Toward Moisture-Stable and Dendrite-Free Garnet-Type Solid-State Electrolytes

Abstract

All-solid-state batteries using garnet-type solid-state electrolytes (SSEs) are promising candidates for safe, high energy density batteries due to their wide electrochemical stability window, high lithium-ion conductivity at room temperature, and the use of a lithium metal anode. However, garnet-type SSEs exhibit formidable challenges, including their instability in a moisture-containing atmosphere, high interfacial resistance, and the formation of lithium dendrites. Though several strategies have been deployed to alleviate the issues related to garnet-type SSEs against metallic lithium, most of the approaches fail to solve all the challenges. Herein, we demonstrate a surface modification strategy of the Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZT) garnet electrolyte by two-dimensional hexagonal boron nitride (h-BN) nanosheets to solve the interfacial issues. Detailed spectroscopic evidence elucidates that the h-BN interlayer effectively protects the LLZT from moisture-induced chemical degradation and suppresses the formation of adverse carbonate species for over 120 h in an open atmosphere. The h-BNcoated garnet SSE interface has shown a nearly 10-fold reduction in interfacial resistance value compared to the uncoated one and it exhibits stable lithium plating/stripping behavior for over 1400 cycles at 0.2 mA cm −2 . Advanced in situ Raman analysis reveals that the h-BN interlayers remain stable during cycling and inhibit the structural transformation of LLZT at the interface.

Smart Construction of an Intimate Lithium | Garnet Interface for All‐Solid‐State Batteries by Tuning the Tension of Molten Lithium

“…), [ 24 ] and inorganic thin films (BN, ZnO, Al 2 O 3 , Cu 3 N, SnN x , Ge, Sn, Mg, C, Au, Ag, etc.) [ 25,26 ] have been utilized to optimize the Li | garnet SSE interface. Although polymer‐based buffer layers are flexible and soft and enable intimate contact with garnet SSEs, their Li‐ion conductivity at room temperature is still insufficient.…”

Air‐stable inorganic solid‐state electrolytes for high energy density lithium batteries: Challenges, strategies, and prospects

“…Further studies found the hydrophobicity of h-BN whose contact angle was 125 effectively resisted the contact between moisture and LLZT. 91 Similar to h-BN, Li 3 PO 4 (LPO) was served as a protective layer on garnet SSEs. 92 In this work, air-stable LPO not only improved Li + conductivity of the grain boundaries and mechanical strength, but also generated an electron-insulating Li-ion conductive LPO-derived interface between the SSE and Li.…”

“…90 Copyright 2021, Elsevier); (E) concept graph of air-stable mechanism of garnet@h-BN (Reproduced with permission. 91 Copyright 2020, American Chemical Society); (F) concept graph of air-stable and Li freedendrite mechanism of garnet@LPO (Reproduced with permission. 92 Copyright 2020, Wiley-VCH) Liang et al 57 reported doping of Sn 4+ replacing Ge and P to synthesize Li 4 SnS 4 and Li 4 Sn x As y S 4 .…”

“…No Li 2 CO 3 was formed on PDA‐treated LLZTO, which was confirmed by XRD patterns, FT‐IR spectra, and Raman spectra (Figure 5B–D). 90 Moreover, Arava et al 91 used hexagonal boron nitride (h‐BN) nanosheets as a coating layer to modify the surface of Li 6.5 La 3 Zr 1.5 Ta 0.5 O 12 (LLZT). With a high dielectric constant and Young's modulus, h‐BN was able to protect the garnet SSEs from the attack of Li.…”

“…Besides ionically conductive and electronically insulative nature, it was also chemically and mechanically stable, as shown in Figure 5E, which successfully suppressed the formation of Li 2 CO 3 , H + /Li + exchange, and structural transformation based on the results observed by XPS and thermogravimetric analyzer analysis. Further studies found the hydrophobicity of h‐BN whose contact angle was 125° effectively resisted the contact between moisture and LLZT 91 . Similar to h‐BN, Li 3 PO 4 (LPO) was served as a protective layer on garnet SSEs 92 .…”