Patent Description:
In producing a battery, for example, a battery is first assembled by accommodating an electrode body in a metal battery case, and then the internal air pressure of the battery case is reduced less than the atmospheric pressure and further a specified amount of an electrolytic solution is injected in the battery case through a liquid inlet provided in the battery case. Subsequently, the air pressure in the battery case is returned to the atmospheric pressure, thereby promoting impregnation of the injected electrolytic solution into the inside of the electrode body.

However, from the viewpoint of increasing the volumetric energy density of a battery, a battery case is designed with as small a size as possible, so that the empty space of the battery case around the electrode body is small. Therefore, if the injecting speed of the electrolytic solution is increased, the electrolytic solution may overflow out of the battery through the liquid inlet before the specified amount of the electrolytic solution is completely injected. To avoid such a defect, it is necessary to slowly inject the electrolytic solution according to the impregnation speed of the electrolytic solution into the electrode body. This liquid injecting time takes long and leads to low productivity of batteries.

To address the aforesaid disadvantages, Patent Document <NUM> proposes the following manners (see claim <NUM> and others of Patent Document <NUM>. Specifically, while the internal air pressure of a battery case is reduced less than the atmospheric pressure, firstly, an electrolytic solution is injected until at least part of an electrode body is immersed with the electrolytic solution. Successively, the air pressure in the battery case is increased, thereby promoting impregnation of the injected electrolytic solution into the electrode body, thus decreasing the liquid level of the electrolytic solution. Thereafter, injection of the electrolytic solution is restarted to inject a remaining amount of electrolytic solution. This manner can increase the liquid-injecting speed of the electrolytic solution in the first-time injection as compared with the foregoing method in which a specified amount of the electrolytic solution is injected at a time. Thus, the time required for the liquid injecting step can be shortened.

However, even in the method of Patent Document <NUM>, if the liquid injecting speed of the electrolytic solution is increased in the second-time injection, the electrolytic solution may overflow out of the battery through the liquid inlet before the remaining amount of electrolytic solution is completely injected. It is thus necessary to slowly inject the electrolytic solution in accordance with the impregnation speed of the electrolytic solution into the electrode body. Alternatively, it is necessary to wait until the liquid level of electrolytic solution sufficiently decreases and then inject the remaining amount of electrolytic solution. Accordingly, the second-time injection needs a long liquid injection time. Since such a conventional liquid injecting step takes much time as mentioned above, there is room for improvement.

The present disclosure has been made to address the above problems and has a purpose to provide a method for producing a battery with a shorter time required for a liquid injecting step to inject an electrolytic solution into a battery case as compared with a conventional method.

To achieve the above-mentioned purpose, one teaching of the present disclosure provides a method for producing a battery, the battery comprising: a battery case made of metal, including a liquid inlet; an electrode body accommodated in the battery case, the electrode body including an electrode opposed part in which a positive active material layer of a positive electrode sheet and a negative active material layer of a negative electrode sheet are opposed to each other; and an electrolytic solution contained in the battery case, characterized in that the method comprises injecting the electrolytic solution into the battery case through the liquid inlet, the injecting includes: a first liquid-injecting step of injecting the electrolytic solution of a predetermined first injection amount while air pressure in the battery case is regulated to a predetermined first air pressure, the predetermined first injection amount being determined so that a liquid-level height of the injected electrolytic solution falls within an intermediate liquid-level range in which the liquid-level height of the injected electrolytic solution is equal to or higher than a first reference height at which the whole electrode opposed part of the electrode body is immersed in the electrolytic solution but is lower than a second reference height at which the electrolytic solution reaches the liquid inlet; and a second liquid-injecting step of injecting the electrolytic solution of a second injection amount that is a remaining amount up to a specified amount while increasing the air pressure in the battery case to a second air pressure higher than the first air pressure and maintaining the liquid-level height of the electrolytic solution within the intermediate liquid-level range.

In the method of Patent Document <NUM>, when the air pressure in the battery case is increased after the first liquid injection, the liquid level of the electrolytic solution excessively lowers, so that the electrode opposed part of the electrode body protrudes from the liquid surface, and thus air is likely to enter the electrode opposed part. When the liquid injection is then restarted to inject the remaining amount of electrolytic solution, the electrolytic solution is less likely to enter the electrode opposed part. It is therefore necessary to slowly inject the electrolytic solution of the remaining amount in order to avoid overflow of the electrolytic solution to the outside of the battery through the liquid inlet. Alternatively, it is necessary to wait until the liquid level of the electrolytic solution sufficiently lowers and then inject the remaining amount of electrolytic solution. Thus, the second liquid injection takes long.

