Diagnostic Protocols for Evaluating the Degradation Mechanisms in Gel-Polymer Lithium Batteries

Gel polymer electrolytes (GPEs) present a promising alternative to standard liquid electrolytes (LE) for Lithium-ion Batteries (LIBs) and Lithium Metal Batteries bridging the advantages of both liquid and solid polymer electrolytes. However, their cycle life still lags behind that of standard LIBs, and their degradation mechanisms remain poorly understood. A significant challenge is the need for specific diagnostic protocols to systematically study the degradation mechanisms of GPE-based cells. Challenges include the separation of cell components and effective washing, as well as the study of the solid electrolyte interfaces, all complicated by the semi-solid nature of GPEs. This paper provides a brief review of existing literature and proposes a comprehensive set of diagnostic tools for dismantling and evaluating the degradation of GPE-based LIBs. Finally, these methods and recommendations are applied to LiNi0.5Mn1.5O4 (LNMO)-graphite cells, revealing electrolyte oxidation as a major source of cell degradation. The study presents diagnostic protocols for evaluating degradation mechanisms in gel-polymer electrolyte (GPE) lithium-ion batteries. Washing procedures, liquid electrolyte fractions via TGA, and parasitic reactions using solution-state NMR and GC-MS are examined. Structural and compositional analyses are performed with XRD, Raman spectroscopy, FTIR, ssNMR, ICP-AES, EDX and SEM, offering a comprehensive evaluation of GPE-based cells. image