JP2009004303A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery which is strong against an external impact such as falling and vibration and is suppressed in variations in thickness and impedance. <P>SOLUTION: The nonaqueous electrolyte secondary battery has a battery element in which a positive electrode plate and a negative electrode plate are laminated and wound around through a separator housed in an outer package. The battery element is wound, fixed, and covered by a tape 1 including a thermosetting resin layer 1a on a substrate layer 1b, and then, the thermosetting resin is cured. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery excellent in impact resistance.

  In recent years, non-aqueous electrolyte secondary batteries such as lithium ion batteries have been used as power sources for small electronic devices such as mobile phones and personal computers. Recently, as the use of non-aqueous electrolyte secondary batteries has expanded to power assist bicycles, power sources for electric tools, etc., non-aqueous electrolyte secondary batteries that are resistant to shock, vibration, and the like have been desired.

  A non-aqueous electrolyte secondary battery generally includes positive electrode active materials such as lithium cobaltate and spinel type lithium manganate, each of which is used alone or in combination, and formed into a positive electrode current collector together with a binder. In general, a negative electrode active material such as a carbon material and a negative electrode plate formed on a negative electrode current collector together with a binder are laminated via a separator, and a battery element having a wound structure (jelly roll structure) is bonded with an adhesive tape. The non-aqueous electrolyte secondary battery was manufactured by pouring, sealing in a battery can or a laminate film, and injecting a non-aqueous electrolyte.

  Further, Patent Document 1 proposes a battery in which an adhesive-unapplied part is formed on the peripheral part of an adhesive tape so that the outermost electrode is not cracked even when the battery is dropped. In addition, Patent Document 2 proposes a battery using a heat-resistant adhesive tape. Further, Patent Document 3 proposes a battery in which an insulating adhesive tape whose adhesive is thermosetting is attached to the end of the positive electrode plate, and the insulating adhesive tape is wound and fixed to the outermost negative electrode plate.

JP 2005-243336 A JP 2007-73317 A JP 2003-168470 A

  In the conventional non-aqueous electrolyte secondary battery, the battery element is wound and then wound with an adhesive tape to prevent the battery element from being unwound. In the case where a more severe drop test or vibration test is repeatedly performed on a conventional non-aqueous electrolyte secondary battery in which such a battery element is wound with an adhesive tape and stored in a battery can, the positive electrode plate and the negative electrode of the battery element There are cases where the plate and the separator are displaced. In extreme cases, an electrical failure such as an internal short circuit may occur.

  An object of the present invention is to improve impact resistance such as dropping or vibration with respect to a portable device or the like in which a nonaqueous electrolyte secondary battery is incorporated, and to reduce variations in thickness and impedance of the nonaqueous electrolyte secondary battery. The object is to provide a highly reliable non-aqueous electrolyte secondary battery.

  The present invention uses a tape including a thermosetting resin layer as a battery element winding tape composed of a positive electrode plate, a negative electrode plate, and a jelly roll wound with a separator, and cures the thermosetting resin within the manufacturing process. The jelly also serves as an inner pack in which the tape itself becomes a plastic case, has a higher external impact strength than the conventional one, and is derived from the decomposition of the electrolyte that occurs inside the battery during initial charging, etc. As a result of finding that by suppressing roll distortion, variation in cell thickness is suppressed compared to the conventional case, and further, the increase in impedance is suppressed because the distance between electrodes is not increased, thereby suppressing variation in impedance. It is.

  The nonaqueous electrolyte secondary battery of the present invention is a nonaqueous electrolyte secondary battery in which a battery element obtained by laminating and winding a positive electrode plate and a negative electrode plate via a separator is housed in an exterior body. It is characterized in that it is stopped and covered with a tape containing a curable resin layer, and then a thermosetting resin is cured.

