Patent Description:
As an electrode plate used for a lithium-ion secondary cell, there has been known a compressed strip-shaped electrode plate formed of a compressed active material layer which has been pressed in its thickness direction and compressed on a strip-shaped current collecting foil. Further, among electrode plates having the above-mentioned configuration, as shown in <FIG>, there is a compressed strip-shaped electrode plate <NUM> configured such that a center portion in a width direction FH constitutes a strip-shaped post-pressed active material portion <NUM> including compressed active material layers <NUM> and <NUM> in a thickness direction GH and both side portions in the width direction FH constitute strip-shaped post-pressed active material absent portions <NUM> having no compressed active material layers <NUM> and <NUM> in the thickness direction GH, respectively.

This compressed strip-shaped electrode plate <NUM> is manufactured by the following method, for example. Specifically, a center portion in the width direction FH of the strip-shaped current collecting foil <NUM> is firstly formed by strip-shaped undried active material layers 905X and 906X, and subsequently, the undried active material layers 905X and 906X are heated and dried to form strip-shaped active material layers 905Z and 906Z. Then, this strip-shaped electrode plate 901Z is conveyed in a longitudinal direction EH and roll-pressed to compact the active material layers 905Z and 906Z in the thickness direction GH so that the compressed active material layers <NUM> and <NUM> are formed. In this manner, the compressed strip-shaped electrode plate <NUM> is manufactured. As an example of a conventional technique, <CIT> can be given.

Further, patent document <CIT> discloses a roll press apparatus according to the preamble of claim <NUM> which includes a returning unit, a roll press forming unit, and a non-coated part heating device. The roll press forming unit includes a pressing roll heating and pressing a coated part of a stripe shaped material in which preset tension is applied. The non-coated part heating device rolls and touches a heating roller on a non-coated part, which is passed through the roll press forming unit, so that the non-coated part is heated to a predetermined temperature and is intensively elongated.

In addition, patent document <CIT> discloses that a work roll having a diameter smaller than that of the pressing roll is pressed to allow the uncoated part to be rolled between the pressing roll and the work roll, and the work roll is held by two backup rolls arranged in a V-shape formation so that the work roll can press the uncoated part with a pressing force uniform in width-wise.

Moreover, patent document <CIT> discloses that in a wrinkling prevention device, a work roll having a diameter smaller than that of a press-roll is pressed against the press-roll, and the work roll is supported by a bearing frame through a backup roll. Further, an edge roller is disposed at an end part of the bearing frame which supports the work roll, and the edge roller is brought into contact with the other press-rolls not in contact with the work roll.

However, when the above-mentioned strip-shaped electrode plate <NUM> is to be roll-pressed, in the active material absent portions 912Z, there might be repeatedly generated oblique wrinkles SW extending obliquely from an inside to an outside of the width direction FH and from an upstream side EUH to a downstream side EDH, especially around a boundary with the active material portion 911Z.

The present disclosure has been made in view of the above circumstances and has a purpose of providing a roll press apparatus that can roll-press a strip-shaped electrode plate with adjusting a balance of a tensile force applied to active material absent portions of the strip-shaped electrode plate and a manufacturing method for a compressed strip-shaped electrode plate that can restrain generation of wrinkles on the active material absent portions by adjusting the balance of the tensile force applied to the active material absent portions of the strip-shaped electrode plate.

The invention is defined by the roll press apparatus according to claim <NUM> and the manufacturing method according to claim <NUM>. One aspect of the present disclosure for solving the above problem is a roll press apparatus configured to form a compressed strip-shaped electrode plate formed with a compressed active material layer, which is formed in a manner that a strip-shaped electrode plate is conveyed in a longitudinal direction to be roll-pressed so that a active material layer is compressed, the strip-shaped electrode plate comprising: an active material portion including a strip-shaped current colleting foil and the active material layer of a strip shape extending over the current collecting foil in the longitudinal direction of the current collecting foil, the active material portion of a strip shape extending in the longitudinal direction and including the active material layer in a thickness direction of the current collecting foil, and an active material absent portion of a strip shape extending in the longitudinal direction and being arranged with the active material portion in a width direction of the current collecting foil, the active material absent portion having no active material layer in the thickness direction and having a thinner thickness than the active material portion, wherein the roll press apparatus includes: a pair of press rolls placed in parallel with a roll gap formed therebetween; and a tensile-force-ratio adjustment mechanism configured to adjust a tensile force ratio of an upstream active material absent portion tensile force and a downstream active material absent portion tensile force to be smaller than in a case of not providing the tensile-force-ratio adjustment mechanism, in an inter-roll active material absent portion held with no compression by the pair of press rolls of the active material absent portion of the strip-shaped electrode plate.

The present inventors have diligently studied and concluded that, when roll-pressing a strip-shaped electrode plate, an active material absent portion (a post-pressed active material absent portion) tends to cause wrinkles or hardly cause wrinkles depending on a value of a tensile force ratio τd / τu of an upstream active material absent portion tensile force τu and a downstream active material absent portion tensile force τd which are applied to inter-roll active material absent portions of the active material absent portion held between a pair of press rolls in an uncompressed manner. From this reason, when roll-pressing by a conventional roll press apparatus, in most cases, an upstream entire tensile force Tu applied to an upstream side of the entire strip-shaped electrode plate before pressing and a downstream entire tensile force Td applied to a downstream side of the entire compressed strip-shaped electrode plate after pressing are set to be equal (Tu = Td).

In the above case, the upstream entire tensile force Tu applied to the strip-shaped electrode plate before roll-pressing is applied entirely and almost equally over the width direction, and thus the upstream active material absent portion tensile force τu applied to the inter-roll active material absent portion of the active material absent portion is small. On the other hand, in the compressed strip-shaped electrode plate after roll-pressing, while the post-pressed active material portion has been extended in a longitudinal direction by pressing, the post-pressed active material absent portion has been hardly extended. Accordingly, most of the downstream entire tensile force Td applied to the compressed strip-shaped electrode plate is not applied to the post-pressed active material portion but only applied to the post-pressed active material absent portion, so that the downstream active material absent portion tensile force τd applied to the inter-roll active material absent portion becomes larger than the upstream active material absent portion tensile force τu (τd > τu). This causes imbalance between the upstream active material absent portion tensile force τu and the downstream active material absent portion tensile force τd which are applied to the inter-roll active material absent portion of the active material absent portion, thereby increasing a tensile force ratio τd / τu. It has been confirmed that the above-mentioned wrinkles SW (see <FIG>) are easily generated when this tensile force ratio τd / τu becomes too large.

To address this problem, the above-mentioned roll press apparatus is provided with the above-mentioned tensile-force-ratio adjustment mechanism. Thus, when roll-pressing the strip-shaped electrode plate, the strip-shaped electrode plate can be roll-pressed to manufacture the compressed strip-shaped electrode plate with adjusting the balance of the tensile force applied to the inter-roll active material absent portion of the active material absent portion, specifically, with adjusting the tensile force ratio τd / τu of the upstream active material absent portion tensile force τu and the downstream active material absent portion tensile force τd which are applied to the inter-roll active material absent portion.

Herein, as a "strip-shaped electrode plate," there is a strip-shaped electrode plate configured such that a strip-shaped active material portion is placed in a center of a width direction and strip-shaped active material absent portions are arranged on both sides in the width direction of this active material portion as mentioned above, for example. Alternatively, there is another example of a strip-shaped electrode plate configured such that a plurality of strip-shaped active material portions and a plurality of strip-shaped active material absent portions are alternately arranged in the width direction.

