FeS 2-Li 2S composite positive electrode material, consisted of mainly Li 3Fe 2S 4 and Li 2.33Fe 0.67S 2, was prepared for improving the cycle capability of FeS 2 in rechargeable lithium batteries with liquid electrolytes operated at ambient temperature. The electrochemical tests demonstrated that the FeS 2-Li 2S composite cells showed a relatively higher capacity retention after 15 cycles (ca. 64%) as compared with that of the FeS 2 cells (ca. 26%), though both sample cells showed comparable initial discharge capacities (ca. 740 and 790 mAh·g -1 (4.2 and 4.5 mAh·cm -2), respectively). The improved cycle capability of the FeS 2-Li 2S cells was ascribed particularly to rather unchanged discharge plateau at ca. 2.0 V, which was reported to correspond to the reduction of sulfur. The ex-situ S K-edge X-ray absorption fine structure measurements indicated that the redox reaction of sulfur ions (S 2 2- + 2e - 2S 2-), associated with Li extraction / insertion reactions, was still active after 15 cycles in the FeS 2-Li 2S electrode, while such redox reactions almost disappeared in the FeS 2 electrode. The atomic displacements required in the initial delithiation / lithiation were reduced in the FeS 2-Li 2S composite as compared with FeS 2, which would give rise to the suppression of the structural irreversibility in the following charge / discharge, resulting in the improved cycle capability.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry