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Mathematical models for porous electrode impedance have been widely used in energy conversion and storage. They are also utilized for obtaining the physicochemical dynamics, resulting in theoretical understanding and prediction in practical energy devices. The existing mathematical models are limited in their explanations. This limitation can be attributed to the separate consideration of simple (planar electrodes) and complex (porous electrodes) systems and the complexity of parameter distribution with non-uniform processes. Here, to address these limitations, we propose a mathematical model based on a staircase structure that calculates the individual interfacial impedance at each step in the depth direction, which helps not only in describing complex and straightforward systems but also in uniform and non-uniform processes in the form of a simple, seamless general equation. Our study includes mathematical derivations, interpretations of porous electrode impedance, and validation of the experimental data.

To clarify the role of conducting carbon in porous electrodes for lithium-ion batteries on internal resistance, the dependence of internal resistance on the conductive carbon ratio in positive elec...

The decline of lithium-ion battery (LIB) performance at low temperatures, caused by the nonuniform occurrence of electrochemical reactions during cycling and the resulting irreversible capacity loss, significantly hinders further LIB commercialization. Herein, we report the first solution by analyzing the impedance using symmetric cells in the absence of charge-transfer reactions to obtain a parameter quantitatively describing ion transport in porous electrodes and thus modeling the effects of nonuniform reaction occurrence. The reciprocal of ionic resistance in porous electrodes (Rion-1) is found to be positively correlated with capacity retention during low-temperature cycling and is approximated as the product of maximum capacitance related to electric double-layer formation (Cdl,max) and the associated frequency (f0). Consequently, these ion-transport parameters can be used to predict capacity retention during low-temperature cycling, and the adopted approach therefore can help to mitigate low-temperature LIB performance degradation and thus contribute to the fabrication of next-generation rechargeable batteries.

Factors affecting the cycling life of cylindrical lithium-ion batteries of LiNi0.8Co0.15Al0.05O2 (NCA) with graphite were examined in terms of the rechargeable capacity and polarization of NCA derivatives of LizNi0.8Co0.15Al0.05O2−δ (0.8 ≤ z ≤ 1.05). NCA derivatives with rock-salt domains in the structure were prepared by a co-precipitation method and the structures of [Li1−yNiy]3(b)[Ni,Co,Al]3(a)O26(c) based on a space group of Rm were refined by a Rietveld method of the XRD patterns. The electrochemical reactivity of the NCA derivatives with rock-salt domains was examined in non-aqueous lithium cells, and it was found that the rechargeable capacities (Q) of the samples decrease linearly as the amount of rock-salt domain (y) increases. An empirical relation is obtained to be Q = 181.4 − 725.5y in which Q reaches zero at y = 0.25, which is derived from not only the capacity loss owing to inactive rock-salt domains but also the polarization increase. The galvanostatic intermittent titration technique (GITT) measurement told us that polarization of NCA derivatives increases when the amount of rock-salt domains is above 2%, i.e., y > 0.02, and such a relation is remarkable in the lithium insertion direction into the structure, which is ascribed to slow lithium ion mobility due to nickel ions in the lithium layers. The NCA derivatives with increased rock-salt domains of above 2% deteriorate rapidly in non-aqueous lithium cells upon charge and discharge cycles, which is ascribed to the cumulative increase in polarization during charge and discharge. An extended cycling test for cylindrical lithium-ion batteries of the NCA derivatives with a graphite negative electrode at elevated temperature was performed and the quantitative relation is discussed thereof.

Summary Optimization of the 3D battery architecture is crucial to improve the performance of microbatteries. However, such optimization is difficult and time consuming by hand for even experts. In this article, we propose a battery optimization system, which consists of an automatic geometry generator and performance simulators. The geometry generator creates feasible 3D batteries without using any human intuition and experience for the spatial arrangement of positive and negative electrodes. For quick evaluation of the internal resistance, which relates power and energy densities, we propose the transmission line model, the so-called 3D porous electrode model, as one of the performance simulators. To show the effectiveness of the optimization system, we designed the lithium-ion microbatteries. In the trade-off frontier for the internal resistance and the capacity, we successfully found a new battery architecture that has higher power and energy densities over the conventional interdigitated plates configuration., Graphical Abstract, Highlights • The automatic geometry generator created feasible 3D microbattery architectures • The use of TLM enabled quick evaluation of the internal resistance of the 3D battery • The optimization system could evaluate the performance of 200,000 3D microbatteries • The optimized battery showed better performance over the interdigitated geometry, Electrochemical Energy Storage; Energy Engineering; Energy Systems; Energy Materials

In this study, we develop methods for extracting reaction parameters (e.g., rate and enthalpy) from the differential scanning calorimetry (DSC) profiles of [battery component + electrolyte] systems to simulate the thermal abuse behavior of NCA-based batteries using a modification of a previously reported 3D thermal model. The obtained parameters and model are validated by comparison of simulated and experimental thermal abuse behaviors, and the validated model is employed to investigate the influence of heat generation due to SEI decomposition and regeneration in the anode. Moreover, the effect of Mg substitution on the thermal runaway temperature of NCA-based batteries is probed by simulating the thermal abuse behaviors of NCA and Mg-NCA batteries, and the relationship between the DSC-determined heat generation behavior of battery components and the simulated thermal abuse behavior of batteries is discussed in detail.

