Exploring the thermal stability of lithium-ion cells via accelerating rate calorimetry:A review

Given the importance of lithium-ion cell safety,a comprehensive review on the thermal stability of lithium-ion cells investigated by accelerating rate calorimetry(ARC),is provided in the present work.The operating mechanism of ARC is discussed first,including the usage and the reaction kinetics.Besides that,the thermal stability of the cathode/anode materials at elevated temperatures is revealed by examining the impacts of some significant factors,i.e.,the lithium content,particle size,material density,lithium salt,solvent,additive,binder and initial heating temperature.A comparison of the common cathode materials indicates that the presence of Mn and polyanion could significantly enhance the thermal stability of cathode materials,while the doping of Al also helps to restrain the reactivity.Except for their high capacity,some alloy materials demonstrate more competitive safety than traditional carbon anode materials.Furthermore,the thermal behaviors of full cells under abusive conditions are reviewed here.Due to the sensitivity of ARC to the kinetic parameters,a reaction kinetic modeling can be built on the basis of ARC profiles,to predict the thermal behaviors of cell components and cells.Herein,a shortcircuit modeling is exampled.

Scalable synthesis of Na_(3)V_(2)(PO_(4))_(3)/C with high safety and ultrahigh-rate performance for sodium-ion batteries

NASICON-type Na_(3)V_(2)(PO_(4))_(3) is a promising electrode material for developing advanced sodium-ion batteries.Preparing Na_(3)V_(2)(PO_(4))_(3) with good performance by a cost-effective and large-scale method is significant for industrial applications.In this work,a porous Na_(3)V_(2)(PO_(4))_(3)/C cathode material with excellent electrochemical performance is successfully prepared by an agar-gel combined with freeze-drying method.The Na_(3)V_(2)(PO_(4))_(3)/C cathode displayed specific capacities of 113.4 mAh·g^(-1),107.0 mAh·g^(-1) and 87.1 mAh·g^(-1) at 0.1 C,1 C and 10 C,respectively.For the first time,the 500-mAh soft-packed symmetrical sodium-ion batteries based on Na_(3)V_(2)(PO_(4))_(3)/C electrodes are successfully fabricated.The 500-mAh symmetrical batteries exhibit outstanding low temperature performance with a capacity retention of 83%at 0℃ owing to the rapid sodium ion migration ability and structural stability of Na_(3)V_(2)(PO_(4))_(3)/C.Moreover,the thermal runaway features are revealed by accelerating rate calorimetry(ARC)test for the first time.Thermal stability and safety of the symmetrical batteries are demonstrated to be better than lithium-ion batteries and some reported sodium-ion batteries.Our work makes it clear that the soft-packed symmetrical sodium ion batteries based on Na_(3)V_(2)(PO_(4))_(3)/C have a prospect of practical application in high safety requirement fields.

Adiabatic Decomposition of Two Kinds of Organic Peroxides by Accelerating Rate Calorimeter

The accelerating rate calorimeter was applied to study the thermal hazard of two kinds of organic peroxides, i.e. methyl ethyl ketone peroxide (MEKPO) and benzoyl peroxide (BPO). And their thermal decomposition characteristics were discussed. Meanwhile, thermal decomposition characteristics of MEKPO and BPO vvere compared. The result indicated that MEKPO is more sensitive to thermal effect than BPO. While once the thermal decomposition takes place. BPO will be more hazardous than MEKPO due to its serious pressure effect. Thermal kinetic analysis of these two kinds of organic peroxides was also taken, and the kinetic parameters for them were calculated. The study of thermal decomposition of MEKPO solution with different initial concentrations indicated that, the lower concentration MEKPO solution is, the higher onset temperature will be. And with the addition of organic solvent, it becomes more difficult for MEKPO to reach a thermal decomposition. Therefore, its thermal hazard is reduced.

