Nitrofullerene, a C60-based Bifunctional Additive with Smoothing and Protecting Effects for Stable Lithium Metal Anode.

Abstract

Practical applications of lithium metal anodes are gravely impeded by inhomogeneous lithium deposition, which results in dendrite growth. Electrolyte additives are proven to be effective in improving performance but usually serve only a single function. Herein, nitrofullerene is introduced as a bifunctional additive with a smoothing effect and forms a protective solid electrolyte interphase (SEI) layer on stable lithium metal anodes. By design, nitro-C60 can gather on electrode protuberances via electrostatic interactions and then be reduced to NO2- and insoluble C60. Next, the C60 anchors on the uneven groove of the lithium surface, resulting in a homogeneous distribution of Li ions. Finally, NO2- anions can react with metallic Li to build a compact and stable SEI with high ion transport. With a 5 mM nitro-C60 additive, Li-Li symmetric cells show superior cycle stability in both carbonate and ether electrolytes, Li-sulfur batteries with a high cathode loading (10.6 mg cm-2, 6 mAh cm-2) can achieve improved cycle retention of 63.2% over 100 cycles in a carbonate electrolyte, and full cells paired with a high-areal-capacity LiNi0.6Co0.2Mn0.2O2 cathode (3.5 mAh cm-2) exhibit a significantly enhanced cycle lifespan even under lean electrolyte conditions.