Open AccessThe Effect of LiFePO4 Particle Size and Surface Area on the Performance of LiFePO4/Graphite Cells
Author(s) -
Eric Logan,
Ahmed Eldesoky,
Yulong Liu,
Liu M,
Xiaoyong Yang,
Helena Hebecker,
Aidan Luscombe,
Michel B. Johnson,
J. R. Dahn
Publication year - 2022
Publication title -
journal of the electrochemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.258
H-Index - 271
eISSN - 1945-7111
pISSN - 0013-4651
DOI - 10.1149/1945-7111/ac6aed
Subject(s) - materials science , graphite , particle (ecology) , particle size , deposition (geology) , electrode , analytical chemistry (journal) , specific surface area , isothermal process , chemical engineering , composite material , chemistry , thermodynamics , chromatography , paleontology , biochemistry , oceanography , physics , sediment , engineering , biology , geology , catalysis
In an effort to better understand capacity loss mechanisms in LiFePO4 (LFP)/graphite cells, this work considers carbon-coated LFP materials with different surface area and particle size. Cycling tests at room temperature (20°C) and elevated temperatures show more severe capacity fade in cells with lower surface area LFP material. Measurements of Fe deposition on the negative electrode using micro X-ray fluorescence (µXRF) spectroscopy reveal more Fe on the graphite electrode from cells with low surface area. Measurements of parasitic heat flow using isothermal microcalorimetry show marginally higher parasitic heat flow in cells with low surface area. Cross-sectional scanning electron microscopy images of aged LFP electrodes show micro-fracture generation in large LFP particles, which are more prevalent in the low surface area material. Further, studies on the impact of vacuum drying procedures show that while Fe deposition can be inhibited by removing excess water contamination, the direct impact of Fe deposition on capacity fade is small. Particle fracture leads to the exposure of LFP fresh surface to the electrolyte, leading to more parasitic reactions and Li inventory loss.