Analysis of Degradation Mechanism of Lithium Iron Phosphate Battery

Abstract

The degradation mechanisms of lithium iron phosphate battery have been analyzed with 150 day calendar capacity loss tests and 3,000 cycle capacity loss tests to identify the operation method to maximize the battery life for electric vehicles. Both test results indicated that capacity loss increased under higher temperature and SOC conditions. And also, large increase of internal resistance on the high temperature and high SOC conditions was confirmed by AC impedance tests. The real cycle capacity loss characteristic was derived by subtracting the capacity decrease due to calendar capacity loss during the cycle test from the overall capacity loss characteristic obtained from the cycle test. As a result, it is found that the real capacity loss contains not only structural disorders of electrode but also degradation factors due to the chemical reactions. Characteristics of degradation were quantified with equations based on the chemical kinetics. With this degradation prediction, an operation method was proposed that is compatible with the long life of batteries and the safety driving of a vehicle. As a result, with optimizing the SOC range used in the operation as follows: 30-10% in the warm seasons, 45-25% in the cold seasons, it was found that batteries can last 4 times longer than it used with high SOC range in every season.

Analysis of Novel Energy-Efficient Converters to Ensure the Required Quality of Electrical Energy

“…This is another converter, which is the source of the pulsation component, but opposite in phase present in the output signal of the rectifier. It is connected to the output circuit of the rectifier through a matching transformer with a small number of secondary winding turns, from one, which improves its weight and dimensions compared to the choke [44][45][46][47][48][49][50][51][52][53][54]. A single-phase inverter of the H-bridge type is used as a converter.…”

E-Mobility in Europe

“…Research shows that cycling Li ion batteries at differing temperatures causes varying levels of irreversible battery capacity loss (Kaneko et al 2013). The effect of temperature on cycle life of Li ion cells is shown in Fig.…”

Challenges in data‐based degradation models for lithium‐ion batteries

“…Arrhenius‐based correlations are also proven to represent capacity loss during calendar aging for other cell chemistries . For instance, Kaneko et al performed a set of accelerated calendar tests on 6.2‐Ah lithium iron phosphate (LFP) cells, and they fitted the capacity loss using an Arrhenius‐based correlation, where a capacity loss coefficient is correlated with the time term with an exponent equals to 0.5. Similarly, Redondo‐Iglesias et al developed an empirical approach for estimating capacity loss during calendar aging based on a linear approximation of the Eyring equation, which has the same mathematical form as the Arrhenius equation.…”