WO1997008769A1

WO1997008769A1 - Current collector having electrode material on two sides for use in a laminate battery and method of making a battery

Info

Publication number: WO1997008769A1
Application number: PCT/US1996/013131
Authority: WO
Inventors: S. Scot Cheu
Original assignee: Valence Technology, Inc.
Priority date: 1995-08-25
Filing date: 1996-08-13
Publication date: 1997-03-06
Also published as: AU6773196A

Abstract

In a laminate battery cell, a sheet-like current collector is provided with electrode material in electrical contact with two sides of the current collector. Solid electrolyte material contacts the electrode material and separates the electrode material from an electrode material with a different electromotive potential. An extended portion of the current collector is provided to facilitate forming electrical connections with the current collector and the electrode material and to facilitate cooling of the battery cell.

Description

CURRENT COLLECTOR HAVING ELECTRODE MATERIAL

ON TWO SIDES FOR USE IN A LAMINATE BATTERY

AND METHOD OF MAKING A BATTERY

BACKGROUND OF THE INVENTION

FIELD OF THE INVENTION

The present invention relates to the construction of batteries and, more particularly, to laminate battery constructions in which a current collector has electrode material on two sides.

STATE OF THE ART

The basic structure and operation of a conventional battery such as a lead-acid battery may be understood with reference to Figure 1. The main elements of the battery are the anode, the cathode and the electrolyte. The anode, on discharge, supplies a flow of electrons, constituting an electric current, to an external device. The current powers the external device and returns to the cathode. Within the battery, the anode and the cathode are separated by the electrolyte. The electrolyte acts as an electrical insulator preventing electrons from moving between the anode and the cathode inside the battery. However, the electrolyte allows the movement of ions, the remainder of the atom or molecule from which the electron has been released. As electrons are released from the anode to the device, ions are released from the anode, cross through the electrolyte and are stored in the cathode. During the recharge process, ions are transferred through the electrolyte back to the anode.

In conventional batteries, the electrolyte is liquid. Liquid electrolytes effectively allow the movements of ions between the anode and the cathode. However, the use of liquid electrolytes has several disadvantages. In most batteries, the liquid electrolyte contributes a substantial portion of the battery's overall weight. In addition, most electrolytes are composed of hazardous chemicals, including acid. In the event of a short circuit or other physical damage to the battery, the liquid electrolyte may become free to flow to the reaction site and produce a continuous chemical reaction. This reaction may result in excess heat or a gas discharge, and if not properly released, may be explosive. Although batteries are sealed when manufactured, leaks can occur through misuse or a breakdown of the battery's packaging over time, posing a significant safety risk.

Polymer electrolyte batteries represent a new battery technology that differs significantly from conventional battery technology and promises significantly improved performance. Generally speaking, a polymer electrolyte battery includes an anode, such as a lithium metal anode, a single-phase, flexible solid polymer electrolyte, and a cathode that stores lithium ions. Unlike the liquid electrolyte used in most batteries, the polymer electrolyte is a solid. The use of a solid electrolyte makes it possible to substantially reduce the weight and volume of the battery. To date, however, solid electrolyte lithium batteries have not been available commercially because such batteries have operated effectively only at high temperatures.

Solid electrolyte lithium batteries operable at lower temperature levels promise to be commercially available in the near future. Such batteries will be suitable for a wider range of applications. Accordingly, it has become desirable to devise battery constructions that are simple in structure and facilitate simple manufacturing techniques. Further, it is desirable to devise battery constructions and efficient manufacturing techniques in which material usage and battery size is minimized.

SUMMARY OF THE INVENTION The present invention generally relates to battery constructions and manufacturing techniques that permit efficient use of electrode material in batteries and that facilitate construction of batteries.

