Converting an O-vacancy-rich oxide into a multifunctional separator modifier for long-lifespan lithium metal batteries

The lithium metal anode is hailed as the desired "holy grail" for the forthcoming generation of high-energy-density batteries, given its astounding theoretical capacity and low potential. Nonetheless, the formation and growth of dendrites seriously compromise battery life and safety. Herein, an yttria-stabilized bismuth oxide (YSB) layer is fabricated on the polypropylene (PP) separator, where YSB reacts with Li anode in-situ in the cell to form a multi-component composite interlayer consisting of Li3Bi, Li2O, and Y2O3. The interlayer can function not only as a redistributor to regulate Li+ distribution but also as an anion adsorber to increase the Li+ transference number from 0.37 to 0.79 for suppressing dendrite nucleation and growth. Consequently, compared with the cell with a baseline separator, those with modified separators exhibit prolonged lifespan in both Li/Li symmetrical cells and Li/Cu half-cells. Notably, the full cells coupled with ultrahigh-loading LiFePO4 display an excellent cycling performance of 1700 cycles with a high capacity retention of ∼80% at 1 C, exhibiting great potential for practical applications. This work provides a feasible and effective new strategy for separator modification towards building a much-anticipated dendrite-free Li anode and realizing long-lifespan lithium metal batteries.