Unusual Hybrid Magnesium Storage Mechanism in a New Type of Bi 2 O 2 CO 3 Anode.

Bismuth and bismuth-based compounds have been extensively studied as anodes as prospective candidates for rechargeable magnesium batteries (rMBs). However, the unsatisfactory magnesium-storage capability caused by the typical alloying reaction mechanism severely restricts the practical option for anodes in rMBs. Herein, polyaniline intercalated Bi 2 O 2 CO 3 nanosheets are prepared by an effective interlayer engineering strategy to fine-tune the layer structure of Bi 2 O 2 CO 3 , achieving enhanced magnesium-storage capacity, rate performance, as well as long cycle life. Excitedly, a stepwise insertion-conversion-alloying reaction is aroused to stabilize the performance, which is elucidated by in / ex situ investigations. Moreover, first-principles calculations confirm that the coupling of Bi 2 O 2 CO 3 and polyaniline not only increases the conductivity induced by the strong density of states and the interior self-built-in electric field but also significantly reduces the energy barrier of Mg shuttles. Our findings shed light on exploring new electrode materials with an appropriate working mechanism toward high-performance rechargeable batteries.