The Formation/Decomposition Equilibrium of LiH and its Contribution on Anode Failure in Practical Lithium Metal Batteries

Discovering the underlying reason for Li anode failure is a critical step towards applications of lithium metal batteries (LMBs). In this work, we conduct deuterium-oxide (D2O) titration experiments in a novel on-line gas analysis mass spectrometry (MS) system, to determine the content of metallic Li and lithium hydride (LiH) in cycled Li anodes disassembled from practical LiCoO2/Li LMBs. The practical cell is comprised of ultrathin Li anode (50 mu m), high loading LiCoO2 (17 mg cm(-2), 2.805 mAh cm(-2)) and different formulated electrolytes. Our results suggest that the amount of LiH accumulation is negatively correlated with cyclability of practical LMBs. More importantly, we reveal a temperature sensitive equilibrium (Li + 1/2 H-2 LiH) governing formation and decomposition process of LiH at Li anode. We believe that the unusual understanding provided by this study will draw forth more insightful efforts to realize efficient Li protection and the ultimate applications of holy grail LMBs.

Automated summary

This study reveals a negative correlation between the accumulation of LiH and the cyclability of practical LMBs. Additionally, a temperature-sensitive equilibrium governing the formation and decomposition process of LiH at the Li anode is identified, providing important insights for efficient Li protection and the ultimate application of LMBs.