In accordance with one aspect of the present invention, a battery cell comprises a sheet-like first electrode current collector having two sides. First electrode material is in electrical contact with both sides of the first electrode current collector. Second electrode material is provided, having an electromotive potential different from that of the first electrode material. Electrolyte material contacts both the first and the second electrode materials and separates the first and the second electrode materials.

In accordance with another aspect of the present invention, a battery comprises a plurality of battery cells. The battery cells each include a sheet-like first electrode current collector having two sides, and first electrode material in electrical contact with both sides of the first electrode current collector. The battery cells each further include a sheet-like second electrode current collector having two sides, second electrode material in electrical contact with one side of the second electrode current collector, the second electrode material having an electromotive potential different from that of the first electrode material, and electrolyte material contacting both the first and the second electrode materials and separating the first and the second electrode materials. The battery further comprises a housing enclosing the plurality of battery cells. First means for electrical connection of the first electrode current collectors of the plurality of battery cells are provided, a portion of the first electrical connection means extending outside of the housing. Second means for electrical connection of the second electrode current collectors of the plurality of battery cells are provided, a portion of the second electrical connection means extending outside of the housing. In accordance with still a further aspect of the present invention, a method of making a battery comprises the steps of covering at least a portion of both sides of a first electrode current collector with a first electrode material to form a first electrode. Second electrode material is coated on one side of a second electrode current collector to form a second electrode. The second electrode material has an electromotive potential different from that of the first electrode. The first electrode is fixed in position relative to a second electrode and an electrolyte such that the electrolyte is disposed between the first electrode material and the second electrode material to form a battery cell.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be further understood with reference to the following description in conjunction with the appended drawings, wherein like elements are provided with the same reference numerals. In the drawings:

Figure 1 is a diagrammatic view of a conventional battery;

Figure 2 is a schematic, cross-sectional view of a battery cell according to an embodiment of the present invention;

Figure 3 is a schematic, cross-sectional view of a battery composed of multiple battery cells and enclosed in a housing according to an embodiment of the present invention;

Figure 4 is a schematic, cross-sectional view of a battery composed of multiple battery cells and enclosed in a housing according to an embodiment of the present invention; and Figure 5 is a schematic, cross sectional view of a battery composed of multiple battery cells and enclosed in a housing according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in Figure 2, a battery cell 10 includes a first electrode laminate 41 having a first electrode cuπent collector layer 43 having a first portion 45, to which is applied a top and a bottom layer 49, 51 of first electrode material, and a second, extended portion 47. In accordance with the preferred embodiment, and except where otherwise noted, the first electrode laminate 41 is refeπed to herein as the anode laminate, the first electrode cuπent collector layer 43 is refeπed to herein as the anode cuπent collector layer, and the top and bottom layers 49, 51 of first electrode material are refeπed to as the top and bottom anode layers.

The anode cuπent collector layer 43 is sheet-like and is preferably formed from a continuous cuπent conducting web material, such as a nickel or copper web or sheet. The top and bottom anode layers 49, 51 preferably include anode material that is applied to the first portion 45 of the anode cuπent collector 43 by chemical vapor deposition or some other suitable deposition process such that the top and bottom anode layers are in electrical contact with the anode cuπent collector. Alternatively, the top and bottom anode layers 49, 51 can include sheets of anodic foil applied to the anode cuπent collector 43 such that the top and bottom anode layers are in electrical contact with the anode cuπent collector, or the anode laminate 41 can be formed from a sheet of anodic foil. Lithium is a particularly prefeπed anodic material because of its position in the electromotive series.

