Influence of the Electrolyte Amount on the Aging Behavior of 4695 Lithium-Ion Batteries

Vollständiger Abstract

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Abstract This study investigates the effect of varying electrolyte amounts on the aging behavior of lithium-ion batteries using 4695 cells containing a high-nickel NMC cathode and a graphite-silicon composite anode. Eight pore filling ratios (PFRs), ranging from approximately half-filled pores to fully saturated pores with additional free electrolyte, are examined. All cells undergo 720 cycles of accelerated aging between 0% and 80% state of charge at 50 °C with a C-rate of 0.5C. Despite significant differences in electrolyte amount, all cells exhibit remarkably similar capacity fade and resistance increase during cyclic aging. However, subsequent fast charging tests reveal that cells with very low or high PFRs show rapid capacity loss and increased resistance due to lithium plating. For high PFRs, this is attributed to electrolyte motion induced salt inhomogeneity (EMSI), while for low PFRs, increased capacity loss results from higher initial and aging-induced resistance caused by incomplete electrode wetting. In contrast, cells with intermediate PFRs demonstrate stable fast charging performance. Furthermore, moment of inertia measurements were applied for the first time to monitor the evolution of electrolyte amount during cycle life. These findings emphasize the significant influence of aging conditions on the optimal electrolyte amount for ensuring long-term battery durability.