A mortise–tenon-like ionic/electronic conductive interface facilitates long-cycle solid-state lithium metal batteries†

Abstract

Solid-state lithium metal batteries (SSLMBs) with high energy density and superior safety have been recognized as next-generation energy storage systems and have attracted a lot of attention. Garnet-type oxide solid-state electrolytes, especially Li_6.4La₃Zr_1.4Ta_0.6O₁₂ (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 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 a 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, the critical current density increases from 0.3 mA cm⁻² to 2.1 mA cm⁻², and a prominent cycling performance of 6600 h at 0.2 mA cm⁻² or 900 h at 0.4 mA cm⁻² is achieved. Consequently, both the Li|LZFC@LLZTO|LiFePO₄ and Li|LZFC@LLZTO|LiNi_0.8Co_0.1Mn_0.1O₂ full cells exhibit excellent rate performance. Furthermore, Li|LZFC@LLZTO|LiFePO₄ can maintain a high discharge specific capacity close to 140 mA h g⁻¹ at 0.2C 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.