The lattice oxygen oxidation mechanism(LOM)provides an efficient pathway for accelerating the oxygen evolution reaction(OER)in certain electrocatalysts by activating and involving lattice oxygen in the catalytic OER p...The lattice oxygen oxidation mechanism(LOM)provides an efficient pathway for accelerating the oxygen evolution reaction(OER)in certain electrocatalysts by activating and involving lattice oxygen in the catalytic OER process.We investigated the potential of disordered rocksalts as catalysts for accelerating the OER through the LOM process,leveraging their unique metastable Li-O-Li bond states.Theoretical calculations were employed to predict the catalytic pathways and activities of disordered rocksalts(DRX),such as Li_(1.2)Co_(0.4)Ti_(0.5)O_(2)(LCTO).The results revealed that benefiting from the unhybridized Li-O electronic orbitals and the resulting metastable states of Li-O-Li bonds in DRX,LCTO exhibited a typical LOM pathway,and the lattice oxygen was easily activated and participated in the OER.The experimental results showed that LCTO exhibited a remarkable pH-dependent OER activity through the LOM pathway,with an overpotential of 241 mV at a current density of 10 mA/cm^(2),and excellent long-term stability.This work provides a novel chemical space for designing highly active and stable OER electrocatalysts by leveraging the LOM reaction pathway.展开更多
The electronic structures and optical properties of rocksalt indium nitride （INN） under pressure were studied using the first-principles calculation by considering the exchange and correlation potentials with the ge...The electronic structures and optical properties of rocksalt indium nitride （INN） under pressure were studied using the first-principles calculation by considering the exchange and correlation potentials with the generalized gradient approximation. The calculated lattice constant shows good agreement with the experimental value. It is interestingly found that the band gap energy Eg at the F or X point remarkably increases with increasing pressure, but Eg at the L point does not increase obviously. The pressure coefficient of Eg is calculated to be 44 meV/GPa at the F point. Moreover, the optical properties of rocksalt InN were calculated and discussed based on the calculated band structures and electronic density of states.展开更多
High‐entropy materials are emerging electrocatalysts by integrating five or more elements into one single crystallographic phase to optimize the electronic structures and geometric environments.Here,a rocksalt‐type ...High‐entropy materials are emerging electrocatalysts by integrating five or more elements into one single crystallographic phase to optimize the electronic structures and geometric environments.Here,a rocksalt‐type high‐entropy oxide Mg_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Zn_(0.2)O(HEO)is developed as an electrocatalyst towards the oxygen evolution reaction(OER).The obtained HEO features abundant cation and oxygen vacancies originating from the lattice mismatch of neighboring metal ions,together with enlarged Co/Ni‒O covalency due to the introduction of less electronegative Mg and Zn.As a result,the HEO exhibits superior intrinsic OER activities,delivering a turnover frequency(TOF)15 and 84 folds that of CoO and NiO at 1.65 V,respectively.This study provides a mechanistic understanding of the enhanced OER on HEO and demonstrates the potential of high‐entropy strategy in developing efficient oxygen electrocatalysts by elaborately incorporating low‐cost elements with lower electronegativity.展开更多
A thermo-plastic/viscoplastic damage coupled model was formulated to describe the time independent and time dependent behaviors of geomaterials under temperature effect. The plastic strain was divided into instantaneo...A thermo-plastic/viscoplastic damage coupled model was formulated to describe the time independent and time dependent behaviors of geomaterials under temperature effect. The plastic strain was divided into instantaneous plastic strain and creep plastic strain. To take temperature effect into acconnt, a temperature variable was introduced into the instantaneous and creep plastic behavior descriptions and damage characterization, and a linear thermal expansion law was used in constitutive equation formulation. According to the mechanical behavior of rock salt, a specific model was proposed based on the previous model and applied to Avery rock salt, in which the numerical results obtained from our model had a good agreement with the data from experiments.展开更多
Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,...Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,their practical implementation has been impeded by unwanted phenomena such as irrepressible transition metal migration/dissolution and O_(2)/CO_(2)evolution,which arise due to parasitic reactions and densification-degradation mechanisms during extended cycling.To address these issues,a micron-sized DRX cathode Li_(1.2)Ni_(1/3)Ti_(1/3)W_(2/15)O_(1.85)F_(0.15)(SLNTWOF)with F substitution and ultrathin LiF coating layer is developed by alcohols assisted sol-gel method.Within this fluorination-induced integrated structure design(FISD)strategy,in-situ F substitution modifies the activity/reversibility of the cationic-anionic redox reaction,while the ultrathin LiF coating and single-crystal structure synergistically mitigate the cathode/electrolyte parasitic reaction and densification-degradation mechanism.Attributed to the multiple modifications and size effect in the FISD strategy,the SLNTWOF sample exhibits reversible cationic-anionic redox chemistry with a meliorated reversible capacity of 290.3 mA h g^(-1)at 0.05C(1C=200 mA g^(-1)),improved cycling stability of 78.5%capacity retention after 50 cycles at 0.5 C,and modified rate capability of 102.8 mA h g^(-1)at 2 C.This work reveals that the synergistic effects between bulk structure modification,surface regulation,and engineering particle size can effectively modulate the distribution and evolution of cationic-anionic redox activities in DRX cathodes.展开更多
The development of cation-disordered rocksalt(DRX)cathodes has garnered worldwide attention due to their high capacity,broad chemical space and excellent structural flexibility.However,their low intrinsic Li-ion condu...The development of cation-disordered rocksalt(DRX)cathodes has garnered worldwide attention due to their high capacity,broad chemical space and excellent structural flexibility.However,their low intrinsic Li-ion conductivity necessitates extensive particle pulverization,typically achieved through ball-milling process,which impedes large-scale production.In this work,we present a proton-exchange assisted strategy to activate the Li-ion transport in Mn-based DRX cathodes.Short-range spinel-like ordering is observed to form within the DRX matrix after the post treatment,which significantly enhances the intrinsic Li ion mobility.Notably,more than 280 mAh g^(-1)discharge capacity can be delivered at a slow rate from micrometer-sized particles with an overall disordered cation arrangement,which retains more than150 m Ah g^(-1)when cycled at a very high rate of 2000 mA g^(-1).Furthermore,we also demonstrate that the electrochemical performance of the post-treated cathodes can be further optimized by fine-tuning the reaction parameters.展开更多
The reconstruction during oxygen evolution reaction (OER) significantly affects the electronic and local geometry structure of metal sites in electrocatalyst.Compared with well-investigated cobalt-based materials,the ...The reconstruction during oxygen evolution reaction (OER) significantly affects the electronic and local geometry structure of metal sites in electrocatalyst.Compared with well-investigated cobalt-based materials,the reconstruction of rocksalt CoO with purely Co^(2+) in octahedral (Oh) coordination has not been revealed in detail.Herein,monolayer Co O supported on reduced graphene oxide (r GO) was synthesized via a one-pot hydrothermal strategy with calcinating in Ar atmosphere.The structure evolution of twodimension (2D) Co O/r GO during OER was revealed by in situ X-ray absorption spectroscopy (XAS).The transition from Co O toward Co3O_(4) already occurred at open circuit potential,further enhanced at 1.23 V (vs.RHE).The Co Ox(OH)ywas determined as the active phase at 1.53 V,displaying a tetrahedral Co coordination defective spinel Co_(3)O_(4) with the Co-O shell that featured the (oxy)hydroxide,not the standard Co OOH.After OER,the irreversible transition from CoO to Co_(3)O_(4) was observed.In contrast,in situ Raman spectra revealed a reversible amorphization process on Co_(3)O_(4)/r GO under operation conditions.Furthermore,this study indicated that the reconstruction behavior could be more effectively revealed by XAS using 2D materials.展开更多
The structural, electronic and optical properties of rocksalt CdO have been studied using the plane-wave-based pseudo-potential density functional theory within generalized gradient approximation. The calculated latti...The structural, electronic and optical properties of rocksalt CdO have been studied using the plane-wave-based pseudo-potential density functional theory within generalized gradient approximation. The calculated lattice parameters are in agreement with previous experimental work. The band structure, density of states, and Mulliken charge population are obtained, which indicates that rocksalt CdO having the properties of a halfmetal due to an indirect band gap of -0.51eV. The mechanical properties show that rocksalt CdO is mechanically stable, isotropic and malleable. Significantly, we propose a correct value for ε1(0) of about 4.75, which offers theoretical data for the design and application for rocksalt CdO in optoelectronic materials.展开更多
