Layered LiCoO_(2)(LCO)acts as a dominant cathode material for lithium-ion batteries(LIBs)in 3C products because of its high compacted density and volumetric energy density.Although improving the high cutoff voltage is...Layered LiCoO_(2)(LCO)acts as a dominant cathode material for lithium-ion batteries(LIBs)in 3C products because of its high compacted density and volumetric energy density.Although improving the high cutoff voltage is an effective strategy to increase its capacity,such behavior would trigger rapid capacity decay due to the surface or/and structure degradation.Herein,we propose a bi-functional surface strategy involving constructing a robust spinel-like phase coating layer with great integrity and compatibility to LiCoO_(2) and modulating crystal lattice by anion and cation gradient co-doping at the subsurface.As a result,the modified LiCoO_(2)(AFM-LCO)shows a capacity retention of 80.9%after 500 cycles between 3.0and 4.6 V.The Al,F,Mg enriched spinel-like phase coating layer serves as a robust physical barrier to effectively inhibit the undesired side reactions between the electrolyte and the cathode.Meanwhile,the Al,F,Mg gradient co-doping significantly enhances the surficial structure stability,suppresses Co dissolution and oxygen release,providing a stable path for Li-ions mobility all through the long-term cycles.Thus,the surface bi-functional strategy is an effective method to synergistically improve the electrochemical performances of LCO at a high cut-off voltage of 4.6 V.展开更多
LiCoO_(2) is the preferred cathode material for consumer electronic products due to its high volumetric energy density. However, the unfavorable phase transition and surface oxygen release limits the practical applica...LiCoO_(2) is the preferred cathode material for consumer electronic products due to its high volumetric energy density. However, the unfavorable phase transition and surface oxygen release limits the practical application of LiCoO_(2)at a high-voltage of 4.6 V to achieve a higher energy density demanded by the market. Herein, both bulk and surface structures of LiCoO_(2)are stabilized at 4.6 V through oxygen charge regulation by Gd-gradient doping. The enrichment of highly electropositive Gd on LiCoO_(2) surface will increase the effective charge on oxygen and improve the oxygen framework stability against oxygen loss.On the other hand, Gd ions occupy the Co-sites and suppress the unfavorable phase transition and microcrack. The modified LiCoO_(2) exhibits superior cycling stability with capacity retention of 90.1% over 200 cycles at 4.6 V, and also obtains a high capacity of 145.7 m Ah/g at 5 C. This work shows great promise for developing high-voltage LiCoO_(2) at 4.6 V and the strategy could also contribute to optimizing other cathode materials with high voltage and large capacity, such as cobalt-free high-nickel and lithiumrich manganese-based cathode materials.展开更多
Increasing the charging cut-off potential of lithium cobalt oxide(LiCoO_(2),LCO)can effectively improve the energy density of the lithium-ion batteries,which are the mainstream energy storage devices used in 3C electr...Increasing the charging cut-off potential of lithium cobalt oxide(LiCoO_(2),LCO)can effectively improve the energy density of the lithium-ion batteries,which are the mainstream energy storage devices used in 3C electronic products.However,the continuous decomposition of the electrolyte and dissolution of Co from the electrode will occur at high-potential operation,which deteriorate the performances of LCO.Here,a cathode-electrolyte interface(CEI)layer containing Mg F_(2)is constructed to enhance the electrochemical stability of LCO at 4.6 V(vs.Li^(+)/Li).The Mg^(2+)added to the cathode gradually releases into the electrolyte during cycling,which forms a stable Mg F_(2)-rich protective layer.In addition,1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether(TTE)is added to the electrolyte acting as a F source to increase the content of Mg F_(2)in the CEI layer.The Mg F_(2)-rich CEI layer effectively suppresses the decomposition of electrolyte components and the dissolution of Co of LCO,which makes the Li||LiCoO_(2)(Li||LCO)cell cycled stably at 3~4.6 V(vs.Li^(+)/Li)in 200 cycles with a retention of 83.9%.展开更多
We report our numerical simulation on dispersive waves （DWs） generated in the Kr-filled Kagome hollow-core photonic crystal fiber, by deploying the unidirectional pulse propagation equation. Relatively strong disper...We report our numerical simulation on dispersive waves （DWs） generated in the Kr-filled Kagome hollow-core photonic crystal fiber, by deploying the unidirectional pulse propagation equation. Relatively strong dispersive waves are simultaneously generated at 2.5μm and 4.6μm. It is deciphered that the interplay between plasma currents due to Kr ionization and nonlinear effects plays a key role in DW generation. Remarkably, this kind of DW generation is corroborated by the plasma-corrected phase-matching condition.展开更多
The quantum cascade laser(QCL),a potential laser source for mid-infrared applications,has all of the advantages of a semiconductor laser,such as small volume and light weight,and is driven by electric power.However,th...The quantum cascade laser(QCL),a potential laser source for mid-infrared applications,has all of the advantages of a semiconductor laser,such as small volume and light weight,and is driven by electric power.However,the optical power of a single QCL is limited by serious self-heating efects.Therefore,beam combination technology is essential to achieve higher laser powers.In this letter,we demonstrate a simple beam combination scheme using two QCLs to extend the output peak power of the lasers to 2.3 W.A high beam combination efciency of 89% and beam quality factor of less than 5 are also achieved.展开更多
基金supported by the National Natural Science Foundation of China(22075170,52072233)the Beijing National Laboratory for Condensed Matter Physics。
文摘Layered LiCoO_(2)(LCO)acts as a dominant cathode material for lithium-ion batteries(LIBs)in 3C products because of its high compacted density and volumetric energy density.Although improving the high cutoff voltage is an effective strategy to increase its capacity,such behavior would trigger rapid capacity decay due to the surface or/and structure degradation.Herein,we propose a bi-functional surface strategy involving constructing a robust spinel-like phase coating layer with great integrity and compatibility to LiCoO_(2) and modulating crystal lattice by anion and cation gradient co-doping at the subsurface.As a result,the modified LiCoO_(2)(AFM-LCO)shows a capacity retention of 80.9%after 500 cycles between 3.0and 4.6 V.The Al,F,Mg enriched spinel-like phase coating layer serves as a robust physical barrier to effectively inhibit the undesired side reactions between the electrolyte and the cathode.Meanwhile,the Al,F,Mg gradient co-doping significantly enhances the surficial structure stability,suppresses Co dissolution and oxygen release,providing a stable path for Li-ions mobility all through the long-term cycles.Thus,the surface bi-functional strategy is an effective method to synergistically improve the electrochemical performances of LCO at a high cut-off voltage of 4.6 V.
