Design Of Co₃O₄ And Carbon-based Nanomaterials For Aqueous Zn Ion Batteries And Supercapacitors

Aqueous supercapacitors and aqueous zinc-ion batteries are two important components of environmentally friendly energy storage devices for their low cost,environmental friendliness and high safety.At present,the energy density,working voltage and cyclic life of aqueous batteries are far from meeting the actual needs.However,compared with the higher theoretical specific capacity of zinc anode,the capacity of cathode material for zinc-ion batteries still needs to be improved.Therefore,it is very important to design and develop aqueous zinc-ion battery cathode materials with high capacity,high voltage,high rate capacity and long life.At the same time,carbon nanomaterials with excellent conductivity and cyclic stability are very attractive for supercapacitors.However,the unsatisfactory capacitance of carbon nanomaterials is the main factor limiting the further development of carbon-based supercapacitors.This paper describes the research progress of electrode materials for energy storage devices in depth,and conducts the design,preparation,performance and application of transition metal cathode materials and carbon nanomaterials for aqueous energy storage devices.The main achievements are as follow:1.Oxygen defects were introduced into the Co₃O₄ nanosheets cathode to increase the conductivity and active sites,resulting in greatly enhanced electrochemical performance.Co₃O₄ nanosheets with abundant oxygen defects?R-Co₃O₄?were prepared by a simple hydrothermal method and then reduced by a solvent thermal method in ethylene glycol.The electrochemical performances of the R-Co₃O₄ cathode could be tuned by adjusting the reduction temperature and time in ethylene glycol.The optimized R-Co₃O₄ samples exhibited higher conductivity,larger surface area and more active sites than the pristine Co₃O₄ samples did.Consequently,the capacity of alkaline Zn/Co battery with R-Co₃O₄ as cathode achieved 240.8 mAh g^-1 at 2 mA cm^-2,accompanied by good rate performance and stability.2.Glucose-derived porous carbon nanoarchitecture was synthesized by a hydrothermal method using ZnO template and subsequent KOH activation?denoted as KZCC?,which functioned as advanced and durable electrode material for supercapacitors.Benefiting from its excellent conductivity,ultrahigh surface area,and porous architecture,the as-prepared KZCC delivered a high capacitance of 245.4 mF cm^-2 at a current density of 2 mA cm^-2 with impressiverate performance,much higher than the samples that prepared without ZnO template and KOH activation.Moreover,KZCC showed superior cycling durability with more than 99%capacitance retention after 10000 cycles.