title: Revealing Charge Transport Mechanisms in Li2S2for Li-Sulfur Batteries.
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. Li2S2cannot 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 Li2S2due to the unique molecular orbital structure of the S22-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.
authors.affiliation: Department of Mechanical Engineering and ‡Department of Chemical Engineering, Texas A&M University , College Station, Texas 77843, United States.
authors.forename: Zhixiao
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Mechanical Engineering and ‡Department of Chemical Engineering, Texas A&M University , College Station, Texas 77843, United States.
authors.forename: Perla B
authors.identifier: http://orcid.org/0000-0002-2358-3910
authors.initials: PB
authors.lastname: Balbuena
authors.affiliation: Department of Mechanical Engineering and ‡Department of Chemical Engineering, Texas A&M University , College Station, Texas 77843, United States.
authors.forename: Partha P
authors.identifier: http://orcid.org/0000-0001-7900-7261
authors.initials: PP
authors.lastname: Mukherjee