Formation of slurry for high loading sulfur cathodes
A high density slurry comprising encapsulated sulfur particles, carbon nanofibers and activated carbon black suitable for use in forming the active material of an electrode. A method for forming the high density sulfur slurry is also provided. A cathode containing the particles and a battery constructed with the cathode as well as methods for their formation are also provided.
1. A slurry, comprising:
encapsulated chalcogen particles, comprising a chalcogen core and an encapsulate coating disposed on the chalcogen core surface consisting of at least one polymer having both hydrophobic regions and hydrophilic regions;
carbon nanofibers;
carbon black;
carboxymethyl cellulose;
styrene butadiene rubber; and
water;
wherein
a sulfur content of the encapsulated chalcogen particles is greater than 90 wt % relative to the total dry weight of the encapsulated chalcogen particles,
a content of sulfur is greater than 85 wt % relative to a total dry weight of the slurry; and
a ratio of carbon nanofibers to carbon black is 3:1.
2. The slurry of claim 1 , wherein a total content of the carbon nanofiber and carbon black is less than 10 wt % relative to the total dry weight of the slurry.
3. The slurry of claim 1 , wherein a total content of the carboxymethyl cellulose and styrene butadiene rubber is less than 5 wt % relative to the total dry weight of the slurry.
4. The slurry of claim 1 , wherein a ratio of carboxymethyl cellulose to styrene butadiene rubber is 3:1.
5. The slurry of claim 1 , wherein water is present in an amount equal to 0.25-1.25 times the total dry weight of the slurry.
6. The slurry of claim 1 , wherein the chalcogen core further comprises at least one of selenium and tellurium.
7. The slurry of claim 1 , wherein the polymer coating consists of at least one polymer selected from the group consisting of poly (3,4-ethylenedioxythiophene) polystyrene sulfonate, polyvinylpyrrolidone, polyaniline, poly(ethylene oxide), carboxymethyl cellulose, sodium carboxymethyl cellulose, polymethacrylic acid, poly(2-acrylamido-2-methyl-1-propanesulfonic acid), branched polyethylenimine, and poly(diallyl dimethylammonium chloride).
8. The slurry of claim 6 , wherein a selenium content or a tellurium content of the encapsulated chalcogen particles is less than 50 wt % relative to a total weight of the encapsulated chalcogen particles.
9. The slurry of claim 6 , wherein the encapsulated chalcogen core further comprises carbon black particles, functionalized carbon black particles or both which are homogeneously dispersed in the chalcogen core.
10. A method for forming the slurry of claim 1 , comprising:
forming a powder mixture comprising 90 wt % of the encapsulated chalcogen particles relative to the total dry weight of the slurry and 8 wt % of carbon nanofibers and carbon black together relative to the total dry weight of the slurry;
grinding the powder mixture to form a powder of carbon and active material;
adding a weight corresponding to 2 wt % of carboxymethyl cellulose and styrene butadiene rubber together relative to the total dry weight of the slurry to the powder of carbon and active material to form a thick slurry;
adding water to the thick slurry;
mixing the thick slurry to form the slurry.
11. The method of claim 10 , wherein water is added in an amount of 0.4-1.2 mL per g of the thick slurry.
12. The method of claim 10 , wherein the mixing is performed by planetary centrifugation for up to 15 minutes at a speed of greater than 1000 rpm.
13. The method of claim 10 , further comprising ball milling the fine powder of carbon and active material for up to 2 hours at a speed of less than 200 rpm.
14. An electrode, comprising:
the dried slurry of claim 1 as active material; and
a current collector;
wherein the dried slurry is on a surface of the current collector.
15. The electrode of claim 14 , wherein a sulfur weight per current collector area is in the range of 3-8 mg/cm 2 .
16. The electrode of claim 14 , wherein the current collector comprises aluminum.
17. A method for forming the electrode of claim 14 , comprising:
pouring the slurry onto the current collector
forming a wet gap of less than 200 μm to obtain a green electrode;
drying the green electrode; and
calendering the dried green electrode to form the electrode.
18. The method of claim 17 , wherein the drying is performed in an oven at a temperature of up to 100° C. for up to 12 hours.
19. The method of claim 17 , wherein the dried green electrode is calendered such that the electrode has less than 50% of the thickness of the dried green electrode.
20. A battery, comprising:
the electrode of claim 14 as a cathode;
an anode; and
an electrolyte in a solvent.
21. The battery of claim 20 , wherein the anode comprises a metal selected from the group consisting of an alkali metal and an alkaline earth metal.
22. The battery of claim 20 , wherein the anode is lithium and the electrolyte comprises LiTFSI and LiNO 3 in a molar ratio of 5:1.
23. The battery of claim 22 , wherein the solvent comprises glyme and dioxolane in a weight ratio of 1:1.
24. The battery of claim 20 , wherein the anode is lithium and the anode is pretreated with a lithium polysulfide.
25. A vehicle comprising the battery of claim 20 .