A mixed‐valence polyoxometalate‐based 3D inorganic framework cathode material for high‐efficiency rechargeable AZIBs

Abstract The global trend towards new energy storage systems has stimulated the development of electrochemical energy storage technologies. Among these technologies, rechargeable aqueous zinc‐ion batteries (AZIBs) have attracted considerable interest as a potential alternative to lithium‐ion batteries (LIBs) due to their affordable cost, environmental compatibility and high safety standards. In this study, a high‐quality electrode for AZIBs has been successfully developed using a dehydrated mixed‐valence polyoxometalate‐based three‐dimensional (3D) inorganic framework material known as [H 6 Mn 3 V IV 15 V V 4 O 46 (H 2 O) 12 ] (3D‐MnVO). This innovative 3D‐MnVO material is built from the alternate connections of {V 19 O 46 } “sphere‐shaped” clusters and μ 2 ‐{Mn(H 2 O) 4 } bridges, where each {V 19 O 46 } cluster is surrounded by three pairs of vertically distributed {Mn(H 2 O) 4 } units, thus resulting in the 3D interpenetrating grid‐like network from the infinite [‐{V 19 O 46 }‐µ 2 ‐Mn(H 2 O) 4 ‐{V 19 O 46 }] ∞ chains in three mutually perpendicular directions. The 3D framework structure of 3D‐MnVO possesses abundant oxygen vacancies, spacious and multi‐level interconnected channels for ion transport, which facilitates the efficient intercalation/deintercalation of hydrated Zn 2+ into the pores of the primary structure via the intercalation capacitance mechanism. As a result, the 3D‐MnVO electrode exhibits excellent diffusion rates and minimal interfacial resistance. At a current density of 0.1 A·g −1 , the 3D‐MnVO cathode delivers a commendable discharge capacity of 170.5 mAh·g −1 with 81.6% capacity retention after 100 charge/discharge cycles. Furthermore, even at a high current density of 1.0 A·g −1 , the 3D‐MnVO electrode delivers a remarkable reversible capacity of 198.9 mAh·g −1 . Our research results provide valuable insights into the development of advanced polyoxometalate‐based 3D inorganic framework electrode materials for high‐performance rechargeable AZIBs.