  Further, the tape may have a two-layer structure of an adhesive layer made of a thermosetting resin layer and a base material layer, or the tape may be composed of a base material layer, a thermosetting resin layer, and an adhesive layer. It may have a layer structure, the tape may have a two-layer structure of a base material layer made of a thermosetting resin layer and an adhesive layer, or the tape may be made of a thermosetting resin layer. It may have a two-layer structure of a base material layer and an adhesive layer made of a thermosetting resin layer, or the tape may be made of a thermosetting resin layer. Furthermore, it is preferable that the thermosetting resin layer contains at least one of urea resin, phenol resin, melamine resin, epoxy resin, or silicon resin.

  According to the present invention, a tape including a thermosetting resin layer is used as a jelly roll squeezing tape, covering a battery element, and enhancing the impact resistance of the nonaqueous electrolyte secondary battery by curing in the process, Variations in thickness and impedance can be suppressed.

  Next, embodiments of the present invention will be described with reference to the drawings.

  First, a battery element tape for use in the present invention will be described. FIG. 1 is a side view of a tape used in the nonaqueous electrolyte secondary battery according to the first embodiment of the present invention. As shown in FIG. 1, a wrapping tape for holding a wound structure (jelly roll structure) of a battery element is composed of a thermosetting resin layer 1a and a base material layer 1b. For the substrate layer 1b, polyphenylene sulfide (hereinafter referred to as PPS), polyimide, polypropylene (PP), or the like can be used. For the thermosetting resin layer 1a, urea resin, phenol resin, melamine resin, epoxy resin, silicon resin and the like can be used. In the tape used for the nonaqueous electrolyte secondary battery of the first embodiment of the present invention, the thermosetting resin layer 1a can be formed on the base material layer 1b by coating or the like. The thermosetting resin layer 1a holds the battery element after winding as an adhesive layer of the tape.

  Next, the tape used for the nonaqueous electrolyte secondary battery according to the second embodiment of the present invention will be described. A tape for scratching has a three-layer structure of a base material layer, a thermosetting resin layer, and an adhesive layer. As in the first embodiment, PPS, polyimide, PP and urea resin, phenol resin, melamine resin, epoxy resin, and silicon resin can be used for the base material layer and the thermosetting resin layer, respectively. Further, an acrylic or thermosetting rubber adhesive can be used as the adhesive layer on the thermosetting resin layer. In the second embodiment, even when a thermosetting resin layer having a weak adhesive force is used, it can be scratched.

  Next, the tape used for the nonaqueous electrolyte secondary battery according to the third embodiment of the present invention will be described. The tape for squeezing has a two-layer structure of a base material layer made of a thermosetting resin layer and an adhesive layer. A urea resin, a phenol resin, a melamine resin, an epoxy resin, a silicon resin, or the like can be used for the base material layer, and an acrylic or thermosetting rubber adhesive can be used for the adhesive layer. In the third embodiment, when the thermosetting resin layer has a tensile strength as a tape, it can be used as a base material layer, and by forming an adhesive layer on the thermosetting resin layer, can do. In the third embodiment, since the thermosetting resin layer becomes the base material layer, the thermosetting resin layer can be made thicker and stopped.

  Next, the tape used for the nonaqueous electrolyte secondary battery according to the fourth embodiment of the present invention will be described. The tape for scratching has a two-layer structure of a base material layer made of a thermosetting resin layer and an adhesive layer made of a thermosetting resin layer. For the base material layer and the adhesive layer, urea resin, phenol resin, melamine resin, epoxy resin, silicon resin and the like can be used, respectively. In the fourth embodiment, by forming a two-layer structure using a thermosetting resin layer having a tensile strength as a tape as a base material layer and an adhesive thermosetting resin layer as an adhesive layer. It can be set as a whip-stopping tape, and since the base material layer and the adhesive layer are made of a thermosetting resin layer, the thermosetting resin layer can be further thickened to be whispered.

