Implications of the Formation of Small Polarons in Li2O2 for Li-Air Batteries
Lithium-air batteries (LABs) are an intriguing next-generation technology due to their high theoretical energy density of {approx}11 kWh/kg. However, LABs are hindered by both poor rate capability and significant polarization in cell voltage, primarily due to the formation of Li{sub 2}O{sub 2} in the air cathode. Here, by employing hybrid density functional theory, we show that the formation of small polarons in Li{sub 2}O{sub 2} limits electron transport. Consequently, the low electron mobility {mu} = 10{sup -10}-10{sup -9} cm{sup 2}/V s contributes to both the poor rate capability and the polarization that limit the LAB power and energy densities. The self-trapping of electrons in the small polarons arises from the molecular nature of the conduction band states of Li{sub 2}O{sub 2} and the strong spin polarization of the O 2p state. Our understanding of the polaronic electron transport in Li{sub 2}O{sub 2} suggests that designing alternative carrier conduction paths for the cathode reaction could significantly improve the performance of LABs at high current densities.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Laboratory Directed Research and Development (LDRD) Program
- DOE Contract Number:
- AC36-08GO28308
- OSTI ID:
- 1039086
- Report Number(s):
- NREL/JA-5900-53770; TRN: US201209%%150
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 85, Issue 3; Related Information: Article No. 035210
- Country of Publication:
- United States
- Language:
- English
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