Performance Improvement of Li Ion Battery with Non-Flammable TMP Mixed Electrolyte by Optimization of Lithium Salt Concentration and SEI Preformation Technique on Graphite Anode

Abstract

We fabricated a lithium ion battery with a non-flammable trimethyl phosphate (TMP) electrolyte, which has sufficient cycle properties (capacity retention was 97% at 50 cycles) and safety improvement due to the optimization of lithium salt concentration and a graphite anode with pre-formed solid electrolyte interphase (SEI). By dissolving highly concentrated LiPF6, i.e., above 2 M, into the TMP mixed electrolyte, lithium ion easily intercalated into the graphite anode. This was because the solvation number of TMP molecule to the lithium ion decreased. When a SEI film was formed using ethylene carbonate and diethyl carbonate solvents in advance without TMP, the decomposition of the non-carbonate solvent, such as TMP, was suppressed. Eventually, we found that a safe and high-performance lithium ion battery could be fabricated only with a combination of controlling the solvation number in the electrolyte and SEI pre-forming technology on the graphite anode