Enabling LiNO₃ in carbonate electrolytes by flame‐retardant electrolyte additive as a cosolvent for enhanced performance of lithium metal batteries

Abstract

Most contemporary liquid Li‐ion battery chemistries are based on carbonate electrolytes, however, these typically perform poorly with metallic lithium. Especially, when only a small reservoir of metal is present, cells fail quickly due to the complete consumption of electrochemically active Li. Electrolyte modification is, therefore, a commonly chosen strategy to increase cycling stability and prolong lifetime of the cell. At the same time, complete redevelopment of an electrolyte usually creates a new set of problems, as conductivity, suitable electrochemical stability window and compatibility to all components of the cell needs to be ensured. It is, therefore, a reasonable strategy to alter existing electrolytes slightly, as has been done for the aforementioned carbonate electrolytes by incorporating lithium nitrate salt with triethyl phosphate as cosolvent into the mixture. As the role of the organophosphate is not fully clarified, our study aims to investigate its effect onto cycling stability, morphology, and reversibility of Li metal cycling both with and without LiNO3 salt. Using close‐to‐industrial conditions with limited excess of metallic Li at high current density, we are comparing cycling performance of the different electrolyte combinations. Contribution of the additive components to irreversible thickness growth due to the formation of inactive (“dead”) lithium and deposited lithium morphology is investigated by operando dilatometry and postmortem scanning electron microscopy. Finally, we are looking at modified solvent‐salt ratios to see whether further improvements of cell lifetime and morphology can be achieved.

Lithium-Ion Charged Polymer Channels Flattening Lithium Metal Anode

“…Previous studies reported that lithium nitrate (LiNO 3 ) as electrolyte additive was a valid path to strengthen the interface stability for dendrite suppression [ 22 , 23 ]. The LiNO 3 has been proved to be critical electrolyte additive for Li–S batteries in restraining the “shuttle effect” of lithium polysulfides and improving interfacial stability of Li metal anode [ 29 – 32 ]. The NO 3 − will degrade into Li + conductors, Li 3 N and LiN x O y , which are beneficial for Li plating/stripping behavior [ 33 , 34 ].…”

Artificial Li3N SEI-Enforced Stable Cycling of Li Powder Composite Anode in Carbonate Electrolytes

“…Several researchers have focused on strategies to improve the solubility of LiNO 3 in carbonate electrolytes. [29][30][31][32][33][34][35][36] Other approaches, including plasma activation, sputtering, coating, and printing, among others, aimed at pre-forming a Li 3 N layer on the surface of Li foil prior to cycling, have also been explored. [37][38][39][40][41][42][43][44][45][46] Zhu et al 45 reported a thin Li composite anode based on an AlN-embedded reduced graphene oxide (rGO) scaffold via one-step molten Li infusion.…”