Preparing Of Polyaniline/Cu Composite Anode Current Collector By Electrochemistry Polymerization For Lithium-ion Batteries

Cu foil current collector?lithium battery Cu foil?is an important part of lithium-ion batteries.It is used for bearing anode active material layer and connecting internal and external circuits.In industrial production,the active material layer is combined with the Cu foil current collector only by a simple coating process,so the interface contact resistance is relatively high.Moreover,the structure of the active material layer will change during the continuous charging and discharging process,so the active material layer is easy to fall off from the current collector surface,resulting in the battery capacity attenuation.To solve this problem,this paper proposes to construct a new type of composite anode Cu foil current collector?PANI/Cu?.Through surface modification of polyaniline,constant current polymerization method is used to generate polyaniline layer on the surface of Cu foil current collector?Bare/Cu?,so as to increase the bonding strength between Cu foil current collector and active material layer and improve the electrochemical performance of lithium-ion batteries.In this paper,the method of galvanostatic polymerization method is used to control the electrochemical polymerization parameters?sulfuric acid doping concentration,aniline concentration,current density,polymerization time?to control the electropolymerization reaction process and the growth rate of polyaniline particles,and finally the polymerization on the surface of Cu foil produces a dense uniform and flat polyaniline particle layer.The mechanism of polyaniline formation by electropolymerization on copper foil surface was investigated.The experimental results show that increasing sulfuric acid concentration or decreasing aniline concentration during galvanostatic polymerization can make the dissolution rate of copper foil anode faster than that of polyaniline,which is not conducive to the formation of polyaniline particle layer.Too small or too large current density is not conducive to the formation of dense uniform and flat polyaniline particle layer.Polymerization time is too short or too long,will make the polyaniline layer loose or superimposed too thick and uneven.Therefore,galvanostatic polymerization process was optimized as follows:sulfuric acid doping concentration:0.05M,aniline concentration:0.2M,current density:0.3m A cm^-2,polymerization time:15min.Based on SEM and E-t curve analysis,the electrodeposition of polyaniline layer on Cu foil surface goes through three stages.The first stage:electroadsorption of aniline monomer and electrolyte;The second stage:nanometer polyaniline crystal nucleus formation;The third stage:the growth of nano-polyaniline particles and the formation of polyaniline layer.The SEM analysis results showed that the galvanostatic polymerized polyaniline layer was 1.8?m thick and composed of 50 nm nano-polyaniline particles.The existence of nano-polyaniline particle layer was beneficial to enhance the bonding strength between the active material and the current collector.The results of EDS-Mapping energy spectrum show that the polyaniline particles are uniformly distributed on the surface of Cu foil.FT-IR and UV-vis analysis confirmed that the polyaniline layer obtained by sulfuric acid doped electropolymerization exists in oxidation-reducing state and has conductivity.PANI/Cu and Bare/Cu?both loaded lithium titanate electrode material layers?were used as working electrodes,and Li plate was used as counter electrode to assemble the half-cell.The cycle performance test showed that the discharge retention capacity of PANI/Cu battery and Bare/Cu battery were 155.0 m Ah g^-1 and 137.6 m Ah g^-1 respectively after 500 cycles of 1C.After 1000 cycles of 10 C cycling,the capacity retention rate of PANI/Cu battery is 70%,which is much higher than 61%of Bare/Cu battery.Polyaniline layer is beneficial to improve the cycling stability of the battery.Both rate capability and cyclic voltammetry tests show that PANI/Cu battery has good reversibility and cyclic stability.The electrochemical impedance of PANI/Cu cell shows that the polyaniline layer effectively reduces the impedance of PANI/Cu cell.