Overcharge for Reviving Failed Li-O2 Batteries

Prolonging the lifetime of batteries is a long-term pursuit, and it is also one of the prerequisites for the practical application of batteries. However, this is really challenging for high-energy Li-O2 batteries due to their poor charge efficiency and cathode passivation induced by products accumulation. Here, we demonstrate that overcharging the Li-O2 batteries can facilitate the decomposition of residue products and thus revive the cathode, which allows further operation of Li-O2 batteries for 1316 cycles. This long lifetime not only makes full use of the Li anode, but also enables the battery recycling in a safer way. Furthermore, applying anode protection and overcharge together, the life of batteries can be extended to a record high value of 2714 cycles. This overcharge strategy simplifies the cathode regenerating procedures, realizing system-level efficient use of battery components and prolonging the life of Li-O2 batteries that can meet the requirements of practical applications.

Investigation on Cycling and Calendar Aging Processes of 3.4 Ah Lithium-Sulfur Pouch Cells

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.