据《科学新闻》（Science News）2021年1月5日提供的消息，Zn-空气电池有很多用途。它们重量轻，结构紧凑，并且比其他电池使用更可持续，更不易燃的材料制成。但是它们通常是不可充电的。新的电池设计可能会改变这一点。通过调整构建材料，研究人员创建了锌-空气电池的原型，该电池可以充电数百次。相关研究结果于2021年1月1日在《科学》（Science）杂志描述了这种持久耐用的设备，有一天可以为电动汽车或其他电子设备供电。详见W. Sun et al. A rechargeable zinc-air battery based on zinc peroxide chemistry. Science. Vol. 371, January 1, 2021, p. 46. doi: 10.1126/science.abb9554.

锌-空气电池是许多潜在的下一代电池之一，它们可以容纳更多的能量，同时比现有设备便宜和更安全。每个锌-空气电池单元都包含两个电极-锌阳极和多孔阴极-被称为电解质的液体隔开。在标准的锌-空气电池中，电解质是一种高pH值物质，含有诸如氢氧化钾之类的成分。空气中的氧气进入阴极，在此气体与电解质中的水反应形成氢氧化物。在阴极表面形成的氢氧化物会流向阳极，并与锌反应释放能量，从而为其他设备提供动力。

“问题是，这种反应不是非常可逆的，”德国明斯特大学（University of Münster in Germany）的材料科学家孙伟（Wei Sun音译）表示，这样就很难为电池充电。常规锌-空气电池中的苛性电解质还会使阴极和阳极降解。为了解决这些问题，孙伟和他的同事使用一种新的电解质制成了锌-空气电池，该电解质含有憎水离子。这些离子粘附在阴极上，从而阻止了电解液中的H₂O与阴极表面上的氧气反应。结果，来自阳极的锌离子可以传播到阴极并直接与空气中的氧气反应。这种相对简单的反应很容易向后运行（逆向反应）以给电池充电。

更重要的是，新的电解质不会使电池的电极退化，这有助于使电池寿命更长。在实验室实验中，孙伟及其同事能够在160个小时内对新的锌-空气电池单元进行320次放电和充电。更多信息请注意浏览原文。

When two is better than four

Batteries based on the reaction of zinc and oxygen have been used for more than a century, but these have been primary (that is, nonrechargeable) cells. These batteries use an alkaline electrolyte and require a four-electron reduction of oxygen to water, which is a slow process. Sun et al. show that with the right choice of nonalkaline electrolyte, the battery can operate using a two-electron zinc-oxygen/zinc peroxide chemistry that is far more reversible. By making the electrolyte hydrophobic, water is excluded from the near surface of the cathode, thus preventing the four-electron reduction. These batteries also show higher energy density and better cycling stability.

Science, this issue p. 46

Abstract

Rechargeable alkaline zinc-air batteries promise high energy density and safety but suffer from the sluggish 4 electron (e−)/oxygen (O2) chemistry that requires participation of water and from the electrochemical irreversibility originating from parasitic reactions caused by caustic electrolytes and atmospheric carbon dioxide. Here, we report a zinc-O2/zinc peroxide (ZnO2) chemistry that proceeds through a 2e−/O2 process in nonalkaline aqueous electrolytes, which enables highly reversible redox reactions in zinc-air batteries. This ZnO2 chemistry was made possible by a water-poor and zinc ion (Zn2+)–rich inner Helmholtz layer on the air cathode caused by the hydrophobic trifluoromethanesulfonate anions. The nonalkaline zinc-air battery thus constructed not only tolerates stable operations in ambient air but also exhibits substantially better reversibility than its alkaline counterpart.

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