In the foregoing battery producing method, in contrast, in the first liquid injection, the electrolytic solution is injected until the liquid-level height of the injected electrolytic solution falls within the intermediate liquid-level range in which the liquid-level height is equal to or higher than the foregoing first reference height but lower than the foregoing second reference height. When the air pressure in the battery case is increased in the subsequent second liquid-injecting step, the liquid-level height of the electrolytic solution is also maintained in the intermediate liquid-level range and the whole the electrode opposed part is immersed in the electrolytic solution. This can avoid the electrode opposed part from protruding out from the liquid surface and prevent air from entering in the electrode opposed part. In the second liquid-injecting step, accordingly, the remaining second injection amount of the electrolytic solution in can be injected in a short time. The above-described battery producing method can consequently shorten the time required for the liquid injecting than the conventional method described in Patent Document <NUM>, and thus can enhance the productivity of batteries.

Further, in the foregoing method for producing a battery, the second liquid-injecting step may include air pressure increase to intermittently increase the air pressure in the battery case and additional liquid injection to intermittently inject the electrolytic solution, the air pressure increase and the additional liquid injection being alternately repeated.

In the above-described battery producing method, the second liquid-injecting step is configured to alternately repeat the "air pressure increase" to intermittently increase the air pressure in the battery case and the "additional liquid injection" to intermittently inject the electrolytic solution. This configuration can inject the remaining amount of electrolytic solution in a short time by simply performing the second liquid-injecting step.

Further, in the foregoing method for producing a battery, the second liquid-injecting step may include continuously injecting the electrolytic solution while continuously increasing the air pressure in the battery case.

In the above-described battery producing method, the second liquid-injecting step is configured to continuously inject the electrolytic solution while continuously increasing the air pressure in the battery case. This configuration can inject the remaining amount of electrolytic solution in a short time.

A detailed description of a first embodiment according to this disclosure will now be given referring to the accompanying drawings. <FIG> is a perspective view of a battery <NUM> and <FIG> is a longitudinal cross-sectional view of the battery <NUM> in the first embodiment. In the following description, each direction of the battery <NUM>, that is, the longitudinal direction AH, the lateral direction BH, and the thickness direction CH, are defined as illustrated in <FIG>. This battery <NUM> is a rectangular-cross-sectional and airtight lithium-ion secondary battery which is mounted in a vehicle, such as a hybrid car, plug-in hybrid case, and an electric car. The battery <NUM> includes a battery case <NUM>, an electrode body <NUM> accommodated in this battery case <NUM>, a positive terminal member <NUM> and a negative terminal member <NUM> supported on the battery case <NUM>, and others. In the battery case <NUM>, an electrolytic solution <NUM> is contained, a part of which permeates the electrode body <NUM> and the remaining electrolytic solution is accumulated on the bottom of the battery case <NUM>.

The battery case <NUM> is made of metal (e.g., aluminum in the present embodiment) formed in a rectangular parallelepiped box shape, including a case body member <NUM> having a bottom-closed rectangular tube shape having an opening only at an upper end and a case lid member <NUM> having a square plate-like shape welded to the case body member <NUM> so as to close the opening. The case lid member <NUM> of the battery case <NUM> is provided with a liquid inlet <NUM> that is hermetically closed by a sealing member <NUM>. Further, on the case lid member <NUM>, the positive terminal member <NUM> and the negative terminal member <NUM> are fixedly-attached so as to be electrically insulated from the case lid member <NUM>.

The electrode body <NUM> has a flat shape and is encased in a sideways position in the battery case <NUM>. This electrode body <NUM> is configured such that a strip-shaped positive electrode sheet <NUM> including a strip-shaped positive current collecting foil <NUM> whose each principal surface is coated with a positive active material layer <NUM>, a strip-shaped negative electrode sheet <NUM> including a strip-shaped negative current collecting foil <NUM> whose each principal surface is coated with a negative active material layer <NUM>, and a pair of strip-shaped separators <NUM> are stacked one on another and wound together in a flat shape about the axis line.

