Reducing Interfacial Resistance between Garnet-Structured Solid-State Electrolyte and Li-Metal Anode by a Germanium Layer

Wei Luo; Yunhui Gong; Yizhou Zhu; Yiju Li; Yonggang Yao; Ying Zhang; Kun Kelvin Fu; Glenn Pastel; Chuan-Fu Lin; Yifei Mo; Eric D Wachsman; Liangbing Hu

doi:10.1002/adma.201606042

Reducing Interfacial Resistance between Garnet-Structured Solid-State Electrolyte and Li-Metal Anode by a Germanium Layer

Adv Mater. 2017 Jun;29(22). doi: 10.1002/adma.201606042. Epub 2017 Apr 18.

Authors

Wei Luo^{1

2}, Yunhui Gong^{1

3}, Yizhou Zhu¹, Yiju Li¹, Yonggang Yao¹, Ying Zhang¹, Kun Kelvin Fu^{1

3}, Glenn Pastel¹, Chuan-Fu Lin¹, Yifei Mo^{1

3}, Eric D Wachsman^{1

3}, Liangbing Hu^{1

3}

Affiliations

¹ Department of Materials Science and Engineering, University of Maryland, College Park, MD, 20742, USA.
² Department of Mechanical Engineering, University of Maryland, College Park, MD, 20742, USA.
³ University of Maryland Energy Research Center, University of Maryland, College Park, MD, 20742, USA.

PMID: 28417487
DOI: 10.1002/adma.201606042

Abstract

Substantial efforts are underway to develop all-solid-state Li batteries (SSLiBs) toward high safety, high power density, and high energy density. Garnet-structured solid-state electrolyte exhibits great promise for SSLiBs owing to its high Li-ion conductivity, wide potential window, and sufficient thermal/chemical stability. A major challenge of garnet is that the contact between the garnet and the Li-metal anodes is poor due to the rigidity of the garnet, which leads to limited active sites and large interfacial resistance. This study proposes a new methodology for reducing the garnet/Li-metal interfacial resistance by depositing a thin germanium (Ge) (20 nm) layer on garnet. By applying this approach, the garnet/Li-metal interfacial resistance decreases from ≈900 to ≈115 Ω cm² due to an alloying reaction between the Li metal and the Ge. In agreement with experiments, first-principles calculation confirms the good stability and improved wetting at the interface between the lithiated Ge layer and garnet. In this way, this unique Ge modification technique enables a stable cycling performance of a full cell of lithium metal, garnet electrolyte, and LiFePO₄ cathode at room temperature.

Keywords: Li-metal anodes; first-principles calculations; garnet; reducing interfacial resistance; solid-state electrolytes.