JP2006032052A - Battery device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide battery structure preventing the generation of overvoltage in sudden current shut off by decreasing inductance component in a battery. <P>SOLUTION: A wound electrode body is prepared by piling a positive electrode foil and a negative electrode foil through a separator, winding them from the central part in the length direction of each electrode foil, and positioning the electrode foil end parts of a positive electrode and a negative electrode in the winding end. Alternatively, the electrode winding body is prepared by spirally winding from the the end part of the electrode foil as usual, and when a positive electrode lead and a negative electrode lead are installed in the positive electrode foil and the negative electrode foil, the leads are arranged in the positions as near as possible. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery device for a primary battery and a secondary battery.

  In recent years, with the development of portable electronic devices such as notebook personal computers and mobile phones, the demand for batteries has been rapidly increasing, and the use of batteries has been expanded. Under such circumstances, battery design is moving toward smaller size and higher capacity, and at the same time, higher safety is required when the battery is used.

  Currently, primary and secondary batteries (hereinafter, appropriately referred to as lithium ion batteries) using lithium and lithium ions as a constituent material are attracting attention as batteries that meet the demand for miniaturization and high capacity.

  A lithium ion battery uses carbon or graphite as a negative electrode and combines various ceramic positive electrode agents, and is produced using a nonaqueous solvent as an electrolyte.

  The lithium ion secondary battery is a non-aqueous electrolyte battery using lithium ion doping / dedoping. A lithium ion secondary battery mainly includes a positive electrode and a negative electrode that can be doped / undoped with lithium ions, a non-aqueous electrolyte (a solution obtained by dissolving a lithium salt in an aprotic organic solvent), a positive electrode, and a negative electrode. And a separator interposed therebetween. The electrode includes a current collector and an active material layer formed on the current collector. The active material layer includes an active material, a conductive agent, and a binder that binds these materials to a current collector.

  Lithium ion batteries are advantageous in that they are small and lightweight, have high energy density, and can withstand long-term storage. Taking advantage of this, cylindrical shapes, square shapes, coin shapes, and the like are now manufactured and used in various electronic devices.

  Conventionally, a protection circuit has been provided as a safety measure against overcharge of a battery, external short circuit, and the like. As an example of a battery protection circuit, there is a thermal resistance element (hereinafter referred to as a PTC element as appropriate). The PTC element is usually an element having an extremely small resistance, but has a characteristic that the resistance value increases when an excessive current flows or when the temperature becomes high, and the current flowing through the battery is limited. By providing the battery with a PTC element, for example, even when an external short circuit occurs, the PTC element works when the temperature reaches a certain temperature and stops the battery current, thereby preventing an overcurrent from flowing through the battery.

  Patent Document 1 below proposes a protection circuit capable of reducing the current value before the battery is deteriorated or damaged even when the value of the current flowing through the battery is increased.

JP 2003-92826 A

  The internal structure of a conventional lithium ion battery is a wound electrode body in which strip-shaped electrodes are stacked and wound spirally. Therefore, as shown in FIG. 1, the conceptual equivalent circuit is considered to be a series circuit of C (battery capacity), R (internal resistance component), and L (internal inductance component), and corresponds to both ends of the battery. To do. For this reason, it has an inductance component depending on the position of the lead drawn from the electrode. When the usage method is such that a large current is intermittently taken out from the battery, a counter electromotive force due to di / dt is generated by the inductance component, and a large voltage is generated between the output terminals of the battery. In particular, in the use of an electric circuit such as a power tool or a toy having a structure in which the output terminal of the battery is opened when the current is reduced, the occurrence of overvoltage is remarkable.

  For example, FIG. 2 shows a calculation example of the voltage generated at the battery terminal when a current is intermittently passed through the electric circuit. In FIG. 2, the waveform indicated by the solid line indicates the voltage generated at the battery terminal, and the waveform indicated by the dotted line indicates the voltage applied to the load circuit.

  When a current starts to flow, a voltage is gradually applied to the battery terminal, and then becomes a constant voltage. However, when the current is set to 0, a large voltage is suddenly generated at the battery terminal due to the energy stored in the inductance component.

