Data paper Exploring binder–ionic liquid electrolyte systems in silicon oxycarbide negative electrodes for lithium-ion batteries

Enhancing the safety of lithium-ion batteries (LIB) by replacing flammable electrolytes is a key challenge. This study investigates the electrochemical behavior of two newly synthesized ionic liquids (ILs) comparing them to conventional alkyl carbonate-based electrolytes. Nitrogen-doped carbon silicon oxycarbide (NC-SiOC) as the active material in negative electrodes was combined with two polymeric binders: poly(acrylic acid) (PAA) and poly(acrylonitrile) (PAN). NC-SiOC/PAN electrodes exhibited a significantly higher initial charge capacity—approximately 25–30% greater than their PAA-based counter-parts in the first cycle at 0.1 A g⁻¹ (850–990 mAh g⁻¹ vs. 600–700 mAh g⁻¹), and demon-strated an improved initial Coulombic efficiency (67% vs. 62%). Long-term cycling sta-bility over 1000 cycles at 1.6 A g⁻¹ retained 75–80% of the initial 0.1 A g⁻¹ capacity. This outstanding performance is attributed to the synergistic effects of nitrogen-rich carbo-naceous phases within the NC-SiOC material and the cyclized-PAN binder, which fa-cilitate structural stability by accommodating volumetric changes and enhancing solid electrolyte interphase (SEI) stability. Notably, despite the lower ionic transport properties of the IL electrolytes, their incorporation did not compromise performance, supporting their feasibility as safer electrolyte alternatives. These findings offer one of the most promising electrochemical performances reported for SiOC materials to date.