Sustained Release of AgNO3 Additive in Carbonate Electrolytes for Stable Lithium Metal Anodes

Abstract

With increasing energy storage demand, research on high energy density and stable battery became essential. Among different anode materials for lithium batteries, lithium metal is an ideal anode material as it has low redox potential and high specific capacity. Therefore, for post-lithium ion battery with high energy density cannot avoid using lithium metal as an anode. However, lithium metal anode has stability and safety issues due to dendritic growth. Lithium metal in contact with organic electrolyte reacts with the electrolyte to form solid electrolyte interface (SEI). SEI prevents further electrolyte consumption, however presence of unstable SEI causes uneven lithium ion diffusion through the SEI layer and induces lithium dendrite growth. Therefore, uniform deposition of lithium and stable SEI is important to operate lithium metal anode safely.The application of nitrate additives in carbonate electrolyte has been very limited due to poor solubility. However, nitrate containing polymer interlayer can release additive constantly enabling nitrate act as an electrolyte additive. Herein, AgNO3 synthesized with PAN nanofibers (AgPAN) is used as an additive to induce uniform lithium deposition and stable SEI formation. In the symmetric cell test, life time of 20 µm thick lithium foil enhanced from 140 hr to 300 hr with AgPAN. Lithium nucleation overpotential disappeared and overall overpotential is reduced. Originally, plane lithium foil had the sparsely deposited dendrite shaped lithium, but with AgPAN lithium was evenly deposited and grow in spherical shape. Ag+ reduces on lithium metal surface acting as a lithium nucleation seed helping uniform lithium deposition and NO3 - reacts with lithium to form stable inorganic SEI layer (Li2O, Li3N, LiNxOy, and etc) resulting in stable cycling of lithium metal anode.