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Decouple charge transfer reactions in the Li-ion battery

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Journal of Energy Chemistry 2024年第5期92卷 759-798页

作者： Yuxuan Bai Qiu-An Huang kai wu Jiujun Zhang Institute for Sustainable Energy/College of Sciences Shanghai UniversityShanghai 200444China Ningde Contemporary Innovation Laboratory Contemporary Amperex Technology Co.LimitedNingde 352100FujianChina

In the development of Li-ion batteries(LIBs)with high energy/power density,long cycle-life,fast charging,and high safety,an insight into charge transfer reactions is required.Although electrochemical impedance spectroscopy(EIS)is regarded as a powerful diagnosis tool,it is not a direct but an indirect measurement.With respect to this,some critical questions need to be answered:(i)why EIS can reflect the kinetics of charge transfer reactions;(ii)what the inherent logical relationship between impedance models under different physical scenes is;(iii)how charge transfer reactions compete with each other at multiple scales.This work aims at answering these questions via developing a theory framework so as to mitigate the blindness and uncertainty in unveiling charge transfer reactions in LIBs.To systematically answer the above questions,this article is organized into a three-in-one(review,tutorial,and research)type and the following contributions are made:(i)a brief review is given for impedance model development of the LIBs over the past half century;(ii)an open source code toolbox is developed based on the unified impedance model;(iii)the competive mechanisms of charge transfer reactions are unveiled based on the developed EIS-Toolbox@LIB.This work not only clarifies theoretical fundamentals,but also provides an easy-to-use open source code for EIS-Toolbox@LIB to optimize fast charge/discharge,mitigate cycle aging,and improve energy/power density.

关键词： Electrochemical impedance spectroscopy Unified impedance model Charge transfer reactions Solid/electrolyte diffusion Porous electrode EIS-Toolbox@LIB

Hybrid bonding of GaAs and Si wafers at low temperature by Ar plasma activation

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Journal of Semiconductors 2024年第4期45卷 69-75页

作者： Rui Huang Zhiyong Wang kai wu Hao Xu Qing Wang Yecai Guo School of Electronic and Information Engineering Wuxi UniversityWuxi 214105China Institute of Advanced Technology on Semiconductor Optics&Electronics Institute of Laser EngineeringBeijing University of TechnologyBeijing 100124China

High-quality bonding of 4-inch GaAs and Si is achieved using plasma-activated bonding technology.The influence of Ar plasma activation on surface morphology is discussed.When the annealing temperature is 300℃,the bonding strength reaches a maximum of 6.2 MPa.In addition,a thermal stress model for GaAs/Si wafers is established based on finite element analysis to obtain the distribution of equivalent stress and deformation variables at different temperatures.The shape varia-tion of the wafer is directly proportional to the annealing temperature.At an annealing temperature of 400℃,the maximum protrusion of 4 inches GaAs/Si wafers is 3.6 mm.The interface of GaAs/Si wafers is observed to be dense and defect-free using a transmission electron microscope.The characterization of interface elements by X-ray energy dispersion spectroscopy indi-cates that the elements at the interface undergo mutual diffusion,which is beneficial for improving the bonding strength of the interface.There is an amorphous transition layer with a thickness of about 5 nm at the bonding interface.The preparation of Si-based GaAs heterojunctions can enrich the types of materials required for the development of integrated circuits,improve the performance of materials and devices,and promote the development of microelectronics technology.