Integrated rocksalt-polyanion cathodes(DRXPS)are promising candidates for next-generation lithium-ion battery cathode materials that combine high energy density,stable cycling performance,and reduced reliance on Co an...Integrated rocksalt-polyanion cathodes(DRXPS)are promising candidates for next-generation lithium-ion battery cathode materials that combine high energy density,stable cycling performance,and reduced reliance on Co and Ni.In this work,we investigated Li_(3)Mn_(1.6)P_(0.4)O_(5.4)F_(0.6),a new DRXPS cathode with fluoride incorporation.A pure spinel phase was formed and a discharge capacity retention of 84%was achieved after 200 cycles between 1.5 and 4.8 V versus Li/Li^(+).In comparison,the similarly synthesized Li_(3)Mn_(1.6)Nb_(0.4)O_(5.4)F_(0.6),in which all P^(5+)was substituted by Nb^(5+)while maintaining the same stoichiometry for all other elements,crystallized in a disordered rocksalt structure,and exhibited inferior capacity retention and rate capability than the P^(5+)counterpart.Our findings expand the compositional space of DRXPS to include F^(−),justify the viability of integrating polyanion groups in rocksalt-type cathodes,and highlight the superiority of P^(5+)as a cation charge compensator compared to the commonly used Nb^(5+).This work thereby advances the design of robust,high-performance cathode materials for sustainable batteries.展开更多
LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)is a high-capacity and widely used nickel-rich cathode material for lithium-ion batteries,but its fragile surface structure severely limits the cycle stability.In this work,by bl...LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)is a high-capacity and widely used nickel-rich cathode material for lithium-ion batteries,but its fragile surface structure severely limits the cycle stability.In this work,by blending the nano-sized LiCoO_(2)(nano-LCO)particles in NCM811 electrode,the surface structure reconstruction of NCM811 upon cycle is successfully achieved.Due to the short Li^(+)diffusion path within the nano-LCO particles,Li^(+)diffusion kinetics is significantly enhanced.Thus,when these nano-particles are blended in the NCM811 electrode,the Li^(+)extraction across the surface of NCM811 particles can be homogenized,which further promotes the uniformity of“layered/rocksalt(RS)”phase transitions in the surface region.This homogenization of surface state of charge(SOC)inhibits the rapid formation and thickening of the high-impedance RS phase,thereby enhancing the cycle and rate performances of NCM811-based electrode.This study deepens the understanding of the performance optimization mechanisms at the electrode level for NCM811-based electrodes.展开更多
基金supported by the National Natural Science Foundation of China(Nos.52177220,52231008)Key Research and Development Program of Hainan Province(ZDYF2022GXJS006)。
文摘The lattice oxygen oxidation mechanism(LOM)provides an efficient pathway for accelerating the oxygen evolution reaction(OER)in certain electrocatalysts by activating and involving lattice oxygen in the catalytic OER process.We investigated the potential of disordered rocksalts as catalysts for accelerating the OER through the LOM process,leveraging their unique metastable Li-O-Li bond states.Theoretical calculations were employed to predict the catalytic pathways and activities of disordered rocksalts(DRX),such as Li_(1.2)Co_(0.4)Ti_(0.5)O_(2)(LCTO).The results revealed that benefiting from the unhybridized Li-O electronic orbitals and the resulting metastable states of Li-O-Li bonds in DRX,LCTO exhibited a typical LOM pathway,and the lattice oxygen was easily activated and participated in the OER.The experimental results showed that LCTO exhibited a remarkable pH-dependent OER activity through the LOM pathway,with an overpotential of 241 mV at a current density of 10 mA/cm^(2),and excellent long-term stability.This work provides a novel chemical space for designing highly active and stable OER electrocatalysts by leveraging the LOM reaction pathway.
文摘The electronic structures and optical properties of rocksalt indium nitride （INN） under pressure were studied using the first-principles calculation by considering the exchange and correlation potentials with the generalized gradient approximation. The calculated lattice constant shows good agreement with the experimental value. It is interestingly found that the band gap energy Eg at the F or X point remarkably increases with increasing pressure, but Eg at the L point does not increase obviously. The pressure coefficient of Eg is calculated to be 44 meV/GPa at the F point. Moreover, the optical properties of rocksalt InN were calculated and discussed based on the calculated band structures and electronic density of states.
文摘High‐entropy materials are emerging electrocatalysts by integrating five or more elements into one single crystallographic phase to optimize the electronic structures and geometric environments.Here,a rocksalt‐type high‐entropy oxide Mg_(0.2)Co_(0.2)Ni_(0.2)Cu_(0.2)Zn_(0.2)O(HEO)is developed as an electrocatalyst towards the oxygen evolution reaction(OER).The obtained HEO features abundant cation and oxygen vacancies originating from the lattice mismatch of neighboring metal ions,together with enlarged Co/Ni‒O covalency due to the introduction of less electronegative Mg and Zn.As a result,the HEO exhibits superior intrinsic OER activities,delivering a turnover frequency(TOF)15 and 84 folds that of CoO and NiO at 1.65 V,respectively.This study provides a mechanistic understanding of the enhanced OER on HEO and demonstrates the potential of high‐entropy strategy in developing efficient oxygen electrocatalysts by elaborately incorporating low‐cost elements with lower electronegativity.