The electrode body <NUM> includes a positive current collecting part 20e located on one side (a left side in <FIG> and <FIG>) in the lateral direction BH, a negative current collecting part 20f located on the other side (a right side in <FIG> and <FIG>) in the lateral direction BH, and an electrode opposed part <NUM> located between those current collecting parts 20e and 20f. The positive current collecting part 20e is a portion formed of the positive current collecting foil <NUM> of the positive electrode sheet <NUM> and wound in a flat shape. On the other hand, the negative current collecting part 20f is a portion formed of the negative current collecting foil <NUM> of the negative electrode sheet <NUM> and wound in a flat shape. The electrode opposed part <NUM> is a flat wound portion so that the positive active material layers <NUM> of the positive electrode sheet <NUM>, formed on the positive current collecting foil <NUM>, and the negative active material layers <NUM> of the negative electrode sheet <NUM>, formed on the negative current collecting foil <NUM>, are correspondingly opposed to each other through each separator <NUM>.

The method for producing the above-described battery <NUM> will be described below with reference to <FIG>. In an assembly step S1 (see <FIG>), firstly, the battery <NUM> is assembled. Specifically, the case lid member <NUM> is prepared and fixedly attached with the positive terminal member <NUM> and negative terminal member <NUM> as shown in <FIG> and <FIG>. Then, the positive terminal member <NUM> and negative terminal member <NUM> are respectively welded to the positive current collecting part 20e and the negative current collecting part 20f of the electrode body <NUM> which are fabricated separately. Furthermore, this electrode body <NUM> is inserted in the case body member <NUM> and the opening of the case body member <NUM> is closed with the case lid member <NUM>. The case body member <NUM> and the case lid member <NUM> are welded to each other to accomplish the battery case <NUM>.

Subsequently, a liquid injecting step S2 (see <FIG>) is performed, in which a specified amount V of the electrolytic solution <NUM> (e.g., <NUM> in the present embodiment) is injected into the battery case <NUM> through the liquid inlet <NUM> provided in the case lid member <NUM>. This liquid injecting step S2 is carried out by use of a liquid injection device <NUM> shown in <FIG>. This liquid injection device <NUM> includes a vacuum chamber <NUM> in which the battery <NUM> is to be placed, a liquid injection part <NUM> for injecting the electrolytic solution <NUM> into the battery case <NUM>, a control unit <NUM>, and others.

The vacuum chamber <NUM> is attached with a vacuum pump <NUM>, a pressure regulation valve <NUM>, and a pressure sensor <NUM>. As an alternative, a mass flow controller may be used instead of the pressure regulation valve <NUM>.

The liquid injection part <NUM> includes a cylindrical liquid injection nozzle <NUM> for injecting the electrolytic solution <NUM> into the battery case <NUM> and an electrolytic-solution tank <NUM> for storing the electrolytic solution <NUM> in advance. The liquid injection nozzle <NUM> and the electrolytic-solution tank <NUM> are connected to each other through a liquid flow passage <NUM>. In some point of this liquid flow passage <NUM>, there are placed a flow meter <NUM> and a liquid injection valve <NUM>.

The control unit <NUM> includes a microcomputer that includes a CPU, a ROM, and a RAM, which are not shown, and operates according to a predetermined control program stored in the ROM and others. To this control unit <NUM>, there are individually connected the vacuum pump <NUM>, the pressure regulation valve <NUM>, the pressure sensor <NUM>, the flow meter <NUM>, and the liquid injection valve <NUM>. Based on each signal from the pressure sensor <NUM> and the flow meter <NUM>, the control unit <NUM> controls operations of the vacuum pump <NUM>, opening and closing of the pressure regulation valve <NUM>, and opening and closing of the liquid injection valve <NUM>.

