Research Of Electrolyte Additives On Both Corrosion And Passivation Performances Of Zinc Electrode

Zinc is widely used as anode material for batteries due to its merits,including rich source,low toxicity,non pollution,high energy density and low cost,etc.However,both the utilization of zinc electrode and the life time of batteries significantly reduced due to the problems of corrosion and passivation of zinc in alkaline solution,resulting in serious impact on battery performance.Based on the problems above,additives are often added into electrode or electrolyte to improve the performance of zinc electrode.Among them,electrolyte additives have attached much attention due to the advantages of convenient operation and less investment.In this work,the influences of lauroamide propylbetaine(LAB),dodecyltrimethyl ammonium bromide(DTAB),DTAB/LAB composite additive DL or sodium dodecyl benzene sulfonate(SDBS)/LAB composite additive SL on performances of zinc electrode were investigated in 7.0 mol L-1 KOH saturated with ZnO by Tafel polarization curve,linear sweep voltammetry(LSV),clectrochemical impedance spectroscopy(EIS)and field emission scanning electron microscopy(FE-SEM)methods.The main contents of this work were as follo w s:(1)Different mass fractions of DTAB were added into 7.0 mol L-1 KOH saturated with ZnO to evaluate the electrochemical behaviors of zinc electrode using Tafel polarization curve,LSV and EIS tests.FE-SEM was carried out to analyze the surface morphologies of zinc.It was shown that the addition of DTAB inhibited the corrosion of zinc electrode,and DTAB belonged to anodic-type inhibitor.The adsorption of DTAB on the surface of zinc obeyed the Freundlich isotherm adsorption model.The highest corrosion inhibition efficiency of DTAB was up to 80.2%in the presence of O.07 wt%DTAB.FE-SEM analysis showed that the addition of 0.07 wt%DTAB was beneficial to the formation of dense porous protective film on the surface of zinc.Such a morphological greatly improved the utilization of zinc.In addition,potentials of both passivation and anodic dissolution current peak positively shifted in the presence of DTAB,indicating that the passivation was delayed.(2)The performances of zinc electrode in the presence of different concentrations of LAB in 7.0 mol L-1 KOH saturated with ZnO were investigated by Tafel polarization curve,LSV and EIS tests.FE-SEM was carried out to analyze the surface morphologies of zinc.The results suggested that LAB acted as cathodic-type inhibitor,which inhibited the corrosion of zinc electrode by decreasing the hydrogen evolution process.The inhibition effect and charge transfer resistance of zinc electrode increased with increasing concentrations of LAB due to the adsorption of LAB on the surface of zinc electrode,which were beneficial to inhibit the corrosion of zinc electrode.The adsorption of LAB obeyed the Langmuir isotherm adsorption model and the corrosion inhibition efficiency was up to 84.1%in the presence of 800 ppm LAB.In addition,the morphology of zinc surface in the presence of 8 00 ppm LAB was observed to be smoother than that in blank solution,indicating that the corrosion of zinc was inhibited.Anodic polarization curves confirmed that small amount of LAB was beneficial to delay the passivation.(3)The effects of composite additive DL on the performances of zinc electrode were investigated by Tafel polarization curves,LSV and EIS tests in 7.0 mol L-1 KOH saturated with ZnO.The results demonstrated that DL acted as cathodic-type inhibitor,which effectively inhibited the corrosion of zinc electrode.Compared with single system,the corrosion current density was greatly decreased,and the charge transfer resistance increased,suggesting that the corrosion of zinc electrode was effectively inhibited in the presence of DL in electrolyte.The highest corrosion inhibition efficiency was up to 96.1%in the presence of 0.05 wt%DTAB + 400 ppm LAB in electrolyte,indicating there was an obvious synergistic effect between DTAB and LAB.Anodic polarization curves indicated that the addition of DL additive effectively inhibited the passivation of zinc electrode.(4)Electrochemical properties of zinc electrode were studied by Tafel polarization curves,LSV and EIS tests in the presence of SDBS/SL in 7.0 mol L-1 KOH saturated with ZnO.It was shown that the inhibition efficiency was up to 7 8.8%and the passivation of zinc electrode was also delayed in the presence of 0.02 wt%SDBS in electrolyte.The results also indicated that the corrosion current density was decreased,and the charge transfer resistance increased.suggesting that the corrosion of zinc electrode was effectively inhibited in the presence of SL in electrolyte and SL worked as cathodic-type inhibitor.The highest corrosion inhibition efficiency of SL was up to 85.0%with addition of 0.02 wt%SDBS + 400 ppm LAB in electrolyte,indicating that there was an obvious synergistic effect between SDBS and LAB.Anodic polarization curves showed that the potential of passivation positively shifted in the presence of SL,suggesting that the passivation was obviously delayed.In summary,it was found that single additive(DTAB and LAB)and composite additive(DL and SL)have an inhibiting effect on both corrosion and passivation of zinc electrode.Compared with the single system,composite system showed a better effect after reasonable application of organic additives.