Study On The Action Mechanism Of High Efficient Additives For Acidic Copper Plating

With the global deployment of the 5G network and the development of the new energy industry,the production of electrolytic copper foil is important as a key material for the negative electrode of lithium batteries.At present,lithium electric copper foil generally has battery short circuit and failure due to thermal expansion fracture band and fatigue fracture,due to the low tensile strength of the key performance.Therefore,a new composite additive is developed in this article.The 6 μm copper foil which be used for lithium battery can effectively solve this problem.Starting with the action mechanism of the composite additives,the crystallization process,texture,morphology and grain size were studied.Firstly,linear sweep voltammetry,chronoamperometry and cyclic voltammetry were used to deeply explore the influence of different concentrations of MPS,HEC,gelatin and additive-D on copper deposition.Studies had shown that additives caused the nucleation process;MPS and HEC didn’t change the nucleation mode,but still maintained the transition from instantaneous nucleation to continuous nucleation;and when gelatin and D were added,the nucleation mode was instantaneous nucleation mode;adding only additive-D had no obvious effect on increasing the cathodic polarization;different concentrations of MPS caused rapid changes in the deposition rate.Taking dispersion ability,leveling ability,covering ability and coating appearance as evaluation criteria,the concentration of additive combination was optimized by orthogonal test.The optimization result was: 6mg/L MPS+6mg/L HEC+6mg/L gelatin+4mg/ L D.On this basis,the same method was used to study the mechanism of the composite additives,XRD characterized the preferred orientation of crystal planes and calculated the average grain size,and SEM characterized the micro morphology.The results showed that: different systems didn’t change the copper nucleation-growth mechanism,but affected the nucleation method and nucleation number density;each additive system could have a leveling effect on the micro morphology;deposition process,texture,average grain size and the warpage of the copper foil had a mutual influence and a multi-to-many intricate relationship.It could be found that the increase of cathodic polarization increased the value of N and reflected the average grain size;the increase of the average grain size only occured in the non-quaternary system where MPS and gelatin coexisted.Flat and smooth coating micro morphology was the result of the increase of the value of N,the preference of the(111)crystal plane and the decrease of other crystal plane coefficients.The decrease of copper foil warpage was affected by the decrease of the texture coefficient of the crystal plane(220)and the grain refinement.Finally,the mechanical performance test results of electrolytic copper foil prepared by new composite additives 6mg/L MPS+6mg/L HEC+6mg/L gelatin+4mg/L were: surface roughness Rz value droped below 2.0μm,tensile strength ≥ 450 MPa,which was an increase of more than 40% compared with conventional products.At the same time,it still reached 400 MPa after baking at 110℃ for 6 hours.The additives changed the uniformity of the electrochemical state of the foil crystallization front,improved the nucleation rate of the crystal nucleus,and changed the growth direction of the copper foil from crystal planes(111),(200),(220)to crystal planes(111)as the dominant growth.The average grain size was reduced from 38.11 nm to 20.16 nm,which realized the growth control of nano-scale grains on the surface of the copper foil.