原位表征技术在锂硫电池机理研究中的应用

商用锂离子电池的低能量密度已经无法满足电动汽车和电子设备迅速发展的需求,锂硫电池作为一种高能量密度、绿色环保且成本低廉的储能器件,已经成为储能领域的重要议题。然而,氧化还原动力学缓慢、穿梭效应严重、电解液耗竭以及锂负极的降解等问题依然阻碍着锂硫电池商业化的脚步。研究锂硫电池系统内各部件的基本反应机制对于解决以上问题,并进一步提高电池的整体性能至关重要。原位表征技术可用于锂硫电池充放电过程中各部件结构变化与反应进程的实时观察与研究,对锂硫电池机理的揭示有望从材料设计层面大幅提升电池整体性能。本文通过对近期研究工作进行总结,介绍了锂硫电池在提高循环寿命和高能量密度上遇到的瓶颈性问题,简述了原位拉曼光谱、原位透射电镜、原位共振非弹性X射线散射、原位红外光谱和原位核磁共振光谱等原位表征技术在锂硫电池中的应用。并结合锂硫电池涉及的氧化还原反应、多硫化物溶解、电解液对多硫化物的抑制以及锂负极降解等具体环节,重点分析了原位表征技术在这些具体环节中监测多硫化物转化过程和探究锂硫电池内部反应机理方面的研究进展,指出了原位表征技术在促进锂硫电池机理理解方面的重要作用。

“双一流”背景下工科类研究生工程实践能力提升的研究与探索

在加快推进“双一流”建设的背景下,紧密结合企事业单位对具备较强实践能力人才的需求,通过优化课程体系、建立多维考核评价机制,提升导师团队的实践能力、加强“双师型”师资队伍建设,深化产学研融合、加强研究生实践基地建设等举措,从研究生培养的各环节提升其实践能力,培养具备创新思维且能解决实际工程问题的高级人才。

高校大型仪器设备开放共享的制约因素及改进措施研究

高校大型仪器设备开放共享是提高国有资产利用率、推动科技创新、促进人才培养的有力举措。围绕大型仪器设备开放共享过程中的制约因素,结合湘潭大学大型仪器设备开放共享的实践经验,探讨了从科学配置仪器设备资源、完善现代化管理模式、强化实验技术队伍建设、健全考核制度和激励机制等方面推进大型仪器设备开放共享的改进措施及效果。

A new method to determine the elastoplastic properties of ductile materials by conical indentation

Based on load-displacement curves,indentation is widely used to extract the elastoplastic properties of materials.It is generally believed that such a measure is non-unique and a full stress-strain curve cannot be obtained using plural sharp and deep spherical indenters.In this paper we show that by introducing an additional dimensionless function of A/A (the ratio of residual area to the area of an indenter profile) in the reverse analysis,the elastoplastic properties of several unknown materials that exhibit visually indistinguishable load-displacement curves can be uniquely determined with a sharp indentation.

Damage and fracture with strain gradient plasticity for high-capacity electrodes of Li-ion batteries

In consideration of the high-density dislocations from the lithiation process of high-capacity electrodes in Li-ion batteries, in this paper, a new elastoplastic model is established to describe the diffusion-induced deformation and damage fracture. With the help of the relative physical quantities and state of charge, the surface damage and fracture behaviors of electrode materials are discussed based on the elastic-perfectly plastic(PP) and the strain gradient plasticity(SGP) theories, respectively. The results show that the lithiation deformation could be alleviated by reducing the electrode scale, and the plastic flow can play an essential role in the extrusion ratcheting effect relating to the upper surface fracture. Furthermore, the interface damage is more likely to appear by increasing the initial bond stiffness at the upper surface, which has little effect on the later fracture. A strong size effect is also found in the damage and fracture critical curves for the PP and SGP models.

Interface adhesion properties characterization of sulfide electrode materials by the combination of BOLS and XPS

Although sulfide electrode materials in lithium battery systems have been intensively investigated due to their low-cost, high theoretical specific capacity, and energy density, there are few studies fousing on the adhesion properties, including the physical origin of hetero-coordination resolved interface relaxation, binding energy and the energetic behavior, and even the accurate quantitative information. In this paper, we present an approach for quantifying the interface adhesion properties of sulfide electrode materials resolved by the combination of bond order-length-strength theory(BOLS) and X-ray photoelectron spectroscopy(XPS), which has enabled clarification of the interface adhesion nature. The results show that the Cu 2p, Fe 2p, and S 2p electrons of Cu S and FeS_(2) compounds shift negatively due to the charge polarization of the conduction electrons of the heteroatoms, while Mo 3d, Sn 3d electrons of Mo S2 and Sn S2 and the C 1 s and S 2p electrons of CS compound shift positively due to the quantum trapping. It is noted that the exact interface adhesion energies of Cu S is 3.42 J m^(-2), which is consistent with the calculation result. The approach can not only clarify the origin of the interface adhesion properties of sulfide electrode materials,but also derive their quantification information from atomistic sites.

Mesoscopic superelasticity,superplasticity,and superrigidity

Atomic-undercoordination-induced local bond contraction,bond strength gain,and the associated temperature (T)-dependent atomic-cohesive-energy and binding-energy-density are shown to originate intrinsically the exotic paradox of superplasticity,superelasticity,and superrigidity demonstrated by solid sizing from monatomic chain to mesoscopic grain.The paradox follows these relationships:(ε(K,T)y(K,T)σ(K,T))∝(exp(B/△T_(mk)),(η_1△T_(mk))d～(-3),[1+AK～(-2/2)exp(△T_(mk)/T)]△T_(mk)d～(-3)),(Plastic strain)(Elastic modulus)(Yield stress,IHPR)where A,B,η1,d and△T_(mk)=Tm(K) Tare size (K)-dependent physical parameters.Tm (K) is the melting point.Mechanical work hardening during compressing and self-heating during stretching modulate the measured outcome extrinsically.Superplasticity dominates in the solid-quasimolten-liquid transition state.The competition between the accumulation and annihilation of dislocations activates the inverse Hall-Petch relationship.Therefore,it is essential for one to discriminate the intrinsic competition between the local bond energy density gain and the atomic cohesive energy loss from the extrinsic factors of pressure and temperature in dealing with atomistic mechano-thermo dynamics.