Solid-state Sodium Metal Batteries Based On Silicate Zirconium Phosphate Sodium Solid Electrolyte

As a new type of high energy density battery,sodium metal batteries have attracted much attention because of their relatively low preparation cost.Similar to lithium metal batteries,sodium metal batteries also have safety hazards such as electrolyte volatilization and leakage,sodium dendrite growth,battery combustion and even explosion.In current research,solid-state batteries rely on their good ionic conductivity,high mechanical strength,and are the main research direction for next generation Organic-inorganic composite electrolytes are effective in improving the interface between electrode and electrolyte and increasing the ionic conductivity,which can meet the need of energy density of most batteries.To explore the effect of ionic conductor powder on polymer electrolytes,organic-inorganic composite electrolytes with ionic conductivity up to 0.9 m S cm^-1,were prepared using Na₃Zr₂Si₂PO₁₂ with PVDF-HFP.The solid sodium metal battery prepared with composite electrolyte,Na metal negative electrode and Na₃V₂（PO₄）₃-C cathode has a discharge capacity of 48.6 m Ah g^-1 at a current density of 100 m A g^-1.After 95 cycles,the battery discharge capacity can still be maintained at 96.6%and the coulombic efficiency is close to 100%.In order to reduce the use cost of sodium anode and lower the local current density,Ti₃C₂T_x was used to compound with sodium metal.The composite anode is 46%thinner than the pure sodium metal anode,which reduces the cost of using sodium metal anode and the nucleation overpotential is much lower than that of the pure sodium anode.To improve the interfacial contact,PVDF-HFP and Na₃Zr₂Si₂PO₁₂ were used to modify the polyimide film（PI）,which improved its mechanical strength and sodium ion migration ability.The sodium battery with composite sodium metal anode and PVDF-HFP-Na₃Zr₂Si₂PO₁₂modified polyimide film has a specific discharge capacity of 87.9 m Ah g^-1 after500 cycles,with a capacity retention rate close to 100%.To alleviate the sulfur shuttle effect of sodium-sulfur batteries,the ionic conductivity of the solid electrolyte was enhanced and the contact between electrode and electrolyte was improved.A structure with dense middle and porous sides was creatively designed to prepare the integrated electrolyte.Carbon nanotubes were deposited in the porous structure by chemical vapor deposition to enhance the conductivity of sulfur at low temperatures.The ionic conductivity of the aluminum ion-doped Na_3.5Zr_1.9Al_0.1Si_2.4P_0.6O₁₂ reached 4.43m S cm^-1 at 50^oC.The polarization voltage of the Na||Na symmetric cell was about 40 m V after cycling for more than 1600 h.Its specific discharge capacity was maintained at 300 m Ah g^-1 after 480 cycles at 300 m A g^-1.Finally,in order to address the current situation that the energy density of the battery is still insufficient,we used magnesium-doped Na_3.2Zr_1.9Mg_0.1Si₂PO₁₂ as a filler in the electrolyte of the Na-CO₂ battery in the context of"carbon neutral,carbon peaking"and effectively utilized greenhouse gases as raw materials.The solid-state Na-CO₂ battery assembled using the composite electrolyte showed a discharge specific capacity of 7720 m Ah g^-1 at200 m A g^-1.In general,this paper takes the preparation of low-cost,high-safety,high specific capacity sodium battery as a guideline,based on solid electrolyte,through organic-inorganic composite,doping modification,etc.,the ionic conductivity and interfacial wettability of the solid electrolyte are improved,and the designed composite negative electrode and integrated ceramic electrolyte reduce the cost of using electrodes and improve the safety of the battery;the prepared sodium-CO₂ battery is useful for The prepared sodium-CO₂battery presents a new idea for carbon dioxide fixation,energy storage.This thesis provides a possible solution for sodium batteries as the core of large-scale energy storage.