Mechanism and Solution for the Capacity Fading of Li/FeS₂Battery

Development of Li/FeS 2 rechargeable batteries has been hampered by their short cycle life. In this paper, we start with the fundamental chemistry of FeS 2 in a non-aqueous liquid electrolyte to analyze the capacity fading mechanism of Li/FeS 2 batteries and propose three facile strategies for stabilizing capacity. It is repeatedly observed that the capacity fading of Li/FeS 2 cells follows a general mode consisting of a fast fading stage as Region 1, a slow fading stage as Region 2, and an accelerated fading stage as Region 3. We found that Region 1 is mainly attributed to the dissolution of lithium polysulfide leading to the loss of sulfur active material, and that Region 3 is mainly associated with the poor morphology of Li deposition resulting in the localized electric circuit shortening. The powder-like, small and loose Li particles not only react with electrolyte solvents drying-out the cell but also penetrate across the separator shortening the cell. Based on the above finding, the cycle life of Li/FeS 2 cells was improved by adding vinylene carbonate as the electrolyte additive, increasing mechanical pressure between two electrodes, and placing a carbon interlayer between the FeS 2 cathode and separator, respectively.