The battery cell 10 further includes a second electrode laminate sheet 21 having a second cuπent collector layer 23, a layer 25 of second electrode material laminated on the second cuπent collector layer, and an electrolyte layer 27 laminated on the second electrode layer. The layer 25 of second electrode material is of an electromotive potential different from that of the first electrode material. The second cuπent collector layer 23, the layer 25 of second electrode material, and the electrolyte layer 27 are laminated together such that the second cuπent collector layer is in electrical contact with the layer of second electrode material, and the layer of second electrode material is in electrical contact with the electrolyte layer. In accordance with the prefeπed embodiment, and except where otherwise noted, the second electrode laminate sheet 21 is refeπed to herein as the cathode laminate, the second cuπent collector layer 23 is refeπed to herein as the cathode cuπent collector layer, and the layer 25 of second electrode material is refeπed to herein as the cathode layer. The cathode cuπent collector layer 23 is provided to inject electrons into the cathode layer 25 which, by itself, is generally a relatively poor conductor. The cathode cuπent collector layer 23 also facilitates forming an electrical connection with the cathode laminate 21 in that an electrical connection can be made directly with the cathode cuπent collector layer.

The cathode cuπent collector layer 23 is sheet-like and is preferably formed from a continuous cuπent conducting web material, such as a nickel web or sheet. The cathode layer 25 is coated or covered onto the cathode cuπent collector layer 23 and is selected from the group of materials suited for storing ions released from an anode. The cathode layer 25 is preferably a composite material including a vanadium oxide, V₆Oι₃ or V₃O₈, material. The electrolyte layer 27 is a polymer electrolyte material that is coated or covered onto the cathode layer 25. The cathode layer 25 and the electrolyte layer 27 can be cured in an electron beam curing apparatus (not shown). U.S. Patent No. 4,925,751 to Shackle et al. describes certain materials useful in forming the cathode layer 25, the electrolyte layer 27, and the anode laminate 41, and is ncorporated_^ by reference to the extent that it describes such materials. As shown in Figures 2 and 4-5, the cathode laminate 21 is folded evenly around the anode laminate 41 such that the layer of electrolyte material 27 on the cathode laminate 21 contacts the top and bottom anode layers 49, 51, thereby forming the battery cell 10. Preferably, the cathode laminate 21 is of sufficient size such that, when the cathode laminate is folded around the anode laminate 41, the top and bottom layers 49, 51 of anode material are completely covered by the cathode laminate. Preferably, all of the extended portion 47 of the anode cuπent collector layer 43 extends outwardly from between the folded cathode laminate 21; however, the cathode laminate can extend over a portion of the extended portion of the anode cuπent collector layer.

As shown in Figure 3, it is also possible to position discrete cathode laminates 21 adjacent the top and bottom anode layers 49, 51 and thereby form the battery cell 10. Further, a plurality of battery cells 10, 10', 10" are preferably stacked on top of one another and be electrically connected to one another to form a battery pack 1. Extended portions 29, 29', 29" of each discrete cathode cuπent collector 23, 23', 23" of each discrete cathode laminate 21, 21', 21" are formed to facilitate forming an electrical connection between the cathode cuπent collectors and an external point. The extended portions 29, 29', 29" of each cathode cuπent collector 23, 23', 23" extend outwardly from the battery pack 1. The discrete cathode cuπent collectors 23, 23', 23" of the cathode laminates 21, 21', 21" suπounding each anode laminate 41, 41', 41" are electrically connected to one another by an electrical connector 54, such as a conductive strip or wire, contacting the extended portions 29, 29', 29" of each of the discrete cathode cuπent collectors, thereby electrically connecting discrete cathode layers 25, 25', 25" to one another.

In the folded structures shown in Figures 4 and 5, a plurality of battery cells 10, 10', 10" are stacked on top of one another to form a battery pack 1 such that a portion of the cathode cuπent collector layer 23 of the cathode laminate 21 of each cell contacts, and is thereby electrically connected to, a portion of the cathode cuπent collector layer of every other cell. In this manner, a plurality of cathode layers 25 are electrically connected to one another.

