Stabilizing Na₃Zr₂Si₂PO₁₂/Na Interfacial Performance by Introducing a Clean and Na-Deficient Surface

Abstract

Most Li+/Na+-conducting solid electrolytes are unstable in moisture, and the formed hydroxides and carbonates on their surfaces result in the increase of the interfacial resistance between solid electrolytes and alkali metal anodes. In this study, heat treatment was used to remove the byproduct coating on the surface of Na3Zr2Si2PO12 (NZSP) that also leads to the generation of Na-ion deficient surface simultaneously. This surface chemistry approach was used to reduce the interfacial resistance and suppress Na-dendrite growth during Na plating. A combination of the metallic Na wetting test, density functional theory, and electrochemical measurement was employed to investigate the origins of ultralow interfacial resistance and mechanism between the Na-ion deficient surface and the metallic Na anode. The analysis demonstrates that the Na-ion-deficient surface effectively improves the contact between NZSP and the metallic Na anode. Moreover, an ultrathin passivating layer involving Na2O was formed between NZSP with metallic Na that protected the NZSP electrolyte from the reduction by metallic Na. This study not only motivates the need for further understanding of the surface chemistry of NZSP but also provides guidelines for the future design of the Na-ion solid–electrolyte interface.

Solid Electrolyte Interphases on Sodium Metal Anodes

“…Besides, heat treatment is another simple and promising technique to construct a Na‐ion deficient surface on NZSP for good contact. [ 172 ]…”

Progress and Challenges for All‐Solid‐State Sodium Batteries

“…[ 176 ] Guo et al investigated the surface chemistry of NZSP and further proposed a Na‐deficient surface on it, which can effectively enhance its interfacial Na anode performance ( Figure a). [ 177 ] They used a simple heating method to decompose the surface by product of NZSP to form a Na‐deficient surface on NZSP. This surface could significantly reduce the Na metal anode/NZSP interfacial resistance, and symmetric cells of Na/NZSP (HT)/Na, where HT is high temperature, at a current density of 0.1 mA cm −2 could cycle for over 1500 h. Zhou et al [ 178 ] also reported that the NZSP membrane was quite stable toward Na anode, and when Na metal was heated at 380 °C, a black layer was formed on the surface of the NZSP.…”

“…Reproduced with permission. [ 177 ] Copyright 2020, American Chemical Society. b) Schematic illustration of the interface between Na–SiO 2 and NASICON solid electrolyte, and their electrochemical performance.…”

Inorganic Solid Electrolytes for All‐Solid‐State Sodium Batteries: Fundamentals and Strategies for Battery Optimization

“…NZSPO possesses similar chemical stability as β/β″‐Al 2 O 3 , and there would form Na 2 CO 3 and NaOH on the surface of NZSPO due to the slow chemical reaction between the humid air and NZSPO. [ 69 ] All NZSPO oxides are thermodynamically unstable at low potentials. The most conductive Na 3 Zr 2 Si 2 PO 12 could be decomposed into Na 3 P, ZrO 2 , and Na 3 PO 4 below 1.1 V versus Na/Na + , and oxidized into ZrSiO 4 , NaZr 2 P 3 O 12 , SiO 2 , and O 2 up to ≈3.6 V (Figure 14c), [ 20 ] and therefore, it can potentially be coupled with 4V‐class ceramic‐cathodes.…”