  In particular, when the impedance increases due to the inductance component of the battery in a high frequency range and the load current changes abruptly, the battery voltage becomes unstable. For example, FIG. 3 is a graph showing impedance characteristics of a cylindrical lithium ion secondary battery. The waveform indicated by the solid line is the impedance characteristic of the battery, and the waveform indicated by the dotted line is the background during measurement. The actual impedance can be obtained by the difference between the value indicated by the solid line and the value indicated by the dotted line. The impedance increases as the frequency becomes higher.

  FIG. 4 is a graph showing voltage characteristics of a cylindrical lithium ion secondary battery, and shows voltage characteristics when the load current is switched from 10 A to 0 A as an example. When the load current is suddenly switched from 10 A to 0 A, the battery voltage, which was 4 V, rises to 8 V. Depending on the degree of overvoltage, the voltage resistance of the FET (Field Effect Transistor) for protecting the battery, the control circuit on the side of the device used, etc. may be exceeded, which may destroy the FET, the control circuit, and the like. For this reason, it is dangerous to generate overvoltage, and there is an increasing demand for overvoltage prevention.

  Conventionally, since the number of cells connected to the device is small and the usage method is such that the fluctuation of the load current is small, the problem of overvoltage as described above is relatively small. However, in recent years, the need for countermeasures against overvoltage has increased as the use of batteries has expanded and the number of connected cells has increased. Although it is possible to take measures against overvoltage by improving the withstand voltage of the control circuit on the equipment side, a control circuit with an extremely high withstand voltage value is required and the cost increases. It is necessary to take measures against overvoltage on the battery side.

  Therefore, an object of the present invention is to provide a battery device that prevents the occurrence of an overvoltage at the time of a sudden current interruption by reducing the inductance component in the battery.

  In order to solve the above-mentioned problems, a first aspect of the present invention is a positive electrode produced by applying a positive electrode active material to a positive electrode current collector made of a sheet-like metal foil, and a negative electrode made of a sheet-like metal foil In a battery device in which a negative electrode produced by applying a negative electrode active material to a current collector is overlapped with a separator and a cylindrical wound electrode body produced by winding this is housed in an exterior body, The cylindrical wound electrode body is a battery device characterized in that it is wound from the center part in the longitudinal direction of the positive electrode and the negative electrode so that the electrode foil end portions of the positive electrode and the negative electrode come to the end of winding.

  A second aspect of the present invention is a negative electrode active material formed on a positive electrode current collector made of a sheet-like metal foil and a positive electrode produced by applying a positive electrode active material to a positive electrode current collector made of a sheet-like metal foil. Connected to a positive electrode current collector in a battery device in which a cylindrical wound electrode body produced by stacking a negative electrode produced by applying a substance on a negative electrode is wound through a separator and wound around the separator. The battery device is characterized in that the distance between the positive electrode lead and the negative electrode lead connected to the negative electrode current collector is minimized.

  The third aspect of the present invention is a negative electrode active material manufactured by applying a positive electrode active material to a positive electrode current collector made of a sheet-like metal foil and a negative electrode current collector made of a sheet-like metal foil. In a battery device in which a cylindrical wound electrode body produced by stacking a negative electrode produced by applying a substance on a negative electrode via a separator and winding the same is housed in an exterior body, the positive electrode current collector to the positive electrode The battery device is characterized in that the lead is led out, the negative electrode lead is led out from the negative electrode current collector, and at least one of the positive electrode lead and the negative electrode lead is plural.

  According to the present invention, it is possible to prevent the occurrence of an overvoltage due to a sudden current interruption, particularly in an application in which a large current is intermittently passed, such as an electric tool or an electric toy. In addition, it is possible to prevent malfunction, destruction, etc. due to overvoltage when installing a load circuit such as charge control in the secondary battery.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 5 is a cross-sectional view showing an example of the configuration of a lithium ion battery according to an embodiment of the present invention. This lithium ion battery is called a so-called cylindrical type, and a wound electrode body 10 in which a strip-like positive electrode 11 and a negative electrode 12 are wound through a separator 13 inside a substantially hollow cylindrical battery can 1. have. The battery can 1 is made of, for example, iron (Fe) plated with nickel, and has one end closed and the other end open. Inside the battery can 1, a pair of insulating plates 2 and 3 are respectively disposed perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 10.