In the battery packs 1 shown in Figures 3-5, the plurality of battery cells 10, 10', 10" are preferably stacked such that each of the extended portions 47, 47', 47" of each of the anode cuπent collectors 43, 43', 43" of each of the anode laminates 41, 41', 41" of each cell extend in the same direction. Aligning all the battery cells in the same direction facilitates electrically connecting all of the discrete anode laminates 41, 41', 41" to one another by an electrical connector 53. In the altemative, the plurality of battery cells 10, 10', 10" can be arranged in alternatingly opposite directions (not shown). The electrical connector 53 is preferably a conductive strip, such as a piece of copper wire or sheet, which is electrically connected to each of the extended portions 47, 47', 47" of the anode cuπent collectors 43, 43', 43", such as by welding, soldering or by being fused to the extended portions by a chemical reaction. In this manner, all of the top and bottom anode layers 49, 49', 49", 51, 51', 51" are electrically connected to one another. The cathode laminates 21, 21', 21" of the plurality of battery cells 10, 10', 10" are electrically connected to one another by contact of the conductive cathode cuπent collectors 23, 23', 23" with one another. The cathode laminates 21, 21', 21" are electrically connected to an outside load or power source by the electrical connector 54 contacting an exposed portion of one of the cathode cuπent collectors 23, 23', 23". As noted above, in the battery pack 1 shown in Figure 3, the electrical connector 54 is connected to all of the discrete cathode cuπent collectors 23, 23', 23".

When multiple cells 10, 10', 10" are joined together to form a battery pack 1, as shown in Figures 3-5, the extended portions 47, 47', 47" of the anode cuπent collectors 43, 43', 43" of the cells extend parallel to one another, thereby forming a finned heat sink structure. Air flow across the extended portions 47, 47', 47" of the anode cuπent collectors 43, 43', 43" permits heat from the reactive core of the battery, the lithium anode layer 49, 51, to be rapidly dissipated. Air flow can be provided by natural or forced convection. Heat conduction from the extended portions 47, 47', 47" of the anode cuπent collectors 43, 43', 43" allows the top and bottom lithium layers 49, 51 to be maintained at a low, stable operating temperature.

One or more battery cells 10 can be enclosed in a housing 60, as shown in Figures 3-5, which can be rigid or flexible. In the housing 60 shown in Figure 4, the extended portions 47, 47', 47" of the anode cuπent collectors 43, 43', 43" extend through a wall 61 of the housing, thereby facilitating forming electrical connections with the anode laminates 41, 41', 41" as well as facilitating blowing cooling air over the extended portions to maintain the battery cells 10, 10', 10" at a proper operating temperature. A prefeπed flexible housing 60 includes a shrink wrap material wrapped around the battery pack 1. Edges 62 of the shrink wrap material where the extended portions 47, 47', 47" of the anode cuπent collectors 43, 43', 43" extend through the wall 61 of the housing 60 are sealed, preferably with a hot melt adhesive 63. Sealing the battery pack 1 in the foregoing manner helps to prevent damage to the battery cells 10 that might occur due to exposure to the elements; particularly exposure to water, which is highly reactive with many anode materials such as lithium.

As shown in Figures 3 and 5, the battery pack 1 can be enclosed in a housing 60 such that the extended portions 47, 47', 47" of the anode cuπent collectors 43, 43', 43" are enclosed within the housing. In Figure 3, the extended portions 29, 29', 29" of the cathode cuπent collectors 23, 23', 23" are enclosed within the housing 60. A portion of the electrical connector 53 extends outside of the housing 60 so that the anode laminates 41, 41', 41" of the battery cells 10, 10', 10" can be connected to a load or a power source (not shown). A portion of the electrical connector 54 also extends outside of the housing 60 so that the cathode laminates 21, 21', 21" of the battery cells 10, 10', 10" can be connected to the load or the power source. In the housing shown in Figure 3, the electrical connector 54 is connected to each of the extended portions 29, 29', 29" of the cathode cuπent collectors 23, 23', 23" and a portion of the electrical connector 54 extends through the wall 61 of the housing, thereby facilitating forming electrical connections with the cathode laminates 21, 21', 21", as well as facilitating blowing cooling air over the extend portions to maintain the battery cells 10, 10', 10" at a proper operating temperature. Again, edges 62 of the shrink wrap material where the electrical connectors 53, 54 extend through the wall 61 of the housing 60 are sealed with hot melt adhesive 63. The housing 60 is preferably selected such that open spaces are provided near the extended portions 47, 47', 47" of the battery cells 10, 10', 10" to permit internal ventilation of the battery cells.

