Fabrication Of Aqueous Lithium Ion Battery Anode Materials Based On NiCo Nanocomposite

Aqueous lithium ion battery is superior to the organic system in terms of saving cost and battery safety.Aqueous lithium ion battery has rapid electrochemical kinetics which benefits from good ion conductivity.However,the narrow electrochemical window has limited the application of aqueous lithium ion battery due to the decomposition of water,which is also an urgent challenge in the research of aqueous lithium-ion batteries.The ultrahigh concentrated lithium trifluoromethanesulfonate imide（Li TFSI）is used as aqueous electrolyte to widen the electrochemical window of the aqueous lithium ion battery and enhance the stability of the battery.In addition,high concentration of TFSI^-can form a SEI film on the surface of anode,which can protect the electrode.As a transition alloy material,NiCo is easy to prepare and modify surface morphology and microstructure,which can expose more surface defects and reactive active sites to improve electrochemical performance.Design stable morphology of NiCo structure is also conducive to improving mechanical stability.Based on the above background,this paper studies and designs a series of NiCo to be hollow,core shell,double shell,and 3D porous foam anode materials,analyzes their micro morphology,and evaluates the electrochemical and battery performance of these NiCo materials.The main research content is as follows:Firstly,we prepared hollow Co₃O₄/NiCo₂O₄ conductive networks by hydrothermal and solution precipitation methods,and studied their electrochemical and battery performance.NiCo precursor nanorods have constructed a conductive network,they can provide channels for electron transmission and supporting hollow Co₃O₄ to improve the conductivity and stability of the composite material.The hollow Co₃O₄ nanocrystals were prepared by using ZIF-67 as a sacrificial template,which can provide more reactive active site for the composite materials,and this structure is also benefit for the process of Li⁺insertion and deinsertion.The experiment evaluated the battery performance of Co₃O₄ and NiCo₂O₄ at different mass ratios,and we found that the Co₃O₄/NiCo₂O₄=1:6（CN-6）full battery had the best battery performance.When the charge and discharge current density was 0.5 C,it could provide 93.1 Wh kg^-1 energy density and 91.04%capacity retention rate.This battery has important application value in the direction of new energy devices for high-energy batteries.Secondly,through the analysis and summary the properties of the Co₃O₄/NiCo₂O₄ anode material,we hope to improve the stability of NiCo materials and enhance the long-range cycling ability of batteries.In this chapter,we design a sea urchin like NiCo₂O₄/NiCo core-shell anode material and explores its battery performance.A core-shell structure anode material with NiCo₂O₄ core and Ni Mn shell was constructed using hydrothermal method and solution precipitation method.The design of the core-shell structure can provide a large porosity for the composite materials,which is conducive to the substance transfer during the battery charging and discharging cycle for promoting the electrochemical kinetics.This chapter explores the effect of Ni Mn on battery performance under different coverage thicknesses.The results show that when the mass ratio of NiCo₂O₄ to Ni Mn is 3:1（NiCo₂O₄/Ni Mn（3:1））,the as-prepared battery can carry out for 100 at 0.3 C.The discharge specific capacity of the full battery is 51.2 m Ah g^-1,and the capacity retention rate is 87.5%.This battery has excellent capacity retention and cycle life,which providing a novel preparation idea for the future preparation of large long-life power supply devices.Thirdly,the as-prepared NiCo₂O₄/Ni Mn core-shell anode materials provide good cycling ability for batteries.Based on this study,we want to pursue a battery which can balances battery capacity and cycling life.We prepared NiCo₂S₄ double-layer shell microspheres using a two-step hydrothermal method.Using NiCo microspheres as precursors and thioacetamide（TAA）as sulfur sources,a double shell structure of NiCo₂S₄microspheres was formed through ion exchange reaction between S^2-and Ni²⁺(Co²⁺).There is a gap between the core and shell of NiCo₂S₄ microspheres,which has a hollow characteristic.As a double-layer shell structure,the core inside the microspheres can provide support for the outer layer material and enhance mechanical stability to improve the cycling life of batteries.NiCo₂S₄with reaction time of 6 h,a TTA addition of 50 mg（NiCo₂S₄-6）exhibits the most perfect double shell structure.At 0.3 C,the NiCo₂S₄-6 battery can achieve a discharge specific capacity of 120 m Ah g^-1 with a high capacity retention rate after 100 cycles.This battery not only ensures cycle life and capacity retention rate,but also improves the battery capacity,which has important reference value for the future practical application of aqueous lithium-ion batteries.Fourthly,based on the experimental research on the micro regulation of NiCo previously researched,we used micro-and nano-materials（such as NiCo,MXene and GO）as basic units to fabricate 3D porous foam through self-assembly,and explore its battery performance.3D porous foam was constructed by self-assembly of micro nanomaterials of NiCo,MXene and GO,and then we explored their battery performance.MXene@NiCo/rGO foam has very large specific surface area and porosity,which is conducive to substance and electron transfer.GO skeleton can stabilize single layer MXene to improve battery performance and enhance composite material stability.MXene@NiCo/rGO can provide a discharge specific capacity of 60 m Ah g^-1 at 0.3 C,and the capacity retention rate of the battery is 99%after 100 cycles.The full battery assembled in this chapter endows the battery with excellent capacity retention rate by constructing a new 3D structure anode material,which providing new ideas for subsequent anode material design and has a crucial reference value.