Studies On Performance Of Aqueous Zinc Ion Battery Electrode And Construction Of All-in-one Flexible Device

Rechargeable aqueous zinc ion batteries（AZIBs）with abundant reserves,low price,high stability,low redox potential（-0.76 V）,high specific capacity(820 m Ah g^-1)and high ionic conductivity(about 1 S cm^-1)has attracted widespread attention both at home and abroad.AZIBs mainly consist of anode and cathode active materials,aqueous electrolyte,current collector and separator.Nevertheless,the electrochemical performance of the battery is largely limited by the cathode and anode materials.Serving as a common anode materia of AZIBs,Zn metal anode suffers from dendrites growth and other side reactions（such as corrosion,passivation,and hydrogen precipitation）during cycling,which would eventually lead to lower plating/stripping coulombic efficiency（CE）and low utilization of zinc.The generated hydrogen also arouses bulging of the battery,which greatly limits the cyclic life and electrochemical performance of battery and seriously lead to battery failure.As a typically cathode material,Mn O₂ would undergo a serious structural transformation during the battery cycle along with the long-term insertion/extraction of Zn²⁺ions and protons,leading to the collapse of the structure.Meanwhile,the dissolution of Mn O₂ leads to the degradation of active substances during the cycle,resulting in a sharp decline in battery capacity.Thus,the capacity and cycle stability of AZIBs are limited.Therefore,this work mainly focuses on the problems and challenges of AZIBs,respectively from the ferroelectric polymer modified zinc anode surface,polyelectrolyte in situ intercalation manganese dioxide cathode material to improve the overall electrochemical performance and structural stability of AZIBs.This thesis mainly includes the following three aspects:（1）Establishment of ferroelectric polymer coating on zinc anode surfaceFerroelectric polymers spontaneously generate charges on their surfaces due to their inherent polarization.In this work,we construct a ferroelectric polymer coating on the zinc anode surface by surface engineering to inhibit the growth of zinc dendrites and the occurrence of side reactions.Due to the inherent ferroelectricity of polyvinylidene fluoride,it can effectively regulate the electric field gradient distribution and weaken the electric field intensity on the zinc surface,reduce the nucleation overpotential of Zn.This is conducive to the uniform deposition of Zn²⁺and thus largely inhibits the growth of Zn dendrites.At the same time,the weakening of the electric field strength on the zinc surface can effectively alleviate the hydrogen precipitation reaction and reduce the occurrence of other side reactions.Thanks to the excellent versatility of ferroelectric polyvinylidene fluoride,the results shown that the cycle performance of Zn//Zn symmetric cells with ferroelectric polymer protective layer in neutral electrolyte Zn SO₄ exceeds 1700 h(0.5 m Ah cm^-2 deposition capacity),and has excellent electroplating/stripping stability.The ferroelectric polymer coating provides a low-cost and scalable production method for the development of anode materials for AZIBs.（2）Design of polyelectrolyte intercalated Mn O₂ cathode materialsPolyelectrolyte Poly（diallyldimethylammonium chloride）（PDDA）has good prospects for industrial applications due to its excellent stability,relatively high visible light transparency,water treatment properties,and high electrical conductivity.In this work,we configured a certain concentration of PDDA and manganese sulfate solution as the deposition solution to ionize PDDA into PDDA ions in aqueous solution,and subsequently synthesized manganese dioxide intercalated with PDDA ions by in situ electrochemical co-deposition.PDDA ions can play a role in widening the layer spacing and stabilizing the layer structure between manganese dioxide layers.The results showed that the intercalated Mn O₂ exhibited wide layer spacing（～0.97nm）and low resistance.PDDA ions intercalated Mn O₂ were assembled with zinc metal into batteries,which showed high specific capacity and brilliant rate performance.The synthesis method of polyelectrolyte intercalated cathode material is an effective means to improve the cathode material,and provides a good strategy for the construction of high capacity and stability of cathode material.（3）Construction of all-in-one flexible deviceIn this work,we constructed a flexible wearable zinc ion battery device with all-in-one structure.The resultant all-in-one zinc ion battery features an all-in-one structure.The structure avoids relative sliding and separation between the integrated layers,ensuring a highly compact structure and integrity with a thickness of only 97μm,which greatly shortens the diffusion path of ions and promotes the diffusion kinetics during charge and discharge.In addition,thanks to the unique structure and well-design of electrode materials,the battery provides an improved capacity of 353.8m Ah g^-1,and features an ultra-long lifetime of over 500 cycles with a capacity retention of 94.1%.Impressively,AZIB showed high flexibility and wide temperature resistance in the electrochemical cycle.These excellent characteristics indicate that the integrated zinc-ion battery has a good application prospect in the field of wearable electronic devices and implanted biomedical devices,providing a solution for the further application of flexible zinc-ion battery.