Further, as the "active material absent portion," other than an active material absent portion formed only of a current collecting foil, there is an active material absent portion formed on a current collecting foil with a protective layer having a thickness thinner than the active material layer as one example.

Further, the above-mentioned roll press apparatus is provided with the tensile-force-ratio adjustment mechanism to adjust the tensile force ratio τd / τu, and an applicable range of this apparatus is not limited to a case that the upstream entire tensile force Tu and the downstream entire tensile force Td are equal (Tu = Td).

Further, another aspect of the present disclosure is a manufacturing method for a compressed strip-shaped electrode plate comprising a strip-shaped current collecting foil and a compressed active material layer which has been compressed in a thickness direction of the current collecting foil, the method including: electrode plate forming of forming a strip-shaped electrode plate, the strip-shaped electrode plate including: an active material portion of a strip shape extending in a longitudinal direction and having an active material layer in a thickness direction, the active material portion including the current collecting foil and the active material layer of a strip shape extending over the current collecting foil in the longitudinal direction of the current collecting foil; and an active material absent portion of a strip shape extending in the longitudinal direction and being arranged in the width direction of the active material portion and the current collecting foil, the active material absent portion having no active material layer in the thickness direction and having a thinner thickness than the active material portion, and pressing of conveying the strip-shaped electrode plate in the longitudinal direction and roll-pressing the strip-shaped electrode plate by a pair of press rolls arranged in parallel with a roll gap formed therebetween to form the compressed strip-shaped electrode plate provided with the compressed active material layer, wherein the pressing is performed with adjusting a tensile force ratio of an upstream active material absent portion tensile force applied to an upstream side and a downstream active material absent portion tensile force applied to a downstream side of an inter-roll active material absent portion to be smaller than in a case of not adjusting the tensile force ratio, which is not compressed but held between the pair of press rolls so that generation of wrinkles in the active material absent portion is restrained.

The above-mentioned manufacturing method for the compressed strip-shaped electrode plate includes the above-mentioned pressing. Accordingly, the compressed strip-shaped electrode plate can be manufactured with restraining generation of the wrinkles in the active material absent portion (post-pressed active material absent portion) by adjusting the balance of the tensile force applied to the inter-roll active material absent portion among the active material absent portion of the strip-shaped electrode plate, specifically, by adjusting the tensile force ratio τd / τu of the upstream active material absent portion tensile force τu and the downstream active material absent portion tensile force τd which are applied to the inter-roll active material absent portion. Further developments of the present disclosure are given in the dependent claims.

A first embodiment of the present disclosure is explained below with reference to the accompanying drawings. <FIG> is a perspective view of a compressed strip-shaped electrode plate <NUM> according to the first embodiment. This compressed strip-shaped electrode plate <NUM> is used for manufacturing a rectangular parallel-piped hermetically sealed lithium-ion secondary battery to be mounted on a vehicle and the like such as a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle. To be specific, the compressed strip-shaped electrode plate <NUM> is a strip-shaped positive electrode plate used for manufacturing a flat-wound shaped or laminated electrode body configuring a battery. In the following explanation, a longitudinal direction EH, a width direction FH, and a thickness direction GH of the compressed strip-shaped electrode plate <NUM> are defined as the ones indicated in <FIG>.

The compressed strip-shaped electrode plate <NUM> includes a current collecting foil <NUM> made of a strip-shaped aluminum foil extending in the longitudinal direction EH with a thickness of about <NUM>. This current collecting foil <NUM> has a first main surface 3a, and on a center portion of the width direction FH extending in the longitudinal direction EH of this first main surface 3a, a first compressed active material layer <NUM> (hereinafter, also simply referred as the "compressed active material layer <NUM>") with a thickness of about <NUM> which has been pressed and compressed in the thickness direction GH is formed in a strip-like shape in the longitudinal direction EH. Further, on a second main surface 3b on an opposite side, a second compressed active material layer <NUM> (hereinafter, also simply referred as the "compressed active material layer <NUM>") with a thickness of about <NUM> which has been pressed and compressed in the thickness direction GH is formed in a strip-like shape in the longitudinal direction EH on a center portion of the width direction FH extending in the longitudinal direction EH of the second main surface 3b. On the other hand, portions on both sides in the width direction FH extending in the longitudinal direction EH of the current collecting foil <NUM> are not provided with the compressed active material layers <NUM> and <NUM>, respectively, and the current collecting foil <NUM> is exposed in the thickness direction GH.

The compressed active material layers <NUM> and <NUM> are each configured with active material particles, conductive particles, and binders. In the present first embodiment, the active material particles are lithium-transition metal composite oxide, more specifically, lithium nickel-manganese-cobalt-oxide particles. Further, the conductive particles are acetylene black (AB) particles, and the binders are polyvinylidene fluoride (PVDF).

This compressed stirp-shaped electrode plate <NUM> is, as mentioned above, formed with the current collecting foil <NUM>, the strip-shaped compressed active material layers <NUM> and <NUM> formed on this current collecting foil <NUM>. In the compressed strip-shaped electrode plate <NUM>, a center portion in the width direction FH is a strip-shaped post-pressed active material portion <NUM> having the compressed active material layers <NUM> and <NUM> in the thickness direction GH. On the other hand, in the compressed strip-shaped electrode plate <NUM>, the both side portions in the width direction FH (portions arranged on both sides in the width direction FH of the post-pressed active material portion <NUM>) are not provided with the compressed active material layers <NUM> and <NUM> in the thickness direction GH, and each of the both sides constitutes a post-pressed active material absent portion <NUM> having a thinner thickness than the post-pressed active material portion <NUM>.

A manufacturing method for the compressed strip-shaped electrode plate <NUM> is now explained (see <FIG>). Firstly, in an "electrode pate forming step S1" (see <FIG>), a strip-shaped electrode plate 1Zbefore being pressed is formed. The electrode plate forming step S1 includes a "first undried layer forming step S11," a "first drying step S12," a "second undried layer forming step S13," and a "second drying step S14" in this order.

In the first undried layer forming step S11, a strip-shaped first undried active material layer 5X is formed on the first main surface 3a of the current collecting foil <NUM>. Specifically, the active material particles (lithium nickel-manganese-cobalt-oxide particles in the present first embodiment), the conductive particles (the AB particles in the present first embodiment), the binders (PVDF in the present first embodiment), and a disperse medium (N-Methyl-pyrrolidone (NMP) in the present first embodiment) are mixed to obtain an active material paste in advance. In this first undried layer forming step S11, the current collecting foil <NUM> is conveyed in the longitudinal direction EH and the active material paste is discharged to the center portion in the width direction FH of the first main surface 3a of the current collecting foil <NUM> by an application die (not shown), so that the strip-shaped first undried active material layer 5X is serially formed on the first main surface 3a of the current collecting foil <NUM>.

Subsequently, in the first drying step S12, the strip-shaped electrode plate obtained in the first undried layer forming step S11 is conveyed into a drying device (not shown) to heat and dry the first undried active material layer 5X by blowing hot air, so that a first active material layer 5Z before being pressed (hereinafter, simply referred as an "active material layer 5Z") is formed.

Subsequently, in the second undried layer forming step S13, as similar to the first undried layer forming step S11, the center portion of the width direction FH of the second main surface 3b on an opposite side of the current collecting foil <NUM> is also formed with a strip-shaped second undried active material layer 6X.

