High-mass loading Bi 2 O 2 CO 3 nanoflakes with crystalline structure transition as cathode for alkaline zinc battery

Rechargeable aqueous alkaline zinc batteries (AZBs) have received extensive attention due to their cost-effectiveness and environmental friendliness. However, the areal capacity of currently reported AZBs is still unsatisfactory especially at high mass loading, which hinders their further practical application. Herein, we propose a simple precipitate strategy to prepare low-cost Bi 2 O 2 CO 3 nanoflakes for AZBs. The resultant Bi 2 O 2 CO 3 undergoes a structural transformation during the charge/discharge cycle, which not only significantly changed the microstructure but also optimized the energy storage capability of the as-prepared material. At a high mass loading of 30 mg cm −2 , the as-fabricated electrode could attain a high areal capacity of 5.14 mAh cm −2 at the current density of 15 mA cm −2 , excellent rate capability (2.40 mAh cm −2 at 180 mA cm −2 ), and long cycling life of about 88.6% retention after 800 charge/discharge cycles. Ex situ XRD and SEM techniques show that the energy storage mechanism of the prepared material is predominantly contributed by the reversible conversion reaction between Bi and Bi 2 O 3 in the KOH aqueous electrolyte. This work might shed light on the construction of advanced materials in alkaline energy-storage devices.