JP2009266660A - Manufacturing method of electrode plate for lithium ion secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the manufacturing method of an electrode plate for a lithium ion secondary battery capable of sufficiently ensuring adhesion between metal foil and a binder which is homogeneous within an active material layer by a necessary minimum amount of binder. <P>SOLUTION: Slurry containing an active material is applied to metal foil 1 with a coating device 2, a shield plate 5 is set to the surface side of the metal foil 1, preheating is conducted by sending warm air from a warm air device 4 on the back side of the metal foil, and then slurry is dried by sending warm air from both warm air devices 4 of the surface side and the back side of the slurry coated surface to manufacture the electrode plate for the lithium ion secondary battery. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of manufacturing an electrode plate used for a lithium ion secondary battery.

  In recent years, electronic devices and communication devices are rapidly becoming smaller and lighter, and secondary batteries used as driving power sources are also required to be smaller and lighter. In particular, lithium ion secondary batteries are mainly used for small portable electronic devices such as mobile phones and game machines. Recently, there is an increasing demand for a lithium ion secondary battery that can be used for a long time with a smaller volume.

  The lithium ion secondary battery has a configuration in which two electrode plates of a positive electrode and a negative electrode, each having an active material layer formed on a metal foil, are opposed to each other via a separator. The electrode plate is manufactured with conditions such as thickness and dimensions determined according to the specifications (storage capacity, dimensions, etc.) of the lithium ion battery.

  The active material layer formed on the metal foil is manufactured by applying a slurry made of a mixture of active material particles having an average particle diameter of several μm to several tens of μm, a binder, and a solvent to the metal foil, and drying. The binder has a function of binding the active materials and binding the active material and the metal foil. A conventional method of manufacturing an electrode plate is disclosed in Patent Document 1.

  A method for manufacturing a conventional electrode plate for a lithium ion secondary battery will be described with reference to the drawings. FIG. 8 is an explanatory view of a manufacturing process of a conventional electrode plate for a lithium ion secondary battery. The metal foil 1 is sent out from the metal foil unwinding unit 11, the slurry is applied to the upper surface from the coating device 2, dried through the drying furnace 3, and wound up by the metal foil winding unit 21. Here, the drying furnace 3 includes a first drying zone 13, a second drying zone 23, and a third drying zone 33. In the first drying zone 13, the warm air device 4 performs preheating by sending warm air from the back side of the slurry application surface of the metal foil 1. In the second drying zone 23 and the third drying zone 33, the hot air device 4 is arranged on both the front surface side and the back surface side of the slurry application surface to dry the slurry.

  In the conventional method for manufacturing an electrode plate for a lithium ion secondary battery, the hot air from the back side of the slurry application surface of the metal foil 1 in the first drying zone 13 is dispersed in the first drying zone 13 to apply the slurry. Since the binder is unevenly distributed on the surface due to the surface of the slurry being dried, the distribution of the binder in the active material layer becomes non-uniform, and the binding force between the metal foil and the active material is reduced, which makes it easy to peel off. there were.

  An anode electrode (negative electrode) manufactured using a binder containing fluorine by a conventional manufacturing method was subjected to EPMA analysis in the vicinity of the interface of the metal foil to measure the fluorine count, and the peel strength of the metal foil was measured. The results are shown in the figure. FIG. 9 is a graph of the fluorine count number and peel strength of the anode electrode according to the conventional manufacturing method.

  From FIG. 9, the peel strength and the fluorine count number increase as the peel strength increases. The fluorine count number represents the distribution state of the binder and indicates that the binder is uniformly distributed. That is, by homogenizing the binder in the active material layer formed on the metal foil, the peel strength can be increased, and the binding between the active material and the metal foil can be made sufficient.

  From this measurement result, in order to make the binder in the active material layer homogeneous, if the drying time is short with respect to the step of drying the slurry, the binder between the active materials in the vicinity of the metal foil may be reduced. Although it is conceivable to lengthen the drying furnace, there is a problem that the drying furnace is lengthened and the equipment is enlarged. Moreover, although it is possible to reduce the application | coating speed | rate of a slurry, there existed a problem that manufacturing efficiency worsened.

