Study On 3D Ordered Macroporous MOFs-based Cathode Material For Aluminun Ion Battery

Porous materials play an important role in a wide range of applications such as catalysis,separation,and energy.In particular,some crystalline porous materials,such as zeolites,metal organic frameworks?MOFs?,and covalent organic frameworks,due to their uniform pore size and orderly pore distribution,often have a great improvement in performance,which has attracted widespread attention.However,on account of the intrinsic characteristics of these materials,the pore size range of these porous materials is limited to the range of micropores,which makes them extremely limited in applications controlled by diffusion.Therefore,the design and development of hierarchical porous materials with macropores or mesopores has important research significance.MOFs have attracted a lot of attention because of their controllable structure and composition,especially the Co-based MOFs of transition metals are more widely used,because the outermost layer of cobalt ions has holes,which can effectively promote electron transfer,this makes it widely used in the field of electrochemistry.Unlike other secondary batteries,the reactive ions in aluminum ion batteries are chloroaluminate ions,with an ion radius of about 0.59 nm,much larger than Li⁺,Mg²⁺,and Na⁺,and the diffusion of large-sized ions is still a problem in electrode reactions.Therefore,this paper focuses on the preparation of three-dimensional ordered MOFs single crystals,and proposes a one-step carbonization-selenization method to prepare three-dimensional ordered macroporous CoSe₂@C composites for the diffusion of large-sized ions in aluminum ion batteries and the aluminum storage performance was tested.The specific research content is as follows:?1?A saturated solution-based double-solution assisted method was proposed to prepare a cobalt-based three-dimensional ordered macroporous MOFs single crystal?ZIF-67?.Using this method,the nucleation process of ZIF-67 was successfully controlled,making ZIF The-67 precursor successfully crystallized and grew in the three-dimensional ordered styrene template voids.The obtained three-dimensional ordered macroporous single crystal has the microstructure of conventional ZIF-67;macroscopically,it exhibits a symmetrical tetrahedral morphology,and the order of the macropore channels is consistent with the crystal plane orientation.The cobalt-based three-dimensional ordered macroporous single crystal prepared by this method has controllability and easy operation.?2?Based on the three-dimensional ordered macroporous MOFs prepared above,the one-step carbonization-selenization method was used to convert the three-dimensional ordered macroporous ZIF-67 into a three-dimensional ordered macroporous CoSe₂@C composite material.The composite material has a three-dimensional ordered structure of three-dimensional ordered macroporous MOFs,and the interconnected large pore channels could facilitate the diffusion of large-sized ions.Also,the CoSe₂ particles are uniformly wrapped in a three-dimensional ordered macropore conductive carbon skeleton,which not only improves the conductivity of the material but also effectively increases the active sites.When used as a cathode material for an aluminum ion battery,it exhibits excellent electrochemical performance.After 1000 cycles,the specific capacity can still maintain 125m A hg^-1,at current density of 2 A g^-1 and the Coulomb efficiency is 96%;and it shows excellent rate performance(the specific capacity of 83 m A hg^-1 at a current density of 5 A g^-1).