Recent progress of functional separators in dendrite inhibition for lithium metal batteries

Lithium metal battery is one of the most promising candidates for high power portable electronic devices and long-range electric vehicles, due to its ultra-high theoretical energy density when compared with the current commercial Li-ion batteries. Meanwhile, the metallic lithium also brings safety concern because Li+ ions tend to form lithium dendrite on the uneven surface of anode, and subsequently cause short circuit, fire or explosion of the battery. In this review, we summarized the formation mechanism of lithium dendrite and the corresponding inhibiting strategies via functional separators in lithium metal batteries. The lithium dendrite inhibiting strategies via functional separators can be classified into three catalogs: (i) block the growth of lithium dendrite by mechanical barrier, (ii) redistribute the Li+ ion flux when passing through the separator and (iii) induce the uniform deposition of Li+ ions on anode by nucleation sites. The recent advances of the above strategies are reviewed and discussed, existing critical problems and future perspective of functional separators for lithium dendrite inhibition are also discussed.