JP2017228429A - Method for manufacturing electrode plate of wound type secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an electrode plate, by which the rise in battery resistance can be reduced by suppressing an electrolyte solution in an electrode body from being squeezed out thereof even in the case of suffering repeated high-rate charge/discharge when used for a wound type secondary battery.SOLUTION: A method for manufacturing an electrode plate 31 comprises: a roll-coating step for applying a first paste layer 37s onto a transfer roll ROB; a transfer step for transferring the first paste layer to a piece of belt-shaped current collector foil 32 placed in a first gap Gbc between a feed roll ROC and the transfer roll ROB to form an active material paste layer 38; and a drying step for drying the active material paste layer to form an active material layer 33. In the transfer step, the transfer is performed while spreading a granulated material 36 in a longitudinal direction LH with a peripheral velocity Vc of the feed roll faster than a peripheral velocity Vb of the transfer roll, thereby forming the convex portion-distributed paste layer 38 with many paste convex portions 38p distributed and spread to become longer in the longitudinal direction. In the drying step, the convex portion-distributed paste layer is dried, thereby forming the convex portion-distributed active material layer 33 with many active material convex portions 33p distributed and spread to become longer in the longitudinal direction.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for producing a strip-shaped electrode plate used for a wound type secondary battery.

Conventionally, as a secondary battery such as a lithium ion secondary battery (hereinafter, also simply referred to as a battery), a battery in which an electrolyte solution is impregnated in a laminated type or a wound type electrode body is known.
In these batteries, when high-rate charge / discharge is repeatedly performed, deterioration such as an increase in battery resistance may occur. It is considered that due to the rapid expansion and contraction of the electrode body due to the high-rate charge / discharge, the electrolytic solution held in the electrode body is pushed out, thereby causing uneven concentration in the electrolytic solution in the electrode body.

  In addition, in the case of a battery having a wound electrode body, the above-described extrusion of the electrolyte solution to the outside moves the electrolyte solution in the axial direction along the axis line of the wound electrode body, that is, a strip-shaped electrode plate ( It appears as movement of the electrolyte in the width direction of the positive electrode plate and the negative electrode plate).

JP 2014-139888 A

  The present invention has been made in view of such a problem, and when used in a wound secondary battery, the electrolyte retained in the electrode body is externally exposed even when high-rate charge / discharge is repeatedly performed. An object of the present invention is to provide a method for producing an electrode plate for a wound secondary battery that can suppress extrusion and suppress an increase in battery resistance.

  In one embodiment of the present invention for solving the above problems, a paste having a granulated body containing at least active material particles, a thickener, and a solvent is applied to a strip-shaped current collector foil extending in the longitudinal direction and dried. A wound-type secondary battery electrode plate manufacturing method for manufacturing a strip-shaped electrode plate having a strip-shaped active material layer extending in the longitudinal direction, wherein the paste is applied on a transfer roll to form a first electrode plate. A roll coating step for forming a paste layer, and a coating on the transfer roll in the roll coating step on the current collector foil passed through a first gap between the feed roll for feeding the current collector foil and the transfer roll. A transfer step of transferring the first paste layer formed to form an active material paste layer, and a drying step of drying the active material paste layer to form the active material layer, the transfer step comprising: The peripheral speed Vc of the feed roll for feeding the current collector foil The active material paste layer is transferred to the current collector foil while extending in the longitudinal direction, the granulated body supplied to the first gap, faster than the peripheral speed Vb of the recording roll (Vc> Vb). Forming a convex distribution paste layer in which a large number of paste convexes extending in the longitudinal direction are distributed, and the drying step dries the convex distribution paste layer to form the active material layer in the longitudinal direction. This is a method for manufacturing an electrode plate for a wound secondary battery, in which a convex-distributed active material layer in which a large number of active material convex portions extending long is distributed.

Generally, when manufacturing an electrode plate, it is usual to form a paste layer and an active material layer so that the surface of the paste layer applied to the current collector foil and the active material layer obtained by drying the paste layer may be flat.
On the other hand, in the method for manufacturing an electrode plate for a wound secondary battery of the present invention, in the transfer step, the peripheral speed Vc of the feed roll that feeds the current collector foil is faster than the peripheral speed Vb of the transfer roll (Vc> Vb In addition, the granulated material supplied to the first gap is transferred to the current collector foil while extending in the longitudinal direction to form a convex distribution paste layer in which a large number of paste convexes extending in the longitudinal direction are distributed. To do. Further, this is dried in a drying step to form a convexity distribution active material layer in which a large number of active material projections extending in the longitudinal direction are distributed.

  The band-shaped electrode plate having the convex distribution active material layer thus manufactured is wound as at least one of a positive electrode plate or a negative electrode plate to form a wound electrode body, and further accommodated in a battery case, A secondary battery is formed by impregnating with the electrolytic solution. In this secondary battery, even if high-rate charge / discharge is repeated, the active material layer of the negative electrode plate or the positive electrode plate is provided with the active material projections extending in the longitudinal direction, so that it was held in the electrode body. It is possible to suppress the electrolytic solution from being pushed out, and to suppress an increase in battery resistance.

  Patent Document 1 describes a technique for forming a plurality of concave wrinkles extending in a direction (width direction) perpendicular to the longitudinal direction of the electrode plate as a non-aqueous secondary battery electrode plate. However, in the technique described in the cited document 1, the direction in which the wrinkles are formed is the width direction, which is completely different from the electrode plate of the present invention. It cannot be suppressed.

  In addition, this invention is applicable to both a negative electrode plate and a positive electrode plate as an electrode plate for winding type | mold secondary batteries. Examples of the negative electrode plate include those having a negative electrode active material layer on a current collector foil made of copper foil, and examples of the positive electrode plate include those having a positive electrode active material layer on a current collector foil made of aluminum foil. It is done.

  Examples of the negative electrode active material particles used in the negative electrode active material layer and the negative electrode active material granule include graphite particles such as flaky graphite and spheroidized graphite. Moreover, as a thickener used for a negative electrode active material layer and a negative electrode active material granulation body, sodium polyacrylate and the sodium salt of carboxymethylcellulose (CMC) are mentioned. Water is mentioned as a solvent used for a negative electrode active material granulation body.

