Method for preparing a positive electrode material through extrusion in presence of an aqueous solvent, positive electrode obtained through said method, and uses thereof

Patent metadata

Field	Value
Publication number	US-9450231-B2
Application number	US-201013389286-A
Country	US
Kind code	B2
Filing date	Sep 8, 2010
Priority date	Sep 9, 2009
Publication date	Sep 20, 2016
Grant date	Sep 20, 2016

Abstract

The present invention relates to a method for preparing a positive electrode that is made up of a composite material containing at least one active positive electrode made of iron and phosphate and at least one water-soluble polymer having ionic conduction properties in the presence of a lithium salt, said method comprising at least one step for mixing ingredients of the composite material through extrusion so as to obtain an extruded composite material and wherein said extrusion step is carried out by means of a co-kneader or extruder in the presence of an aqueous solvent and at a temperature from 20° to 95° C. The invention also relates to the positive electrode obtained according to said method, to the use of said electrode for manufacturing a lithium battery, and to the lithium battery having such electrode built therein. The electrode is particularly characterized in that it contains a level of active material greater than 60 wt %.

First claim

The invention claimed is:

1. A process for producing a positive electrode including an active positive-electrode material of LiFePO 4 ,
said active positive-electrode material made from a composite having:
at least one water-soluble polymer that conducts ions in the presence of a lithium salt;
at least one lithium salt; and
optionally at least one material providing electrical conduction properties,

said process comprising the steps of:
(1) mixing, by extrusion, the ingredients of the composite so as to obtain an extruded composite;
(2) forming the composite extruded through a die;
(3) rolling or calendering the extruded composite into the form of a positive electrode film on a current collector; and,
(4) drying the positive-electrode film applied to the current collector,
wherein the extrusion step is carried out via an extruder in the presence of an aqueous solvent,
said aqueous solvent having any one of
(a) demineralized water,
(b) distilled water or
(c) a mixture of demineralized or distilled water and at least one water-miscible solvent representing at most 30 wt % of the total weight of the aqueous solvent,

said aqueous solvent representing approximately from 3 to 25 wt % of the total weight of the ingredients forming the composite, and
at a temperature from 20 to 95° C.,

wherein the water-soluble polymer is selected from the group consisting of polyoxyethylene, polyoxypropylene, polyoxybutylene, polyoxyethylene-based copolymers, polyoxypropylene-based copolymers, polyoxybutylene-based copolymers, polyoxyethylene based terpolymers, polyoxypropylene-based terpolymers, and polyoxybutylene-based terpolymers,
wherein the lithium salt is selected from the group consisting of LiTFSI, LiClO 4 and LiBETI, and
wherein said aqueous solvent is of a composition that is sufficient to reduce the viscosity of the composite so that it is extruded below 95° C. such that said positive electrode film includes at least 60% active material while the positive-electrode film being 100μm or less in thickness.

2. The process as claimed in claim 1 , wherein the extrusion step is carried out at a temperature from 35 to 80° C.

3. The process as claimed in claim 1 , wherein the extrusion step is carried out by means of a. twin-screw extruder.

4. The process as claimed in claim 3 , wherein the twin-screw extruder is a corotating twin-screw extruder.

5. The process as claimed in claim 4 , wherein the twin-screw extruder comprises a sectional, modular barrel of about ten blocks in succession, each block being individually controlled to a specific selected temperature and in Which blocks two parallel screws rotate, a variable-speed gearmotor driving the screws, one or more variable feed rate supply devices intended to supply the extruder with the ingredients making up the composition of the electrode composite, a system for introducing the liquid aqueous solvent, and optionally one or more side feeders, said twin-screw extruder furthermore being equipped with multiple hoppers, with one or more specific barrel assemblies dedicated to the optional connection of one or more liquid injection nozzles, and optionally with one or more barrel assemblies intended to receive the one or more connections of a side feeder.

