Cathode material and a method of preparing the same
View Patent ↗There is provided a cathode material comprising a layer of sulfur species dispersed within or thereon a porous matrix comprising a first conducting carbon material, a second conducting carbon material and a binder, wherein the second conducting carbon material is carbon fiber or carbon nanotube. There is also provided a cathode material comprising a layer of sulfur species dispersed within or thereon a porous matrix comprising a first conducting carbon material, a second conducting carbon material and a binder, wherein said porous matrix is interconnected with uniform pores. There are also provided methods for preparing the above cathode material(s).
1 . A cathode material comprising a layer of sulfur species dispersed within or thereon a porous matrix comprising a first conducting carbon material, a second conducting carbon material and a binder, wherein the binder is a copolymer of acrylamide, lithium carboxylate and cyano group,
the second conducting carbon material is carbon fiber or carbon nanotube, and
said porous matrix is interconnected with uniform pores.
2 . The cathode material according to claim 1 , wherein the sulfur species is a polysulfide or elemental sulfur.
3 . The cathode material according to claim 1 , where the polysulfide has a formula of Li 2 S n , wherein 2<n≤8.
4 . The cathode material according to claim 1 , wherein the cathode material has a sulfur content in the range of about 30 wt % to about 80 wt % based on the total weight of the cathode material.
5 . The cathode material according to claim 1 , wherein the first conducting carbon material is selected from the group consisting of reduced graphene oxide, graphene, graphite, carbon nanotube, carbon fiber, acetylene black, and ketjenblack; wherein the first conducting carbon material is doped with nitrogen, oxygen, sulfur, boron, phosphorus or their mixtures thereof; or is different from the second conducting material.
6 . The cathode material according claim 1 , wherein the first conducting carbon material is reduced graphene oxide.
7 . The cathode material according claim 1 , wherein the amount of the first conducting carbon material is in the range of 20 wt % to 60 wt % based on the total weight of the cathode material.
8 . The cathode material according claim 1 , wherein the binder is water soluble.
9 . The cathode material according to claim 1 , wherein the amount of the binder is in the range of 5 wt % to 15 wt % based on the total weight of the cathode material.
10 . The cathode material according to claim 1 , wherein the second conducting carbon material is vapor grown carbon fiber (VCGF); or has a diameter in the range of about 0.1 nm to about 100 μm.
11 . The cathode material according to claim 1 , wherein the amount of the second conducting carbon material is in the range of 5 wt % to 35 wt % based on the total weight of the cathode material.
12 . The cathode material according to claim 1 , wherein the cathode material has a sulfur loading density in the range of 1.3 mg cm −2 to 15 mg cm −2 ; a surface area in the range of 200 m 2 /g to 900 m 2 /g; a pore volume in the range of 0.25 cm 3 /g to 3 cm 3 /g; or a pore size distribution of mesopore size in the range of 2.0 nm to 50 nm and macropore size larger than 50 nm.
13 . An electrochemical cell comprising a liquid electrolyte, and a cathode material comprising a layer of sulfur species dispersed within or thereon a porous matrix comprising a first conducting carbon material, a second conducting carbon material and a binder, wherein the binder is a copolymer of acrylamide, lithium carboxylate and cyano group,
the second conducting carbon material is carbon fiber or carbon nanotube, and
said porous matrix is interconnected with uniform pores.
14 . A lithium-sulfur battery comprising one or more electrochemical cells, each electrochemical cell comprising a liquid electrolyte, and a cathode material comprising
a layer of sulfur species dispersed within or thereon a porous matrix comprising a first conducting carbon material, a second conducting carbon material and a binder, wherein the binder is a copolymer of acrylamide, lithium carboxylate and cyano group,
the second conducting carbon material is carbon fiber or carbon nanotube, and
said porous matrix is interconnected with uniform pores.
15 . A method for preparing a cathode material comprising:
a) coating a support with a slurry formed by mixing a mixture of a first conducting carbon material, a second conducting carbon material and a binder, wherein the binder is a copolymer of acrylamide, lithium carboxylate and cyano group, and the second conducting carbon material is carbon fiber or carbon nanotube; and
b) adding a sulfur source in solution or gaseous state to the coated support to form a layer of sulfur species dispersed within or thereon the coated support to thereby obtain the cathode material, wherein the coated support is a porous matrix comprising the first conducting carbon material, the second conducting carbon material and the binder, and said porous matrix is interconnected with uniform pores.
16 . The method according to claim 15 , further comprising, before said coating operation (a), the operation of (a1) stirring said mixture in a solvent overnight with a solid content in the range of 3 wt % to 10 wt %, wherein the solvent is water or water mixture with polar organic solvents.
17 . The method according to claim 15 , wherein the first conducting carbon material is reduced graphene oxide; or has a concentration in the range of 60 wt % to 90 wt % based on the total weight of solid content in the slurry.
18 . The method according to claim 15 , wherein the second conducting carbon material has a concentration in the range of 5 wt % to 50 wt % based on the total weight of solid content.
19 . The method according to claim 15 , wherein the binder has a concentration in the range of 5 wt % to 20 wt % based on the total weight of solid content.
20 . The method according to claim 15 , further comprising, after said coating operation (a), the operation of (a2) drying the coated support at a temperature in the range of 40° C. to 80° C. for more than 2 hours.
21 . The method according to claim 15 , comprising preparing a polysulfide (PS) solution as the sulfur source in fluid state by stirring a mixture of sulfur (S) and lithium sulfide (Li 2 S); wherein the mixture has a S/Li 2 S mass ratio in the range of 2:1 to 5:1; and/or is stirred at a temperature in the range of 40° C. to 60° C. overnight in a glovebox.
22 . The method according to claim 15 , comprising the operation of obtaining said sulfur source in fluid state by heating elemental sulfur solid at a temperature in the range of 160° C. to 190° C. at a duration in the range of 5 minutes to 40 minutes.