Until today, the use of acetonitrile (AN) based electrolytes in lithium-ion batteries could only be enabled by using superconcentrated electrolyte mixtures with a lithium salt concentration of over 2 mol L-1, due to the poor reductive stability of AN against graphite. [1]
Here, the durability of electrolyte containing AN using low concentration of dual lithium salts was investigated by electrochemical measurements and optimized to achieve the desired battery performance derived from high ionic conductivity. [2]
We could prove that our AN containing electrolyte surpass the performance of a conventional carbonate-based electrolyte in LFP/graphite cells. The power and the durability in a wide temperature range from -40 °C to 85 °C is demonstrated, which exceed the operating range of conventional lithium-ion batteries.
The concentration of LiPF6 was successfully reduced in LFP/graphite cells using the AN containing electrolyte. In this study we were able to control the performance deterioration caused by HF, and therefore increase the longevity and the reliability of cells containing AN containing electrolyte, which is an important point when it comes to recycling.
This innovative electrolyte solutions are able to contribute directly to 48 V power supplies for mild hybrid vehicles and to 12 V batteries and can replace lead-acid batteries in the technology trend of automatic operation. Furthermore, it may also contribute to the popularization of cell-to-pack technology in the future, if it is possible to produce thicker electrodes whose thickness is exceeding the limit of current state-of-the-art electrode casting processes.
From the above results we suggest that it is possible to impart high durability in a wide temperature range to the developed AN containing electrolyte even if the concentration of lithium salts is within the same level as that of conventional carbonate-based electrolyte. Thus, these moderately concentrated AN containing electrolyte with high ionic conductivity for durability-oriented lithium-ion batteries will be possible to really pave the way for next-generation lithium-ion batteries towards a more sustainable environment.
[1] Y. Yamada, K. Furukawa, K. Sodeyama, K. Kikuchi, M. Yaegashi, Y. Tateyama, and A. Yamada, J. Am. Chem. Soc. 2014, 136, 5039–5046.
[2] N. Matsuoka, H. Kamine, Y. Natsume, and A. Yoshino, ChemElectroChem 2021, 8, 3095-3104.