Patent Application
20090100669
The present invention relates to an improvement in a battery manufacturing method and apparatus.
There have been known batteries including a roll-shaped electrode assembly formed by winding sheet-shaped positive and negative electrodes into a roll shape together with a separator. In manufacturing positive and negative electrodes of these conventionally-known batteries, the positive and negative electrodes would be undesirably deformed due to a difference in extension (or elongation) between a portion coated with an electrode active material and other portions not coated with the electrode active material, as detailed below with reference to
However, because not only the non-active-material-coated portion of the electrode sheet 211 is extended due to the corrugation process but also the active-material-coated portion too is extended due to the roll-pressing, the entire paid-out leading section of the electrode sheet 211 is considerably extended in the longitudinal direction of the electrode sheet 211. Thus, the paid-out section of the electrode sheet 211 has an excessively reduced thickness and hence a reduced strength against a pulling force. Consequently, at a stage following the cutting step, the positive-pole and negative-pole electrode sheets may break and/or be further extended when wound into a roll shape together with a separator.
Further, in some conventional electrode sheet manufacturing apparatus, pressing, slitting and winding steps of an electrode sheet process edges of the electrode sheet, and thus, if the edges of the electrode sheet has a corrugated shape, it tends to be difficult to accurately position the electrode sheet at a predetermined position, which results in a reduced processing accuracy.
In view of the foregoing prior art problems, it is an object of the present invention to provide an improved battery manufacturing method and apparatus which not only can minimize an undesired thickness change of electrode sheets but also can minimize lowering of a processing accuracy of the electrode sheets.
In order to accomplish the above-mentioned object, the present invention provides an improved method for manufacturing a battery including positive and negative sheet electrodes formed from positive and negative electrode sheets each having active-material-coated portions on opposite surfaces, except for opposite surfaces of one side edge portion, of the electrode sheet and non-active-material-coated portions on the opposite surfaces of the one side edge portion of the electrode sheet, which comprises: a step of forming a succession of corrugations on each of the positive and negative electrode sheets, having the active-material-coated portions provided thereon, in a longitudinal direction of the electrode sheet; a step of roll-pressing each of the positive and negative electrode sheets having the succession of corrugations formed thereon; a step of constructing an electrode assembly of the positive and negative sheet electrodes, formed from the roll-pressed positive and negative electrode sheets respectively, with a separator interposed therebetween; a step of connecting positive and negative current collectors to the non-coated portions of the positive and negative sheet electrodes, respectively, exposed on ends of the electrode assembly; and a step of enclosing the electrode assembly and the positive and negative current collectors in a case together with battery electrolyte.
In the roll-pressing step, only the active-material-coated portions (i.e., electrode active material and electrode film) are roll-pressed. Namely, the active-material-coated portions of the electrode sheet (i.e., of a leading section of the electrode sheet) are roll-pressed and extended, while the non-active-material-coated portions of the electrode sheet are not roll-pressed and extended because they have a smaller thickness than the active-material-coated portions.
With the arrangement that the electrode sheet is roll-pressed after the formation, in the longitudinal direction, of the succession of corrugations, the extension produced in the active-material-coated portions of the electrode film due to the roll-pressing can be effectively absorbed in the corrugations, so that no residual stress arises from a difference in extension between the active-material-coated portions and the non-active-material-coated portions of the electrode sheet; thus, the electrode sheet will not curve when it is cut in the longitudinal direction thereof through the width of the sheet. Because almost no extension occurs in the non-active-material-coated portions of the electrode sheet, a thickness change of the electrode sheet can be minimized or prevented. Further, because the battery manufacturing method of the present invention is not arranged to process the side edges of the electrode sheet, it can effectively prevent reduction or lowering of processing accuracy. As a result, it is possible to prevent unwanted breakage and further extension of the positive and negative sheet electrodes when constructing the electrode assembly, and thus achieve an enhanced productivity and product quality of the battery.
In an embodiment, the above-mentioned step of forming a succession of corrugations forms the corrugations on each of the positive and negative electrode sheets by imparting tension to portions of the electrode sheet located upstream and downstream of roll-pressing rollers when the electrode sheet is to be roll-pressed via the rollers. Namely, as the electrode sheet is fed forward through the rollers, the electrode sheet is pulled forwardly, i.e., downstream, of the rollers. Because the non-active-material-coated portions, having a smaller thickness than the active-material-coated portions, are not sandwiched and detained by the roll-pressing rollers with only the active-material-coated portions sandwiched and detained by the roll-pressing rollers, only the non-active-material-coated portions are moved forward in a sheet feeding direction, so that a succession of corrugations can be produced in the electrode sheet. Thus, the method of the invention can form the corrugations with ease by just imparting tension to the electrode sheet.
