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Exploiting cationic vacancies for increased energy densities in dual-ion batteries

Abstract : Dual-ion Li–Mg batteries offer a potential route to cells that combine desirable properties of both single-ion species. To maximize the energy density of a dual-ion battery, we propose a strategy for achieving simultaneous intercalation of both ionic species, by chemically modifying the intercalation host material to produce a second, complementary, class of insertion sites. We show that donor-doping of anatase TiO2 to form large numbers of cationic vacancies allows the complementary insertion of Li+ and Mg2+ in a dual-ion cell with a net increase in cell energy density, due to a combination of an increased reversible capacity, an increased operating voltage, and a reduced polarization. By tuning the lithium concentration in the electrolyte, we achieve full utilization of the Ti4+/Ti3+ redox couple with excellent cyclability and rate capability. We conclude that native interstitial sites preferentially accommodate Li+ ions, while Mg2+ ions occupy single-vacancy sites. We also predict a narrow range of electrochemical conditions where adjacent vacancy pairs preferentially accommodate one ion of each species, i.e., a [LiTi ​+ ​MgTi] configuration. These results demonstrate the implementation of additional host sites such as cationic sites as an effective approach to increase the energy density in dual-ion batteries.
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Submitted on : Thursday, February 6, 2020 - 10:51:31 AM
Last modification on : Monday, April 19, 2021 - 8:56:18 AM
Long-term archiving on: : Thursday, May 7, 2020 - 1:53:53 PM

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Toshinari Koketsu, Jiwei Ma, Benjamin Morgan, Monique Body, Christophe Legein, et al.. Exploiting cationic vacancies for increased energy densities in dual-ion batteries. Energy Storage Materials, Elsevier, 2020, 25, pp.154-163. ⟨10.1016/j.ensm.2019.10.019⟩. ⟨hal-02468860⟩

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