  Next, the tape used for the nonaqueous electrolyte secondary battery according to the fifth embodiment of the present invention will be described. The tape for scratching consists of a thermosetting resin layer. For the thermosetting resin layer, urea resin, phenol resin, melamine resin, epoxy resin, silicon resin and the like can be used. In the fourth embodiment, it is possible to obtain a tape having adhesiveness only by the thermosetting resin layer, and it is possible to stop by only the thermosetting resin layer. For example, as a tape made of an epoxy resin, there are SUPER-EPOXY TAPE 1520 manufactured by Sumitomo 3M Co., and tape-shaped adhesive S-1255-02 manufactured by Tyco Electronics Raychem Co.

Next, the nonaqueous electrolyte secondary battery of the present invention will be described. The positive electrode plate, the negative electrode plate, and the separator used in the nonaqueous electrolyte secondary battery of the present invention can be the same as conventional ones. That is, the positive electrode plate is made of an aluminum foil by mixing a positive electrode active material made of LiCoO ₂ or the like, a conductive aid, a binder made of PVdF or the like and dispersing it in NMP (N-methyl-2-pyrrolidone) to form a slurry. The negative electrode plate is produced by applying and drying on both surfaces of the positive electrode current collector, and the negative electrode plate is made of carbon or the like that can insert and desorb (intercalate / deintercalate) Li ions between layers, A conductive auxiliary agent and a binder mixed together and dispersed in NMP to form a slurry were applied to both surfaces of a negative electrode current collector made of copper foil and dried. An electrode terminal is connected to each of the positive electrode plate and the negative electrode plate, stacked via a separator having ion permeability, and wound to produce a battery element.

  FIG. 2 is a front view showing an intermediate step of the nonaqueous electrolyte secondary battery of the present invention. The electrode plate terminal portion 5 of the battery element 2 in which the electrode terminal 4 is drawn out and wound as described above is wound with the tape 1. Here, the tape 1 is not only scratched but also fixed at least 2/3, preferably not less than 3/4 of the side surface of the battery element 2 as well as the scratching portion in order to fix the battery element 2 after the tape is cured. It is desirable to cover. At this time, it is necessary to cover the electrode plate end portion 5 with the tape 1 without overlapping the electrode plate end portion 5 and the end portion of the tape 1 due to squeezing. Further, regarding the thickness of the thermosetting resin layer, a thicker battery element can be produced, but conversely, the volume energy density is lowered accordingly. Therefore, it is preferable that the thickness of the tape including the base material layer and the adhesive layer is about the same as that of the conventional tape. Furthermore, the bottom portion can be covered with a bottom protective tape 3 in order to protect the bottom portion of the battery element opposite to the lead-out portion of the electrode terminal 4 of the battery element 2 when inserted into the battery can.

  The battery element that has been squeezed with tape is inserted into a battery can or packaged by being housed in a laminate film, and then the thermosetting resin is cured by heating or the like. As for the heating temperature, heating is performed at a temperature that does not deteriorate the battery performance, for example, a temperature that does not affect the separator, and the time may be a time sufficient for the resin to thermoset at that temperature. Thereafter, an electrolytic solution is injected, and the inlet is sealed to complete the assembly of the nonaqueous electrolyte secondary battery. Thereafter, charge and discharge are performed to complete the nonaqueous electrolyte secondary battery.

  Hereinafter, the present invention will be specifically described based on examples.

(Example 1)
A positive electrode plate formed with LiCoO ₂ as a positive electrode active material on an aluminum foil, and a negative electrode plate formed with graphite as a negative electrode active material on a copper foil were laminated via a separator and wound, and length: 39 mm, width: 33 mm, thickness S: A 3.7 mm battery element was produced.

  Next, the tape will be described. 28μm of adhesive layer made of one-component thermosetting epoxy resin is applied on the PPS base material layer of length: 36mm, width: 68mm, thickness: 12μm (finished tape thickness is 40μm), and the adhesive strength is peeled off 180 degrees A tape having a thickness of 0.078 or more (N / 25 mm) was prepared by a method and used as a tape for squeezing. Similarly, an adhesive layer made of a one-component thermosetting epoxy resin was applied on a PPS substrate layer having a length of 8 mm, a width of about 37 mm, and a thickness of 12 μm to prepare a bottom protective tape.

