Inferior cycling stability, poor safety, and gas generation are long lasting problems of Ni-rich Li Ni0.80 Co0.10 Mn0.10 O2(NCM811) cathode material. Although much effort has been made, mechanisms for the above proble...Inferior cycling stability, poor safety, and gas generation are long lasting problems of Ni-rich Li Ni0.80 Co0.10 Mn0.10 O2(NCM811) cathode material. Although much effort has been made, mechanisms for the above problems are poorly understood. Studying the cycling and float-charging characteristics of Li/NCM811 cells in high voltage conditions(4.5 V and 4.7 V, respectively), in this work we find that nearly all known problems with NCM811 material can be attributed to the oxidation of lattice oxygen occurring in the capacity region corresponding to H2 → H3 phase transition. While contributing to overall capacity,the oxidation of lattice oxygen results in a loss of oxygen through oxygen evolution and relative reactions between active oxygen evolution intermediates and electrolyte solvents. It is the loss of oxygen that results in irreversible layered-spinel-rocksalt phase transition, secondary particle cracking, and performance degradation. The conclusions of this work suggest that the priority for further research on NCM811 material should give to the suppression of oxygen evolution, followed by the use of the anti-oxygen electrolyte being chemically stable against the active oxygen evolution intermediates.展开更多
Fast-charging is highly demanded for applications requiring short charging time.However,fast-charging triggers serious problems,leading to decline in charge acceptance and energy efficiency,accelerated capacity degrad...Fast-charging is highly demanded for applications requiring short charging time.However,fast-charging triggers serious problems,leading to decline in charge acceptance and energy efficiency,accelerated capacity degradation,and safety risk.In this work,a three-electrode coin cell with a Li metal reference electrode is designed to individually record the potential of two electrodes,and measure the impedance of each electrode by using a power-optimized graphite-LiNi0.80Co0.15Al0.05O2 electrode couple.It is shown that regardless of the state-of-charge the Li-ion cell's impedance is contributed predominantly by the cathode,and that the cathode's impedance is dominated by the charge-transfer resistance.In consistence with the impedance results,polarization of the Li-ion cell is dominated by the cathode.It is surprised to find that no Li plating occurs on the graphite anode even if the charging rate is increased to 10 C(1 C=1.30 mA cm^−2).The results of this work indicate that low overall impedance with a high cathode-to-anode impedance ratio is the key to enabling safe fast-charging,and that fast-charging Li-ion batteries without Li plating on the graphite anode is possible if the cathode and graphite anode are optimistically engineered.展开更多
Protonic ceramic fuel cells(PCFCs)offer a convenient means for electrochemical conversion of chemical energy into electricity at intermediate temperatures with very high efficiency.Although BaCeO_(3)-and BaZrO_(3)-bas...Protonic ceramic fuel cells(PCFCs)offer a convenient means for electrochemical conversion of chemical energy into electricity at intermediate temperatures with very high efficiency.Although BaCeO_(3)-and BaZrO_(3)-based complex oxides have been positioned as the most promising PCFC electrolytes,the design of new protonic conductors with improved properties is of paramount importance.Within the present work,we studied transport properties of scandium-doped barium stannate(Sc-doped BaSnO_(3)).Our analysis included the fabrication of porous and dense BaSn_(1−x)Sc_(x)O_(3−δ)ceramic materials(0≤x≤0.37),as well as a comprehensive analysis of their total,ionic,and electronic conductivities across all the experimental conditions realized under the PCFC operation:both air and hydrogen atmospheres with various water vapor partial pressures(p(H2O)),and a temperature range of 500–900℃.This work reports on electrolyte domain boundaries of the undoped and doped BaSnO_(3)for the first time,revealing that pure BaSnO_(3)exhibits mixed ionic–electronic conduction behavior under both oxidizing and reducing conditions,while the Sc-doping results in the gradual improvement of ionic(including protonic)conductivity,extending the electrolyte domain boundaries towards reduced atmospheres.This latter property makes the heavilydoped BaSnO_(3)representatives attractive for PCFC applications.展开更多