Subsequently, in the second drying step S14, as similar to the first drying step S12, the second undried active material layer 6X of the strip-shaped electrode plate obtained in the second undried layer forming step S13 is heated and dried by blowing hot air, so that a second active material layer 6Z before being pressed (hereinafter, simply referred as an "active material layer 6Z") is formed. Thereafter, this strip-shaped electrode plate 1Z is wound into a roll-like shape by use of a winding device (not shown).

This strip-shaped electrode plate 1Z is formed with the current collecting foil <NUM> and the active material layers 5Z and 6Z. In the strip-shaped electrode plate 1Z, the center portion in the width direction FH is the strip-shaped active material portion 11Z, which is before being pressed, having the active material layers 5Z and 6Z in the thickness direction GH, and the both side portions arranged on both sides in the width direction FH of the active material portion 11Z are the strip-shaped active material absent portions 12Z, which has not yet been pressed, having no active material layers 5Z and 6Z formed in the thickness direction GH, respectively.

Subsequently, in the "pressing step S2" (see <FIG>), the strip-shaped electrode plate 1Z formed in the electrode plate forming step S1 is conveyed in the longitudinal direction EH and roll-pressed by use of a roll press apparatus <NUM> (see <FIG> and <FIG>) to compact each of the active material layers 5Z and 6Z in the thickness direction GH, so that the compressed strip-shaped electrode plate <NUM> provided with the compressed active material layers <NUM> and <NUM> are formed (see also <FIG>).

Herein, the roll press apparatus <NUM> is explained. The roll press apparatus <NUM> is provided with a first press roll <NUM> and a second press roll <NUM> which are arranged in parallel with having a roll gap KA. The roll press apparatus <NUM> further includes a tensile-force-ratio adjustment mechanism <NUM> provided on an upstream side EUH (a left side in <FIG>) of the roll gap KA of the first press roll <NUM> and the second press roll <NUM>, and this tensile-force-ratio adjustment mechanism <NUM> includes an upstream-direction tensile roll <NUM> placed near the roll gap KA.

Further, the roll press apparatus <NUM> is provided with a wind-off device (not shown) to wind off the strip-shaped electrode plate 1Z, which is before being pressed and hereinafter referred as the pre-press strip-shaped electrode plate 1Z, that has been wound into a roll-like shape and to convey the strip-shaped electrode plate 1Z in the longitudinal direction EH and a wind-up device (not shown) to wind the compressed strip-shaped electrode plate <NUM> which has been pressed into a roll-like shape. The roll press apparatus <NUM> is further provided with an upstream-side tensile force applying unit (not shown) between the unwinding device (not shown) and the upstream-direction tensile roll <NUM> to apply an upstream entire tensile force Tu (in the present first embodiment, Tu = <NUM> N) toward the upstream side EUH over the entire width direction FH to apply the force to the strip-shaped electrode plate 1Z during conveyance. Furthermore, the roll press apparatus <NUM> is provided with a downstream-side tensile force applying unit (not shown) to apply a downstream entire tensile force Td (in the present first embodiment, as equal to Tu, Td = Tu = <NUM> N) toward a downstream side EDH over the entire width direction FH to apply the force to the compressed strip-shaped electrode plate <NUM> during conveyance between the roll gap KA of the first press roll <NUM> and the second press roll <NUM> and the winding device (not shown).

The first press roll <NUM> and the second press roll <NUM> are each formed with a roll surface <NUM> and a roll surface <NUM> both of which are made of stainless steel. The first press roll <NUM> and the second press roll <NUM> are each coupled with a motor (not shown), the first press roll <NUM> is rotatable in a clockwise direction in <FIG>, and the second press roll <NUM> is rotatable in a counter-clockwise direction in <FIG>. In the present first embodiment, the strip-shaped electrode plate 1Z that has been wound off from the winding device (not shown) is to be conveyed in the longitudinal direction EH in a manner that the first active material layer 5Z faces upward in <FIG> and <FIG> and the second active material layer 6Z faces downward in <FIG> and <FIG>. Accordingly, in <FIG>, the second press roll <NUM> placed upward comes to contact with the first active material layer 5Z of the strip-shaped electrode plate 1Z, and the first press roll <NUM> placed downward in <FIG> comes to contact with the second active material layer 6Z of the strip-shaped electrode plate 1Z.

Herein, explanation of the active material portion 11Z of the strip-shaped electrode plate 1Z is made separately with explanation about a portion held tightly between the first press roll <NUM> and the second press roll <NUM> in the roll gap KA (the inter-roll active material portion 11Zb corresponding to an obliquely hatched part in <FIG>) and explanation about a portion on an upstream side EUH of the inter-roll active material portion 11Zb, i.e., a portion prior to roll-pressing (a pre-press active material portion 11Za) (see <FIG>). Further, explanation about the active material absent portions 12Z of the strip-shaped electrode plate 1Z is made separately with explanation about a portion which is held between the first press roll <NUM> and the second press roll <NUM> but not compressed (the inter-roll active material absent portions 12Zb) and explanation about a portion on the upstream side EUH of the inter-roll active material absent portions 12Zb, i.e., portions prior to roll-pressing (pre-press active material absent portions 12Za).

The tensile-force-ratio adjustment mechanism <NUM> adjusts the tensile force ratio τd / τu of an upstream active material absent portion tensile force τu applied to the upstream side EUH and a downstream active material absent portion tensile force τd applied to the downstream side EDH in the above-mentioned inter-roll active material absent portions 12Zb. The tensile-force-ratio adjustment mechanism <NUM> of the present first embodiment specifically includes the upstream-direction tensile roll <NUM> as mentioned above, and the active material absent portion 12Z is pressed against the first press roll <NUM> by the upstream-direction tensile roll <NUM> so that the upstream active material absent portion tensile force τu applied to the inter-roll active material absent portions 12Zb can be increased.

To be more specific, the upstream-direction tensile roll <NUM> is an elastic roll provided with a roll center portion <NUM> placed in a center in the width direction FH and roll both-side portions <NUM> placed on both sides of the roll center portion <NUM> in the width direction FH and each formed with a roll surface <NUM> which has a larger diameter than the roll center portion <NUM> and is made of rubber to be elastically deformed. The upstream-direction tensile roll <NUM> is also a follower roll to rotate in association with conveyance of the strip-shaped electrode plate 1Z. In the roll <NUM>, the roll center portion <NUM> having a smaller diameter than the roll both-side portions <NUM> is to face with the pre-press active material portion 11Za of the active material portion 11Z of the strip-shaped electrode plate 1Z with a clearance. On the other hand, the roll surfaces <NUM> of the roll both-side portions <NUM> are pressure-contacted with tensile roll pressure portions 12Zap (obliquely hatched parts in <FIG>) of the pre-press active material absent portions 12Za of the active material absent portions 12Z in the strip-shaped electrode plate 1Z, and these tensile roll pressure portions 12Zap are each pressed against the first press roll <NUM>.

In other words, the roll both-side portions <NUM> of the upstream-direction tensile roll <NUM> are to press the tensile roll pressure portions 12Zap (the current collecting foil <NUM>) of the pre-press active material absent portions 12Za against the first press roll <NUM> to hold and press the pre-press active material absent portions 12Za between the roll both-side portions <NUM> and the first press roll <NUM>. As mentioned above, the upstream-direction tensile roll <NUM> is an elastic roll in which the roll surfaces <NUM> are made of rubber and also a follower roll. Therefore, a magnitude of a rotation resistance of the upstream-direction tensile roll <NUM> changes according to a magnitude of a press-contact force of the upstream-direction tensile roll <NUM> (the roll both-side portions <NUM>) applied to the tensile roll pressure portions 12Zap and the first press roll <NUM>. Namely, when this rotation resistance is increased, a tensile force Tp applied in a direction of the upstream side EUH to the tensile roll pressure portions 12Zap which are press-contacted with the upstream-direction tensile roll <NUM> and the pre-press active material absent portions 12Za on the downstream side EDH of the tensile roll pressure portions 12Zap can be increased.

