Dispersion of coal tar pitch for coating graphitic materials and use in Li-ion battery electrode production
A dispersion, methods of making the same, applications of the dispersion to graphitic material and the resulting coated particles are disclosed. The dispersion includes ≤55% wt. coal tar pitch (softening point 100° C.-95° C.), ≤60% wt. dispersant, and the balance a non-aromatic solvent such as water or alcohol. Pitch particles in the dispersion are preferably ≤10 μm with a distribution of D50<15 μm. The pitch particles are micronized, such as by dry and/or wet milling with the dispersant and aqueous solvent to achieve the desired pitch particle size and distribution. This aqueous dispersion may be mixed with natural or synthetic graphitic material having a diameter of 5-20 μm in a ratio of 5%-30% pitch to graphite, dried and carbonized to form coated particles having a graphitic core at least partially coated by pitch particles.
1. A dispersion of coal tar pitch, comprising:
55% by weight or less coal tar pitch having a softening point in the range of 100° C.-200° C.;
60% by weight or less dispersant being at least one of a cationic surfactant, anionic surfactant, non-ionic surfactant, zwitterionic surfactant, polymeric, co-polymeric, surface-active substance and non-surface active polymer;
a solvent selected from the group consisting of at least one of water, non-aromatic alcohol, aliphatic alcohol, polar solvent, inorganic solvent and aliphatic organic solvent; and
wherein said dispersion has a particle size distribution of D50<15 μm of said coal tar pitch.
2. The dispersion as recited in claim 1 , wherein said dispersion comprises 28-50% by weight coal tar pitch, 8.25-15% by weight dispersant, and a balance said solvent.
3. The dispersion as recited in claim 1 , wherein said coal tar pitch has a softening point in the range of 110° C. to 155° C.
4. The dispersion as recited in claim 1 , wherein said dispersant is selected from the group consisting of:
Class
Description
A
APE-free aqueous general use dispersant (40-100% active)
B
Aqueous general use dispersant (40-100% active)
C
High performance carbon black dispersant
D
Organic general use dispersant (40-100% active)
E
Waterborne anionic dispersant agent
F
Waterborne non-ionic dispersant containing alcohol ethoxylate
G
Defoamer containing tetramethyldecynediol
H
Polymeric dispersant .
5. The dispersion as recited in claim 1 , wherein said dispersion has a particle size distribution of D 50 selected from the group consisting of <9 μm and <5 μm of said coal tar pitch, and a D 90 selected from the group consisting of <19 μm of said coal tar pitch and <10 μm of said coal tar pitch.
6. The dispersion as recited in claim 1 , wherein said dispersion forming an unsettled portion being less than 60% of said dispersion upon settling for 28 days.
7. The dispersion as recited in claim 6 , wherein said dispersion forming a settled portion capable of being resuspended in a time selected from the group consisting of less than 8 minutes at agitation speeds in the range of 600 to 700 cycles per minute; less than or equal to 2 minutes at agitation speeds in the range of 600 to 700 cycles per minute; and in the range of 1 to 3 minutes at agitation of about 700 cycles per minute.
8. The dispersion as recited in claim 7 , wherein said dispersion has a viscosity in the range of 100 to 375 cP and a consistency of up to 20% deviation in viscosity before and after said settled portion is resuspended.
9. The dispersion as recited in claim 1 , wherein said dispersion is capable of creating coated particles having an increased tap density compared to uncoated particles.
10. The dispersion as recited in claim 9 , wherein said dispersion is capable of creating coated particles having an increased tap density selected from the group consisting of in the range of 10% to 30% compared to uncoated particles; in the range of 10% to 15% compared to uncoated particles; in the range of 20% to 25% compared to uncoated particles.
11. The dispersion as recited in claim 1 , wherein said dispersion is capable of creating coated particles having a BET surface area of less than 8 m 2 /g.
12. The dispersion as recited in claim 11 , wherein said dispersion is capable of creating coated particles having a BET surface area selected from the group consisting of less than 5 m 2 /g and less than 3 m 2 /g.
13. The dispersion as recited in claim 1 , wherein said dispersion is capable of producing a battery having a charge capacity in the range of 360-372 mAh/g in the first cycle.
14. The dispersion as recited in claim 1 , wherein said dispersion is capable of producing a battery having an irreversible capacity loss of 7% or less in a first cycle.
15. The dispersion as recited in claim 1 , wherein said softening point of said coal tar pitch is at least 125° C.
16. The dispersion as recited in claim 1 , wherein said dispersion comprises 28-50% by weight coal tar pitch and 8.25-15% by weight dispersant.
17. The dispersion as recited in claim 1 , wherein said dispersion has a particle size distribution D50<10 μm of said coal tar pitch.
18. The dispersion as recited in claim 1 , said coal tar pitch is micronized.
19. A method of making a dispersion of pitch particles, said method comprising:
combining an amount of coal tar pitch particles with an aqueous solvent sufficient to achieve a concentration of 55% by weight or less coal tar pitch particles in said dispersion;
adding an amount of dispersant to said coal tar pitch particles sufficient to achieve a concentration of 60% by weight or less dispersant in said dispersion to form a mixture; and
milling the mixture of said coal tar pitch particles and said dispersant until said coal tar pitch reaches a particle size distribution of D50<15 μm in said dispersion.