  A battery lid 4 and a safety valve mechanism 5 and a PTC element 6 provided inside the battery lid 4 are attached to an open portion of the battery can 1 by caulking through a gasket 7. The inside of 1 is sealed. The battery lid 4 is made of, for example, the same material as the battery can 1. The safety valve mechanism 5 is electrically connected to the battery lid 4 via the heat sensitive resistance element 6, and the disk plate 5a is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 4 and the wound electrode body 10 is cut off. When the temperature rises, the heat-sensitive resistance element 6 limits the current by increasing the resistance value and prevents abnormal generation due to a large current. For example, the gasket 7 made of barium titanate semiconductor ceramics is used. Is made of, for example, an insulating material, and the surface is coated with asphalt.

  For example, the wound electrode body 10 is wound around a center pin 14. A positive electrode lead 15 made of aluminum (Al) or the like is connected to the positive electrode 11 of the wound electrode body 10. The positive electrode lead 15 is electrically connected to the battery lid 4 by being welded to the safety valve mechanism 5. The negative electrode lead 16 is welded and electrically connected to the battery can 1.

<Positive electrode 11>
The positive electrode 11 includes, for example, a positive electrode current collector having a band shape and a positive electrode mixture layer formed on one or both surfaces of the positive electrode current collector. The positive electrode current collector is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

The positive electrode mixture layer is composed of a positive electrode active material and a binder. Specific examples of the positive electrode mixture layer include LiCoO ₂ and LiNiO ₂ . Moreover, as a binder contained in this positive mix layer layer, the well-known binder normally used for this kind of battery can be used. Examples of the binder include fluorine resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene.

  Moreover, you may make it contain a conductive material, the additive which expresses various functions, etc. in a positive mix layer as needed. The conductive material is not particularly limited as long as it can be mixed with an appropriate amount of the active material to impart conductivity, and examples thereof include carbon powders such as graphite and carbon black.

  As a method for forming the positive electrode active material layer, for example, a powdery positive electrode active material is mixed with a solvent together with a binder (binder), and if necessary, a dispersion paint is formed by a ball mill, a sand mill, a twin-screw kneader or the like. Thereafter, a method of applying and drying on the positive electrode current collector is suitably used. In this case, the type of the solvent used is not particularly limited as long as it is inactive to the positive electrode current collector and can dissolve the binder. For example, N-methyl-2-pyrrolidone or the like is generally used. Any organic solvent can be used. The coating apparatus is not particularly limited, and examples thereof include slide coating, extrusion type die coating, reverse roll, gravure, knife coater, kiss coater, micro gravure, rod coater, blade coater and the like. The drying method is not particularly limited, and examples thereof include standing drying, a blast dryer, a hot air dryer, an infrared heater, and a far infrared heater.

<Negative electrode 12>
The negative electrode 12 includes, for example, a negative electrode current collector having a band shape and a negative electrode mixture layer formed on one or both surfaces of the negative electrode current collector. The negative electrode current collector is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.

  The negative electrode mixture layer is composed of a negative electrode active material and a binder. Specific examples of the negative electrode mixture layer include carbonaceous materials such as pyrolytic carbons, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers, and activated carbon.

  As the binder contained in the positive electrode mixture layer, known binders usually used in this type of battery can be used. Examples of the binder include fluorine resins such as polyvinyl fluoride, polyvinylidene fluoride, and polytetrafluoroethylene.

  As a method for forming the negative electrode active material layer, the same method as that for the positive electrode active material layer described above can be used.

<Separator 13>
The separator 13 separates the positive electrode mixture layer 11b and the negative electrode mixture layer 12b. The separator 13 is, for example, a porous film made of a polyolefin-based material such as polypropylene or polyethylene, or a porous film made of an inorganic material such as a nonwoven fabric made of a ceramic material, and these two or more kinds of porous films It is good also as a structure which laminated | stacked.

  In the lithium ion battery having such a structure, the following configuration is used to prevent overvoltage.

  As an overvoltage prevention measure according to the first embodiment of the present invention, an electrode winding structure capable of preventing the occurrence of overvoltage will be described.

