Moreover, the reaction mechanism is assumed to follow either a ‘core–shell’ or ‘domino’ mechanism. Electronic (10 –7 to 10 –9 S cm −1) and ionic conductivity (10 –11 to 10 –20 m 2 s −1) values in the literature span over several magnitudes and are still under debate. Additionally, for the ionic conductivity, the diffusion is highly anisotropic, due to the olivine structure of the material with 1D transport. The main drawbacks of LFP are the low electronic and ionic conductivity. It was firstly introduced by Padhi et al.

The use of iron and phosphorus makes it a sustainable choice, since the materials are abundant and less toxic compared to Co, Ni and Mn. Li/Li +) and specific capacity of roughly 170 mAh g −1. It offers a relatively high working potential (3.5 V vs. LiFePO 4 (LFP) is a promising cell chemistry with potential to overcome all current drawbacks. However, even after roughly 30 years of development, many drawbacks still exist which limit the further utilisation and competitiveness. The focus is especially on lithium ion batteries, due to their relatively high energy density, low self-discharge, falling costs and scalability in battery packs. Graphic abstractĮnergy storage devices are receiving more and more attention due to the shift from fossil to renewable energy sources for the power grid and the electrification of the mobility sector. The results indicate that cycling at higher SOC ranges is more detrimental and low temperature cycling mainly affects the anode by the formation of plated Li. The cathodes aged at 55 ☌ exhibit micrometer size agglomerates of nanometer particles on the cathode surface. Using atomic force microscopy (AFM), the surface conductivity is examined, which shows only minor degradation for the cathodes aged at − 20 ☌. As expected, Fe dissolution from the cathode and deposition on the anode are observed for the ageing performed at 55 ☌, while Fe dissolution and deposition are not observed at − 20 ☌. The anode surface aged at 55 ☌ forms a dense cover on the graphite flakes, while at the anode surface aged at − 20 ☌ lithium plating and LiF crystals are observed. The results show that ageing at lower DOD results in higher capacity fading compared to higher DOD cycling.

Post-mortem analysis focuses on the structure of the electrodes using atomic force microscopy (AFM) and scanning electron microscopy (SEM) and the chemical composition changes using energy dispersive X-ray spectroscopy (SEM-EDX) and X-ray photoelectron spectroscopy (XPS).

The paper presents post-mortem analysis of commercial LiFePO 4 battery cells, which are aged at 55 ☌ and − 20 ☌ using dynamic current profiles and different depth of discharges (DOD).

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