Study Of Aqueous Rechargeable Battery Based On Organic Anode

With the development of the world economy,the combustion of fossil fuels results in serious pollution which has brought serious problems to the development of human society.The use of renewable energy not only reduces the risk of environmental pollution,but also promotes the harmony between human and nature.However,renewable energy usually possesses interstitial and regional characteristics.Therefore,it is necessary to find safe and efficient energy storage battery technologies to match it.Aqueous re-chargeable batteries（ARBs）have received widespread attention due to the high ionic conductivity,inherent safety and cost advantages of aqueous electrolytes.However,aqueous rechargeable batteries usually use metal ions as charge carriers,and these metal elements either have relatively limited reserves or high mining costs.Proton（H⁺）is not only the lightest and smallest of all ions,but also has the fastest ion mobility in aqueous solutions.Moreover,it is earth-abundant and readily available.Therefore,in this study,we have designed a new type of aqueous rechargeable proton battery based on organic anode and inorganic metal-organic framework compound cathode.The main contents of this research include:（1）The electrochemical properties of an organic conjugated molecule—dipyridophenazine（DPPZ）in acidic and alkaline aqueous systems are studied by cyclic voltammetry（CV）.The effect of p H,cyclic stability and charge-discharge rate performance etc.were investigated for DPPZ in a 0.05 M H₂SO₄ solution（p H=1）and a possible electrochemical reaction mechanism is proposed.The experimental results showed that the redox potential（E⁰）of DPPZ has a good linear correlation with p H within the range of p H 0～3.The slope is about 41 m V p H^-1,revealing that the charge-transfer reaction of DPPZ in acidic aqueous solution is basically a two-proton/two-electron process.Further electrochemical experiments revealed that the electrochemical response of DPPZ to K⁺is significantly weaker than the response to H⁺and DPPZ has almost no electrochemical response to Li⁺,Na⁺and Mg²⁺.In addition,the large planarπ-conjugated system and the low structural reorganization enengy of the phenazine unit can endow DPPZ with high chemical/electrochemical stability.（2）A redox-active metal-organic framework compound-indium Prussian blue（In HCF）was synthesized through a convenient co-precipitation method.Furthermore,the chemical structure of In HCF was analyzed by X-ray photoelectron spectroscopy（XPS）,thermogravimetric（TGA）,inductively coupled plasma emission spectroscopy（ICP-AES）and other characterization techniques.The electrochemical performance and the effect of p H were investigated and a possible reaction mechanism in an acidic aqueous system was proposed.The electrochemical results show that the E⁰ of In HCF is about 0.924 V,independent of p H value.However,the p H affects obviously its electrochemical reaction activity.In HCF shows high redox reversibility and good stability in 0.05 M H₂SO₄ solution.（3）A new type of aqueous proton battery was constructed by using DPPZ as the anode active material,In HCF as the cathode active material,and H⁺as the charge carrier,respectively.Owing to the reversible amination of the redox-active phenazine unit of DPPZ and the rapid intercalation/deintercalation of protons on In HCF,this proton battery exhibits a high specific capacity,excellent rate performance and outstanding cycling stability.At a current density of 1Ag^-1,the specific capacity reaches 133.1 m Ah g^-1.After 3000 charge-discharge cycles,the capacity retention rate at 6Ag^-1 still remains about 76.6%.That is to say,the capacity retention rate per cycle is as high as 99.991%.（4）A long-life aqueous dual-cation battery system was then constructed by employing DPPZ as the anode active material,In HCF as the cathode active material,H⁺/K⁺as the charge co-carriers,respectively.This dual-cation battery also shows a high specific capacity of 134.4 m Ah g^-1 at 1Ag^-1,excellent rate performance(90 m Ah g^-1 at 10Ag^-1)and out-standing cycling stability（the capacity retention of 82.5%after 5000cycles,coulombic efficiency of 99.7%and energy efficiency of 93.5%）.