  FIG. 6 schematically shows an electrode winding structure in an existing lithium ion battery. FIG. 7 schematically shows an electrode winding structure in a battery manufactured by applying the present invention. In addition, in order to show the winding structure of positive electrode foil and negative electrode foil in an easy-to-understand manner, illustration of separators and the like disposed between the positive electrode foil and the negative electrode foil is omitted in FIGS.

  The electrode winding structure in the existing lithium ion battery shown in FIG. 6 is such that a positive electrode foil indicated by reference numeral 21 and a negative electrode foil indicated by reference numeral 22 are overlapped, and spirally wound from an end portion of the electrode foil. It is made by turning.

  An example of a wound electrode body produced by applying the present invention is shown in FIG. In this wound electrode body, a positive electrode foil indicated by reference numeral 31 and a negative electrode foil indicated by reference numeral 32 are overlapped via a separator, and then wound from the center in the longitudinal direction of each electrode foil. Each electrode foil end portion of the negative electrode is prepared so as to come to the end of winding.

  By adopting this configuration, the direction of the current generated in the electrode foil can be reversed in the portion where the inductance component has been generated conventionally. Thereby, the direction of the magnetic flux generated by the inductance component is reversed, and the inductance component can be substantially reduced.

  FIG. 8 shows voltage characteristics when the load current is switched from 10 A to 0 A in the lithium ion battery manufactured using the spirally wound electrode body shown in FIG. When the load current is suddenly switched from 10 A to 0 A, the voltage of the battery, which was 4 V in the conventional lithium ion battery, rises to 8 V. However, in the case of the lithium ion battery manufactured using the present invention, 5.8 V It can be suppressed by a voltage increase of a certain degree.

  Next, a method for preventing the occurrence of overvoltage by changing the lead-out position of the electrode lead will be described as an overvoltage prevention measure according to the second embodiment of the present invention.

  FIG. 9 schematically shows a state in which an electrode foil of an existing lithium ion battery is developed. Reference numeral 41 indicates a positive electrode foil, and reference numeral 42 indicates a negative electrode foil. A positive electrode lead 41 a and a negative electrode lead 42 a for connecting the electrode foil and the battery outer package are provided on each of the positive electrode foil 41 and the negative electrode foil 42. In an existing lithium ion battery, a wound electrode body is manufactured by installing a positive electrode lead 41a and a negative electrode lead 42a at opposite ends of each electrode foil.

  FIG. 10 schematically shows a current flow when the positive electrode lead 41a and the negative electrode lead 42a are installed. The illustration of the separator disposed between the positive electrode foil 41 and the negative electrode foil 42 is omitted, and it is assumed that the positive electrode foil 41 and the negative electrode foil 42 are filled with an electrolytic solution.

  In this case, the current introduced from the negative electrode lead 42a flows through the electrolyte from the negative electrode foil 42 to the positive electrode foil 41, and then flows through the positive electrode lead 41a to the external electric circuit.

  FIG. 11 shows a state in which an electrode foil of a lithium ion battery manufactured by applying the present invention is developed. Reference numeral 51 indicates a positive electrode foil, and reference numeral 52 indicates a negative electrode foil. Unlike the existing lithium ion battery shown in FIG. 9, the distance between the lead positions of the positive electrode lead 51a and the negative electrode lead 52a connected from the positive electrode foil 51 and the negative electrode foil 52 is made as small as possible.

  The current flow in this case is schematically shown in FIG. In addition, the separator arrange | positioned between the positive electrode foil 51 and the negative electrode foil 522 is abbreviate | omitted, and the electrolyte solution shall be filled in the circumference | surroundings of the positive electrode foil 51 and the negative electrode foil 52. FIG.

  When the present invention is applied, in order for the current to flow from the negative electrode lead 52a to the positive electrode lead 51a, it can be roughly divided into three paths: a path A, a path B, and a path C. In this case, in the path B and the path C, the current flowing on the negative electrode foil 52 side and the current flowing on the positive electrode foil 51 side are in opposite directions, and the inductance component is suppressed. Therefore, only the inductance component due to the current in the path A is generated.

  Therefore, the inductance component can be suppressed by minimizing the distance between the lead positions of the positive electrode lead 51 a and the negative electrode lead 52 a connected from the positive electrode foil 51 and the negative electrode foil 52.