As a positive electrode active material particle used for a positive electrode active material layer and a positive electrode active material granule, the particle | grains which consist of lithium transition metal complex oxide are mentioned, for example. Examples of the lithium transition metal composite oxide include lithium nickel cobalt manganese based composite oxide containing nickel (Ni), cobalt (Co) and manganese (Mn) as transition metals, and nickel and manganese as transition metals. Examples thereof include lithium nickel manganese composite oxide, lithium nickelate (LiNiO ₂ ), lithium cobaltate (LiCoO ₂ ), and lithium manganate (LiMn ₂ O ₄ ).
Moreover, CMC (aqueous type) and PVDF (non-aqueous type) are mentioned as a thickener used for a positive electrode active material layer and a positive electrode active material granulation body. In addition to the positive electrode active material particles and the thickener, the positive electrode active material layer and the positive electrode active material granule include, for example, conductive materials such as graphite, carbon black, and acetylene black, polyvinylidene fluoride (PVDF), poly A binder such as tetrafluoroethylene (PTFE) can be included. NMP and water are mentioned as a solvent used for a positive electrode active material granulation body.

  In the roll coating process, as a method of applying the paste on the transfer roll, the paste is supplied between the supply roll prepared separately from the transfer roll and the feed roll and the transfer roll described above, and the peripheral speed of the supply roll Also, there is a method of increasing the peripheral speed Vc of the transfer roll and applying the paste onto the transfer roll. Alternatively, the paste layer applied on the supply roll may be transferred onto the transfer roll using a doctor blade or the like.

  In the transfer step, the peripheral speed Vc of the feed roll is made faster than the peripheral speed Vb of the transfer roll, and the granule supplied to the first gap is transferred to the current collector foil while extending in the longitudinal direction. Further, the peripheral speeds Vc and Vb at which the convex portion distribution paste layer in which a large number of paste convex portions extending long in the longitudinal direction are distributed are selected.

  Furthermore, in the above-described method for manufacturing a wound secondary battery electrode plate, the roll coating step supplies the paste to a second gap between a supply roll and the transfer roll, and the transfer roll A method of manufacturing a wound secondary battery electrode plate on which the first paste layer is formed is preferable.

In the roll coating step, the paste is supplied to the second gap between the supply roll and the transfer roll to form a first paste layer on the transfer roll. Thereafter, when the paste is transferred to the current collector foil between the transfer roll and the feed roll to form the convex portion distribution paste layer, 2 between the supply roll and the transfer roll and between the transfer roll and the feed roll. Since the thickness can be adjusted in stages, there is an advantage that the adjustment range of the thickness (coating weight) of the convex portion distribution paste layer can be widened and the thickness of the convex portion distribution paste layer can be adjusted with high accuracy.
In order to form the first paste layer on the transfer roll, a paste pool is preferably provided between the supply roll and the transfer roll, and the second paste layer is formed on the transfer roll through the second gap. Further, there is a method in which a second paste layer is once formed on a supply roll, this second paste layer is supplied to the second gap and transferred to a transfer roll to form the first paste layer. When the second paste layer is thus formed on the supply roll and transferred to the transfer roll, the thickness can be further adjusted at the stage of forming the second paste layer on the supply roll. The thickness adjustment of the first paste layer and further the convex portion distribution paste layer can be performed more appropriately.

  Furthermore, it is a manufacturing method of the electrode plate for wound secondary batteries according to any one of the above, wherein the paste has a solids content NV of 68 to 96 (wt%), and the transfer step includes the paste When the solid content ratio NV is 70 ≦ NV ≦ 95 (wt%), the peripheral speed ratio Vc / Vb between the peripheral speed Vc of the feed roll and the peripheral speed Vb of the transfer roll is 10 ≦ Vc. When the solid content ratio NV of the paste is 68 ≦ NV <70 (wt%), the peripheral speed ratio Vc / Vb is set to 18 ≦ Vc / Vb ≦ 30. When the solid content ratio NV of the paste is 95 <NV ≦ 96 (wt%), the peripheral speed ratio Vc / Vb is selected from the range of 10 ≦ Vc / Vb ≦ 12 A method for manufacturing an electrode plate for a wound secondary battery is preferable.

In the transfer process, in order to appropriately form a convex portion distribution paste layer in which a large number of paste convex portions extending long in the longitudinal direction are distributed, the peripheral speed Vc of the feed roll and the transfer roll according to the solid content ratio NV of this paste The inventor has found that the peripheral speed ratio Vc / Vb with respect to the peripheral speed Vb should be selected from an appropriate range so that a larger peripheral speed ratio should be selected than when a flat paste layer is formed.
In the present invention, the range of the peripheral speed ratio Vc / Vb to be selected is determined in accordance with the solid content ratio NV of the paste, whereby the convex distribution paste layer can be appropriately formed in the transfer step. It is possible to appropriately form a convex portion distribution paste layer in which a large number of paste convex portions are distributed in the transfer step, and furthermore, a convex portion distribution active material layer in which a large number of active material convex portions are distributed in the drying step.

That is, when the solid content ratio of the paste to be used is in the range of 70 ≦ NV ≦ 95 (wt%), the peripheral speed ratio Vc / Vb is selected from the range of 10 ≦ Vc / Vb ≦ 30. Since the solid content ratio NV is low and a large amount of solvent is contained, the granulated body is easily deformed. Therefore, when the peripheral speed ratio Vc / Vb is low, that is, when Vc / Vb <10, the active material The paste layer becomes flat, and paste protrusions that extend long in the longitudinal direction are not formed. On the other hand, in the case of Vc / Vb> 30, the unevenness generated in the formed active material paste layer becomes too large, and so-called “scratch” (fading of the paste) occurs in some cases.
When the solid content of the paste is in the range of 68 ≦ NV <70 (wt%), the peripheral speed ratio Vc / Vb is selected from the range of 18 ≦ Vc / Vb ≦ 30. This is because when the peripheral speed ratio Vc / Vb is low and Vc / Vb <18, the paste protrusions cannot be appropriately formed in the active material paste layer, and the surface becomes flat. On the other hand, in the case of Vc / Vb> 30, the unevenness generated in the formed active material paste layer becomes too large and “scaling” occurs.
Furthermore, when the solid content rate of the paste is in the range of 95 <NV ≦ 96 (wt%), the peripheral speed ratio Vc / Vb is selected from the range of 10 ≦ Vc / Vb ≦ 12. Since the solid fraction NV is high and the amount of the solvent contained is small, the granulated body is not easily deformed. Therefore, when the peripheral speed ratio Vc / Vb is high, that is, when Vc / Vb> 12, the active mass This is because the unevenness due to the paste protrusions formed in the material paste layer becomes too large, and the IV resistance of the battery at a low temperature (for example, −10 ° C.) increases. On the other hand, when Vc / Vb <10, the paste protrusions cannot be appropriately formed in the active material paste layer.

