全固态无负极锂金属电池纳米化复合集流体构筑

全固态无负极锂金属电池(AFSSLB)是一种通过初次充电形成金属锂负极的新型锂电池,它的负极与正极容量比为1,能使任意锂化正极系统达到最大能量密度。无机固态电解质的引入使无负极锂金属体系兼具高安全性。然而,电池循环过程中的锂离子通量不均导致的界面接触损失和锂枝晶生长会不断加剧,从而造成电池循环容量迅速衰减。本文构筑了纳米化的银碳复合集流体,显著增强了全固态无负极锂金属电池中集流体-电解质界面的性能。使用该集流体的固态电池循环过程中接触良好,界面阻抗为~10Ω·cm^(-2)。从而实现了超过7.0mAh·cm^(-2)锂金属的均匀稳定沉积,并在0.25mA·cm^(-2)的电流条件下实现循环200次以上。

Femtosecond laser-inscribed optical waveguides in dielectric crystals:a concise review and recent advances

Femtosecond laser inscription or writing has been recognized as a powerful technique to engineer various materials toward a number of applications.By efficient modification of refractive indices of dielectric crystals,optical waveguides with diverse configurations have been produced by femtosecond laser writing.The waveguiding properties depend not only on the parameters of the laser writing but also on the nature of the crystals.The mode profile tailoring and polarization engineering are realizable by selecting appropriate fabrication conditions.In addition,regardless of the complexity of crystal refractive index changes induced by ultrafast pulses,several three-dimensional geometries have been designed and implemented that are useful for the fabrication of laser-written photonic chips.Some intriguing devices,e.g.,waveguide lasers,wavelength converters,and quantum memories,have been made,exhibiting potential for applications in various areas.Our work gives a concise review of the femtosecond laser-inscribed waveguides in dielectric crystals and focuses on the recent advances of this research area,including the fundamentals,fabrication,and selected photonic applications.

Tuning anionic/cationic redox chemistry in a P2-type Na0.67Mn0.5Fe0.5O2 cathode material via a synergic strategy

The anionic redox chemistry(O^2-→O^-)in P2-type sodium-ion battery cathodes has attracted much attention.However,determining how to tune the anionic redox reaction is still a major challenge.Herein,we tune the activity and reversibility of both the anionic and cationic redox reactions of Na0.67Mn0.5Fe0.5O2 though an integrated strategy that combines the advantages of Li2SiO3 coating,Li doping and Si doping,and the initial capacity,rate performance and cycling stability are significantly improved.The in-depth modulation mechanism is revealed by means of neutron diffraction,X-ray absorption spectroscopy,in situ X-ray diffraction,electron paramagnetic resonance spectroscopy,first-principles calculations and so on.The Li2SiO3 coating alleviates the side reactions and enhances the cycling stability.Si^4+doping lowers the Na^+diffusion barrier due to the expanded interlayer spacing.Additionally,Si^4+doping improves the structural stability,oxygen redox activity and reversibility.Li^+doping in Na sites further increases the structure stability.The electron density maps confirm the greater activity of Na and O in the modified sample.Nuclear density maps and bond-valence energy landscapes identify the Na^+migration pathway from Nae site to Naf site(the positions of the Na ions in the crystal structure).The proposed insights into the modulation mechanism of the anionic and cationic redox chemistry are also instructive for designing other oxide-based cathode materials.

Effect of OH^- on fluorescence properties in 1.5-1.6 μm for Er:Yb:YCOB crystal

FTIR absorption spectra indicate that H^+can easily enter the crystal structure and form OH^-centers in Er:Yb:YCOB and O-H bonds prefer to lie in the a-c plane.Within our current studied concentration level,crystal samples with higher OH-abso rption coefficie nts demonstrate stro nger fluo rescence intensity and longer fluorescence lifetime at 1535 nm.As the stretching vibration energy of OH-group approximately corresponds to the energy gap between the 4 I11/2 and 4 I13/2 levels of Er^3+,and thus,OH^-ions can shorten the fluorescence lifetime of Er^3+-4I11/2 level by the phonon-assisted cross-relaxation process between the Er^3+and OH-ions.Our curre nt results confirm that a certain conte nt of OH ions can enhance the ene rgy transfer process from Yb^3+to Er^3+and subsequently promote fluorescence output in 1.5-1.6μm.

Synthesis, crystal structure and thermal analysis of a new stilbazolium salt crystal

A new organic crystal of 4-N, N-dimethylamino-4＇-N＇-methyl-stilbazolium benzene sulfonate （DASBS） was synthesized and characterized for the first time. It is a derivative of 4-N, N-dimethylamino-4＇-N＇-methyl-stilbazolium tosylate （DAST） with the benzene sulfonate replacing p-toluenesulfonate. Single crystal XRD demonstrated that the crystal structure of DASBS. H20 was triclinic. The thermal analysis of this new crystal was also conducted, and the melting point was obtained to be 232℃.

In situ magnetometry study on the origin of anomalously capacity in transition metal sulfides

Cobalt sulfides are considered as promising candidates for lithium-ion battery(LIB)anode materials with high energy densities.Their energy storage mechanism is widely understood to involve the traditional intercalation and conversion reaction.However,these conventional mechanisms are unable to explain the storage capacities of certain materials which exceed the theoretical limit.Here,utilizing advanced in situ magnetometry to detect the magnetization evolution of Co_(1-x) S LIBs in real time,it is demonstrated that the Co-catalytic lithium storage process and interfacial space charge storage mechanism are strongly related to the additional capacity of cobalt sulfides.During discharge,a Co/Li_(2) S interface is formed,wherein the Co nanoparticles and Li_(2) S could store a large amount of polarized electrons Li^(+),respectively.Subsequently,the electrons stored in Co are transferred to the polymeric film,forming radical anions and contributing extra capacity.These findings reveal the charge storage mechanisms of transition metal sulfides and highlight the critical role of magnetic testing in the investigation of energy storage mechanisms.