A comparative study on the reactivity of charged Ni-rich and Ni-poor positive electrodes with electrolyte at elevated temperatures using accelerating rate calorimetry

The reactivity between charged Li(Li_(0.115)Mn_(0.529)Ni_(0.339)Al_(0.017))O_(2)(Li-rich),single crystal Li(Ni_(0.8)Mn_(0.1)Co_(0.1))O_(2)(SC-NMC811),LiFePO_(4)(LFP) and LiMn_(0.8)Fe_(0.2)PO_(4)(LMFP) positive electrodes at different states of charge(SOCs) and traditional carbonate-based electrolyte at elevated temperatures is systematically studied using accelerating rate calorimetry(ARC).The results show that the SOC greatly affects the thermal stability of the Li-rich and SC-NMC811 when traditional carbonate-based electrolyte is used.Although an increase in the SOC increases the energy density of lithium-ion cells,it also increases the reactivity between charged Li-rich and SC-NMC811 samples with electrolyte at elevated temperatures.In comparison with SC-NMC811,the Li-rich samples are much more stable at elevated temperatures,and the latter have higher specific capacity.SC-NMC811 samples are less reactive than traditional polycrystalline NMC811.Both LFP and LMFP samples show excellent thermal stability at elevated temperatures.The substitution of Fe by Mn in the olivine series positive materials does not impact the reactivity with electrolyte.

Thermal stability assessment of anti-explosive ammonium nitrate

The explosivity experiment of anti-explosive ammonium nitrate (AEAN) shows that the explosive characteristic of AEAN is eliminated. The adiabatic decompositions of ammonium nitrate and AEAN were investigated with an accelerating rate calorimeter (ARC). The curves of thermal decomposition temperature and pressure versus time, self-heating rate and pressure versus temperature for two systems were obtained. The kinetic parameters such as apparent activation energy and pre-exponential factor were calculated. The safety of AEAN was analyzed. It was indicated that AEAN has a higher thermal stability than AN. At the same time, it can be shown that the elimination of its explosive characteristic is due to the improvement on the thermal stability of AEAN.

Studies on the flame propagation characteristic and thermal hazard of the premixed N2O/fuel mixtures

An experimental study was carried out to investigate the flame propagation and thermal hazard of the premixed N2O/fuel mixtures,including NH3,C3H8 and C2H4.The study provided the high speed video images and data about the flame locations,propagation patterns,overpressures and the quenching diameters during the course of combustion in different channels to elucidate the dynamics of various combustion processes.The onset decomposition temperature was determined using high-performance adiabatic calorimetry.It was shown that the order of the flame acceleration rate and thermal hazard was N2O/C2H4>N2O/C3H8>N2O/NH3.

Traffic dynamics of an on-ramp system with a cellular automaton model

This paper uses the cellular automaton model to study the dynamics of traffic flow around an on-ramp with an acceleration lane. It adopts a parameter, which can reflect different lane-changing behaviour, to represent the diversity of driving behaviour. The refined cellular automaton model is used to describe the lower acceleration rate of a vehicle. The phase diagram and the capacity of the on-ramp system are investigated. The simulation results show that in the single cell model, the capacity of the on-ramp system will stay at the highest flow of a one lane system when the driver is moderate and careful; it will be reduced when the driver is aggressive. In the refined cellular automaton model, the capacity is always reduced even when the driver is careful. It proposes that the capacity drop of the on-ramp system is caused by aggressive lane-changing behaviour and lower acceleration rate.

The acceleration degradation processes of different aged refuses with the forced aeration for landfill reclamation

Forced aeration is one of the promising ways to accelerate landfill reclamation,and understanding the relation between aeration rates and waste properties is the prerequisite to implementing forced aeration under the target of energy saving and carbon reduction.In this work,landfill reclamation processes with forced aeration were simulated using aged refuses(ARs)of 1,4,7,10,and 13 disposal years,and the potential of field application was also investigated based on a field project,to identify the degradation rate of organic components,the O_(2)consumption efficiency and their correlations to microbes.It was found that the removal rate of organic matter declined from 20.3%(AR_(1))to 12.6%(AR_(13)),and that biodegradable matter(BDM)decreased from 5.2%to 2.4%at the set aeration rate of 0.12 L O_(2)/kg waste(Dry Matter,DM)/day.A linear relationship between the degradation rate constant(K)of BDM and disposal age(x)was established:K=−0.0002193x+0.0091(R^(2)=0.854),suggesting that BDM might be a suitable indicator to reflect the stabilization of ARs.The cellulose/lignin ratio decrease rate for AR1(18.3%)was much higher than that for AR13(3.1%),while the corresponding humic-acid/fulvic-acid ratio increased from 1.44 to 2.16.The dominant bacteria shifted from Corynebacterium(9.2%),Acinetobacter(6.6%),and Fermentimonas(6.5%),genes related to the decompose of biodegradable organics,to Stenotrophomonas(10.2%)and Clostridiales(3.7%),which were associated with humification.The aeration efficiencies of lab-scale tests were in the range of 5.4–11.8 g BDM/L O_(2)for ARs with disposal ages of 1–13 years,and in situ landfill reclamation,ARs with disposal ages of 10–18 years were around 1.9–8.8 g BDM/L O_(2),as the disposal age decreased.The increased discrepancy was observed in ARs at the lab-scale and field scale,indicating that the forced aeration rate should be adjusted based on ARs and the unit compartment combined,to reduce the operation cost.

