2D organic-inorganic supercrystalline structures with 3D layered ion channels for efficient aqueous zinc ion storage

Abstract

Aqueous zinc ion batteries (AZIBs) have become powerful substitutes for large-scale energy storage because of their high safety and low cost, so the design of high-performance cathode materials has always been a requirement. Layered VxOy is one key type of cathode materials for rechargeable AZBs. Usually, it shows two-dimensional (2D) ion diffusion mechanism through the intercalation/deintercalation of Zn2+ at edge sites, but is plagued by the inert basal planes. Here, polymelamine (PME) was successfully inserted into the layered structure of VO2 nH2O and an organic–inorganic supercrystalline structure (PMVO-sls) with layered structure along the c-axis and ab plane was formed, thus providing additional ion diffusion channels and abundant active sites. The highly efficient and ultrafast 3D Zn2+ intercalation/deintercalation behaviors along both the c-axis and ab plane of VO2 nH2O are realized for the first time in AZIBs. Moreover, PMVO-sls has rich oxygen vacancy (Od) which is beneficial to electrolyte transport and ion diffusion, and it is a very competitive electrode material. Experimental data and density functional theory calculation (DFT) have confirmed that the intercalation of PEM can improve the electronic conductivity of materials and explained the possibility of Zn2+ diffusion through 3D interlayer structural channels. As cathode materials for AZIBs in 3 M Zn (CF3SO3)2, PMVO-sls exhibited an ideal reversible capacity of 344 mA h g−1 at 0.2 A g−1, and excellent cyclic stability (121 mA h g−1 retained after 4,500 cycles at 10 A g−1, a retention rate of 93%). Furthermore, in PMVO-sls/2.8 M Zn (CF3SO3)2 + 0.2 M ZnSO4/Zn AZIBs, PMVO-sls has a higher reversible capacity with an reversible capacity of 392.1 mA h g−1 at 0.2 A g−1 and better cyclic stability (180 mA h g−1 retained after 6,000 cycles at 10 A g−1, a retention rate of 90%). This method can provide a new way for the synthesis of high quality cathode materials for AZIBs and other metal ion batteries.