Prior to the liquid injecting step S2, the battery <NUM> assembled as above is placed in the vacuum chamber <NUM>, and the tip end of the liquid injection nozzle <NUM> is inserted in advance in the battery case <NUM> through the liquid inlet <NUM>. In a first liquid-injecting step S21 (see <FIG>) of the liquid injecting step S2, the internal pressure of the vacuum chamber <NUM> is reduced from the atmospheric pressure P0 of <NUM> kPa to regulate the air pressure P in the vacuum chamber <NUM> and the battery case <NUM> to a predetermined first air pressure P1 (e.g., <NUM> kPa in the first embodiment) (see a broken-line graph in <FIG>). Under this reduced pressure, then, a predetermined first injection amount V1 (<NUM> in the first embodiment) of the electrolytic solution <NUM> is injected into the battery case <NUM> (see a solid-line graph in <FIG>). The elapsed time t (seconds) in <FIG> means an elapsed time that passes from the start time (t=<NUM>) of reducing the internal air pressure of the vacuum chamber <NUM> (the battery case <NUM>).

The first injection amount V1 of <NUM> is an injection amount determined so that the liquid-level height H of the electrolytic solution <NUM> injected in the battery case <NUM>, which is the height of a liquid surface <NUM> of the electrolytic solution <NUM> from the bottom surface 10b of the battery case <NUM>, can fall within an intermediate liquid-level range AHc (Ha≤H<Hb) in which the liquid-level height H is equal to or higher than the first reference height Ha at which the whole electrode opposed part <NUM> of the electrode body <NUM> is immersed in the electrolytic solution <NUM>, but is lower than the second reference height Hb at which the electrolytic solution <NUM> reaches, or touches, the liquid inlet <NUM> (see <FIG>).

In the first embodiment, the first reference height Ha is a distance from the bottom surface 10b of the battery case <NUM> to an upper end 20a of the electrode body <NUM>; specifically, the first reference height Ha is <NUM> in the first embodiment. The second reference height Hb is a distance from the bottom surface 10b of the battery case <NUM> to the inner upper surface 10a (the lower surface of the case lid member <NUM>) of the battery case <NUM>; specifically, the second reference height Hb is <NUM> in the first embodiment. In contrast, when the electrolytic solution <NUM> of the first injection amount V1, i.e., <NUM>, is injected into the battery case <NUM>, the liquid-level height H of the electrolytic solution <NUM> is about <NUM>.

In this first liquid-injecting step S21, specifically, the control unit <NUM> closes the pressure regulation valve <NUM> and then activates the vacuum pump <NUM> to reduce the internal air pressure of the vacuum chamber <NUM> (see <FIG> and <FIG>). When the air pressure P in the vacuum chamber <NUM> and the battery case <NUM>, detected by the pressure sensor <NUM>, decreases from the atmospheric pressure P0 of <NUM> kPa to the first air pressure P1 of <NUM> kPa, the vacuum pump <NUM> is stopped, the liquid injection valve <NUM> is opened, and injection of the electrolytic solution <NUM> into the battery case <NUM> is started at time t1. Thereafter, when the flow meter <NUM> detects that the electrolytic solution <NUM> of the first injection amount V1 of <NUM> is injected, the liquid injection valve <NUM> is closed. Thus, the liquid-level height H of the injected electrolytic solution <NUM> becomes a height falling within the intermediate liquid-level range AHc (<NUM>≤H<<NUM>), concretely, about <NUM>.

In a second liquid-injecting step S22 (see <FIG>), the electrolytic solution <NUM> of a remaining, second injection amount V2 (= V-V1), e.g., <NUM> in the first embodiment, is injected up to the specified amount V of <NUM> while the air pressure P in the battery case <NUM> is increased to the second air pressure P2 (<NUM> kPa corresponding to the atmospheric pressure P0 in the first embodiment) higher than the first air pressure P1 of <NUM> kPa and the liquid-level height H of the electrolytic solution <NUM> is maintained within the above-described intermediate liquid-level range AHc (<NUM>≤H<<NUM>).

In the first embodiment, the air pressure increase to intermittently increase the air pressure P in the battery case <NUM> and the additional liquid injection to intermittently inject the electrolytic solution <NUM> are alternately repeated. Specifically, as indicated by a broken line in <FIG>, the air pressure P in the battery case <NUM> is intermittently increased in <NUM> stages (P1→ P3→ P4→ P5→ P6→ P7→ P8→ P9→ P2). In contrast, from each of time t3 to time t9 and time t2 at which each air pressure P3 to P9 and P2 is reached, the electrolytic solution <NUM> is intermittently injected by an additional injection amount Va of <NUM> in <NUM> stages.