Thermal hazard assessment of TKX-50-based melt-cast explosive

In the present study, thermal hazards of TNT and DNAN used as the molten binder in TKX-50-based meltcast explosives were comparatively studied through accelerating rate calorimeter(ARC) and Cook-off experiments. Two kinds of ARC operation modes were performed to investigate the thermal safety performance under adiabatic conditions(HWS mode) and constant heating(CHR mode). The obtained results demonstrated that at both heating modes, DNAN/TKX-50 outperformed TNT/TKX-50 from the thermal safety point of view. However, the sensitivity to heat of the samples was reverse because of the different heating modes. In addition, the results of thermal hazard assessment obtained from the cookoff experiment complied with ARC analysis which indicated the molten binder TNT replaced by DNAN would reduce the hazard of the TKX-50 melt cast explosive. Furthermore, the results of cook-off experiments also showed that DNAN/TKX-50 outperformed TNT/TKX-50 from the aspect of thermal stability, which was consistent with the result of CHR mode because of the similar heating process.

A model cathode for mechanistic study of organosulfide electrochemistry in Li-organosulfide batteries

Organosulfides offer new opportunities for high performance lithium-sulfur(Li-S)batteries because of materials abundance,versatile structures and unique properties.Yet,their redox kinetics as well as cycling performance need to be further improved.Employing redox mediators is a highly effective strategy to address above challenges.However,the underlying mechanism in this chemistry is so far insufficiently explored.Here,phenyl disulfide(Ph S–SPh)and phenyl diselenide(Ph Se–Se Ph)are used as a model system for mechanistic understanding of organosulfide electrochemistry,particularly the rate acceleration.Profiling the reaction thermodynamics and charge-discharge process reveals redox of both S–S and C–S bonds,as well as that the coupling between radical exchange and electrochemical redox is the key to enhance the sulfur kinetics.This study not only establishes a basic understanding of orgaonsulfide electrochemistry in Li-S batteries,but also points out a general strategy for enhancing the kinetics of sulfur electrodes in electrochemical devices.

Rate Acceleration of the Baylis-Hillman Reaction within Microreactors

Based on microreactors, the representative Baylis-Hillman reaction of cyclopent-2-enone coupled with 4-nitrobenzaldehyde in the presence of imidazole could be accelerated by manipulating the temperature and electric field. Furthermore, the electric field was used in promoting Baylis-Hillman reaction for the first time with the rate acceleration approximately 5.2-fold higher than that carried out in conventional vessels as well as 4.0-fold under control of temperature. Meanwhile, the products of Baylis-Hillman reaction at every time point could be collected and then determined by capillary micellar electrokinetic chromatography.

环丁砜凝胶化界面工程助力安全耐用的宽温域Li/LiCoO_(2)电池

高能量密度锂金属电池在电化学储能领域受到了广泛关注,但其存在热失控的风险.尤其在高温或热滥用等恶劣条件下,安全隐患更加凸显.研发本征热稳定、高安全电解质是该领域的一个主要挑战.在该工作中,我们提出了一种简单易操作的凝胶化策略,制备出独特的、高热稳定的环丁砜基凝胶电解质.采用耐高温环丁砜作为增塑剂,通过强偶极-偶极相互作用,实现了聚偏氟乙烯/聚环氧乙烷基质之间的凝胶化,并系统地研究了砜基凝胶对凝胶化过程、锂沉积/剥离和固态电解质界面的影响.由于良好的界面特性,砜基凝胶电解质显著提高了锂金属电池的长循环和安全性能.由凝胶电解质组装的Li/LiCoO_(2)电池,在高温(高达90℃)条件下仍然呈现出优异的循环稳定性.此外,通过加速量热仪证实了Li/LiCoO_(2)软包电池的高热安全性(>190℃).该研究工作为开发耐滥用、高比能和长寿命的高安全性锂金属电池提供了新方法.