Haodong Chen

Comparison analysis on the thermal runaway of lithium-ion battery under two heating modes

The thermal stability evaluation of materials in a soft-pack commercial cell is tested using C80 calorimeter, including anode, cathode, separator and full cell (mixing of the three materials including additional electrolyte). Thermal runaway characteristic of the commercial cell is tested on the accelerating rate calorimeter (ARC) with two heating modes, including internal heating mode and external heating mode. The results show that the thermal stability of internal material for tested cell follows the below order: anode<separator<cathode. The voltage drop is influenced by the consumption of cathode and separator, while the effect of anode consumption on the voltage can be negligible. Both onset temperature and critical temperature in external heating mode are larger than that in internal heating mode. Thermal runaway induced by high temperature of the tested cell can be divided into three stages: 1) the cell can work under normal mode and all the internal exothermal reaction can be ignorable, 2) the exothermal of anode which can be detected and the thermal runaway can be stopped by effective heat dissipation, and 3) the cathode reaction and separator melting which cause the cell voltage drop and thermal runaway of the cell is inevitable in this stage.

Experimental Investigation on Glass Cracking for Wind Load Combined with Radiant Heating

The glass curtain wall is widely used in high-rise buildings; however, the glass breakage behavior is not well understood, which cannot satisfy the fire prevention requirements. The breakage behavior of glass panel under the combined effects of heating and wind was performed in this work. A total of 21 specimens were tested under five kinds of wind velocity from 0.0 m/s, 2.0 m/s, 5.0 m/s, 8.0 m/s, 11.0 m/s to 13.3 m/s. The maximum temperature difference on the glass surface is between the unshaded area on the exposed surface and the shaded area on the ambient side of the glass. With the speed of the wind which acted on the ambient side of the heated glass increasing, the maximum temperature difference on the glass surface when crack initiation decreases.

Comparative Study on Crack Initiation and Propagation of Glass under Thermal Loading

This paper explores the fracture process based on finite element simulation. Both probabilistic and deterministic methods are employed to model crack initiation, and several commonly used criteria are utilized to predict crack growth. It is concluded that the criteria of maximum tensile stress, maximum normal stress, and maximum Mises stress, as well as the Coulomb-Mohr criterion are able to predict the initiation of the first crack. The mixed-mode criteria based on the stress intensity factor (SIF), energy release rate, and the maximum principal stress, as well as the SIF-based maximum circumferential stress criterion are suitable to predict the crack propagation.

An optimal multistage charge strategy for commercial lithium ion batteries

Herein, an optimal multistage charge strategy for commercial lithium ion batteries is proposed to enhance the performance of electric vehicles and hybrid electric vehicles. The strategy includes four stages of constant current charge and short constant voltage (CV) charge time. Equivalent circuit model (ECM) and capacity fade analysis are used to search for optimal charge profiles. The results indicate that the parameters of ECM change with SOC and over battery lifetime. The charge time simulation based on ECM is still accurate enough to obtain fast charging after hundreds of cycles. The charge capacity depends on the final stage charge rate and CV charge time. The maximum temperature during charging and the temperature at the end of charging, which are related to the first and fourth stage charge rates, respectively, have different effects on the capacity fading. The influence of the maximum temperature on the capacity fading changes over the battery lifetime, which may be because the capacity fading mechanisms of the battery change over the battery lifetime. Thus, the charge profiles should be suitable at different periods. CV charging prolongs the cycle life when its time is suitable value. Considering all the results and practicality, optimal values of charge can be acquired to obtain fast charging, less charge capacity loss and long cycle life.

An Experimental and Theoretical Study of Optimized Selection and Model Reconstruction for Ammonium Nitrate Pyrolysis

Ammonium nitrate (AN) is a commonly-used industrial raw material in industrial explosives and fertilizers areas. However, as an energetic material, its danger exists during the production, transportation, and storage, resulting in a large number of accidents involving personal injury and property loss. To obtain the accurate kinetic triplet parameters of AN thermal decomposition, a series of thermogravimetry analysis (TGA) experiments was conducted with four different heating rates. Activation energies were calculated by different isoconversional methods Then the kinetic triplet of AN pyrolysis was optimized using a combination of experimental and simulant methods. Combined with the traditional model-free and model-fitting approaches, the experimental kinetic model for AN pyrolysis was optimized and then reconstructed. Through the pyrolysis reaction of AN, a reliable methodology for processing TGA data of hazardous material is proposed in the paper, and the kinetic parameters can be accurately obtained by using such a kinetics method.