Polypyrrole/Partially Reduced Graphene Oxide Composite As Cathode Materials For Lithium/Potassium Ion Batteries

Recent years,lithium-ion batteries have higher requirements due to the raise of energy vehicles.Due to the large-scale application of lithium-ion batteries,in recent years,the prices of Co and Li salts have risen,so searching for new battery materials has become a new development direction.It shows the optimal synthesis conditions of polypyrrole/partially reduced graphene oxide composites?PPY-pRGO?with improved electrical properties by oxidative polymerization were investigated by orthogonal experiments.The structure of material was characterized by XRD,TGA,FTIR,Raman,XPS,SEM and TEM.PPY-pRGO composite material was used as cathode material for lithium/potassium ion battery,and its electrochemical performance was characterized by charge-discharge test,CV and EIS.?1?Preparation of polypyrrole/partially reduced graphene oxide by designing orthogonal experiments.Four factors and three levels of experimental scheme were adopted,and the four factors were:graphite oxide concentration,pyrrole dosage,ultrasonic time and reaction temperature.After nine sets of orthogonal experiments,four factors were used as independent variables,and the capacity of the composite after 200 cycles was used as the dependent variable.The best synthesis conditions were determined by SPSS software analysis,namely,the graphite oxide concentration of 1 mg/mL,the pyrrole use level of 200?L,the ultrasonic time of 8 h and the reaction temperature of 353 K.?2?The structural composition,electrochemical performance and lithium storage mechanism of PPY-pRGO were studied.Results show that PPY is coated on the surface of graphite oxide,and reacts with the oxygen-containing functional group on the surface of GO.PPY-pRGO shows specific discharge capacity of 235.2 mAh g^-1 after 200 cycles at 100 mAh g^-1,and it maintains at 214.9 mAh g^-1 after 1200 cycles,with an average decay rate of only0.009%per cycle.At a current density of 1.6 A g^-1,it has a specific capacity of 141.1 mAh g^-1.PPY-pRGO sample has a capacitance of 51.4%at a sweep speed of 0.1 mV s^-1.The higher tantalum capacitance determines the good rate performance of PPY-pRGO.?3?The potassium storage mechanism and capacitance behavior of GO and PPY-pRGO composites as cathode materials for potassium ion batteries were also studied.Results show that both materials can be used as cathode materials for potassium ion batteries and have higher discharge specific capacity,especially PPY-pRGO composites.When used as a positive electrode material for potassium ion batteries,PPY-pRGO composite has a discharge specific capacity of up to 200.8 mAh g^-1 after activation at a current density of 100 mA g^-1.GO and PPY-pRGO composites have similar electrochemical behavior and capacitance behavior as lithium ion batteries when used as cathode materials.