Particles in composite polymer electrolyte for solid-state lithium batteries:A review

Solid-state lithium batteries(SSLBs)have been identified as one kind of the most promising energy conversion and storage devices because of their safety,high en...     

全固态锂电池界面的机械失效模型综述

全固态锂电池具有高能量密度和高安全性能等优点,有望替代传统锂电池成为下一代可移动储备．然而,全固态结构也给这种新型电池的应用带来全新的挑战,阻碍其商业化的进程,其中很重要的一个挑战就是机械不稳定性．首先,尽管固态电解质具有较高刚度与强度,理论上应该可以阻挡锂枝晶的穿透,但在其使用过程中仍能观察到锂枝晶的生长,这与高刚度电解质可抵制锂枝晶生长的理论相悖．其次,与液态电解质相比,固态电解质刚度大,在电极活性材料充放电时不能始终保持与活性材料的有效接触,可能导致活性颗粒和电解质的界面分层．因此,解释这些现象并提供解决策略对促进全固态锂电池的广泛应用至关重要．本文旨在总结近年来关于全固态锂电池不同界面处机械失效的力化耦合模型,主要包括以下两个方面：(1) 锂金属负极与固态电解质界面处锂枝晶的形成与生长;(2) 活性颗粒锂化/脱锂化引起的界面分层和破裂．本文从理论模型的角度总结了全固态锂离子电池中不同界面上的机械失效行为,旨在为全固态锂离子电池的模型建立与结构优化提供借鉴思路．     

聚合物／无机纳米复合材料润滑油添加剂的摩擦学功能设计

选择3种具有不同抗磨性能的纳米组分,制备了具有不同界面特性的聚合物／无机纳米复合材料;考察了纳米复合材料的减摩抗磨性能和机理,探讨了关于纳米复合材料润滑油添加剂的摩擦学功能设计准则。结果表明：对聚合物与无机纳米组分界面进行设计优化后能明显提高纳米复合材料的摩擦学性能。实现聚合物与无机纳米组分界面的优化设计后,聚合物与无机纳米组分之间具有更好的相容性,无机纳米组分在聚合物基体中分布更均匀;当聚合物基体在摩擦热和剪切作用下熔融分解后,裸露出来的具有高活性的无机纳米组分可在摩擦副接触表面形成具有良好摩擦学性能的表面膜。     

Roles of metal element substitutions from the bimetallic solid state electrolytes in lithium batteries

All-solid-state lithium batteries (ASSLBs), receiving extensive attentions and studies, exhibit better safety, environmental friendliness, stability, wider electrochemical stability window and higher energy density than traditionally liquid lithium batteries. In a variety of inorganic materials, with highly replaceable, the non-lithium metal elements emerge in endlessly and affect performances in diversiform ways. Due to facile preparation, convertible structures and excellent properties, the lithium-containing bimetallic granular materials are often applied as important components of electrolytes in lithium batteries. In this review, in terms of the properties of substituted elements, changing crystal structures, increasing vacancies or defects and improving the interfacial conductions, the roles of metal element substitutions of inorganic particles on the improvement of solid-state electrolytes are expounded. And the applications of substituted strategies in ASSLBs as the host of inorganic particles electrolytes and as fillers or modifications for composite electrolytes are also investigated and discussed. It also summarizes the current concerns and obstacles that need to be broken through, as well as provides a basis guide for the selection and optimization of inorganic particles.     

