The enhancement of the fluorination degree of carbon fluorides(CF_(x))compounds is the most effective method to improve the energy densities of Li/CF_(x)batteries because the specific capacity of CF_(x)is proportional...The enhancement of the fluorination degree of carbon fluorides(CF_(x))compounds is the most effective method to improve the energy densities of Li/CF_(x)batteries because the specific capacity of CF_(x)is proportional to the molar ratio of F to C atoms(F/C).In this study,B-doped graphene(BG)is prepared by using boric acid as the doping source and then the prepared BG is utilized as the starting material for the preparation of CF_(x).The B-doping enhances the F/C ratio of CF_(x)without hindering the electrochemical activity of the C–F bond.During the fluorination process,B-containing functional groups are removed from the graphene lattice.This facilitates the formation of a defect-rich graphene matrix,which not only enhances the F/C ratio due to abundant perfluorinated groups at the defective edges but also serves as the active site for extra Li+storage.The prepared CF_(x)exhibits the maximum specific capacity of 1204 mAh g^(−1),which is 39.2%higher than that of CF_(x)obtained directly from graphene oxide(without B-doping).An unprecedented energy density of 2974 Wh kg^(−1)is achieved for the asprepared CF_(x)samples,which is significantly higher than the theoretically calculated energy density of commercially available fluorinated graphite(2180 Wh kg^(−1)).Therefore,this study demonstrates a great potential of B-doping to realize the ultrahigh energy density of CF_(x)cathodes for practical applications.展开更多
The development of all-solid-state lithium batteries(ASSLBs)depends on exploiting solid-state electrolytes(SSEs)with high ionic conductivity and electrochemical stability.Fluorination is generally considered to be an ...The development of all-solid-state lithium batteries(ASSLBs)depends on exploiting solid-state electrolytes(SSEs)with high ionic conductivity and electrochemical stability.Fluorination is generally considered to be an effective strategy to improve the ionic conductivity and electrochemical stability of inorganic SSEs.Here,we report the partial fluorination of the chlo rine sites in an antiperovskite,by which the orthorhombic Li_(2)OHCl was transformed into cubic Li_(2)OHCl_(0.9)F_(0.1),resulting in a fourfold increase in ionic conductivity at 30℃.The ab initio molecular dynamics simulations suggest that both the crystal symmetry and the anions electronegativity influence the diffusion of Li+in the antiperovskite structure.Besides,from the perspective of experiments and calculations,it is confirmed that fluorination is a feasible method to improve the electrochemical stability of antiperovskite SSEs.The LiFePO_(4)|Li cell based on Li_(2)OHCl_(0.9)F_(0.1) is also assembled and exhibits stable cycle performance,which indicates that fluorination of antiperovskite SSEs is an effective way to produce high-performance SSEs for practical application of ASSLBs.展开更多
Lithium(Li)metal anodes have attracted extensive attention due to their ultrahigh theoretical capacity and low potential.However,the uneven deposition of Li near the unstable electrode/electrolyte interfaces leads to ...Lithium(Li)metal anodes have attracted extensive attention due to their ultrahigh theoretical capacity and low potential.However,the uneven deposition of Li near the unstable electrode/electrolyte interfaces leads to the growth of Li dendrites and the degradation of active electrodes.Herein,we directly fluorinate alkyne-containing conjugated microporous polymers(ACMPs)microspheres with fluorine gas(F_(2))to introduce a novel fluorinated interlayer as an interfacial stabilizer in lithium metal batteries.Using density functional theory methods,it is found that as-prepared fluorinated ACMP(FACMP)has abundant partially ionic C–F bonds.The C–F bonds with electrochemical lability yield remarkable lithiophilicity during cycling.The in situ reactions between the active C–F bonds and Li ions enable transfer of lithium fluoride microcrystals to the solid electrolyte interphase(SEI)layers,guaranteeing effective ionic distribution and smooth Li deposition.Consequently,Li metal electrodes with the fluorinated interlayers demonstrate excellent cycling performances in both half-batteries and full cells with a lithium bis(trifluoromethanesulfonyl)imide electrolyte as well as a nonfluorinated lithium bis(oxalate)borate electrolyte system.This strategy is highly significant in customizable SEI layers to stabilize electrode interfaces and ensure high utilization of Li metal anodes,especially in a nonfluorinated electrolyte.展开更多
As growing applications demand higher driving currents of oxide semiconductor thin-film transistors(TFTs),severe instabilities and even hard breakdown under high-current stress(HCS)become critical challenges.In this w...As growing applications demand higher driving currents of oxide semiconductor thin-film transistors(TFTs),severe instabilities and even hard breakdown under high-current stress(HCS)become critical challenges.In this work,the triggering voltage of HCS-induced self-heating(SH)degradation is defined in the output characteristics of amorphous indium-galliumzinc oxide(a-IGZO)TFTs,and used to quantitatively evaluate the thermal generation process of channel donor defects.The fluorinated a-IGZO(a-IGZO:F)was adopted to effectively retard the triggering of the self-heating(SH)effect,and was supposed to originate from the less population of initial deep-state defects and a slower rate of thermal defect transition in a-IGZO:F.The proposed scheme noticeably enhances the high-current applications of oxide TFTs.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
基金financialy supported by the State Key Program of National Natural Science Foundation of China(no.52130303)the National Natural Science Foundation of China(no.51773147 and 51973151)
文摘The enhancement of the fluorination degree of carbon fluorides(CF_(x))compounds is the most effective method to improve the energy densities of Li/CF_(x)batteries because the specific capacity of CF_(x)is proportional to the molar ratio of F to C atoms(F/C).In this study,B-doped graphene(BG)is prepared by using boric acid as the doping source and then the prepared BG is utilized as the starting material for the preparation of CF_(x).The B-doping enhances the F/C ratio of CF_(x)without hindering the electrochemical activity of the C–F bond.During the fluorination process,B-containing functional groups are removed from the graphene lattice.This facilitates the formation of a defect-rich graphene matrix,which not only enhances the F/C ratio due to abundant perfluorinated groups at the defective edges but also serves as the active site for extra Li+storage.The prepared CF_(x)exhibits the maximum specific capacity of 1204 mAh g^(−1),which is 39.2%higher than that of CF_(x)obtained directly from graphene oxide(without B-doping).An unprecedented energy density of 2974 Wh kg^(−1)is achieved for the asprepared CF_(x)samples,which is significantly higher than the theoretically calculated energy density of commercially available fluorinated graphite(2180 Wh kg^(−1)).Therefore,this study demonstrates a great potential of B-doping to realize the ultrahigh energy density of CF_(x)cathodes for practical applications.
