Lithium-carbon dioxide (Li-CO 2 ) batteries are regarded as a promising electrochemical system owing to their energy storage capability and CO 2 utilization. However, the reported operating voltage of ~2.6 V is increasingly questioned as seemingly beyond the capability of the electrochemical carbon dioxide reduction reaction to carbon. Herein, the real operating voltage of a Li-CO 2 battery is reacquainted, and the operating voltage and the equilibrium potential are clarified to be ~1.1 V and ~2.82 V, respectively. The products formed at low voltage are identified to be crystalline Li 2 CO 3 , amorphous C, and explicitly amorphous Li 2 CO 3 . Moreover, by decoupling small currents, 1% O 2 , and 500 ppm H 2 O, the operating voltage plateaus are stimulated to ~2.0 V. An ever-increasing plateau can be achieved up to the reported level of ~2.6 V activated by a minor air leak or residue in test environments. Conclusively, the operating voltages of Li-CO 2 batteries are proposed to be deceptive and extremely sensitive to the surrounding environments. This work unveils the real operating voltage and provides the voltage regulation rules to advance next-generation Li-CO 2 batteries.
Safety hazards arising from lithium (Li) plating during the operation of lithium-ion batteries (LIBs) are a constant concern. Herein, this work explores the coaction of low temperatures and current rates (C rates) on Li plating in LIBs by electrochemical tests, material characterization, and numerical analysis. With a decrease in temperature and an increase in C rate, the battery charging process shifts from normal intercalation to Li plating and even ultimately fails at −20 °C and 0.5C. The morphology observations reveal the detailed growth process of individual plated Li through sand-like Li, whisker Li, dendritic Li, mossy Li, and finally bulk Li, as well as aggregated Li from sparse to dense. Through quantitative analysis, the dynamic pattern under long-term cycles is revealed. The low temperature and high C rate will lead to an increase in Li plating capacity and irreversibility, which are further deteriorated with the cycles. In addition, a critical condition of high Li plating and high reversibility at −10 °C and 0.2C is found, and further studies are needed to reveal the competition between kinetics and thermodynamics in the Li plating process. This work provides detailed information on the range and growth process of Li plating and quantifies Li plating, which can be used for practical Li plating prediction and regulation.
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