Manganese-based Quasi-Solid-State Zinc-Ion Battery And Its Performance Study

Along with the development of an era,the problems of energy shortage and environmental pollution has become more and more serious,and the storage and utilization of clean and efficient renewable energy has become a focus of research.As a preeminent energy storage device,lithium-ion batteries are used in various fields.However,lithium-ion batteries have certain problems such as lack of lithium resources,environmental pollution and safety hazards.As a new battery system,rechargeable aqueous zinc-ion batteries（ZIBs）have comprehensive advantages like environmental friendliness,high safety performance,easy fabrication,high theoretical capacity,and low cost.Manganese oxides,as the cathode material of aqueous zinc-ion batteries,have the advantages of high discharge voltage,high theoretical capacity,abundant resources and environmental protection,thus they have attracted much attention in recent years.However,its inherent poor electrical conductivity,instability during cycling,and significant volume change seriously affect the overall performance of the battery.In addition,the practical application of aqueous zinc-ion batteries is hindered by the growth of zinc dendrites and side reactions at the electrolyte-electrode interface,and the quasi-solid state Electrolytes can effectively alleviate the above problems and facilitate the development of flexible zinc-ion batteries.Based on this,the performance of quasi-solid-state zinc-ion batteries was investigated in this thesis by reducing both graphite oxide（r GO）modifiedδ-Mn O₂cathode material and laponite（Lap）modified polyacrylamide（PAM）gel electrolyte.The specific work is as follows:（1）Screening the properties of manganese dioxide cathode materials with different morphologies and structures,selectingδ-Mn O₂with a lamellar structure as the precursor,and combining the graphene with a two-dimensional lamellar structure with it to construct a sandwich structure of Mn O₂@r GO composites.As an excellent conductive carbon material,r GO can effectively improve the conductivity of the composites,and the introduction of graphene can availably to buffer the volume expansion of manganese-based materials during cycling and improve the cycle stability.By adjusting the amount of r GO added,it was found that the cathode（Mn O₂@8%r GO）with 30.2 mg r GO doping amount and the quasi-solid-state battery assembled with polyacrylamide（PAM）hydrogel as electrolyte exhibited the best electrochemical performance,which can provide a high reversible capacity of 287.3 m Ah g^-1at a current density of 0.2 A g^-1,and maintain a high reversibility of 94.5 m Ah g^-1after 2000 cycles even at a high rate of 2 A g^-1capacity.（2）The quasi-solid gel electrolyte contains a small amount of water retained in the stable polymer hydrogel,which not only has high mechanical strength and stability,but also provides high ionic conductivity and good protection of zinc metal electrodes.Utilizing the above optimized Mn O₂@8%r GO as the cathode,the polyacrylamide hydrogel was modified by hectorite,and the influence of hectorite doping on the electrolyte properties of the composite gel was investigated,and the optimized composite hydrogel electrolyte（PAM-5%Lap）of mechanical and electrochemical properties were prepared.More importantly,Lap is highly dispersed and charged in hydrogel,which helps to guide the uniform distribution of zinc ions and effectively avoid the occurrence of tip effect.The assembled Zn//PAM-5%Lap//Zn symmetric cell exhibited a low-voltage polarization of less than 60 m V for 2000 hours without short-circuit phenomenon or any overpotential rise,indicating its good suppression effect on Zn dendrites.It was assembled with Mn O₂@8%r GO cathode and electrodeposited Zn anode to form a flexible battery,which showed excellent anti-bending and anti-ring-breaking properties.