In one embodiment, the step of forming a succession of corrugations forms the corrugations on each of the positive and negative electrode sheets by plastically deforming the active-material-coated portions of the electrode sheet. Such plastically deformation allows the succession of corrugations to be formed with increased ease and accuracy.
In one embodiment, the step of forming a succession of corrugations forms the corrugations on each of the positive and negative electrode sheets after heating the active-material-coated portions of the electrode sheet. Such heating allows the active-material-coated portions (i.e., electrode active material and electrode film) to be plastically deformed easily, which can even further facilitate the formation of the corrugations.
The present invention can be implemented as an apparatus invention as well as the method invention as discussed above. Namely, the present invention provides an improved apparatus for manufacturing a battery including positive and negative sheet electrodes formed from positive and negative electrode sheets each having active-material-coated portions on opposite surfaces, except for opposite surfaces of one side edge portion, of the electrode sheet and non-active-material-coated portions on the opposite surfaces of the one side edge portion of the electrode sheet, which comprises: a section for forming a succession of corrugations on each of the positive and negative electrode sheets, having the active-material-coated portions provided thereon, in a longitudinal direction of the electrode sheet; and a section for roll-pressing each of the positive and negative electrode sheets having the corrugations formed thereon, an electrode assembly being constructed of the positive and negative sheet electrodes with a separator interposed therebetween, the electrode assembly and the positive and negative current collectors, connected to the non-active-material-coated portions of the positive and negative sheet electrodes exposed on opposite ends of the electrode assembly, being enclosed in a case together with battery electrolyte.
In the roll-pressing section, only the active-material-coated portions (i.e., electrode active material and electrode film) are roll-pressed. Namely, the active-material-coated portions of the electrode sheet are roll-pressed and extended, while the non-active-material-coated portions of the electrode sheet are not roll-pressed and extended because they have a smaller thickness than the active-material-coated portions. With the arrangement that the electrode sheet is roll-pressed after the formation, in the longitudinal direction, of the succession of corrugations, the extension produced in the active-material-coated portions of the electrode film due to the roll-pressing can be absorbed in the corrugations, so that no residual stress arises from a difference in extension between the active-material-coated portions and the non-active-material-coated portions of the electrode sheet; thus, the electrode sheet will not curve, due to a difference in extension between the active-material-coated portions and the non-active-material-coated portions, when it is cut in the longitudinal direction thereof through the width of the sheet. Because almost no extension occurs in the non-active-material-coated portions of the electrode sheet, the thickness change of the electrode sheet, particularly the non-active-material-coated portions, can be minimized. Further, because the battery manufacturing apparatus of the invention is not arranged to process the side edges of the electrode sheet, it can effectively prevent reduction or lowering of processing accuracy. As a result, it is possible to prevent unwanted breakage and further extension of the positive and negative sheet electrodes when constructing the electrode assembly, and thus achieve an enhanced productivity and product quality of the battery.
The following will describe embodiments of the present invention, but it should be appreciated that the present invention is not limited to the described embodiments and various modifications of the invention are possible without departing from the basic principles. The scope of the present invention is therefore to be determined solely by the appended claims.
Certain preferred embodiments of the present invention will be described in detail below, by way of example only, with reference to the accompanying drawings, in which:
Reference is now made to
The positive sheet electrode 11 comprises a positive electrode film 11a and active material 11b coated on the opposite surfaces of the positive pole film 11a. The negative sheet electrode 12 comprises a negative electrode film 12a and active material 12b coated on the opposite surfaces of the negative pole film 11b.
The separators 13 electrically insulate between the positive sheet electrode 11 and the negative sheet electrode 12 and between the negative sheet pole 12 and the case 16. The current collectors 14 and 15, which are identical in construction and behavior to each other, are incorporated in the case 16 in vertically opposite orientations, and they are indicated by different reference characters in the figures for convenience of description.
The negative sheet electrode 12 may be held in direct contact with the case 16 without the current collector 15 being used. The conductive plate 17 has a pressing section 17a that provides a pressing force by being flexed at the time of assembly.
After the conductive plate 17 and lid 19 are inserted in the opening portion 16b of the case 16, the upper end portion of the case 16 is sealed by being squeezed radially inwardly as shown in
Each of the current collectors 14 and 15 has a plurality of radial protrusions 14a or 15a and a central protrusion 14c or 15c. The central protrusion 14a of the current collector 14 is a section that connects to the pressing section 17a of the conductive plate 17, while the central protrusion 15c of the current collector 15 is a section that connects to the bottom 16a (see
The negative electrode film 12a of the negative sheet electrode 12 has the opposite surfaces coated with the electrode active material 12b (to provide active-material-coated portions or coated portions, which are also indicated by reference characters 12b), except for one side edge portion of the film 12a; the coated portion 12b of the inner (reverse) surface is not visible the figure. In the illustrated example, the non-coated portions 12c (the non-coated portion 12c of the inner (reverse) surface is not visible in the figure) are each formed on the lower side of the negative sheet electrode 12 and have a predetermined width. The non-coated portions (i.e., non-active-material-coated portion) 11c and 12c have higher electrical conductivity than the coated portions 11b and 12b.