  The “solid content ratio” NV of the paste refers to the weight ratio of the solid content remaining after drying out of the components contained in the paste. The current collector foil is fed by a feed roll, and the feed speed of the current collector foil is equal to the peripheral speed Vc of the feed roll.

  And a wound secondary battery having a wound electrode body in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound through a strip-shaped separator, wherein the electrode body is impregnated with an electrolyte. In addition, at least one of the positive electrode plate and the negative electrode plate is a belt-shaped electrode plate having a strip-shaped active material layer extending in the longitudinal direction on a strip-shaped current collector foil extending in the longitudinal direction, The active material layer is preferably a wound secondary battery that is a convex-part distributed active material layer in which a large number of active material convexes extending in the longitudinal direction are distributed.

  In this secondary battery, in at least one of a positive electrode plate and a negative electrode plate that are wound to form an electrode body, the active material layer has a convex portion distribution active in which a large number of active material convex portions extending long in the longitudinal direction are distributed. It is a material layer. For this reason, even if this wound type secondary battery is repeatedly subjected to high rate charge / discharge, the active material convex portion of the convex distributed active material layer prevents the electrolyte held in the electrode body from being pushed out. It is possible to suppress the increase in battery resistance.

1 is a perspective view of a lithium ion secondary battery according to an embodiment. It is the longitudinal cross-sectional view which cut | disconnected the lithium ion secondary battery which concerns on embodiment by the plane in alignment with a battery horizontal direction and a battery vertical direction. It is an expanded view of an electrode body which concerns on embodiment and shows the state which mutually accumulated the positive electrode plate and the negative electrode plate through the separator. It is a partial expanded sectional view which cut | disconnected the negative electrode plate or the undried negative electrode plate in the width direction according to embodiment. It is explanatory drawing which shows a structure typically in connection with embodiment using apply | coating negative electrode paste to negative electrode current collector foil using a roll coating apparatus. It is a graph which shows the relationship between the peripheral speed ratio Vc / Vb and arithmetic mean roughness Ra about each example in case solid content ratio NV = 80,68,70,95,96wt%. It is a graph which shows the relationship between the peripheral speed ratio Vc / Vb and the resistance increase rate before and behind a high-rate pulse cycle test about each example in case solid content ratio NV = 80,68,70,95,96wt%.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. 1 and 2 show a wound lithium ion secondary battery (hereinafter also simply referred to as “battery”) 1 according to the present embodiment. FIG. 3 is a development view of the wound electrode body 20 constituting the battery 1. In the following description, the battery thickness direction BH, the battery lateral direction CH, and the battery vertical direction DH of the battery 1 are defined as the directions shown in FIGS. 1 and 2.
The battery 1 is a rectangular and sealed lithium ion secondary battery mounted on a vehicle such as a hybrid vehicle or an electric vehicle. The battery 1 includes a battery case 10, an electrode body 20 and a nonaqueous electrolyte solution 41 accommodated therein, a positive terminal 50 and a negative terminal 51 supported by the battery case 10, and the like.

  Among these, the battery case 10 has a rectangular parallelepiped shape and is made of metal (in this embodiment, aluminum). This battery case 10 includes a rectangular parallelepiped box-shaped case main body member 11 whose upper side is opened, and a rectangular plate-shaped case lid member 13 welded in a form to close the opening 11h of the case main body member 11. . The case lid member 13 is provided with a safety valve 14 that opens when the internal pressure of the battery case 10 reaches a predetermined pressure. The case lid member 13 is formed with a liquid injection hole 13 h that communicates the inside and outside of the battery case 10 and is hermetically sealed with a sealing member 15.

  Further, the case lid member 13 has a positive terminal 50 and a negative terminal 51 formed of an internal terminal member 53, an external terminal member 54, and a bolt 55, respectively, via an internal insulating member 57 and an external insulating member 58 made of resin. It is fixed. The positive terminal 50 is made of aluminum, and the negative terminal 51 is made of copper. In the battery case 10, the positive electrode terminal 50 is connected and connected to the positive electrode current collector 21 m of the positive electrode plate 21 in the electrode body 20 described later. Further, the negative electrode terminal 51 is connected to the negative electrode current collector 31 m of the negative electrode plate 31 in the electrode body 20 and is conductive.

  Next, the electrode body 20 will be described (see FIGS. 2 and 3). The electrode body 20 has a flat shape and is accommodated in the battery case 10. The electrode body 20 is a wound electrode body in which a belt-like positive electrode plate 21 and a belt-like negative electrode plate 31 are wound on each other via a pair of belt-like separators 40 and compressed into a flat shape.

  The positive electrode plate 21 has a positive electrode active material layer 23 provided in a band shape on a region extending in the longitudinal direction LH in a part of the width direction WH of both main surfaces of a positive electrode current collector foil 22 made of a band-shaped aluminum foil. Become. The positive electrode active material layer 23 includes positive electrode active material particles 24, a conductive material (conductive aid) 26, and a binder 27. In the present embodiment, particles made of lithium nickel cobalt manganese composite oxide are used as the positive electrode active material particles 24, acetylene black (AB) is used as the conductive material 26, and polyvinylidene fluoride (PVDF) is used as the binder 27. . In addition, the compounding ratio of the positive electrode active material particles 24, the conductive material 26, and the binder 27 is 93: 4: 3 in weight ratio.

  Further, in the positive electrode current collector foil 22, one end (upper in FIG. 3) in the width direction WH has no positive electrode active material layer 23 in its own thickness direction, and the positive electrode current collector foil 22 is exposed. It is a current collector 21m. The positive electrode terminal 50 described above is welded to the positive electrode current collector 21m.

