Sodium–sulfur batteries operating at a high temperature between 300 and 350°C have been used commercially, but the safety issue hinders their wider adoption. Here the authors report a “cocktail optimized” electrolyte system that enables higher electrochemical performance and room-temperature operation.
The as-developed sodium–sulfur batteries deliver high capacity and long cycling stability. To date, batteries based on alkali metal-ion intercalating cathode and anode materials, such as lithium-ion batteries, have been widely used in modern society from portable electronics to electric vehicles 1.
We also find that sulfur remains interred in the carbon pores and undergo solid-state electrochemical reactions with sodium ions. Rechargeable sodium-sulfur batteries able to operate stably at room temperature are sought-after platforms as they can achieve high storage capacity from inexpensive electrode materials.
Among the various battery systems, room-temperature sodium sulfur (RT-Na/S) batteries have been regarded as one of the most promising candidates with excellent performance-to-price ratios.
Lifetime is claimed to be 15 year or 4500 cycles and the efficiency is around 85%. Sodium sulfur batteries have one of the fastest response times, with a startup speed of 1 ms. The sodium sulfur battery has a high energy density and long cycle life. There are programmes underway to develop lower temperature sodium sulfur batteries.
A complete reaction mechanism is proposed to explain the sulfur conversion mechanism in room-temperature sodium-sulfur battery with carbonate-based electrolyte. The irreversible reactions about crystal sulfur and reversible two-step solid-state conversion of amorphous sulfur in confined space are revealed.