PP/SnO2/PP sandwich separator: an electrochemical trap for proactive Li dendrite elimination and long-cycling lithium metal batteries

The uncontrollable growth of lithium (Li) dendrites severely hampers the commercialization of lithium metal batteries (LMBs). Herein, a highly integrated PP/SnO₂/PP sandwich-structured separator was designed and fabricated. Utilizing an innovative solvent-induced bonding and hot-pressing process, lithiophilic SnO₂ nanoparticles were precisely anchored within a dual-layer polypropylene framework. Morphological and chemical characterizations (SEM, XPS, and EDS) confirmed the uniform distribution and intimate interfacial contact of the modification layer. Electrochemical measurements demonstrated that the sandwich separator enables exceptionally high Coulombic efficiency at a current density of 1 mA cm⁻² and imparts superior cycling stability to LFP||Li cells. Mechanistic investigations reveal that the SnO₂ interlayer functions not merely as a physical barrier but, more importantly, as a ‘‘electrochemical trap.’’ Upon contact with the interlayer, Li dendrites trigger an in situ ‘‘micro-cell reaction,’’ which proactively eliminates dendrite tips via electrochemical ablation. This strategic shift from ‘‘passive blocking’’ to ‘‘proactive elimination’’ offers a novel perspective for designing high-safety lithium metal batteries.

Graphical abstract

Schematic diagram of the mechanism for an electrochemical trapping device used to actively eliminate lithium dendrites.

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