基金supported by the National Key Research and Development Program of China(2020YFA0210701)the National Natural Science Foundation of China(22005134,12275119,U22A20439)+4 种基金the Shenzhen Science and Technology Program(RCBS20210609103647030)the Guangdong Basic and Applied Basic Research Foundation(2021A1515012403)the Shenzhen Science and Technology Program(KQTD20200820113047086)the Guangdong-Hong Kong-Macao Joint Laboratory for PhotonicThermal-Electrical Energy Materials and Devices(2019B121205001)the open research fund of Songshan Lake Materials Laboratory(2022SLABFK04)。
文摘The development of all-solid-state lithium batteries(ASSLBs)depends on exploiting solid-state electrolytes(SSEs)with high ionic conductivity and electrochemical stability.Fluorination is generally considered to be an effective strategy to improve the ionic conductivity and electrochemical stability of inorganic SSEs.Here,we report the partial fluorination of the chlo rine sites in an antiperovskite,by which the orthorhombic Li_(2)OHCl was transformed into cubic Li_(2)OHCl_(0.9)F_(0.1),resulting in a fourfold increase in ionic conductivity at 30℃.The ab initio molecular dynamics simulations suggest that both the crystal symmetry and the anions electronegativity influence the diffusion of Li+in the antiperovskite structure.Besides,from the perspective of experiments and calculations,it is confirmed that fluorination is a feasible method to improve the electrochemical stability of antiperovskite SSEs.The LiFePO_(4)|Li cell based on Li_(2)OHCl_(0.9)F_(0.1) is also assembled and exhibits stable cycle performance,which indicates that fluorination of antiperovskite SSEs is an effective way to produce high-performance SSEs for practical application of ASSLBs.
基金Science Foundation for Distinguished Young Scholars in Tianjin,Grant/Award Number:19JCJQJC61700National Natural Science Foundation of China,Grant/Award Numbers:51773147,51973151,52130303National Key R&D Program of China,Grant/Award Number:2022YFB3805702。
文摘Lithium(Li)metal anodes have attracted extensive attention due to their ultrahigh theoretical capacity and low potential.However,the uneven deposition of Li near the unstable electrode/electrolyte interfaces leads to the growth of Li dendrites and the degradation of active electrodes.Herein,we directly fluorinate alkyne-containing conjugated microporous polymers(ACMPs)microspheres with fluorine gas(F_(2))to introduce a novel fluorinated interlayer as an interfacial stabilizer in lithium metal batteries.Using density functional theory methods,it is found that as-prepared fluorinated ACMP(FACMP)has abundant partially ionic C–F bonds.The C–F bonds with electrochemical lability yield remarkable lithiophilicity during cycling.The in situ reactions between the active C–F bonds and Li ions enable transfer of lithium fluoride microcrystals to the solid electrolyte interphase(SEI)layers,guaranteeing effective ionic distribution and smooth Li deposition.Consequently,Li metal electrodes with the fluorinated interlayers demonstrate excellent cycling performances in both half-batteries and full cells with a lithium bis(trifluoromethanesulfonyl)imide electrolyte as well as a nonfluorinated lithium bis(oxalate)borate electrolyte system.This strategy is highly significant in customizable SEI layers to stabilize electrode interfaces and ensure high utilization of Li metal anodes,especially in a nonfluorinated electrolyte.
基金supported by National Key Research and Development Program under Grant No.2022YFB3607100Shenzhen Research Programs under Grant Nos.JCYJ20200109140601691,JCYJ20190808154803565,SGDX20201103095607022,SGDX20211123145404006,and GXWD20201231165807007-20200807025846001。
文摘As growing applications demand higher driving currents of oxide semiconductor thin-film transistors(TFTs),severe instabilities and even hard breakdown under high-current stress(HCS)become critical challenges.In this work,the triggering voltage of HCS-induced self-heating(SH)degradation is defined in the output characteristics of amorphous indium-galliumzinc oxide(a-IGZO)TFTs,and used to quantitatively evaluate the thermal generation process of channel donor defects.The fluorinated a-IGZO(a-IGZO:F)was adopted to effectively retard the triggering of the self-heating(SH)effect,and was supposed to originate from the less population of initial deep-state defects and a slower rate of thermal defect transition in a-IGZO:F.The proposed scheme noticeably enhances the high-current applications of oxide TFTs.
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.
