Natural “relief” for lithium dendrites: Tailoring protein configurations for long-life lithium metal anodes

Abstract

Rechargeable lithium metal batteries (LMBs) are faced with concerns of safety and short lifespan because of the uncontrollable growth of lithium (Li) dendrites. Natural biomolecules enriched with diverse polar groups are likely to have high lithiophilicity, showing the potential to suppress the dendrite growth. However, besides the chemical compositions, their structural diversities from nature induce notable impacts on the functions, which has not been studied yet. Here, through experiments and molecular simulations, we discover a natural “relief” for Li dendrites, zein protein, and successfully strengthen its dendrite-suppressing ability by tailoring its configurations to achieve long-life Li anodes. The “strong relief configuration” (SRC-Zein) is generated via drastically unfolding and opening the compact protein structure using a powerful denaturant. Modifying the separator by SRC-Zein results in excellent electrolyte wettability, higher ionic conductivity (2.0 mS/cm), and higher Li+ transference number (0.68), compared with the less unfolded protein. These important properties play the synergistical role in homogenizing the ion deposition and inhibiting the nucleation/growth of Li dendrites. As a result, the symmetrical Li/Li cell exhibits exceptional cycling stability for more than 1400 h at 2 mA/cm2. Furthermore, the half-cell with the SRC-Zein modified separator shows significant enhancement in capacity, cycle stability, and rate performance.