Self-healing and robust polymer-based protective interlayer containing boronic esters for stabilizing lithium metal anode

Lithium (Li) metal batteries have attracted wide research interests due to the ultrahigh theoretical capacity of Li anode. However, lithium metal anodes suffer from the inhomogeneous Li deposition, resulting in capacity fade and unacceptable safety hazards. More importantly, the huge volume change of the mechanically fragile solid electrolyte interphase (SEI) further induces the dendrite growth during repeated Li plating. Therefore, it is critical to protect Li metal anodes and inhibit the growth of Li dendrites for stabilizing the Li plating process. Herein, we fabricated a novel polymer-based protective interlayer (LBP) with a stable cross-linked network containing abundant boron moieties via the thiol-ene click reaction. The polymer-based protective interlayer obtains self-healing properties through the boronic ester transesterification and enhances the safety of lithium batteries. Besides, the dense layer with a cross-linked network effectively retards the air corrosion when the Li metal was exposed to the air environment. Furthermore, the vacant p orbital in the boron atoms of boronic ester can trap anions of Li salt and regulate a homogeneous Li deposition, enhancing the interface stability of Li metal. Consequently, the Li|Li symmetric cell with LBP protective interlayer shows stable stripping/plating voltage over 3500 h at 1.0 mA cm-2. The LBP-Li|LFP cell maintains a high capacity of 142.2 mAh/g after 300 cycles, demonstrating the cell with LBP-Li exhibits excellent cycling stability. The design of this advanced protective interlayer with multiple capabilities is potential to shed a light for high-performance lithium metal batteries.