Search

The effect of lithium salts such as LiPF6, LiBF4, LiCF3SO3 and LiN(CF3SO2)2 (LiTFSI) in tetra(ethylene glycol) dimethyl ether (TEGDME) electrolyte on the ionic conductivity, interfacial resistance and discharge properties of Li/pyrite cell at room temperature was studied. The electrolytes had good ionic conductivity at room temperature in the range 0.61 to 1.86 × 10-3 S/[removed info]. The discharge capacities of Li/pyrite cells with 1M LiPF6 and LiBF4 in TEGDME were lower compared to those of the other two non-HF containing salts. The best cycle performance was exhibited by LiTFSI in TEGDME electrolyte, with a discharge capacity of 438 mAhg-1 after 20 cycles, which is ~49% of FeS2 theoretical capacity (894 mAhg-1). The good performance of LiTFSI-TEGDME electrolyte resulted mainly from its low interfacial resistance in Li/FeS2 cells, which showed a decreasing trend with cycling.

Iron, sulfur and transition metal powders were used as the starting materials to prepare iron disulfide (FeS2) cathode material at room temperature by high energy mechanical alloying. Modified FeS2 were also prepared by incorporation of transition metals like Co and Ni. Li/FeS2 cells with the prepared iron disulfides as cathodes were studied for discharge properties at room temperature using the 0.5M LiTFSI in tetra(ethylene glycol) dimethyl ether (TEGDME). The first discharge capacities of Li/composite FeS2 cell with 5 wt.% Co and 3 wt.% Ni were 571 and 844 mAh/g, respectively, compared to 389 mAh/g for the cell without any additive. The enhanced properties resulted from the better electronic conductivity of the material containing the metallic additive. The initial capacity and cyclic performance were improved when nickel and cobalt were added to prepare the modified iron disulfide.

Polymer electrolyte (PE) based on poly(ethylene oxide)‐lithium bis(trifluoromethane sulfonyl)imide (PEO‐LiTFSI) was blended with three room temperature ionic liquids (RTILs), namely 1‐butyl‐3‐methylimidazolium bis(trifluoromethane sulfonyl)imide (BMITFSI), 1‐butyl‐3‐methylimidazolium tetrafluoroborate (BMIBF4) and 1‐butyl‐3‐methylimidazolium trifluoromethanesulfonate (BMICF3SO3) with a view to enhance the room temperature ionic conductivity to acceptable levels for use in lithium batteries. The incorporation of 80 parts by weight (pbw) of the RTILs in 100 pbw of PEO‐LiTFSI resulted in enhanced ionic conductivity, the effect being more pronounced at lower temperatures. Evaluation of electrochemical properties showed that PEs with RTILs exhibit an electrochemical stability window between −1.0 V and 4.5 V vsLi/Li+and good reversibility of redox reactions on cycling. The optimum results were obtained with the incorporation of BMITFSI in the PE, which exhibited a low and stable interfacial resistance on lithium metal.

An organic radical battery (ORB) operating at room temperature with lithium metal anode and radical polymer poly(2,2,6,6-tetramethylpiperidinyloxy-4-ylmethacrylate) (PTMA) cathode with a microporous polymer electrolyte based on electrospun poly(vinylidene fluoride-co-hexafluoropropylene) membrane has been demonstrated. The polymer electrolyte with a fully interconnected pore structure, high electrolyte uptake, and high ionic conductivity is found to be suitable for use in PTMA-based ORBs. The cell with a thin cathode of 17μmthickness incorporating 40wt%of PTMA exhibits a discharge capacity of 111mAh∕gat 1C-rate (0.1mA∕cm2)that corresponds to ∼100%theoretical capacity. Good rate capability is shown by the ORB; thus, a specific capacity of 98mAh∕gis delivered even at the very high 50C-rate. A stable cycle property is obtained at all C-rates, with the cathode structure remaining intact during cycling. The polymer electrolyte shows good compatibility with the electrodes and leads to a decrease of electrode/electrolyte interfacial resistance with cycling. The study indicates the suitability of microporous, polymer electrolyte-based ORB as a safe, lightweight, environmentally benign, flexible battery with high power-rate capability for varied applications.