Interplay among Metallic Interlayers, Discharge Rate, and Pressure in LLZO-Based Lithium–Metal Batteries

Abstract

Solid-state electrolyte separators play a critical role in improving energy density, charging rate, and safety in next-generation batteries; however, controlling the interface between Li-metal and the separator continues to be challenging. Here, using a garnet-type Li7La3Zr2O12 (LLZO) ceramic solid electrolyte, we show that sputter-coated thin metallic interlayers (∼300 nm of gold) in combination with controlled discharge rates (0.3 mA/cm2) and practical levels of external pressure (0.7 MPa) play vital roles in mitigating void formation during discharge. These metallic-interlayer, Li-metal full cells achieve a high charging rate capability (up to 2.5 mA/cm2) and stable long-term cycling of 97.4% capacity retention at 500 cycles for ∼12 μm of Li-metal (2.5 mAh/cm2). We report progressive changes in the metallic-interlayer morphology measured with ex situ and in situ methods, revealing that a discontinuous metal interlayer can facilitate hundreds of repeated electrochemical cycles without significant loss in cell energy. Our proposed mechanism suggests that the Li–gold alloy particles act as pinning and/or rewetting points for the Li-metal during discharge.

Understanding and unveiling the electro‐chemo‐mechanical behavior in solid‐state batteries

“…Similarly, Thenuwara et al. designed Li–Au alloys interlayers to increase the wettability of Li anode with LLZO electrolytes, mitigating void formation and realizing stable long‐term cycling 48 . The authors used advanced x‐ray imaging to show the morphology of the gold interlayer without destroying any electrode structure after cycling (Figure 5A).…”

“…(A) x‐Ray tomography of the LLZO/Au/Li interface after cycling. Copyright, 2023 American Chemical Society 48 . (B) Schematics of the three‐diemnsional (3D) PZL/Li interfaces formation.…”

Computational approach inspired advancements of solid-state electrolytes for lithium secondary batteries: from first-principles to machine learning

“…, is another popular method to improve the wetting of the electrode/SSE interface and prevent parasitic reactions. 228–231 Numerical approaches have been employed to study the interfacial stability and kinetics of SSEs and metal anodes, as well as the underlying mechanisms, offering guidance on effective material selection strategies for electrode–SSE pairs and buffer layers. 232 The evolution of the SSE/anode interface without a buffer layer and with buffer layer/anode and buffer layer/SSE interfaces has been comprehensively assessed using atomistic simulations, offering guidance on material selection strategies for electrode–SSE pairs and buffer layers.…”

Rational Design of Lamellar Mixed Ion/Electron Conductive Layer for Dendrite-Free Garnet-Based Solid State Batteries

“…The reason was attributed to the Ag elements diffusing into the lithium metal during continuous alloying and dealloying, and led to the disruption of the modified layer structure. The highly reactive metal elements of buffer layer are tend to diffuse into Li metal during charging/discharging, leads to interfacial contact deteriorating. , The phenomenon of metallic interlayer element migrated into the Li was also found in Li|Au@LGLZO|Li …”