Abstract
Polymer solid state electrolytes are actively sought for their potential application in energy storage devices, particularly lithium metal rechargeable batteries. Herein, we report a polymer with high concentration salts as a quasi-solid state electrolyte used for lithium-sulfur cells, which shows an ionic conductivity of 1.6 mS cm−1 at room temperature. The cycling performance of Li-S battery with this electrolyte shows a long cycle life (300 cycles) and high coulombic efficiency (>98%), without any consuming additives in the electrolyte. Moreover, it also shows a remarkably decreased self-discharge (only 0.2%) after storage for two weeks at room temperature. The reason can be attributed to that the electrolyte can suppress polysulfide anions diffusion, due to the high ratio oxygen atoms with negative charges which induce an electrical repulsion to the polysulfide anions, and their relatively long chains which can provide additional steric hindrance. Thus, the polysulfide anions can be located around carbon particles, which result in remarkably improved overall electrochemical performance, and also the electrolyte have a function of suppress the formation of lithium dendrites on the lithium anode surface.
Highlights
Conductivity at room temperature, and can dissolve lithium polysulfide at higher temperature
The results are supported by the lithium polysulfide diffusion and lithium metal stability experiments (Fig. 5)
Due to the effect of PIS electrolyte, it is difficult for the polysulfide diffuse to the lithium metal anode surface, and the perfect results were achieved with long cycling stability and high coulombic efficiency
Summary
Conductivity at room temperature, and can dissolve lithium polysulfide at higher temperature. Liquid electrolyte show a high ion conductivity but cause polysulfides diffusion issues, solid electrolyte can inhibit polysulfides diffusion but is hardly used at room temperature. We report a new polymer-in-salt electrolyte (the “PIS electrolyte”) as quasi-solid state electrolyte (QSSE) and its application in Li-S batteries. It is demonstrated that PIS electrolyte can prevent the diffusion of polysulfide anions by special polymer structures, which result in a perfect long cycle life and high coulombic efficiency. It shows a decreased self-discharge after two week storage
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