Composite Anode and Lithium-Ion Battery Comprising Same and Method for Producing the Composite Anode

Abstract

A composite anode is provided which includes a collector, an active anode material, a binder, a solid inorganic lithium-ion conductor and a liquid electrolyte. The solid inorganic lithium ion conductor is present in the composite anode in a higher volume and weight proportion than the liquid electrolyte. A method for forming the composite anode is also provided, and a lithium ion battery is provided which includes a composite anode having a collector, an active anode material, a binder, a solid inorganic lithium ion conductor and a liquid electrolyte.

Claims

1. A composite anode comprising: a collector, an active anode material, a binder, a solid inorganic lithium ion conductor, and a liquid electrolyte, wherein the solid inorganic lithium ion conductor is present in the composite anode in a higher volume fraction and weight fraction than the liquid electrolyte.

2. The composite anode according to claim 1, wherein the composite anode has interconnected pores and the pores comprise the solid inorganic lithium-ion conductor and the liquid electrolyte.

3. The composite anode according to claim 1, wherein the composite anode has a porosity of 5% to 25% based on the volume without the liquid electrolyte, and wherein the porosity is filled with the liquid electrolyte to an extent of more than 90%.

4. The composite anode according to claim 3, wherein the porosity is filled with the liquid electrolyte to an extent of more than 95%.

5. The composite anode according to claim 3, wherein the porosity is completely filled with the liquid electrolyte.

6. The composite anode according to claim 1, wherein the active anode material and the solid inorganic lithium ion conductor each comprise particles, and wherein the particles of the active anode material has a greater average particle size D50 than the particles of the solid inorganic lithium ion conductor.

7. The composite anode according to claim 6, wherein the particles of the active cathode material has a 5 to 1000 times greater average particle size D50 than the particles of the solid inorganic lithium ion conductor.

8. The composite anode according to claim 1, wherein the active electrode material comprises secondary particles having the particle size D50 of more than 3 μm to 75 μm.

9. The composite anode according to claim 1, wherein the solid inorganic lithium ion conductor comprises particles having the particle size D50 of more than 0.05 μm to 5 μm.

10. The composite anode according to claim 1, wherein the solid inorganic lithium ion conductor is present at 10 to 80 wt % in the composite anode in relation to the active anode material.

11. The composite anode according to claim 1, wherein the solid inorganic lithium ion conductor is present at 20 to 60 wt % in the composite anode in relation to the active anode material.

12. The composite anode according to claim 1, wherein the active anode material is selected from the group consisting of synthetic graphite, natural graphite, carbon, lithium titanate, and mixtures thereof.

13. The composite anode according to claim 1, wherein the solid inorganic lithium ion conductor has a lithium ion conductivity of at least 10.sup.−5 S/cm at room temperature.

14. The composite anode according to claim 1, wherein the solid inorganic lithium ion conductor is selected from the group consisting of Perovskite, glass formers, Garnet, and mixtures thereof.

15. The composite anode according to claim 1, wherein the binder is selected from the group consisting of polyvinylidene fluoride, copolymer of polyvinylidene fluoride and hexafluoropropylene, copolymer of styrene and butadiene, cellulose, cellulose derivatives, and mixtures thereof.

16. The composite anode according to claim 1, wherein the liquid electrolyte comprises organic carbonates and a conducting salt.

17. The composite anode according to claim 16, wherein the conducting salt is LiPF.sub.6 or LiBF.sub.4.

18. A lithium ion battery comprising: electrodes, a separator, and an electrolyte, wherein one of the electrodes is a composite anode comprising a collector, an active anode material, a binder, an inorganic solid lithium ion conductor, and a liquid electrolyte.

19. A method for producing a composite anode having a collector, an active anode material, a binder, an inorganic solid lithium ion conductor, and a liquid electrolyte, the method comprising the steps of: combining at least the active anode material, the binder in solution with a solvent, and solid inorganic lithium ion conductor to form a homogeneous slurry; applying the slurry to a collector; stripping off the solvent under reduced pressure and/or elevated temperature, forming a porosity in the slurry; adjusting the porosity by calendaring; and filling up the porosity with the liquid electrolyte.

