Low-cost room-temperature sodium-ion batteries (SIBs) are expected to promote the development of stationary energy storage applications.However,due to the large size of Na+,most Na+ host structures resembling their Li...Low-cost room-temperature sodium-ion batteries (SIBs) are expected to promote the development of stationary energy storage applications.However,due to the large size of Na+,most Na+ host structures resembling their Li+ counterparts show sluggish ion mobility and destructive volume changes during Na ion (de)intercalation,resulting in unsatisfactory rate and cycling performances.Herein,we report a new type of sodium iron phosphate (Na0.71Fe1.07PO4),which exhibits an extremely small volume change (~ 1%) during desodiation.When applied as a cathode material for SIBs,this new phosphate delivers a capacity of 78 mA·h·g-1 even at a high rate of 50 C and maintains its capacity over 5,000 cycles at 20 C.In situ synchrotron characterization disclosed a highly reversible solid-solution mechanism during charging/discharging.The findings are believed to contribute to the development of high-performance batteries based on Earth-abundant elements.展开更多
Designing low-cost and high-performance catalysts of electrocatalytic oxygen evolution reaction(OER)has always been one of the hot topics in current research.Hexagonal perovskite materials show great application poten...Designing low-cost and high-performance catalysts of electrocatalytic oxygen evolution reaction(OER)has always been one of the hot topics in current research.Hexagonal perovskite materials show great application potential in this field.Here,we synthesized 5%Iridium(Ir)-doped hexagonal phase perovskite BaCo_(0.8)Fe_(0.15)Ir_(0.05)O_(3–δ)(BCFI).Using the Rietveld method to refine the structure,combining with the spherical aberration corrected high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)atomic imaging,we found that BCFI is a ten-layer hexagonal(10H)structure,which belongs to the Purn:x-wiley:1001604X:media:cjoc202200200:cjoc202200200-math-0001m2 space group.In addition,BCFI shows excellent OER catalytic effect and good stability in 1 mol/L KOH solution,and the overpotential reaches 294 mV at a current density of 10 mA cm^(–2).The reduction of Cobalt(Co)valence state induced by Ir doping significantly enhances the OER activity of BCFI.Meanwhile,density functional theory(DFT)calculations show that the 2p-band center of oxygen(O)in BCFI is closer to the Fermi level than that in undoped BaCo_(0.8)Fe_(0.15)Ir_(0.05)O_(3–δ)(BCF),which is beneficial to the OER.This work reveals a novel 10H-BCFI material with excellent OER performance,and provides a basis for the design of hexagonal perovskite materials in OER and other energy conversion fields.展开更多
Main observation and conclusion Perovskites(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(x=0.02,0.05,0.1 denoted as BSCF-0.98,BSCF-0.95,BSCF-0.9,respectively)with A-site cation defects are synthesized by simple and...Main observation and conclusion Perovskites(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(x=0.02,0.05,0.1 denoted as BSCF-0.98,BSCF-0.95,BSCF-0.9,respectively)with A-site cation defects are synthesized by simple and efficient sol-gel method and are proved to have better OER catalytic effect than the well-known(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF)oxides.BSCF-0.95 exhibits the best OER catalytic activity in the series perovskite.The current density of BSCF-0.95 is about 56%higher than that of BSCF oxide at a potential of 1.7 V.The experimental studies have shown that compared with BSCF,BSCF-0.95 oxide has a larger electrochemical surface area(ECSA),a higher content of O_(2)^(2–)species related to surface oxygen vacancies,and faster charge transfer rate,which may be the factors for the enhancement of OER activity.The theoretical calculation results prove that the center positions of the O 2p-band of perovskite with A-site cation defects are closer to the Fermi level than BSCF oxide,which agrees with the OER performance trend of the material.展开更多
文摘Low-cost room-temperature sodium-ion batteries (SIBs) are expected to promote the development of stationary energy storage applications.However,due to the large size of Na+,most Na+ host structures resembling their Li+ counterparts show sluggish ion mobility and destructive volume changes during Na ion (de)intercalation,resulting in unsatisfactory rate and cycling performances.Herein,we report a new type of sodium iron phosphate (Na0.71Fe1.07PO4),which exhibits an extremely small volume change (~ 1%) during desodiation.When applied as a cathode material for SIBs,this new phosphate delivers a capacity of 78 mA·h·g-1 even at a high rate of 50 C and maintains its capacity over 5,000 cycles at 20 C.In situ synchrotron characterization disclosed a highly reversible solid-solution mechanism during charging/discharging.The findings are believed to contribute to the development of high-performance batteries based on Earth-abundant elements.
基金This workwas supported by the National Natural Science Foundation of China(No.21671182)the National Key R&D Program of China(No.2021YFB4001401).
文摘Designing low-cost and high-performance catalysts of electrocatalytic oxygen evolution reaction(OER)has always been one of the hot topics in current research.Hexagonal perovskite materials show great application potential in this field.Here,we synthesized 5%Iridium(Ir)-doped hexagonal phase perovskite BaCo_(0.8)Fe_(0.15)Ir_(0.05)O_(3–δ)(BCFI).Using the Rietveld method to refine the structure,combining with the spherical aberration corrected high-angle annular dark-field scanning transmission electron microscopy(HAADF-STEM)atomic imaging,we found that BCFI is a ten-layer hexagonal(10H)structure,which belongs to the Purn:x-wiley:1001604X:media:cjoc202200200:cjoc202200200-math-0001m2 space group.In addition,BCFI shows excellent OER catalytic effect and good stability in 1 mol/L KOH solution,and the overpotential reaches 294 mV at a current density of 10 mA cm^(–2).The reduction of Cobalt(Co)valence state induced by Ir doping significantly enhances the OER activity of BCFI.Meanwhile,density functional theory(DFT)calculations show that the 2p-band center of oxygen(O)in BCFI is closer to the Fermi level than that in undoped BaCo_(0.8)Fe_(0.15)Ir_(0.05)O_(3–δ)(BCF),which is beneficial to the OER.This work reveals a novel 10H-BCFI material with excellent OER performance,and provides a basis for the design of hexagonal perovskite materials in OER and other energy conversion fields.
基金supported by the National Natural Science Foundation of China(No.21671182)the Fundamental Research Funds for the Central Universities(WK3430000005))The calculations were performed on the supercomputing center of the University of Science and Technology of China(USTC-SCC).
文摘Main observation and conclusion Perovskites(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(x=0.02,0.05,0.1 denoted as BSCF-0.98,BSCF-0.95,BSCF-0.9,respectively)with A-site cation defects are synthesized by simple and efficient sol-gel method and are proved to have better OER catalytic effect than the well-known(Ba_(0.5)Sr_(0.5))_(1-x)Co_(0.8)Fe_(0.2)O_(3-δ)(BSCF)oxides.BSCF-0.95 exhibits the best OER catalytic activity in the series perovskite.The current density of BSCF-0.95 is about 56%higher than that of BSCF oxide at a potential of 1.7 V.The experimental studies have shown that compared with BSCF,BSCF-0.95 oxide has a larger electrochemical surface area(ECSA),a higher content of O_(2)^(2–)species related to surface oxygen vacancies,and faster charge transfer rate,which may be the factors for the enhancement of OER activity.The theoretical calculation results prove that the center positions of the O 2p-band of perovskite with A-site cation defects are closer to the Fermi level than BSCF oxide,which agrees with the OER performance trend of the material.
