The development and subsequent incorporation of flame retardant additives (FRAs) has become a priority for Li-Ion battery research and development. Triphenyl phosphate (TPP) was studied to ascertain the safety benefits and electrochemical performance when incorporated into a LiPF 6 /ethylene carbonate (EC)/ethyl methyl carbonate (EMC) electrolyte system. The flammability of electrolytes containing TPP was investigated via self-extinguishing time and flash point analysis. The electrochemical stability was studied by cyclic voltammetry (CV), battery cycling in graphite/LiNi 0.8 Co 0.2 O 2 cells, electrochemical impedance spectroscopy (EIS) and Tafel polarization. In order to better understand the role of TPP, ex-situ surface analysis of the cycled electrodes was conducted with X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Incorporation of TPP results in a moderate decrease in the flammability of the electrolyte with relatively minor detrimental effects on the performance of the cells and thus is a promising additive for lithium ion batteries.

Flame retarding co-solvents triphenyl phosphate (TPP) and dimethyl methylphosphonate (DMMP) were incorporated into a standard binary LiPF 6 /ethylene carbonate (EC)/Ethyl methyl carbonate (EMC) electrolyte with and without the anode solid electrolyte interface (SEI) film forming additive, lithium bis(oxalato)borate (LiBOB). Thin-film silicon/Li cells were cycled with the different electrolytes. The standard electrolyte has poor cycling performance losing ∼ 50% of the initial capacity during the first 50 cycles. Electrolytes containing TPP and DMMP show comparable cycling performance to the standard electrolyte. Incorporation of LiBOB into the standard electrolyte or the standard electrolyte containing flame retarding co-solvents results in improved cycling efficiency and capacity retention. Ex-situ analysis via X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) provides insight into the role of LiBOB in the improved cycling performance and SEI structure and composition.

The cycling performance of Si-nanoparticle/Li cells with different electrolytes has been investigated. Cells containing standard binary LiPF 6 /ethylene carbonate/ethyl methyl carbonate electrolytes have poor capacity retention (46 %) after 50 cycles. Cells cycled with fluoroethylene carbonate (FEC)-based electrolyte have much better capacity retention (74 %). The effect of incorporation of flame-retardant co-solvents triphenyl phosphate and dimethyl methylphosphonate was investigated with both the standard and FEC electrolytes. The incorporation of the FR co-solvents did not significantly alter the performance of either electrolyte. Ex situ analysis via scanning electron microscopy, attenuated total reflectance infrared spectroscopy, and X-ray photoelectron spectroscopy was conducted to gain a better understanding of the role of electrolyte in solid electrolyte interphase structure and stability.