Composites Of Perylene Diimide And Biomass-derived Carbons As Organic Cathodes In Lithium Ion Batteries

The cathodes in lithium-ion batteries(LIB s)are represented by LiCoO2 and LiFePO4,However,with the scarcity of mineral resources,the environmental pollution and high cost of waste battery recycling,inorganic cathode materials are bound to be replaced by environmentally friendly organic anode materials.This thesis focuses on the new organic cathode materialsIn this thesis,two kinds of organic cathode materials were prepared by composites of 3,4,9,10-perylenetetracarboxylic diimide(PDI)and biochar,including the organic cathodes(PDI/SC)composited with PDI and sucrose-derived carbon,and the flexible organic cathodes(FOC/CCF)composited with PDI and carbonized cotton fiber,both of which have excellent rate performance and stable cycling performancePDI/SC were prepared from PDI and sucrose-derived carbon(SC)by the acid solution method,which were composite materials supported on sucrose-derived carbon.According to the electrochemical performance test,it was found that the PDI/SC composite materials as the cathodes had outstanding electrochemical performance,when the wt%of PDI in cathodes was 46%:it exhibited an excellent specific capacity of 121 mA h g-1 at the current density of 0.05 A g-1,and had a reversible specific capacity of 72 mA h g-1 even at an ultra-high current density of 5.0 A g-1.Besides,after 500 charge-discharge cycles,it also maintained a high specific capacity of 91 mA h g-1 at a high current density of 1 A g-1,without obvious attenuationFOC/CCF were prepared from PDI and carbonized cotton fibers(CCFs)by the phase inversion approach,which were flexible organic cathode materials.According to the electrochemical tests,on the one hand,it was found that the electrochemical performances of flexible organic cathodes had a certain relationship with the carbonization temperature of CCFs.In the range of 700-900?,the cathodes electrochemical performances were improved with increasing carbonization temperature;On the other hand,the ratio of CCFs,PDI in flexible organic cathodes would also affect its electrochemical performances.When the wt%of CCFs and PDI were also 30%,the flexible organic cathodes could deliver the best electrochemical performance:It showed a high discharge capacity of 135 mA h g-1 at a current density of 0.05 A g-1(close to the theoretical specific capacity),and a reversible specific capacity of 101 mA h g-1 at a high current density of 2.0 A g-1.After 500 charge-discharge cycles,it also kept a specific capacity of 102 mA h g-1 at a current density of 0.5 A g-1,and its retention rate is as high as 90.5%.The FOC/CCF was furtherly assembled into a pouch full-cell because of its good mechanical stability,and the pouch full-cell manifested stable performances at various bent states,confirming the potentials of CCFs in flexible energy storage devices.