1. Field of the Invention
The invention relates to a method of manufacturing a non-aqueous electrolyte secondary battery.
2. Description of Related Art
Conventionally, there has been widely known a non-aqueous electrolyte secondary battery that is equipped with a flat electrode body that is fabricated by stacking a pair of electrodes (a positive electrode and a negative electrode) formed in a sheet-like shape via a separator and winding them, and with a case that substantially assumes the shape of a rectangular parallelepiped and accommodates the electrode body as well as an electrolytic solution.
In general, the non-aqueous electrolyte secondary battery as described above is subjected to an initial charging process in which the battery is initially charged while being bound, a high-temperature aging process in which the battery that has been subjected to the initial charging process is maintained for a predetermined period at a high temperature (e.g., at a temperature equal to or higher than 60° C.) while being bound, and the like to become a final product (e.g., see Japanese Patent Application Publication No. 2000-346262 (JP-2000-340262 A)). However, in the case where the electrode body of the non-aqueous electrolyte secondary battery assumes a certain structure, the electrode body is highly likely to be short-circuited at a specific position thereof when the non-aqueous electrolyte secondary battery is subjected to the high-temperature aging process.
A battery that is highly likely to be short-circuited in the case of being subjected to a high-temperature aging process (hereinafter referred to as “a defective battery”) will be described hereinafter with reference to
As shown in
In the electrode body of the defective battery, the length of each of the separators in the winding direction thereof is longer than the length of the pair of the electrodes in the winding direction thereof. In a terminal end region of each of the separators in the winding direction thereof, there is a surplus portion that is in contact with neither of the electrodes. The surplus portion of each of the separators is located from the flat portion to the upper R portion, instead of being located at the lower R portion.
As shown in
In the defective battery, in the case where the defective battery is subjected to the high-temperature aging process, the following region thereof is highly likely to be short-circuited. That is, the outermost peripheral regions of the pair of the electrodes, namely, those regions which are located on the positive electrode non-support portion side of the upper R portion are short-circuited (see regions surrounded by circles in
The inventor and the like have found out that the surplus portions of the two separators constitute a cause of short-circuiting as a result of scrutinizing the cause of the aforementioned short-circuiting.
As shown in
Besides, as shown in
As a result, the positive electrode active material layer from which an excessive amount of lithium ions have been desorbed becomes locally high in potential, and becomes unstable. In the case where the high-temperature aging process is performed in this state, the positive electrode active material is eluted from the unstable positive electrode active material layer, and a metal constituting the positive electrode active material (e.g., Mn, Ni, or Co) is separated out on the negative electrode. As a result, short-circuiting is highly likely to occur.
As described hitherto, it has turned out that the surplus portions of the two separators constitute a cause of short-circuiting. However, although those regions of the electrode body of the defective battery in which the surplus portions of the two separators are located exist in addition to the upper R portion, short-circuiting hardly occurs in the regions other than the upper R portion. In this respect, the inventor and the like have found out that the binding of the defective battery in the initial charging process exerts an influence.
As shown in
When a load that is equal to or higher than a predetermined value is applied to the electrode body, the electrolytic solution is squeezed out from the separators of the electrode body. Therefore, lithium ions are not prompted to turn around from the positive electrode active material layer that is opposed to the negative electrode active material layer that is formed inside the outermost peripheral region of the negative electrode to the negative electrode active material layer that is formed outside the outermost peripheral region of the negative electrode (see
The invention has been made in view of the foregoing circumstances, and provides a method of manufacturing a non-aqueous electrolyte secondary battery that can suppress the occurrence of short-circuiting in a high-temperature aging process.
According to one aspect of the invention, there is provided a method of manufacturing a non-aqueous electrolyte secondary battery that is equipped with an electrode body that has a positive electrode, a negative electrode and a plurality of separators. An upper R portion of the electrode body is curved. The respective separators have surplus portions that are in contact with neither the positive electrode nor the negative electrode at terminal ends thereof. The case has an accommodation portion and a lid portion. The accommodation portion is a container that has an opening in an upper face thereof and accommodates the electrode body. The lid portion is a member that closes up the opening in the upper face of the accommodation portion. The method includes a process of forming positive electrode mixture layers on both faces of the positive electrode current collector of the positive electrode respectively, a process of forming negative electrode mixture layers on both faces of the negative electrode current collector of the negative electrode respectively, a process of arranging the negative electrode outside the positive electrode in the electrode body, and a process of winding the positive electrode, the negative electrode and the plurality of separators; The method, furthermore, includes an initial charging process and a high-temperature aging process. In the initial charging precess, the non-aqueous electrolyte secondary battery is charged while being bound such that the electrode body is pressed via the accommodation portion of the case, with the surplus portions of the plurality of the separators not located at the upper R portion of the electrode body. In the high-temperature aging process, the non-aqueous electrolyte secondary battery that has been subjected to the initial charging process is maintained for a predetermined high temperature. It should be noted herein that the predetermined high temperature in the high-temperature aging process is also preferably equal to or higher than 60 degrees Celsius.