  Therefore, it is conceivable to increase the amount of the binder, but the amount of the active material is relatively decreased, and the storage capacity is decreased. In order to satisfy the demand for a small-sized secondary battery that can be used for a long time, the storage capacity cannot be reduced. Therefore, the amount of the binder cannot be increased, and the binder must be produced in the minimum necessary amount.

JP 2006-107780 A

  The present invention solves the above problems in the production of an electrode plate for a lithium ion secondary battery. The binder in the active material layer is homogeneous with the minimum amount of binder, and the metal foil and binder It is to propose a method for manufacturing an electrode plate for a lithium ion secondary battery that can sufficiently secure binding.

  The present invention applies a slurry containing an active material to a metal foil, sends warm air from the back surface side of the slurry coating surface of the metal foil and preheats, and then both the surface side and the back surface side of the slurry coating surface. A method for producing an electrode plate for a lithium ion secondary battery by sending hot air from a slurry and installing a shielding plate at a distance on the surface side of the metal foil in the preliminary heating step This is a method for producing an electrode plate for a lithium ion secondary battery.

  The present invention is the method for producing an electrode plate for a lithium ion secondary battery, wherein the distance is 10 to 40 mm.

  The present invention is the above-described method for manufacturing an electrode plate for a lithium ion secondary battery, wherein the width of the shielding plate is equal to or smaller than the width of the metal foil.

  The present invention is the above-described method for producing an electrode plate for a lithium ion secondary battery, wherein the difference in width between the metal foil and the shielding plate is 0 to 30 mm.

  According to the present invention, in the electrode plate for a lithium ion secondary battery manufactured by applying a slurry mixed with an active material, a binder and a solvent to a metal foil, the binder in the active material layer is added with a minimum amount of binder. Homogeneous, and sufficient binding strength between the metal foil and the active material can be secured.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view of a production process of an electrode plate for a lithium ion secondary battery of the present invention. FIG. 2 is an explanatory view of the first drying zone in the production process of the electrode plate for a lithium ion secondary battery of the present invention as seen from the side.

  In FIG. 1, the metal foil 1 is sent out from the metal foil unwinding portion 11 and is applied from the coating device 2 to the upper surface in the same manner as in the explanatory view of the manufacturing process of the conventional electrode plate for a lithium ion secondary battery shown in FIG. The slurry is applied to the metal foil, dried through the drying furnace 3, and wound on the metal foil winding unit 21. Here, the drying furnace 3 includes a first drying zone 13, a second drying zone 23, and a third drying zone 33. In the first drying zone 13, the warm air device 4 performs preheating by sending warm air from the back side of the slurry application surface of the metal foil 1. Here, in the first drying zone 13, the shielding plate 5 is disposed on the surface side of the metal foil 1. The second drying zone 23 and the third drying zone 33 are the same as the conventional method because the hot air device 4 is disposed on both the front side and the back side of the metal foil 1 to dry the slurry.

  According to the method for producing an electrode plate for a lithium ion secondary battery of the present invention, as shown in FIG. 2, the hot air 14 sent from the hot air device 4 to the metal foil back surface in the first drying zone 13 is a metal The hot air 24 extruded from the foil 1 in the lateral direction hits the shielding plate 5 to prevent drying of the slurry surface. Thereby, drying of the slurry surface can be reduced.

  The distance between the shielding plate 5 and the metal foil 1 is preferably 10 to 40 mm, and the width of the shielding plate 5 is desirably the same or narrower than the width of the metal foil 1. The width difference of 5 is preferably 0 to 30 mm.

  In FIG. 1, the drying furnace 3 is shown by three zones, ie, a first drying zone 13, a second drying zone 23, and a third drying zone 33, but the first is provided with a hot air device from the back side of the metal foil. Although it is necessary to provide at least one drying zone, the drying zone in which the hot air devices 4 are provided on both the front surface side and the back surface side of the metal foil 1 is not limited to FIG. good.