  Next, referring to FIG. 2, the tape stoppage will be described. The electrode plate terminal portion 5 of the battery element 2 was wound with the squeezing tape 1 and the side surface of the battery element was covered over almost one turn except for the central part. Further, a bottom protective tape 3 was attached to the bottom surface of the battery element 2. Thereafter, the battery element was molded and dried, and at the same time, the epoxy resin layer was dried at a constant thickness of 110 ° C. for 5 hours in order to cure. Then, it was housed in a laminate film, and an electrolyte solution was poured into a nonaqueous electrolyte secondary battery.

(Comparative Example 1)
Each tape was coated with 28 μm of an adhesive layer made of an acrylic resin on a PPS substrate layer of length: 36 mm, width: 68 mm, thickness: 12 μm, length: 8 mm, width: 37 mm, thickness: 12 μm. A tape of 0.078 or more (N / 25 mm) was produced by a 180-degree peeling method, and used as a tape for scratching and a tape for protecting the bottom. After affixing a tape for scratching and a tape for protecting the bottom to the battery element produced in the same manner as in Example 1, the battery element was molded and dried at a constant thickness of 110 ° C. for 5 hours for drying. It was. Then, it accommodated in the laminate film and inject | poured electrolyte solution, it was set as the nonaqueous electrolyte secondary battery.

(Evaluation 1) Thickness Measurement The thickness of the thickest part at the center of the battery at the time of 50% charge after the initial charge / discharge of the nonaqueous electrolyte secondary battery obtained in Example 1 and Comparative Example 1 was measured. FIG. 3 shows the measurement results of the 275 thickest portions in Example 1 and Comparative Example 1 as differences from the upper limit specification of the battery thickness. As can be seen from FIG. 3, the thickness of the thickest portion of the nonaqueous electrolyte secondary battery after the initial charge is less varied in Example 1 than in Comparative Example 1. In Example 1, Cp (process capability) = 3.481 and σ (standard deviation) = 0.010, and in Comparative Example 1, Cp = 1.726 and σ = 0.177. This is gasified internally by the decomposition of the electrolyte mainly occurring in the initial charging, and the distance between the electrodes is widened by distorting the jelly roll. As a result, it is considered that the battery swells. However, when a tape having a thermosetting resin layer is used, the spread of the distance between the electrodes can be suppressed, so that the variation in Example 1 is less than that in Comparative Example 1. It is thought that it was made.

(Evaluation 2) Impedance Measurement Next, an AC impedance measurement at 1 kHz after the initial charging of the nonaqueous electrolyte secondary battery obtained in Example 1 and Comparative Example 1 was performed. FIG. 4 shows 275 impedance measurement results of Example 1 and Comparative Example 1 as differences from the upper limit standard. From FIG. 4, it can be seen that the impedance after the initial charging of the nonaqueous electrolyte secondary battery was less varied in Example 1 than in Comparative Example 1. In Example 1, Cp = 3.761 and σ = 0.0842, and in Comparative Example 1, Cp = 2.165 and σ = 1.105. This is due to gasification inside due to the decomposition of the electrolyte that occurs mainly during initial charging, and the distance between the electrodes increases due to distortion of the jelly roll, resulting in an increase in resistance inside the battery, resulting in an increase in impedance. When a tape having a curable resin layer is used, the spread of the distance between the electrodes can be suppressed. Therefore, it is considered that Example 1 was able to reduce impedance variation more than the comparative example.

(Evaluation 3) Drop test Next, the nonaqueous electrolyte secondary battery obtained in Example 1 and Comparative Example 1 was dropped on the concrete from a height of 1.9 m after the initial charge, and the voltage and impedance were measured each time. (AC 1 kHz) was measured. The end condition of the drop test was when the voltage dropped by 0.1 V from the initial voltage or when the impedance increased by 10 mΩ. That is, it is considered that a decrease in voltage confirms that there is no defect due to a short circuit inside the battery, and an increase in impedance occurs because the distance between the electrodes increases due to distortion of the jelly roll caused by dropping. Further, it is considered that the impedance rises when the electrode terminal welded to the electrode plate is cut by an impact or the like.

