Transient Behavior of the Metal Interface in Lithium Metal–Garnet Batteries

Abstract

The interface between solid electrolytes and Li metal is aprimary issue for solid-state batteries.Introducing ametal interlayer to conformally coat solid electrolytes can improve the interface wettability of Li metal and reduce the interfacial resistance,b ut the mechanism of the metal interlayer is unknown. In this work, we used magnesium (Mg) as am odel to investigate the effect of am etal coating on the interfacial resistance of asolid electrolyte and Li metal anode.The Li-Mg alloyh as low overpotential, leading to al ower interfacial resistance.O ur motivation is to understand howt he metal interlayer behaves at the interface to promote increased Limetal wettability of the solid electrolyte surface and reduce interfacial resistance.S urprisingly,w ef ound that the metal coating dissolved in the molten piece of Li and diffused into the bulk Li metal, leading to as mall and stable interfacial resistance between the garnet solid electrolyte and the Li metal. We also found that the interfacial resistance did not change with increase in the thickness of the metal coating (5, 10, and 100 nm), due to the transient behavior of the metal interface layer.The adoption of lithium (Li)m etal as anode is critical to achieving high energy and high power density batteries since Li metal has the highest theoretical capacity (3860 mAh g À1 ) while maintaining the lowest electrochemical potential (À3.04 Vv ersus the standard hydrogen electrode). [1][2][3][4][5][6] However,the penetration of Li dendrites through the separator in batteries,w hich raises safety concerns and often results in battery performance decay,h ave limited the use of Li metal anodes for decades.R ecently,e xtensive studies of Li metal composites and modified separators to suppress or delay Li dendrite growth have been reported. [7][8][9][10][11][12][13][14] In comparison to those efforts,a na ll-in-one strategy is to use as olid-state electrolyte to replace polymer separators and physically block the Li dendrite penetration [15][16][17][18][19][20][21][22] Theu se of as olid-state electrolyte has many advantages over organic liquid electrolyte in batteries;f or example,as olid-state electrolyte generally has aw ide stability window (0-5 V), good thermal stability,a nd an intrinsic nonflammability. [20,21,23] Among the different types of solid-state electrolytes,t he Li 7 La 3 Zr 2 O 12 (LLZO) garnet-type solid-state electrolyte is al eading candidate for Li metal batteries,due to its high ionic conductivity (10 À3 -10 À4 Scm) and chemical stability against Li metal. [20,[23][24][25][26][27][28][29][30][31][32][33] Amajor challenge of using the garnet solid-state electrolyte in aL im etal battery is the poor contact at the interface between the garnet and the Li metal, leading to ah igh interfacial impedance of 10 2 -10 3 ohm cm À2 .E xtensive work has been reported to reduce the interfacial impedance,f or example,b ym odifying solid electrolyte composition, using gel or polymer interlayers,a nd constructing interface structures. [11,15,17,22,[34][35][36][37...

Recent Advances in Energy Chemistry between Solid-State Electrolyte and Safe Lithium-Metal Anodes

“…The poor contact cannot be effectively relieved by high-temperature pretreatment due to the lithiophobic nature of many SSEs. 36 Hu and co-workers proposed an interface design between Li metal and SSE to improve the wettability, such as Mg coating to form the Li-Mg alloy 70 and ZnO. 71 Al 4 Li 9 72 and Au 73 coating can also be introduced to wet the interface.…”

The Role of Interlayer Chemistry in Li‐Metal Growth through a Garnet‐Type Solid Electrolyte

“…Poor contact between lithium metal and LLZO has been reported to cause large interfacial resistance that results in an inhomogeneously distributed current that triggers such failure 19,26,27,30. In this respect, recent studies have attempted to reduce contact resistance by removing surface impurities or introducing an artificial interlayer between the lithium metal and the LLZO, which have led to some improvements 26,27,31–37…”

Li2CO3-affiliative mechanism for air-accessible interface engineering of garnet electrolyte via facile liquid metal painting

“…In order to modify the interface contact, some methods have been attempted to eliminate Li 2 CO 3 (e.g., by carbothermal reaction, high-temperature calcination, or acid treatment) or construct lithiophilic interlayer (e.g., by depositing alloyable film, decorating Li + -conductive polymer, pasting soft graphite, or two-dimensional MoS 2 ) 17 – 25 . For the alloyable strategy, some expensive installations and refined manipulation for thin film deposition (e.g., atomic layer deposition and chemical vapor deposition) are usually required in order to achieve compact planar contact 21 , 26 , 27 . Although the facile addition of alloyable elements (e.g., Sn or graphite) into molten Li can also improve the wettability of anode on LLZO by tuning the surface tension and viscosity of molten lithium 28 , 29 , a high weight percent of blended alloy (e.g., blending 50% Sn or 70% graphite) is required for best wetting effect.…”