Nonflammable Solvents and Additives

With regard to nonflammable solvents, we focus on organic phosphates, phospha-zenes, and other additives for safety improvement. 

In 1990, Mitsubishi Chemical Corporation discovered solvents with unusually high flash point, such as triesters of phosphoric acid (triethyl phosphate (66) and others) as well as other esters of phosphoric acid (15 vol.% and above) [140], This triggered prolific research on phosphate solvents. 

According to a paper by Wang et al. from the Japan Aerospace Exploration Agency (JAXA) published in 2006, TMP exhibits excellent anode stability but poor cathode stability against a graphite anode [141]. For this reason, they note the following The poor cathodic stability of the TMP solvent has led some authors to conclude that the goal of a TMP-based nonflammable electrolyte is impractical for lithium-ion cells [141], 

In 1992, Bridgestone discovered that cyclic phosphazenes, such as hexapropi-oxycyclotriphosphazene (146) and hexafuluoroethoxycyclotriphosphazene (147), can be used as additives [ 142]. 

In 1994, Tadiran, an Israeli company, made the discovery described as follows This cell comprises as main components a negative electrode which is Lithium or Lithium alloy, a positive cathode which includes MnOa and an electrolyte which is 1,3-Dioxolane (148) with Lithium hexafluoroarsenate (LiAsFe) and a polymerization inhibitor [143]. 

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Following the increase in battery capacity, the safety of LIBs is becoming an increasingly important topic. Compounds for safety improvement presented in this section are grouped into (1) additives for overcharge prevention [3, 111-138], (2) nonflammable solvents and additives [139-141], and (3) others [142-146]. 

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