Ran Wei,Yue Zhang,Jiameng Yu,Xinshui Zhang,Yining Zhang,Tianyi Gao,Yi Yu,Jie Zhao,Wei Liu
Ta-doped Li6.4La3Zr1.4Ta0.6O12 (LLZTO) for solid-state lithium batteries demonstrates encouraging performance; however, they encounter issues with lithium dendrite formation that impede their widespread use. Herein, we design a LLZTO ceramic with an interlayer containing a mixed dense layer of Ag and LLZTO, prepared by one-step sintering. The Ag-rich interlayer in LLZTO can hinder the growth and the penetration of lithium dendrites though the reaction between Ag and lithium metal. Compared with the Ag-free counterpart, a higher critical current density of 0.6 mA cm–2, in addition to a longer life span under a current density of 0.2 mA cm–2, is achieved by adopting the interlayer in LLZTO. This research offers novel insights into the engineering of garnet-based solid electrolytes, tailored for the advancement of high-rate lithium metal batteries.
Investigating the growth kinetics of Li metal in solid-state batteries is crucial to both a fundamental understanding and practical application. Here, by directly observing the formation of Li metal from Ta-doped Li6.4La3Zr1.4Ta0.6O12 (LLZTO) in a transmission electron microscope, the growth kinetics is analyzed quantitatively. The growth kinetics of Li deposits shows a cubic-curve characteristic for LLZTO with Li-source-free. Instead, a linear growth process is observed with Li-source supplied. The impact of the illuminating electron dose rate on the growth kinetics is clarified, indicating that even low dose rates (1–3 e–/Å2/s) could affect Li growth, highlighting the significance of controlling dose rates. Furthermore, a new pathway for the formation of Li metal from Li-containing materials utilizing the field-emission effect is reported. This work has implications on the failure mechanism in solid batteries by using limited Li anodes and opens pathways for regulating Li growth in LLZTO at various scenarios, which can also extend to other ionic conductors.
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 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 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|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 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.
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