Experimental and Numerical Study on Mechanical Deformation Characteristics of Lithium Iron Phosphate Pouch Battery Modules under Overcharge Conditions

Abstract

Lithium iron phosphate (LFP) pouch batteries are likely to swell under overcharge conditions, failing the module structure. An overcharge experiment was carried out on an LFP battery module composed of 72 LFP pouch cells. The experimental results show that the pouch LFP cell has a large deformation even at a low temperature (below ∼60 °C), and the deformation mainly occurs during the overcharge voltage plateau period. After overcharge, the average temperature increase of the module is 46 °C, and the overcharge voltage increases by 15 V. A novel gas swelling model, which is suitable for both pouch cells and prismatic cells, is proposed for the first time to realize the cell swelling caused by increased internal pressure. The interaction between cells is simulated under different working conditions, including a swelling cell contact with a normal cell (working condition I) and two swollen cells interact (working condition II). The simulation results show that the volume change offset can reach 277.6% under the internal pressure of 32434 Pa. The contact pressure is greater when both of the cells swell, causing an easily burst of the cell. In this paper, the initial contact in working condition II occurs when the SOC is 110% and the peak contact pressure is 28 N mm–2. The simulation and experimental results can provide numerical support for understanding the interaction mechanism between cells during overcharge.

Aging Mechanisms of Lithium-ion Batteries

“…Activated or released lattice oxygen can undergo reactions with alkyl carbonate electrolytes, producing additional gaseous byproducts such as CO 2 and CO (Fig. 8(a-e)) [141,153,154].…”

Gas Sensing Technology for the Detection and Early Warning of Battery Thermal Runaway: A Review

“…Inducing factors of battery thermal runaway can be summarized as follows: mechanical abuse (puncture, extrusion, and collision), electrochemical abuse (internal short circuit, overcharging, and overdischarging), and thermal abuse (local overheating and high ambient temperature). , As shown in Figure , there exists a certain relationship among these three abusing conditions, which can be ultimately developed to thermal abuse and consequently cause the thermal runaway of batteries: (1) Mechanical abuse will lead to battery deformation and then induce the occurrence of internal short circuit, that is, electrical abuse; (2) electrical abuse will release Joule heat and chemical reaction heat, further resulting in thermal abuse; (3) the temperature rise caused by thermal abuse will induce the thermal runaway chain reaction of a lithium-ion battery. In essence, battery thermal runaway is a positive feedback cycling process of energies.…”

How Gas Generates in Pouch Cells and Affects Consumer Products

“…Swollen pouch cell issues have been reported on various consumer electronics products such as phones and laptops, causing the device not to operate and the trackpad, screen, or outer cases of the devices to deform, pop open, or fracture (Puls Technologies Inc, 2019;Androidcentral, 2020). Sun et al (2021) showed that the contact pressure of the swollen cells with 278% volume increase on the surrounding components was up to 28 N/mm 2 . The swelling can compromise the waterproof or water-resistant level of the device (Dube, 2018).…”