Graphene oxide as a sulfur immobilizer in high performance lithium/sulfur cells

Patent metadata

Field	Value
Publication number	US-9853284-B2
Application number	US-201715498113-A
Country	US
Kind code	B2
Filing date	Apr 26, 2017
Priority date	Sep 30, 2011
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

The loss of sulfur cathode material as a result of polysulfide dissolution causes significant capacity fading in rechargeable lithium/sulfur cells. Embodiments of the invention use a chemical approach to immobilize sulfur and lithium polysulfides via the reactive functional groups on graphene oxide. This approach obtains a uniform and thin (˜tens of nanometers) sulfur coating on graphene oxide sheets by a chemical reaction-deposition strategy and a subsequent low temperature thermal treatment process. Strong interaction between graphene oxide and sulfur or polysulfides demonstrate lithium/sulfur cells with a high reversible capacity of 950-1400 mAh g −1 , and stable cycling for more than 50 deep cycles at 0.1 C.

First claim

What is claimed is:

1. A method of preparing a graphene oxide-sulfur (GO—S) nanocomposite comprising:
providing a graphene oxide (GO) dispersion;
adding a sodium polysulfide solution to the GO dispersion to form a blended solution;
titrating the GO/sodium polysulfide blended solution into a HCOOH solution to form a precipitate; and
heat treating, for a specified time and temperature, the precipitate in a sealed vessel utilizing a flowing gas at a specified gas flow rate.

2. The method of claim 1 , wherein the flowing gas is argon.

3. The method of claim 1 , wherein the gas flow rate is approximately 200 cc S −1 .

4. The method of claim 1 , wherein the temperature is approximately 155° C.

5. The method of claim 1 , wherein the time is approximately 12 hours.

6. The method of claim 1 , wherein the sodium polysulfide solution is added to the GO dispersion in the presence of 5 wt % surfactant cetyl trimethylammonium bromide (CTAB).

7. The method of claim 1 , wherein the sodium polysulfide solution is prepared by adding Na 2 S into a flask that has been filled with distilled water to form a Na 2 S solution, then elemental S is suspended in the Na 2 S solution, wherein the ratios of Na 2 S and elemental S, are adjusted to determine a value of x in Na 2 S x of the sodium polysulfide solution.

8. The method of claim 7 , wherein the GO after the heat treatment comprises approximately 50-90 wt % S.

9. The method of claim 8 , wherein the GO after the heat treatment comprises approximately 60-70 wt % S.

10. The method of claim 1 , wherein the graphene oxide (GO) dispersion is prepared by exfoliating GO from a graphite oxide.

11. The method of claim 10 , wherein the graphite oxide was prepared using a modified Hummers method.

Assignees

• Univ California

Inventors

• Zhang Yuegang
• Cairns Elton J
• Ji Liwen
• Rao Mumin

Classifications

• H01M50/417

  Polyolefins · CPC title

• C01P2006/40

  Electric properties · CPC title

• C01B31/26

  Chemistry & Metallurgy · mapped topic

• C01P2004/04

  obtained by TEM, STEM, STM or AFM · CPC title

• C01P2004/03

  obtained by SEM · CPC title