To be specific, the control unit <NUM> opens the pressure regulation valve <NUM> to gradually increase the air pressure P in the vacuum chamber <NUM> and the battery case <NUM> from the first air pressure P1 of <NUM> kPa. This promotes impregnation of the injected electrolytic solution <NUM> into the electrode body <NUM>, thus gradually decreasing the liquid-level height H of the electrolytic solution <NUM>. This is because the volume VD of the air remaining in the electrode body <NUM> decreases in inverse proportion to the air pressure P as the air pressure P rises (Boyle's law). When the air pressure in the vacuum chamber <NUM> detected by the pressure sensor <NUM> reaches the predetermined air pressure P3 of <NUM> kPa, the pressure regulation valve <NUM> is closed. Accordingly, the liquid-level height H of the electrolytic solution <NUM> decreases by about <NUM> down to about <NUM> (within the intermediate liquid-level range AHc (<NUM> ≤ H < <NUM>)) as indicated by a solid line in <FIG>. At time t3, subsequently, the control unit <NUM> opens the liquid injection valve <NUM> again to restart injection of the electrolytic solution <NUM>. When the flow meter <NUM> then detects that the electrolytic solution <NUM> is additionally injected by the additional injection amount Va of <NUM>, the liquid injection valve <NUM> is closed. Thus, the liquid-level height H of the electrolytic solution <NUM> increases again to about <NUM>.

The air pressure increase to intermittently increase the air pressure P in the battery case <NUM> and the additional injection to intermittently inject the electrolytic solution <NUM> are alternately repeated <NUM> times to inject the electrolytic solution <NUM> of the remaining second injection amount V2, <NUM> (= <NUM> × <NUM>). In the liquid injecting step S2 in the first embodiment, consequently, the electrolytic solution <NUM> of the specified amount V, <NUM>, can be injected in an elapsed time t of <NUM> seconds.

Prior to execution of the first embodiment, it is preferable to determine the magnitude of each air pressure P3 to P9 in advance for example by investigating a relationship between the magnitude of each air pressure P3 to P9 and each additional injection amount Va of the electrolytic solution <NUM> in a battery identical in shape to the battery <NUM> while measuring the liquid-level height H by use of a liquid-level sensor or the like.

Meanwhile, even though the detailed experimental results are omitted, when the method of Patent Document <NUM> is adopted instead of the liquid injecting step S2 in the first embodiment, it is found that it takes an elapsed time t of <NUM> seconds to inject the electrolytic solution <NUM> of the specified amount V of <NUM> to the battery <NUM>. The first embodiment can therefore greatly reduce the time required for the liquid injecting step S2 than the method of Patent Document <NUM>.

After the end of the liquid injecting step S2, the battery <NUM> is taken out of the vacuum chamber <NUM>. In a sealing step S3, subsequently, the liquid inlet <NUM> of the battery <NUM> is hermetically closed with the sealing member <NUM> by welding. This battery <NUM> is then subjected to initial charge and various tests. The battery <NUM> is thus accomplished.

As described above, in the method for producing the battery <NUM>, in the first liquid-injecting step S21, the electrolytic solution <NUM> is injected until the liquid-level height H of the electrolytic solution <NUM> falls within the intermediate liquid-level range AHc (Ha≤H<Hb) in which the liquid-level height H is equal to or higher than the first reference height Ha but is lower than the second reference height Hb. When the air pressure P in the battery case <NUM> is increased in the following second liquid-injecting step S22, similarly, the liquid-level height H of the electrolytic solution <NUM> is maintained within the intermediate liquid-level range AHc (Ha≤H<Hb) and the whole electrode opposed part <NUM> is immersed in the electrolytic solution <NUM>. This can prevent the electrode opposed part <NUM> from protruding out from a liquid surface <NUM> and hence avoid entrance of air into the electrode opposed part <NUM>. Accordingly, in the second liquid-injecting step S22, the remaining second injection amount V2 of the electrolytic solution <NUM> can be injected in a short time. The method for producing the battery <NUM> can therefore shorten the time required for the liquid injecting step S2 than the conventional method described in Patent Document <NUM> and enhance the productivity of the battery <NUM>.

In the first embodiment, furthermore, in the second liquid-injecting step S22, the air pressure increase to intermittently increase the internal air pressure of the battery case <NUM> and the additional liquid injection to intermittently inject the electrolytic solution <NUM> are alternately repeated. This configuration can inject the remaining electrolytic solution <NUM> in a short time by simply performing the second liquid-injecting step S22.

