Enhancing Interfacial Reaction Rates in Extremely Fast Charging Li-Ion Batteries Using Linear Carbonate-Based, High-Concentration LiPF₆ Electrolytes

With the growing reliance on battery-operated vehicles, addressing the safety concerns associated with lithium plating, exacerbated by high cell polarization during extremely fast charging (XFC) of Li-ion batteries, becomes imperative. This research probes into the effects of Li⁺ desolvation and the solid-electrolyte interphase (SEI) chemistry on cell polarizations through the use of linear carbonate (LC)-based, high-concentration LiPF₆ electrolytes (LPCEs). Within the LC group, dimethyl carbonate (DMC) is identified as the most thermodynamically favorable for enhancing desolvation kinetics, thus reducing the charge-transfer resistance at the graphite anode. To facilitate effective graphite passivation and accelerated Li⁺ transport through the SEI, fluoroethylene carbonate (FEC) is employed to form a thin, fluorinated SEI layer. This enhances the XFC cycling stability in graphite||NMC622 full cells (3.0 mAh cm⁻²; N/P ratio = 1.1), achieving a remarkable 94.3% capacity retention after 500 cycles under a 10-minute charging regime. Compared to traditional electrolytes, the excellent XFC performance is further substantiated in a practical 1.2-Ah pouch cell, showcasing a tripling in capacity retention over 200 cycles and effectively mitigating Li plating-induced cell swelling. Unraveling the intricate mechanisms of cell polarization, as dictated by the electrolyte chemistry, furnishes pivotal insights for developing future electrolyte designs for XFC capabilities of Li-ion batteries.