Enhanced low temperature performance of LiFePO₄ cathode with electrolyte modification

Electrolyte conductivity and solid electrolyte interphase (SEI) film are two key factors that affect the low temperature performance of LiFePO₄ battery. In this work, the enhancement of conductivity is realized through optimizing the proportion of solvents by mass triangle model. SEI modification is achieved by adding film-forming agent of Li₂CO₃ in the high conductivity electrolyte of LiPF₆-EC/PC/EMC (0.14/0.18/0.68). For LiFePO₄ electrode, 51.5% of its room temperature capacity is delivered at-30^°C with the addition of 4% Li₂CO₃ in the electrolyte. As XPS measurement verified, the Li₂CO₃ precipitates on the electrode surface hinder electron transfer more efficiently and suppress electrolyte reaction further. Moreover, lithium ion migration within this phase is speeded up with the help of Li vacancies in Li₂CO₃.