Electrochemical Energy and Interfaces Laboratory, Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Hong Kong Special Administrative Region, China.
Nat Mater. 2020 Sep;19(9):1006-1011. doi: 10.1038/s41563-020-0667-y. Epub 2020 Apr 20.
Developing low-cost and eco-friendly aqueous electrolytes with a wide voltage window is critical to achieve safe, high-energy and sustainable Li-ion batteries. Emerging approaches using highly concentrated salts (21-55 m (mol kg)) create artificial solid-electrode interfaces and improve water stability; however, these approaches raise concerns about cost and toxicity. Molecular crowding is a common phenomenon in living cells where water activity is substantially suppressed by molecular crowding agents through altering the hydrogen-bonding structure. Here we demonstrate a 'molecular crowding' electrolyte using the water-miscible polymer poly(ethylene glycol) as the crowding agent to decrease water activity, thereby achieving a wide electrolyte operation window (3.2 V) with low salt concentration (2 m). Aqueous LiTiO/LiMnO full cells with stable specific energies between 75 and 110 W h kg were demonstrated over 300 cycles. Online electrochemical mass spectroscopy revealed that common side reactions in aqueous Li-ion batteries (hydrogen/oxygen evolution reactions) are virtually eliminated. This work provides a path for designing high-voltage aqueous electrolytes for low-cost and sustainable energy storage.
开发低成本、环保且具有宽电压窗口的水系电解液对于实现安全、高能量密度和可持续的锂离子电池至关重要。新兴的方法是使用高浓度盐（21-55m（molkg））来构建人工固-液界面并提高水的稳定性；然而，这些方法引发了人们对成本和毒性的担忧。分子拥挤是一种常见的现象，在活细胞中，水分子的氢键结构被分子拥挤剂改变，从而使水的活性显著降低。在这里，我们展示了一种“分子拥挤”电解液，使用水溶性聚合物聚乙二醇（PEG）作为拥挤剂来降低水的活性，从而在低盐浓度（2m）下实现了宽的电解液工作窗口（3.2V）。具有稳定比能量在 75-110Whkg 之间的 LiTiO/LiMnO 全电池在 300 次循环后仍保持稳定。在线电化学质谱揭示了水系锂离子电池中常见的副反应（析氢/析氧反应）几乎被消除。这项工作为设计低成本、可持续的储能用高压水系电解液提供了一种思路。