These positive and negative sheet electrodes 11 and 12 are wound into a roll shape with the separator 13 interposed therebetween in such a manner that the active materials 11b and 12b superposed on each other via the separator 13, and then accommodated in the case 16 with the non-coated portions 11c and 12c exposed or projecting outwardly beyond the opposite ends of the roll-shaped electrode assembly 23 (see
The following paragraphs describe an apparatus and method for manufacturing the above-described positive and negative sheet electrodes 11 and 12 in accordance with embodiments of the present invention.
The input-side driving roller 34 and output-side driving roller 36 differ from each other in rotating speed; namely, the output-side driving roller 36 is caused to rotate at a slightly higher speed than the input-side driving roller 34, to thereby impart predetermined tension to a portion of the electrode sheet 31 located between the roll-pressing rollers 37 and 38 and the output-side driving roller 36. That is, the input-side driving roller 34 and output-side driving roller 36 together constitute a tension imparting device 55.
Further, the roll-pressing rollers 37 and 38 rotate at the same speed as the input-side driving roller 34; thus, during the roll-pressing of the electrode sheet 31 by the roll-pressing rollers 37 and 38, a portion of the electrode sheet 31 located between the output-side driving roller 36 and the roll-pressing rollers 37 and 38 has greater tension than a portion of the electrode sheet 31 located between the input-side driving roller 34 and the roll-pressing rollers 37 and 38. The roll-pressing rollers 37 and 38 and the roll device 41 together constitute a rolling device 57.
The induction heating device 53 induces a voltage in the leading section of the electrode sheet 31, by means of the induction coils 51 and 52, to produce a heating current flow in the leading section of the electrode sheet 31. The leading section of the electrode sheet 31 is heated by Joule heat produced through electric resistance of the sheet 31. As the leading section of the electrode sheet 31 is heated by the induction heating device 53, it gets easier to plastically deform.
Next, behavior of the electrode manufacturing apparatus 30 will be explained to describe an example manner or method in which the electrode sheet 31 is manufactured in accordance with the basic principles of the present invention. Although how the positive sheet electrode 11 is manufactured will be primarily or representatively described hereinbelow, it should be appreciated that the negative sheet electrode 12 is manufactured in the same manner as the positive sheet electrode 11.
The leading section of the electrode sheet 31 is first paid out from the paying-out device 32, then imparted with tension by the input-side driving roller 34 and output-side driving roller 36 (rolling at different speeds), and then pressed between and rolled by the roll-pressing rollers 37 and 38 rotating while the induction heating device 53 is heating the leading section of the electrode sheet 31. The leading section of the electrode sheet 31 roll-pressed by the roll-pressing rollers 37 and 38 are divided into two electrode sheets by being cut by the cutting device 46 centrally through the width of the electrode sheet 31, and then the thus-made two electrode sheets are taken up by the taking-up device 47.
(4-2) of
Before passing the input-side driving roller 34, each of the coated and non-coated portions 11b and 11c in the leading section 31A of the electrode sheet 31 has not been plastically deformed.
On the leading section 31B (which is identical to the leading section 31A but indicated by the different reference character 31B to facilitate understanding) of the electrode sheet 31 located between the input-side driving roller 34 and the roll-pressing rollers 37 and 38, corrugations 61 have been produced by the tension imparted by the input-side driving roller 34 and output-side driving roller 36. Such corrugations 61 are produced on only the coated portions 10b or on both of the coated portions 10b and non-coated portions 11c. The following lines describe the case where the corrugations 61 have been produced only on the coated portions 10b.
On the leading section 31C (which is identical to the leading section 31A but indicated by the different reference character 31C to facilitate understanding) of the electrode sheet 31 located between the roll-pressing rollers 37 and 38 and the output-side driving roller 36, other corrugations 62 have been produced by the tension imparted by the input-side driving roller 34 and output-side driving roller 36 and by plastic deformation (extension) of the coated portions 10b (active material and positive electrode film 11a) resulting from the roll-pressing by the roll-pressing rollers 37 and 38. No plastic deformation has been produced in the non-coated portions 11c.
The corrugations 62 have a shorter waveform cycle than the corrugations 61 because it is a combination of the corrugations 61 and the extension resulting from the roll-pressing by the roll-pressing rollers 37 and 38 (namely, the extension has been absorbed in the corrugations 61). If the waveform cycle of the corrugations 61 is indicated by T1 and the waveform cycle of the corrugations 62 is indicated by T2, T2<T1.
