Interplay among Metallic Interlayers, Discharge Rate, and Pressure in LLZO-Based Lithium–Metal Batteries
Akila C. Thenuwara, Eric L. Thompson, Thomas F. Malkowski, Kenneth D. Parrotte, Kathryn E. Lostracco, Sooraj Narayan, Ryan T. Rooney, Lori A. Seeley, Melroy R. Borges, Brent D. Conway, Zhen Song, Michael E. Badding, Kevin G. Gallagher
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 Li 7 La 3 Zr 2 O 12 (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/cm 2 ) 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/cm 2 ) and stable long-term cycling of 97.4% capacity retention at 500 cycles for ∼12 μm of Li-metal (2.5 mAh/cm 2 ). 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.