Investigation into Electromechanical Properties of Biocompatible Chitosan-Based Ionic Actuator

Ionic actuators have attracted much attention due to their remarkably large strain under low-voltage stimulation. Here, we investigate a highly biocompatible ionic polymer actuator, which consists of multi-walled carbon nanotube (MCNT) film as a double electrode layer and an electrolyte layer equipped with chitosan polymer skeleton and ionic liquid. As a result, with the thickness increase of the electrolyte layer and the electrode layer, the membrane capacitance values are obviously improved, which are 0.01 F (membrane thickness of 1.3 mm) and 0.4 F (0.25 mm). The blocking force and its response speed show peak values of 5.75 mN (1.1 mm) and 5.1 mN (0.25 mm), while reverse increases for the displacement and its response speed are observed, which present maximum values of 10.3 mm (0.3 mm) and 13.3 mm (0.15 mm). Furthermore, for various thicknesses of the electrode layers under applied direct current of 5 V, the generated strain of 0.15 mm thickness (59%) is 4.92 times greater than that of the 0.25 mm thickness. This is against the strain difference on the electrode surface due to the growing stiffness of the electrode layer. Additionally, from the experiments of the electromechanical energy efficiency of various electrode layers and electrolyte layers, our actuator exhibits excellent electromechanical energy efficiency under a high electrical conductivity of the electrode layer, which enhance the specific electromechanical energy up to 9.95%.     

Balancing particle properties for practical lithium-ion batteries

As a state-of-the-art secondary battery, lithium-ion batteries (LIBs) have dominated the consumer electronics market since Sony unveiled the commercial secondary battery with LiCoO₂ as the negative electrode material in the early 1990s. The key to the efficient operation of LIBs lies in the effective contact between the Li-ion-rich electrolyte and the active material particles in the electrode. The particle properties of the electrode materials affect the lithium ion diffusion path, diffusion resistance, contact area with the active material, the electrochemical performance and the energy density of batteries. To achieve satisfied comprehensive performance and of LIBs, it is not only necessary to focus on the modification of materials, but also to balance the properties of electrode material particles. Therefore, in this review, we analyze the influence of particle properties on the battery performance from three perspectives: particle size, particle size distribution, and particle shape. A deep understanding of the effect and mechanism of particles on electrodes and batteries will help develop and manufacture practical LIBs.     

SHEAR TEST AND FINITE ELEMENT SIMULATION OF POLYURETHANE POLYMER GROUTING MATERIALS1)

通过扭转试验对高聚物注浆材料剪切性能进行试验研究,并在扫描电子显微镜(scanning electron microscope, SEM) 下观测了试件断面处胞体形状破坏特征,在此基础上通过有限元数值模拟,对其剪切变形力学响应特征及剪应力分布规律进行了研究。结果表明：密度对高聚物材料的剪切强度及剪切模量影响显著,且随着高聚物材料密度的增加,其剪切强度和剪切模量被显著提升;高聚物材料胞体分布遵循能量最低原理,密度越大,胞体表面积越小,表面能越小,体系越稳定;面心立方体堆砌模型可以较好模拟材料剪切变形行为,且密度越大,拟合效果越好。     

Carbonate-salt-based composite materials for medium- and high-temperature thermal energy storage

This paper discusses composite materials based on inorganic salts for medium- and high-temperature thermal energy storage application. The composites consist of a phase change material （PCM）, a ceramic material, and a high thermal conductivity material. The ceramic material forms a microstructural skeleton for encapsulation of the PCM and structural stability of the composites; the high thermal conductivity material enhances the overall thermal conductivity of the composites. Using a eutectic salt of lithium and sodium carbonates as the PCM, magnesium oxide as the ceramic skeleton, and either graphite flakes or carbon nanotubes as the thermal conductivity enhancer, we produced composites with good physical and chemical stability and high thermal conductivity. We found that the wettability of the molten salt on the ceramic and carbon materials significantly affects the microstructure of the composites.     

