Reversible magnesium and aluminium ions insertion in cation-deficient anatase TiO₂

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Reversible magnesium and aluminium ions insertion in cation-deficient anatase TiO₂

In contrast to monovalent lithium or sodium ions, the reversible insertion of multivalent ions such as Mg2+ and Al3+ into electrode materials remains an elusive goal. Here, we demonstrate a new strategy to achieve reversible Mg2+ and Al3+ insertion in anatase TiO2, achieved through aliovalent doping, to introduce a large number of titanium vacancies that act as intercalation sites. We present a broad range of experimental and theoretical characterizations that show a preferential insertion of multivalent ions into titanium vacancies, allowing a much greater capacity to be obtained compared to pure TiO2. This result provides a new strategy for the chemical design of materials for practical multivalent batteries