The need for alternative anode materials for lithium-ion batteries (LIBs) is one of the decisive steps towards the electrification of our public and private transportation, since the state-of-the-art anode material graphite intrinsically limits the energy and power density of current LIBs. As a potential alternative, alloying metal-oxides such as ZnO and SnO_2 have been widely studied, mostly due to their high theoretical specific capacities of 988 mAh g~(-1) and 1494 mAh g~(-1), respectively. Nevertheless, the pure oxides reveal poor electrochemical performance as a result of the eventually irreversible formation of the Li_2O matrix and the pronounced volume variation, causing active material exfoliation. When doped with transition metals, however, the Li_2O formation turns very reversible and the theoretically possible capacities can be achieved. As an example, Co-doped ZnO offers substantially higher specific capacities than pure ZnO (i.e., 966 mAh g~(-1) vs 330 mAh g~(-1)). Recently, the class of TM-doped alloying metal oxides has been extended to Fe-doped GeO_2, offering even higher specific capacities than transition metal doped SnO_2 (theoretically 2152 mAh g~(-1)).
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