Nonlinear multiscale modeling of polymer materials

In this study, a hyperelastic multiscale modeling technique is used to predict elastic properties of polycarbonate and polyimide polymer systems using a set of widely accepted atomistic force fields. The model incorporates molecular simulations and a nonlinear, continuum mechanics-based, constitutive formulation that incorporates the behavior of the polymer materials as predicted from molecular simulations. The predicted properties of the polymers using multiple force fields are compared to experimentally measured values. Both static and dynamic molecular simulations are performed using molecular mechanics energy minimizations and molecular dynamics simulation techniques, respectively. The results of this study indicate that static molecular simulation is a useful tool to predict the bulk-level nonlinear mechanical behavior of polymers for finite deformations. It is found that the AMBER force field yields the most accurate predicted mechanical and physical properties of the modeled polymer systems compared to the other force fields used in this study.     

Predictive nonlinear constitutive relations in polymers through loss history

A model is presented that calculates the highly nonlinear mechanical properties of polymers as a function of temperature, strain and strain rate from their molecular structure. The model is based upon the premise that mechanical properties are a direct consequence of energy stored and energy dissipated during deformation of a material. This premise is transformed into a consistent set of structure–property relations for the equation of state and the engineering constitutive relations in a polymer by quantifying energy storage and loss at the molecular level of interactions between characteristic groups of atoms in a polymer. The constitutive relations are formulated as a set of analytical equations that predict properties directly in terms of a small set of structural parameters that can be calculated directly and independently from the chemical composition and morphology of a polymer.     

材料高温力学性能理论表征方法研究进展

随着科学技术的迅猛发展,材料在高温领域的应用越来越广泛。然而高温下材料的力学性能和常温相比有很大差异,材料的高温力学性能研究和表征已成为当前的研究热点。论文文对材料在高温下力学行为理论表征方法研究的最新进展进行了总结和回顾。着重介绍了近年来高温陶瓷材料的断裂强度、金属材料的屈服强度、弹性模量与本构关系的温度相关性理论表征方法的研究进展。最后,总结已有研究工作的特点和不足之处,对材料高温力学性能理论表征方法的后续研究进行了展望,就进一步研究提供建议。     

Characterization of polymer dispersions by Fourier transform rheology

Fourier transform rheology is a very sensitive technique to characterize non-linear rheological fluid properties. It has been applied here for the first time to polymer dispersions in water and the results are compared to those from conventional rheology, namely steady and small amplitude oscillatory shear experiments. The investigated systems are mainly based on styrene and n-butylacrylate. A first attempt was made to evaluate how far colloidal parameters like particle volume fraction and ionic strength as well as chemical composition and surface characteristics of the dispersed particles are reflected in FT-rheology spectra. Significantly different non-linearities are observed for highly concentrated dispersions of particles with different T_g. These differences are not detected in linear oscillatory shear and show up in steady shear only at significantly higher shear rates. Particle surface characteristics influence the non-linear response in oscillatory shear significantly and the intensity of the overtones is found to be higher for a dispersion of particles with a “hairy” swollen surface layer as compared to a system of smooth particles, although the solids content was adjusted to match the steady shear viscosity. The intensity of the overtones in FT-rheology strongly decrease upon dilution. At a solid content below 35% no differences are observed in the FT-experiments for the systems investigated here, whereas the differences in steady shear are very pronounced in this concentration range. A significant influence of added salt onto the non-linear response is detected for some systems, which might be correlated to the stability of these systems. The observed phenomena certainly cannot be explained in terms of constitutive equations or microstructural statistical mechanical models at present. Thus, FT-rheology yields information complementary to classical steady or linear oscillatory shear experiments. Received: 11 December 2000 Accepted: 8 April 2001     

Dependence of nonlinear elasticity on filler size in composite polymer systems

Nanosized filler particles enhance the mechanical properties of polymer composites in a size-dependent fashion. This is puzzling, because classical elasticity is inherently scale-free, and models for the elasticity of composite systems never predict a filler-size dependence. Here, we study the industrially important system of silica-filled rubbers, together with a well-characterized model-filled crosslinked gel and show that at high filler content both the linear and nonlinear elastic properties of these systems exhibit a unique scaling proportional to the cube of the volume fraction divided by the particle size. This remarkable behavior makes it possible to predict the full mechanical response of particle-filled rubbers for small but finite deformations based solely on the rheology of the matrix and the size and modulus of the filler particles.     

