Electrode containing silicon and copolymer having ionic ally conductive polymer and electrically conductive polymer, and battery cell using same

Abstract

An electrode for a battery cell, including an active material which contains silicon and which contains a first polymer which is ionically conductive. The active material contains in this case a copolymer, which includes the first polymer and a second polymer, the second polymer being electrically conductive. A battery cell which includes at least one electrode is also described.

Claims

1. An electrode for a battery cell, including an active material which contains: at least one of silicon and an alloy including silicon, a first polymer which is ionically conductive, a copolymer which includes the first polymer and a second polymer, the second polymer being electrically conductive, wherein the at least one of the silicon and the alloy including silicon is embedded as grains in the copolymer so as to prevent contact between an electrolyte in the battery cell and the grains of the at least one of the silicon and the alloy including silicon, wherein: the at least one of silicon and the alloy including silicon includes a plurality of grains of at least one of silicon and the alloy including silicon, the second polymer includes a plurality of blocks, and at least one of the plurality of blocks of the second polymer contacts a first and a second of the grains such that the at least one of the blocks serves as an electronically conductive bridge between the first and the second grains.

2. The electrode as recited in claim 1, wherein the electrode is an anode of the battery cell.

3. The electrode as recited in claim 1, wherein the first polymer contains polyethylene oxide.

4. The electrode as recited in claim 1, wherein the second polymer contains one of polyaniline (PAM) or polypyrrole (PPY).

5. The electrode as recited in claim 1, wherein the active material contains carbon.

6. The electrode as recited in claim 1, wherein the at least one of the silicon and the alloy including silicon is embedded in the copolymer as one of nanometer grains and micrometer grains.

7. The electrode as recited in claim 1, wherein at least some of the silicon grains are disposed in the active material in direct contact with the first polymer and the second polymer.

8. The electrode as recited in claim 1, wherein the alloy contains an active metal which is able to take up lithium ions.

9. The electrode as recited in claim 8, wherein the active metal includes one of aluminum, magnesium, and tin.

10. The electrode as recited in claim 1, wherein the alloy contains an inactive metal which is not able to take up lithium ions.

11. The electrode as recited in claim 10, wherein the inactive metal includes one of iron, titanium, and copper.

12. A battery cell, including at least one electrode, the electrode including an active material which contains silicon and a first polymer which is ionically conductive, wherein the active material contains a copolymer which includes the first polymer and a second polymer, the second polymer being electrically conductive, wherein the silicon is embedded as grains in the copolymer so as to prevent contact between an electrolyte in the battery cell and the grains of the silicon, wherein: the silicon includes a plurality of grains of silicon, the second polymer includes a plurality of blocks, and at least one of the plurality of blocks of the second polymer contacts a first and a second of the grains such that the at least one of the blocks serves as an electronically conductive bridge between the first and the second grains.

13. The battery cell as recited in claim 12, wherein the silicon is embedded in the copolymer as one of nanometer grains and micrometer grains.

14. The battery cell as recited in claim 12, wherein at least some of the silicon grains are disposed in the active material in direct contact with the first polymer and the second polymer.

15. A method of using a battery cell, comprising: providing a battery cell in one of an electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, the battery cell including at least one electrode, the electrode including an active material which contains silicon and a first polymer which is ionically conductive, wherein the active material contains a copolymer which includes the first polymer and a second polymer, the second polymer being electrically conductive, wherein the silicon is embedded as grains in the copolymer so as to prevent contact between an electrolyte in the battery cell and the grains of the silicon; and using the battery cell in the electric vehicle, the hybrid electric vehicle, or the plug-in hybrid electric vehicle, wherein: the silicon includes a plurality of grains of the silicon, the second polymer includes a plurality of blocks, and at least one of the plurality of blocks of the second polymer contacts a first and a second of the grains such that the at least one of the blocks serves as an electronically conductive bridge between the first and the second grains.

16. The method as recited in claim 15, wherein the silicon is embedded in the copolymer as one of nanometer grains and micrometer grains.

17. The method as recited in claim 15, wherein at least some of the silicon grains are disposed in the active material in direct contact with the first polymer and the second polymer.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Specific embodiments of the present invention are explained in greater detail below based on the figures.

(2) FIG. 1 shows a schematic representation of a battery cell.

(3) FIG. 2 shows a section through an anode in a schematic representation which is not true to scale.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

(4) A battery cell 2 includes a cell housing 3 which is prismatic, cuboid-shaped in the present case. In the present case, cell housing 3 is electrically conductive and made of aluminum, for example. Battery cell 2 includes a negative terminal 11 and a positive terminal 12. A voltage made available by battery cell 2 may be picked off via terminals 11, 12. Furthermore, battery cell 2 may also be charged via terminals 11, 12. Terminals 11, 12 are situated spaced apart from one another on a cover surface of prismatic cell housing 3.

