Design And Application Of High Performance Aqueous Zinc-dual Halogen Batterie

In recent years,the development of the lithium battery industry has been increasingly challenged by issues such as the shortage of raw materials,the flammability and explosiveness of organic electrolytes,high assembly costs,and difficulties in developing the recycling market.Aqueous electrolytes can eliminate safety hazards from the root cause,and metal zinc has lower costs and more stable chemical properties.Therefore,in the development process of non-lithium battery systems,aqueous zinc-based batteries are a type of battery device with broad development prospects.Aqueous zinc-based batteries can be roughly divided into ion insertion/desertion and chemical conversion types.The cathode material structure of ion insertion/desertion type aqueous zinc-based batteries is prone to damage due to ion insertion and desertion behavior,resulting in lower discharge specific capacity and poor cycling stability of the battery.Chemical conversion aqueous zinc based batteries can provide high specific capacity and avoid capacity degradation caused by ion insertion and desertion.Halogen ions are suitable as active materials for cathode materials of such batteries due to their suitable reduction potential,multivalent state variability and fast reaction kinetics.However,previous work mainly focused on the construction of zinc single halogen batteries based on two electron conversion redox pairs（X₂+2e^-=2X^-,X=Cl,Br,I）,failing to utilize the multivalent variability of halogen ions.This project designs a zinc-dual-halogen battery through the interaction between two types of halogens,achieving the redox conversion of high valence halogen ions and improving the electrochemical performance of the battery system.The main work is divided into:Firstly,the aqueous zinc-dual halogen battery based on multi electron conversion was designed.The structure of the electrolyte,the electrochemical performance of the zinc negative electrode,the reaction mechanism of the system,and the electrochemical performance were studied by combining molecular dynamics simulation,program simulation,theoretical calculation,and electrochemical experimental characterization.The results indicate that introducing a high concentration liquid electrolyte（ZLL electrolyte）composed of lithium bromide（Li Br）and lithium nitrate（Li NO₃）into the electrolyte can reduce the content of free water molecules in the system,thereby expanding the electrochemical stability window.The high concentration of lithium ions（Li⁺）in the electrolyte system can generate electrostatic shielding effect on the zinc negative electrode,inhibiting the generation of zinc dendrites.Bromine ions（Br^–）can form halogen intermetallic compounds（[IBr₂]^–）with iodine ions to activate I⁰/I⁺reactions.In addition,[IBr₂]^–can further undergo Br^–/Br⁰ conversion under high voltage.The multi electron conversion mechanism designed in this way,which can achieve three continuous redox reactions（i.e.,I^–/I⁰,I⁰/I⁺,and Br^–/Br⁰）,increases the discharge specific capacity of the battery by nearly twice compared to traditional zinc single halogen batteries.Subsequently,the high performance quasi-solid-state zinc-dual halogen battery was constructed.The quasi-solid-state electrolyte was prepared by UV light initiation using high concentration electrolyte as bulk electrolyte.This gel electrolyte inhibits the dissolution and diffusion of reaction intermediates by weakening the activity of free water molecules in the electrolyte system,so that the assembled quasi solid zinc double halogen battery system can have more stable cycling performance while achieving high discharge specific capacity.The assembled battery exhibits high area specific capacity(1.91 m Ah cm^-2)and energy density(3.11 m Wh cm^-2),as well as excellent cycling performance（capacity retention rate of 82%after 500 cycles）.