Current lithium-ion intercalation technology, even when fully developed, is difficult to satisfy society's increasing demand of high-energy-density power sources for electric vehicles and electronics. Thus, non-aqueous alkali metal-oxygen (AM-O2: AM = Li, Na, etc.) batteries are promising to replace conventional lithium-ion battery due to their ultrahigh theoretical energy density.
However, AM is extremely reactive towards air and almost all nonaqueous electrolytes, resulting in significant parasitic reactions. Furthermore, uncontrollable Li or Na metal plating/stripping, generally emerging as dendrites, easily induces cells short circuit accompanying by fire/explosion events, plaguing AM anodes towards practical applications. Therefore, to achieve a safe and stable AM-O2 cell, it is important to solve the dendrite coupled with oxidation/corrosion issues of AM anode.
Recently, a research team led by ZHANG Xinbo from the Changchun Institute of Applied Chemistry (CIAC), Chinese Academy of Sciences, YAN Junmin from Jilin University, ZHANG Yu from Beihang University Beijing developed a long-life AM-O2 battery using Li-Na eutectic alloy as novel metal anode for the first time. Their findings were published in Nature Chemistry.
They found that Li and Na of Li-Na alloy exhibit similar reaction activities and therefore both can be employed as active components in batteries without sacrificing the specific capacity compared with other alloys (e.g., Na-Sn alloy). In addition, alloying Li and Na improves the corrosion resistance of single metal against O2 and electrolyte and suppresses the metal dendrites growth.
Importantly, in a Li-Na alloy battery, with the help of electrolyte additive, the resultant dendrite-suppressed, oxidation-resistant, and crack-free Li-Na alloy electrode endows the newly-proposed aprotic bimetallic Li-Na alloy-O2 battery with good performances.
Furthermore, by introducing efficient O2 reduction/evolution catalysts (e.g., Co/NCF), the cycling life and rate capability of Li-Na alloy-O2 battery are significantly improved.
"We believe that this strategy can also be applied to other metal electrodes, such as Zn, Mg, Ca, Al and so on." said ZHANG.
Meanwhile, this study provides a guidance for developing other bimetal batteries such as bimetal ion batteries and bimetal-S batteries. These batteries possess new chemistries, exhibit much better electrochemical performance than mono-metal batteries, and adopt collaborative methods to release the great potential of alkali metal anode.
Oxidation and corrosion resistance characterization of Li-Na eutectic alloy and Na electrodes; morphology comparisons for Li-Na alloy and Na electrodes after stripping/plating cycling; the electrochemical performance of Li-Na alloy batteries. (Image By YAN Junmin, ZHANG Yu, ZHANG Xinbo)
