JP2000106167A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve discharge voltage, prolong discharge time, uniformize distribution of reaction current density, and improve the battery discharge characteristic, by providing plural positive and negative electrode collector terminals on the electrodes, in the longitudinal direction of the electrode without overlapping the location of the positive and negative electrode collector terminals each other. SOLUTION: Positive electrode collector terminals 3 are mounted by ultrasonic welding at two longitudinally trisected positions of a positive electrode, composed of a positive electrode collector 2 and positive electrode active material layers 1 of portions which is not applied with positive electrode active material layers 1 on the positive electrode collector 2. Negative electrode collector terminals 7 are mounted by the ultrasonic welding, through separators 4 at three positions of both ends and the center of a negative electrode composed of a negative electrode collector 6 and a negative electrode active material layer 5 of a portion which is not applied with a negative electrode active material layer 5 of the negative electrode collector 6. After the positive electrode, negative electrode and the separators 4 are overlapped and wound, and the tips of the two positive electrode collector terminals 3 are welded into a single terminal. The tips of the three negative electrode collector terminals 7 are put together into one, and contained within a battery container as a battery body. Then, an electrolyte is injected, and sealed, to form a battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current collecting structure for a battery, which minimizes energy loss due to internal resistance and effectively utilizes an electrode active material filled in an electrode.
In addition to improving the energy density of the battery and making the electrode reaction uniform, overcharging and overdischarging are suppressed.

[0002]

2. Description of the Related Art As portable electronic devices become smaller and thinner in recent years, batteries used as power sources for devices, especially secondary batteries which can be repeatedly charged and discharged, are required to be smaller, thinner and have improved performance. Is coming. Above all, lithium ion secondary batteries have attracted attention as batteries that can drive electronic devices for a longer time, are lightweight, easy to carry, and have high capacities. Therefore, in the present invention, a lithium ion battery will be described as an example.

The structure of an electrode body composed of a negative electrode, a separator, and a positive electrode is known to be a bobbin type, a laminated type, or a spiral type. However, general portable devices such as personal computers and mobile phones require high pulse discharge. Generally, a spiral electrode structure is used.

In particular, in the case of a wound electrode body structure, the current collecting terminal structure has a structure in which a current is taken out from each of the positive and negative electrode ends. The negative electrode current collector terminal is generally formed by welding or crimping an elongated, foil-like metal such as copper or nickel to the electrode foil, while the positive electrode current collector terminal is generally made mainly of aluminum.

[0005]

[0005] Lithium ion secondary batteries are often used as power sources for small portable devices at present.
Further, it is also expected to be used as a power source for electric vehicles that require a large capacity, and it is considered that development of a high-output, high-capacity battery will proceed.

In such applications, it is common to use a plurality of cells (the minimum unit battery body composed of a negative electrode, a separator, and a positive electrode is referred to as a cell) in series or in parallel. Since it is necessary to increase the output and capacity of the battery unit in the minimum unit as compared with the conventional battery, long electrodes (negative electrode and positive electrode) are used, and accordingly, the current value is relatively large. .

At this time, in the conventional structure in which the current collecting terminal is attached to one position of the electrode end, the energy density is large,
When charging or discharging a battery having a large output density, the resistance of the current collecting terminal and the contact resistance between the current collecting terminal and the electrode cannot be ignored, which causes a reduction in charge / discharge efficiency, a decrease in discharge voltage, and the like. . Also, since the electrode is long, the portion of the electrode close to the current collecting terminal is easy to work, while the portion far from the current collecting terminal of the electrode is difficult to work, and current distribution occurs in the length direction of the electrode, so that the electrode surface In this case, there is a problem that overcharging and overdischarging are partially caused in the inside, and the temperature is locally increased due to the concentration of these currents.

[0008] The present invention solves the above-mentioned problems, and collects current by dispersing a current generated by an electrode reaction.
Another object is to reduce energy loss and suppress overcharge and overdischarge by making the electrode reaction distribution uniform.

[0009]

A first battery according to the present invention comprises a separator between each of a positive electrode comprising a positive electrode current collector and a positive electrode active material layer and a negative electrode comprising a negative electrode current collector and a negative electrode active material layer. And a battery container having a seal portion for hermetically sealing and housing the battery body, wherein each of the electrodes has a plurality of positive current collecting terminals and a negative current collecting terminal, each of which has a length equal to the length of each electrode. The positive electrode current collecting terminal and the negative electrode current collecting terminal are arranged so as not to overlap with each other.

A second battery according to the present invention is a battery according to the first battery, wherein a plurality of positive current collecting terminals and a plurality of negative current collecting terminals respectively extend out of the battery container from a sealing portion of the battery container. .

According to a third battery of the present invention, in the second battery, the positive current collecting terminal and the negative current collecting terminal extend out of the battery container from the opposite side of the battery container.

A fourth battery according to the present invention is the above-mentioned second battery, wherein each of the positive electrode current collecting terminal and the negative electrode current collecting terminal is
It is one that has come out of the battery container from the opposite side of the battery container.