6. The process as claimed in claim 1 , wherein the water-miscible solvent is chosen from methanol, ethanol, propanol, butanol and glycols.

7. The process as claimed in claim 1 , wherein when it is present, the water-miscible solvent represents less than least 15 wt % of the total weight of the aqueous solvent.

8. The process as claimed in claim 1 , wherein the amount of aqueous solvent used in the extrusion step varies from 8 to 15 wt % of the total weight of the ingredients forming the composite.

9. The process as claimed in claim 1 , further comprising a device for increasing and stabilizing pressure is positioned at the outlet of the extruder, in front of the die.

10. The process as claimed in claim 9 , wherein said device is a single-screw rework extruder having a temperature profile of 20 to 95° C.

11. The process as claimed in claim 1 , wherein the die is a flat die.

12. The process as claimed in claim 1 , wherein the rolling or calendering step is carried out in rolling or calendering equipment of two rollers that rotate in opposite directions.

13. The process as claimed in claim 1 , wherein the drying step is carried out in line.

14. The process as claimed in claim 1 , wherein the active positive-electrode material, the water-soluble polymer and the material providing electrical conduction properties are each contained in different feeders and introduced, in succession and/or simultaneously, into zones of the extruder, downstream or upstream of the zone for introducing the aqueous solvent.

15. The process as claimed in claim 1 , wherein the aqueous solvent is injected directly into the extruder, by means of a liquid injection pump.

16. The process as claimed in claim 1 , wherein the extrusion is carried out at a feed rate of 2 to 200 kg of the mixture of the ingredients (solid content) of the composition of the electrode material per hour.

17. The process as claimed in claim 1 , wherein the active electrode material is LiFePO 4 in the form of uncoated particles or particles comprising a carbonaceous coating.

18. The process as claimed in claim 1 , wherein the active electrode material represents approximately 60 to 85 wt % of the total weight of the ingredients of the composition of the composite in the solid state.

19. The process as claimed in claim 1 , wherein the water-soluble polymer takes the form selected from the group consisting of a powder, of granules and an aqueous dispersion.

20. The process as claimed in claim 1 , wherein the water-soluble polymer represents from 10 to 30 wt % of the total weight of the ingredients of the composition of the composite in the solid state.

21. The process as claimed in claim 1 , wherein the material providing electrical conduction properties is carbon and is selected from the group consisting of carbon blacks, carbon nanotubes, graphite and mixtures of these materials.

22. The process as claimed in claim 1 , wherein the material providing electrical conduction properties is an aqueous dispersion of carbon black or of graphite.

23. The process as claimed in claim 1 , wherein the final content of lithium salt varies from 3 to 10 wt % of the total weight of the electrode composite after drying of the film.

24. The process as claimed in claim 1 , wherein the aqueous solvent used in the extrusion step contains said lithium salt in solution.

25. The process as claimed in claim 1 , wherein the rolling or calendering step is carried out directly on at leas one of the two faces of a current collector, via action on the composite as it is extruded from the die.

26. The process as claimed in claim 1 , wherein the current collector for the positive electrode is an aluminum foil having a thickness ranging from 4 μm to 30 μm.

27. The process as claimed in claim 1 , wherein the step of drying the film applied to the current collector is carried out by convective heating in a drying oven.

28. The process as claimed in claim 1 , wherein the extrusion step is carried out by a co-kneader extruder.

29. The process as claimed in claim 1 , wherein the extrusion step is carried out by a multi-screw extrude

Assignees

• Madray Sophie
• Deschamps Marc
• Kerdranvat Stéphane
• Blue Solutions

Inventors

• Madray Sophie
• Deschamps Marc
• Kerdranvat Stéphane

Classifications

• H01M4/0404

  by coating on electrode collectors · CPC title

• H01M4/1397

  of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy · CPC title

• H01M4/0435

  Rolling or calendering · CPC title

• H01M4/136 Primary

  Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy · CPC title

• H01M4/0411 Primary

  by extrusion · CPC title