Study On PEO-based Solid Electrolyte Modified By Atomic Layer Deposition

The continuous development of science and technology has brought a lot of convenience to people’s lives,but at the same time when a lot of natural resources are consumed,it also inevitably causes the destruction of the environment.As a zero-emission energy device,lithium-ion batteries gradually replace nickel-cadmium batteries and lead-acid batteries as the mainstream products in energy storage devices because of their excellent performance and environmental friendliness,thus they have also attracted the attention of researchers.At present,in addition to the portable electronic equipment power supplies which have already been applied,lithium ion batteries are also widely used in the power output of electric vehicles and are gradually being applied in our life and industrial production.However,the use of liquid electrolytes has outstanding safety issues,such as burning,explosions,etc.,which limited the further development of lithium-ion batteries.In this paper,the using of atomic layer deposition to coat dopant is studied to obtain a solid polymer electrolyte with high safety and excellent performance.The content of this article mainly includes:（1）Using self-built atomic layer deposition（ALD）equipment,prepare tert-butoxide lithium as the lithium source and trimethyl phosphate as the phosphorus source,a layer of 100 cycle’s Li3PO4 electrolyte was coated on the titanium dioxide nanoparticles at300°C.And then It was doped into a polymer electrolyte with PEO and LITFSI as the matrix,mixed and vacuum dried and demolded to obtain a solid electrolyte with high ionic conductivity.The structure of the composite electrolyte was further characterized by transmission electron microscopy（TEM）,scanning electron microscopy（SEM）and X-ray diffraction（XRD）.The impedance and changes in ionic conductivity was measured by AC impedance spectroscopy.It was found that the recrystallization process of the nanoparticle-doped electrolyte was limited,and the successful encapsulation of Li3PO4 was confirmed by EDS element mapping.Combined with the measurement results of the electrochemical workstation,it was found that the ionic conductivity of the electrolyte doped with 5%TiO2@Li3PO4 reached 6.53×10-⁴S/cm at 80°C.Compared with the undoped polymer electrolyte,the ion conductivity increased by an order of magnitude under the premise of maintaining flexibility.Compared with the uncoated nanoparticles,the ionic conductivity is also greatly improved,which shows that coating the doped particles by ALD does contribute to the improvement of the ionic conductivity of the composite polymer electrolyte.（2）Using the purchased TiO₂ nanowires as raw materials,the same 100 cycle Li₃PO₄electrolyte was coated by atomic layer deposition,and then it was doped into the polymer electrolyte using the same preparation method as the nanoparticle doped electrolyte to acquire a composite polymer electrolyte.The morphologies and structures of the samples were characterized by TEM,EDX and SEM.It was found that the nanowires were successfully coated with a layer of Li₃PO₄ electrolyte and distributed evenly in the electrolyte.XRD results showed that the degree of crystallinity before and after doping changed little,indicating that doped nanowires have a limited inhibitory effect on the recrystallization process of high molecular polymers.Combined with electrochemical workstation measurement data,it was found that the ionic conductivity increased to some extent compared to the undoped and uncoated electrolytes,and the ionic conductivity could be achieved 2.47×10^-4S/cm at 80°C.The effect of different morphologies of the same kind dopant on the ionic conductivity is revealed.The nanoparticle has a better inhibition effect on the recrystallization process,so that the ionic conductivity after doping is higher,and after the introduction of the atomic layer deposition coating,the ionic conductivity of the dopants had increased,indicating that the surface modification by atomic layer deposition artificially introduces new lithium ion migration sites.