Degradation Analysis and Thermal Behavior of Ni‐Rich Cathodes at High Cutoff Voltages With Fluorine‐Free Electrolytes
Year: 2026
Type: article
Abstract: Nickel-rich layered cathodes, LiNixMnyCo₁₋ₓ₋ᵧO₂ (NMC) are promising materials for next-generation Li-ion batteries due to their high energy/power densities and long cycle life, however, capacity fading remains a major limitation. While fluorinated electrolytes have enabled optimal performance, their environmental and safety issues prompt the investigation of fluorine-free alternatives. Here, we evaluate a fluorine-free electrolyte based on lithium bis(oxalato)borate in NMC811||Si–Graphite full cells operated at low and high cutoff voltages, comparing its performance with that of a LiPF₆-based electrolyte. The cathode–electrolyte reactions are the primary cause of capacity fade, leading to electrolyte decomposition, layer disorder, and irreversible phase transitions. Increasing the cutoff voltage and the use of a fluorine-free electrolyte exacerbate these reactions, resulting in more rapid capacity loss. Differential scanning calorimetry characterization of harvested electrodes from cycled cells with both electrolytes indicated that the anode limits the thermal stability at lower temperatures than the cathode, and it is higher for the fluorine-free electrolyte. Overall, the results indicate that the fluorine-free electrolyte performance is limited at high cutoff voltage by the cathode and highlights the need for improved CEI-based additives or cathode coatings to allow competitive performance of more environmentally friendly electrolytes with fluorine-free components.
Authors: Saeed Mardi, Emil Tronde, Guiomar Hernández
Institution: Uppsala University
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,910
OpenAlex ID: W7128960403