Prevention of Na Corrosion and Dendrite Growth for Long-Life Flexible Na–Air Batteries

Abstract

Rechargeable Na–air batteries (NABs) based on abundant Na resources are generating great interest due to their high energy density and low cost. However, Na anode corrosion in ambient air and the growth of abnormal dendrites lead to insufficient cycle performance and safety hazards. Effectively protecting the Na anode from corrosion and inducing the uniform Na plating and stripping are therefore of vital importance for practical application. We herein report a NAB with in situ formed gel electrolyte and Na anode with trace residual Li. The gel electrolyte is obtained within cells through cross-linking Li ethylenediamine at the anode surface with tetraethylene glycol dimethyl ether (G4) from the liquid electrolyte. The gel can effectively prevent H 2 O and O 2 crossover, thus delaying Na anode corrosion and electrolyte decomposition. Na dendrite growth was suppressed by the electrostatic shield effect of Li + from the modified Li layer. Benefiting from these improvements, the NAB achieves a robust cycle performance over 2000 h in opened ambient air, which is superior to previous results. Gelation of the electrolyte prevents liquid leakage during battery bending, facilitating greater cell flexibility, which could lead to the development of NABs suitable for wearable electronic devices in ambient air.

Growth Mechanism of Micro/Nano Metal Dendrites and Cumulative Strategies for Countering Its Impacts in Metal Ion Batteries: A Review

“…From the analytical characterizations, the amount of O2 crossover was 40%, with no CO2 crossover observation for the initial 20 min; later, 55% CO2 crossover was noted due to the absorption of CO2 by ethylenediamine. Notably, no H2O and O2 crossover was observed, which accounted for the stability of the Na anode [374].…”

“…Inorganic solid electrolytes consist of symmetrical structures as moveable ions, which dislocate from one site to another, creating vacancies (Frenkel and Schottky defects). Crosslinking of compounds and ion migration plays an imperative role in inorganic electrolytic conduction [373,374]. Therefore, the available hopping sites or vacancies have to be optimized for the efficient functioning of the battery.…”

“…Recently, a Li@Na anode was prepared by cross-linking lithium ethylenediamine at the anodic surface and tetraethylene glycol dimethyl ether from the electrolyte, forming a stable gel electrolyte [374]. This new type of gel electrolyte effectively inhibited Na dendrites by the electrostatic shield effect mechanism, controlling the migration of surface charges.…”

Rational Design of Electrolyte Solvation Structures for Modulating 2e−/4e− Transfer in Sodium–Air Batteries

“…Rechargeable sodium–air batteries (SABs) have attracted attention as next generation high energy density batteries owing to their high theoretical energy densities, low cost, and environmental friendliness. [ 1–4 ] The reactions occurring in SABs are mainly classified into 1e − , 2e − , and 4e − reactions according to the different types of discharge products (NaO 2 , Na 2 O 2 , Na 2 O 2 ·2H 2 O, or NaOH). [ 1,4–6 ] Among these reactions, 1e − or 2e − reactions (aprotic reactions) possess advantages of fast reaction kinetics and high reaction efficiency, while 4e − reaction (proton reactions) possess the advantages low overpotential and high cyclic stability.…”

Guiding Uniform Sodium Deposition through Host Modification for Sodium Metal Batteries

“…This gives room‐temperature Na−S batteries a much higher specific energy of 1,274 Wh kg −1 compared to 760 Wh kg −1 for high‐temperature Na−S batteries [3e] . Apart from Na−S batteries, Na‐air batteries are gaining immense attention as well because of their high specific energy (∼1,605 Wh kg −1 ) [7] and low cost (projected to be 1/3 rd of Li‐air batteries) [8] . The technology of room‐temperature Na−S and Na‐air batteries is still in its infancy, and demands much more research to realize its full potential.…”