  The example which manufactured the anode electrode by the manufacturing method of the electrode plate for lithium ion secondary batteries of this invention is demonstrated.

  As the metal foil, an electrolytic copper foil (manufactured by Furukawa Electric) having a width of 400 mm and a thickness of 8 μm was used. The raw material of the slurry uses, as an active material, commercially available artificial graphite powder (manufactured by Timical, Italy, average particle size 30 μm), 173.33 kg, binder is commercially available PVDF # 9300 (made by Kureha), 5.39 kg, as a solvent Used N-methyl-2-pyrrolidone (hereinafter referred to as NMP) 179.73 kg and oxalic acid 0.11 kg. These raw materials were mixed in a mixer SR-300 manufactured by Paulec Co., Ltd. to prepare a slurry. The viscosity of the slurry was 12000 cp at 12 rpm.

  The application and drying of the slurry is performed by connecting the first drying zone with the hot air device on the back surface of the metal foil and the second and third drying zones with the hot air device on both surfaces of the metal foil, A coating machine made of Hiranotechseed provided with an opening to be passed was used.

  In each drying chamber, the first drying zone has a set temperature of 130 ° C. and a wind speed of 5 (m / sec) perpendicular to the copper foil surface, and the second drying zone has a set temperature of 120 ° C. and a wind speed of 5 (m / sec). sec), the third drying zone was similarly set to a wind speed of 17 (m / sec) at a set temperature of 130 ° C.

  As an example of the present invention, in the first drying zone, an anode electrode was manufactured by installing a shielding plate having a width of 400 mm, which is the same as the copper foil, at a distance of 10 mm from the copper foil. As a comparative example, an anode electrode was manufactured without installing a shielding plate.

Moreover, the application | coating speed | rate (feeding speed of copper foil) shall be 1.0 m / min for the application | coating conditions of a slurry. It applied so that the density of the active material containing the binder after drying might be 9.5 mg / cm < ³ >.

  First, since the temperature of each drying chamber is the temperature of the warm air sent into the drying chamber, in order to confirm the temperature actually applied to the copper foil, a thermocouple is attached to the copper foil, and the copper foil is moved 10 to 20 cm at a time. The temperature applied to the copper foil was measured, and the temperature distribution in both cases with and without the shielding plate was confirmed.

  FIG. 3 is a graph showing the measurement result of the temperature distribution in the drying furnace of the present invention. The temperature when the shielding plate is installed is shown as an example, and the temperature distribution when there is no shielding plate is shown as a comparative example. There was hardly any difference in temperature distribution in the drying furnace depending on whether or not a shielding plate was installed in the first drying zone.

  The peel strength was measured for evaluating the binding force between the copper foil and the active material. FIG. 4 is an explanatory diagram of a peel strength measuring method. FIG. 4A is a side view of a configuration in which a sample is fixed. The manufactured anode electrode plate was cut into a strip shape having a width of 12 mm to prepare a sample 41, and the sample was fixed to the sample fixing plate 43 with double-sided adhesive tape 42. FIG. 4B is a side view of the active material layer peeled off. The lower end of the sample 41 was pulled up vertically in the direction of the arrow, and the load when the active material layer 40 was peeled from the sample 41 was measured with a tensile tester.

  In measuring the peel strength, in order to confirm the difference depending on the position of the manufactured anode electrode plate, measurement samples were taken from six locations and the peel strength was measured. FIG. 5 is an explanatory diagram of a position where a measurement sample is collected. Slurry coating on the copper foil is performed under conditions of a width of 380 mm and a copper foil feeding direction of 300 mm, and a sample collected from the initial coating position at the center of the slurry coating part is A, from the middle position. The sample collected was designated as B, and the sample collected from the end of application as C. At the end of the slurry application part, D is a sample collected from the initial application position, E is a sample collected from the middle position, and F is a sample collected from the final application position. The results are shown in Table 1.

  From Table 1, the peel strength was greatly improved as compared with the Examples and Comparative Examples. In particular, in the sample E collected from the position of the intermediate part at the end of the slurry application part, the peel strength was doubled.

