Journal
ACS APPLIED MATERIALS & INTERFACES
Volume 13, Issue 20, Pages 23853-23865Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsami.1c05809
Keywords
large-sized Li-O-2 battery; high energy density; local chemism inconsistency; rechargeability; LiAc center dot 2H(2)O; Li2CO3
Funding
- Science and Technology Nova Plan of Beijing City [Z191100001119032]
- Beijing Excellent Talents Training Program (Youth backbone individual project) [Z2018000097607G379]
- Beijing Municipal Science and Technology Project [Z181100004518003]
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Despite the theoretical ultrahigh energy density of Li-O-2 battery chemistry, practical Li-O-2 batteries are often hindered by electrolyte and O-2 maldistribution, leading to local inhomogeneity at the cathode interface and the formation of lithium acetate, which in turn affects the rechargeability of the batteries.
Due to the theoretical ultrahigh energy density of the Li-O-2 battery chemistry, it has been hailed as the ultimate battery technology. Yet, practical Li-O-2 batteries usually need to be designed in a large-sized pattern to actualize a high specific energy density, and such batteries often cannot be cycled effectively. To understand the inherent reasons, we specially prepared large-sized (13 cm x 13 cm) Li-O-2 model batteries with practical energy output (6.9 Ah and 667.4 Wh/kg(cell)) for investigations. By subregional and postmortem analysis, the cathode interface was found to have severe local inhomogeneity after discharge, which was highly associated with the electrolyte and O-2 maldistribution. The quantitative results by X-ray photoelectron spectroscopy (XPS) evidenced that this local inhomogeneity can exacerbate the generation of lithium acetate during charge, where the locally higher ratio of unutilized carbon surface and less Li2O2 after discharge would result in increased lithium acetate formation for a subsequent local overcharge. Moreover, verification experiments proved that the byproduct lithium acetate, which had been of less concern, was recalcitrant and triggered much larger polarization compared with the commonly reported byproduct Li2CO3 during battery operations, further revealing the key limiting factors leading to the poor rechargeability of batteries by its accumulation at a pouch-type cell level.
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