Thus, it is possible to increase the upstream active material absent portion tensile force τu applied to the inter-roll active material absent portions 12Zb. In the present first embodiment, the upstream-direction tensile roll <NUM> has been adjusted such that the tensile roll pressure portions 12Zap and the pre-press active material absent portions 12Za on the downstream side EDH of the tensile roll pressure portions 12Zap are each pulled toward the upstream side EUH with a tensile force of Tp = <NUM> N. Accordingly, the upstream active material absent portion tensile force τu applied to the inter-roll active material absent portions 12Zb also increases by the tensile force of about Tp = <NUM> N as compared with a case of not providing the upstream-direction tensile roll <NUM>.

In the pressing step S2, the strip-shaped electrode plate 1Z which has been unwound from the unwinding device (not shown) and conveyed in the longitudinal direction EH is roll-pressed by the first press roll <NUM> and the second press roll <NUM> and the active material layers 5Z and 6Z are compressed in the thickness direction GH, so that the compressed strip-shaped electrode plates <NUM> each provided with the compressed active material layers <NUM> and <NUM> are serially manufactured. Thereafter, these compressed strip-shaped electrode plates <NUM> are wound around the winding device (not shown) into a roll-like shape.

In the present first embodiment, the pre-press strip-shaped electrode plate 1Z is subjected to an upstream entire tensile force Tu of <NUM> N in a direction of the upstream side EUH by an upstream-side tensile force applying unit (not shown). This upstream entire tensile force Tu is applied almost uniformly to the strip-shaped electrode plate 1Z over the entire width direction FH. Accordingly, the tensile force Tu2 in a direction of the upstream side EUH applied to the active material absent portions 12Z becomes a small value corresponding to a size of a width W2 of the respective active material absent portions 12Z. In the present first embodiment, a width W of the entire strip-shaped electrode plate 1Z is <NUM>, a width W1 of the active material portion 11Z is <NUM>, and a width W2 of the respective active material absent portions 12Z is <NUM> (W = W1 + <NUM> × W2). Therefore, the tensile force Tu2 in the direction of the upstream side EUH applied to a pair of the active material absent portions 12Z is defined as almost Tu2 = Tu × (W2 / W) = <NUM> × (<NUM> / <NUM>) = <NUM> N.

Further in the present first embodiment, the tensile roll pressure portions 12Zap are pressed against the first press roll <NUM> by the roll both-side portions <NUM> of the upstream-direction tensile roll <NUM> as mentioned above. Thus, the tensile roll pressure portions 12Zap and the pre-press active material absent portions 12Za in a downstream-side EDH range of the tensile roll pressure portions 12Zap are pulled toward the upstream side EUH by a tensile force Tu2' of the original tensile force Tu2 added with the above-mentioned tensile force Tp. As a result of this, the upstream active material absent portion tensile force τu applied to the inter-roll active material absent portions 12Zb of the active material absent portions 12Z is increased by the tensile force Tp as compared with the case of not providing the tensile-force-ratio adjustment mechanism <NUM>. In the present first embodiment, the upstream active material absent portion tensile force τu is roughly defined as τu = Tu2 + Tp = Tu2' = <NUM> + <NUM> = <NUM> N.

The compressed strip-shaped electrode plate <NUM> which has been roll-pressed is entirely subjected to the downward entire tensile force Td in a direction of the downstream side EDH (in the present first embodiment, for example, Td = <NUM> N) by a downstream-side tensile force applying unit (not shown). However, in this compressed strip-shaped electrode plate <NUM> which has been roll-pressed, while the post-pressed active material portion <NUM> is extended in the longitudinal direction EH, the post-pressed active material absent portions <NUM> are hardly pressed due to their thin thickness, so that the post-pressed active material absent portions <NUM> are hardly extended. Accordingly, the downward entire tensile force Td is hardly applied to the post-pressed active material portion <NUM> (the tensile force Td1 applied to the post-pressed active material portion <NUM> ≈ <NUM>), but the downward entire tensile force Td is applied to the two post-pressed active material absent portions <NUM> (see <FIG>). Therefore, the magnitude of the tensile force Td2 in a direction of the downstream side EDH applied to each of the post-pressed active material absent portions <NUM> is almost a half of the downward entire tensile force Td (Td2 = Td / <NUM>). Further, the downward active material absent portion tensile force τd applied to the inter-roll active material absent portions 12Zb is almost equal to the tensile force Td2 in the direction of the downward side EDH applied to the post-pressed active material absent portions <NUM> (τd = Td2). In the present first embodiment, the downward entire tensile force Td is also set as Td = <NUM> N, and thus the tensile force Td2 in the direction of the downward side EDH and the downward active material absent portion tensile force τd are each resulted in Td2 = τd = <NUM> N.

Therefore, providing the tensile-force-ratio adjustment mechanism <NUM> achieves reduction in the tensile force ratio τd / τu of the upstream active material absent portion tensile force τu and the downward active material absent portion tensile force τd which are applied to the inter-roll active material absent portions 12Zb respectively as compared with the case of not providing the tensile-force-ratio adjustment mechanism <NUM>. In the present first embodiment, when the tensile-force-ratio adjustment mechanism <NUM> is not provided, the tensile force results in τd / τu = τd / Tu2 = <NUM> / <NUM> = <NUM>. On the other hand, in the present first embodiment providing the tensile-force-ratio adjustment mechanism <NUM>, the tensile force ratio can be adjusted as τd / τu = τd / Tu2 = <NUM> / <NUM> = <NUM>. The tensile force ratio τd / τu can be thus made small and thereby reducing the imbalance between the tensile forces τd and τu, so that it is possible to restrain generation of wrinkles in the active material absent portions 12Z (the post-pressed active material absent portions <NUM>) in roll-pressing.

In addition, as shown in <FIG>, in the active material portion 11Z, the tensile force applied to the inter-roll active material portion 11Zb held between the first press roll <NUM> and the second press roll <NUM> in the roll gap KA causes the imbalance between the force in the direction of the upstream side EUH and the force in the direction of the downstream side EDH. Namely, the inter-roll active material portion 11Zb is subjected to the tensile force Tu1 in the direction of the upstream side EUH. In the present first embodiment, specifically, the tensile force of Tu1 = Tu × (W1 / W) = <NUM> × (<NUM> / <NUM>) = <NUM> N is applied. However, the inter-roll active material portion 11Zb is hardly subjected to the tensile force Td1 in the direction of the downstream side EDH (the tensile force Td1 ≈ <NUM>). This is because, as mentioned above, while the post-pressed active material portion <NUM> is extended in the longitudinal direction EH, the post-pressed active material absent portions <NUM> are hardly extended, so that the downward entire tensile force Td is hardly applied to the post-pressed active material portion <NUM>.

Incidentally, there is no problem due to the imbalance in the magnitude of this tensile force Tu1 and the tensile force Td1. The inter-roll active material portion 11Zb is firmly held and pressed to be restricted by the first press roll <NUM> and the second press roll <NUM>, and thus the tensile force Tu1 on the upstream side EUH and the tensile force Td1 on the downstream side EDH are not influenced each other.

