Seamlessly integrated alloy-polymer interphase for high-rate and long-life lithium metal anodes

Reasonably designed artificial solid-electrolyte interphases (ASEI) are essential for reversible and stable lithium metal batteries. However, poor compatibility between heterogeneous interfaces remains a challenge for the ASEI to sustain the long-term stability of the lithium metal anodes. Herein, an interfacial compatible protective layer with interpenetrating Li–Sn alloy across the PVDF-HFP interphase (ISPI) is fabricated on the lithium to realize seamless integration of the organic/inorganic components in the interphase, and the interface between ASEI and metallic Li simultaneously. Compared to the double-layered and uniform protective layers that both have sharp joint interfaces, ISPI achieves enhanced mechanical stability and ensures homogeneous lithium deposition underneath it even with a high capacity of 5.0 mAh/cm2. Utilizing this interface-compatible ISPI-Li anode, the Li│Li symmetric cells perform stably at a super high current density of 20 mA/cm2 with a capacity of 1 mAh/cm2 for over 1000 cycles, and the full cells with ISPI-Li anodes exhibit outstanding cycling performance when coupling with LiFePO4 or LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes. This work proposes a significant concept of designing artificial SEI with a seamlessly integrated interface for lithium metal anodes and uncovers the basic mechanism of interfacial compatibility as a key factor in achieving a highly reversible lithium anode for the practical usage of LMBs.