Lithium-rich oxide is one of the most promising cathodes that meet high energy density requirement for batteries of the future, but its phase transformation from layer to spinel structure caused by the lattice instabi...Lithium-rich oxide is one of the most promising cathodes that meet high energy density requirement for batteries of the future, but its phase transformation from layer to spinel structure caused by the lattice instability presents severe challenge to cycling stability and the actually accessible capacity. The currently available approaches to suppress this undesired irreversible process often resort to limit the high voltages that lithium-rich oxide is exposed to. However, cycling stability thus improved is at the expense of the eventual energy output. In this work, we identified a new mechanism that is directly responsible for the lithium-rich oxide phase transformation and established a clear correlation between the successive consumption of Li+on anode due to incessant interphase repairing and the over-delithiation of lithium-rich oxide cathode. This new mechanism enables a simple but effective solution to the cathode degradation, in which an electrolyte additive is used to build a dense and protective interphase on anode with the intention to minimize Li depletion at cathode. The application of this new interphase effectively suppresses both electrolyte decomposition at anode and the phase transformation of lithium-rich oxide cathode, leading to high capacity and cycling stability.展开更多
The molecular dynamics method is used to investigate the interaction between one-six nitrate anions and water clusters absorbing six ozone molecules. The infrared（IR） absorption and reflection spectra are reshaped s...The molecular dynamics method is used to investigate the interaction between one-six nitrate anions and water clusters absorbing six ozone molecules. The infrared（IR） absorption and reflection spectra are reshaped significantly, and new peaks appear at Raman spectra due to the addition of ozone and nitrate anions to the disperse water system. After ozone and nitrate anions are captured, the average（in frequency） IR reflection coefficient of the water disperse system increased drastically and the absorption coefficient fell.展开更多
Metallic coatings of many types can be applied to steel to provide outstanding, long-term corrosion protection. A thin A1 film is studied at an Fe substrate by the molecular dynamics method at temperatures ranging fro...Metallic coatings of many types can be applied to steel to provide outstanding, long-term corrosion protection. A thin A1 film is studied at an Fe substrate by the molecular dynamics method at temperatures ranging from 300 K to 1173 K. A1 atoms are found to penetrate the Fe matrix at a temperature of 873 K. The potential energy of the system changes step-like at a temperature of 1173 K. At such temperature mean square atomic displacement significantly changes. The behaviors of the A1 and Fe diffusion coefficients are mainly determined by the temperature dependence of the diffusion activation energy.展开更多
文摘Inferior cycling stability, poor safety, and gas generation are long lasting problems of Ni-rich Li Ni0.80 Co0.10 Mn0.10 O2(NCM811) cathode material. Although much effort has been made, mechanisms for the above problems are poorly understood. Studying the cycling and float-charging characteristics of Li/NCM811 cells in high voltage conditions(4.5 V and 4.7 V, respectively), in this work we find that nearly all known problems with NCM811 material can be attributed to the oxidation of lattice oxygen occurring in the capacity region corresponding to H2 → H3 phase transition. While contributing to overall capacity,the oxidation of lattice oxygen results in a loss of oxygen through oxygen evolution and relative reactions between active oxygen evolution intermediates and electrolyte solvents. It is the loss of oxygen that results in irreversible layered-spinel-rocksalt phase transition, secondary particle cracking, and performance degradation. The conclusions of this work suggest that the priority for further research on NCM811 material should give to the suppression of oxygen evolution, followed by the use of the anti-oxygen electrolyte being chemically stable against the active oxygen evolution intermediates.
基金Funding information Army Research Laboratory,Grant/Award Number:N/A
文摘Fast-charging is highly demanded for applications requiring short charging time.However,fast-charging triggers serious problems,leading to decline in charge acceptance and energy efficiency,accelerated capacity degradation,and safety risk.In this work,a three-electrode coin cell with a Li metal reference electrode is designed to individually record the potential of two electrodes,and measure the impedance of each electrode by using a power-optimized graphite-LiNi0.80Co0.15Al0.05O2 electrode couple.It is shown that regardless of the state-of-charge the Li-ion cell's impedance is contributed predominantly by the cathode,and that the cathode's impedance is dominated by the charge-transfer resistance.In consistence with the impedance results,polarization of the Li-ion cell is dominated by the cathode.It is surprised to find that no Li plating occurs on the graphite anode even if the charging rate is increased to 10 C(1 C=1.30 mA cm^−2).The results of this work indicate that low overall impedance with a high cathode-to-anode impedance ratio is the key to enabling safe fast-charging,and that fast-charging Li-ion batteries without Li plating on the graphite anode is possible if the cathode and graphite anode are optimistically engineered.
