Current studies on the mechanical abuse of lithium-ion batteries usually focus on the mechanical damage process of batteries inside a jelly roll. In contrast, this paper investigates the internal short circuits inside batteries. Experimental results of voltage and temperature responses of lithium-ion batteries showed that battery internal short circuits evolve from a soft internal short circuit to a hard internal short circuit, as battery deformation continues. We utilized an improved coupled electrochemical-electric-thermal model to further analyze the battery thermal responses under different conditions of internal short circuit. Experimental and simulation results indicated that the state of charge of Li-ion batteries is a critical factor in determining the intensities of the soft short-circuit response and hard short-circuit response, especially when the resistance of the internal short circuit decreases to a substantially low level. Simulation results further revealed that the material properties of the short circuit object have a significant impact on the thermal responses and that an appropriate increase in the adhesion strength between the aluminum current collector and the positive electrode can improve battery safety under mechanical abusive conditions.

The response characteristics of the motor of an electric bus have many differences compared to those of traditional vehicle engines. During frequent acceleration and deceleration, the torque mutation has a severe impact on the transmission system because of the sensitive response characteristics of the electric bus motor. In this paper, an example of an electric city bus driven by a double motor coaxial series drive system is presented. To reduce the impact on the transmission system caused by motor torque mutation, a Model Predictive Control Algorithm for vibration suppression of an electric city bus is proposed. In order to deduce the state equation and output equation of the transmission system, the model of transmission system is simplified, and based on the Model Predictive Control method we describe the multi-objective problem as a weight objective function to obtain the model predictive control law to solve the optimization problem. In addition, we design a Transmission Control-Model Predictive Control controller to achieve vibration control based on Model Predictive Control within Vehicle Control Unit (VCU), and then improve the performance of the dynamic response of the transmission system. Finally, simulation and vehicle testing are used to verify the effect of the algorithm. The result shows that the torque control algorithm based on Model Predictive Control has a positive effect on suppressing vibration under certain weighting conditions.

Most literature on the mechanical properties of Lithium-ion battery cells is concerned with the mechanical behavior of jellyroll or Lithium-ion battery when the state of charge (SOC) is 0%. Recent evidence shows that the mechanical properties of Lithium-ion batteries change as the SOC value changes. In this study, several quasi-static mechanical tests on 18650 battery cells with various SOC values are performed to reveal the SOC-dependent mechanical and electrochemical failure behavior of Lithium-ion batteries. The SOC-dependent constitutive model of the jellyroll is proposed. Experimental results indicate that the ability of Lithium-ion batteries to resist deformation increase as the SOC value increases. An increase in the SOC value may facilitate thermal runaway after an internal short circuit. An explicit finite-element model of a Lithium-ion battery is established to validate the proposed approach. The simulation results of various loading cases are in good agreement with the corresponding experimental results. The established SOC-dependent finite-element model of a Lithium-ion battery may be beneficial to produce accurate simulations of an entire battery pack during operation.