The above-described battery cell 10 provides significant advantages. For example, by depositing lithium on the cuπent collector 43, the thickness of the anode laminate 41, and of the top and bottom anode layers 49, 51 is able to be carefully controlled. In a typical application, lithium anode layers 49, 51 of 5 to 15 microns in thickness are sufficient, depending on the capacity of the cell. Lithium foils, on the other hand, are not presently known to be commercially available in thicknesses less than about 75 microns. Using a lithium foil anode 75 microns thick in an application where a layer of lithium of only 5 to 15 microns thick would normally suffice results in a several-fold excess of lithium.

By depositing the lithium material on the first portion 45 of the cuπent collector 43 in only the required thickness for the top and bottom anode layers 49, 51, the concentration of lithium in the battery can be reduced, reducing expense, enhancing safety, and not least of all, reducing the volume of the battery cell 10. Furthermore, the cuπent collector 43 effectively partitions the battery cell 10, dividing the top and bottom anode layers 49, 51 into separate portions and forming a sort of reaction barrier between those separate portions. A potential problem in one part of the battery cell 10 is, therefore, less likely to affect other parts of the battery cell.

Thus, it can be appreciated that the above-described battery provides a means for efficiently removing sufficient heat from a battery cell 10 or a battery pack 1 to reduce risks due to explosions. This is done, as described above, by providing a heat sink in the form of thin metal foil cuπent collector 43 that has been coated or covered, on a first portion 45, with lithium or other active metal. A second portion 47 of the cuπent collector 43 acts as a heat sink and radiator to maintain a low temperature in the interior of a battery cell 10. The second portion 47 of the metal foil cuπent collector 43 also provides a convenient method for removing cuπent from the battery cell 10 at high rates.

In a prefeπed method for making a battery pack 1, first electrode material is coated or covered on the first portion 45 of both sides of the first electrode cuπent collector 43 to form a top and bottom layers 49, 51 of the first electrode laminate 41. Second electrode material is coated covered on at least one side of a second electrode cuπent collector 23 to form a layer 25 of a second electrode laminate 21. The second electrode material has an electromotive potential different from that of the first electrode material. The first electrode laminate 41 is fixed in position relative to the second electrode laminate 21 and the electrolyte 27 such that the electrolyte is disposed between the first electrode material and the second electrode material to form the battery cell 10.

Further, a plurality of battery cells 10, 10', 10" are preferably stacked on top of one another, and the first electrode cuπent collectors 43, 43', 43" of the plurality of battery cells are electrically connected to one another. The second electrode cuπent collectors 23, 23', 23" of the plurality of battery cells 10, 10', 10" are also electrically connected to one another.

The stacked plurality of battery cells 10, 10', 10" are enclosed in a housing 60. A portion of the electrical connector 53 for electrically connecting the first electrode cuπent collectors 43, 43', 43" is extended outside of the housing 60 through the wall 61 of the housing. A portion of an electrical connector 54 for electrically connecting the second electrode cuπent collectors 23, 23', 23" is extended outside of the housing 60 through the wall 61 of the housing.

The foregoing principles can be applied advantageously in batteries having designs other than the above-described folded cell design. Also the foregoing principles can be applied in batteries using other anode materials, such as sodium, magnesium, or some other active metal. Accordingly, although the foregoing has described the principles, prefeπed embodiments and modes of operation of the present invention, the invention should not be construed as limited to the particular embodiments discussed. Instead, the above described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.

