期刊
ENERGY STORAGE MATERIALS
卷 25, 期 -, 页码 154-163出版社
ELSEVIER
DOI: 10.1016/j.ensm.2019.10.019
关键词
Lithium-magnesium dual ion; Defects; DFT-calculations; 7Li and 19F solid-state NMR
资金
- French National Research Agency under Idex@Sorbonne University for the Future Investments program [ANR-11-IDEX-0004-02]
- Sino German TU9 network for electromobility [16N11929]
- U.S. DOE [DE-AC02-06CH11357]
- Royal Society [UF130329]
- Faraday Institution [EP/S003053/1, FIRG003]
- EPSRC [EP/L000202]
- Engineering and Physical Sciences Research Council [EP/S003053/1] Funding Source: researchfish
- The Faraday Institution [FIRG003] Funding Source: researchfish
- EPSRC [EP/S003053/1] Funding Source: UKRI
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 [Li-Ti + Mg-Ti] 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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