基金Project supported by the National Natural Science Foundation of China(NSFC) (Nos. 10772190,50979104 and 51009132)
文摘A thermo-plastic/viscoplastic damage coupled model was formulated to describe the time independent and time dependent behaviors of geomaterials under temperature effect. The plastic strain was divided into instantaneous plastic strain and creep plastic strain. To take temperature effect into acconnt, a temperature variable was introduced into the instantaneous and creep plastic behavior descriptions and damage characterization, and a linear thermal expansion law was used in constitutive equation formulation. According to the mechanical behavior of rock salt, a specific model was proposed based on the previous model and applied to Avery rock salt, in which the numerical results obtained from our model had a good agreement with the data from experiments.
基金supported by the National Key R&D Program of China(2021YFB2401800)the National Natural Science Foundation of China(22179008,21875022)+2 种基金the Natural Science Foundation of Chongqing,China(cstc2020jcyj-msxmX0589,cstc2020jcyjmsxmX0654)the support from Beijing Institute of Technology Research Fund Program for Young Scholarsthe 4B7B beamlines radiation equipment of Beijing Synchrotron Radiation Facility(2021-BEPC-PT-005924,2021-BEPC-PT-005967)。
文摘Cation-disordered rocksalt oxides(DRX)have been identified as promising cathode materials for high energy density applications owing to their variable elemental composition and cationic-anionic redox activity.However,their practical implementation has been impeded by unwanted phenomena such as irrepressible transition metal migration/dissolution and O_(2)/CO_(2)evolution,which arise due to parasitic reactions and densification-degradation mechanisms during extended cycling.To address these issues,a micron-sized DRX cathode Li_(1.2)Ni_(1/3)Ti_(1/3)W_(2/15)O_(1.85)F_(0.15)(SLNTWOF)with F substitution and ultrathin LiF coating layer is developed by alcohols assisted sol-gel method.Within this fluorination-induced integrated structure design(FISD)strategy,in-situ F substitution modifies the activity/reversibility of the cationic-anionic redox reaction,while the ultrathin LiF coating and single-crystal structure synergistically mitigate the cathode/electrolyte parasitic reaction and densification-degradation mechanism.Attributed to the multiple modifications and size effect in the FISD strategy,the SLNTWOF sample exhibits reversible cationic-anionic redox chemistry with a meliorated reversible capacity of 290.3 mA h g^(-1)at 0.05C(1C=200 mA g^(-1)),improved cycling stability of 78.5%capacity retention after 50 cycles at 0.5 C,and modified rate capability of 102.8 mA h g^(-1)at 2 C.This work reveals that the synergistic effects between bulk structure modification,surface regulation,and engineering particle size can effectively modulate the distribution and evolution of cationic-anionic redox activities in DRX cathodes.
基金funding support from the National Natural Science Foundation of Chinathe Institute of WeiqiaoUCAS Science and Technologythe Fundamental Research Funds for the Central Universities。
文摘The development of cation-disordered rocksalt(DRX)cathodes has garnered worldwide attention due to their high capacity,broad chemical space and excellent structural flexibility.However,their low intrinsic Li-ion conductivity necessitates extensive particle pulverization,typically achieved through ball-milling process,which impedes large-scale production.In this work,we present a proton-exchange assisted strategy to activate the Li-ion transport in Mn-based DRX cathodes.Short-range spinel-like ordering is observed to form within the DRX matrix after the post treatment,which significantly enhances the intrinsic Li ion mobility.Notably,more than 280 mAh g^(-1)discharge capacity can be delivered at a slow rate from micrometer-sized particles with an overall disordered cation arrangement,which retains more than150 m Ah g^(-1)when cycled at a very high rate of 2000 mA g^(-1).Furthermore,we also demonstrate that the electrochemical performance of the post-treated cathodes can be further optimized by fine-tuning the reaction parameters.
