A Sodiophilic Amyloid Fibril Modified Separator for Dendrite‐Free Sodium‐Metal Batteries

Abstract Sodium (Na) batteries are being considered as prospective candidates for the next generation of secondary batteries in contrast to lithium‐based batteries, due to their high raw‐material abundance, low cost, and sustainability. However, the unfavorable growth of Na‐metal deposition and severe interfacial reactions have prevented their large‐scale applications. Here, a vacuum filtration strategy, through amyloid‐fibril‐modified glass‐fiber separators, is proposed to address these issues. The modified symmetric cell can be cycled for 1800 h, surpassing the performance of previously reported Na‐based electrodes under an ester‐based electrolyte. Moreover, the Na/Na 3 V 2 (PO 4 ) 3 full cell with a sodiophilic amyloid‐fibril‐modified separator exhibits a capacity retention of 87.13% even after 1000 cycles. Both the experimental and the theoretical results show that the sodiophilic amyloid fibril homogenizes the electric field and Na‐ion concentration, fundamentally inhibiting dendrite formation. Simultaneously, the glutamine amino acids in the amyloid fibril have the highest adsorption energy for Na, resulting in the formation of a stable Na 3 N‐ and NaN x O y ‐rich solid‐electrolyte‐interface film on the anode during cycling. This work provides not only a possible pathway to solve the dendrite problem in metal batteries using environmentally friendly biomacromolecular materials, but also a new direction for expanding biomaterial applications.