A Highly Reversible Room-Temperature Sodium Metal Anode

Abstract

Owing to its low cost and high natural abundance, sodium metal is among the most promising anode materials for energy storage technologies beyond lithium ion batteries. However, room-temperature sodium metal anodes suffer from poor reversibility during long-term plating and stripping, mainly due to formation of nonuniform solid electrolyte interphase as well as dendritic growth of sodium metal. Herein we report for the first time that a simple liquid electrolyte, sodium hexafluorophosphate in glymes (mono-, di-, and tetraglyme), can enable highly reversible and nondendritic plating–stripping of sodium metal anodes at room temperature. High average Coulombic efficiencies of 99.9% were achieved over 300 plating–stripping cycles at 0.5 mA cm–2. The long-term reversibility was found to arise from the formation of a uniform, inorganic solid electrolyte interphase made of sodium oxide and sodium fluoride, which is highly impermeable to electrolyte solvent and conducive to nondendritic growth. As a proof of concept, we also demonstrate a room-temperature sodium–sulfur battery using this class of electrolytes, paving the way for the development of next-generation, sodium-based energy storage technologies.

Microsized Sn as Advanced Anodes in Glyme‐Based Electrolyte for Na‐Ion Batteries

“…[33] The proportion of C-C(H) peak at 285 eV increases prominently after long cycling: an indication of the formation of sodium alkoxides (RCH 2 ONa) groups as a result of reduction of DGME. [34] Note also the appearance of another peak at 290 eV corresponding to the formation of Na 2 CO 3 . This assignment is confirmed by the O1s spectra which shows the growth of a carbonate specie peak at 531 eV.…”

Ultraconcentrated Sodium Bis(fluorosulfonyl)imide-Based Electrolytes for High-Performance Sodium Metal Batteries

“…[20][21][22][23][24][25][26][27] Nevertheless, the practical application of Na metal batteries is quite challenging because the high chemical and electrochemical reactivity of Na metal electrodes with organic liquid electrolytes leads to low Coulombic efficiencies and limited cycling performance. 20,[24][25][26] Severe electrolyte decomposition at the Na metal electrode results in the formation of a resistive and non-uniform surface film, leading to dendritic Na metal growth. To control the Na metal electrode-electrolyte interface for high performance Na metal batteries, considerable efforts have been made to find electrolyte systems that are stable at the Na metal electrode.…”

“…To control the Na metal electrode-electrolyte interface for high performance Na metal batteries, considerable efforts have been made to find electrolyte systems that are stable at the Na metal electrode. 20,21,[23][24][25][26] The use of linear carbonates such as dimethyl carbonate (DMC), which are widely used as electrolyte solvents in lithium batteries, is limited due to their drastic decomposition at Na metal electrodes and sodiated hard carbon anodes. 24,27 Using fluoroethylene carbonate (FEC) as an electrolyte additive for in situ formation of an artificial solid electrolyte interphase (SEI) layer could stabilize the anode-electrolyte interface ( Figure 2).…”

On the Reliability of Half-Cell Tests for Monovalent (Li+, Na+) and Divalent (Mg2+, Ca2+) Cation Based Batteries

“…Although these conditions are, at least satisfactorily, met in Li half-cells, 20 recent studies point to several issues associated with the use of Na metal CEs and REs. [21][22][23][24] No extensive studies have been made in order to evaluate the reliability of Mg and Ca half-cell configurations. Undeniably, the poor divalent cation mobility within the electrolyte is an important limiting factor in Ca based cells, as reported in Ref.…”