Mixing polyanion cathode materials are promising candidates for the development of next-generation batteries, owing to their structural robustness and low-volume changes, yet low conductivity of polyanion hinders thei...Mixing polyanion cathode materials are promising candidates for the development of next-generation batteries, owing to their structural robustness and low-volume changes, yet low conductivity of polyanion hinders their practical capacity. Herein, the anion-site regulation is proposed to elevate the electrode kinetics and properties of polyanionic cathode. Multivalent anion P_(2)O_(7)^(4-) is selected to substitute the PO_(4)^(3-) in Na_(3)V_(2)(PO_(4))_(3) (NVP) lattice and regulate the ratio of polyanion groups to prepare Na_(3+x)V_(2)(PO_(4))_(3-x)(P_(2)O_(7))_(x)(NVPP_(x), 0 ≤ x ≤ 0.15) materials.The optimal Na_(3.1)V_(2)(PO_(4))_(2.9)(P_(2)O_(7))_(0.1) (NVPP_(0.1)) material can deliver remarkably elevated specific capacity(104 mAh g^(-1) at 0.1 C, 60 mAh g^(-1) at 20 C, respectively), which is higher than those of NVP. Moreover, NVPP_(0.1) exhibits outstanding cyclic stability(91% capacity retention after 300 cycles at 1 C). Experimental analyses reveal that the regulation of anions improves the structure stability, increases the active Na occupancy in the lattice and accelerates the Na+migration kinetics. The strategy of anion-site regulation provides the researchers a reference for the design of new high-performance polyanionic materials.展开更多
Iron-based mixed polyanion-type sodium-ion cathode materials like Na_(4)Fe_(3)(PO_(4))_(2)P_(2)O_(7)(NFPP)typically suffer from poor electronic conductivity,resulting in capacity retention under high-rate cycling and ...Iron-based mixed polyanion-type sodium-ion cathode materials like Na_(4)Fe_(3)(PO_(4))_(2)P_(2)O_(7)(NFPP)typically suffer from poor electronic conductivity,resulting in capacity retention under high-rate cycling and rapid capacity degradation.In this study,we introduce an innovative dual-carbon enhancement strategy that integrates carbon nanotubes(CNTs)into the precursor mixing stage,combined with citric acid as both an organic carbon source and a dispersant.Unlike conventional methods where CNTs are added post-synthesis or during slurry preparation-often leading to uneven dispersion-we incorporate CNTs during the initial mixing process.Citric acid not only provides carbon for pyrolysis but also forms a gel-like precursor that ensures homogeneous dispersion of CNTs and raw materials.This one-step sintering approach produces NFPP particles uniformly coated with carbon layers intimately connected to well-dispersed CNTs,potentially forming chemical bonds between them.The resulting pyrolytic carbon and CNT-coated NFPP(NFPP-CNT)exhibits a dense and interconnected electron-conductive network,significantly enhancing its electronic conductivity and electrochemical performance.The precisely designed NFPP-CNT delivers a reversible capacity of 111 mAh/g at 0.1 C and maintains a reversible capacity of 78.8 mAh/g even at an ultra-high rate of 100 C.NFPP-CNT also demonstrates outstanding high-rate capacity retention,with 85.7% capacity remaining after 27,000 cycles at 100 C.This novel synthesis method and the multifaceted role of citric acid endow NFPP with superior high-rate,long-cycle,and low-temperature performance,making it a highly competitive material for large-scale electric energy storage systems(EESs).展开更多
基金financially supported by the National Natural Science Foundation of China (No. 91963118)Science Technology Program of Jilin Province (No. 20200201066JC)+1 种基金“13th Five-Year” Science and Technology Research from the Education Department of Jilin Province (No.JJKH20201179KJ)the 111 Project (No. B13013)。
文摘Mixing polyanion cathode materials are promising candidates for the development of next-generation batteries, owing to their structural robustness and low-volume changes, yet low conductivity of polyanion hinders their practical capacity. Herein, the anion-site regulation is proposed to elevate the electrode kinetics and properties of polyanionic cathode. Multivalent anion P_(2)O_(7)^(4-) is selected to substitute the PO_(4)^(3-) in Na_(3)V_(2)(PO_(4))_(3) (NVP) lattice and regulate the ratio of polyanion groups to prepare Na_(3+x)V_(2)(PO_(4))_(3-x)(P_(2)O_(7))_(x)(NVPP_(x), 0 ≤ x ≤ 0.15) materials.The optimal Na_(3.1)V_(2)(PO_(4))_(2.9)(P_(2)O_(7))_(0.1) (NVPP_(0.1)) material can deliver remarkably elevated specific capacity(104 mAh g^(-1) at 0.1 C, 60 mAh g^(-1) at 20 C, respectively), which is higher than those of NVP. Moreover, NVPP_(0.1) exhibits outstanding cyclic stability(91% capacity retention after 300 cycles at 1 C). Experimental analyses reveal that the regulation of anions improves the structure stability, increases the active Na occupancy in the lattice and accelerates the Na+migration kinetics. The strategy of anion-site regulation provides the researchers a reference for the design of new high-performance polyanionic materials.
基金granted by the National Natural Science Foundation of China(Nos.52172210 and 51772163).
文摘Iron-based mixed polyanion-type sodium-ion cathode materials like Na_(4)Fe_(3)(PO_(4))_(2)P_(2)O_(7)(NFPP)typically suffer from poor electronic conductivity,resulting in capacity retention under high-rate cycling and rapid capacity degradation.In this study,we introduce an innovative dual-carbon enhancement strategy that integrates carbon nanotubes(CNTs)into the precursor mixing stage,combined with citric acid as both an organic carbon source and a dispersant.Unlike conventional methods where CNTs are added post-synthesis or during slurry preparation-often leading to uneven dispersion-we incorporate CNTs during the initial mixing process.Citric acid not only provides carbon for pyrolysis but also forms a gel-like precursor that ensures homogeneous dispersion of CNTs and raw materials.This one-step sintering approach produces NFPP particles uniformly coated with carbon layers intimately connected to well-dispersed CNTs,potentially forming chemical bonds between them.The resulting pyrolytic carbon and CNT-coated NFPP(NFPP-CNT)exhibits a dense and interconnected electron-conductive network,significantly enhancing its electronic conductivity and electrochemical performance.The precisely designed NFPP-CNT delivers a reversible capacity of 111 mAh/g at 0.1 C and maintains a reversible capacity of 78.8 mAh/g even at an ultra-high rate of 100 C.NFPP-CNT also demonstrates outstanding high-rate capacity retention,with 85.7% capacity remaining after 27,000 cycles at 100 C.This novel synthesis method and the multifaceted role of citric acid endow NFPP with superior high-rate,long-cycle,and low-temperature performance,making it a highly competitive material for large-scale electric energy storage systems(EESs).
