Orchestrating ion desolvation and transport via biomimetic dual-cascade separator for dendrite-free lithium metal anodes

Lithium (Li) dendrites, resulting from poor ion desolvation and transport behavior at the anode/electrolyte interface during electrodeposition, severely impede the practicality of Li metal anodes. Inspired by the transmembrane cascade transport mechanism of biological ion pumps, we design a biomimetic dual-cascade separator (BDS) based on gradient pore core–shell Gd2O3@ZIF-7 nanoparticles to stabilize Li metal anodes. The mesoporous Gd2O3 core, via Lewis acidic surface, weakens Li+-solvent interactions, thereby reconstructing the solvation structure and achieving pre-desolvation. The microporous ZIF-7 shell then promotes final desolvation through strong confinement effect and N-rich site coordination, while its nanochannels homogenize Li+ transport. This synergistic meso/microporous gradient creates a unique dual-cascade effect for ion desolvation and transport. Consequently, BDS achieves a low desolvation energy barrier, a high Li+ transference number (0.71), and dendrite-free Li deposition. The average Coulombic efficiency rises from 72.7 % to 98.4 %, the cycling performance of the Li||Li symmetrical cell improves by 3.2 times, and the capacity retention of LiFePO4(LFP)||Li full cell increases from 38.3 % to 73.4 % after 500 cycles. This work offers a novel separator design concept, deepens Li deposition understanding, and guides separators from passive protection to active regulation.