关键词： plasma-activated bonding bonding strength thermal stress model mutual diffusion

Stress relaxation properties of calcium silicate hydrate:a molecular dynamics study

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2024年第2期25卷 97-115页

作者： Zhicheng GENG Shengwen TANG Yang WANG Hubao A Zhen HE kai wu Lei WANG State Key Laboratory of Water Resources Engineering and Management Wuhan UniversityWuhan430072China Key Laboratory of Advanced Civil Engineering Materials of Ministry of Education School of Materials Science and EngineeringTongji UniversityShanghai200092China College of Materials Science and Engineering Xi’an University of Architecture and TechnologyXi’an710055China

The time-dependent viscoelastic response of cement-based materials to applied deformation is far from fully understood at the atomic level.Calcium silicate hydrate(C-S-H),the main hydration product of Portland cement,is responsible for the viscoelastic mechanism of cement-based materials.In this study,a molecular model of C-S-H was developed to explain the stress relaxation characteristics of C-S-H at different initial deformation states,Ca/Si ratios,temperatures,and water contents,which cannot be accessed experimentally.The stress relaxation of C-S-H occurs regardless of whether it is subjected to initial shear,tensile,or compressive deformation,and shows a heterogeneous characteristic.Water plays a crucial role in the stress relaxation process.A large Ca/Si ratio and high temperature reduce the cohesion between the calcium-silicate layer and the interlayer region,and the viscosity of the interlayer region,thereby accelerating the stress relaxation of C-S-H.The effect of the hydrogen bond network and the morphology of C-S-H on the evolution of the stress relaxation characteristics of C-S-H at different water contents was elucidated by nonaffine mean squared displacement.Our results shed light on the stress relaxation characteristics of C-S-H from a microscopic perspective,bridging the gap between the microscopic phenomena and the underlying atomic-level mechanisms.

关键词： Calcium silicate hydrate(C-S-H) Stress relaxation Ca/Si ratio Temperature Water content Atomic simulation

Incombustible solid polymer electrolytes:A critical review and perspective

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Journal of Energy Chemistry 2024年第6期93卷 264-281,I0007页

作者： kai wu Jin Tan Zhenfang Liu Chenguang Bao Ao Li Qi Liu Baohua Li College of Materials Science and Engineering Hunan UniversityChangsha 413000HunanChina Tsinghua Shenzhen International Graduate School Tsinghua UniversityShenzhen 055GuangdongChina

Since the advent of the solid-state batteries,employing solid polymer electrolytes(SPEs)to replace routine flammable liquid electrolytes is regarded to be one of the most promising solutions in pursing highenergy-density battery systems.SPEs with superior thermal stability,good processability,and high mechanical modulus obtain increasing attentions.However,SPE-based batteries are not impenetrable due to their decomposition and combustibility under extreme conditions.Researchers believe incorporating appropriate flame-retardant additives/solvents/fragments into SPEs can intrinsically reduce their flammability to solve the battery safety issues.In this review,the recent research progress of incombustible SPEs,with special emphasis on flame-retardant structural design,is summarized.Specifically,a brief introduction of flame-retardant mechanism,evaluation index for safety of SPEs,and a detailed overview of the latest advances on diverse-types SPEs in various battery systems are highlighted.The deep insight into thermal ru naway process,the free-standing incombustible GPEs,and the ratio nal design of pouch cell structures may be the main directions to motivate revolutionary next-generation for safety batteries.

关键词： Non-flammable electrolyte Solid polymer electrolyte High safety electrolyte Solid state electrolyte Solid state battery

Dynamics of an impurity ion transport in oil-paper insulation under various electric fields

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High Voltage 2024年第1期9卷 66-80页

作者： Yuanyang Ren Yang Wang Qiankai Zhang Jiayu Xiong Wen Cao Zepeng Lv kai wu State Key Laboratory of Electrical Insulation and Power Equipment Xi'an Jiaotong UniversityXi'anChina School of Electronics and Information Xi'an Polytechnic UniversityXi'anChina State Grid Sichuan Electric Power Research Institute ChengduChina

