Preparation Of Polypyrrole-based Cathode Composite Material And Research On Its Sodium Electrical Properties

Now,sodium-ion battery(SIB)has been gaining increasing attention thanks to the abundance of Na resources.Na and Li share similar chemical properties in many aspects.Owing to larger size of Na cations of SIB,the material and technology of lithium ion batterry are not completely suitable for SIB.Hence,it’s very necessary to explore the suitable electrode materials for SIB.Conductive polymer Polypyrrole(PPy)possess the potential advantages such as tensile strength,low toxicity and structural diversity.The flexibility and mobility of the long chain within the polymer matrix can provide the elastic loose space and path for the ionic diffusion and deinserton/insertion,especially for larger Na~+.However,its conductivity is usually poor in the native state,which can be further enhanced after doping.Electrochemical polymerization can directly combine the polymer with the metal substrate and exclude the use of a polymer binder.The process is simple.For this purpose,PPy was doped with p-toluenesulfonate(TsONa)and PPy was co-doped with L-lactic acid(LA)and TsONa for high performance cathode in SIB via facile one-step electropolymerization,the separator and assembly in this paper as follows:(1)TsONa mono-doped PPy was synthesized as the cathode active material of SIB by facile one-step electrodeposition.The microstructure and morphology of the as-synthesized TsONa-doped PPy cathode was investigated in terms of SEM,EDX,XPS,XRD and FTIR.As expected,TsONa was indeed doped in PPy.The micromorphology of the sample was the cauliflower-like surface irregular microspherical particles.Furthermore,the electrochemical activity and reaction mechanism of TsONa mono-doped PPy cathode were investigated by galvanostatic charge/discharge,cyclic voltammetry and alternating current impedance.As expected,the obtained TsONa mono-doped PPy cathode delivered satisfactory electrochemical performances.The reversible discharge capacity of TsONa mono-doped PPy cathode remained about 98 mAh/g after at least 50 cycles,indicating high Na-storage activity of PPy matrix and high electronic conductivity induced by doping of TsONa.(2)PPy was co-doped with LA and TsONa for high performance cathode in SIB via facile one-step electropolymerization.The microstructure and morphology of the as-synthesized Ts ONa/LA co-doped PPy cathode was investigated in terms of SEM,FTIR.As expected,TsONa and LA were successfully doped in PPy.The micromorphology is oval-bud-like micro-particles.Furthermore,the electrochemical activity and reaction mechanism of TsONa-doped PPy cathode were investigated by methods of galvanostatic charge/discharge,cyclic voltammetry.Furthermore,Ts ONa/LA co-doped PPy cathode also delivered higher electrochemical performances than TsONa mono-doped PPy cathode.For example,the reversible specific capacity still maintained at about 116 mAh/g even after 50 cycles,higher than those of TsONa mono-doped PPy cathode,indicating LA with good Na-storage activity and the synergy effect of TsONa and LA.