The Academician Chen Jun at College of Chemistry, Nankai University has made breakthroughs in the construction of sodium-free pre-filled “respirable” sodium-CO2 batteries using inexpensive sodium carbonate and carbon nanotubes. The research results are published in the first issue of Research. 

    The primary version of the breathable battery is a lithium-oxygen battery, with lithium as the negative electrode and carbon, noble metal or transition metal oxide as air positive electrode. Greenhouse gas CO2 is obtained from the outside during discharge, and CO2 is released when charged. Therefore, it is called a breathable battery. The rechargeable sodium-CO2 battery derived from this, which is generally a type of battery where sodium is used as a negative electrode, carbon is used as a positive electrode. Compared with lithium-oxygen batteries, these batteries are not only abundant in raw materials, but also easy to prepare, and increases the safety during the experiment. CO2, as a greenhouse gas, can also be turned into resource to achieve sustainable development of green. 

    Nevertheless, there are difficulties in the development of sodium-CO2 batteries: excessive sodium and negative electrodes are prone to dendrites, resulting in short-circuit of the battery, which poses a safety hazard, and the preparation of sodium metal is mainly through electrolytic melting of sodium chloride or sodium hydroxide. Chen’s team tried to construct a sodium-CO2 battery from sodium carbonate. However, since sodium carbonate has poor conductivity, it is difficult to achieve electrochemical decomposition of sodium carbonate at a low overpotential. Based on the above difficulties, Chen Jun's research group used the sodium carbonate cheap composite material obtained by the dissolution precipitation method on the surface of multi-walled carbon nanotubes as the positive electrode and conductive carbon as the negative electrode to construct the sodium-free pre-filled respirable sodium-CO2 battery. Through the control of the charging capacity, the quantitative generation of metallic sodium on the negative electrode side is realized, and the formation of dendrites is successfully suppressed by utilizing the characteristics of the large specific surface area of the conductive carbon. 

    After testing, the battery can ensure that the charging voltage is lower than 4 V after 100 cycles of the cut-off capacity of 0.3 mAh/cm2. The research team further assembled a single cell with a capacity of 350 mAh and an energy density of 183 Wh/kg (based on the entire battery mass). 

    Sodium carbonate is easy to prepare in industry, and carbon is widely existed in nature. The research results of Chen Jun's group have successfully constructed a breathable sodium-CO2 battery using cheap and safe sodium carbonate and carbon as raw materials, avoiding the negative electrode. The pre-filling of sodium metal can effectively reduce the safety hazard of the battery and provide a new idea for the design of the safety battery. In addition, the Martian atmosphere contains 95% CO2, and the “breathable” sodium-CO2 battery constructed by this work is expected to provide a potential electrochemical energy system for Mars exploration. 

    Research is a new comprehensive high-level international English science and technology journal jointly created by China Association for Science and Technology (CAST) and the American Association for the Advancement of Science. It is the first collaborative journal of Science since its founding in 1880. Its international editor-in-chief is the University of Minnesota's Distinguished McKnight University Professor Cui Tianhong. Research has carried out solicitation and publicity for academicians of the Chinese Academy of Sciences, American Academy of Sciences, the Canadian Academy of Sciences, researchers of various disciplines at home and abroad, and strives to become an internationally renowned comprehensive scientific journal with international first-class academic standards in the short term in virtue of the high-influence international communication platform and ample international high-end academic resources of Science. Since August 22, 2018, the Research inaugural article began to publish online OA successively. The first issue published nine articles whose writers from universities such as Cambridge University and University of California. Academician Chen Jun. Research results on breathable sodium-CO2 batteries was the first article published online.