Claims

WHAT IS CLAIMED IS:

1. A battery cell comprising: a sheet-like first electrode cuπent collector having two sides; first electrode material covering at least portions of both sides of the first electrode cuπent collector; second electrode material, having an electromotive potential different from that of the first electrode material; and solid electrolyte material contacting both the first and the second electrode materials and separating the first and the second electrode materials.

2. The battery cell of claim 1, wherein the second electrode material is in electrical contact with one or more sheet-like second electrode cuπent collectors.

3. The battery cell of claim 2, wherein second electrode material of the second electrode cuπent collectors is disposed, relative to both sides of the first electrode cuπent collector, such that the first electrode material on both sides of the first electrode cuπent collector is in ion exchange, through the electrolyte material, with the second electrode material on the second electrode cuπent collectors.

4. The battery cell of claim 3, wherein the first electrode cuπent collector and the first electrode material are disposed between the second electrode material on two second electrode cuπent collectors, and a portion of the first electrode cuπent collector extends outwardly from between the second electrode material and the second electrode cuπent collectors.

5. The battery cell of claim 3, wherein a second electrode cuπent collector is folded around the first electrode cuπent collector such that the first electrode material on both sides of the first electrode cuπent collector is in ion exchange, through the electrolyte material, with the second electrode material on the second electrode cuπent collector.

6. The battery cell of claim 2, wherein the electrolyte material is coated on the second electrode material.

7. The battery cell of claim 1, wherein the first electrode material is an anodic material.

8. The battery cell of claim 1, wherein the first electrode material is coated on each side of the first electrode cuπent collector to a thickness of less than 30 microns.

9. The battery cell of claim 1, wherein the first electrode material is lithium.

10. The battery cell of claim 1, wherein the electrolyte material is a flexible, solid polymer electrolyte.

11. The battery cell of claim 1, wherein the first electrode cuπent collector is made of an electrically and thermally conductive material.

12. A battery, comprising: a plurality of battery cells, the battery cells each including a sheet-like first electrode cuπent collector having two sides, first electrode material in electrical contact with both sides of the first electrode cuπent collector, a sheet-like second electrode cuπent collector having two sides, second electrode material in electrical contact with one side of the second electrode cuπent collector, the second electrode material having an electromotive potential different from that of the first electrode material, and solid electrolyte material contacting both the first and the second electrode materials and separating the first and the second electrode materials; a housing enclosing the plurality of battery cells; first means for electrical connection of the first electrode cuπent collectors of the plurality of battery cells, a portion of the first electrical connection means extending outside of the housing; and second means for electrical connection of the second electrode cuπent collectors of the plurality of battery cells, a portion of the second electrical connection means extending outside of the housing.

13. The battery of claim 12, wherein a portion of each first electrode cuπent collector of the plurality of battery cells is extended, and the first electrical connection means contacts the extended portion of each first electrode cuπent collector.

14. A method of making a battery, comprising the steps of: covering at least a portion of both sides of a first electrode cuπent collector with a first electrode material to form a first electrode; covering at least a portion of one side of a second electrode cuπent collector with a second electrode material to form a second electrode, the second electrode material having an electromotive potential different from that of the first electrode; and fixing the first electrode in position relative to a second electrode and a solid electrolyte such that the electrolyte is disposed between the first electrode material and the second electrode material to form a battery cell.

15. The method of claim 14, comprising the further steps of stacking a plurality of battery cells on top of one another; electrically connecting the first electrode cuπent collectors of the plurality of battery cells; and electrically connecting the second electrode cuπent collectors of the plurality of battery cells.

16. The method of claim 15, comprising the further steps of enclosing the stacked plurality of battery cells in a housing; extending a portion of a first means for electrically connecting the first electrode cuπent collectors outside of the housing; and extending a portion of a second means for electrically connecting the second electrode cuπent collectors outside of the housing.