LiBOB as Conductive Salt or Additive for Li-Ion Batteries

Lithium hexafluorophosphate (LiPF6) is at present the most used electrolyte salt in Li-ion batteries. However, LiPF6 is known to be very sensitive to moisture, has a lower thermal stability in comparison to other salts and is quite toxic. Therefore many efforts have been focused on developing new salts to replace LiPF6. One of the most promising alternatives is lithium bis(oxalato)borate (LiBOB) [1,2]. LiBOB is a fluorine-free salt, its advantages towards LiPF6 being: low toxicity, very good thermal stability and the ability to take actively part in the formation of a stable SEI film at the carbon negative electrode, this improving the cycling stability of the cell. LiBOB allows the use of electrolyte solvents which otherwise cause co-intercalation and graphite exfoliation (i.e. PC) [3,4]. However, the use of LiBOB as electrolyte salt seems to be less compatible with some Cocontaining cathode materials used in Li-ion batteries e.g. LiCoO2. They were shown to generate more heat and to have less thermal stability in LiBOB when compared with LiPF6based electrolytes [5]. In such systems it is more rational to use LiBOB as an additive. The amount of additive in the electrolyte (about 5%) should be high enough to form a stable SEI film at the graphite anode and low enough not to have a negative impact on the thermal behaviour of the cathode material [6,7]. In this context, the present study investigated the potential use of LiBOB as both electrolyte salt and additive for Li-ion batteries, using different cathode and anode materials. The electrochemical characterization of different full cell configurations in both LiBOBand LiPF6-based electrolyte systems, as well as DSC/TG analysis of the electrode materials will be presented and discussed in the meeting. References