To understand the relationship between the specific energy and power of lithium (Li)-ion batteries, the dependence of the internal resistance of porous electrodes with high loading weight on thickness was systematically investigated. The ionic resistance in pores (Rion) and charge-transfer resistance for Li intercalation (Rct) normalized per unit electrode geometric area were assessed using a combination of electrochemical impedance spectroscopy with symmetric cells and the transmission line model for cylindrical pores. The changes of Rion and Rct and their magnitude show opposite trends with respect to electrode thickness. For thin electrodes, Rion is lower than Rct. The specific power decreases slightly as the electrodes become thicker because the total internal resistance is predominantly affected by the charge-transfer resistance, and there is no delay of the response in the depth direction. In contrast, for thick electrodes, Rion is higher than or approximately equal to Rct, so there is a delay of th...

Mg-substituted Li(Ni,Co,Al)O 2 have been prepared by a co-precipitation method and examined by XRD, neutron diffraction, X-ray absorption, magnetization and electrochemical measurements. Neutron diffraction measurement indicated that the Mg ions were mostly substituted for Ni ions located in transition metal layers in LiNi 0.75 Co 0.15 Al 0.05 Mg 0.05 O 2 . Although a tiny amount of Ni ions in lithium layers in LiNi 0.8 Co 0.15 Al 0.05 O 2 was detected by magnetization measurements, such Ni ions decreased by Mg-substitution. The Mg-substitution for Ni in LiNi 0.75 Co 0.15 Al 0.05 Mg 0.05 O 2 was also confirmed by X-ray absorption measurements. The 500 mAh-type cylindrical lithium-ion cells of LiNi 0.8-x Co 0.15 Al 0.05 Mg x O 2 (x = 0,0.05) with graphite negative-electrode were prepared and their battery performances were evaluated by cycling test at 2 C charge/discharge rate at 60 °C. A lithium-ion cell of LiNi 0.75 Co 0.15 Al 0.05 Mg 0.05 O 2 exhibited better capacity retention and smaller battery resistance than that of LiNi 0.8 Co 0.15 Al 0.05 O 2 after 500 cycles. Electrochemical impedance spectroscopy revealed that the Mg-substitution suppressed the increase in charge-transfer resistance upon cycling. The effects of Mg-substitution in LiNi 0.8 Co 0.15 Al 0.05 O 2 were discussed in terms of crystal structure and battery performance.

When the human head is loaded by the translational acceleration in the traffic crash accident, the human brain is damaged at the crash side and the counter side, such as the coup and the contre-coup brain injuries. The purpose of this study is to reveal a generation mechanism of the coup and contrecoup brain injuries and develop a prediction method of the brain injury at the nerve cell level by using the dynamic-explicit finite element method (FEM). We carried out a multi-scale crash simulation by using a macroscopic head model and a microscopic nerve cell model. We have investigated the hydrostatic pressure, the equivalent stress and strains distributions in the nerve cell during the head crash against the street plate. Numerical results show the availability of our multi-scale analysis to predict the brain injury at the macro and micro levels.

Hard coatings are frequently used to give plastics high scratch resistance. Coating hardness and adhesion to the substrate are considered to be key factors influencing scratch resistance, but it is difficult to produce coatings that have both properties. Hybridization of polymers and inorganic materials is a promising approach for solving this problem. We prepared polymer-silica hybrid coatings by using in situ polymerization to carry out radical polymerization of vinyl monomers in a sol-gel solution of alkoxysilanes, and measured the abrasion resistance of the coatings. However, the expected properties were not obtained because the sol-gel reaction did not perfectly proceed on the surface of the coatings under the N2 conditions. We found that curing the hybrid coatings by UV irradiation in air promoted the sol-gel reaction on the surface, resulting in coatings having excellent abrasion resistance.

The mechanism of the increasing of resistance of lithium-ion batteries using Li(Ni,Co)O2 based material as positive electrode materials was investigated. The increase in resistance of cells with Li(Ni,Co)O2 material and artificial graphite was observed in cycling test at 60 °C. It was found that the increasing of resistance was mainly attributed to that at positive electrode by ‘reconstructed method’. In order to examine the mechanism of the increasing of resistance of positive electrode, the morphological changes of positive particles and local structure of Li(Ni,Co)O2 material were investigated. The clearance and crack were observed at grain boundary inside particle after cycle by FIB (focused ion beam) technique. The change of local structure around Co-atom was observed during charge–discharge process at 60 °C by in situ XAFS (X-ray absorption fine structure spectroscopic) analysis method. It was considered that the morphological and local structural changes of positive material cause the increasing of resistance.

