Study On Honeycomb-like Porous Carbon Composite Electrode Materials Based On Doping And Their Assembling Aqueous Zn|MnO₂ Secondary Batteries

With the increasing demand for portable energy storage and conversion devices,aqueous rechargeable Zn|Mn O₂ battery has a unique application prospect among many energy storage devices due to its advantages of low price,environmental friendliness,safety and high efficiency.But,the application of cathode material Mn O₂ is limited by its inherent shortcomings such as poor conductivity,easy dissolution when using and easy collapse of crystal structure,which affect the performance of Zn|Mn O₂ battery.In addition,dendrite,side reaction and other problems in the process of charge/discharge of commercial zinc sheet affect the safety and charge/discharge efficiency.In this dissertation,the nano multistage structure materials of Mn O₂ or Zn are grown in situ honeycomb porous carbon,and their favorable effects in structure and morphology are used to construct composite cathode and anode materials of high-performance zinc ion batteries,so as to solve or alleviate the above problems.The specific research contents of this dissertation are as follows:（1）Preparation of honeycomb porous carbon supported manganese dioxide nanosheet composite and and their performances in Zinc ion battery:In order to construct high capacity and stability of cathode materials of zinc ion battery.In this dissertation,a three-dimensional porous honeycomb carbon material was constructed by controlling the calcination of freeze-dried carbon and nitrogen precursors,and it was used as the substrate to grow small size ZIF8 particles distributing uniformly.After roasting,a new Zn-N modified carbon material（ZIF8/HPC）was obtained.Both of these two carbon materials could be used as the reducing agent materials for in-situ growth of ultra-thin Mn O₂ nanosheets.Mn O₂/HPC and Mn O₂/ZIF8/HPC cathode materials with uniform distribution and controllable size are synthesized by optimizing and controlling the reaction conditions.The results show that:The battery assembled with Mn O₂/HPC retains the capacity of 127.4 m Ah/g after 4500cycles at high current density.The capacitance contribution reached to 81.9%.The battery assembled by Mn O₂/ZIF8/HPC can also reach the capacity of136.5 m Ah/g at 2 A/g;Capacitance contribution reached to 86.0%.In this work,the conductive substrate of three-dimensional porous honeycomb carbon material is designed to enhance the electrical conductivity of the composite material,accelerate the electron transfer on the small size ultra-thin Mn O₂ nanosheet,and improve the reaction efficiency.Mesoporous and macroporous structures of HPC help to accommodate Zn sources,generate additional pseudocapacitive charge storage.Meanwhile,it accelerates the diffusion rate of Zn ions and improves the mass transfer effect of the full battery.（2）Preparation of 3D honeycomb porous carbon composite materials based on zinc element doping modification and their application as anodes of Zinc ion battery:In order to solve the problems of dendrite and side reactions of zinc anode,this work selects Zn-doped porous honeycomb carbon material(Zn_{1.5 g}-HPC)and the carbon materials with honeycomb carbon material as the base with ZIF8 particles uniform loading and after roasting to obtain（ZIF8/HPC-600）,these two kinds of carbon materials as the host to electrodeposed is used to construct zinc anode.By modulating the zincophilic properties of the composite,the nucleation overpotential of zinc was greatly reduce,thus the reversibility of zinc deposition/dissolution was improved.The prepared Zn_{1.5 g}-HPC was tested for zinc deposition/dissolution.After 100cycles,it still maintained high coulombic efficiency（99.08%）and low polarization voltage difference（82.4 m V）.The prepared Zn/ZIF8/HPC was tested for zinc deposition/dissolution.After 200 cycles,it still maintained high coulombic efficiency（99.18%）and low polarization voltage difference（46.1m V）.Assembled as symmetrical cells for testing,they had low voltage hysteresis and stable cycle performance under different current density and capacity,with cycle life more than 180 h.When coupled with Zn/ZIF8/HPC anode and Mn O₂/HPC cathode,the Zn|Mn O₂ full battery has excellent charge/discharge performance,and the specific capacity reaches 397.3 m Ah/g at 0.1 A/g.After 6000 cycles,the cell with excellent stability still maintained high reversible capacity and coulombic efficiency at a high current density of5 A/g.In this dissertation,the modified three-dimensional honeycomb porous carbon nanomaterial as an inducible zinc deposition site can make the zinc metal limit in the HPC holes uniform growth,significantly improve the reversibility and stability of the zinc anode,and inhibit the dendritic growth and side reactions of the zinc anode.This work can provide a new idea for the preparation of zinc anode with high stability.