  Next, the negative electrode plate 31 will be described. This negative electrode plate 31 is provided with a negative electrode active material layer 33 in a band shape on a region extending in the longitudinal direction LH in a part of the width direction WH of both main surfaces of a negative electrode current collector foil 32 made of a strip-shaped copper foil. It becomes. The negative electrode active material layer 33 includes negative electrode active material particles 34 and a thickener 35. In the present embodiment, scaly graphite particles are used as the negative electrode active material particles 34, and sodium polyacrylate is used as the thickener 35. In addition, the compounding ratio of the negative electrode active material particle 34 and the thickener 35 is 98: 2 by weight ratio. As will be described later, the negative electrode plate 31 has a negative electrode active material layer 33 in which a large number of active material protrusions 33p extending in the longitudinal direction LH are distributed on both surfaces (see FIGS. 3 and 4).

In addition, in the negative electrode current collector foil 32, one end (downward in FIG. 3) in the width direction WH has no negative electrode active material layer 33 in its own thickness direction, and the negative electrode current collector foil 32 is exposed. It is a current collector 31m. The negative electrode terminal 51 described above is welded to the negative electrode current collector 31m.
The separator 40 is a porous film made of resin and has a strip shape.

Next, the nonaqueous electrolytic solution 41 will be described. This non-aqueous electrolyte 41 is accommodated in the battery case 10, a part of the non-aqueous electrolyte 41 is impregnated in the electrode body 20, and the rest is accumulated at the bottom of the battery case 10 as an excess liquid. The electrolyte of this non-aqueous electrolyte 41 is lithium hexafluorophosphate (LiPF ₆ ), and its concentration is 1.0M. The nonaqueous solvent of the nonaqueous electrolytic solution 41 is a mixed organic solvent in which fluoroethylene carbonate (FEC) and 2,2,2-trifluoroethylmethyl carbonate are mixed at a volume ratio of 1: 1.

Next, a method for manufacturing the battery 1 will be described. First, the positive electrode plate 21 is formed. Specifically, positive electrode active material particles 24 made of LiNi _0.5 Mn _1.5 O ₄ which is a lithium nickel manganese composite oxide having a spinel structure are prepared. Then, the positive electrode active material particles 24, the conductive material 26 (acetylene black), and the binder 27 (polyvinylidene fluoride) are kneaded together with a solvent (NMP in this embodiment) to produce a positive electrode paste. . The mixing ratio of the positive electrode active material particles 24, the conductive material 26, and the binder 27 is 93: 4: 3 by weight as described above.

Thereafter, the positive electrode paste is applied to one main surface of the positive electrode current collector foil 22 made of a strip-shaped aluminum foil so that the coating weight of the solid content is 30 mg / cm ² and dried, and the positive electrode active material layer 23 is formed. Further, the positive electrode paste is applied to the other main surface of the positive electrode current collector foil 22 and dried to form the positive electrode active material layer 23. Then, this is pressed and the positive electrode plate 21 is obtained.

  Separately, the negative electrode plate 31 is formed. Specifically, first, negative electrode active material particles 34 made of flaky graphite with D50 = 10 μm are prepared. Then, a thickener 35 (sodium polyacrylate) is added to the negative electrode active material particles 34, and a solvent (in this embodiment, water) is added so that the solid fraction NV is 80 wt%. Using a granulator (Hiflex glal manufactured by Earth Technica Co., Ltd.), a negative electrode paste 37 composed of the negative electrode granulated body 36 is produced. The mixing ratio of the negative electrode active material particles 34 and the thickener 35 is 98: 2 by weight as described above.

Next, as shown in FIG. 5, this negative electrode paste 37 (negative electrode granulated body 36) is made of a negative electrode current collector foil made of a strip-like copper foil using a roll coater RI having three rolls ROA, ROB, ROC. The negative electrode paste layer 38 is formed so as to be applied to one main surface of 32 so that the coating weight of the solid content is 18 mg / cm ² . That is, the negative electrode plate 31 was formed such that the basis weight of the negative electrode active material layer 33 was 18 mg / cm ² .

  Specifically, the negative electrode paste 37 is charged into the paste supply unit PS, and the second paste layer 37r is formed on the supply roll ROA. The second paste layer 37r is supplied to the AB gap Gab between the supply roll ROA and the transfer roll ROB. Here, the peripheral speed Vb of the transfer roll ROB is made larger than the peripheral speed Va of the supply roll ROA (Va <Vb). For this reason, the first paste layer 37s made of the negative electrode paste 37 is formed on the transfer roll ROB (roll coating step). In this embodiment, the peripheral speed Va of the supply roll ROA is Va = 0.1 m / min, and the peripheral speed Vb of the transfer roll ROB is Vb = 0, which is twice the peripheral speed Va of the supply roll ROA. .2 m / min. That is, in this embodiment, the peripheral speed ratio Vb / Va between the supply roll ROA and the transfer roll ROB is Vb / Va = 2.

  Next, the first paste layer 37s on the transfer roll ROB is formed on one main surface on the transfer roll ROB side of the negative electrode current collector foil 32 passed through the BC gap Gbc between the transfer roll ROB and the feed roll ROC. The negative electrode paste layer 38 is transferred to 32 s (transfer process). Note that the peripheral speed Vc of the feed roll ROC that feeds the negative electrode current collector foil 32 is larger than the peripheral speed Vb of the transfer roll ROB (Vb <Vc). For this reason, the negative electrode paste 37 is transferred from the transfer roll ROB to one main surface 32 s of the negative electrode current collector foil 32. In this embodiment, the peripheral speed Vc of the feed roll ROC is Vc = 3 m / min, which is 15 times the peripheral speed Vb of the transfer roll ROB. That is, in this embodiment, the peripheral speed ratio Vc / Vb of the transfer roll ROB and the feed roll ROC is Vc / Vb = 15.

During this transfer, the negative electrode granule 36 forming the negative electrode paste 37 receives pressure in the BC gap Gbc and is elongated in the longitudinal direction LH of the negative electrode plate 31 (negative electrode current collector foil 32). Transferred to one main surface 32 s of the negative electrode current collector foil 32.
As will be described later, when the peripheral speed ratio Vc / Vb is small, the negative electrode granulated body 36 has a low degree even if it is elongated in the longitudinal direction LH. Can be deformed. For this reason, the surface of the negative electrode paste layer 38 can be kept flat.
However, when the peripheral speed ratio Vc / Vb is large (Vc / Vb = 15) as in the present embodiment, the individual negative electrode granulated bodies 36 are excessively stretched in the longitudinal direction LH, and the negative electrode current collector is As shown in FIG. 4, the negative electrode paste layer 38 on the foil 32 is a convex distribution paste layer in which irregularities are generated in the width direction WH and a large number of paste convex portions 38p extending in the longitudinal direction LH are distributed.

