/126/21)Research Talent Hub for ITF project(RTH-ITF)(Project No.K-45-35-ZWC6)from the Innovation and Technology Commission of Hong Kong SARResearch Institute for Advanced Manufacturing(RIAM)at The Hong Kong Polytechnic University(Project No.1-CD9C)。
文摘Sodium superionic conductor(NASICON)-type materials are promising cathodes for sodium-ion batteries due to their stable multi-channel frameworks and exceptional ionic conductivity.Among them,Na_(3)V_2(PO_4)_(2)F_(3)(NVPF)has attracted significant attention.However,the low electronic conductivity and phase impurities limit its sodium storage capability.Herein,we present a Fe and Mn dual-doped NVPF(FM-NVPF)cathode with improved phase purity,electronic conductivity,and electrochemical activities.Detailed ex-situ analyses and density functional theory calculations reveal that Fe and Mn dopants induce defect energy levels and modulate the electronic structure,resulting in a direct-to-indirect bandgap transition in NVPF,which in turn increases carrier concentration and lifetime,accelerates ionic/electronic transport,and improves structural stability.As a result,the FM-NVPF cathode delivers a high capacity of 126.6 mAh g^(-1)at 0.1 C(1 C=128 mAh g^(-1))and outstanding high-rate capability of 67.6 mAh g^(-1)at 50 C,corresponding to 1.2 min per charge.Furthermore,Na ion full cells assembled with the FM-NVPF cathodes and hard carbon anodes exhibit a high energy density of about 175 Wh kg^(-1)_(cathode+anode mass)and appealing cyclic stability.This work provides an efficient strategy for developing high-purity and high-performance NVPF cathode materials for advanced sodium-ion batteries.
基金supported by The Hong Kong Polytechnic University(1-ZVGH).
文摘Rechargeable lithium-sulfur batteries have been regarded as the promising next generation energy storage system due to their overwhelming advantages in energy density.However,their practical implementations are hindered by severe capacity fading and low sulfur utilization,which are caused by polysulfide shuttling and the insulating nature of sulfur.Herein,sulfur-embedded porous multichannel carbon nanofibers coated with MnO2 nanosheets(CNFs@S/MnO2)are rationally designed and fabricated as cathode for lithiumsulfur battery.The high conductivity of porous multichannel carbon nanofibers facilitates the kinetics of electron and ion transport in the electrodes,and the porous structure encapsulates and sequesters sulfur in its interior void space to physically retard the dissolution of high-order polysulfides.Moreover,the MnO2 shell exhibits a combination of physical and chemical adsorption for high-order polysulfides,which could sequester polysulfides leaked from the carbon matrix after long-time charge/discharge cycles,resulting in enhanced cyclic stability.As a result,the electrode delivers a specific capacity of 1286 m A h g^-1 at 0.1 C and 728 m A h g^-1 at 3 C.And the capacity could remain 774 m A h g^-1 after 600 cycles at 1 C.
