Amorphous silicon nitride induced high dielectric constant toward long-life solid lithium metal battery

Abstract

Solid polymer electrolytes are the most promising solid electrolytes due to their mechanical flexibility and manufacturing scalability. However, the low lithium-ion transference number and battery failure with detrimental dendrites growth inhibit its commercial application in solid-state batteries. Here amorphous silicon nitride with high permittivity was introduced to both restrain the anion motion and screen the electric potential under external electric field, by which the lithium-ion transference number was improved and the dendrite growth was inhibited significantly. The symmetric Li//Li cell paired with this solid polymer electrolyte exhibits a high lithium-ion transference number of 0.53, with excellent lithium plating/stripping capability at high current density of 1.0 mA cm −2 over 250 h at room temperature. The practical application of this solid polymer electrolyte is verified by the capacity retention of 86.5% over 500 cycles and 70.5% even after 1000 cycles at room temperature with Li//LiFePO 4 pouch cell at 1C. The fire retardant of this solid polymer electrolyte is demonstrated by an excellent self-extinguish behavior (<1 seconds) in the flame test. Additionally, this solid polymer electrolyte system presents an effective strategy for enhancing anode interfacial stability for other battery systems. Amorphous silicon nitride with high dielectric constant enhances the uniform lithium electrodeposition by screening electric potential at high current density. The reduction product from the in-situ reaction between lithium anode and silicon nitride is beneficial to interfacial chemistry, especially the in-situ formed LiSi 2 N 3 shows a better Li + migration pathway across the inorganic-rich SEI layer.