Modification And Application Of Cu Current Collector For Silicon Anode In Lithium Ion Batteries

Increasing the energy density of lithium-ion batteries(LIBs)is an urgent need for emerging technologies such as electric vehicles,artificial intelligence,and virtual reality.Silicon(Si)with ultrahigh theory specific capacity(4200 mAh g-1),low operation voltage,environmental friendliness,and abundant natural reserves is considered one of the most promising anode materials for the next generation LIBs.However,the process of lithium insertion/extraction along with huge volume changes(>300%)leads to the pulverization of the Si particles and damage of electrode integrity.Considerable research efforts have been made to work out these challenges,such as various structures of Si materials and multifucational polymeric binders.In addition,Cu current collector modification,as an useful approach to deal with the electrode volume change,is yet to receive important attention.In view of aforementioned disadvantages of Si anode,this thesis designed and prepared a variety of modified current collectors to enhance the bonding force between Cu current collector and silicon anode.The main research contents and results are as follow:(1)Constructing three-dimensional(3D)Cu current collector to enhance the mechanical interlocking force between the silicon electrode and Cu current collector.A special 3D morphology(including needle,rod,and petal)was constructed on the surface of copper foil by alkaline solution oxidation method.The 3D structure increases the surface roughness of Cu foil and enhances the mechanical interlocking force.Meanwhile,the 3D structure is beneficial to increase the Cu specific surface area and effectively reduces the interface impedance of the electrode.In addition,the porous structure can provide sufficient buffer space for the volume change of Si during the cycling process.(2)Introducing the amido bond to strengthen the bonding force between the Si electrode and Cu current collector.A simple and efficient coating method was adopted to introduce amino functional groups on the surface of the copper foil.During the curing process of slurry,the amino on the surface of the copper foil and the carboxyl in the binder react chemically to form an amide bond.The combined action of the mechanical interlocking and chemical bondings significantly improves the interfacial adhesion force and reduce the contact loss inside the electrode.Benefiting from the improved binding stability,a favorable cycling performance is reached.