Next, the negative electrode paste layer 38 is dried by passing through a known drying furnace to form the negative electrode active material layer 33 (drying step). Due to the paste protrusions 38p described above, this negative electrode active material layer 33 also has a protrusion distribution in which a large number of active material protrusions 33p extending in the longitudinal direction LH are distributed as shown in FIGS. It is an active material layer.
Thereafter, the negative electrode paste 37 is applied and dried on the other main surface 32s of the negative electrode current collector foil 32 in the same manner as described above to form the negative electrode active material layer 33 in which a large number of active material convex portions 33p are distributed. Thus, the negative electrode plate 31 is obtained in which the negative electrode active material layers 33 in which a large number of active material protrusions 33p extending in the longitudinal direction LH are distributed are provided on both surfaces of the negative electrode current collector foil 32.

  The negative electrode active material layer 33 of the negative electrode plate 31 of the present embodiment has an arithmetic average roughness Ra (μm) (conforming to JIS B 0601: 2001) measured for a length of 20 mm in the width direction WH, Ra = 0.75 μm. Met. As described above, since the negative electrode active material layer 33 of the negative electrode plate 31 of the present embodiment is in a form in which a large number of active material convex portions 33p are distributed, when the arithmetic average roughness Ra or the like is measured in the width direction WH, It turns out that values, such as arithmetic mean roughness Ra, become a big value.

Next, the positive electrode plate 21 and the negative electrode plate 31 are overlapped with each other via a pair of separators 40 and wound using a winding core. Further, the electrode body 20 is formed by compressing it into a flat shape.
Separately, a case lid member 13, an internal terminal member 53, an external terminal member 54, a bolt 55, an internal insulating member 57 and an external insulating member 58 are prepared. Then, the positive terminal 50 and the negative terminal 51 including the internal terminal member 53, the external terminal member 54, and the bolt 55 are fixed to the case lid member 13 via the internal insulating member 57 and the external insulating member 58, respectively. Thereafter, the positive electrode terminal 50 and the negative electrode terminal 51 integrated with the case lid member 13 are welded to the positive electrode current collector 21m and the negative electrode current collector 31m of the electrode body 20, respectively.
Next, after housing the electrode body 20 in the case body member 11, the case cover member 13 is welded to the opening portion of the case body member 11 to form the battery case 10.

Separately, a non-aqueous electrolyte solution 41 is prepared. Specifically, LiPF ₆ is dissolved in a mixed organic solvent in which fluoroethylene carbonate and 2,2,2-trifluoroethyl methyl carbonate are mixed at a volume ratio of 1: 1 so as to have a concentration of 1.0M. Then, the nonaqueous electrolytic solution 41 is injected into the battery case 10 through the injection hole 13h, and the electrode body 20 is impregnated with the nonaqueous electrolytic solution 41. Thereafter, the liquid injection hole 13 h is temporarily sealed to obtain a battery 1.
Next, the battery 1 is initially charged, and thereafter the temporary sealing of the liquid injection hole 13h is released, and the liquid injection hole 13h is finally sealed under reduced pressure. Furthermore, various inspections are performed. Thus, the battery 1 is completed.

(Examples 1 to 24 and Comparative Examples 1 to 4)
Next, tests performed to verify the effects of the present invention and the results thereof will be described. As shown in Table 1 below, the positive electrode plate 21 used in the battery 1 and the negative electrode plate 31 having the negative electrode active material layer 33 in which many active material convex portions 33p are distributed, the separator 40, and the non-aqueous electrolyte 41 are used. An 18650 cylindrical battery having a diameter of 18 mm and a height of 650 mm was manufactured, and the IV resistance at 25 ° C., the IV resistance at −10 ° C., and the increase rate of the IV resistance before and after the high-rate pulse cycle test were investigated (Examples). 1).

In addition, for the negative electrode plate 31, a negative electrode paste 37 made of a granulated body in which the solid content of the negative electrode paste is 80 wt%, 70, 68, 95, 96 wt% is manufactured, and each roll ROA, ROB is manufactured. , ROC peripheral speeds Va, Vb, Vc were changed. In addition to using these negative electrode plates 31, the batteries of Examples 2 to 24 and Comparative Examples 1 to 4 in which the other conditions such as the positive electrode plate 21, the separator 40, and the non-aqueous electrolyte 41 were the same as the battery of Example 1 It manufactured and investigated IV resistance etc. (refer Table 1). In each of the batteries of the examples and comparative examples, the negative electrode plate 31 was formed so that the basis weight of the negative electrode active material layer 33 was the same, specifically, both were 18 mg / cm ^2. Was used.

The arithmetic average roughness (surface roughness) Ra is, as described above, the width of the negative electrode active material layer 33 of the negative electrode plate 31 used in each example and comparative example, in accordance with JIS B 0601: 2001. It is a value obtained by measuring over a length of 20 mm in the direction WH.
In addition, the 25 ° C. IV resistance is such that the completed 18650 cylindrical battery of each Example and Comparative Example is SOC = 60%, held in a 25 ° C. environment for 3 hours, and then discharged with a current of 10 C for 10 seconds. The battery voltage was measured and calculated. Similarly, after measuring the 25 ° C. IV resistance, the −10 ° C. IV resistance was determined by keeping the 18650 cylindrical battery of each Example and Comparative Example at SOC = 60% for 3 hours in an environment of −10 ° C. 10 C was discharged for 5 seconds and the battery voltage was measured and calculated.

  Further, the following was performed as a high-rate pulse cycle test. That is, in a constant temperature bath of 25 ° C., high rate charging is performed for 80 seconds with a charging current of 10 C for each of the 18650 cylindrical batteries of Examples and Comparative Examples in which the charged state SOC is 60%. Next, discharging is performed for 400 sec at a discharging current of 2C. With this as one cycle, charge and discharge were repeated over 3000 cycles, and the above-mentioned 25 ° C. IV resistance was measured before and after the test to obtain an increase rate of IV resistance.

