3M HQ-115 (LiTFSI) Electrolyte Additive Dramatically Improves Battery Performance in Electrolytes Containing Trace Amounts of Water

Abstract

3M has successfully commercialized lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) (trade name: HQ-115) as an electrolyte additives in commercial lithium ion batteries. Based on our investigations and customer’s feedback, when used as an electrolyte additive, HQ-115 improves cycle life in Graphite/LiCoO2 cells at high temperature. Similar results are obtained in Graphite/MNC cells. Cycle life improvements achieved by adding HQ-115 correlates with reduced cell impedance. HQ-115 also reduces gassing at the negative electrode and can prevent shorting under high temperature float test conditions with single layer PE separator. Thus cell life and safety are improved using HQ-115 as additives in standard electrolyte.Recent studies by 3M, Dalhousie University, and Medtronic indicate that HQ-115 is a useful additive for maintaining acceptable cell performance under conditions where moisture levels in the electrolyte are elevated. It is interesting that the addition of HQ-115 to either VC+100 ppm water or VC+1000 ppm water cells reduced the cell swelling and impedance rise compared to identical cells without HQ-115, consistent with later long term cycling data at 55oC. Thus HQ-115 additive can enable relaxation of specifications on water in electrolyte. The results reported herein suggest that relaxing specifications on water content in electrolyte with added HQ-115 as additives may be one avenue for cost-reduction of Li-ion cells with graphite negative electrodes. In August 2013, 3M, Dalhousie University, and Medtronic jointly filed a global patent application to cover these new benefits of 3M’s HQ-115 electrolyte additives in lithium ion batteries.