Thermal Stability and Outgassing Behaviors of High-nickel Cathodes in Lithium-ion Batteries

LiNiO₂-based high-nickel layered oxide cathodes are regarded as promising cathode materials for high-energy-density automotive lithium batteries. Most of the attention thus far has been paid towards addressing their surface and structural instability issues brought by the increase of Ni content (>90 %) with an aim to enhance the cycle stability. However, the poor safety performance remains an intractable problem for their commercialization in the market, yet it has not received appropriate attention. In this review, we focus on the gas generation and thermal degradation behaviors of high-Ni cathodes, which are critical factors in determining their overall safety performance. A comprehensive overview of the mechanisms of outgassing and thermal runaway reactions is presented and analyzed from a chemistry perspective. Finally, we discuss the challenges and the insights into developing robust, safe high-Ni cathodes.     

An Aurivillius Oxide Based Cathode with Excellent CO2 Tolerance for Intermediate‐Temperature Solid Oxide Fuel Cells

The Aurivillius oxide Bi₂Sr₂Nb₂MnO_12?δ (BSNM) was used as a cobalt‐free cathode for intermediate‐temperature solid oxide fuel cells (IT‐SOFCs). To the best of our knowledge, the BSNM oxide is the only alkaline‐earth‐containing cathode material with complete CO₂ tolerance that has been reported thus far. BSNM not only shows favorable activity in the oxygen reduction reaction (ORR) at intermediate temperatures but also exhibits a low thermal expansion coefficient, excellent structural stability, and good chemical compatibility with the electrolyte. These features highlight the potential of the new BSNM material as a highly promising cathode material for IT‐SOFCs.     

In situ formed FeS2@CoS cathode for long cycling life lithium-ion battery

Pyrite FeS₂ exhibits an ultrahigh energy density (1671 W·h·kg^-1, for the reaction of FeS₂+4Li=Fe+2Li₂S) in secondary lithium-ion batteries, but its poor cycling stability, huge volume expansion, the shuttle effect of polysulfides, and slow kinetic properties limit its practical application. In this work, we synthesize a composite structure material CoS on FeS₂ surface (FeS_x@CoS, 1 < x ≤ 2) by using a cobalt-containing MOF to improve its cycle stability. It is found that CoS inhibits the side reactions and adsorbs polysulfides. As a result, the modified FeS₂ shows a higher discharge capacity of 577 mA·h·g^-1 (919 W·h·kg^-1) after 60 cycles than 484 mA·h·g^-1 (778 W·h·kg^-1) of bare pyrite FeS₂. This efficient strategy provides a valuable step toward the realization of high cycling stability FeS₂ cathode materials for secondary lithium-ion batteries and enriches the basic understanding of the influence of FeS₂ interfacial stability on its electrochemical performances.     

A Layered P2‐ and O3‐Type Composite as a High‐Energy Cathode for Rechargeable Sodium‐Ion Batteries

A layered composite with P2 and O3 integration is proposed toward a sodium‐ion battery with high energy density and long cycle life. The integration of P2 and O3 structures in this layered oxide is clearly characterized by XRD refinement, SAED and HAADF and ABF‐STEM at atomic resolution. The biphase synergy in this layered P2+O3 composite is well established during the electrochemical reaction. This layered composite can deliver a high reversible capacity with the largest energy density of 640 mAh g^?1, and it also presents good capacity retention over 150 times of sodium extraction and insertion.     

Methods of Increasing Sensitivity of Non-Coincidental Sharp Line Sources for AAS: Magnetic Control of Hollow Cathodes

Preliminary investigations were carried out on the magnetic effects on the emission of hollow cathode lamps as applied to overlap sources. It was found that a measurable increase in sensitivity was obtained for Mn, Ni and Cu when using a iron hollow cathode under a magnetic flux of 3400 gauss.     

Infrared and Raman spectroscopy of nanostructured LT-LiCoO2 cathodes for Li-ion rechargeable batteries

Nano-engineered electrodes, such as porous LiCoO₂, exhibit improved electrochemical performance compared to the non-porous LiCoO₂ analogue. Structural studies of the pore walls composing the nanostructured LiCoO₂ materials have focused on long-range (diffraction) methods. However, the powder diffraction patterns of the low-temperature (LT) and high-temperature (HT) phases of non-porous LiCoO₂ are very similar and distinguishing the two phases can be challenging. In this work, infrared and Raman spectroscopy are used to unambiguously assign the LiCoO₂ crystalline domains present in two porous compounds (nanowire LiCoO₂ and mesoporous LiCoO₂) as LT-LiCoO₂. Moreover, the appearance of new bands in the infrared spectrum of LiCoO₂ nanowires might signal the presence of disordered LiCoO₂ domains that are XRD silent.     

锂硫电池系统研究与展望

锂硫电池具有高的理论比容量（1675 mAh·g^-1）和能量密度（2600 Wh·kg^-1）,是一种新型的高性能储能电池。本文全面介绍了锂硫电池最新的基础研究,详细阐述了电池的正极、黏合剂、电解质、隔膜、负极和一些最新的锂硫电池组装与结构设计。硫可以和其他材料以不同方式复合后作为正极来提高电池的导电性以及抑制其电池充放电过程中的“穿梭效应”,以此来改善电池性能;在黏合剂和电解质研究方面,可以选择一些与电极配套和功能性的黏合剂以及不同类型的电解质;同样,在隔膜方面也涉及到隔膜类型的选择、复合与改性处理;在负极方面,对于锂片负极可采用涂覆保护薄膜或膜预锂化处理等方法来改善电池的稳定性和安全性;在一些新颖的电池组合方面,过渡层、新型集流体的运用以及电池结构的新设计也极大提高了电池电化学性能。最后,本文分析了现有锂硫电池存在的缺陷和问题,并对未来可能的发展方向进行了预测。     

Gallium arsenide and (alga)as devices prepared by Liquid-Phase epitaxy (Review Article)

Gallium arsenide and (AlGa)As devices and their preparative techniques based on liquid-phase epitaxy are reviewed. Included are discussions of dopants, growth apparatus and structures used in light emission, electron emission, photodetection, and microwave systems.