Synthesis And Electrochemical Performance Of Sodium Ion Solid Electrolyte

Large-scale energy storage systems require low-cost,high-safety and long-life energy storage devices.sodium-ion batteries have received extensive attention due to the abundance resources,low cost and uniform distribution of sodium.Solid electrolytes can effectively avoid the combustion and explosion of Na-ion batteries based on organic electrolyte.Therefore,solid-state sodium-ion batteries have received widespread attention in recent years.How to improve the conductivity of solid electrolytes and the compatibility of electrodes and electrolytes restrict the development of solid-state sodium-ion batteries.NASICON-type electrolytes with high ionic conductivity and good chemical/mechanical stability have broad application prospects.This paper mainly focuses on doping and interface modification of Na₃Hf₂Si₂PO₁₂.The main research contents include:The low ionic conductivity of Na₃Hf₂Si₂PO₁₂at room temperature is solved by Ca²⁺doping.Na_3+2xHf_2-xCa_xSi₂PO₁₂（x=0、0.05、0.1、0.15、0.2、0.25）is prepared by doping with Ca at Hf site.Ca²⁺with a larger ionic radius can expand the size of the sodium ion channel,which is beneficial to the transport of Na⁺and improve the ionic conductivity.The poor wettability and excessive interfacial resistance between sodium metal and Na_3.2Hf_1.9Ca_0.1Si₂PO₁₂were regulated by SnO₂modification.In situ reaction between Na and SnO₂occurs to form Na-Sn alloy,which improves interfacial contact and reduces interfacial resistance.The solid-state sodium-ion battery based on the SnO₂interlayer can be stably cycled for more than 2400 hours under current density of 0.1 mA·cm^-2.Electron blocking interlayer（Sn F₂+NaCl）was constructed to control the dendrite growth and side reactions between Na and Na_3.2Hf_1.9Ca_0.1Si₂PO₁₂.Sn F₂reacts with Na in situ to form Na-Sn alloy and Na F,which can increase the contact area,stabilize the ion transport and improve the interface stability.NaCl provides electronic insulation and directly inhibits the formation of sodium dendrites.The solid-state battery based on the electron blocking layer cycles for more than 700 hours under 0.2 mA·cm^-2,and the maximum current density can reach 2.3 mA·cm^-2.Figure 51;Table 5;Reference 66...