Electrolyte Regulation With Metal-organic Framework Additives Toward Stable Zinc Anode For Zinc Ion Batteries

Lithium-ion batteries are widely used in the field of energy storage due to high output power,low self-discharge and long cycle life.However,safety and environmental issues hinder the development of lithium-ion batteries in the field of energy storage owning to limited lithium resources,volatile and toxic organic electrolytes.In recent years,zinc ion batteries are regarded as a strong competitor of the next generation of energy strorage devices because of high safety,abundant resources,high theoretical capacity(820 m Ah g^-1,5855 m Ah cm^-3),and high hydrogen evolution potential（-1.06 V vs.Standard hydrogen electrode）.However,dendrite growth,corrosion and hydrogen evolution on the surface of zinc metal anode shorten the battery cycle life.The current solutions include current collector design,zinc anode surface modification and electrolyte modification.The procedure of the first two methods is more complicated,while electrolyte modification strategy is convenient operation and cost saving,which is expected to realize large-scale application.Metal-organic framework（MOF）have different metal centers,high porosity,largespecific surface area and abundant regulatory sites,which support their application in the research of electrolyte additives.It can inhibit dendrite growth,reduce the generation of by-products,achieve uniform zinc plating/stripping,and improve the cycle life of zinc ion batteries.In this thesis,five kinds of MOF materials are used as electrolyte additives.The specific contents and results are as follows.（1）The effects of HKUST-1（Cu）,MIL-53（Fe）,MIL-53（Al）and ZIF-8 as electrolyte additives were discussed.From the perspective of preparation,characterization and performance testing,ZIF-8 was selected for detailed performance and mechanism exploration.The solvent structure of zinc ion is adjusted due to anionphilic nature of ZIF-8.Thus,zinc ion desolvation is faster,the nuclear barrier is reduced,and zinc ion deposition is uniformed to achieve excellent performances.Under the optimal addition concentration of ZIF-8 at 2 mg m L^-1,the cycle life of symmetric battery can reach about1000 h at 2 m A cm^-2 and 1 m Ah cm^-2.（2）ZIF-67 was employed as an electrolyte additive,and the mechanism of performance improvement was explored.By using its excellent zincophilic properties,ZIF-67 preferentially adsorbs on zinc anode,hinders dendrite growth and improves interface compatibility between electrode and electrolyte,thus improving battery performances.Under the optimal addition concentration of ZIF-67 at 2 mg m L^-1,the cycle life of the symmetric battery can exceed 2500 h at 5 m A cm^-2 and 1 m Ah cm^-2.