  Example 1 and Comparative Example 1 Table 1 shows the number of times until the drop test was completed when 5 pieces each were subjected to a drop test.

  As shown in Table 1, in Example 1, it can be confirmed that the number of times until the end of the drop test is larger than that in Comparative Example 1. This is because the tape including the thermosetting resin layer functions like an inner pack, the impact strength due to dropping is improved from that in Comparative Example 1 in Example 1, and the distortion of the jelly roll due to dropping is suppressed. It is thought that the rise in In addition, since the electrode plates are more closely adhered to each other because distortion of the jelly roll is suppressed, the welded portion of the electrode terminal welded to the electrode plate is difficult to move. It is presumed that the dropout of the welded part was delayed and the drop resistance was improved.

(Example 2)
Next, the battery element produced in the same manner as in Example 1 was scratched using the following tape. That is, 12 μm of a thermosetting layer made of a one-component thermosetting epoxy resin is applied on a PPS base material layer having a length of 36 mm, a width of 68 mm, and a thickness of 12 μm, and an adhesive layer made of an acrylic resin is further applied by 28 μm. (Finished tape thickness: 52 μm), and having an adhesive strength of 0.078 or more (N / 25 mm) by a 180-degree peeling method, was used as a tape for scratching prevention. Similarly, 12 μm of a thermosetting layer made of a one-component thermosetting epoxy resin is applied on a PPS base material layer having a length of 8 mm, a width of 37 mm, and a thickness of 12 μm, and an adhesive layer made of an acrylic resin is further applied. 28 μm was applied to produce a bottom protective tape.

  In the subsequent steps, the thermosetting layer was dried and cured by heating in the same manner as in Example 1, and then accommodated in a laminate film, injected with an electrolytic solution, and then subjected to the same steps as in the prior art to obtain a nonaqueous electrolyte secondary battery. .

  Next, evaluations 1 to 3 were performed in the same manner as in Example 1 and Comparative Example 1. As a result, although a better result was shown in terms of variation than Comparative Example 1, the variation was larger than Example 1.

  This is considered to be because the strength as the inner pack was lowered because the thermosetting layer was thinner than in Example 1. In this experiment, since the thickness of the tape itself is increased, the stacked thickness of the battery element is thicker than that of the first embodiment, and the thinner first embodiment is more effective.

The side view of the tape used for the nonaqueous electrolyte secondary battery of 1st embodiment of this invention. The front view which shows the middle process of the non-aqueous electrolyte secondary battery of this invention. The thickest part measurement result of Example 1 and Comparative Example 1. The impedance measurement result of Example 1 and Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 (For tearing prevention) Tape 1a Thermosetting resin layer 1b Base material layer 2 Battery element 3 (For bottom part protection) Tape 4 Electrode terminal 5 Electrode board terminal part

Claims (7)

  In a non-aqueous electrolyte secondary battery in which a battery element in which a positive electrode plate and a negative electrode plate are stacked and wound via a separator is housed in an exterior body, the battery element is wound and covered with a tape including a thermosetting resin layer. Then, a non-aqueous electrolyte secondary battery characterized by curing a thermosetting resin.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the tape has a two-layer structure of an adhesive layer made of a thermosetting resin layer and a base material layer.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the tape has a three-layer structure including a base material layer, a thermosetting resin layer, and an adhesive layer.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the tape has a two-layer structure of a base material layer made of a thermosetting resin layer and an adhesive layer.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the tape has a two-layer structure of a base material layer made of a thermosetting resin layer and an adhesive layer made of a thermosetting resin layer.   The non-aqueous electrolyte secondary battery according to claim 1, wherein the tape is made of a thermosetting resin layer.   The non-aqueous electrolyte according to any one of claims 1 to 6, wherein the thermosetting resin layer contains at least one of urea resin, phenol resin, melamine resin, epoxy resin, and silicon resin. Secondary battery.

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