Next, a second embodiment is explained. The roll press apparatus <NUM> in the first embodiment is exemplified by providing the tensile-force-ratio adjustment mechanism <NUM> including the upstream-direction tensile roll <NUM> as an elastic and follower roll (see <FIG> and <FIG>). On the other hand, a roll press apparatus <NUM> of the present second embodiment is different in a manner that a tensile-force-ratio adjustment mechanism <NUM> including an upstream-direction tensile roll <NUM> as a metal and driving roll is provided (see <FIG> and <FIG>).

The tensile-force-ratio adjustment mechanism <NUM> according to the present second embodiment includes the upstream-side tensile roll <NUM> placed near the roll gap KA on the upstream side EUH of the roll gap KA. This upstream-direction tensile roll <NUM> is a metal roll including a roll center portion <NUM> placed in a center and roll both-side portions <NUM> placed on both sides in the width direction FH of the roll center portion <NUM> and each formed with a roll surface <NUM> having a larger diameter than the roll center portion <NUM> and being made of stainless steel. The upstream-direction tensile roll <NUM> is further a driving roll to be driven and rotated in a counter-clockwise direction in <FIG> by a motor (not shown). The roll center portion <NUM> of a small diameter faces the pre-press active material portion 11Za of the active material portion 11Z of the strip-shaped electrode plate 1Z with a clearance. On the other hand, the roll surfaces <NUM> of the roll both-side portions <NUM> having the large diameter are each press-contacted with the pre-press active material absent portions 12Za of the active material absent portions 12Z of the strip-shaped electrode plate 1Z.

The upstream-direction tensile roll <NUM> is rotated in a counter-clockwise direction at a rotation speed set in a manner that a peripheral speed Vu of the roll both-side portions <NUM> is slower than a peripheral speed V1 of the first press roll <NUM> (Vu < V1) to some extent. Accordingly, in the pre-press active material absent portions 12Za (the current collecting foil <NUM>), the tensile roll pressure portions 12Zaq (the obliquely hatched parts in <FIG>) are press-contacted with the first press roll <NUM> and the roll both-side portions <NUM> of the upstream-direction tensile roll <NUM> and subjected to the tensile force Tq in the direction of the upstream side EUH by a frictional force from the roll both-side portions <NUM> (see <FIG>). Therefore, the tensile roll pressure portions 12Zaq and the pre-press active material absent portions 12Za in the range of the downstream side EDH are pulled toward the upstream side EUH by the tensile force Tu2' (= Tu2 + Tq) which is an addition of the original tensile force Tu2 and the tensile force Tq.

In the present second embodiment, the rotation speed of the upstream-direction tensile roll <NUM> is adjusted by applying the tensile force Tq = <NUM> N which is equal to the tensile force Tp in the first embodiment. As a result of this, the upstream active material absent portion tensile force τu applied to the inter-roll active material absent portions 12Zb is also added by the tensile force Tq = <NUM> N as compared with the case of not providing the upstream-direction tensile roll <NUM>. Further, the downstream active material absent portion tensile force τd is as equal as the case of the first embodiment (τd = <NUM> N).

Accordingly, while the tensile force ratio τd / τu of the upstream active material absent portion tensile force τu and the downstream active material absent portion tensile force τd which are applied to the inter-roll active material absent portions 12Zb is set as τd / τu = <NUM> when the tensile-force-ratio adjustment mechanism <NUM> is not provided, the tensile force ratio can be adjusted to τd / τu = <NUM> in a case that the pressing step S2 is carried out by use of the roll press apparatus <NUM> of the present second embodiment. Also in the present second embodiment, the tensile force ratio τd / τu can be made small and the imbalanced state between the tensile forces τd and τu can be made small, so that it is possible to restrain generation of wrinkles on the active material absent portions 12Z (the post-pressed active material absent portions <NUM>) in roll-pressing.

Next, a third embodiment is explained. The roll press apparatuses <NUM> and <NUM> of the first and second embodiments have been embodied with the tensile-force-ratio adjustment mechanisms <NUM> and <NUM> including the upstream-direction tensile rolls <NUM> and <NUM> to increase the upstream active material absent portion tensile force τu applied to the inter-roll active material absent portions 12Zb, respectively (see <FIG>). On the other hand, a roll press apparatus <NUM> of the present third embodiment is different from those embodiments in a manner that a tensile-force-ratio adjustment mechanism <NUM> including an upstream-direction tensile roll <NUM> to reduce a downstream active material absent portion tensile force τd applied to the inter-roll active material absent portions 12Zb is provided on the downstream side EDH of the roll gap KA (see <FIG>).

As explained in the first embodiment, also in the present third embodiment and a fourth embodiment which will be explained below, the entire roll-pressed compressed strip-shaped electrode plate <NUM> is subjected to a downward entire tensile force Td in a direction of the downward side EDH by a downstream-side tensile force applying unit (not shown, also in the present third embodiment, Td = <NUM> N, for example). While the post-pressed active material portion <NUM> of the compressed strip-shaped electrode plate <NUM> is extended in the longitudinal direction EH by roll-pressing, the post-pressed active material absent portions <NUM> are hardly extended, and thus the downward entire tensile force Td is hardly applied to the post-pressed active material portion <NUM> (the tensile force Td1 ≈ <NUM>) but applied to the two post-pressed active material absent portions <NUM> (see <FIG>). Accordingly, the magnitude of the tensile force Td2 in the direction of the downstream side EDH applied to the post-pressed active material absent portions <NUM> is almost a half of the downward entire tensile force Td (Td2 = Td / <NUM>). Also in the present third and fourth embodiments, the downward entire tensile force is Td = <NUM> N, and accordingly, the tensile force Td2 in the direction of the downstream side EDH is each roughly set as Td2 = <NUM> N.

The tensile-force-ratio adjustment mechanism <NUM> according to the present third embodiment is provided with an upstream-direction tensile roll <NUM> placed on the downstream side EDH of the roll gap KA and near the roll gap KA. This upstream-direction tensile roll <NUM> is an elastically deformable elastic roll formed with a roll surface <NUM> made of rubber in a roll center portion <NUM>, and also a follower roll rotating in association with conveyance of the compressed strip-shaped electrode plate <NUM>. This upstream-direction tensile roll <NUM> is press-contacted with a tensile roll pressure part 11r (in <FIG>, obliquely hatched parts) of the post-pressed active material portion <NUM> of the compressed strip-shaped electrode plate <NUM>, and this tensile roll pressure part 11r is being pressed against the first press roll <NUM> and pulled toward the upstream side EUH, so that the downstream active material absent portion tensile force τd applied to the inter-roll active material absent portions 12Zb is reduced.

The upstream-direction tensile roll <NUM> of the present third embodiment includes the roll center portion <NUM> placed in a center of the width direction FH and roll both-side portions <NUM> placed on both sides in the width direction FH of the roll center portion <NUM> with a smaller diameter than the roll center portion <NUM>. Each of the roll both-side portions <NUM> and the roll center portion <NUM> may have the equal diameter. The roll surface <NUM> of the roll center portion <NUM> is press-contacted with the tensile roll pressure portion 11r of the post-pressed active material portion <NUM> of the compressed strip-shaped electrode plate <NUM>. On the other hand, the roll both-side portions <NUM> face the post-pressed active material absent portions <NUM> of the compressed strip-shaped electrode part <NUM> with a clearance.

