Study On Conjugated Carbonyl Polymers As Anode Materials For Aqueous Zinc Ion Batteries

By using rich and cheap inorganic salt aqueous solution as the electrolyte,aqueous battery systems showed better ionic conductivity than organic system,which implied the better rate performance.In addition,environmental and stable water resource make it become a low-cost and safety energy storage device.Due to the high specific capacity,aqueous zinc ion battery has been widely studied and own a great development background.However,the current reports mainly focused on the exploration of cathode materials with the zinc metal as the anode.Generally,the zinc metal would lead hydrogen evolution reaction and zinc dendrite easily,limited the development of aqueous zinc ion battery.Therefore,this paper focused on the exploitation of anode materials,stated the synthesis of the conjugated carbonyl polymer anode materials for aqueous zinc ion battery,and investigated the electrochemical performance.Otherwise,analyzed the metal ion in anode materials embedded mechanism,assembled the drainage whole batteries to taking electrochemical performance test,indicating that the zinc metal anode is replaceable.The 1,4,5,8-naphthalentetracarboxylic acid diamide polymer（PNDI）was prepared by condensation reflux method.PNDI-180 was synthesized at 180℃by temperature control,which showed a diameter of about 6μm.The electrochemical performance of PNDI-180 in different electrolytes(1.0 mol L^-1 ZnSO₄,Zn（C₂H₃O）₂,ZnCl₂ and Zn（NO₃）₂)was compared by cyclic voltammetry and galvanostatic charge and discharge technology tests.The best electrochemical performance was found in 1.0 mol L^-1 ZnSO₄ electrolyte.At 100 mA g^-1,the electrode had a specific discharge capacity of 236.2 mAh g^-1with an idea coulombic efficiency of 100%,and capacity retention ratio reached 96.7%after 100 cycles.Even at 1000 mA g^-1,it still exhibited a specific capacity of 210.3 mAh g^-1,after 1000 cycles,the capacity retention ratio was 96.4%.The electrochemical reaction mechanism of PNDI was determined by XPS and FT-IR characterization methods,the excellent capacitance performance of the electrode was determined from the reversible conversion of C=O and C-O-Zn.To explore the feasibility of material application,PNDI-180//ZnMn₂O₄ aqueous full cell was assembled.It was found that excellent rate and stability performance still existed.It showed a specific capacity of 108.6mA g^-1 at 50 mA g^-1,with an energy density of 153.4 Wh kg^-1.Even at 1000 mA g^-1,it could also achieve a specific capacity of 67.1 mAh g^-1,furthermore,after 500 cycles at 100 mA g^-1,it gained a capacity retention ratio of 82.1%.The 1,4,5,8-naphthalenetetrarboxylic acid aniline polymer（m-PNDDI）was prepared by a solvent-thermal method.FT-IR characterization,cyclic voltammetry and galvanostatic charging-discharge test were used to confirm that m-PNDDI was the better choice for the anode of zinc ion battery.The morphology of uniform nanoplate composite sphere with high porosity synthesized at the concentration of 0.1 mol m L^-1 was obtained,and the diameter was about 30μm.The m-PNDDI gained a discharge capacity of 190.1 mAh g^-1 at 100 mA g^-1 in 1.0 mol L^-1ZnSO₄.After 100 cycles,the capacity retention ratio was 85.3%and coulombic efficiency was91.2%.In order to improve the stability and coulombic efficiency of the electrode,the strategy of adding Na⁺was used to optimize the electrolyte.It was found that the coulombic efficiency and cycle stability of the electrode were improved in 1.0 mol L^-1 ZnSO₄+0.5 mol L^-1 Na₂SO₄electrolyte.Under 100 mA g^-1,the discharge specific capacity of the double salt system was178.8 mAh g^-1.After 100 charging and discharging cycles,the capacity retention ratio was96.7%.When the current density increased to 1000 mA g^-1,it still showed specific capacity of134.6 mAh g^-1.After 1000 cycles,the coulombic efficiency was close to 100%with a capacity retention ratio of 85.3%.The reaction mechanism of Zn²⁺/Na⁺in m-PNDDI was investigated by XPS and FT-IR characterization,and the electrode demobilization reaction was determined to be a reversible transformation of C=O and C-O-Zn/Na.In order to explore the practicability of the material,m-PNDDI//β-MnO₂ full cell was assembled.It was found that the full battery showed better performance in the double salt electrolyte system,and the wonderful performance of the anode was perfectly retained.It showed a specific capacity of 100.1 mAh g^-1 at 50 mA g^-1,with an energy density of 137.6 Wh kg^-1.Even at 2000 mA g^-1,the full cell still showed a specific capacity of 78.8 mAh g^-1,which respected the excellent rate performance.After 1000 cycles under 1000 mA g^-1,the capacity retention ratio reached at 85.9%.