  From the results of Table 1, the relationship between the peripheral speed ratio Vc / Vb and the arithmetic average roughness Ra (μm) is shown in the scatter diagram of FIG. Further, the relationship between the peripheral speed ratio Vc / Vb and the resistance increase rate by the high-rate pulse cycle test is shown in the scatter diagram of FIG. As shown in Table 1, although the resistance increase rate value was not obtained for Comparative Example 2, in FIG. 7, the resistance increase rate of Comparative Example 2 is plotted as 0%.

  The case where NV = 80 wt% indicated by “●” in FIGS. 6 and 7 (Examples 1 to 14 and Comparative Examples 1 and 2 in Table 1) will be examined. In the case of NV = 80 wt%, as shown in FIG. 6, it can be seen that the peripheral speed ratio Vc / Vb and the arithmetic average roughness Ra have a substantially proportional relationship. As the peripheral speed ratio Vc / Vb increases, the negative electrode granulated body 36 is elongated in the longitudinal direction LH and transferred to the main surface 32s of the negative electrode current collector foil 32. For this reason, it is thought that the unevenness | corrugation by forming the paste convex part 38p, ie, arithmetic mean roughness Ra, becomes larger. From the results of Examples 11 to 14, it can be seen that the arithmetic average roughness Ra of the negative electrode active material layer 33 is hardly affected by the difference in the peripheral speed ratio Vb / Va.

  Further, as shown in FIG. 7, it can be seen that the resistance increase rate decreases as the peripheral speed ratio Vc / Vb increases (and accordingly, the arithmetic average roughness Ra increases in proportion thereto). The reason is that the peripheral speed ratio Vc / Vb is increased and the arithmetic average roughness Ra is further increased. That is, when the active material convex portion 33p having a higher height is formed on the negative electrode active material layer 33 of the negative electrode plate 31, the negative electrode active material layer can be obtained even if the electrode body is rapidly expanded and contracted by performing a high-rate pulse cycle test. A large number of active material protrusions 33p formed on 33 suppress the extrusion of the non-aqueous electrolyte 41 to the outside of the electrode body (the outside in the axial direction of the electrode body: the outside in the width direction of the negative electrode plate 31). This is thought to be due to the suppression of the increase in

  In the case of NV = 80 wt%, in Example 6 (circumferential speed ratio Vc / Vb = 11), the resistance increase rate is 20%, and in Example 8 (circumferential speed ratio Vc / Vb = 10.3). The resistance increase rate is 23%, whereas in Comparative Example 1 (circumferential speed ratio Vc / Vb = 9), the resistance increase rate exceeds 25% and reaches 29%.

  Further, according to Table 1, in the case of Comparative Example 1 (circumferential speed ratio Vc / Vb = 9), the arithmetic average roughness Ra is as small as Ra = 0.46, and the negative electrode active material layer 33 cannot be uneven. It turns out that it becomes flat (refer to the remarks column in Table 1). Since the peripheral speed ratio Vc / Vb is small (Vc / Vb <10), in the negative electrode paste layer 38 on the negative electrode current collector foil 32, the individual negative electrode granules 36 contained therein extend in the longitudinal direction LH. However, since the negative electrode granulated body 36 can be deformed in accordance with stretching, it is considered that the surface of the negative electrode paste layer 38 as a whole can be kept flat and the active material convex portion 33p is not formed. . In Comparative Example 1, the rate of increase in resistance reaches 29%. Since the active material convex portion 33p is not formed on the negative electrode active material layer 33, it is considered that when the electrode body is rapidly expanded and contracted by performing a high-rate pulse cycle test, the nonaqueous electrolytic solution 41 is pushed out of the electrode body. It is done. Therefore, it can be seen that when the negative electrode paste 37 composed of the negative electrode granulated body 36 having a solid content ratio NV = 80 wt% is used, it is preferable that the peripheral speed ratio Vc / Vb ≧ 10.

  On the other hand, according to Table 1, in the case of Comparative Example 2 (circumferential speed ratio Vc / Vb = 31), the arithmetic average roughness Ra becomes too large as Ra = 1.55, and the negative electrode active material layer 33 has large unevenness. It can be seen that not only can be made, but also “scaling” (the fading of the current collector foil) occurs (see the remarks column in Table 1). Therefore, it can be seen that when the negative electrode paste 37 made of the negative electrode granule 36 having a solid content ratio NV = 80 wt% is used, it is preferable that the peripheral speed ratio Vc / Vb ≦ 30. From the above, it can be seen that it is preferable to select the peripheral speed ratio Vc / Vb from the range of 10 ≦ Vc / Vb ≦ 30.

  Next, the case of NV = 70 wt% (Examples 17 to 19 in Table 1) indicated by “■” in FIGS. When NV = 70 wt%, as shown in FIG. 6, the arithmetic average roughness Ra is Ra ≧ 0.0 in any case (Examples 17-19) in the range of the peripheral speed ratio Vc / Vb = 10-30. 50, and the active material convex portion 33p can be appropriately formed on the negative electrode active material layer 33, while no “scaling” occurs. Moreover, as shown in FIG. 7, it turns out that a resistance increase rate can be suppressed to 25% or less. It is considered that the formation of the active material convex portion 33p was able to suppress the non-aqueous electrolyte solution 41 from being pushed out of the electrode body even when the high rate pulse cycle test was performed.

  Further, the case of NV = 95 wt% (Examples 20 to 22 in Table 1) indicated by “▲” in FIGS. Also in the case of NV = 95 wt%, as shown in FIG. 6, the arithmetic average roughness Ra is Ra ≧ Ra in any case (Examples 20 to 22) in the range of the peripheral speed ratio Vc / Vb = 10 to 30. The active material convex portion 33p can be appropriately formed on the negative electrode active material layer 33, while no “scaling” occurs. Moreover, as shown in FIG. 7, it turns out that a resistance increase rate can be suppressed to 25% or less. It is considered that the formation of the active material convex portion 33p was able to suppress the non-aqueous electrolyte solution 41 from being pushed out of the electrode body even when the high rate pulse cycle test was performed.

  From the above, it is preferable to select the peripheral speed ratio Vc / Vb from the range of 10 ≦ Vc / Vb ≦ 30 when the solid content ratio NV is in the range of 70 ≦ NV ≦ 95.