20. The method as recited in claim 19 , wherein combining an amount of said coal tar pitch particles further comprises combining an amount of said coal tar pitch particles sufficient to achieve a concentration selected from the group consisting of in the range of 28% to 50% by weight of said coal tar pitch particles in said dispersion; 28% by weight of said coal tar pitch particles in said dispersion; 30% by weight of said coal tar pitch particles in said dispersion; 35% by weight of said coal tar pitch particles in said dispersion; and 50% by weight of said coal tar pitch particles in said dispersion.
21. The method as recited in claim 19 , wherein adding an amount of said dispersant further comprises adding an amount of said dispersant sufficient to achieve a concentration selected from the group consisting of in the range of 8.25% to 15% by weight of said dispersant in said dispersion; 8.25% by weight of said dispersant in said dispersion; 10% by weight of said dispersant in said dispersion; 13% by weight of said dispersant in said dispersion; and 15% by weight of said dispersant in said dispersion.
22. The method as recited in claim 19 , wherein milling the mixture further comprises milling the mixture for a time selected from the group consisting of 30 to 400 minutes;
30 to 135 minutes; 30 to 75 minutes; 30 to 45 minutes; 60 to 75 minutes; and up to 45 minutes.
23. The method as recited in claim 19 , wherein milling the mixture of said coal tar pitch particles and said dispersant occurs in the presence of said aqueous solvent.
24. The method as recited in claim 19 , wherein milling the mixture of said coal tar pitch particles and said dispersant occurs in the absence of said aqueous solvent.
25. A method of applying a dispersion of coal tar pitch to graphitic material, comprising:
combining an amount of a dispersion as recited in claim 1 to an amount of graphitic material in a ratio in the range of 5% to 30% pitch to graphitic material;
mixing said dispersion and said graphitic material to achieve a mixture;
drying said mixture to remove said solvent and contact said coal tar pitch particles with said graphitic material;
carbonizing at temperatures in the range of 1000° C. to 1650° C. to adhere said coal tar pitch particles to a surface of said graphitic material.
26. The method as recited in claim 25 , wherein combining an amount of said dispersion further comprises combining an amount of said dispersion as recited in claim 1 to an amount of said graphitic material in a ratio selected from the group consisting of in the range of 7% to 28% pitch to graphitic material; in the range of 10% to 20% pitch to graphitic material; 8% pitch to graphitic material; 11% pitch to graphitic material; 12% pitch to graphitic material; 14% pitch to graphitic material; 15% pitch to graphitic material; 16% pitch to graphitic material; 18% pitch to graphitic material; and 28% pitch to graphitic material.
27. The method as recited in claim 25 , wherein carbonizing occurs at a temperature selected from the group consisting of about 1100° C. and about 1450° C.
28. The method as recited in claim 25 , wherein said graphitic material is selected from the group consisting of natural graphite and synthetic graphite.
29. The method as recited in claim 25 , wherein a shape of said graphitic material shape-is selected from the group consisting of spherical, spheroidal, ellipsoid and oblong.
30. The method as recited in claim 25 , wherein said graphitic material is of a size selected from the group consisting of in the range of 5 to 20 microns; in the range of 5 to 7 microns;
in the range of 7 to 12 microns; in the range of 10 to 20 microns; and in the range of 10 to 12 microns.
31. Coated particles produced by the method of claim 25 .
32. The coated particles as recited in claim 31 , wherein said dispersion is selected from the group consisting of 28-50% by weight coal tar pitch, 8.25-15% by weight dispersant, and a balance said solvent; 35% by weight coal tar pitch, 10% by weight dispersant and a balance said solvent; 28% by weight coal tar pitch, 8.25% by weight dispersant and a balance said solvent; 50% by weight coal tar pitch, 13% by weight dispersant, and a balance said solvent; and 50% by weight coal tar pitch, 15% by weight dispersant, and a balance said solvent.
33. The coated particles as recited in claim 31 , wherein said coal tar pitch of said dispersion has a softening point selected from the group consisting of in the range of 110° C. to 155° C.; 125° C.; 126.5° C.; 130° C.; and 132° C.
34. The coated particles as recited in claim 31 , wherein said dispersion comprises a particle size distribution of D 50 selected from the group consisting of <9 μm of said coal tar pitch and <5 μm of said coal tar pitch, and a D 90 selected from the group consisting of <19 μm of said coal tar pitch and <10 μm of said coal tar pitch.
35. The coated particles as recited in claim 31 , further comprising a composition selected from the group consisting of a range of 7% to 28% pitch to graphitic material; range of 10% to 20% pitch to graphitic material; 8% pitch to graphitic material; 11% pitch to graphitic material; 12% pitch to graphitic material; 14% pitch to graphitic material; 15% pitch to graphitic material; 16% pitch to graphitic material; 18% pitch to graphitic material; and 28% pitch to graphitic material.
36. The coated particles as recited in claim 31 , wherein said coated particles have a BET surface area selected from the group consisting of less than 8 m 2 /g; less than 5 m 2 /g; and less than 3 m 2 /g.
37. The coated particles as recited in claim 31 , wherein said coated particles have an increased tap density compared to uncoated graphitic material.
38. The coated particles as recited in claim 31 , wherein said coated particles have an increased tap density selected from the group consisting of in the range of 10% to 30% compared to uncoated particles; in the range of 10%-15% compared to uncoated particles; and in the range of 20% to 25% compared to uncoated particles.
39. The coated particles as recited in claim 31 , wherein said coated particles are capable of producing battery having charge capacity in the range of 360-372 mAh/g in a first cycle.
40. The coated particles as recited in claim 31 , wherein said coated particles are capable of producing battery having irreversible capacity loss of 7% or less in a first cycle.