A second embodiment will be described below. In the first embodiment, as described above, in the second liquid-injecting step S22 of the liquid injecting step S2, the remaining amount of the electrolytic solution <NUM> is injected by alternately repeating the air pressure increase to intermittently increase the internal air pressure of the battery case <NUM> and the additional liquid injection to intermittently inject the electrolytic solution <NUM>. In contrast, the second embodiment differs from the first embodiment in that a second liquid-injecting step S122 (see <FIG>) of the liquid injecting step S12 in the second embodiment is performed by continuously injecting the electrolytic solution <NUM> while continuously increasing the air pressure P in the battery case <NUM> (see <FIG>).

In the first liquid-injecting step S21, pressure reduction and liquid injection are performed as in the first embodiment. In the second liquid-injecting step S122, from time tlb, the air pressure P in the vacuum chamber <NUM> and the battery case <NUM> is continuously increased by use of an electropneumatic regulator instead of the pressure regulation valve <NUM> from the first air pressure P1 of <NUM> kPa to the second air pressure P2 of <NUM> kPa corresponding to the atmospheric pressure P0 as shown by a broken line in <FIG> in a curve to which the inclination of a tangent line is larger as the elapsed time t is longer,. On the other hand, the liquid injection valve <NUM> is opened and a constant additional flow rate Ra of the electrolytic solution <NUM> is injected into the battery case <NUM>. Then, as indicated by a solid line in <FIG>, the liquid-level height H of the electrolytic solution <NUM> is maintained at about <NUM>. This is because, as in the first embodiment, the volume VD of the air remaining in the electrode body <NUM> decreases in inverse proportion to the air pressure P as the air pressure P rises (Boyle's law), so that the impregnation of the electrolytic solution <NUM> into the electrode body <NUM> is promoted by just that much.

When the flow meter <NUM> detects that the electrolytic solution <NUM> of the second injection amount V2, <NUM>, is additionally injected, the liquid injection valve <NUM> is closed. In the second embodiment, therefore, the electrolytic solution <NUM> of the specified amount V, <NUM>, can be injected in an elapsed time t of <NUM> seconds, which is shorter than the elapsed time t of <NUM> seconds in the first embodiment.

Prior to execution of the second embodiment, it is preferable to obtain in advance a relationship between the change in the air pressure P and the additional flow rate Ra of the additionally-injected electrolytic solution <NUM>, in which the liquid-level height H is substantially constant, for example by investigating the relationship between the change in each air pressure P and the additional flow rate Ra of the additionally-injected electrolytic solution <NUM> in a battery identical to the battery <NUM> while measuring the liquid-level height H by use of a liquid-level sensor or the like.

The second embodiment can also shorten the time required for the liquid injecting step S2 than the conventional method described in Patent Document <NUM>, thus enabling to enhance the productivity of the battery <NUM>. In the second embodiment, the second liquid-injecting step S122 is performed to continuously inject the electrolytic solution <NUM> while continuously increasing the air pressure P in the battery case <NUM>. Thus, the remaining electrolytic solution <NUM> can be injected in a shorter time than in the second liquid-injecting step S22 in the first embodiment.

The present disclosure is described in the foregoing first and second embodiments but is not limited thereto.

In the first and second embodiments, for instance, the present disclosure is applied to the method for producing the battery <NUM> provided with a flat-shaped wound electrode body <NUM>, but is not limited thereto. For example, the present disclosure is also applicable to a method for producing a battery provided with a laminated electrode body configured such that rectangular positive electrode sheets and rectangular negative sheets are alternately laminated in two or more layers with rectangular separators individually interposed therebetween.

In the first and second embodiments, to meet a relation of P1 < P2, the first air pressure P1 is set lower than the atmospheric pressure and the second air pressure P2 is set equal to the atmospheric pressure (P2 = P0), but they are not limited thereto. An alternative may be set such that the first air pressure P1 is equal to the atmospheric pressure and the second air pressure P2 is higher than the atmospheric pressure. In this case, liquid injection is performed in the first liquid-injecting step without pressure reduction and then the air pressure P is intermittently or continuously increased to the second air pressure P2 in the second liquid-injecting step.

