A Forceful "Dendrite-Killer" of Polyoxomolybdate with Reusability Effectively Dominating Dendrite-Free Lithium Metal Anode.

In this work, a series of Mo-containing polyoxometalates (POMs) modified separators to inhibit the growth of lithium dendrites, and thus improving the lifespan and safety of the cells is proposed. When the deposited lithium forms dendrites and touches the separator, the optimized Dawson-type POM of (NH 4 ) 6 [P 2 Mo 18 O 62 ]·11H 2 O (P 2 Mo 18 ) with the stronger oxidizability, acts like a "killer", is more inclined to oxidize Li 0 into Li + , thus weakening the lethality of lithium dendrites. The above process is accompanied by the formation of Li x [P 2 Mo 18 O 62 ] (x = 6-10) in its reduced state. Converting to the stripping process, the reduced state Li x [P 2 Mo 18 O 62 ] (x = 6-10) can be reoxidized to P 2 Mo 18 , which achieves the reusability of P 2 Mo 18 functional material. Meanwhile, lithium ions are released into the cell system to participate in the subsequent electrochemical cycles, thus the undesired lithium dendrites are converted into usable lithium ions to prevent the generation of "dead lithium". As a result, the Li//Li symmetrical cell with P 2 Mo 18 modified separator delivers exceptional cyclic stability for over 1000 h at 3 mA cm -2 and 5 mAh cm -2 , and the assembled Li-S full cell maintains superior reversible capacity of 600 mAh g -1 after 200 cycles at 2 C.