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 Use of trifluoromethane sulfonate in place of basic electrolyte enables electrochemical reversibility of zinc-air batteries. 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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基于过氧化锌化学的可充电锌空气电池

当两个优于四个时 基于锌和氧反应的电池已经使用了一个多世纪，但这些都是原电池（即不可充电电池）。这些电池使用碱性电解液，需要将氧气四电子还原成水，这是一个缓慢的过程。孙等人。表明通过正确选择非碱性电解质，电池可以使用更可逆的双电子锌氧/过氧化锌化学操作。通过使电解质疏水，水被排除在阴极的近表面，从而防止四电子还原。这些电池还表现出更高的能量密度和更好的循环稳定性。科学，这个问题 p。46 使用三氟甲烷磺酸盐代替碱性电解质可实现锌空气电池的电化学可逆性。可充电碱性锌空气电池具有高能量密度和安全性，但存在需要水参与的缓慢的 4 电子 (e-)/氧 (O2) 化学反应以及由腐蚀性电解质和大气碳引起的寄生反应引起的电化学不可逆性二氧化氮。在这里，我们报告了锌-O2/过氧化锌 (ZnO2) 化学反应，该化学反应在非碱性水性电解质中通过 2e-/O2 过程进行，这使得锌-空气电池中的氧化还原反应具有高度可逆性。这种 ZnO2 化学是由疏水性三氟甲磺酸盐阴离子引起的空气阴极上的缺水且富含锌离子 (Zn2+) 的内部亥姆霍兹层实现的。