To be more specific, the roll center portion <NUM> of the upstream-direction tensile roll <NUM> is to hold and press the tensile roll pressure portion 11r between the roll center portion <NUM> and the first press roll <NUM> by pressing the tensile roll pressure portion 11r of the post-pressed active material portion <NUM> against the first press roll <NUM>. As mentioned above, the upstream-direction tensile roll <NUM> is an elastic and follower roll in which the roll surface <NUM> is elastically deformable. Thus, rotation resistance of the upstream-direction tensile roll <NUM> leads to generation of the tensile force Tr in the direction of the upstream side EUH on the tensile roll pressure portion 11r that has been press-contacted with the roll center portion <NUM> of the upstream-direction tensile roll <NUM>. Herein, the magnitude of the rotation resistance of the upstream-direction tensile roll <NUM> changes according to the magnitude of the press-contact force of the upstream-direction tensile roll <NUM> (the roll center portion <NUM>) applied to the tensile roll pressure portion 11r and the first press roll <NUM>. When this rotation resistance is made larger, it is possible to increase the tensile force Tr in the direction of the upstream side EUH applied to the tensile roll pressure portion 11r which has been press-contacted with the upstream-direction tensile roll <NUM> and the post-pressed active material portion <NUM> on the downstream side EDH downstream of the tensile roll pressure portion 11r.

As shown in <FIG>, the tensile force Tr in the direction of the upstream side EUH applied to the tensile roll pressure portion 11r is applied in an opposite direction from the downward entire tensile force Td which is applied in the entire width direction FH of the pressed compressed strip-shaped electrode plate <NUM>. Accordingly, in a range from the roll gap KA to the tensile roll pressure portion 11r in the compressed strip-shaped electrode plate <NUM>, the downward entire tensile force Td applied to this compressed strip-shaped electrode plate <NUM> in the downward direction can be lessened. Within this range, then, the tensile force Td2' applied to the pressed active material absent portions <NUM> in the direction of the downstream side EDH can be made smaller than the tensile force Td2 (Td2' = (Td - Tr) / <NUM> < Td2 = Td / <NUM>). Therefore, the downstream active material absent portion tensile force τd applied in the direction of the downstream side EDH in the inter-roll active material absent portions 12Zb can also be made small according to the magnitude of the generated tensile force Tr.

In the present third embodiment, the press-contact force of the upstream-direction tensile roll <NUM> is adjusted such that the tensile force Tr is set as Tr = <NUM> N, for example. As a result of this, in the present third embodiment, the tensile force Td2' and the downstream active material absent portion tensile force τd can be set as Td2' = τd = (Td - Tr) / <NUM> = (<NUM> - <NUM>) / <NUM> = <NUM> N, resulting in decrease in the tensile force as compared with the original tensile force Td2 = <NUM> N.

Therefore, also in the present third embodiment, it is possible to reduce the tensile force ratio τd / τu of the upstream active material absent portion tensile force τu and the downstream active material absent portion tensile force τd which are applied to the inter-roll active material absent portions 12Zb. For example, in the present third embodiment, when the tensile-force adjustment mechanism <NUM> is not provided, the tensile force ratio is τd / τu = <NUM> / <NUM> =<NUM>, but on the other hand, when the pressing step S2 is carried out by use of the roll press apparatus <NUM> of the present third embodiment, the tensile force ratio can be adjusted to τd / τu = <NUM> / <NUM> = <NUM>. The tensile force ratio τd / τu is thus made small and the imbalance between the tensile forces τd and τu is made small, thereby achieving restraint in generation of wrinkles in the active material absent portions 12Z (the post-pressed active material absent portions <NUM>) in roll-pressing.

Next, a fourth embodiment is explained. The roll press apparatus <NUM> in the third embodiment is exemplified with providing the tensile force ratio adjustment mechanism <NUM> including the upstream-direction tensile roll <NUM> as an elastic and follower roll (see <FIG>). On the other hand, a roll press apparatus <NUM> in the present fourth embodiment is different from that in the third embodiment in a manner that a tensile-force-ratio adjustment mechanism <NUM> including an upstream-direction tensile roll <NUM> as a metal and driving roll is provided (see <FIG>).

The tensile-force-ratio adjustment mechanism <NUM> according to the present fourth embodiment is provided with an upstream-direction tensile roll <NUM> placed on a downstream side EDH of the roll gap KA and near the roll gap KA. This upstream-direction tensile roll <NUM> is a metal roll having a roll surface <NUM> made of stainless steel in a roll center portion <NUM> and also a driving roll to be driven in a counter-clockwise direction in <FIG> by a motor (not shown). This upstream-direction tensile roll <NUM> is provided with the roll center portion <NUM> placed in a center portion in the width direction FH and roll both-side portions <NUM> placed on both sides of the roll center portion <NUM> in the width direction FH and each having a smaller diameter than the roll center portion <NUM>. Herein, the roll both-side portions <NUM> and the roll center portion <NUM> may have the equal diameter. The roll surface <NUM> of the roll center portion <NUM> is press-contacted with the tensile roll pressure portion <NUM> (the obliquely hatched part in <FIG>) of the post-pressed active material portion <NUM> of the compressed strip-shaped electrode plate <NUM>. Further, the roll both-side portions <NUM> face the post-pressed active material absent portions <NUM> of the compressed strip-shaped electrode plate <NUM> with a clearance, respectively.

The upstream-direction tensile roll <NUM> is configured to rotate in the counter-clockwise direction such that a peripheral speed Vd of the roll center portion <NUM> is some slower than a peripheral speed V1 of the first press roll <NUM> (Vd < V1). Therefore, in the post-pressed active material portion <NUM>, the tensile roll pressure portion <NUM> (the obliquely hatched part in <FIG>) is press-contacted with the first press roll <NUM> and the roll center portion <NUM>, and thus the tensile force Ts in the direction of the upstream side EUH is generated by a friction force applied by this roll center portion <NUM> (see <FIG>).

Also in the present fourth embodiment as similar to the third embodiment, as shown in <FIG>, the tensile force Ts applied to the tensile roll pressure portion <NUM> in the direction of the upstream side EUH faces opposite to the downstream entire tensile force Td applied to the compressed strip-shaped electrode plate <NUM> over the entire width direction FH. Thus, in the range of the compressed strip-shaped electrode plate <NUM> from the roll gap KA to the tensile roll pressure portion <NUM>, it is possible to lessen the downstream entire tensile force Td applied to the compressed strip-shaped electrode plate <NUM>. Accordingly, in this range, the tensile force Td2' applied to the post-pressed active material absent portions <NUM> in the direction of the downstream side EDH can be made smaller than the tensile force Td2 (Td2' = (Td - Ts) / <NUM> < Td2 = Td / <NUM>). Therefore, the downstream active material absent portion tensile force τd applied in the direction of the downstream side EDH in the respective inter-roll active material absent portions 12Zb can also be made small according to the generated tensile force Ts.

Also in the present fourth embodiment, the rotation speed of the upstream-direction tensile roll <NUM> is adjusted such that the tensile force Ts is set as Ts = <NUM> N. Therefore, also in the present fourth embodiment, the tensile force Td2' and the downstream active material absent tensile force τd can be set as Td2' = τd = (Td - Ts) / <NUM> = (<NUM> - <NUM>) / <NUM> = <NUM> N, thereby reducing the forces as compared with the original tensile force Td2 = <NUM> N.

