Engineered Electrode-Electrolyte Interface for Moisture-Stable, Dendrite-Free Garnet-Type Solid-State Electrolytes

Lithium-ion batteries (LIBs) are becoming increasingly universal energy storage systems to power most portable electronic devices and electric vehicles due to their high energy densities and long cycle life^1-3. However, with increasing applications of LIBs into grid storage, an increase in the efficiency of LIBs is essential to meet today's requirements^{2, 4}. Solid-state batteries using garnet-type solid-state electrolytes (SSEs) are promising contenders for safe, high energy density devices due to their high lithium-ion conductivity at room temperature, wide electrochemical stability window, and the use of lithium metal anode⁵. However, garnet-type SSEs exhibit formidable challenges including the formation of lithium dendrites, instability in moisture containing atmosphere, and their high interfacial resistance. Although several strategies have been employed to improve the issues related to garnet-type SSE, most approaches focus on one challenge and fail to solve all other challenges. Herein, we demonstrate an engineered electrode-electrolyte interface with surface modification of Li_6.5La₃Zr_1.5Ta_0.5O₁₂ (LLZT) garnet-type SSEs by two-dimensional hexagonal boron nitride (h-BN) nanosheets to solve the interfacial issues. Detailed spectroscopic evidence reveals that the surface modification effectively protects the LLZT from moisture-induced chemical degradation and suppresses the formation of adverse surface impurities for over 5 days in an open atmosphere. The interfacial resistance value has reduced nearly 10-fold when compared to the uncoated LLZT and exhibits stable lithium plating/stripping behavior for over 1400 hours at 0.2 mA cm^-2. Advanced in-situ Raman analysis elucidates that h-BN layers remain stable during cycling and prevents the structural transformation of the garnet-type SSE at the interface.

References:

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5. Jones, J. C.; Rajendran, S.; Pilli, A.; Lee, V. R.; Chugh, N.; Arava, L. M. R.; Kelber, J. A., In situ x-ray photoelectron spectroscopy study of lithium carbonate removal from garnet-type solid-state electrolyte using ultra high vacuum techniques. Journal of Vacuum Science & Technology A 2020, 38 (2), 023201.