  Further, as a third embodiment, as shown in FIG. 13, a configuration in which an inductance component is suppressed by installing a plurality of positive electrode leads 51 a and negative electrode leads 52 a drawn from the positive electrode foil 51 and the negative electrode foil 52. Is also possible.

  The embodiment of the present invention has been specifically described above, but the present invention is not limited to the above-described embodiment, and various modifications based on the technical idea of the present invention are possible.

  For example, in the third embodiment, not only the one electrode lead is plural and the other electrode lead is one, but a configuration in which plural positive leads and plural negative leads are derived is used. Also good.

It is a basic diagram which shows an example of the conceptual equivalent circuit in a lithium ion battery. It is a basic diagram which shows the example of calculation of the voltage which arises in a battery terminal when an electric current is sent through an electric circuit intermittently. It is a basic diagram which shows the impedance characteristic of a cylindrical lithium ion secondary battery. It is a basic diagram which shows the voltage characteristic at the time of switching load current from 10A to 0A. It is sectional drawing which shows an example of a structure of the lithium ion battery which can apply this invention. It is a schematic diagram which shows the winding structure of the electrode in the existing lithium ion battery. It is a schematic diagram which shows the winding structure of the electrode in the battery by 1st Embodiment of this invention. FIG. 8 is a schematic diagram showing voltage characteristics when the load current is switched from 10 A to 0 A in the lithium ion battery manufactured using the wound electrode body shown in FIG. 7. It is a basic diagram which shows a mode that the electrode foil of the existing lithium ion battery was expand | deployed. It is a schematic diagram which shows the flow of the electric current of the existing lithium ion battery. It is a basic diagram which shows a mode that the electrode foil of the battery by 2nd Embodiment of this invention was expand | deployed. It is a schematic diagram which shows the flow of the electric current of the lithium ion battery produced by applying this invention. It is a basic diagram which shows a mode that the electrode foil at the time of installing the positive electrode lead in the battery by the 3rd Embodiment of this invention was expand | deployed. It is a schematic diagram which shows the electric current flow of the lithium ion battery produced by installing two positive electrode leads.

Explanation of symbols

21 ... Positive electrode foil 22 ... Negative electrode foil 31 ... Positive electrode foil 32 ... Negative electrode foil 41 ... Positive electrode foil 41a ... Positive electrode lead 42 ... Negative electrode foil 42a .... Negative electrode lead 51 ... Positive electrode foil 51a ... Positive electrode lead 52 ... Negative electrode foil 52a ... Negative electrode lead

Claims (4)

A positive electrode prepared by applying a positive electrode active material to a positive electrode current collector made of a sheet-like metal foil, and a negative electrode made by applying a negative electrode active material to a negative electrode current collector made of a sheet-like metal foil In a battery device in which a cylindrical wound electrode body produced by stacking and winding this through a separator is housed in an exterior body,
The cylindrical wound electrode body is manufactured by winding the positive electrode and the negative electrode from a longitudinal central portion so that the electrode foil end portions of the positive electrode and the negative electrode come to the end of winding. A positive electrode prepared by applying a positive electrode active material to a positive electrode current collector made of a sheet-like metal foil, and a negative electrode made by applying a negative electrode active material to a negative electrode current collector made of a sheet-like metal foil In a battery device in which a cylindrical wound electrode body produced by stacking and winding this through a separator is housed in an exterior body,
A battery device, wherein a distance between a positive electrode lead connected to the positive electrode current collector and a negative electrode lead connected to the negative electrode current collector is minimized. The battery device according to claim 2,
A battery device, wherein the positive electrode lead and the negative electrode lead are led out from substantially the same position of each of the positive electrode current collector and the negative electrode current collector. A positive electrode prepared by applying a positive electrode active material to a positive electrode current collector made of a sheet-like metal foil, and a negative electrode made by applying a negative electrode active material to a negative electrode current collector made of a sheet-like metal foil In a battery device in which a cylindrical wound electrode body produced by stacking and winding this through a separator is housed in an exterior body,
A battery device, wherein a positive electrode lead is led out from the positive electrode current collector, a negative electrode lead is led out from the negative electrode current collector, and at least one of the positive electrode lead and the negative electrode lead is plural.

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