Additive engineering strategies for improved interfacial stability in lithium metal batteries

Electrolyte engineering is crucial for advancing lithium (Li) metal batteries (LMBs). Currently, unstable electrode-electrolyte interfaces limit the stable cycling of LMBs. Here, we introduce an additive engineering approach aimed at strengthening these electrode-electrolyte interfaces by incorporating the ionic additive tetrabutylammonium tetrafluoroborate into a low-concentration tetrahydrofuran ether electrolyte. Our findings reveal that tetrafluoroborate anions minimize corrosion and Li inventory loss. In addition, bulky tetrabutylammonium cations adsorbed onto the anode surface enable uniform and compact Li electrodeposition. This fluorinating and dendrite-suppressing mechanism supports stable high-current and high-capacity operations. Without altering the electrolyte solvation structure, the functional additive forms a robust interface with enhanced charge transport kinetics, specifically a stable solid-electrolyte interphase and cathode-electrolyte interphase. The designed electrolyte demonstrates 150 cycles 82.4% capacity retention in full cells employing 4 mA h cm-2 high-nickel cathodes under practical testing conditions (N/P = 1.75, E/C = 5.1 g A h-1). Additive engineering in low-concentration ether electrolytes enhances the electrode-electrolyte interfacial stability, enabling the stable cycling of high-energy, cost-effective lithium metal batteries.