Dehydrating A Borate Additive Unlocks Fast‐Charging Graphite

ABSTRACT

Graphite anodes dominate commercial lithium‐ion batteries (LIBs), yet fast charging is limited by interfacial polarization that drives resistive SEI growth and lithium plating. Borate additives such as lithium bis(oxalato)borate (LiBOB) can boost rate performance, but often produce thick, resistive interphases and gas‐induced swelling in practical cells; nevertheless, they are still used because comparable, manufacturable alternatives remain scarce‐highlighting the urgency for new interphase chemistries. Here, an anhydrous lithium bis(catecholato)borate (LiBCB) additive is enabled by a one‐step non‐aqueous synthesis that eliminates water of crystallization, an often‐overlooked factor that can obscure intrinsic interphase function. LiBCB first enriches at the graphite surface via preferential adsorption and then undergoes interfacial reduction to form a thin, compact, ionically conductive SEI, thereby reducing polarization, delaying sub‐0 V plating, and suppressing dead‐lithium accumulation. In 1.7 Ah graphite||LiFePO ₄ pouch full cells, 2 wt.% LiBCB retains 92% of initial capacity after 1000 cycles at 2.6 A with the smallest pouch‐volume change among the tested electrolytes, vastly outperforming the base electrolyte (13% rentention). These results identify salt form (hydration state and purity) as a decisive variable in SEI engineering and position anhydrous LiBCB as a practical alternative to LiBOB for fast‐charging graphite‐based batteries.