Method for producing composite material for positive electrode of lithium battery
The present invention provides a method for producing a composite material for positive electrodes of lithium batteries which is particularly excellent in high-rate discharge characteristics. The method for producing a composite material for positive electrodes of lithium batteries, contains: a dispersing step of dispersing at least the positive electrode active material and the conductive material 1 in a solvent to be in a forcibly dispersed state; and a composite particle-forming step of obtaining composite particles containing the positive electrode active material and the conductive material 1 by a process for agglutinating the conductive material 1 together with the positive electrode active material in the solvent or by a process for removing the solvent.
1. A method for producing a positive electrode for lithium batteries containing a positive electrode active material and a conductive material, the method comprising:
(Step 1): a step of producing a composite material for positive electrodes of lithium batteries,
(Step 2): a step of obtaining a slurry containing the composite material for positive electrodes of lithium batteries obtained in Step 1, a solvent, a conductive material and a binder,
(Step 3): a step of applying the slurry obtained in Step 1 onto a current collector, and
(Step 4): a step of drying the current collector having the slurry applied thereto and obtained in Step 3,
wherein Step 1 further comprises:
(Step 1-1): a dispersing step of dispersing at least the positive electrode active material and the conductive material 1 in a solvent to be in a forcibly dispersed state; and
(Step 1-2): a composite particle-forming step of obtaining composite particles containing the positive electrode active material and the conductive material 1 by a process for agglutinating the conductive material 1 together with the positive electrode active material in the solvent, wherein
a conductive material having autoagglutination in the solvent is used as the conductive material 1,
the content of the conductive material 1 is 0.2 to 5 parts by weight relative to 100 parts by weight of the positive electrode material, and
the forcibly dispersed state is a dispersion state where when a slurry is sampled and diluted to a predetermined concentration, and an average particle diameter is promptly measured by a particle size distribution measuring device, the average diameter does not surpass 130% of a primary particle diameter of the positive electrode active material.
2. The method according to claim 1 , wherein a conductive material containing carbon black having a DBP absorption amount of 200 to 800 cm 3 /100 g and/or fibrous carbon having an aspect ratio of 50 to 1000 is used as the conductive material 1, and the composite particle-forming step agglutinates the conductive material 1 together with the positive electrode active material in the solvent to obtain the composite particles.
3. The method according to claim 2 , wherein the conductive material 1 contains ketjen black having a DBP absorption amount of 200 to 800 cm 3 /100 g.
4. The method according to claim 2 , wherein the fibrous carbon has a fiber diameter of 1 nm to 1 μm.
5. The method according to claim 1 , wherein the positive electrode active material has a primary particle diameter of 0.1 to 10 μm.
6. The method according to claim 1 , wherein the dispersing step disperses carbon black having a DBP absorption amount of less than 200 cm 3 /100 g together with the conductive material 1.
7. The method according to claim 1 , wherein the composite material for positive electrodes from which the solvent is distilled has a volume resistivity of 3 Ω·cm or less.
8. The method according to claim 1 , wherein the composite material for positive electrodes from which the solvent is distilled has a total pore capacity of 0.8 cc/g or more.
9. The method according to claim 1 , wherein the positive electrode active material has a primary particle diameter of 0.5 to 10 μm.
10. The method according to claim 1 , wherein the solvent in Step 2 is N-methyl-2-pyrolidone.
11. The method according to claim 1 , wherein the binder in Step 2 is polyvinylidene difluoride.
12. The method according to claim 1 , wherein the conductive material 1 is carbon black having a DBP absorption amount of 200 to 600 cm 3 /100 g and/or fibrous carbon having an aspect ratio of 50 to 600.
13. A method for producing a positive electrode for lithium batteries containing a positive electrode active material and a conductive material, the method comprising:
(Step 1): a step of producing a composite material for positive electrodes of lithium batteries,
(Step 2): a step of obtaining a slurry containing the composite material for positive electrodes of lithium batteries obtained in Step 1, a solvent, and a binder,
(Step 3): a step of applying the slurry obtained in Step 1 onto a current collector, and
(Step 4): a step of drying the current collector having the slurry applied thereto and obtained in Step 3,
wherein Step 1 further comprises:
(Step 1-1): a dispersing step of dispersing at least the positive electrode active material and the conductive material 1 in a solvent in a forcibly dispersed state;
(Step 1-2): a composite particle-forming step of obtaining composite particles containing the positive electrode active material and the conductive material 1 by a process for removing the solvent; and
(Step 1-3): a mixing step of mixing at least the composite particles and a conductive material 2 having an aspect ratio of 2 to 10 after the composite particle-forming step, wherein
the content of the conductive material 1 is 0.2 to 5 parts by weight relative to 100 parts by weight of the positive electrode material, and
the forcibly dispersed state is a dispersion state wherein when a slurry is sampled and diluted to a predetermined concentration, and an average particle diameter is promptly measured by a particle size distribution measuring device, the average diameter does not surpass 130% of a primary particle diameter of the positive electrode active material.
14. The method according to claim 13 , wherein the conductive material 1 is carbon black having a primary particle diameter of 10 to 100 nm.
15. The method according to claim 13 , wherein the solvent has a boiling point of 100° C. or less.
16. The method according to claim 13 , wherein the obtained composite material for positive electrodes has a volume resistivity of 5 Ω·cm or less.
17. The method according to claim 13 , wherein the compounding amount of the conductive material 2 is 2 to 15 parts by weight relative to 100 parts by weight of the positive electrode active material.
18. The method according to claim 13 , wherein the conductive material 2 has the aspect ratio of 2 to 5.
19. The method according to claim 13 , wherein the conductive material 2 has the aspect ratio of 2 to 5 and a DBP absorption amount of 100 to 500 cm 3 /100 g.
20. A method for producing a positive electrode for lithium batteries containing a positive electrode active material and a conductive material, the method comprising:
(Step 1): a step of producing a composite material for positive electrodes of lithium batteries,
(Step 2): a step of obtaining a slurry containing the composite material for positive electrodes of lithium batteries obtained in Step 1, a solvent, and a binder,
(Step 3): a step of applying the slurry obtained in Step 1 onto a current collector, and
(Step 4): a step of drying the current collector having the slurry applied thereto and obtained in Step 3,
wherein Step 1 further comprises:
(Step 1-1): a dispersing step of dispersing at least the positive electrode active material and the conductive material 1 in a solvent in a forcibly dispersed state;
(Step 1-2): a composite particle-forming step for obtaining composite particles containing the positive electrode active material and the conductive material 1 by a process that comprises removing the solvent; and
(Step 1-3): a mixing step of mixing at least the composite particles and a conductive material 2 having a DBP absorption amount of 100 to 500 cm 3 /100 after the composite particle-forming step, wherein
the content of the conductive material 1 is 0.2 to 5 parts by weight relative to 100 parts by weight of the positive electrode material, and
the forcibly dispersed state is a dispersion state where when a slurry is sampled and diluted to a predetermined concentration, and an average particle diameter is promptly measured by a particle size distribution measuring device, the average diameter does not surpass 130% of a primary particle diameter of the positive electrode active material.
21. The method according to claim 20 wherein the compounding amount of the conductive material 2 is 2 to 15 parts by weight relative to 100 parts by weight of the positive electrode active material.