Surface Chemistry Mechanism of Ultra-Low Interfacial Resistance in the Solid-State Electrolyte Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> Asma Sharafi Eric Kazyak Andrew L. Davis Seungho Yu Travis Thompson Donald J. Siegel Neil P. Dasgupta Jeff Sakamoto 10.1021/acs.chemmater.7b03002.s001 https://acs.figshare.com/articles/journal_contribution/Surface_Chemistry_Mechanism_of_Ultra-Low_Interfacial_Resistance_in_the_Solid-State_Electrolyte_Li_sub_7_sub_La_sub_3_sub_Zr_sub_2_sub_O_sub_12_sub_/5368792 The impact of surface chemistry on the interfacial resistance between the Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> (LLZO) solid-state electrolyte and a metallic Li electrode is revealed. Control of surface chemistry allows the interfacial resistance to be reduced to 2 Ω cm<sup>2</sup>, lower than that of liquid electrolytes, without the need for interlayer coatings. A mechanistic understanding of the origins of ultra-low resistance is provided by quantitatively evaluating the linkages between interfacial chemistry, Li wettability, and electrochemical phenomena. A combination of Li contact angle measurements, X-ray photoelectron spectroscopy (XPS), first-principles calculations, and impedance spectroscopy demonstrates that the presence of common LLZO surface contaminants, Li<sub>2</sub>CO<sub>3</sub> and LiOH, result in poor wettability by Li and high interfacial resistance. On the basis of this mechanism, a simple procedure for removing these surface layers is demonstrated, which results in a dramatic increase in Li wetting and the elimination of nearly all interfacial resistance. The low interfacial resistance is maintained over one-hundred cycles and suggests a straightforward pathway to achieving high energy and power density solid-state batteries. 2017-09-01 00:00:00 resistance XPS Ultra-Low Interfacial Resistance surface chemistry Li 7 La 3 Zr 2 O 12 2 Ω cm 2 Surface Chemistry Mechanism Solid-State Electrolyte Li 7 La 3 Zr 2 O 12 LLZO surface contaminants Li contact angle measurements Li 2 CO 3 X-ray photoelectron spectroscopy