Ni-rich layered oxides are considered promising cathodes for advanced lithium-ion batteries(LIBs)in the future,owing to their high capacity and low cost.However,the issues on structural and interfacial stability of Ni...Ni-rich layered oxides are considered promising cathodes for advanced lithium-ion batteries(LIBs)in the future,owing to their high capacity and low cost.However,the issues on structural and interfacial stability of Ni-rich cathodes still pose substantial obstacles in the practical application of advanced LIBs.Here,we employ a one-step method to synthesize a B-doped and La_(4)NiLiO_(8)-coated LiNi_(0.82)5Co_(0.115)Mn_(0.06)O_(2)(BL-1)cathode with reliable structure and interface,for the first time.The La_(4)NiLiO_(8)coating layer can prevent cathodes from electrolyte assault and facilitate Li+diffusion kinetics.Moreover,B-doping can effectively restrain the pernicious H_(2)-H_(3) phase transition and adjust the orientation of primary particles to a radial alignment,which is obstructive to the arise of microcracks induced by the change of anisotropic volume.Specifically,when tested in pouch cells,the BL-1 cathode exhibits outstanding capacity retention of 93.49%after 500 cycles at 1 C.This dual-modification strategy dramatically enhances the stability of the structure and interface for Ni-rich cathode materials,consequently accelerating the commercialization process of high-energy–density LIBs.展开更多
A pure dielectric metamaterial absorber with broadband and thin thickness is proposed,whose structure is designed as a periodic cross-hole array.The pure dielectric metamaterial absorber with high permittivity is prep...A pure dielectric metamaterial absorber with broadband and thin thickness is proposed,whose structure is designed as a periodic cross-hole array.The pure dielectric metamaterial absorber with high permittivity is prepared by ceramic reinforced polymer composites.Compared with those with low permittivity,the absorber with high permittivity is more sensitive to structural parameters,which means that it is easier to optimize the equivalent electromagnetic parameters and achieve wide impedance matching by altering the size or shape of the unit cell.The optimized metamaterial absorber exhibits reflection loss below-10 dB in 7.93 GHz–35.76 GHz with a thickness of 3.5 mm,which shows favorable absorption properties under the oblique incidence of TE polarization(±45°).Whether it is a measured or simulated value,the strongest absorbing peak reaches below-45 dB,which exceeds that of most metamaterial absorbers.The distributions of power loss density and electric and magnetic fields are investigated to study the origin of their strong absorbing properties.Multiple resonance mechanisms are proposed to explain the phenomenon,including polarization relaxation of the dielectric and edge effects of the cross-hole array.This work overcomes the shortcomings of the narrow absorbing bandwidth of dielectrics.It demonstrates that the pure dielectric metamaterial absorber with high permittivity has great potential in the field of microwave absorption.展开更多
基金financially supported by the National Natural Science Foundation of China(51774051,52072323,52122211)the Science and Technology Planning Project of Hunan Province(2019RS2034)+1 种基金the Hunan High-tech Industry Science and Technology Innovation Leading Plan(2020GK2072)the Changsha City Fund for Distinguished and Innovative Young Scholars(KQ1707014)。
文摘Ni-rich layered oxides are considered promising cathodes for advanced lithium-ion batteries(LIBs)in the future,owing to their high capacity and low cost.However,the issues on structural and interfacial stability of Ni-rich cathodes still pose substantial obstacles in the practical application of advanced LIBs.Here,we employ a one-step method to synthesize a B-doped and La_(4)NiLiO_(8)-coated LiNi_(0.82)5Co_(0.115)Mn_(0.06)O_(2)(BL-1)cathode with reliable structure and interface,for the first time.The La_(4)NiLiO_(8)coating layer can prevent cathodes from electrolyte assault and facilitate Li+diffusion kinetics.Moreover,B-doping can effectively restrain the pernicious H_(2)-H_(3) phase transition and adjust the orientation of primary particles to a radial alignment,which is obstructive to the arise of microcracks induced by the change of anisotropic volume.Specifically,when tested in pouch cells,the BL-1 cathode exhibits outstanding capacity retention of 93.49%after 500 cycles at 1 C.This dual-modification strategy dramatically enhances the stability of the structure and interface for Ni-rich cathode materials,consequently accelerating the commercialization process of high-energy–density LIBs.
基金Project supported in part by the Young Scientific and Technological Innovation Talents in Hunan,China(Grant No.2021RC3003)the Science and Technology Plan Project of Hunan Province,China(Grant No.2015TP1007)+1 种基金Initial Research Funding for Special Associate Professor by Central South University(Grant No.202045002)the National Natural Science Foundation for Young Scientists of China(Grant No.51802353)。
文摘A pure dielectric metamaterial absorber with broadband and thin thickness is proposed,whose structure is designed as a periodic cross-hole array.The pure dielectric metamaterial absorber with high permittivity is prepared by ceramic reinforced polymer composites.Compared with those with low permittivity,the absorber with high permittivity is more sensitive to structural parameters,which means that it is easier to optimize the equivalent electromagnetic parameters and achieve wide impedance matching by altering the size or shape of the unit cell.The optimized metamaterial absorber exhibits reflection loss below-10 dB in 7.93 GHz–35.76 GHz with a thickness of 3.5 mm,which shows favorable absorption properties under the oblique incidence of TE polarization(±45°).Whether it is a measured or simulated value,the strongest absorbing peak reaches below-45 dB,which exceeds that of most metamaterial absorbers.The distributions of power loss density and electric and magnetic fields are investigated to study the origin of their strong absorbing properties.Multiple resonance mechanisms are proposed to explain the phenomenon,including polarization relaxation of the dielectric and edge effects of the cross-hole array.This work overcomes the shortcomings of the narrow absorbing bandwidth of dielectrics.It demonstrates that the pure dielectric metamaterial absorber with high permittivity has great potential in the field of microwave absorption.
