Study On Failure Mechanism And Electrolyte Modification Of Zinc-nickel Battery

Considering reserves and environmental problems,traditional fossil fuels have been unable to meet the energy needs of society in the future,and strengthening the use of renewable energy has become an important task.Due to its intermittence and instability,the efficient utilization of renewable energy brings great opportunities and challenges to energy storage equipment.Compared with lead-acid batteries and lithium-ion batteries,which currently occupy a dominant position in the market,aqueous Zn-based batteries stand out with their advantages of low cost,rich resource,environmental friendliness and non-toxicity.Among them,zinc-nickel batteries have attracted extensive attention because of their high open-circuit voltage（～1.75 V）and excellent rate performance.However,the short cycling life seriously limits the practical application of zinc-nickel battery.In order to solve the problem of cycling life more effectively,it is necessary to analyze the failure mechanism of zinc-nickel battery and modify the battery according to the key factors.Firstly,the failure mechanism of aqueous zinc-nickel battery was studied in detail.Through the measurement and analysis of electrolyte and gas composition of the battery under different cycle number,and the recombination experiment of key components,the failed component of zinc-nickel battery is identified as the negative electrode.Then,combined with phase analysis,morphology characterization and finite element simulation of the current/potential distribution of zinc anode,the root reason for the failure of the aqueous zinc-nickel battery was identified as the shape change caused by the uneven current distribution and zinc dissolution.The serious shape change of zinc anode reduces the effective surface area of charge and discharge reaction,and increases the possibility of dead zinc.So even if there is a large amount of zinc in the anode,the zinc-nickel battery will eventually fail to discharge.According to the conclusion of the failure mechanism,we carried out a targeted modification design for the zinc-nickel battery.In order to inhibit the solubility of Zn and Zn O in KOH electrolyte,K₃[Fe（CN）₆]was introduced as electrolyte additive,and the chemical adsorption of K₃[Fe（CN）₆]on zinc surface was used to reduce the contact between active material and electrolyte.Zinc can reduce K₃[Fe（CN）₆]to K₄[Fe（CN）₆].Due to the low solubility of K₄[Fe（CN）₆]in alkaline solution,a protective layer of K₄[Fe（CN）₆]was formed on zinc surface,which inhibited the corrosion and dissolution of active material.This modification strategy can effectively reduce the shape change of zinc anode in KOH electrolyte,increase the cycle life of zinc-nickel battery by more than two times,and significantly improve the capacity retention of the battery.