| Polyaniline(PANI)has attracted much attention because of its easy synthesis,low cost,good stability,broad conductivity after doping,and unique proton doping process.In the process of electropolymerization of polyaniline,when the anode material is more active,anodic dissolution occurs on the metal anode surface while polyaniline is generated,and the anodic dissolution of metal has an important effect on the morphology,structure and properties of polyaniline.Therefore,it is important to establish the relationship between the structure and the electrochemical properties of the material in order to deeply investigate the electrochemical polymerization PANI process performed on the surface of copper foil.Copper foil collector is an important component of lithium-ion batteries,used to connect the internal and external circuits and carry the active material layer of the negative electrode.The contact interface resistance between the copper foil collector and the active material is relatively high,which makes the active material easily fall off during charging and discharging making the battery capacity decay,and it becomes one of the important directions of collector material modification by forming polyaniline composites on the surface of copper foil to improve the interface characteristics between the copper foil collector and the electrode active material.In this study,polyaniline was electrochemically prepared by constant voltage method on the surface of copper foil collector,and the effect of voltage on the structure and morphology of polyaniline was investigated,while the battery system was constructed with lithium titanate material,graphite,lithium hexafluorophosphate and modified copper foil as anode material,cathode material,electrolyte and anode collector,respectively.The results of the study showed that the nanoparticles of PANI film modified collector led to a significant improvement in lithium-ion battery performance.The experimental results show that the PANI particle layer was obtained by electropolymerization on the surface of copper foil collector with sulfuric acid doping during polymerization under constant voltage conditions.The obtained samples were characterized by SEM,and the effects of the electrochemical polymerization process parameters(sulfuric acid concentration,voltage,and electropolymerization time)on the structural morphology of PANI particle layers were investigated to obtain the optimal electrochemical polymerization process parameters.The optimal process parameters were: aniline concentration(0.2 M),sulfuric acid concentration(0.05 M),polymerization time(10 min),and voltage(1.4 V).The thickness of polyaniline at the optimum electrochemical polymerization process parameters of 3 μm was measured by a multimeter thickness gauge,and the surface of the copper foil consisted of polyaniline particles of 200 nm size.The EDS results yielded that the PANI particles were uniformly distributed on the surface of the copper foil collector.UV spectroscopy and IR spectroscopy characterization yielded that the polyaniline layer is present in redox state and is electrically conductive.In this study,the growth mechanism of polyaniline was investigated by cyclic voltammetry.The results showed that the acid concentration was too low and the anode was dominated by the loss of electron reaction of OH-,making it difficult to form polyaniline complexes.However,with the increase of acidity,there is the appearance of redox peaks due to sulfuric acid affecting the structure of aniline monomer in a doping manner,leading to the formation of polyaniline.When the sulfuric acid concentration reached 0.05 M,the redox peak began to disappear significantly,indicating that the sulfuric acid concentration was too large,leading to an increase in current density,and the anode was dominated by the anodic dissolution reaction of copper,and the aniline polymer film was difficult to form.There is variability in the polymerization products with increasing aniline concentration,and the polymerization potentials are not the same because the thickness and structure of the reaction products change with increasing aniline concentration.The electrochemical performance of the battery system constructed before and after the modification of the copper foil collector was tested.The cycle performance test showed that the capacity of both batteries decayed after 500 cycles at 1 C magnification,but the discharge specific capacity of the modified copper foil(PANI/Cu)group was still higher than that of the unmodified copper foil(bare/Cu)group.The capacity retention of the battery assembled with 1.4V PANI/Cu composite lithium copper foil was 75.6% after 1000 cycles at 10 C magnification.The 1.3V PANI/Cu capacity retention rate is 48.8%,1.2V PANI/Cu capacity retention rate is41.9%,1.1V PANI/Cu capacity retention rate is 31.9%,and bare/Cu capacity retention rate is 40.4%.The results showed that the resulting polyaniline prepared at a voltage of1.4 V could better improve the cycling stability of the battery. |
