Hard Carbon Anodes and Novel Electrolytes for Long‐Cycle‐Life Room Temperature Sodium‐Sulfur Full Cell Batteries

Abstract

A novel combination of hard carbon anode sodium pre-loading and a tailored electrolyte is used to prepare room temperature sodium-sulfur full cell batteries. The electrochemical loading with sodium ions is realized in a specifi c mixture of diethyl carbonate, ethylene carbonate, and fl uoroethylene carbonate electrolyte in order to create a fi rst solid electrolyte interface (SEI) on the anode surface. Combining such anodes with a porous carbon/sulfur composite cathode results in full cells with a signifi cantly decreased polysulfi de shuttle when compared to half cells combined with metallic sodium anodes. Further optimization involves the use of Na 2 S/P 2 S 5 doped tetraethylene glycol dimethyl ether based electrolyte in the full cell for the formation of a second SEI, reducing polysulfi de shuttle even further. More importantly, the electrochemical discharge processes in the cell are improved by adding this dissolved complexation agent to the electrolyte. As a result of this combination sodium-sulfur cells with tailored cathode materials and electrolytes can achieve high discharge capacities up to 980 mAh g −1 sulfur and 1000 cycles with 200 mAh g −1 sulfur remaining capacity, at room temperature.

Improving the Stability of an RT‐NaS Battery via In Situ Electrochemical Formation of Protective SEI on a Sulfur–Carbon Composite Cathode

“…Interestingly, the precycle capacity of untreated NaS with FEC is approximately two times higher than that of untreated NaS without FEC (Figure 3b), presumably because NaF is spontaneously formed on the sulfurcarbon composite cathode before the electrochemical reaction and can temporarily inhibit the initial polysulfide dissolution ( Figure S4, Supporting Information). Compared with previously reported researches (Figure 3f), [10,11,13,16,28,29] ET-NaS with FEC shows outstanding active material utilization and cycling stability at high current density (1 A g −1 ) (Table S1, Supporting Information). Figure 3c shows the charge-discharge profile of untreated NaS and ET-NaS with FEC at 0.4 A g −1 .…”

“…At present, this technology is commercialized for stationary-energy-storage systems because of its reasonable energy density and cost. [9,10] However, RT-NaS still faces critical obstacles to practical use, such as the low electrical conductivity of sulfur, large volume expansion (≈170%), loss of active materials, etc. [7] Additionally, the high-temperature operation results in safety, cost, and efficiency concerns.…”

“…[7] Additionally, the high-temperature operation results in safety, cost, and efficiency concerns. [9][10][11][12] To prevent the shuttle effect, several research studies have reported various attempts: (i) encapsulation with/infiltration into porous carbon, [13] (ii) coating of the cathode with conductive polymers, [14] (iii) formation of multiple metal oxides, [15] and (iv) development of a membrane to impede polysulfide diffusion to the anode. [9,10] However, RT-NaS still faces critical obstacles to practical use, such as the low electrical conductivity of sulfur, large volume expansion (≈170%), loss of active materials, etc.…”

Schwefel‐basierte Elektroden mit Mehrelektronenreaktionen für Raumtemperatur‐Natriumionenspeicherung

“…Sie postulierten einen neuen Festkçrpertransportmechanismus ohne die Bildung lçslicher Polysulfidverbindungen. [57] Zusätzlich zur Physisorption gibt es auch erste Studien von Kohlenstoffkäfigen, welche Su nd/oder Polysulfide fester (chemisorptiv) binden kçnnten. Eine äußerst hohe Kapazität( ca.…”

Electrolyte Decomposition and Electrode Thickness Changes in Li-S Cells with Lithium Metal Anodes, Prelithiated Silicon Anodes and Hard Carbon Anodes

“…Such an electrode combination might even be more promising when strategic lithium is substituted with abundant sodium. 10 The strength of silicon anodes compared to lithium is the higher volumetric energy density in a full cell at the cost of a lower cell voltage and reduced gravimetric energy density. The aim of this work is to provide deeper insights into electrolyte decomposition in Li-S cells with standard electrolyte dependent whether a lithium metal, a prelithiated silicon or a prelithiated carbon anode were applied.…”