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Unraveling the fundamentals of Li-O(2) battery chemistry is crucial to develop practical cells with energy densities that could approach their high theoretical values. We report here a straightforward chemical approach that probes the outcome of the superoxide O(2)(-), thought to initiate the electrochemical processes in the cell. We show that this serves as a good measure of electrolyte and binder stability. Superoxide readily dehydrofluorinates polyvinylidene to give byproducts that react with catalysts to produce LiOH. The Li(2)O(2) product morphology is a function of these factors and can affect Li-O(2) cell performance. This methodology is widely applicable as a probe of other potential cell components.

We report a significant difference in the growth mechanism of Li 2 O 2 in Li-O 2 batteries for toroidal and thin-film morphologies which is dependent on the current rate that governs the electrochemical pathway. Evidence from diffraction, electrochemical, FESEM and STEM measurements shows that slower current densities favor aggregation of lithium peroxide nanocrystallites nucleated via solution dismutase on the surface of the electrode; whereas fast rates deposit quasi-amorphous thin films. The latter provide a lower overpotential on charge due to their nature and close contact with the conductive electrode surface, albeit at the expense of lower discharge capacity.

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prevent further reactions between the electrolyte and Li metal which decrease the CE, as well as Li metal dendrite growth at the Li surface. Attempts to tackle one or both of these issues have relied on approaches such as tailoring the electrolyte to modify the SEI, [6] introducing an artificial SEI or surface layer on Li metal, [7] and homogenizing the flux of Li + ions during the deposition process. [8] In the pursuit of a high performance LMB, the accurate measurement of Li CE is the most critical factor to predict the cycle life. As shown in Table 1, when the CE is close to 100%, even a 0.1% increase in CE can lead to a dramatic increase in the cycle life of Li metal batteries. However, the measurement of Li CE is often affected by various factors and the measurement methods reported in literature often give different values, even for the same cell design. For example, an extreme caution needs to be taken when handling Li samples during preparation, transfer, and analysis to avoid atmospheric exposure. With so much effort being put into making the Li metal anode a reality, there is an urgent need for a common method for the accurate determination of CE for LMAs and LMBs. Here, we investigated various factors that affect the measurement of Li CE and proposed a more accurate method to determine the CE of Li metal. In this work, we were able to develop a reliable method for measuring CE which can be used as a standardized technique by other researchers and help avoid discrepancy in reported values of CE by different groups. Very accurate values of CE can be calculated and used to quantify the amount of Li consumed during cycling and estimate the cycle life of LMBs.