Description

EXAMPLES

[0062] Working Examples of an Anode:

[0063] Reference Anode:

[0064] Dissolved at room temperature in 90 ml of demineralized water is 1.0 g of cellulose binder (Wollf cellulose). Then, using a dissolver disk, 1.0 g of conductive carbon black (Super C65, from Timcal) is introduced. Next, 96.0 g of synthetic graphite (MAG D20; from Hitachi) are incorporated by dispersion and lastly, 2.0 g of SBR binder (from ZEON Corp., Japan) are added. This gives a homogeneous suspension, which with a semiautomatic film-drawing apparatus to a copper support foil (Schlenk, 10 μm rolled copper foil). Stripping off the water results in a composite anode film. After calendering (compression) of the anode film, the resulting porosity is 34% (based on volume), corresponding to a thickness of the anode (without current collector) of 50 μm.

[0065] Inventive Anode:

[0066] Dissolved at room temperature in 90 ml of demineralized water is 1.0 g of cellulose binder (Wolff cellulose). Then, using a dissolver disk, 1.0 g of conductive carbon black (Super C65, from Timcal) is introduced. Next, 64.0 g of LLZ garnet (average particle diameter 1 μm) and 96.0 g of synthetic graphite (MAG D20; from Hitachi) are incorporated by dispersion and lastly, 2.0 g of SBR binder (from ZEON Corp., Japan) are added. This gives a homogeneous suspension, which with a semiautomatic film-drawing apparatus to a copper support foil (Schlenk, 10 μm rolled copper foil). Stripping off the water results in a composite anode film. After calendering (compression) of the inventive anode film with ceramic Li-ion conductor, the resulting porosity is 16% (based on volume), corresponding to a thickness of the anode (without current collector) of 50 μm.

[0067] Working Examples of a Cell

[0068] For further cell construction, a cathode with weight per unit area of 14.0 mg/cm.sup.2 is used (4.5 g of PVdF (from Solvay), 4.5% Super C65, 91% lithium nickel cobalt manganese oxide (NCM111; from BASF)), and was coated onto a 15 μm aluminum foil (Hydro-Aluminum). The separator used is a 25 μm-thick polyolefin separator with the sequence PP/PE/PP. The liquid electrolyte used is a 1.1 M solution of LiPF.sub.6 in EC:DEC (3:7 v/v), which penetrates into the free volume (pores) of the anode, the cathode, and the separator. From the respective electrode/separator assemblies, an Li-ion cell with 2.0 Ah nominal capacity is constructed in stacked design. In each case 20 reference cells with reference anode and 20 inventive cells with inventive anode are built.

[0069] Results of Long-Term Cycling

[0070] On long-term RT cycling (voltage range 2.8 V to 4.2 V (1 C, CCCV charging, 1 C CC discharging), behavior observed is identical to that of a batch of 5 reference cells and inventive cells:

[0071] After 500 cycles, 80% of the initial capacity (2 Ah) is achieved.

[0072] Safety Tests

[0073] 10 cells each (reference and inventive) are subjected in the fully charged state (4.2 V) to a Sandia nail test (“penetration test”, SANDIA REPORT, SAND2005-3123, Unlimited Release Printed August 2006 on page 18f; see http://prod.sandia.gov/techlib/access-control.cgi/2005/053123.pdf). The cells are punctured here with a nail 3 mm thick.

[0074] The results of the tests were evaluated on the basis of the EUCAR Hazard Levels in table 2 on page 15f. of the Sandia Report. Safety level 3 signifies emergence of less than 50 wt % of liquid electrolyte without inflammation or explosion. Safety level 4 corresponds to the previous safety level, but more than 50 wt % of liquid electrolyte emerges. In the case of safety level 5, additionally, there is inflammation of the cells.

TABLE-US-00001 TABLE 1 Results of the safety tests Observed cells of Observed cells of Observed cells of Safety level 3 Safety level 4 Safety level 5 Reference cell 0 9 1 Inventive cell 10 0 0

[0075] Result: The Inventive Cells Exhibit Better Safety Behavior.

[0076] The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.