The ionic transport process is an important counterpart to charge transport in oil-paper insulation,and it significantly impacts oil flow electrification at the oil-paper interface.Despite this,the dynamics of this phenomenon and the underlying mechanisms remain unclear,particularly at the molecular level.To understand this fundamental aspect,we conduct Molecular Dynamics study on the transport behaviour of an impurity ion in different oil-paper insulation models under various external electric fields.Different influence factors,such as external electric fields,temperatures,and local structural characteristics,are investigated in relation to the corresponding ionic mobility in different polymer models.According to the simulations,ionic mobility and its response to electric fields are higher in weaker electrostatic models.As a result,mineral oil exhibits the highest ionic mobility and the most substantial enhancement of ionic mobility by external electric fields,followed by vegetable oil,oil-paper blends,and insulating paper.This significant deviation in ionic mobility between oil and paper leads to the formation of an electric double layer near the oil-paper interface.The underlying physical mechanisms of different ionic mobility and its response to the electric field in different polymer models could be explained by the different polymer structural influences in terms of interaction energy and coordination numbers in a static manner,as well as by the interactions between the impurity ion and its surrounding atoms in terms of lifetime correlation functions and velocity autocorrelation functions in a dynamic manner.In addition,the influence of temperature on ionic mobility in mineral and vegetable oil is examined,and their activation energies are calculated.Advancing in the fundamental understanding of the dynamics of the ion transport process in oil-paper insulation is vital to improving their insulating properties for oil-impregnated power transformers.

关键词： insulation transport fields

Exploring Trade-offs in Thermal Interface Materials:The Impact of Polymer-Filler Interfaces on Thermal Conductivity and Thixotropy

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Chinese Journal of Polymer Science 2024年第7期42卷 916-925,I0006页

作者： Bin Zhang Zheng-Li Dou Yong-Zheng Zhang Qiang Fu kai wu College of Polymer Science and Engineering State Key Laboratory of Polymer Materials EngineeringSichuan UniversityChengdu610065China

Effective thermal transport across solid-solid interfaces which is essential in thermal interface materials(TIMs),necessitates both optimal thixotropy and high thermal conductivity.The role of filler surface modification,a fundamental aspect of TIM fabrication,in the influence of these properties is not fully understood.This study employs the use of a silane coupling agent(SCA)to modify alumina,integrating experimental approaches with molecular dynamics simulations,to elucidate the interface effects on thixotropy and thermal conductivity in polydimethylsiloxane(PDMS)-based TIMs.Our findings reveal that the variations of SCAs modify both interface binding energy and transition layer thickness.The interface binding energy restricts macromolecular segmental relaxation near the interface,hindering desirable thixotropy and bond line thickness.On the contrary,the thickness of the transition layer at the interface positively influences thermal conductivity,facilitating the transport of phonons between the polymer and filler.Consequently,selecting an optimal SCA allows a balance between traditionally conflicting goals of high thermal conductivity and minimal bond line thickness,achieving an impressively low interface thermal resistance of just 2.45-4.29 K·mm^(2)·W^(-1)at275.8 kPa.

关键词： Thermal interface material Surface modification Thermal conductivity Thixotropy Interface thermal resistance

A Calculation Method of Double Strength Reduction for Layered Slope Based on the Reduction of Water Content Intensity

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工程与科学中的计算机建模(英文) 2024年第1期138卷 221-243页

作者： Feng Shen Yang Zhao Bingyi Li kai wu School of Civil Engineering Suzhou University of Science and TechnologySuzhou215011China R&D Department Suzhou Jcon Greenbuild Fabricated Co.Ltd.Suzhou215004China

The calculation of the factor of safety(FOS)is an important means of slope evaluation.This paper proposed an improved double strength reductionmethod(DRM)to analyze the safety of layered slopes.The physical properties of different soil layers of the slopes are different,so the single coefficient strength reduction method(SRM)is not enough to reflect the actual critical state of the slopes.Considering that the water content of the soil in the natural state is the main factor for the strength of the soil,the attenuation law of shear strength of clayey soil changing with water content is fitted.This paper also establishes the functional relationship between different reduction coefficients.Then,a USDFLD subroutine is programmed using the secondary development function of finite element software.Controlling the relationship between field variables and calculation time realizes double strength reduction applicable to the layered slope.Finally,by comparing the calculation results of different examples,it is proved that the stress and displacement distribution of the critical slope state obtained by the improved method is more realistic,and the calculated safety factor is more reliable.The newly proposedmethod considers the difference of intensity attenuation between different soil layers under natural conditions and avoids the disadvantage of the strength reduction method with uniform parameters,which provides a new idea and method for stability analysis of layered and complex slopes.

