Study On The Preparation And Performance Of PAN-based Polymer Electrolyte For Zinc Ion Battery

Aqueous zinc ion batteries have received widespread attention due to their inherent safety,low cost,and high capacity(5855 Ah g^-1).However,it is difficult to solve a series of problems such as the dissolution of the positive electrode active material,the corrosion and passivation of the negative electrode metal zinc,and the dendrite growth piercing the separator caused by the active water in the water-based battery.The solid polymer electrolyte/gel polymer electrolyte does not contain water or has low active water content.The low water content,combined with a certain degree of strength and flexibility,is promising to solve the above-mentioned problems of aquepus zinc ion batteries.In this paper,a simple method was used to synthesize a polymer electrolyte in which polyacrylonitrile(PAN)as the polymer matrix and zinc acetate(Zn(OAc)₂)as the zinc source,named PAN/Zn(OAc)₂ polymer electrolyte.The conductivity of the electrolyte after the interface wetting is greatly increased to 2.2×10^-4S cm^-1,which is two orders of magnitude higher than that of the polymer electrolyte without interface wetting.Combined with experimental phenomena,it is believed that the surface of the electrolyte without surface wetting is covered with Zn(OAc)₂,which significantly increases the interface resistance of the polymer electrolyte.After wetting,the surface Zn(OAc)₂ can be dissolved,and improve the electrode/electrolyte interface contact.However,because the obtained polymer electrolyte has the performance of a solid polymer electrolyte,it is easy to be brittle in the air,and its solid-solid interface contact method makes the electrode/electrolyte interface contact bad,the polarization voltage is large,and the cycle is unstable.In view of the above problems,the stronger but brittle PAN is blended with the tougher UV-cured poly(ethylene glycol)diacrylate(PEGDA),after removing the solvent,PAN-PEGDA/Zn(OAc)₂ polymer electrolyte membrane.with both strength and toughness is obtained.The conductivity of the wetted PAN-PEGDA/Zn(OAc)₂ electrolyte reaches 6.2×10^-4 S cm^-1,which 3 times than the conductivity of PAN/Zn(OAc)₂;PAN-PEGDA/Zn(OAc)₂ polymer electrolyte membrane with both strength and flexibility makes the electrode/electrolyte interface contact well and significantly reduces the interface impedance;the addition of PEGDA after UV-initiated polymerization increases the Zinc ion migration number of the polymer electrolyte from 0.45 to 0.61,the glass transition temperature dropped by 3°C.Under the action of the PAN-PEGDA/Zn(OAc)₂polymer electrolyte membrane,the Zn||Zn symmetrical battery cycled stably for more than 150 hours,and the polarization voltage was significantly decreased and stabilized.The PAN-PEGDA/Zn(OAc)₂ polymer electrolyte is used to assemble a Zn||Mn O₂ full battery.The full battery cycled more than 200 times at a rate of 0.1C(0.03mAcm^-2),and the average coulombic efficiency is 91.2%.