Effects of the pH on the mechanical behavior of articular cartilage and corneal stroma

Electro-chemo-mechanical couplings in articular cartilages and corneal stroma are due to the presence of electric charges on proteoglycans. In addition, at non-physiological pH, collagen molecules become charged as well. Variation of the pH of the electrolyte has strong implications on the electric charge of these tissues, and by the same token, on their transport and mechanical properties. Indeed, articular cartilages and corneal stroma swell and shrink depending on the composition of the electrolyte, they are in contact with.Emphasis is laid here on the combined effects of pH, ionic strength, calcium and chloride binding on mechanical properties.The tissues are viewed as three-phase multi-species porous media. The constitutive framework is phrased in the theory of thermodynamics of deformable porous media. Acid–base reactions, as well as ion binding, are embedded in this framework. Although, macroscopic in nature, the approach accounts for a number of biochemical details defining collagen and proteoglycans.The model is used to simulate laboratory experiments where specimens of articular cartilages and corneal stroma are put in contact with a bath of controlled chemical composition. Chemical loadings, where the ionic composition and pH of the bath are varied, are intermingled with mechanical loadings. The variations of the stress and strain are observed to depend strongly on the ionic strength and ion type present in the bath: sodium chloride leads to a stiffer response than calcium chloride and hydrochloric acid. Moreover, when the bath changes from basic to acidic, the change of sign of the fixed charge across the isoelectric point has definite mechanical implications, and it gives rise to non-monotonous evolutions of the stress, strain and chemical content.While the chemo-mechanical effect is a key phenomenon that governs the behavior of tissues with fixed charges, the converse mechano-chemical effect is significant in corneal stroma due to its low stiffness.     

石墨烯的功能化改性及其作为水基润滑添加剂的应用进展

传统的油基润滑剂在使用过程中通常存在冷却性能差,易造成环境污染等问题,近年来绿色环保的水基润滑逐渐受到科学家们的关注. 水由于自身黏度低且易挥发等特点,其作为润滑剂时润滑效果不佳,因此亟待发展高效的水基润滑添加剂来改善其摩擦磨损性能. 在本文中,作者综述了近年来石墨烯基纳米材料的功能化改性及其作为水基润滑添加剂的最新研究进展,总结了其在摩擦过程中的润滑机理,并对目前石墨烯水基润滑添加剂存在的问题及今后重点研究内容进行了展望.      

Processing and characterization of epoxy/clay nanocomposites

Nanocomposite materials consisting of an epoxy matrix and silicate clay particles have been processed and characterized mechanically. The clay material used was a modified natural montmorillonite. The clay particles consisted of 1 nm thick layers with aspect ratios in the range of 100–1000. The clay particles were mixed with acetone and sonicated, then mixed with the polymer, deaerated and cured. The ultimate objective of processing was to produce a polymer/clay nanocomposite with separated (exfoliated) platelets, dispersed as uniformly as possible. Samples were prepared with clay concentrations of up to 10 wt%. The process used resulted in limited exfoliation but mostly intercalation, i.e., infusion of polymer between the silicate layers and increase of interlayer spacing. The characteristics of the nanocomposite were assessed by transmission electron microscopy and x-ray diffraction. Results from these observations show that the basal spacing of clay platelets increased from an initial pre-processing value of 1.85 nm to 4.5 nm. Enhancement of mechanical properties was measured by tensile testing of coupons. Stiffness increases of up to 50% over that of the unfilled epoxy were measured for clay concentrations of 5 wt%. Strength increases were also measured for low clay concentrations and low strain rate loading. Micromechanics modeling of mechanical behavior is discussed as a function of clay platelet dispersion.     

