Study On The Preparation Of Sn Powder By Electrodeposition In Ionic Liquid/water Mixture

Tin has excellent corrosion resistance,weldability,and lithium storage characteristics and is widely used in the semiconductor industry and the battery field.Tin powder is commonly used as an activating sintering additive,a lubricant additive,and a conductive coating.It is also the main raw material for high-performance lithium ion battery anode materials.However,their preparation methods have the disadvantages of long production process,high requirement for equipment,and easy introduction of impurities.Ionic liquid is a new type of green solvent with excellent properties such as low vapor pressure,good electrical conductivity and wide electrochemical window.It used for the electrolyte as a preparation of tin powder is expected to overcome the problems existing in the traditional production methods,improve the quality of the product,and has a certain scientific significance and industrial application prospects.In this paper,1-butyl-3-methylimidazolium hydrogensulfate?[Bmim]HSO₄?and choline chloride-ethylene glycol?ChCl-EG?were used as electrolytes for the electrodeposition of tin powders.Cyclic voltammetry and cathodic polarization method were used to study the electrochemical behaviors of tin powders prepared from[Bmim]HSO₄-SnO and ChCl-EG-SnCl₂·2H₂O systematically.By changing the experimental conditions,the relationship between tin powder morphology and electrodeposition parameters was determined and the control mechanism was determined.The main research results are as follows:?1?The concentration of SnO and the water content had a significant effect on the electrical conductivity of[Bmim]HSO₄,and the electrical conductivity gradually decreased with the increase of SnO concentration,and gradually increased with the increase of water content.The electrochemical reduction test of Sn?II?in[Bmim]HSO₄-SnO shows that both the deposition potential E_Sn?II?/Snn?II?/Sn and the cathode peak potential of the Sn are positively shifted with increasing SnO concentration,and the exchange current density i₀ increases.In addition,with the increase of water content,the initial reduction potential of Sn?II?is obviously shifted,and the cathode current density is greatly increased.?2?The SnO concentration,deposition potential,and water incorporation in[Bmim]HSO₄-SnO directly affect the morphology of the tin deposits.By changing the water content,deposition potential,and SnO concentration,the prismatic,sheet-like,hollow tubulars,and linear micro-nanostructured Sn powders can be obtained.?3?SnCl₂·2H₂O concentration and water content have a great influence on the electrical conductivity of ChCl-EG.The conductivity decreases with the increase of SnCl₂·2H₂O concentration,and the conductivity increases with the increase of water content.The process of reduction of Sn?II?to metallic tin on the glassy carbon electrode in the ChCl-EG-SnCl₂ system is a diffusion-controlled quasi-reversible process.The deposition potential of Sn?II?shifts with the increase of SnCl₂·2H₂O concentration and the amount of water added,and the relationship between the deposition potential and the concentration of SnCl₂·2H₂O conforms to the Nernst equation.Compared with the concentration of SnCl₂·2H₂O,the effect of water incorporation is more significant.In addition,the diffusion coefficient of Sn?II?ions in ChCl-EG-SnCl₂ system increases with the increase of temperature.Both of them accord with the Arrhenius formula,and diffusion coefficient increase first and then decrease with the increase of water content.?4?Electrodeposition experiments show that the water content and deposition potential have a significant effect on the morphology and rate of electrodeposited tin powder.As the amount of water added increases,the transition layer between the substrate and the deposited tin changes from a Cu₃Sn alloy to a Cu-Sn alloy.The morphology of the tin powder changes from fine needles to a granular shape,and then to a short rod shape...