Therefore, also in the present fourth embodiment, the tensile force ratio τd / τu of the upstream active material absent portion tensile force τu and the downstream active material absent portion tensile force τd which are applied to the inter-roll active material absent portions 12Zb can be made small. For example, in the present fourth embodiment, while the tensile force ratio is set as τd / τu = <NUM> in a case that the tensile-force-ratio adjustment mechanism <NUM> is not provided, the tensile force ratio can be adjusted as τd / τu = <NUM> / <NUM> = <NUM> as similar to the third embodiment in a case that the pressing step S2 is carried out by use of the roll press apparatus <NUM> of the present fourth embodiment. This reduction in the tensile force ratio τd / τu and reduction in the imbalance between the tensile forces τd and τu can also achieve restraint in generation of wrinkles on the active material absent portions 12Z (the post-pressed active material absent portions <NUM>) in roll-pressing.

Next, a fifth embodiment is explained. A roll press apparatus <NUM> of the present fifth embodiment is provided with a tensile-force-ratio adjustment mechanism <NUM> (see <FIG>) including a downstream-side driving roll (a downstream-direction tensile roll) <NUM> to press the post-pressed active material portion <NUM> after roll-pressing against the first press roll <NUM> and pull the post-pressed active material portion <NUM> toward the downstream side EDH. This downstream-side driving roll <NUM> is placed on the downstream side EDH of the roll gap KA between the first press roll <NUM> and the second press roll <NUM> and near the roll gap KA. The downstream-side driving roll <NUM> is a metal roll provided with a roll center portion <NUM> formed with a roll surface <NUM> made of stainless steel and a driving roll to be driven and rotated in a counter-clockwise direction in <FIG> by a motor (not shown).

The downstream-side driving roll <NUM> is formed with the roll center portion <NUM> placed in a center portion in the width direction FH and roll both-side portions <NUM> placed on both sides of the roll center portion <NUM> in the width direction FH and each having a smaller diameter than the roll center portion <NUM>. Herein, the roll both-side portions <NUM> and the roll center portion <NUM> may have the equal diameter. The roll surface <NUM> of the roll center portion <NUM> is to be press-contacted with a roll pressure portion 11t (an obliquely hatched part in <FIG>) of the post-pressed active material portion <NUM> of the compressed strip-shaped electrode plate <NUM>. On the other hand, each of the roll both-side portions <NUM> faces the post-pressed active material absent portion <NUM> of the compressed strip-shaped electrode plate <NUM> with a clearance therebetween.

The downstream-direction driving roll <NUM> is to rotate in an opposite direction from the first press roll <NUM> at a rotation speed some faster in the peripheral speed Vd of the roll center portion <NUM> than the peripheral speed V1 of the first press roll <NUM> (Vd > V1). As mentioned above, in the compressed strip-shaped electrode plate <NUM> which has been roll-pressed, while the post-pressed active material portion <NUM> has been extended in the longitudinal direction EH by pressing, the post-pressed active material absent portion <NUM> has hardly been extended. Therefore, when the downstream-direction driving roll <NUM> is not provided, the post-pressed active material portion <NUM> gets loosened.

To address this, in the present fifth embodiment, the downstream-direction driving roll <NUM> rotates at the fast peripheral speed Vd with pressing the post-pressed active material portion <NUM> against the first press roll <NUM>. By this fast rotation, the post-pressed active material portion <NUM> which has been pressed and loosened is sequentially fed out to the downstream side EDH, so that there is no loosening generated in the post-pressed active material portion <NUM> between the roll gap KA and the downstream-direction driving roll <NUM> and the compressed strip-shaped electrode plate <NUM> results in a stretched state over the entire width direction FH.

Accordingly, when there is no downstream-direction driving roll <NUM> provided, the downward entire tensile force Td (= <NUM> N) is hardly applied to the post-pressed active material portion <NUM> (the tensile force Td1 applied to the inter-roll active material portion 11Zb is set as Td1 ≈ <NUM>), so that the downstream active material absent portion tensile force τd applied to the two inter-roll active material absent portions 12Zb becomes large (τd = Td / <NUM> = <NUM> N) (see <FIG>).

To address this, in the present fifth embodiment, a part of the downstream entire tensile force Td is made to be applied to the post- pressed active material portion <NUM> (the tensile force Td1 is also applied to the inter-roll active material portion 11Zb), and thus the downstream active material absent portion tensile force τd applied to the two inter-roll active material absent portions 12Zb is made small by that force (see <FIG>). Specifically, a position of providing the downstream-side driving roll <NUM> and the peripheral speed Vd of the downstream-side driving roll <NUM> are adjusted to make the downstream active material absent tensile force τd applied to the respective inter-roll active material absent portions 12Zb as small as τd = <NUM> N.

Accordingly, also in the present fifth embodiment, the tensile force ratio τd / τu of the upstream active material absent portion tensile force τu and the downstream active material absent portion tensile force τd which are applied to the inter-roll active material absent portions 12Zb can be made small. For example, in the present fifth embodiment, while the tensile force ratio is set as τd / τu = <NUM> when the tensile-force-ratio adjustment mechanism <NUM> is not provided, the tensile force ratio can be adjusted as τd / τu = <NUM> / <NUM> = <NUM>, when the pressing step S2 is carried out by use of the roll press apparatus <NUM> of the present fifth embodiment as similar to the third and fourth embodiments. Reduction in the tensile force ratio τd / τu and reduction in the imbalance between the tensile forces τd and τu in this manner also leads to restraint in generation of wrinkles on the active material absent portions 12Z (the post-pressed active material absent portions <NUM>) in roll-pressing.

It is now explained about results of an experiment carried out for inspecting a relationship between wrinkles generated on the current collecting foil <NUM> constituting the post-pressed active material absent portion <NUM> and a value of the tensile force ratio τd / τu (see a table <NUM> and <FIG>). As indicated in the table <NUM>, the compressed strip-shaped electrode plates <NUM> according to examples <NUM> to <NUM> are manufactured and a depth SF (mm) of the wrinkles generated on the current collecting foil <NUM> constituting the post-pressed active material absent portion <NUM> is inspected. To be specific, the electrode plate forming step S1 is carried out and the strip-shaped electrode plates 1Z are formed. Thereafter, a roll press apparatus with no tensile-force-ratio adjustment mechanism <NUM> provided in the above-mentioned roll press apparatus <NUM> is used as a usual roll press apparatus (not shown) for performing the pressing step S2 to manufacture the compressed strip-shaped electrode plates <NUM>. However, in the respective examples, an upstream-side tensile force applying unit (not shown) changes the magnitude of the upstream entire tensile force Tu applied to the entire width direction FH of the strip-shaped electrode plate 1Z which is being conveyed and the magnitude of the downstream entire tensile force Td applied to the entire width direction FH of the compressed strip-shaped electrode plate <NUM> during conveyance so that the compressed strip-shaped electrode plate <NUM> in the respective examples are manufactured.

Thereafter, the compressed strip-shaped electrode plates <NUM> of the respective examples are each measured with a depth SF (mm) of the wrinkles generated on the current collecting foil <NUM> constituting the post-pressed active material absent portion <NUM>. Specifically, the current collecting foil <NUM> constituting the post-pressed active material absent <NUM> is cut out from each of the compressed strip-shaped electrode plate <NUM> in the respective examples by <NUM> in the longitudinal direction EH. Then, the thus cut-out current collecting foil <NUM> is disposed on an electrostatic adsorption stage to be electrostatically adsorbed, and thereby the depth SF of the wrinkles is measured by a laser microscope with a flat portion having no wrinkles (dents) as a reference.

