Two-Dimensional Zeolite Imidazolate Framework Applied To The Anode Of Zinc-Ion Batteries

Environmental pollution and increasing energy demand promote the exploration and development of renewable energy.Lithium-ion batteries occupy a dominant position in the rechargeable battery market.However,their high price,poor lithium resources,toxic electrolytes,and potential safety problems seriously hindered their further large-scale energy storage applications.Rechargeable aqueous Zn-ion batteries are promising replacements for lithium-ion batteries.Due to its high theoretical gravitational capacity(820 m Ah g-1),volumetric capacity(5855 m Ah cm-3),low electrochemical potential(-0.76 V vs.SHE),an abundant resource and nontoxic,metal Zn is considered as an ideal anode for Zn-ion battery in water.However,the Zn anode is facing many challenges such as dendrite growth,hydrogen evolution reactions,and corrosion.During charging,uneven deposition of Zn can lead to the formation of dendrites,which can pierce the separator and cause an internal short circuit.The strategies to protect the Zn anode consist of two parts: interfacial design and three-dimensional(3D)host construction.Two-dimensional(2D)materials have the high specific surface area and rich chemistry.Studies have been carried out on the application of 2D materials to the Zn anode.To explore strategies for protecting Zn anodes,2D zeolite imidazolate framework(ZIF-L)materials as a typical 2D material applied to interface design and 3D host construction.The details are listed as follows:(1)First,we synthesized ZIF-L nanosheets directly grown on bare Zn(ZIF-L@Zn)as the interface to protect the Zn anode.The electric field distribution of the ZIF-L array is uniform,which is favorable to the uniform nucleation of Zn on the surface.The porous structure of ZIF-L nanosheets can quickly remove the solvation structure of Zn ions,provide a fast channel for ion diffusion,induce 3D diffusion,and inhibit dendrite growth.Removing the solvation structure can also effectively prevent side reactions.The cells were assembled to test the electrochemical performance of the samples.The stable operation of ZIF-L@Zn symmetric cells could be up to 2000 h with the voltage hysteresis of 80 m V.(2)Second,we further explored the strategy of ZIF-L applied to 3D host to protect the Zn anode.ZIF-L nanosheets were synthesized directly grown on the Ti meshes(TMs)(ZIF-L@TMs).During the synthesis process,the Cu ZIFL@TMs was doped with a certain proportion of Cu2+.Similarly,the uniformly distributed electric field of Cu ZIF-L@TMs promotes uniform nucleation of Zn.The porous structure of Cu ZIF-L@TMs provides channels for ion diffusion and avoids the accumulation and deposition of Zn2+.From the results of X-ray absorption fine structure spectra,the doped Cu is dispersed in the form of single atoms,replacing the position of Zn in ZIF-L.The density functional theory calculation results show that the introduction of Cu greatly improves the zincophilicity of the host,reduces the diffusion barrier,and inhibits the growth of Zn dendrites.The electrochemical properties of the assembled cells were tested.The Cu ZIF-L@TMs/Zn||Cu ZIF-L@TMs/Zn symmetrical cells exhibited a long cycle of 1100 hours at a current density of 1m A cm-2 and showed a low polarization of 50 m V.Even at a high current density of 6 m A cm-2 and a high depth of discharge(50%),the stable operation of Cu ZIF-L@TMs/Zn||Cu ZIF-L@TMs/Zn symmetric cells could be up to 650 h with the voltage hysteresis of 80 mV.