Interface Modification Of Nickel/Cobalt-based Electrode Materials And Study On The Performance Of Zinc Ion Batteries

In the world today,environmental problems caused by the extraction and consumption of fossil fuels such as coal,petroleum,and natural gas are be,human society is facing the dilemma of fishing after exhaustion.In order to get rid of the heavy dependence on non-renewable energy,it is critical to create cleaner,greener energy sources to meet the global energy needs.Simultaneously,the energy storage and conversion method are vital,and researchers have long been dedicated to the study and development of efficient and sustainable advanced energy storage systems.Water-based zinc ion batteries have many significant advantages,such as low cost,good safety,harmlessness,and high power density.As a crucial component,cathode materials have always had an impact on the energy density,cycle stability,and other performance indicators of the zinc ion battery,and have become a bottleneck constraining the applications of high-performance batteries.Because of their superior physical and chemical properties,nickel/cobalt-based composites are widely used in energy storage devices such as lithium-ion batteries,supercapacitors and so on.However,there are few reports in the research of cathode materials for water-based zinc ion batteries.This thesis takes nickel/cobalt-based materials as the research objects,and uses interface modification and doping modification methods to improve its electrochemical performance,promoting the development of high-performance water-based zinc ion batteries.The specific works are as follows:(1)Synthesis of CoO/Ni₂P-Co₂P nanosheet arrays and its application in zinc ion batteries:Based on interface reconstruction and defect chemistry modification strategies,CoO/Ni₂P-Co₂P nanosheet arrays were synthesized by etching deposition and partial phosphating methods.Moreover,by adjusting the etching time and phosphating time to further screen the best CoO/Ni₂P-Co₂P product.In CoO/Ni₂P-Co₂P nanosheets,the heterogeneous interfaces between different components become fast channels for charge transfer,a large number of introduced electrons near oxygen defects are excited to form new conduction bands to promote carrier migration.Abundant active surface provides sufficient redox reaction sites.The electrochemical test results show that at a current density of 3 A g^-1,the specific capacity of CoO/Ni₂P-Co₂P-30 is as high as 370.4 m A h g^-1,and when the current density is increased six times to 18 A g^-1,63.3%of its initial capacity is maintained,showing outstanding specific capacities and superior rate performance.The CoO/Ni₂P-Co₂P//Zn battery was assembled with a nickel foam substrate loaded with CoO/Ni₂P-Co₂P as the cathode and a piece of commercial zinc foil as the anode.The test results show that the battery achieves a superior energy density of 547.5 W h kg^-1 at a power density of 9.7 k W kg^-1.After 8000 cycles of CoO/Ni₂P-Co₂P//Zn battery,104.9%of its initial specific capacity can be maintained.(2)Synthesis of P-Ni_0.5Co_0.5Se₂ nanosheet arrays and its application in zinc ion batteries:P-Ni_0.5Co_0.5Se₂ nanosheet arrays were synthesized by the strategy of selenization interface reconstruction and phosphorus doping modification.The selenization method of vapor deposition transforms the oxide into porous Ni_0.5Co_0.5Se₂ nanosheet arrays with higher conductivity.The phosphorus doping process substitutes part of the selenium atoms and changes the coordination structure and electrons configuration of Ni_0.5Co_0.5Se₂.It also strengthens the interface properties of Ni_0.5Co_0.5Se₂ itself,and improves its structural stability.The characterization results of electrochemical performance indicate that,at the current density of 8 A g^-1,the specific capacity of P-Ni_0.5Co_0.5Se₂ reaches 305.3 m A h g^-1,and the capacity can still reach 237.3 m A h g^-1 at an ultra-high rate of 32 A g^-1,which proves the superior rate performance of P-Ni_0.5Co_0.5Se₂ and its universality under high current density.A P-Ni_0.5Co_0.5Se₂//Zn battery was assembled with carbon paper loaded with P-Ni_0.5Co_0.5Se₂ nanosheet arrays as the cathode and a piece of commercial zinc foil as the anode.The test results show that the energy density and power density of the battery were respectively up to 397.8 W h kg^-1 and 16.4 k W kg^-1,after 7000 cycles,109%of the initial capacity is still maintained,proving its excellent cycle stability.