基金supported by the National Natural Science Foundation of China (52102249, 52172201, 51732005, 51902118)the China Postdoctoral Science Foundation (2019M662609 and 2020T130217)+1 种基金the international postdoctoral exchange fellowship program (PC2021026)the Major Technological Innovation Project of Hubei Province (2019AAA019) for financial support。
文摘LiCoO_(2) is the preferred cathode material for consumer electronic products due to its high volumetric energy density. However, the unfavorable phase transition and surface oxygen release limits the practical application of LiCoO_(2)at a high-voltage of 4.6 V to achieve a higher energy density demanded by the market. Herein, both bulk and surface structures of LiCoO_(2)are stabilized at 4.6 V through oxygen charge regulation by Gd-gradient doping. The enrichment of highly electropositive Gd on LiCoO_(2) surface will increase the effective charge on oxygen and improve the oxygen framework stability against oxygen loss.On the other hand, Gd ions occupy the Co-sites and suppress the unfavorable phase transition and microcrack. The modified LiCoO_(2) exhibits superior cycling stability with capacity retention of 90.1% over 200 cycles at 4.6 V, and also obtains a high capacity of 145.7 m Ah/g at 5 C. This work shows great promise for developing high-voltage LiCoO_(2) at 4.6 V and the strategy could also contribute to optimizing other cathode materials with high voltage and large capacity, such as cobalt-free high-nickel and lithiumrich manganese-based cathode materials.
基金supported by National Natural Science Foundation of China(Nos.22075172 and 22075170)the Opening Project of Key Laboratory of Optoelectronic Chemical Materials and Devices of Ministry of Education,Jianghan University(No.JDGD202221)。
文摘Increasing the charging cut-off potential of lithium cobalt oxide(LiCoO_(2),LCO)can effectively improve the energy density of the lithium-ion batteries,which are the mainstream energy storage devices used in 3C electronic products.However,the continuous decomposition of the electrolyte and dissolution of Co from the electrode will occur at high-potential operation,which deteriorate the performances of LCO.Here,a cathode-electrolyte interface(CEI)layer containing Mg F_(2)is constructed to enhance the electrochemical stability of LCO at 4.6 V(vs.Li^(+)/Li).The Mg^(2+)added to the cathode gradually releases into the electrolyte during cycling,which forms a stable Mg F_(2)-rich protective layer.In addition,1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether(TTE)is added to the electrolyte acting as a F source to increase the content of Mg F_(2)in the CEI layer.The Mg F_(2)-rich CEI layer effectively suppresses the decomposition of electrolyte components and the dissolution of Co of LCO,which makes the Li||LiCoO_(2)(Li||LCO)cell cycled stably at 3~4.6 V(vs.Li^(+)/Li)in 200 cycles with a retention of 83.9%.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11674243 and 11674242
文摘We report our numerical simulation on dispersive waves （DWs） generated in the Kr-filled Kagome hollow-core photonic crystal fiber, by deploying the unidirectional pulse propagation equation. Relatively strong dispersive waves are simultaneously generated at 2.5μm and 4.6μm. It is deciphered that the interplay between plasma currents due to Kr ionization and nonlinear effects plays a key role in DW generation. Remarkably, this kind of DW generation is corroborated by the plasma-corrected phase-matching condition.
基金supported by the National Natural Science Foundation of China(Nos.61076064 and 61176046)the International Science Technology Cooperation Program of China(No.2013DFR00730)the Hundred Talents Program of Chinese Academy of Sciences for their fnancial support
文摘The quantum cascade laser(QCL),a potential laser source for mid-infrared applications,has all of the advantages of a semiconductor laser,such as small volume and light weight,and is driven by electric power.However,the optical power of a single QCL is limited by serious self-heating efects.Therefore,beam combination technology is essential to achieve higher laser powers.In this letter,we demonstrate a simple beam combination scheme using two QCLs to extend the output peak power of the lasers to 2.3 W.A high beam combination efciency of 89% and beam quality factor of less than 5 are also achieved.
