Abstract
Much attention has been paid to rechargeable lithium-sulfur batteries (Li–SBs) due to their high theoretical specific capacity, high theoretical energy density, and affordable cost. However, their rapid c fading capacity has been one of the key defects in their commercialization. It is believed that sulfuric cathode degradation is driven mainly by passivation of the cathode surface by Li2S at discharge, polysulfide shuttle (reducing the amount of active sulfur at the cathode, passivation of anode surface), and volume changes in the sulfuric cathode. These degradation mechanisms are significant during cycling, and the polysulfide shuttle is strongly present during storage at a high state-of-charge (SOC). Thus, storage at 50% SOC is used to evaluate the effect of the remaining degradation processes on the cell’s performance. In this work, unlike most of the other previous observations that were performed at small-scale cells (coin cells), 3.4 Ah pouch Li–SBs were tested using cycling and calendar aging protocols, and their performance indicators were analyzed. As expected, the fade capacity of the cycling aging cells was greater than that of the calendar aging cells. Additionally, the measurements for the calendar aging cells indicate that, contrary to the expectation of stopping the solubility of long-chain polysulfides and not attending the shuttle effect, these phenomena occur continuously under open-circuit conditions.
Highlights
Recent trends in the energy sector strive towards high-density energy storages
Many of the previous observations were performed at small-scale cells, while in this study, we investigated the degradation mechanisms of larger format lithium-sulfur batteries (Li–SBs) pouch cells
The charge capacity, after an initial dip, increases gradually over the first 61 days, and it plateaus as the charging period becomes prolonged due to the strong presence of polysulfide shuttle, preventing the cells from reaching the cutoff voltage limits; instead, the charging is limited by time
Summary
Recent trends in the energy sector strive towards high-density energy storages. Among electrochemical energy storage options, lithium-sulfur batteries (Li–SBs) are an appropriate option, which meet this requirement. This shows connections between individual causes and the degradation mechanisms they lead to, resulting in the deterioration of Li–SB In this list, the items indicated by solid lines include the proven items in the literature, and the dashed lines are based on the results of the analysis of lithium-ion batteries, and the validation of these items must be investigated and are yet to be proven [9,23,24,25,26,27,28,29,30]. The calendar case showed a linearly increasing trend, while for cycling, the trend first rapidly grew, followed by a decrease, which further underlines the complexity of Li–SBs
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