*2.1. Materials*

Bis(trifluoromethane)sulfonimide lithium salt (Li-TFSI) (99%) and 1-ethyl-3-methylimidazolium bromide (EMI-Br) (99.98%) were purchased from Io-li-tech, Tuscaloosa, AL, USA. Ethylene carbonate (EC) (99%) and dimethyl carbonate (DMC) were purchased from Alpha Aesar (Tewksbury, MA, USA) and Fisher Scientific (Lenexa, KS, USA), respectively. LiTFSI (98%), HPLC water, silicon oxide, dichloromethane (DCM) (99%), and succinonitrile (SN, 99%) were obtained from Sigma-Aldrich (St. Louis, MO, USA)). Polyacrylonitrile (PAN) with *M*w ≈ 150,000 was purchased from Sigma-Aldrich. Dimethylformamide (DMF) (>99.5%), and tin (II) 2-ethylhexaonate were purchased from Fisher Scientific.