Besides, in the method of manufacturing the non-aqueous electrolyte secondary battery, it is preferable that the non-aqueous electrolyte secondary battery be further equipped with a pair of current collector terminals and a spacer, that the pair of the current collector terminals be fixed to an outer peripheral face of the electrode body, and that the spacer be provided between the outer peripheral face of the electrode body and an inner face of the accommodation portion of the case, and be arranged in such a manner as to sandwich the electrode body together with the pair of the current collector terminals.
Besides, in the method of manufacturing the non-aqueous electrolyte secondary battery, it is preferable that the non-aqueous electrolyte secondary battery be further equipped with a spacer film that is arranged between an outer peripheral face of the electrode body and an inner face of the accommodation portion of the case, and that a thickness of the spacer film be set equal to or larger than a predetermined value. It should be noted herein that it is also preferable that the predetermined value of the thickness of the spacer film be a value larger than 50 μm. Furthermore, it is also preferable that this predetermined value be substantially 200 μm.
The method of manufacturing the non-aqueous electrolyte secondary battery according to the invention as described above makes it possible to suppress the occurrence of short-circuiting in the high-temperature aging process.
Features, advantages, and technical and industrial significance of an exemplary embodiment of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:
A battery 1 as one embodiment of a non-aqueous electrolyte secondary battery according to the invention will be described hereinafter with reference to
As shown in
The case 10 is a container that substantially assumes the shape of a rectangular parallelepiped, and is made of an aluminum alloy or the like. The case 10 has an accommodation portion 11 that has an opening in an upper face thereof, and a lid portion 12 that closes up the opening in the upper face of the accommodation portion 11.
The accommodation portion 11 is a housing that substantially assumes the shape of a rectangular parallelepiped, and has an opening in an upper face thereof. The electrode body 20 is accommodated inside the accommodation portion 11.
The lid portion 12 is a flat plate that assumes a shape corresponding to the opening in the upper face of the accommodation portion 11, and is bonded to the accommodation portion 11 through welding. A positive electrode terminal 13 and a negative electrode terminal 14, which function as external terminals of the battery 1, are fixed to the lid portion 12.
The electrode body 20 is fabricated by stacking a pair of sheet-like electrodes via a plurality of separators and winding them. The electrode body 20 functions as a power generation element by being impregnated with an electrolytic solution.
As shown in
The electrode body 20 is equipped with a positive electrode 21 and a negative electrode 22 as the pair of the electrodes, and a first separator 23 and a second separator 24 as the plurality of the separators, and is configured such that the second separator 24, the negative electrode 22, the first separator 23, and the positive electrode 21 are arranged in this order from the outside. In the electrode body 20, the negative electrode 22 as one of the positive electrode 21 and the negative electrode 22 is arranged at an outermost periphery, and an outermost peripheral region of the negative electrode 22 is covered at least with the second separator 24.
The positive electrode 21 is an electrode that is equipped with a sheet-like positive electrode current collector, and positive electrode mixture layers that are formed on both faces of the positive electrode current collector respectively. The positive electrode current collector is a current collector that is formed of a metal foil of aluminum, titanium, stainless steel, or the like. Each of the positive electrode mixture layers is an electrode mixture layer that is formed of a positive electrode mixture including a positive electrode active material. The positive electrode mixture layers are formed except on parts of respective surfaces of the positive electrode current collector.
The negative electrode 22 is an electrode that is equipped with a sheet-like negative electrode current collector, and negative electrode mixture layers that are formed on both faces of the negative electrode current collector respectively. The negative electrode current collector is a current collector that is formed of a metal foil of copper, nickel, stainless steel, or the like. Each of the negative electrode mixture layers is an electrode mixture layer that is formed of a negative electrode mixture including a negative electrode active material. The negative electrode mixture layers are formed except on parts of respective surfaces of the negative electrode current collector, as is the case with the positive electrode mixture layers.
The first separator 23 is a separator that is formed of an insulator such as a polyolefin resin (e.g., polyethylene or polypropylene) or the like. The length of the first separator 23 in the winding direction thereof is longer than the length of the positive electrode 21 in the winding direction thereof, and is longer than the length of the negative electrode 22 in the winding direction thereof. Thus, when the first separator 23 is wound as part of the electrode body 20, a surplus portion 23a that is in contact with neither the positive electrode 21 nor the negative electrode 22 is created in a terminal end region of the first separator 23 in the winding direction thereof. The surplus portion 23a is arranged from the flat portion 20c of the electrode body 20 to the lower R portion 20b of the electrode body 20, so as not to be located at the upper R portion 20a of the electrode body 20.
