Electrochemical characteristics of room temperature Li/FeS 2 batteries with natural pyrite cathode

Abstract

Electrochemical characteristics of Li/FeS 2 batteries having natural pyrite as cathode and liquid electrolytes have been studied at room temperature. The organic electrolytes used were 1 M lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) in tetra(ethylene glycol) dimethyl ether (TEGDME) or a mixture of TEGDME and 1,3-dioxolane (DOX), and 1 M LiPF 6 in a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC). The pyrite powder and FeS 2 cathode were characterized by SEM, EDS, XRD and charge/discharge cycling. The discharge capacities of Li/FeS 2 cells with 1 M LiTFSI dissolved in TEGDME were 772 mAh g −1 at the 1st cycle and 313 mAh g −1 at the 25th cycle at 0.1 C. The cycling performance could be improved by using a mixture of TEGDME and DOX as the electrolyte. It was found that TEGDME contributed to high initial discharge capacity, whereas, DOX contributed to better stabilization of the performance. The first discharge capacities of Li/FeS 2 cells showed a decreasing trend with higher current densities (615 and 534 mAh g −1, respectively, at 0.5 C and 1.0 C). Li/FeS 2 cells with the battery grade electrolyte 1 M LiPF 6 in EC/DMC had lower initial discharge capacity and cycling capability compared to the TEGDME system. The natural pyrite cathode with 1 M LiTFSI dissolved in a mixture of TEGDME and DOX showed reasonably good first discharge capacity and overall cycling performance, suitable for application in room temperature lithium batteries.