Understanding the boundary and mechanism of gas-induced explosion for lithium-ion cells:Experimental and theoretical analysis

Thermal runaway(TR)of lithium-ion(Li-ion)batteries(LIBs)involves multiple forms of hazards,such as gas venting/jetting,fire,or even explosion.Explosion,as the most extreme case,is caused by the generated flammable gases,and a deflagration to detonation transition(DDT)may occur in this process.Here,overheat-to-TR tests and the corresponding outgas-induced explosion tests were conducted on 42 Ah Li-ion cells with Li[Ni_(1/3)Co_(1/3)Mn_(1/3)]O2cathode.The sum of CO_(2),H_(2),C_(2)H_(4),CO,and CH4accounted for more than 90%of the gases.Lower/upper explosion limits(LEL/UEL),laminar flame speed,and ideal stable detonation pressure were calculated to interpret the explosion characteristics and boundary.It turned out that shockwave was easily to be compressed and accelerated under higher state of charge(SOC)conditions.Thus,Li-ion cells explosion may evolve into unstable detonation in encapsulated battery pack and its evolution mechanism was explained,which provides a new idea for explosion-proof design of LIBs system.Additionally,a comprehensive assessment method was developed to intuitively characterize TR hazards.Severity of explosion presented an upward trend with the increase of SOC while the sensitivity was not the same.This study provides a further anatomy of TR,which is instructive to the safety of power battery systems.

Overcharge-to-thermal-runaway behavior and safety assessment of commercial lithium-ion cells with different cathode materials:A comparison study

In this paper,overcharge behaviors and thermal runaway(TR)features of large format lithium-ion(Liion)cells with different cathode materials(LiFePO4(LFP),Li[Ni_(1/3)Co_(1/3)Mn_(1/3)]O_(2)(NCM111),Li[Ni_(0.6)Co_(0.2)Mn_(0.2)]O_(2)(NCM622)and Li[Ni_(0.8)Co_(0.1)Mn_(0.1)]O_(2)(NCM811))were investigated.The results showed that,under the same overcharge condition,the TR of LFP Li-ion cell occurred earlier compared with the NCM Li-ion cells,indicating its poor overcharge tolerance and high TR risk.However,when TR occurred,LFP Li-ion cell exhibited lower maximum temperature and mild TR response.All NCM Liion cells caught fire or exploded during TR,while the LFP Li-ion cell only released a large amount of smoke without fire.According to the overcharge behaviors and TR features,a safety assessment score system was proposed to evaluate the safety of the cells.In short,NCM Li-ion cells have better performance in energy density and overcharge tolerance(or low TR risk),while LFP Li-ion cell showed less severe response to overcharging(or less TR hazards).For NCM Li-ion cells,as the ratio of nickel in cathode material increases,the thermal stability of the cathode materials becomes poorer,and the TR hazards increase.Such a comparison study on large format Li-ion cells with different cathode materials can provide deeper insights into the overcharge behaviors and TR features,and provide guidance for engineers to reasonably choose battery materials in automotive applications.

Geochronology and geochemistry of the five magmatic rocks in the Ningzhen region,China

The Ningzhen region of China is located in the easternmost part of the middle-lower Yangtze River Cu–Fe polymetallic metallogenic belt. From west to east, it comprises five main intermediate–acidic intrusive complexes: the Qilinmen, Anjishan, Xiashu–Gaozi, Shima, and Jianbi complexes. Geochemical investigations show that these five intrusive complexes exhibit high contents of SiO_2, at 64.74–73.40 wt%, Al_2O_3, at 14.15–17.37 wt%, and K_2O + Na_2O, at 6.49–8.68 wt%. The majority of the samples belong to the high-K calc-alkaline series, with a few samples plotting in the calc-alkaline and tholeiitic series. Trace element analysis shows that the samples are enriched in large ion lithophile elements(LILE) and are depleted in high field strength elements(HFSE).The chondrite-normalized rare earth element(REE) patterns are characterized by right-inclined curves, showing light rare earth element(LREE) enrichment. In addition,the(La/Yb)Nratios are high at 15.02–37.28, with an average of 29.13, and slightly negative or none Eu anomalies are present. In the(La/Yb)N–d Eu diagram, the samples plot within the crust-mantle type field. Laser ablation–inductively coupled plasma–mass spectrometry(LA–ICP–MS) zircon U–Pb dating yielded ages of122.0 ± 1.0 Ma, 106.1 ± 0.8 Ma, 108.7 ± 1.4 Ma,103.5 ± 1.9 Ma, and 96.8 ± 1.7 Ma for the Qilinmen,Anjishan, Xiashu–Gaozi, Shima, and Jianbi complexes,respectively. On the basis of this research and knowledge of several known metal deposits related to these complexes, we suggest that the Mesozoic large-scale diagenesis and metallogenesis in the Ningzhen region may have ceased at 100 Ma or about 95 Ma.

Explosion behavior investigation and safety assessment of large-format lithium-ion pouch cells

Large-format lithium-ion(Li-ion) batteries with high energy density for electric vehicles are prone to thermal runaway(or even explosion) under abusive conditions. In this study, overcharge induced explosion behaviors of large-format Li-ion pouch cells with Li[NiCoMn]Ocathode at different current rates(C-rates)(0.5C, 1C, 2C) were investigated. The explosion characteristics of the cells were elucidated by discussing the evolution of the cell voltage, the surface temperature and the shock wave pressure.Generally, the whole overcharge process could be divided into four stages according to the evolution of several key parameters and the overcharge behaviors;the overcharge C-rate has a great influence on cells’ thermal behaviors. The experimental results showed that the thermal runaway process of Liion cells caused by overcharging consisted of two kinds of explosions, physical explosion and chemical explosion. The existence of observable negative pressure zone in the pressure curves indicated that the Li-ion cells are not a self-supplying oxygen system during the explosion. Further, the explosion dynamics parameters were matched. An explosion TNT-equivalent conversion strategy that depended on the pressure of the shock wave was utilized to evaluate the released energy and its hazards. In addition, with respect to the overcharge of Li-ion pouch cells, a safety assessment method and a safety management method were proposed based on the explosion behaviors. From the perspective of battery safety, this study is of great significance for the safety design of Li-ion cells and can provide guidance for engineers to optimize the safety function of battery packs.