The second separator 24 is a separator that is configured substantially in the same manner as the first separator 23. The length of the second separator 24 in the winding direction thereof is longer than the length of the positive electrode 21 in the winding direction thereof, and is longer than the length of the negative electrode 22 in the winding direction thereof. Thus, when the second separator 24 is wound as part of the electrode body 20, a surplus portion 24a that is in contact with neither the positive electrode 21 nor the negative electrode 22 is created in a terminal end region of the second separator 24 in the winding direction thereof. The surplus portion 24a is arranged from the flat portion 20c of the electrode body 20 to the lower R portion 20b of the electrode body 20, so as not to be located at the upper R portion 20a of the electrode body 20.
A terminal end of the surplus portion 24a of the second separator 24 is fixed to a middle portion of the second separator 24 in the winding direction thereof at the lower R portion 20b by an adhesive tape or the like, whereby the electrode body 20 is held in a wound state.
As shown in
In the electrode body 20, a plate-like positive electrode current collector terminal 15 is fixed to the positive electrode non-support portion 21a, and a plate-like negative electrode current collector terminal 16 is fixed to the negative electrode non-support portion 22a.
The positive electrode current collector terminal 15 is a plate material that has electrical conductivity and is formed in such a manner as to extend in a vertical direction. An upper end of the positive electrode current collector terminal 15 is fixed to a positive electrode connection member that is electrically connected to the positive electrode terminal 13 (not shown). A lower end of the positive electrode current collector terminal 15 is fixed to the positive electrode non-support portion 21a of the positive electrode 21. More specifically, the positive electrode current collector terminal 15 is arranged on one wide face side (on a near side of the sheet of
The negative electrode current collector terminal 16 is a plate material that is configured substantially in the same manner as the positive electrode current collector terminal 15. An upper end of the negative electrode current collector terminal 16 is fixed to a negative electrode connection member that is electrically connected to the negative electrode terminal 14 (not shown). A lower end of the negative electrode current collector terminal 16 is fixed to the negative electrode non-support portion 22a of the negative electrode 22. More specifically, the negative electrode current collector terminal 16 is arranged on one wide face side (on the near side of the sheet of
A manufacturing process S1 of the battery 1 as one embodiment of the method of manufacturing the non-aqueous electrolyte secondary battery according to the invention will be described hereinafter with reference to
As shown in
The electrode body fabricating process S10 is a process in which the electrode body 20 is fabricated. In the electrode body fabricating process S10, the electrode body 20 is fabricated by stacking the positive electrode 21, the negative electrode 22, the first separator 23, and the second separator 24 in a predetermined sequence, winding them, and then deforming this wound body into a flat shape.
After being fabricated, the electrode body 20 is accommodated inside the case 10. Then, after an electrolytic solution is injected into the case 10, the initial charging process S20 is performed. Incidentally, an unfinished battery having the case 10 in which the electrode body 20 is accommodated and into which the electrolytic solution has been injected is referred to as “an intermediate product” for the sake of convenience.
The initial charging process S20 is a process in which the intermediate product is charged while being bound such that the electrode body 20 is pressed via the accommodation portion 11 of the case 10. As shown in
Then, the bound intermediate product is charged. At this time, since the surplus portions 23a and 24a are not arranged at the upper R portion 20a of the electrode body 20, lithium ions are restrained from turning around (see
Incidentally, a load is slightly less likely to be applied to the lower R portion 20b of the electrode body 20 than to the flat portion 20c of the electrode body 20. Therefore, it is preferable not to arrange the surplus portions 23a and 24a at the lower R portion 20b either. For example, as shown in
Besides, it is preferable to interpose a predetermined member between the inner face of the accommodation portion 11 of the case 10 and the outer peripheral face of the electrode body 20. In this embodiment of the invention, it is preferable to interpose a predetermined member between the inner face of the wide face of the accommodation portion 11 of the case 10 and the wide face of the flat portion 20c of the electrode body 20. For example, as shown in
Besides, as shown in
The high-temperature aging process S30 is a process in which the intermediate product that has been subjected to the initial charging process S20 is maintained at a high temperature. In the high-temperature aging, process S30, the intermediate product that has been subjected to the initial charging process S20 is bound by the binding device, and is maintained at a high temperature (e.g., at a temperature equal to or higher than 60° C.) for a predetermined period. As described above, in the initial charging process S20, lithium ions are restrained from turning around as described above. Therefore, the positive electrode active material layer of the positive electrode 21 is restrained from becoming locally high in potential, and from becoming unstable. Thus, even in the case where the intermediate product has been subjected to the high-temperature aging process S30, the positive electrode active material can be restrained from being eluted from the positive electrode active material layer of the positive electrode 21, and a metal constituting this positive electrode active material (e.g., Mn, Ni, or Co) can be restrained from being separated out on the negative electrode. Accordingly, the occurrence of short-circuiting in the high-temperature aging process S30 can be suppressed.
As described above, in the manufacturing process S1, the battery 1 is fabricated by being sequentially subjected to the electrode body fabricating process S10, the initial charging process S20, and the high-temperature aging process S30.
Number | Date | Country | Kind |
---|---|---|---|
2012-147907 | Jun 2012 | JP | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/IB2013/001371 | 6/27/2013 | WO | 00 |