Characterization and Model of Piezoelectrochemical Energy Harvesting Using Lithium ion Batteries

Although lithium ion battery research often focuses on electrochemical properties, lithium ion intercalation materials are also mechanically active. Essentially, these materials exhibit a mechanical-electrochemical coupling such that when a stress is applied, the voltage of the battery increases. In this work, we develop a model to study and predict the effectiveness of intercalation materials as mechanical energy harvesters. Specifically, we show that a lithium ion battery harvester can be modelled as a simple circuit and that we can make both qualitative and quantitative predictions about the effectiveness of a battery material given its intrinsic mechanical and electrochemical properties. The measured efficiency of our system, calculated from the energy output and total work input, is 0.012 ± 0.004%, and our model predicts that the maximum theoretical efficiency of the system is 2.9 ± 0.5%. In the future, this model will help us develop and study other intercalation materials that will bring the measured efficiency closer to our proposed theoretical maximum.     

Polymer contribution to the thermal conductivity and viscosity in a dilute solution (Fraenkel Dumbbell model)

The phase-space kinetic theory for polymeric liquid mixtures is used to obtain an expression for the polymer contribution to the thermal conductivity of a nonflowing, dilute solution of polymers, where the polymer molecules are modeled as Fraenkel dumbbells. This theory takes into account three mechanisms for the energy transport: diffusion of kinetic energy (including the Öttinger-Petrillo term), diffusion of intramolecular energy, and the work done against the intramolecular forces. This paper is an extension of previous developments for the Hookean dumbbell model and the finitely-extensible dumbbell model. A comparison among the dumbbell results suggests that the thermal conductivity increases with chain stiffness. In addition, the zero-shear-rate viscosity and first normal-stress coefficient are also given for the Fraenkel dumbbell model.Dedicated to Prof. John D. Ferry on the occasion of his 85th birthday.     

Theoretical model of biomacromolecule through nanopore including effects of electrolyte and excluded volume

A theoretical model for the translocation process of biomacromolecule is developed based on the self-consistent field theory (SCFT), where the biomacromolecule is regarded as a self-avoiding polymer chain actuated by the external potential. In this theoretical model, the external potential, the Coulomb electrostatic potential of the charged ions (the electrolyte effect), and the attractive interaction between the polymer and the nanopore (the excluded volume effect) are all considered, which have effects on the free energy landscape and conformation entropy during the translocation stage. The result shows that the entropy barrier of the polymer in the solution with high valence electrolyte is much larger than that with low valence electrolyte under the same condition, leading to that the translocation time of the DNA molecules in the solution increases when the valence electrolyte increases. In addition, the attractive interaction between the polymer and the nanopore increases the free energy of the polymer, which means that the probability of the translocation through the nanopore increases. The average translocation time decreases when the excluded volume effect parameter increases. The electrolyte effect can prolong the average translocation time. The simulation results agree well with the available experimental results.     

镍掺杂白云母复合粉体的制备及其作为润滑脂添加剂的摩擦学性能

采用液相还原法制备了纳米镍掺杂白云母微粉(Muscovite,简记为Mu)的复合粉体Mu/Ni,表征了复合粉体的微观形貌、晶体结构和元素组成.利用环-块摩擦磨损试验机考察并比较了Mu/Ni和Mu作为锂基润滑脂添加剂的摩擦学性能,对磨损表面的粗糙度、二维和三维形貌以及元素组成进行了分析,探讨了Mu/Ni复合粉体的减摩抗磨机理.结果表明:复合粉体中纳米镍粒子均匀负载在白云母微粉表面,Mu/Ni和Mu作为添加剂均能有效提高锂基润滑脂的摩擦学性能,且Mu/Ni相比于Mu表现出更好的减摩抗磨性能,摩擦系数较锂基润滑脂降低了67.9%.Mu/Ni优良的摩擦学性能与白云母的层状结构及磨损表面生成的含有O、Fe、Si、Al和Ni等元素的润滑膜有关.