None of the battery chemistry would be possible without the component of electrolyte and additive, which is responsible for the formation of Solid Electrolyte Interface (SEI), the interface between the electrodes and the electrolyte. Studies have showed that EC would be reduced at ~ 0.7 V vs Li/Li⁺, and the reduction of EC forms SEI consisting of organic polymer, inorganic salts that serves as a filter for lithium ion conducting. The typical electrolyte consists of 1.0 to 1. 2 M of a lithium salt (such as LiPF₆ or lithium bis(trifluoromethylsulfonyl)imide, LiTFSI) in mixed solvents of carbonates type. For example, the current prevalent electrolyte Gen 2 consists of 1.2 M LiPF6 in 30 wt % of ethylene carbonate (EC) and 70 wt % of ethyl methyl carbonate (EMC). Another vital role of the additive is to mitigate unavoidable electrolyte decomposition occurred both at anode and cathodes side during the charge/discharge process. Apparently, the quality of the SEI significantly affects the battery performance.

We are reporting a series of new additives for lithium ion batteries, and the ability of the additives to mitigate the presence of HF in the electrolyte was probed by solution-state nuclear magnetic resonance (NMR) spectroscopy. A galvanostatic charge/discharge protocol cycled between 3.0-4.4V at 30°C with periodic hybrid pulse power characterization (HPPC) tests gave electrochemical information from which capacity and impedance data were derived. Investigation of the harvested electrodes using X-ray photoelectron spectroscopy (XPS) after being cycled shed light on surface films formed and transition metal dissolution.