Electrolyte-Mediated Misconception of Carbon-Based Electrode Performance and Beyond in Metal-Ion Batteries

摘要

A half-cell that is composed of electrode and metal (e.g., lithium) is the mostclassical model for examining electrode performance in battery community, bywhich the voltage versus capacity profile is the important indicator. However,it is found that these results are not all reliable, as a misconception ofelectrode performance can be caused once the electrolyte is chemicallyunstable. As a paradigm, it is demonstrated that the diethyl carbonate (DEC)solvent can chemically react with lithium metal to form insoluble and solubleby-products, which can accumulate on the lithium anode to influence thelithium potential and/or migrate to the counter electrode to proceed with theuncompleted electrochemical reactions. The resultant voltage-capacity profilecannot reflect the actual electrode performance, such as the lithium storingcapability within the graphite. The reason for this phenomenon is elucidatedbased on solvation chemistry, particularly the mechanism of mitigating it byintroducing ethylene carbonatesolvent to form new hydrogen bonds. Theviewpoint is further verified by employing the full cell and also extended insodium and potassium batteries. This study shows the necessity of discerningthe reliability of electrode performance and also sheds light on the importanceof designing a compatible electrolyte to examine electrode performance.