Study On The Preparation Of Birnessite/Polyaniline Composite Material And Its Zinc Storage Performance

Aqueous zinc ion batteries have high application value and development prospects in large-scale energy storage and other fields.As the cathode material of aqueous zinc ion batteries,manganese dioxide has the advantages of abundant reserves,low price,safety and environmental protection,and has been rapidly developed in recent years.However,during the charging and discharging process,the crystal structure of manganese dioxide will transform to other tunnel structures,and the crystal structure will collapse after multiple phase changes,resulting in poor cycle performance of the battery.In view of the above problems,this thesis takes birnessite as the main research object,and on the basis of exploring its reaction mechanism as a zinc ion battery cathode material,try to stabilize its layered structure by introducing polyaniline between the birnessite layers to improve electrochemical performance of aqueous zinc ion batteries.The main results of this thesis are as follows:(1)Combining XRD,TEM,SEM and other methods,the birnessite electrode products under different charge and discharge conditions are analyzed,and the reaction mechanism and cycle attenuation mechanism of the birnessite electrode are revealed.The results show that the intercalation reaction of H⁺and Zn²⁺is mainly caused on the 1.32V discharge platform.The discharge products on the 1.2V discharge platform are tunnel-shaped Mn OOH,Zn Mn₂O₄,Zn Mn₃O₇·2H₂O and large pieces of(Zn(OH)₂)₃(Zn SO₄)(H₂O)₃.It can be seen from this that the layered structure of birnessite will transform to the tunnel structure of the discharge product during the charging and discharging process of the battery.After multiple phase transitions,the layered structure of birnessite will collapse,which will seriously affect the cycle performance of aqueous zinc ion batteries.(2)On the basis of the above mechanism research,an attempt was made to improve the electrochemical performance of the battery by introducing polyaniline between the birnessite layers and stabilizing its layered structure.The influence of different variables in the reaction on the structure,morphology and electrochemical properties of the birnessite/polyaniline composite was explored.The results show that under the condition of mixing birnessite and aniline hydrochloride raw materials in a certain ratio,polyaniline is mainly intercalated between the birnessite layers,and with the increase of the addition of aniline hydrochloride,the intercalation amount of polyaniline increases.Electrochemical test results show that proper polyaniline intercalation can stabilize the layered structure of birnessite to a certain extent and improve the conductivity of the composite material,thereby improving cycle performance and rate performance.The above research provides new ideas for improving the performance of manganese dioxide as a cathode material for water-based zinc-ion batteries.