Author(s) Liu, Z.; Balbuena, P.B.; Mukherjee, P.P.
Journal J Phys Chem Lett
Date Published 2017 Apr 06
Abstract

Besides lithium sulfide (Li2S), lithium persulfide (Li2S2) is another solid discharge product in lithium-sulfur (Li-S) batteries. Revealing the charge transport mechanism in the discharge products is important for developing an effective strategy to improve the performance of Li-S batteries. Li2S2 cannot transport free electrons due to its wide bandgap between the valence band maximum (VBM) and conduction band minimum (CBM). However, electron polarons (p(-)) and hole polarons (p(+)) can appear in solid Li2S2 due to the unique molecular orbital structure of the S2(2-) anion. The thermodynamic and kinetic properties of native defects are investigated. It is found that negatively charged Li vacancies (VLi(-)) and p(+) are the main native defects with a low formation energy of 0.77 eV. The predominant charge carrier is p(+) because p(+) has a high mobility. The electronic conductivity related to p(+) diffusion is dependent on temperature, and high temperatures are preferred to increase the conductivity.

DOI 10.1021/acs.jpclett.6b03063
ISSN 1948-7185
Citation J Phys Chem Lett. 2017;8(7):13241330.

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