Single-Ion Conducting Polymer Electrolytes for High-Energy Lithium Batteries

Summary:

In order to broaden and strengthen the future application of lithium batteries, it is highly important to further increase their energy density without compromising their safety. In this regard, the use of metallic lithium as anode material is considered the next big step forward in battery research, but this requires the realization of electrolyte materials with a high electrochemical stability towards lithium, while simultaneously suppressing dendritic lithium deposition [1,2]. Research in this field is largely focusing on solid electrolyte materials nowadays, i.e., inorganic materials or polymers. For the latter, the achievement of suitable ionic conductivities at ambient temperature, however, is a severe issue, rendering them non-applicable for most electrochemical energy storage solutions. In addition, the use of polymer-based electrolytes is commonly limited to “low-voltage” cathode materials like LiFePO4 due to their limited electrochemical stability towards oxidation [3].
Recently, we have developed a new single-ion conducting multiblock copolymer electrolyte system with suitable ionic conductivities of at least 0.5 mS cm-1 at ambient temperature, long-term stable lithium stripping and plating and excellent stability towards LiNi0.6Mn0.2Co0.2O2 (NMC622) as well as LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes [4–6] thanks to the wide electrochemical stability window of up to 4.8 V. This is accompanied by a facile synthesis procedure including high yields and a very promising perspective towards upscaling of the reactions. While the membrane preparation follows a simple solvent casting process, followed by the introduction of highly mobile molecular transporters (e.g., ethylene carbonate (EC) or propylene carbonate (PC)), the self-standing properties of the membrane are maintained at any time. Presently, additional efforts are undertaken to further increase the ionic conductivity, for instance, by optimizing the molar ratio of the lithium-containing block and the mechanical stability providing block. The very recent advances promise further improvement of the already demonstrated excellent performance in the near future, thus, contributing to the development of high-energy solid-state lithium-metal batteries.

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[4] Nguyen H D, Kim G T, Shi J, Paillard E, Judeinstein P, Lyonnard S, Bresser D and Iojoiu C 2018 Nanostructured multi-block copolymer single-ion conductors for safer high-performance lithium batteries Energy Environ. Sci. 11 3298–309
[5] Chen Z, Steinle D, Nguyen H D, Kim J K, Mayer A, Shi J, Paillard E, Iojoiu C, Passerini S and Bresser D 2020 High-energy lithium batteries based on single-ion conducting polymer electrolytes and Li[Ni0.8Co0.1Mn0.1]O2 cathodes Nano Energy 77 105129
[6] Steinle D, Chen Z, Nguyen H D, Kuenzel M, Iojoiu C, Passerini S and Bresser D 2021 Single-ion conducting polymer electrolyte for Li||LiNi0.6Mn0.2Co0.2O2 batteries—impact of the anodic cutoff voltage and ambient temperature J. Solid State Electrochem., https://doi.org/10.1007/s10008-020-04895-6.