Leading-edge receptivity of boundary layer to three-dimensional free-stream turbulence

The laminar-turbulent transition has always been a hot topic of fluid mechanics. Receptivity is the initial stage and plays a crucial role in the entire transition process. The previous studies of receptivity focus on external disturbances such as sound waves and vortices in the free stream, whereas those on the leading-edge receptivity to the three-dimensional free-stream turbulence (FST), which is more general in the nature, are rarely reported. In consideration of this, this work is devoted to investigating the receptivity process of three-dimensional Tollmien-Schlichting (T-S) wave packets excited by the three-dimensional FST in a flat-plate boundary layer numerically. The relations between the leading-edge receptivity and the turbulence intensity are established, and the influence of the FST directions on the propagation directions and group velocities of the excited T-S wave packets is studied. Moreover, the leading-edge receptivity to the anisotropic FST is also studied. This parametric investigation can contribute to the prediction of laminar-turbulent transition.

PC-VINS-Mono: A Robust Mono Visual-Inertial Odometry with Photometric Calibration

Feature detection and Tracking, which heavily rely on the gray value information of images, is a very importance procedure for Visual-Inertial Odometry (VIO) and the tracking results significantly affect the accuracy of the estimation results and the robustness of VIO. In high contrast lighting condition environment, images captured by auto exposure camera shows frequently change with its exposure time. As a result, the gray value of the same feature in the image show vary from frame to frame, which poses large challenge to the feature detection and tracking procedure. Moreover, this problem further been aggravated by the nonlinear camera response function and lens attenuation. However, very few VIO methods take full advantage of photometric camera calibration and discuss the influence of photometric calibration to the VIO. In this paper, we proposed a robust monocular visual-inertial odometry, PC-VINS-Mono, which can be understood as an extension of the opens-source VIO pipeline, VINS-Mono, with the capability of photometric calibration. We evaluate the proposed algorithm with the public dataset. Experimental results show that, with photometric calibration, our algorithm achieves better performance comparing to the VINS-Mono.

Enhancing production of ergosterol in Pichia pastoris GS115 by over-expression of 3-hydroxy-3-methylglutaryl CoA reductase from Glycyrrhiza uralensis

The rate-limiting enzyme in the mevalonic acid(MVA)pathway which can lead to triterpenoid saponin glycyrrhizic acid(GA)is 3-hydroxy-3-methylglutaryl-CoA reductase(HMGR).In order to reveal the effect of copy number variation in the HMGR gene on the MVA pathway,the HMGR gene from Glycyrrhiza uralensis Fisch.(GuHMGR)was cloned and over-expressed in Pichia pastoris GS115.Six recombinant P.pastoris strains containing different copy numbers of the GuHMGR gene were obtained and the content of ergosterol was analyzed by HPLC.The results showed that all the recombinant P.pastoris strains contained more ergosterol than the negative control and the strains with 8 and 44 copies contained significantly more ergosterol than the other strains.However,as the copy number increased,the content of ergosterol showed an increasing–decreasing–increasing pattern.This study provides a rationale for increasing the content of GA through over-expressing the GuHMGR gene in cultivars of G.uralensis.

Genesis of Carlin-type gold deposits in southwestern Guizhou Province,China

A solution containing nanometer-sized pure gold particles was prepared with the hydrolysisreduction method. As observed under the electron microscope, the gold particles were as large as 2—20 nm in size. Different kinds of mineral and rock were put into the solution and the experimental result showed that the nanometer-sized gold particles are obviously adsorbed on sulfide minerals, native copper and carbonaceous rocks. This experimental result is consistent with the actual geological observation. On this basis a better explanation is presented of the genesis of the Carlin-type gold deposits.

China's battery electric vehicles lead the world:achievements in technology system architecture and technological breakthroughs

Developing new energy vehicles has been a worldwide consensus,and developing new energy vehicles characterized by pure electric drive has been China's national strategy.After more than 20 years of high-quality development of China's electric vehicles(EVs),a technological R&D layout of“Three Verticals and Three Horizontals”has been created,and technological advantages have been accumulated.As a result,China's new energy vehicle market has ranked first in the world since 2015.To systematically solve the key problems of battery electric vehicles(BEVs)such as“driving range anxiety,long battery charging time,and driving safety hazards”,China took the lead in putting forward a“system engineering-based technology system architecture for BEVs”and clarifying its connotation.This paper analyzes the research status and progress of the three core components of this architecture,namely,“BEV platform,charging/swapping station,and real-time operation monitoring platform”,and their key technological points.The three major demonstration projects of the 2008 Beijing Olympic Games,the 2022 Beijing Winter Olympics,and the intelligent and connected autonomous battery electric bus project are discussed to specify the applications of BEVs in China.The key research directions for upgrading BEV technologies remain to be further improving the vehicle-level all-climate environmental adaptability and all-day safety of BEVs,systematically solving the charging problem of BEVs and improving their application convenience,and safeguarding safety with early warning and implementing active/passive safety protection for the whole life cycle of power batteries on the basis of BEVs'operation big data.BEVs have acquired new technological features such as intelligent and networked technology empowerment,extensive integration of control-by-wire systems,a platform of chassis hardware,and modularization of functional software.