(5) Within cell housing 3 of battery cell 2, an electrode coil is situated which has two electrodes, i.e., one anode 21 and one cathode 22. Anode 21 and cathode 22 are each designed in a foil-like manner and wound to form an electrode coil by inserting a separator 18 in-between. It is also possible that several electrode coils are provided in cell housing 3.

(6) Anode 21 includes an anodic active material 41 which is designed in a foil-like manner. Anodic active material 41 has silicon 60 or an alloy containing silicon 60 as its basic material. Anode 21 furthermore includes a current collector 31 which is also designed in a foil-like manner. Anodic active material 41 and current collector 31 are situated planarly to one another and connected to one another.

(7) Current collector 31 of anode 21 is electrically conductive and made of a metal, e.g., copper. Current collector 31 of anode 21 is electrically connected to negative terminal 11 of battery cell 2.

(8) Cathode 22 includes a cathodic active material 42 which is designed in a foil-like manner. Cathodic active material 42 has a metal oxide, e.g., lithium cobalt oxide (LiCoO.sub.2), as its basic material. Cathode 22 furthermore includes a current collector 32 which is also designed in a foil-like manner. Cathodic active material 42 and current collector 32 are situated planarly to one another and connected to one another.

(9) Current collector 32 of cathode 22 is electrically conductive and made of a metal, e.g., aluminum. Current collector 32 of cathode 22 is electrically connected to positive terminal 12 of battery cell 2.

(10) Anode 21 and cathode 22 are separated from one another with the aid of separator 18. Separator 18 is also designed in a foil-like manner. Separator 18 is electrically insulating, but ionically conductive, i.e., permeable to lithium ions.

(11) Cell housing 3 of battery cell 2 is filled with a liquid electrolyte 15. Electrolyte 15 surrounds anode 21, cathode 22, and separator 18. Electrolyte 15 is also ionically conductive.

(12) Anodic active material 41 of anode 21 of battery cell 2 has a copolymer 50 which includes a first polymer 51 and a second polymer 52. First polymer 51 and second polymer 52 of copolymer 50 form, in this case, an ionically conductive and electrically conductive structure in which the polymers penetrate each other.

(13) Silicon 60, in its pure form in the present case, is embedded in copolymer 50. In this case, silicon is present in the form of particles which have a size of several nanometers or micrometers.

(14) Instead of or in addition to pure silicon 60, anodic active material 41 may also have an alloy containing silicon 60. This may be an alloy formed with an active metal, such as aluminum, magnesium, or tin, i.e., with a metal which is able to take up lithium ions. However, an alloy formed with an inactive metal, such as iron, titanium, or copper, i.e., a metal which is not able to take up lithium ions, is also possible.

(15) First polymer 51 of copolymer 50 is ionically conductive, i.e., permeable to lithium ions. Lithium ions may thus migrate through first polymer 51 and thereby also through anodic active material 41 of anode 21. Polyethylene oxide (PEO) may be used as the material for first polymer 51.

(16) First polymer 51 functions at the same time as a glue, or as a binder, for anodic active material 41. First polymer 51 thus increases the mechanical stability of anodic active material 41 and improves the adhesion of anodic active material 41 on current collector 31 of anode 21.

(17) Second polymer 52 of copolymer 50 is electrically conductive, i.e., permeable to electrons. Electrons may thus migrate through second polymer 52 and thereby also through anodic active material 41. Poly-3,4-ethylenedioxythiophene (PEDOT), polyaniline (PANI) or polypyrrole (PPY) may be used as the material for second polymer 52, for example.

(18) Copolymer 50 is, however, impermeable to electrolyte 15. Electrolyte 15 is thus not able to penetrate copolymer 50 and consequently does not get in contact with silicon 60. As a result, electrolyte 15 is not able to accumulate on silicon 60, or on the alloy containing silicon 60, of anodic active material 41. Copolymer 50 thus acts as a barrier for electrolyte 15.

(19) In the case of lithium accumulation, silicon 60 expands. In the case of such an expansion of silicon 60 of anodic active material 41, copolymer 50 expands accordingly, in an elastic manner, and continues to form a barrier which is impermeable to electrolyte 15.

(20) Anodic active material 41 furthermore contains carbon 55 which is integrated into anodic active material 41 in the form of carbon particles. Carbon 55 allows for a good contact between second polymer 52 and silicon 60.

(21) The present invention is not limited to the exemplary embodiments described here and the aspects emphasized therein. A plurality of modifications, which are within the scope of those skilled in the art, is possible, in accordance with the present invention.