基金supported by the National Natural Science Foundation of China(21872093)the National Key Research and Development Program of China(2018YFB1502001)funding support from the Center of Hydrogen Science,Shanghai Jiao Tong University,China。
文摘The reconstruction during oxygen evolution reaction (OER) significantly affects the electronic and local geometry structure of metal sites in electrocatalyst.Compared with well-investigated cobalt-based materials,the reconstruction of rocksalt CoO with purely Co^(2+) in octahedral (Oh) coordination has not been revealed in detail.Herein,monolayer Co O supported on reduced graphene oxide (r GO) was synthesized via a one-pot hydrothermal strategy with calcinating in Ar atmosphere.The structure evolution of twodimension (2D) Co O/r GO during OER was revealed by in situ X-ray absorption spectroscopy (XAS).The transition from Co O toward Co3O_(4) already occurred at open circuit potential,further enhanced at 1.23 V (vs.RHE).The Co Ox(OH)ywas determined as the active phase at 1.53 V,displaying a tetrahedral Co coordination defective spinel Co_(3)O_(4) with the Co-O shell that featured the (oxy)hydroxide,not the standard Co OOH.After OER,the irreversible transition from CoO to Co_(3)O_(4) was observed.In contrast,in situ Raman spectra revealed a reversible amorphization process on Co_(3)O_(4)/r GO under operation conditions.Furthermore,this study indicated that the reconstruction behavior could be more effectively revealed by XAS using 2D materials.
文摘The structural, electronic and optical properties of rocksalt CdO have been studied using the plane-wave-based pseudo-potential density functional theory within generalized gradient approximation. The calculated lattice parameters are in agreement with previous experimental work. The band structure, density of states, and Mulliken charge population are obtained, which indicates that rocksalt CdO having the properties of a halfmetal due to an indirect band gap of -0.51eV. The mechanical properties show that rocksalt CdO is mechanically stable, isotropic and malleable. Significantly, we propose a correct value for ε1(0) of about 4.75, which offers theoretical data for the design and application for rocksalt CdO in optoelectronic materials.
基金sponsored by Tsinghua-Toyota Joint Research Fund.This study used resources of 18-ID and 23-ID-2 of the National Synchrotron Light Source II,a U.S.Department of Energy(DOE)Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No.DESC0012704.
文摘Integrated rocksalt-polyanion cathodes(DRXPS)are promising candidates for next-generation lithium-ion battery cathode materials that combine high energy density,stable cycling performance,and reduced reliance on Co and Ni.In this work,we investigated Li_(3)Mn_(1.6)P_(0.4)O_(5.4)F_(0.6),a new DRXPS cathode with fluoride incorporation.A pure spinel phase was formed and a discharge capacity retention of 84%was achieved after 200 cycles between 1.5 and 4.8 V versus Li/Li^(+).In comparison,the similarly synthesized Li_(3)Mn_(1.6)Nb_(0.4)O_(5.4)F_(0.6),in which all P^(5+)was substituted by Nb^(5+)while maintaining the same stoichiometry for all other elements,crystallized in a disordered rocksalt structure,and exhibited inferior capacity retention and rate capability than the P^(5+)counterpart.Our findings expand the compositional space of DRXPS to include F^(−),justify the viability of integrating polyanion groups in rocksalt-type cathodes,and highlight the superiority of P^(5+)as a cation charge compensator compared to the commonly used Nb^(5+).This work thereby advances the design of robust,high-performance cathode materials for sustainable batteries.
基金supported by the National Natural Science Foundation of China(No.92472206)the Major Science and Technology Infrastructure Project of Material Genome Big-science Facilities Platform supported by Municipal Development and Reform Commission of Shenzhen,the International joint Research Center for Electric Vehicle Power Battery and Materials(No.2015B01015)+1 种基金Guangdong Key Laboratory of Design and Calculation of New Energy Materials(No.2017B030301013)Shenzhen Key Laboratory of New Energy Resources Genome Preparation and Testing(No.ZDSYS201707281026184).
文摘LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)is a high-capacity and widely used nickel-rich cathode material for lithium-ion batteries,but its fragile surface structure severely limits the cycle stability.In this work,by blending the nano-sized LiCoO_(2)(nano-LCO)particles in NCM811 electrode,the surface structure reconstruction of NCM811 upon cycle is successfully achieved.Due to the short Li^(+)diffusion path within the nano-LCO particles,Li^(+)diffusion kinetics is significantly enhanced.Thus,when these nano-particles are blended in the NCM811 electrode,the Li^(+)extraction across the surface of NCM811 particles can be homogenized,which further promotes the uniformity of“layered/rocksalt(RS)”phase transitions in the surface region.This homogenization of surface state of charge(SOC)inhibits the rapid formation and thickening of the high-impedance RS phase,thereby enhancing the cycle and rate performances of NCM811-based electrode.This study deepens the understanding of the performance optimization mechanisms at the electrode level for NCM811-based electrodes.
