Overdischarge-induced evolution of Cu dendrites and degradation of mechanical properties in lithium-ion batteries

The degradation of mechanical properties of overdischarge battery materials manifests as a significant effect on the energy density,safety,and cycle life of the batteries.However,establishing the correlation between depth of overdischarge and mechanical properties is still a significant challenge.Studying the correlation between depth of overdischarge and mechanical properties is of great significance to improving the energy density and the ability to resist abuse of the batteries.In this paper,the mechanical properties of the battery materials during the whole process of overdischarge from discharge to complete failure were studied.The effects of depth of overdischarge on the elastic modulus and hardness of the cathode of the battery,the tensile strength and the thermal shrinkage rate of the separator,and the performance of binder were investigated.The precipitation of Cu dendrites on the separator and cathode after dissolution of anode copper foil is a key factor affecting the performance of battery materials.The Cu dendrites attached to the cathode penetrate the separator,causing irreversible damage to the coating and base film of the separator,which leads to a sharp decline in the tensile strength,thermal shrinkage rate and other properties of the separator.In addition,the Cu dendrites wrapping the cathode active particles reduce the adhesion of the active particles binder.Meanwhile,the active particles are damaged,resulting in a significant decrease in the elastic modulus and hardness of the cathode.

Effect of organophilic group of coupling agent on the electrical performance of Boron Nitride/meta-aramid composite paper

Organophilic groups of coupling agents can be the key factor for the electrical performance of Boron Nitride(BN)/meta-aramid composite paper.In this article,four types of triethoxy-silane coupling agents with different organophilic groups,including mercaptopropyl(MP),glycidylether-propyl(GP),amino-propyl(AP)and trideca-fluoro-octyl(TFO)were studied.The structural and electrical properties of modified papers were compared,and the molecular simulation was conducted to reveal the interface interaction of modified BN and aramid.The results show that AP,GP and MP follow the same mechanism,improving the electrical performance by modifying the interface stability and paper structure,and the ranks of improving effects are AP,MP and GP.While,TFO mainly relies on the fluorine components to implement the electrical reinforcement,which compensates for the shortcoming in the paper structure.By choosing TFO and filler content of 15 wt%,the optimal breakdown strength of the paper can be increased to 28.17 kV/mm,1.8 times that of the paper doped with the hydroxylated BN.

Modified Coffin-Manson equation to predict the fatigue life of structural materials subjected to mechanical-thermal coupling non-coaxial loading

With regard to the structures subjected to severe mechanical-thermal coupling fatigue conditions,the consistency between service conditions and loading conditions was the prerequisite for the fatigue prop-erties test and fatigue life prediction.A miniature piezoelectric-driven instrument integrating with a tripodal piezoelectric actuator and envelope-type heating function was developed to investigate the mechanical-thermal coupling fatigue properties and obtain the fatigue life of materials under approximate service conditions.A physical model was described to quantitatively calculate the alternating deformation under the mechanical-thermal coupling tensile-bending combined condition.Accordingly,a fatigue life prediction method based on the Coffin-Manson equation under tensile-bending combined loading was proposed to estimate the mechanical-thermal coupling fatigue life in terms of the total coupling defor-mation and plastic strain amplitude.The feasibility of the proposed instrument was verified through the analysis of displacement responses of high entropy alloy specimens under the thermal-mechanical cou-pling tensile-bending combined condition at temperatures ranging from RT to 600°C.The comparison between fatigue lives directly measured through thermal-mechanical coupling experiments and theoreti-cally predicted fatigue lives indicated the availability of the modified Coffin-Manson equation.

Estimation of inverse Compton peak frequency for 4FGL Blazars

This study uses a parabolic equation to fit the Inverse Compton (IC) spectral component of 3743 blazars (794 FSRQs,1432 BLLacs,and 1517 BCUs) from the 4FGL-DR3 catalog.Some mutual correlations are investigated,and a Bayesian classification is performed to the IC peak frequencies.Our analyses draw the following conclusions:(1) The Bayesian classification shows two components with a dividing boundary of log(v_(p)^(IC)/Hz)pIC=22.9.Therefore,the 3743 blazars are divided into low IC peak frequency(LCP) blazars and high IC peak frequency (HCP) blazars.(2) A strong linear correlation exists between IC peak frequency(logv_(p)^(IC)) and γ-ray photon spectral index (Γ).The IC peak frequency can be estimated by an empirical relation logv_(p)^(IC)=–4.5·Γ+32.8 for BL Lacs and logv_(p)^(IC)=4.0+31.4pICfor FSRQs,which is consistent with the result by Abdo et al.(3) The ICspectral curvature and IC peak frequency are not as closely related as the synchrotron curvature and the synchrotron peak frequency.(4) An anti-correlation exists between IC peak frequency and IC peak luminosity,implying that as the IC peak frequency in the γ-ray band decreases,the source becomes more luminous.The beaming effect is stronger for the source with a lower IC peak frequency.(5) Positive correlations exist between IC and synchrotron components for both peak frequencies and peak fluxes,but no clear correlation exists between IC curvature and synchrotron curvature.

新生儿Mowat-Wilson综合征1例

Mowat-Wilson综合征是一种由ZEB2基因变异导致的罕见常染色体显性遗传病, 以特殊面容、多发先天畸形、生长发育迟缓为主要表现。本文报道1例新生儿Mowat-Wilson综合征, 以提高临床医生对该病的认识。

Study on operation voltage monitoring and electrothermal coupling simulation of electric multiple unit(EMU)roof arrester

The roof arrester of electric multiple units(EMU)can efficiently limit the overvoltage,and ensure the safe operation of the EMU electrical equipment.In the process of high‐speed operation,the traction power supply system is often affected by overvoltage.In addition,roof arrester explosion accidents occasionally occur.In this paper,the on‐line voltage measurement system of the EMU arrester is developed.By analysing a large number of voltage waveforms,the abnormal voltage is divided into three categories:over‐phase voltage,high harmonic voltage and steep impulse overvoltage.The charac-teristics of abnormal voltage waveforms are then summarised.The electrothermal coupling simulation model of the arrester is developed,and the current response and temperature distribution of the arrester under abnormal voltage are calculated.The impact of the impulse voltage energy on the arrester temperature is studied by applying a triangular wave voltage to the model.Finally,some suggestions are proposed for the operation and maintenance of the roof arrester.