文摘Protonic ceramic fuel cells(PCFCs)offer a convenient means for electrochemical conversion of chemical energy into electricity at intermediate temperatures with very high efficiency.Although BaCeO_(3)-and BaZrO_(3)-based complex oxides have been positioned as the most promising PCFC electrolytes,the design of new protonic conductors with improved properties is of paramount importance.Within the present work,we studied transport properties of scandium-doped barium stannate(Sc-doped BaSnO_(3)).Our analysis included the fabrication of porous and dense BaSn_(1−x)Sc_(x)O_(3−δ)ceramic materials(0≤x≤0.37),as well as a comprehensive analysis of their total,ionic,and electronic conductivities across all the experimental conditions realized under the PCFC operation:both air and hydrogen atmospheres with various water vapor partial pressures(p(H2O)),and a temperature range of 500–900℃.This work reports on electrolyte domain boundaries of the undoped and doped BaSnO_(3)for the first time,revealing that pure BaSnO_(3)exhibits mixed ionic–electronic conduction behavior under both oxidizing and reducing conditions,while the Sc-doping results in the gradual improvement of ionic(including protonic)conductivity,extending the electrolyte domain boundaries towards reduced atmospheres.This latter property makes the heavilydoped BaSnO_(3)representatives attractive for PCFC applications.
基金supported by the National Natural Science Foundation of China(Grant No.21872058)the Key Project of Science and Technology in Guangdong Province(2017A010106006)
文摘Lithium-rich oxide is one of the most promising cathodes that meet high energy density requirement for batteries of the future, but its phase transformation from layer to spinel structure caused by the lattice instability presents severe challenge to cycling stability and the actually accessible capacity. The currently available approaches to suppress this undesired irreversible process often resort to limit the high voltages that lithium-rich oxide is exposed to. However, cycling stability thus improved is at the expense of the eventual energy output. In this work, we identified a new mechanism that is directly responsible for the lithium-rich oxide phase transformation and established a clear correlation between the successive consumption of Li+on anode due to incessant interphase repairing and the over-delithiation of lithium-rich oxide cathode. This new mechanism enables a simple but effective solution to the cathode degradation, in which an electrolyte additive is used to build a dense and protective interphase on anode with the intention to minimize Li depletion at cathode. The application of this new interphase effectively suppresses both electrolyte decomposition at anode and the phase transformation of lithium-rich oxide cathode, leading to high capacity and cycling stability.
文摘The molecular dynamics method is used to investigate the interaction between one-six nitrate anions and water clusters absorbing six ozone molecules. The infrared（IR） absorption and reflection spectra are reshaped significantly, and new peaks appear at Raman spectra due to the addition of ozone and nitrate anions to the disperse water system. After ozone and nitrate anions are captured, the average（in frequency） IR reflection coefficient of the water disperse system increased drastically and the absorption coefficient fell.
基金Project supported by the Ministry of Science and Education of the Russian Federation(Grant No.14.607.21.0035,unique identifier RFMEFI60714X0035)
文摘Metallic coatings of many types can be applied to steel to provide outstanding, long-term corrosion protection. A thin A1 film is studied at an Fe substrate by the molecular dynamics method at temperatures ranging from 300 K to 1173 K. A1 atoms are found to penetrate the Fe matrix at a temperature of 873 K. The potential energy of the system changes step-like at a temperature of 1173 K. At such temperature mean square atomic displacement significantly changes. The behaviors of the A1 and Fe diffusion coefficients are mainly determined by the temperature dependence of the diffusion activation energy.