A method of predicting fatigue strengths using fracture mechanics on noched components of ferrous sintered materials is investigated. By applying Lukas's formula for evaluation of AK and a intrinsic crack model for small crack propagation on notched components, a simple formula for predicting fatigue limits was derived. This method requires three material properties: the fatigue limit of smooth specimen, the threshold stress intensity range for long crack, and the threshold value of the effective stress intensity. For experimental verification, a notched specimen for fatigue tests as sintered was designed, and fatigue tests were conducted with notched specimens of ferrous sintered materials with two different pore sizes. The predicted fatigue limits are comparatively in good agreement with the experimental results.

Bending fatigue tests were carried out to clarify the effects of thin hard coatings on the fatigue strength at a number of cycles for steels. Coatings of carbides and nitrides produced by thermoreactive deposition and diffusion, chemical vapour deposition and physical vapour deposition, processes and of electroplated chromium on various steels were tested as well as hardened steels. The results thus obtained revealed that the fatigue strength at a number of cycles highly depended on hardness and residual stress at the substrate surface as in the case of the endurance limit and that the existence of the coatings suppressed the cracking in the substrates to increase the fatigue strength after loading cycles. Effects of coating thickness, surface roughness, notch shape, and post-heat treatment were also examined.

A 60 year-old man with Wolff-Parkinson-White (WPW) syndrome was admitted to our hospital because of atrial fibrillation and heart failure. He had a history of paroxysmal atrial fibrillation which had increased in frequency as mitral stenosis progressed over a period of 10 years. Since heart rate-dependent torsades de pointes appeared after DC defibrillation due to class IA antiarrhythmic agents, the drug was withdrawn and an intravenous infusion of isoproterenol was started. Sinus rhythm was restored and maintained by restarting the administration of the class I A antiarrhythmic agent. Electrophysiological examination revealed a single accessory conduction pathway and no retrograde conduction, the effective refractory period was prolonged to 330 msec. After the heart failure had improved, mitral valve replacement and transection of the bundle of Kent were performed. Because of the possibility of grave hemodynamic derangement induced by marked tachycardia, surgical treatment should be seriously considered in patients with mitral stenosis when associated with WPW syndrome and atrial fibrillation, even in those not classified as high risk patients.

Hard coatings are frequently used to give plastics high scratch resistance. Coating hardness and adhesion to the substrate are considered to be key factors influencing scratch resistance, but it is difficult to produce coatings that have both properties. Hybridization of polymers and inorganic materials is a promising approach for solving this problem. We prepared polymer-silica hybrid coatings by using in situ polymerization to carry out radical polymerization of vinyl monomers in a sol-gel solution of alkoxysilanes, and measured the abrasion resistance of the coatings. However, the expected properties were not obtained because the sol-gel reaction did not perfectly proceed on the surface of the coatings under the N2 conditions. We found that curing the hybrid coatings by UV irradiation in air promoted the sol-gel reaction on the surface, resulting in coatings having excellent abrasion resistance.

I. Analysis by Electrochemical and Spectroscopic Examination Tsuyoshi Sasaki,* Takamasa Nonaka, Hideaki Oka, Chikaaki Okuda, Yuichi Itou, Yasuhito Kondo, Yoji Takeuchi, Yoshio Ukyo,* Kazuyoshi Tatsumi, and Shunsuke Muto* Toyota Central Research and Development Laboratories, Incorporated, Nagoakute 480-1192, Japan Department of Materials, Physics and Energy Engineering, Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan

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— An hermetic-sealing material for FEDs composed of thermosetting polyimide and glass fiber, has been developed. The main backbone and end-capping material of polyimide were investigated to satisfy both high Tg and high flowability. A thermosetting function, 4-phenylethynylphthalic anhydride (PEPA), was used as the end-capping material. The fracture of a rigid and softening structure was optimized in the main polymer structure. The obtained polyimide demonstrated both a high Tg (265°C) and low viscosity (98 Pa-sec at a sealing temperature of 350°C). In order to improve the gas permeability and the mechanical and thermal characteristics of the sealing material, a mixture of various types of ceramic fillers and polyimide has been investigated, and glass fiber was adopted. When 30 wt.% of glass fiber was combined when the developed polyimide, the Ar permeability and coefficient of thermal expansion of the sealing material decreased to below one-half of the base polyimide. This material enables us to seal at a temperature of about 350°C in nitrogen atmosphere and shows superior performance suitable for glass-to-glass sealing.

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A hermetic-sealing material for FED composed of thermosetting polyimide and inorganic filler has been developed. This material enables us to seal at a temperature around 350 °C in nitrogen atmosphere and shows superior performance suitable for glass-to-glass and glass-to-metal sealing.