Rechargeable Li/CO2 battery
Authors: Liu Yali , Wang Rui , Lyu Yingchun , Peng Jiayue , Li Hong , Chen Liaquan 
Published: February 2020

In recent years, rechargeable nonaqueous lithium air batteries have attracted much attention as a result of their high energy density [1, 2]. However, it is very difficult for most batteries to work in the ambient air for the reason that the moisture and carbon dioxide in the air will affect their performance [2]. If the reactive gas contains CO2, there will be Li2CO3 formation in the discharging process. It has been reported that Li2CO3 is very difficult to decompose during charging process. However, recently H. S. Zhou reported that the main reaction in the charge process is the decomposition of Li2CO3 if the lithium air battery works in the ambient air [3].
In addition, CO2 is a type of greenhouse gas and is harmful to the climate. Thus, we hope to utilize it in the energy storage and conversion, such as a Li/CO2 battery. In 2011, K. Takechi et al reported a Li/CO2:O2 (from 0 to 100% volume CO2) battery, which didn’t show a reversible charge capacity with a cut-off voltage of 4.5 V with the carbonate-based electrolyte [4]. B. D. McCloskey et al reported a Li/O2 battery with CO2 as a contamination gas (10% volume). This battery employed LiTFSI-DME as electrolyte and a sloped charging voltage profile up to 4.8 V was reported only in the first cycle [5]. Besides, Archer et al reported a primary Li/CO2 battery which cannot be recharged and only work in the high temperature [6].
Recently, Sun and Scrosati reported an electrolyte based on tetraethylene glycol dimethyl ether (TEGDME), with which a rechargeable Li/O2 battery could operate over many cycles under high current rate and could reach a high specific capacity [7].
In our recent work [8], we found that when lithium triflate-TEGDME was used as the electrolyte, the Li/CO2:O2 (2:1, volume ratio) battery and Li/CO2 battery could operate reversibly. The specific capacities of Li/O2 battery, Li/CO2:O2 (2:1) battery and Li/CO2 battery were 2273 mAh g-1, 1808 mAh g-1 and 1032 mAh g-1, respectively based on the weight of Ketjen Black. In addition, from XRD, FTIR and SEM analysis we observed that the main discharge product is Li2CO3 in both batteries and the products can decompose in the recharging process. In Li/CO2 battery, another main discharge product may be carbon which could be confirmed by EELS and Raman spectroscopy with porous Au as cathode. In addition, electrochemical behaviors of a series of air electrodes, kinetic analysis and in situ XRD, TEM, SEM investigation on the products will be reported in this meeting. Based on current investigations, Li/CO2 battery could be a potential candidate as energy storage device if the polarization could be solved.
Acknowledgement
Financial support from CAS project "Strategic Priority Research Program" of the Chinese Academy of Sciences (XDA01020304) and National project 973 (2014CB932300,2012CB932900) are appreciated.
References
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