Bifunctional separators with high transference number and uniform ion flux for dendrite-free lithium metal batteries

The lithium metal anode is widely acknowledged as the coveted "holy grail" for the forthcoming generation of high energy density batteries, given its exceptional theoretical capacity and low potential. However, the formation and growth of dendrites seriously deteriorate battery life and safety. Here, hollow mesoporous silica nanospheres modified separators are proposed to promote the application of dendrite-free lithium metal batteries. The modified layer can function not only as an ion sieve to regulate the uniform distribution of lithium-ion flux for uniform deposition but also as an anion adsorber to increase the lithium-ion transference number from 0.34 to 0.70 for suppressing dendrite nucleation and growth. Compared with the cell with a baseline separator, those with modified separators exhibit higher coulombic efficiency (97.2% over 350 cycles), better rate performance (97 mAh g-1 at 10 C), and cycle stability (90% after 250 cycles). This work provides a feasible and effective strategy for separator modification to build a dendrite-free lithium metal anode and enhance cycling performance.