Lithium imide

Abstract: Lithium-conducting nanocomposite polymer electrolytes based on high molecular weight poly(oxyethylene) (POE) were prepared from high aspect ratio cellulosic whiskers and lithium imide LiTFSI salt. The thermomechanical behavior of the resulting films was investigated by differential scanning calorimetry, thermogravimetric analysis, and dynamic mechanical analysis. The ionic conductivity and the electrochemical stability of the nanocomposite polymer electrolytes are quite consistent with the specifications of lithium batteries. The ionic mobilities were determined by pulsed magnetic field gradient NMR, and it was shown that the reinforcement does not affect the lithium transference number. High performance nanocomposite electrolytes based on tunicin whiskers were obtained. Indeed, the filler provides a high reinforcing effect, while a high level of ionic conductivity is retained with respect to unfilled polymer electrolytes.

Abstract: Complexes of amorphous tetraglyme (G4) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) or lithium bis(perfluoroethyl-sulfonyl)imide (LiBETI) were prepared as pol(yethylene) oxide-type electrolytes. Addition of equimolar amounts of LiTFSI and tetraglyme results in a room temperature ionic liquid with the general formula [Li(G4)]TFSI. Differential scanning calorimetry analysis of [Li(G4)]TFSI reveals that it has a T g = -61°C, and the complex remains amorphous over a wide temperature range (-100 to 200°C), and has a very low vapor pressure for tetraglyme at room temperature. The corresponding BETI complex, [Li(G4)]BETI, crystallizes upon cooling and displays a T m = 31°C. Room temperature conductivities (25°C) of [LilG4)]TFSI and [Li(G4)]BETI were 1.13 and 0.63 mS/cm, respectively. Composite polymer electrolytes were prepared by addition of the complexes to polycations possessing TFSI or BETI anions. The composites afforded thin flexible membranes at polymer concentrations ≥50 mol % polymer with room temperature conductivities greater than 10 -4 S/cm. In general, increased concentrations of BETI anions in these materials resulted in increased mechanical stability but decreased ionic mobility. The complexes and composite polymer electrolytes displayed excellent anodic stability up to +4.5 V (vs. Li + /Li) and exhibited breakdown voltages ≥+5.5 V (vs. Li + /Li) on stainless steel electrodes.