Design Of Porous Carbon-based Cathode Materials For High Performance Rechargeable Zinc-Air/Iodine Batteries

With the virtues of high theoretical capacity(820 mAh g^-1)and abundant reserves,zinc has been used to fabricate various zinc-based batteries,such as zinc-air and zinc-iodine batteries.The coupling of Zn with oxygen from air enables to fabricate high-performing zinc-air battery.To replace cathode material with iodine,the Zn-iodine battery also is highly promising as alternative energy storage device due to the high energy density of iodine,as well as low cost,good reversibility.Nevertheless,the rational design and structural optimization of the cathode materials are highly desirable to improve the electrochemical performance of the batteries.This thesis demonstrated the rational design of air electrode and iodine-based cathodes to fabricate advanced batteries with zinc on the basis of carbon-based materials.With the chemical composition and structure characterization,the experimental results and theoretical calculation were incorporated to reveal the relationship between structure and electrochemical performance,aimed to improve the battery performance and cycling stability.The main results are summarized below:（1）The porous nitrogen-doped carbon nanofibers encapsulated with well-dispersed Co3Fe7 nanoparticles（Co3Fe7-PCNF）were synthesized by employing polyvinylpyrrolidone（PVP）as soft template via simple electrospinning and subsequent carbonization.The hierarchical porous and edge-rich carbon structure induced by the pyrolysis of soft template（PVP）was helpful in exposing more catalytic sites,and facilitated the rapid ion and electron transfer.Detailed characterization revealed that the synergistic catalysis of the bimetal Co3Fe7 nanoparticles and nitrogen-doped carbon nanofibers would contribute to improve catalytic activities for oxygen reduction and evolution reactions,leading to high-performing Zn-air battery.（2）Honeycomb-like porous N,P co-doped carbon materials（HP-NPC）was synthesized by using the three-dimensional ordered polystyrene spheres as hard template and tetrasodium 1-hydroxyethylidene diphosphonate as pH buffer to initiate the polymerization of dopamine,forming the uniform coating shell.The subsequent carbonization resulted in the formation of hierarchical porous structure due to the thermal decomposition of organic precursors and the removal of template,which provided efficient space for loading of iodine and reduced the charge transfer resistance.Importantly,the N and P co-doping would enhance adsorption ability of iodine on carbon surface.Thus,the as-obtained HP-NPC/I2 enabled to fabricated advanced Zn-I2 battery with good long-term stability.（3）A facile one-pot approach was demonstrated to prepare doughnut-like carbon with atomic bridging of iron atom via the coordination with nitrogen（namely B-Fe-NC）.The combination of experimental and theoretical calculations revealed that B-Fe-NC with the FeN4-C atomic bridging structure was regarded as efficient host material for iodine species to accelerate the redox conversion via the physicochemical confinement effect.Moreover,B-FeNC possesses great electrical conductivity and abundant porous structure.Thus,the Zn-I2 battery with the as-obtained B-Fe-NC/I2 exhibited good stability in high current density,high specific capacity,remarkable high-rate capability.