In the first embodiment, as shown in <FIG>, the electrolytic solution <NUM> is additionally intermittently injected <NUM> times by an additional injection amount Va of <NUM> at a time while the air pressure P intermittently changes (P1→ P3→ P4→ P5→ P6→ P7→ P8→ P9→ P2) so as to be gradually larger as time goes by, i.e., as the elapsed time t is longer. Further, the additional injection is carried out so that the liquid-level height H repeatedly changes within a range of about <NUM> to about <NUM>.

However, as an alternative to the first embodiment, it may be arranged to set constant the magnitude of change in the air pressure P intermittently changed while gradually decreasing the additional injection amount Va of electrolytic solution intermittently added and also gradually decreasing the change range of the liquid-level height H changed by the additional injection.

The first injection amount V1 and further the subsequent intermittent changes in air pressure P and additional injection amount Va may be determined so as to keep the liquid-level height H of the electrolytic solution <NUM> within the intermediate liquid-level range AHc (Ha≤H<Hb). The magnitude of increase in air pressure P intermittently caused, the magnitude of additional injection amount Va in each intermittent additional injection, and the change range of the liquid-level height H caused by the additional injections may be set different in each air pressure increase and additional liquid injection.

In the second embodiment, similarly, as shown in <FIG>, the additional flow rate Ra of the electrolytic solution <NUM> in the continuous additional injection is set constant, the change in air pressure P from the first air pressure P1 to the second air pressure P2 (P1→P2) is set to be gradually larger as time goes by, i.e., as the elapsed time t is longer. The additional liquid injection is carried out so that the liquid-level height H is constant (H= about <NUM>).

However, as an alternative to the second embodiment, it may be arranged such that the magnitude of change in air pressure P is changed in an almost linear manner, while the additional flow rate Ra in the additional injection is gradually decreased and the liquid-level height H in the additional injection is constant.

Further, the first injection amount V1 and further the subsequent changes in the air pressure P and additional injection amount Va may be determined so as to keep the liquid-level height H of the electrolytic solution <NUM> within the intermediate liquid-level range AHc (Ha≤H<Hb). The magnitude of increase in air pressure P continuously caused, the magnitude of additional flow rate Ra in additional injection, and the liquid-level height H caused by the additional injection may be changed as the air pressure increase and the additional liquid injection progress.

Claim 1:
A method for producing a battery (<NUM>), the battery (<NUM>) comprising:
a battery case (<NUM>) made of metal, including a liquid inlet (<NUM>);
an electrode body (<NUM>) accommodated in the battery case (<NUM>), the electrode body (<NUM>) including an electrode opposed part (<NUM>) in which a positive active material layer (<NUM>) of a positive electrode sheet (<NUM>) and a negative active material layer (<NUM>) of a negative electrode sheet (<NUM>) are opposed to each other; and
an electrolytic solution (<NUM>) contained in the battery case (<NUM>),
characterized in that
the method comprises injecting (S2, S12) the electrolytic solution (<NUM>) into the battery case (<NUM>) through the liquid inlet (<NUM>),
the injecting (S2, S12) includes:
a first liquid-injecting step (S21) of injecting the electrolytic solution (<NUM>) of a predetermined first injection amount (V1) while air pressure (P) in the battery case (<NUM>) is regulated to a predetermined first air pressure (P1),
the predetermined first injection amount (V1) being determined so that a liquid-level height (H) of the injected electrolytic solution (<NUM>) falls within an intermediate liquid-level range (AHc) (Ha≤H<Hb) in which the liquid-level height (H) of the injected electrolytic solution (<NUM>) is equal to or higher than a first reference height (Ha) at which the whole electrode opposed part (<NUM>) of the electrode body (<NUM>) is immersed in the electrolytic solution (<NUM>) but is lower than a second reference height (Hb) at which the electrolytic solution (<NUM>) reaches the liquid inlet (<NUM>); and
a second liquid-injecting step (S22, S122) of injecting the electrolytic solution (<NUM>) of a second injection amount (V2) (V2=V-V1) that is a remaining amount up to a specified amount (V) while increasing the air pressure (P) in the battery case (<NUM>) to a second air pressure (P2) (P2 > P1) higher than the first air pressure (P1) and maintaining the liquid-level height (H) of the electrolytic solution (<NUM>) within the intermediate liquid-level range (AHc).