The growing demands for electric vehicles and consumer electronics; as well as the expanding renewable energy storage market; have promoted extensive research on energy storage technologies with low costhigh energy density and safety. Lithium (Li) metal and solid-state electrolytes are considered as important components for next-generation batteries because of their great potential for improvements in energy density and safety performance. Inorganic garnet-type solid electrolytes with high Li-ion conductivity (about 10-3 S·cm-1) and high shear modulus (55 GPa) are considered to be ideal solid-state electrolytes; however; the issue of Li dendrite growth still obstructs their practical application. Herein; a simple and efficient strategy was developed to suppress the Li dendrite formation in the garnet solid electrolytes. A composite modification layer made of 2 nm LiF and 2 nm Sn thin layers was prepared on the surface of the Li6.5La3Zr1.4Ta0.6O12 (LLZTO) solid electrolyte by the high vacuum evaporation. The composite modification layer combined the advantages of LiF and Sn; which effectively improves the interfacial contact between the Li metal and LLZTO electrolyte; and promotes the uniform Li plating/stripping. The LiF-Sn composite modification layer was deposited on the surface of garnet electrolyte to increase the interfacial wettability between the garnet electrolyte and Li metal; which blocks the injection of electrons into the bulk phase of garnet. The LiF-Sn modification layer effectively enhanced the interfacial contact and inhibited the growth of lithium dendrites. Benefiting from the LiF-Sn interfacial modification; the cross-sectional SEM image shows the intimate contact between the LLZTO-LiF-Sn and the Li metal without any voids. In addition; the interfacial impedance of Li/garnet electrolyte interface decreased from 969 Ω·cm2 to 3.5 Ω·cm2. Meanwhile, the critical current density of the Li symmetric cell increased to 1.3 mA·cm-2, and the Li symmetric cell could be cycled stably for 200 h at a current density of 0.4 mA·cm-2. After disassembling the short-circuited Li/LLZTO/Li cell and reacting the Li metal with alcohol solution; it was found that Li dendrites had grown into the LLZTO pellet. However; the surface of the LiF-Sn-protected LLZTO remained smooth without dark spots from dendrites. The excellent electrochemical performance clearly shows that the LiF-Sn composite modification can effectively inhibit the formation of Li dendrite inside the garnet SSE, proving that this interfacial engineering provides a practical solution for addressing the key challenge of Li/LLZTO interface. At the same time; high vacuum evaporation is a matured industrial technology with large-scale application prospects and can be widely used to solve solid-state interface problems.
LiF, Sn, Vacuum thermal evaporation, Critical current density, Long cycle performance
Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 International License.
Online Available Date
Wu Yang, Xue-Fan Zheng, Yu-Qi Wu, Zheng-Liang Gong.
LiF-Sn Composite Modification Layer to Modify Garnet/Lithium Metal Interface[J]. Journal of Electrochemistry,
Available at: https://jelectrochem.xmu.edu.cn/journal/vol29/iss11/1