Potassium Polyacrylate Based Gel Electrolytes For Zinc-Nickel Batteries

Zn-Ni batteries which demonstrate high output voltage,high specific energy,and environmental protection have attracted much attention.However,the poor cycle stability of the full battery caused by the shape change,dendrite growth and corrosion of the Zn anode still limits the commercialization of the Zn-Ni batteries.Therefore,it is necessary to find effective ways to improve the performance of Zn-Ni batteries.The gel electrolyte has a high elastic modulus and limited free water content,which can effectively inhibit the deformation,dendrite growth and corrosion of the Zn anode.In the first work of this article,we prepared a stable potassium polyacrylate(PAAK)-KOH gel electrolyte.Compared with the aqueous electrolyte,the porous gel electrolyte exhibits excellent ionic conductivity(0.918 S cm-1),a wide electrochemical stable voltage window(1.8 V),high elastic modulus and limited content of free water.We assembled two Zn-Ni batteries using PAAK-KOH gel electrolyte and KOH aqueous electrolyte,and then investigated their performance of cycle stability,shelf life and floating charge.The results show that by suppressing the shape change,dendrite growth and corrosion of the Zn anode,the cycle stability(776 h),shelf life(more than 431 h)and cycle life under floating charge conditions(more than 400 h)of the Zn-Ni battery based on gel electrolyte are higher than the traditional alkaline aqueous Zn-Ni battery.In the second work of this article,based on the PAAK framework,we added calcium lignosulfonate(CLS)to prepare a CLS-PAAK-KOH gel electrolyte.The freeze-dried CLS-PAAK-KOH gel electrolyte still has a porous structure,which is conducive to the ion conduction of the gel electrolyte.In addition,CLS-PAAK-KOH gel electrolyte has relatively high ionic conductivity and a wide electrochemical stability window of 1.9 V.The Tafel test shows that the Zn anode in CLS-PAAK-KOH gel electrolyte has lower corrosion current than that in PAAK-KOH gel electrolyte,which demonstrates that the CLS-PAAK-KOH gel electrolyte has a stronger inhibitory effect on the corrosion of Zn anode in alkaline environment.Compared with the Zn-Ni battery based on the PAAK-KOH gel electrolyte,the Zn-Ni battery based on the CLS-PAAK-KOH gel electrolyte exhibits an ultra-long cycle stability,shelf life(845 h)and excellent cycle life under float charge(696 h).In summary,this article proposes two gel electrolytes suitable for Zn-Ni batteries.The Zn-Ni batteries assembled based on the two gel electrolytes have shown excellent performance.In addition,the raw materials that prepared for gel electrolyte in this paper is abundant and low-cost.The preparation method of gel electrolyte is simple and the requirements for preparation conditions are very low.It is very suitable for large-scale production.