As shown in
Further, because the non-coated portions 11c are not detained by the roll-pressing rollers 37 and 38, only the non-coated portions 11c are moved forward in the sheet feeding direction as shown in
Namely, as set forth above in relation to
Furthermore, because the battery manufacturing method of the invention is not arranged to process the edges of the electrode sheet 31, it can effectively prevent reduction in the processing accuracy. As a consequence, it is possible to prevent unwanted breakage and further extension of the positive and negative sheet electrodes 11 and 12 when constructing the electrode assembly 23 and thus achieve an enhanced productivity and product quality of the battery 10.
Further, prior to the roll-pressing of the electrode sheet 31, portions of the electrode sheet 31 located upstream and downstream of the roll-pressers 37 and 38 are imparted with tension, to thereby form the corrugations 61 on the electrode sheet 31. Thus, the corrugations 61 can be formed easily by the imparted tension.
Further, because the corrugations are formed after the coated portions 11b and 12b are heated, the corrugation formation can be even further facilitated because the heating of the coated portions 11b and 12b allows the electrode sheet 31 to be plastically deformed more easily.
The present invention also provides the battery manufacturing apparatus of the type which first forms the positive sheet electrode 11 and negative sheet electrode 12 by providing the coated portions 11b and 12b on the opposite surfaces, except for those of respective one side edge portions, of the positive electrode sheet and negative electrode sheet and providing the non-coated portions 11c and 12c on the opposite surfaces of the respective one side edge portions of the electrode sheets, then constructs the electrode assembly 23 of the positive and negative sheet electrodes 11 and 12 with the separator 13 interposed therebetween, and then connects the positive and negative current collectors 14 and 15 to the coated portions 11c and 12c exposed on the opposite ends of the electrode assembly 23. As novel features of the battery manufacturing apparatus of the present invention, the apparatus includes: the tension imparting device 55 for forming a succession of corrugations 61 on the leading section of the electrode sheet 31 in the longitudinal direction of the sheet 31 having the coated portions 11b, 12b; the roll-pressing device 57 for roll-pressing the electrode sheet 31 having the corrugations 61 formed thereon; and the cutting device 46 for cutting the thus roll-pressed electrode sheet 31 in the longitudinal direction centrally through its width W, to provide two positive or negative sheet electrodes 11 or 12. The electrode assembly 23 and the positive and negative current collectors 14 and 15 are inserted, together with the electrolyte 21, into the case 16, after which the case 16 is sealed. With the feature that the electrode sheet 31 is roll-pressed after the succession of the corrugations 61 has been formed on the leading section of the electrode sheet 31 in the longitudinal direction of the sheet 31 as noted above, extension of the coated portions 11b, 12b produced by the roll-pressing can be absorbed in the succession of the corrugations 61. Thus, it is possible to not only prevent unwanted curvature, in the width direction, of each of the positive and negative sheet electrodes 11 and 12 produced due to a difference in extension between the coated portions 11b, 12b and the non-coated portions 11c, 12c when the roll-pressed electrode sheet 31 has been cut in the longitudinal direction centrally through its width W, but also minimize a change in the thickness of the electrode sheet 31, particularly the non-coated portions 11c, 12c.
Furthermore, because the battery manufacturing apparatus of the invention does not process the edges of the electrode sheet 31, it can effectively prevent reduction in the processing accuracy. As a consequence, it is possible to prevent unwanted breakage and further extension of the positive and negative sheet electrodes 11 and 12 when constructing the electrode assembly 23 and thus achieve an enhanced productivity and product quality of the battery 10.
In the sheet electrode manufacturing apparatus 70, the feeding direction of the leading section of the electrode sheet 31 is changed via the idle roller 72, located upstream of the roll-pressing rollers 37 and 38, so that the leading section is wound around the roll-pressing rollers 37 and 38 in an inverted S shape. The feeding direction of the leading section of the electrode sheet 31 is further changed via the idle roller 73 located downstream of the roll-pressing rollers 37 and 38. The formation of the corrugations 61 and 62 is performed in the sheet electrode manufacturing apparatus 70 in generally the same manner as in the sheet electrode manufacturing apparatus 30 of
As set forth above in relation to
It should be appreciated that, although the battery 10 has been shown and described as a roll-type battery, the present invention is not so limited and the battery 10 may be a rectangular-type or lamination-type.
The battery manufacturing method and apparatus of the present invention are well suited for use in manufacturing of lithium ion batteries.
Obviously, various minor changes and modifications of the present invention are possible in light of the above teaching. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-274263 | Oct 2007 | JP | national |