Next, the case of NV = 68 wt% indicated by “♦” in FIGS. 6 and 7 (Comparative Example 3, Examples 15 and 16 in Table 1) will be examined. In the case of NV = 68 wt%, as shown in FIG. 6, there is a substantially proportional relationship between the peripheral speed ratio Vc / Vb and the arithmetic average roughness Ra, as in the case of NV = 80, 70, 95 wt%. It is the same.
However, the points in the case of NV = 68 wt% are plotted at positions slightly separated from the points in the case of NV = 80, 70, 95 wt% (downward in FIG. 6). That is, when the solid content rate of the negative electrode granulated body 36 is NV = 68 wt%, each point tends to be separated from the case of NV = 80, 70, 95 wt%. Therefore, the solid content rate NV = 68 wt% This is considered to be almost the lower limit of the solid content ratio NV of the negative electrode paste 37 (negative electrode granulated body 36) capable of forming many active material convex portions 33p on the active material layer 33.

Further, when NV = 68 wt%, the arithmetic average roughness Ra is lower when the peripheral speed ratio Vc / Vb is the same as when NV = 80, 70, 95 wt%. That is, in Comparative Example 3, even when the circumferential speed ratio Vc / Vb = 15, the arithmetic average roughness Ra = 0.48 is small, and the negative electrode active material layer 33 is not flat and flat (Table) See 1 Remarks column). Since the negative electrode granulated body 36 contains a large amount of solvent (low solid content) and the negative electrode granulated body 36 is easily deformed, the peripheral speed ratio Vc / Vb is increased to make the negative electrode granulated body 36 in the longitudinal direction LH. Even if it is greatly stretched, it is considered that the negative electrode granulated body 36 is deformed and the negative electrode paste layer 38 becomes flat. Further, in Comparative Example 3, the resistance increase rate reaches 32%. It can be seen that since the active material protrusions 33p could not be properly formed in the negative electrode active material layer 33, the resistance increase rate could not be suppressed to 25% or less. Since the active material convex portion 33p is not formed, it is considered that when the high-rate pulse cycle test is performed, the nonaqueous electrolyte solution 41 is pushed out of the electrode body, and the concentration distribution of the nonaqueous electrolyte solution 41 is generated in the electrode body. On the other hand, in Examples 15 and 16 (circumferential speed ratio Vc / Vb = 18, 30), the resistance increase rate is a favorable value of 17,10%. This is because in the range of Vc / Vb ≦ 30, the unevenness does not become excessive and “scaling” does not occur.
Therefore, it is preferable to select the peripheral speed ratio Vc / Vb from the range of 18 ≦ Vc / Vb ≦ 30 when the solid content ratio NV is in the range of 68 ≦ NV <70 wt%.

Next, a case where NV = 96 wt% indicated by “x” in FIGS. 6 and 7 (Examples 23 and 24 and Comparative Example 4 in Table 1) will be examined. As shown in FIG. 6, the fact that there is a substantially proportional relationship between the peripheral speed ratio Vc / Vb and the arithmetic average roughness Ra is the same as in the case of NV = 80, 70, 95, 68 wt%.
However, each point when NV = 96 wt% is plotted at a position (upward in FIG. 6) far away from each point when NV = 80, 70, 95, 68 wt%. That is, when the solid content ratio of the negative electrode granulated body 36 is NV = 96 wt%, each point tends to be greatly separated from the case of NV = 95 wt%. Therefore, the solid content ratio NV = 96 wt% is a negative electrode active material. This is considered to be almost the upper limit of the solid content ratio NV of the negative electrode paste 37 (negative electrode granulated body 36) capable of forming many active material convex portions 33p on the layer 33.

Further, when NV = 96 wt%, the arithmetic average roughness Ra is higher than when NV = 80, 70, 95, 68 wt%. That is, in Comparative Example 4, even when the circumferential speed ratio Vc / Vb = 15, the arithmetic average roughness Ra = 1.48 was large and no “scaling” occurred, but the negative electrode active material layer 33 has large unevenness (active material protrusion 33p) (see the remarks column in Table 1). Further, among the initial resistance characteristics, −10 ° C. IV was 72.2 mΩ, which was larger than the other examples. It is presumed that the weight per unit area of the negative electrode active material layer 33 was uneven due to the large unevenness. Thus, since the negative electrode granulated body 36 has a small amount of solvent (a large amount of solids) and the negative electrode granulated body 36 is not easily deformed, the negative electrode granulated body even if the peripheral speed ratio Vc / Vb is not so large. It is considered that the body 36 cannot be deformed according to the stretching, and large irregularities are formed in the negative electrode active material layer 33. On the other hand, in the case of Examples 23 and 24 (circumferential speed ratio Vc / Vb = 10, 12), the negative electrode active material layer 33 is formed with unevenness of an appropriate size, and the resistance increase rate is good at 15,13%. Value. In the case of Vc / Vb <10, the negative electrode active material layer 33 is difficult to be uneven and is flat, which is not preferable.
Therefore, it is preferable to select the peripheral speed ratio Vc / Vb from the range of 10 ≦ Vc / Vb ≦ 12 when the solid content ratio NV is in the range of 95 <NV ≦ 96 wt%.

As described above, in the method of manufacturing the electrode plate (negative electrode plate 31) for the wound secondary battery described above, the peripheral speed Vc of the feed roll ROC that feeds the negative electrode current collector foil 32 is transferred to the transfer roll in the transfer step. Further, the negative granule 36 (negative electrode paste 37) supplied to the BC gap Gbc is transferred to the negative electrode current collector foil 32 while extending in the longitudinal direction LH, which is faster than the peripheral speed Vb of ROB (Vc> Vb). Thus, the negative electrode paste layer 38 in which a large number of paste protrusions 38p extending in the longitudinal direction LH are distributed is formed. Further, this is dried in a drying step to form the negative electrode active material layer 33 in which a large number of active material convex portions 33p extending in the longitudinal direction LH are distributed.
The strip-shaped negative electrode plate 31 having the negative electrode active material layer 33 in which the active material convex portions 33p thus produced are distributed is wound together with the positive electrode plate 21 and the separator 40 to form the wound electrode body 20. Furthermore, the battery 1 is housed in the battery case 10 and impregnated with the non-aqueous electrolyte 41 to form the battery 1. Then, in the battery 1, even if the high-rate charge / discharge such as the high-rate pulse cycle test described above is repeatedly performed, the negative electrode active material layer 33 of the negative electrode plate 31 is provided with the active material convex portion 33p extending long in the longitudinal direction LH. Therefore, the nonaqueous electrolyte solution 41 held in the electrode body 20 is suppressed from being pushed out and the increase in battery resistance can be suppressed.