  Next, the peel strength was measured by changing the distance between the shielding plate and the copper foil to 10 to 60 mm under the same 400 mm width as the copper foil and the shielding plate. As the sample, E collected from the position of the intermediate portion at the end of the slurry application portion described in FIG. 5 was used.

  FIG. 6 is a graph of the distance between the shielding plate and the copper foil of the present invention and the peel strength. From FIG. 6, the peel strength was stable and 40 (mN) was obtained at a distance of 10 to 40 mm between the shielding plate and the copper foil.

  The distance between the shielding plate and the copper foil is 10 mm, but the copper foil is moved up and down by about 5 mm with warm air from the lower surface, so that the portion where the slurry is applied comes into contact with the shielding plate. To avoid it, 10 mm is substantially the lower limit.

  Moreover, in the conditions of the example of the present invention, the distance between the shield plate and the copper foil was 20 mm, and the peel strength was measured by changing the size of the shield plate from 420 mm to 340 mm with respect to the copper foil width of 400 mm. As the sample, E collected from the position of the intermediate portion at the end of the slurry application portion described in FIG. 5 was used. The results are shown in FIG.

  FIG. 7 is a graph of the difference between the copper foil width and the shielding plate width and the peel strength of the present invention. In FIG. 7, the horizontal axis represents the difference between the copper foil width and the shielding plate width. As shown in FIG. 7, when the difference between the shielding plate width and the shielding plate having a copper foil width of 400 mm was 0 to 30 mm, the peel strength was stable and 40 mN was obtained. When the shielding plate width was wider than the copper foil width, the peel strength was low.

  In addition, although the effect was described about the anode electrode in the present Example, the same effect was acquired also about the cathode electrode (positive electrode).

Explanatory drawing of the manufacturing process of the electrode plate for lithium ion secondary batteries of this invention. Explanatory drawing which looked at the 1st drying zone of the manufacturing process of the electrode plate for lithium ion secondary batteries of this invention from the side. The graph of the measurement result of the temperature distribution in the drying furnace of this invention. Explanatory drawing of the peeling strength measuring method. Fig.4 (a) is a side view of the form which fixed the sample. FIG. 4B is a side view showing a state in which the active material layer is peeled off. Explanatory drawing of the position which extract | collected the measurement sample. The graph of the distance between the shielding board of this invention, copper foil, and peeling strength. The graph of the difference of the copper foil width | variety of this invention, a shielding board width, and peeling strength. Explanatory drawing of the manufacturing process of the conventional electrode plate for lithium ion secondary batteries. The graph of the fluorine count number and peeling strength of the anode electrode by the conventional manufacturing method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal foil 2 Coating apparatus 3 Drying furnace 4 Hot air apparatus 5 Shielding board 11 Metal foil unwinding part 13 1st drying zone 14, 24 Hot air 21 Metal foil winding part 23 2nd drying zone 33 3rd drying zone 40 Material layer 42 Double-sided adhesive tape 43 Sample fixing plate 41, A, B, C, D, E, F Sample

Claims (4)

  After applying the slurry containing the active material to the metal foil, pre-heating hot air from the back side of the slurry application surface of the metal foil, and then supplying hot air from both the front and back sides of the slurry application surface A method for producing an electrode plate for a lithium ion secondary battery by drying the feed slurry, wherein a shielding plate is installed at a distance on the surface side of the metal foil in the preliminary heating step. A method for manufacturing an electrode plate for a lithium ion secondary battery.   2. The method for manufacturing an electrode plate for a lithium ion secondary battery according to claim 1, wherein the distance is 10 to 40 mm.   3. The method of manufacturing an electrode plate for a lithium ion secondary battery according to claim 1, wherein a width of the shielding plate is equal to or smaller than a width of the metal foil. .   The method for manufacturing an electrode plate for a lithium ion secondary battery according to any one of claims 1 to 3, wherein a difference in width between the metal foil and the shielding plate is 0 to 30 mm.

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