Design Of Rechargeable Metal-iodine Batteries And Their Electrochemical Performance

Given the looming concerns of energy crisis and climate change,the concepts of developing sustainable energy resources have drawn global spotlights and triggered the search for improving energy storage systems.Herein,we focused on several rechargeable metal-iodine battery systems which show practical value.Based on the purpose of delving energy storage mechanism,we conducted our research for fabricating low-cost,safe and eco-friendly battery systems on two pathways,which are fabricating effective iodine loading electrode materials and probing the relationships among electrodes architecture,components and electrochemical performance,respectively.These fundamental studies are stated as follows:In the study of Zn-I₂ battery system,a sustainable aqueous Zn-I₂ battery was developed and the electrochemical performance was further systematically probed.In this work,porous active carbon cloth was employed as efficient iodine loading substrate to significantly improve battery electrochemical performance and electrode stability.When coupled with weak acidic aqueous electrolyte,Zn-I₂ battery system with capacity which exceeds theoretical capacity was fabricated.The as-prepared Zn-I₂ battery expressed an ultra-low overpotential of 50 mV and glacial capacity fading rate as well as weak self-discharge behavior,which are superior than recently reported metal-iodine batteries.Based on the results of electrochemical analysis and spectroscopy studies,the“one step”conversion reaction between iodine and iodide without formation of polyiodide intermedia was revealed.A quasi-solid-state Zn-I₂ battery was fabricated,and the electrochemical performance in deformation was further studied.The as-prepared quasi-solid-state battery showed highly reversible cycling performance.Even being treated with different deformation and 50 times of folding,a steady capacity of⁹0%was still demonstrated.Moreover,this flexible quasi-solid-state Zn-I₂ battery achieved an appreciable energy density and power density,which is higher than most recently reported solid-state metal-iodine battery systems.With the merits of impressive energy density and low-cost,the highly flexible rechargeable Zn-I₂ battery shows new avenue for wearable electronics.In the design of Fe-I₂ battery,nitrogen doped hierarchical porous carbon framework was prepared to load iodine.The notoriously shuttling of iodine species was significantly alleviated by the porous hierarchical structure.Moreover,the doped nitrogen atoms accelerated the redox of iodine species during cycling.Interestingly,ascorbic acid demonstrated a propensity of suppressing the growth of Fe dendrite.As a result,the as-prepared Fe-I₂ battery showed a high capacity,superior power density and appealing features of low-cost,high safe and eco-friendly.As a result of selecting metal-iodine couple which matches with solar cells,the Fe-I₂ battery could be photo-charged by solar cells smoothly even in a wide range of illumination intensity,shedding lights to the development of smart energy storage grid for solar energy.In the design of Mg-I₂ battery,sustainable natural product?-cyclodextrin??-CD?was employed as iodine loading material.Inspired by the concept of saturation,?-cyclodextrin additive was added into electrolyte to alleviate the shuttling of iodine species.The fabricated Mg-I₂ battery demonstrated two step redox reaction corresponding to conversion between iodine and polyiodide and conversion between polyiodide and iodine,respectively.Moreover,a high capacity of 150 mAh g^-1 in 40cycles could be observed.The employment of?-CD significantly improves battery capacity and cycling stability,which suggests an open route to prepare low-cost and green Mg-I₂ batteries.