Thermal runaway behavior and features of LiFePO ₄ /graphite aged batteries under overcharge

Abstract

In this paper, the overcharge tests of 25 Ah LiFePO 4 /graphite batteries are conducted in an open environment and the overcharge-to-thermal-runaway characteristics are studied. The effects of current rates (C-rates: 2C, 1C, 0.5C, and 0.3C) and states of health (SOHs: 100%, 80%, 70%, and 60%) on thermal runaway features are discussed in detail. The overcharge process can be summarized into five stages based on the experimental phenomena (C-rate ≥ 1 and SOH ≥ 80%): expansion, fast venting after safety valve rupture, slow venting, intense jet smoke, and explosion, while the battery cannot explode at lower Crates and SOHs. The maximum pressure increases with the increase in C-rate or SOH. There are five obvious inflection points in the voltage curve during overcharge process. The V 1 (point B) of aged battery, corresponding to lithium plating on the anode, changes little with C-rates. It is slightly lower than that of the new battery. A sharp drop in voltage (point E) is probably due to the internal short circuit (ISC), caused by the local melting and rupture of the separator. It takes more than 2 minutes from the moment of ISC to thermal runaway regardless of the SOH, indicating that there are a few minutes to take safety measures if the voltage is an indication parameter. The onset temperature of thermal runaway decreases first and then increases as the SOH decreases from 100% to 60% during 1C constant overcharge tests. These results can provide guidance for the thermal management of the whole battery life cycle and the reuse of retired batteries. K E Y W O R D Sageing, lithium-ion battery safety, overcharge, SOH, thermal runaway

Thermal runaway difference between fresh and retired lithium iron phosphate batteries under overheating

“…T1 -T3 are located on the same surface, and T4 is located in the center of the other largest surface of the battery. Four pressure sensors are used to record the overpressure generated by the battery explosion, and the pressure sensors are arranged at 150 mm in the horizontal direction and 150 mm in the vertical direction of the battery, which is the same as Literature [6].…”

“…About 0.5 s after the explosion, due to the deflagration, the pressure wave appeared at a second peak (about 46 kPa), which was lower than the first peak pressure. In the early stage, we also studied the pressure wave of the explosion and combustion of the battery under overcharge at 1C [6]. The results showed that the peak pressure of the explosion was also around 100 kPa, while the overpressure caused by the deflagration was around 150 kPa (higher than the explosion pressure wave), indicating that the combustion caused by overcharge (1C) is more intense than that caused by overheating (200 W).…”

“…However, all of the above is aimed at accelerated aging batteries, which are different from the aging conditions of LIBs in practical applications. For this reason, our research group [6] has carried out research on the overcharge-TR characteristics of retired automotive batteries in the early stage. The results showed that 70% of SOH batteries had a lower TR onset temperature.…”

A La and Nb co-doped BaTiO3 film with positive-temperature-coefficient of resistance for thermal protection of batteries

“…Aer the cells were fully charged ($100% SOC, stage II), the cathode was fully delithiated and no more Li-ions could be extracted, so the voltage of the battery increased until overcharge reactions initiated, at around 4.7 V, and the continuation of the overcharge reactions produced a voltage plateau of around 5.7 V. The behaviour of the batteries with and without the PTCR lm is similar in these two stages and it is also in good agreement with previous studies on overcharge tests of lithium-ion batteries. [70][71][72][73][74] In the following stage III of the overcharge process (Fig. 6a), the cells with and without the PTCR lm showed totally different overcharge behaviours.…”

Experimental and modeling analysis of thermal runaway for LiNi 0 . 5 Mn 0 . 3 Co 0 . 2 O Tang1, Wei2, Zhang3 et al. 2021Int J Energy Res8090View full textAdd to dashboardCite

“…Lithium‐ion batteries (LIBs) with relatively high power density, inherent high energy density, long cycle life, and eco‐friendly property are considered as a prospective power source for new energy vehicles (NEVs), especially for electric vehicles (EVs) 1‐4 . The energy density is the critical parameter inextricably linked to the driving range of EVs.…”