Abstract: Boron-doped carbon dots (B-CDs) synthesized via solid-phase method were employed as electrolyte additives for lithium metal batteries. The carbon dots were prepared through the catalytic pyrolysis of carbon sources in air, highlighting high yield, efficiency, safety, and convenience. Synthesized from 1,3,5-trihydroxy-benzen and boric acid, the B-CDs exhibited excellent dispersibility in carbonate-based electrolytes. The doped boron atoms, serving as electron-deficient centers, could engage fluorinated anion groups through Lewis acid-base interactions, thus inducing uniform lithium-ion deposition on the lithium anode. At an additive concentration of 0.3 mg mL-1, a lithium symmetric cell demonstrated stable cycling for 2500 hours under a current density of 0.5 mA cm-2 and a plating capacity of 0.5 mAh cm-2, indicating that the carbon dot additive significantly enhanced the reversibility of lithium deposition/dissolution. When these carbon dots were incorporated into electrolytes of a LiFePO4 full cell, an initial capacity of 144.4 mAh g-1 was achieved, with a capacity retention of 95.1% after 100 cycles. This work showcases the unique advantages of boron-doped carbon dots in improving the operational performance of lithium metal batteries.

Key words: Carbon dots, Boron doping, Electrochemical energy storage, Electrolyte additives, Lithium metal anode