Preparation Of Transition Metal Compounds And Carbon Composites And Their Application In Aqueous Zinc Batteries

Due to the depletion of reserves and serious environmental pollution caused by the overuse of global fossil fuels,people are devoted to developing chemical energy storage devices with strong portability and high conversion efficiency.Among them,alkaline aqueous zinc-based batteries stand out from all kinds of batteries due to their high theoretical capacity,low cost and high safety.However,the traditional alkaline aqueous zinc-based battery cathode materials have problems such as low capacity,low electrical conductivity and Insufficient stability.In order to solve the above problems,researchers focus on the development of new cathode materials,among which transition metal compounds and carbon composites have received extensive attention in the field of aqueous zinc batteries due to their good electrical conductivity and high capacity.This paper focuses on the construction of transition metal compounds and carbon composites to carried out aseries of work including synthesis of electrode materials with desirable morphology and structure,rational design and construction of electrode architectures,and synthesis of metal oxide and carbon nanofibers.The details are discussed as below:（1）Bimetallic NiCo-MOF spheres are synthesized via a solvothermal method,and then annealed in air atmosphere to successfully prepare NiCo₂O₄hollow multi-shell spheres（denoted as NiCo₂O₄-HMSs）as the cathode of alkaline aqueous Zn-based battery.Benefiting from the unique structure of NiCo₂O₄-HMSs,the NiCo₂O₄-HMSs//Zn batteries exhibit high capacity of 152.8 mAhg^-1at 2 A g^-1,even at at a high rate of 10.0 A g^-1,the capacity is still as high as 103.7 mAhg^-1.Meanwhile,the excellent structural stability of NiCo₂O₄-HMSs can still maintain 86.5%capacity after 500 cycles.What’s more,the energy and power densities of NiCo₂O₄-HMSs//Zn batteries can reach up to 264.3 W h kg^-1and 24.7 kW kg^-1.（2）Through an innovative combination of MOFs-derived strategy and electrospinning technique,NiCo₂S₄nanoparticles and hollow carbon hybrid spheres compactly concatenated by carbon fibers（denoted as NiCo₂S₄/HCS@CFs）were synthesized.The as-synthesized film offers multilevel advantages including high electrical conductivity,abundant electroactive sites,fast ion diffusion,facile electrolyte permeability and robust structure stability.When NiCo₂S₄/HCS@CFs evaluated as self-standing cathode electrodes,as expect,the resulting NiCo₂S₄/HCS@CFs//Zn batteries exhibit an extreme high capacity of 343.1 mAhg^-1at a current density of 3.8 A g^-1（based on the NiCo₂S₄active material）,as well as superior rate performance and decent cycling performance.Meanwhile,the weight/volume energy densities of the quasi-solid NiCo₂S₄/HCS@CFs//Zn batteries are as high as 504.1 Wh kg^-1and 43.9 mWhcm^-3,respectively.