MOFs Derivatives As Cathode Materials For Aqueous Zinc-ion Batteries

The ever-increasing energy consumption are driving a rising demand for renewable,green and low-cost energy storage technologies,the electrochemical energy storage technology has been promoted.Lithium-ion batteries（LIBs）have achieved commercialization because of their high energy density and long cyclic life.Nevertheless,the increasing concerns about rare lithium resources,high cost and combustible organic electrolytes strongly restrict their further application as large-scale energy storage system.Aqueous zinc-ion batteries（ZIBs）with adequate zinc resources,low cost,high conductivity of aqueous electrolyte and high safety hold great promise for grid-scale energy storage.However,it is still hindered by the limited choices of suitable cathode materials with high performance for aqueous ZIBs.In this paper,we study the cathode materials for ZIBs,in which we developed the high performance cathode based on metal organic frameworks.The main research contents are as follows:（1）V-MOF@graphene was used as the precursor to obtain the two-dimensional hierarchical and porous V₂O₅@graphene via thermal oxidation treatment,and then it was used as the cathode material for aqueous ZIBs.When the ratio of graphene is 5%,the V₂O₅@graphene achieved the best electrochemical performance.The V₂O₅@graphene cathode delivered an ultrahigh specific capacity of 378 m Ah g^-1at a high current density of 2 A g^-1.Moreover,a high reversible capacity of 200m Ah g^-1after 1000 cycles at 1 A g^-1can be achieved.（2）The V₂O₃@graphene composite with various graphene ratio was obtained via thermal decomposition of V-MOF@graphene template under Ar atmosphere.When the ratio of graphene is 5%,the V₂O₃@graphene achieved the best electrochemical performance.The resultant V₂O₃@graphene cathode delivered a high reversible capacity of450 m Ah g^-1at 0.1 A g^-1,superior rate capability of 350 m Ah g^-1at 2 A g^-1,and long cyclic stability with 87%capacity retention after 1000cycles at 2 A g^-1.（3）The nanohoneycomb-shaped Mn₃O₄@Mn O₂core-shell composite was prepared via a facile thermal decomposition of Mn-BTC template along with a hydrothermal process,which was further used as the cathode for aqueous ZIBs.The results show that the Mn₃O₄@Mn O₂exhibit more excellent electrochemical performance than Mn₃O₄and Mn O₂,and the corresponding Mn₃O₄@Mn O₂that denoted as Mn-O-0.2possesses the optimum electrochemical performance when the dosage of KMn O₄is 0.2 g.The Mn-O-0.2 cathode delivered a high discharge capacity of 223 m Ah g^-1at the current density of 0.1 A g^-1,and a high discharge capacity of 165 m Ah g^-1can be delivered even at a high current density of 2 A g^-1.Besides,the Zn//Mn-O-0.2 battery achieved an excellent capacity retention of 63.8%after 600 cycles at 1 A g^-1.