  Furthermore, in the roll coating process, the negative electrode paste 37 is supplied to the AB gap Gab between the supply roll ROA and the transfer roll ROB, and the first paste layer 37s is formed on the transfer roll ROB. The adjustment range of the thickness (coating weight) can be widened, and the thickness of the negative electrode paste layer 38 can be adjusted with high accuracy.

  Further, as described above, when the solid content ratio NV of the negative electrode paste 37 (negative electrode granulated body 36) is 70 ≦ NV ≦ 95 wt%, the peripheral speed ratio Vc / Vb is within the range of 10 ≦ Vc / Vb ≦ 30. When the solid content ratio NV is 68 ≦ NV <70 wt%, the peripheral speed ratio Vc / Vb is selected from the range of 18 ≦ Vc / Vb ≦ 30, and the solid content ratio NV is 95 <NV ≦ 96 wt%. In this case, the peripheral speed ratio Vc / Vb is selected from the range of 10 ≦ Vc / Vb ≦ 12. Thus, by defining the range of the peripheral speed ratio Vc / Vb to be selected according to the solid content ratio NV of the negative electrode paste 37 (negative electrode granulated body 36), a large number of paste convex portions 38p are distributed in the transfer process. In addition, the negative electrode paste layer 38 and the negative electrode active material layer 33 in which a large number of active material protrusions 33p are distributed in the drying step can be appropriately formed.

  Further, in the battery 1 described above, in the negative electrode plate 31 that is wound to form the electrode body 20, the negative electrode active material layer 33 has a convex distribution active material layer in which a large number of active material convex portions 33p extending long in the longitudinal direction LH are distributed. It is said. For this reason, even if this wound battery 1 is repeatedly charged and discharged at a high rate, the non-aqueous electrolyte solution 41 in which the active material convex portion 33p of the negative electrode active material layer 33 is held in the electrode body 20 is external. It is possible to suppress the battery resistance from being increased by suppressing the battery resistance.

In the above, the present invention has been described with reference to the embodiments and the like. However, the present invention is not limited to the above-described embodiments and the like, and it is needless to say that the present invention can be appropriately modified and applied without departing from the gist thereof. .
For example, in the battery 1 and each example described above, the active material convex portion 33p is provided on the negative electrode active material layer 33 of the negative electrode plate 31, but the active material convex portion is provided on the positive electrode active material layer 23 of the positive electrode plate 21. You may do it.

1 Lithium ion secondary battery (battery)
20 Electrode body 21 Positive electrode plate (positive electrode)
31 Negative electrode plate (negative electrode)
32 Negative electrode current collector foil 32s Main surface 33 (of negative electrode current collector foil) Negative electrode active material layer (active material layer, convex distribution active material layer)
33p Active material convex part 34 Negative electrode active material particle 35 Thickener 36 Negative electrode granulated body 37 Negative electrode paste 37r Second paste layer 37s First paste layer 38 Negative electrode paste layer (convex part distribution paste layer, active material paste layer)
38p paste convex RI roll coater (coating equipment)
PS Paste supply part ROA Supply roll Va (supply roll) peripheral speed ROB Transfer roll Vb (transfer roll) peripheral speed ROC Feed roll Vc (feed roll) peripheral speed Gab (between supply roll and transfer roll) AB Gap (second gap)
Gbc (between transfer roll and feed roll) BC gap (first gap)
40 Separator 41 Non-aqueous electrolyte (electrolyte)
WH Width direction of positive electrode plate and negative electrode plate LH Longitudinal direction of positive electrode plate and negative electrode plate

Claims (3)

On the strip-shaped current collector foil extending in the longitudinal direction, a paste having a granulated body containing at least active material particles, a thickener, and a solvent is applied and dried to form the strip-shaped active material layer extending in the longitudinal direction. A method for producing an electrode plate for a wound secondary battery for producing a strip-shaped electrode plate having:
A roll application step of applying the paste on a transfer roll to form a first paste layer;
The first paste layer applied on the transfer roll in the roll coating step is transferred onto the current collector foil passed through the first gap between the feed roll for feeding the current collector foil and the transfer roll. A transfer step of forming an active material paste layer;
Drying the active material paste layer to form the active material layer, and
The transfer step is
The peripheral speed Vc of the feed roll that feeds the current collector foil is made faster (Vc> Vb) than the peripheral speed Vb of the transfer roll, and the granule supplied to the first gap is extended in the longitudinal direction. Transfer to the current collector foil,
As the active material paste layer, forming a convex distribution paste layer in which a large number of paste convexes extending in the longitudinal direction are distributed,
The drying step
An electrode plate for a wound secondary battery, wherein the convex distribution paste layer is dried to form a convex distribution active material layer in which a large number of active material projections extending in the longitudinal direction are distributed as the active material layer. Manufacturing method. It is a manufacturing method of the electrode plate for wound type rechargeable batteries according to claim 1,
The roll coating step
A method of manufacturing an electrode plate for a wound secondary battery, wherein the paste is supplied to a second gap between a supply roll and the transfer roll to form the first paste layer on the transfer roll. A method for manufacturing an electrode plate for a wound secondary battery according to claim 1 or 2,
The solids content NV of the paste is 68 to 96 (wt%),
The transfer step includes
When the solid content ratio NV of the paste is 70 ≦ NV ≦ 95 (wt%), the peripheral speed ratio Vc / Vb between the peripheral speed Vc of the feed roll and the peripheral speed Vb of the transfer roll is 10 Select from the range of ≦ Vc / Vb ≦ 30,
When the solid content NV of the paste is 68 ≦ NV <70 (wt%), the peripheral speed ratio Vc / Vb is selected from the range of 18 ≦ Vc / Vb ≦ 30,
When the solid content ratio NV of the paste is 95 <NV ≦ 96 (wt%), the peripheral speed ratio Vc / Vb is selected from the range of 10 ≦ Vc / Vb ≦ 12. Manufacturing method of battery electrode plate.

Images