Enhancing the Cycling Stability of Sodium Metal Electrodes by Building an Inorganic–Organic Composite Protective Layer

Abstract

Owing to the natural abundance of sodium resources and their low price, next-generation batteries employing an Na metal anode, such as Na-O and Na-S systems, have attracted a great deal of interest. However, the poor reversibility of an Na metal electrode during repeated electrochemical plating and stripping is a major obstacle to realizing rechargeable sodium metal batteries. It mainly originates from Na dendrite formation and exhaustive electrolyte decomposition due to the high reactivity of Na metal. Herein, we report a free-standing composite protective layer (FCPL) for enhancing the reversibility of an Na metal electrode by mechanically suppressing Na dendritic growth and mitigating the electrolyte decomposition. A systematic variation of the liquid electrolyte uptake of FCPL verifies the existence of a critical shear modulus for suppressing Na dendrite growth, being in good agreement with a linear elastic theory, and emphasizes the importance of the ionic conductivity of FCPL for attaining uniform Na plating and stripping. The Na-Na symmetric cell with an optimized FCPL exhibits a cycle life two times longer than that of a bare Na electrode.

Pillared MXene with Ultralarge Interlayer Spacing as a Stable Matrix for High Performance Sodium Metal Anodes

“…For example, adjusting electrolyte compositions, such as NaAlCl 4 ·2SO 2 inorganic electrolyte and ether based electrolyte together with appropriate Na salts and electrolyte additives, can assist the formation of a stable SEI. Moreover, constructing artificial SEI layers, including ultrathin graphene films, atomic Al 2 O 3 layer, Al 2 O 3 inorganic particles and polymer layer, Sn–Na hybrid and NaBr interphases, can also effectively protect Na metal surface. However, distinctly different from Li, Na has low metallic bonding energy, and thus possesses inferior mechanical property and is susceptible to deform and degrade during the battery assembly and cycling process.…”

Thermoplastic Polyurethane Elastomer‐Based Gel Polymer Electrolytes for Sodium‐Metal Cells with Enhanced Cycling Performance

“…All XP spectra were normalized with respectt ot he Na Augerp eak at 536.0 eV.T he C1sX Ps pectrum shows five peaks, which correspond to CÀCs pecies (285.0 eV), CÀOs pecies( 286.8 eV), C=Os pecies (288.0 eV), sodium alkyl carbonate (ROCO 2 Na, 289.1 eV), and sodium carbonate (Na 2 CO 3 , 290.0 eV). [18] In the O1ss pectrum, four peaks correspondingt os odium oxide (Na 2 O, 529.7 eV), sodium carbonate (Na 2 CO 3 ,5 31.6 eV), sodium hydroxide or CÀOs pecies (NaOH or CÀO, 532.8 eV), and C=Os pecies (534.1 eV) were observed. [18] These chemical components are formed by reductived ecomposition of the liquid electrolyte.…”

“…[18] In the O1ss pectrum, four peaks correspondingt os odium oxide (Na 2 O, 529.7 eV), sodium carbonate (Na 2 CO 3 ,5 31.6 eV), sodium hydroxide or CÀOs pecies (NaOH or CÀO, 532.8 eV), and C=Os pecies (534.1 eV) were observed. [18] These chemical components are formed by reductived ecomposition of the liquid electrolyte. For the sodium electrode cycled in the gel polymer electrolyte, the lower peak intensities in the XP spectra compared with those in the XP spectra of the electrode cycled in the liquid electrolyte indicate suppressed decomposition of the electrolyte.…”

Dendrite‐Free Sodium Metal Anodes Enabled by a Sodium Benzenedithiolate‐Rich Protection Layer

“…After 10 cycles, the above two peaks still exist in the spectrum, suggesting the presence of Ph−S in the layer after cycling. Three extra peaks at 286.3 eV (C−O), 288 eV (C=O), and 289.6 eV (O−C=O) after cycling correspond to the groups of decomposed products of electrolytes . The clear difference with and without the protection layer is observed in the spectra of S 2p.…”