关键词： Double strength reduction slopes stability water content factor of safety numerical methods

A Case Report on Treating Progressive Supranuclear Palsy with a Combination of Chinese and Western Medicine

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Journal of Clinical and Nursing Research 2024年第5期8卷 23-29页

作者： kai wu Yongjie Gong Shan Yang Yalan Yu First Clinical College Shaanxi University of Chinese MedicineXianyang 712000Shaanxi ProvinceChina Xi’an TCM Hospital of Encephalopathy Xi’an 710000Shaanxi ProvinceChina

A case of progressive supranuclear palsy in a 66-year-old woman is presented.The patient complained of“progressive stiffness of both lower limbs for five years,accompanied by choking and coughing for more than 1 year,”and was diagnosed with paralysis in traditional Chinese medicine(TCM),which was characterized by a deficiency of liver and kidney,and phlegm and blood stasis blocking the collaterals.Western medicine diagnosed it as progressive supranuclear palsy.The patient was diagnosed with“Parkinson’s disease”several times in the past and was given“polybasic hydrazide”and“amantadine hydrochloride tablets,”etc.The patient did not have significant symptomatic relief,so she sought further treatment with a combination of traditional Chinese and Western medicine.Based on the concept of deficiency and excess,this disease is categorized as a paralytic disease in Chinese medicine,and the onset of the disease is closely related to the deficiency of the body after a long period of illness,with wind,phlegm,blood stasis,and deficiency as the main pathogenetic mechanism.The treatment is based on the combination of disease and evidence,with traditional Chinese medicine and acupuncture as the main treatments,supplemented by intermediate-frequency pulsed electrical stimulation,transcranial repetitive magnetic stimulation,medicated canisters,wax therapy,traditional Chinese medicine guasha,and acupoint injections.Western medicine is based on symptomatic treatment,and the patient’s symptoms were relieved significantly after the combination of Chinese and Western medicine.

关键词： Progressive supranuclear palsy Paralytic disease Diagnosis and treatment Deficiency and excess Combination of Chinese and Western medicine

Discussion on Traditional Chinese Medicine Treatment of Liver-Depression-Spleen-Deficiency Type Insomnia Based on the State-Target Theory and the Regulation of Microbiome-Gut-Brain Axis

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Journal of Clinical and Nursing Research 2024年第5期8卷 39-46页

作者： kai wu Yongjie Gong Shan Yang Yalan Yu First Clinical College Shaanxi University of Traditional Chinese MedicineXianyang 712000Shaanxi ProvinceChina Xi’an TCM Hospital of Encephalopathy Xi’an 710000Shaanxi ProvinceChina

Insomnia has become an urgent clinical problem in modern society.Current research has found that the gut flora-gut-brain axis plays an important role in regulating insomnia.The state-target theory is a product of the combination of traditional Chinese medicine and modern molecular biology technology.This paper clarifies the correlation between the state-target theory,the intestinal flora-gut-brain axis,and liver-depression-spleen-deficiency insomnia.The use of traditional Chinese medicine to regulate the structure and abundance of intestinal flora was also explored,aiming to integrate traditional Chinese medicine with Western medicine for the prevention and treatment of liver-depression-spleen-deficiency insomnia.

关键词： State-target theory Microbiome-gut-brain axis Liver-depression and spleen deficiency Insomnia Traditional Chinese medicine