A relationship between the tensile force ratio τd / τu of the tensile forces τu and τd applied to the inter-roll active material absent portions 12Zb of the active material absent portions 12Z and the depth SF (mm) of the wrinkles generated on the current collecting foil <NUM> constituting the post-pressed active material absent portions <NUM> is shown in a graph of <FIG>.

In the present experiments, the upstream active material absent portion tensile force τu is calculated by τu = Tu × (W2 / W) = Tu × (<NUM> / <NUM>). On the other hand, the downstream active material absent portion tensile force τd is calculated by τd = Td / <NUM>.

As clear from <FIG>, when the tensile force ratio τd / τu is too large such as about equal to or larger than <NUM>, deep wrinkles over a depth of <NUM> are generated on the post-pressed active material absent portions <NUM>. On the other hand, when the tensile force ratio τd / τu is made small to reduce the imbalance between the tensile forces τd and τu such as at least within a range of τd / τu ≤ <NUM>, it has been confirmed that there are hardly generated wrinkles on the post-pressed active material absent portions <NUM>. Accordingly, it can be understood that the roll press apparatuses <NUM> to <NUM> provided with the tensile-force-ratio adjustment mechanisms <NUM> to <NUM> as shown in the first to fifth embodiments are preferably used to reduce the tensile force ratio τd / τu and reduce the imbalance between the tensile forces τd and τu, specifically by adjusting the tensile force ratio as τd / τu ≤ <NUM> and carrying out the pressing step S2. On the other hand, the productivity of the compressed strip-shaped electrode plates <NUM> can be made preferable by enlarging the downstream active material absent portion tensile force τd to some extent and carrying out the pressing step S2 with the tensile force ratio τd / τu to be set as τd / τu ≥ <NUM>. Therefore, it is preferable to set the tensile force ratio τd / τu as τd / τu ≤ <NUM> and further preferably, set as <NUM> ≤ τd / τu ≤ <NUM>.

As explained above, the roll press apparatuses <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> of the first to fifth embodiments are provided with the tensile-force-ratio adjustment mechanisms <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, respectively. When the strip-shaped electrode plate 1Z is to be roll-pressed by using these roll press apparatuses <NUM> and others, the strip-shaped electrode plate 1Z can be roll-pressed with adjusting the balance of the tensile force applied to the inter-roll active material absent portions 12Zb of the active material absent portions 12Z, specifically, adjusting the tensile force ratio τd /τu of the upstream active material absent portion tensile force τu and the downstream active material absent portion tensile force τd which are applied to the inter-roll active material absent portion 12Zb, and thus the compressed strip-shaped electrode plate <NUM> can be manufactured.

Further, in the first and second embodiments, the tensile-force-ratio adjustment mechanisms <NUM> and <NUM> include the upstream-direction tensile rolls <NUM> and <NUM>, respectively, and thus it is possible to increase the upstream active material absent portion tensile force τu which is applied to the inter-roll active material absent portion 12Zb of the active material absent portion 12Z. In this manner, only by a simple configuration of providing the upstream-direction tensile rolls <NUM> and <NUM>, the tensile force ratio τd /τu can be made small and the imbalance between the tensile forces τd and τu can be made small.

On the other hand, in the third and fourth embodiments, the tensile-force-ratio adjustment mechanisms <NUM> and <NUM> include the upstream-direction tensile rolls <NUM> and <NUM>, respectively, and thus it is possible to reduce the downstream active material absent portion tensile force τd which is applied to the inter-roll active material absent portions 12Zb of the active material absent portions 12Z. In this manner, only by a simple configuration of providing the upstream-direction tensile rolls <NUM> and <NUM>, the tensile force ratio τd /τu can be made small and the imbalance between the tensile forces τd and τu can be made small.

Further, in the fifth embodiment, the tensile-force-ratio adjustment mechanism <NUM> includes the downstream-side driving roll <NUM>, and thus the downstream active material absent portion tensile force τd which is applied to the inter-roll active material absent portions 12Zb of the active material absent portions 12Z can be reduced. In this manner, only by a simple configuration of providing the downstream-side driving roll <NUM>, the tensile force ratio τd /τu can be made small and the imbalance between the tensile forces τd and τu can be made small.

In the manufacturing method for the compressed strip-shaped electrode plate <NUM> of the embodiments <NUM> to <NUM>, in the pressing step S2, the balance of the tensile force applied to the inter-roll active material absent portions 12Zb of the active material absent portions 12Z of the strip-shaped electrode plate 1Z is adjusted, more specifically, the tensile force ratio τd /τu of the upstream active material absent portion tensile force τu and the downstream active material absent portion tensile force τd which are applied to the inter-roll active material absent portions 12Zb is adjusted to manufacture the compressed strip-shaped electrode plate <NUM> with restraining generation of the wrinkles on the active material absent portions 12Z (the post-pressed active material absent portions <NUM>). Accordingly, the compressed strip-shaped electrode plate <NUM> restrained with generation of the wrinkles can be further appropriately obtained. Especially, the tensile force ratio is set as τd /τu ≤ <NUM> so that the compressed strip-shaped electrode plate <NUM> in which generation of the wrinkles is restrained can be appropriately obtained by further restraining generation of the wrinkles on the active material absent portions 12Z (the post-pressed active material absent portions <NUM>). Furthermore, the tensile force ratio is set as τd /τu ≥ <NUM>, and thus the productivity of the compressed strip-shaped electrode plate <NUM> can be made preferable.

The present disclosure has been explained in the first to fifth embodiments mentioned above, but the present disclosure is not limited to the first to fifth embodiments and may naturally be applied with modifications in an appropriate manner without departing from the scope of the disclosure.

Claim 1:
A roll press apparatus (<NUM>;<NUM>;<NUM>;<NUM>;<NUM>) configured to form a compressed strip-shaped electrode plate (<NUM>) formed with a compressed active material layer (<NUM>,<NUM>), which is formed in a manner that a strip-shaped electrode plate (1Z) is conveyed in a longitudinal direction (EH) to be roll-pressed so that an active material layer (5Z,6Z) is compressed,
the strip-shaped electrode plate (1Z) comprising:
an active material portion (11Z) including a strip-shaped current colleting foil (<NUM>) and the active material layer (5Z,6Z) of a strip shape extending over the current collecting foil (<NUM>) in the longitudinal direction (EH) of the current collecting foil (<NUM>), the active material portion (11Z) of a strip shape extending in the longitudinal direction (EH) and including the active material layer (5Z,6Z) in a thickness direction (GH) of the current collecting foil (<NUM>), and
an active material absent portion (12Z) of a strip shape extending in the longitudinal direction (EH) and being arranged with the active material portion (11Z) in a width direction (FH) of the current collecting foil (<NUM>), the active material absent portion (12Z) having no active material layer (5Z,6Z) in the thickness direction (GH) and having a thinner thickness than the active material portion (11Z), wherein
the roll press apparatus (<NUM>;<NUM>;<NUM>;<NUM>;<NUM>) includes:
a pair of press rolls placed in parallel with a roll gap formed therebetween; and
characterized in that the roll press apparatus includes
a tensile-force-ratio adjustment mechanism (<NUM>;<NUM>;<NUM>;<NUM>;<NUM>) configured to adjust a tensile force ratio (τd / τu) of an upstream active material absent portion tensile force (τu) and a downstream active material absent portion tensile force (τd) to be smaller than in a case of not providing the tensile-force-ratio adjustment mechanism, in an inter-roll active material absent portion (12Zb) held with no compression by the pair of press rolls (<NUM>,<NUM>) of the active material absent portion (12Z) of the strip-shaped electrode plate (1Z).