Mortise-tenon-like ionic/electronic conductive interface facilitates long-cycle solid-state lithium metal batteries

The high energy density and superior safety of solid-state lithium metal batteries (SSLMBs) has been recognized as a next-generation energy storage system with great attention. Garnet-type oxide solid-state electrolytes, especially Li6.4La3Zr1.4Ta0.6O12 (LLZTO), with high ionic conductivity, low activation energy and superior stability with Li, are among the most promising solid-state electrolyte materials. However, high interfacial resistance, uneven lithium deposition and lithium dendrite growth between Li/LLZTO interfaces have hindered the industrialization development of SSLMBs. In this work, a novel mortise-tenon-like hybrid ionic/electronic conductive interface (Li/LZFC@LLZTO) is constructed, which is composed of LiF, LiCl, and Li-Zn alloy through an in situ transformation reaction. As expected, the interfacial impedance of Li/LZFC@LLZTO|Li is significantly reduced from 128 Ω cm2 to 2.7 Ω cm2 and the critical current density increases from 0.3 mA cm-2 to 2.1 mA cm-2, as well as prominent cycling performance of 6600 h at 0.2 mA cm-2 or 900 h at 0.4 mA cm-2. Consequently, both the Li|LZFC@LLZTO|LiFePO4 and Li|LZFC@LLZTO|LiNi0.8Co0.1Mn0.1O2 full cells exhibit excellent rate performance. Furthermore, Li|LZFC@LLZTO|LiFePO4 can maintain a high discharge specific capacity close to 140 mAh g-1 at 0.2 C after 150 cycles of stable cycling. This work lays the foundation for developing garnet-based SSLMBs with high critical current density, low interfacial impedance and long-term cycling performance.