A fifth battery according to the present invention is the battery according to any one of the first to fourth aspects, wherein at least one of the separator and the positive electrode or the separator and the negative electrode is bonded with an ionic conductive adhesive layer. .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to FIGS. 1 to 7 by taking a lithium ion secondary battery as an example. Embodiment 1 FIG. (Production of Positive Electrode) 91 parts by weight of a positive electrode active material made of LiCoO _2, 6 parts by weight of artificial graphite as a conductive material, and polyvinylidene fluoride as a binder (hereinafter abbreviated as PVDF)
A cathode active material paste prepared by dispersing 3 parts by weight of N-methylpyrrolidone (hereinafter abbreviated as NMP) is coated and dried by a doctor blade method on a cathode current collector made of an aluminum foil having a thickness of 20 μm. , Coating) to form a positive electrode active material film. Further, a positive electrode active material paste is applied to the back surface of the positive electrode current collector by a doctor blade method, and a positive electrode active material film is formed on both surfaces of the positive electrode current collector. ) Was prepared. The thickness of the positive electrode active material on each side of the aluminum foil was 90 μm.

The above prepared positive electrode is 129 mm × 300 m
The electrode was cut to a size of m, and two uncoated portions for welding the current collecting terminals were provided at two positions 100 mm from the longitudinal end of the electrode. The length of this uncoated part is 129 mm and the width is 5 mm
And A current collecting terminal made of an aluminum foil having a thickness of 0.1 mm and a width of 3 mm serving as a lead was attached to the uncoated aluminum foil by ultrasonic welding. Note that the current collecting terminal may be directly attached without setting the active material uncoated portion. Further, the positive electrode current collector is not limited to a foil, and may be a mesh.

(Preparation of Negative Electrode) 90 parts by weight of a negative electrode active material comprising mesophase carbon microbeads, and PVDF
The negative electrode active material paste prepared by dispersing 10 parts by weight in NMP was coated on a negative electrode current collector made of copper foil having a thickness of 12 μm by a doctor blade method, and the negative electrode active material coated portion was uncoated. A negative electrode active material film having a processed portion was formed. Further, a negative electrode active material paste was pattern-coated on the back surface of the negative electrode current collector to form a negative electrode active material film having a negative electrode active material coated portion and an uncoated portion, and then pressed to form a negative electrode. The thickness of the negative electrode active material on each surface of the negative electrode current collector was 90 μm.

The prepared negative electrode (electrode) was 130 mm ×
It was cut to a size of 380 mm. The uncoated portion of the copper foil is provided at the end in the longitudinal direction and has a length of 130 mm and a width of 5 mm, and is further provided at positions 100 mm and 200 mm from the end to have a length of 130 mm and a width of 5 mm. A current collecting terminal made of copper having a thickness of 0.1 mm and a width of 3 mm was attached to the uncoated portion by ultrasonic welding. The mounting method may include caulking the current collector foil and the current collector terminal, and the current collector terminal is not limited to copper but may be a conductive metal such as nickel. Further, the installation position of the negative electrode current collecting terminal may not be the active material uncoated portion.

FIG. 1 is a view showing the arrangement of current collecting terminals in this embodiment, and is shown as a developed view of a battery body manufactured using the above-mentioned electrodes and separator. As the separator 4, a 25 μm porous polypropylene sheet (Celgard, manufactured by Hoechst) was used. The positive electrode current collector terminal 3 is attached to a portion of the positive electrode current collector 2 where the positive electrode active material layer 1 is not applied by ultrasonic welding. Attachment positions are two places, and are equal positions in the longitudinal direction of the positive electrode (the positive electrode active material layer 1 and the positive electrode current collector foil 2). On the negative electrode side, a negative electrode current collecting terminal 7 is attached to a portion of the negative electrode current collector 6 on which the negative electrode active material layer 5 is not applied, by ultrasonic welding, with the separator 4 interposed therebetween. There are three mounting positions, both ends of the negative electrode (negative electrode active material layer 5 and positive electrode current collector foil 6) and the center of the negative electrode. After winding the positive electrode, the negative electrode and the separator 4 one on top of the other,
The three positive electrode current collecting terminals 3 are welded at the tip to combine them into one, and similarly, the three negative electrode current collecting terminals 7 are welded together at the tip to form a single battery body. Stored in a container,
After injecting the electrolyte, the battery container is sealed and hermetically sealed.
The number of the current collecting terminals is not limited to the above-mentioned number, and the present invention is characterized in that the positive terminal and the negative terminal are alternately arranged.

FIG. 2 shows a comparative example in which one positive electrode current collecting terminal and one negative electrode current collecting terminal are attached to each electrode. In the case of this comparative example, the current generated by the electrode reaction flows through the current collector and concentrates on one current collecting terminal. The current generated at the electrode portion farthest from the current collecting terminal needs to flow from one end to the other in the length direction (lateral direction in FIG. 2) of the current collector. If the total current value is larger than the length of the electrode, the voltage drop due to the resistance of the current collector cannot be ignored, current distribution in the electrode occurs, and the electrode reaction at the electrode near the current collection terminal occurs. Relatively large.

FIG. 3 is a diagram showing the calculation results of the electrode reaction distribution in the first embodiment. In a battery in which a plurality of current collecting terminals are arranged on each of the positive electrode and the negative electrode, 10 minutes have elapsed since the start of discharging. It shows an electrode reaction distribution at a later time. The calculation conditions are described below. Positive electrode size is 130m long
m, 300 mm in width, and the electrode geometrical area was 780 cm ² assuming that the coating was applied to both sides of the electrode foil. The negative electrode had the same area for the sake of calculation. Assuming that the current is 2000 mA, a current flows from the tip of the positive current collecting terminal to the tip of the negative current collecting terminal as a starting point for supplying current to the tip of the three negative current collecting terminals and the tip of the two positive current collecting terminals. As
Electrode reaction resistance and solution resistance were calculated as constant conditions in the electrode plane. FIG. 3 shows the results calculated under the above conditions. A in FIG. 3 is a portion where the reaction current density is the lowest,
This is an area of 2.48 mA / cm ² . B is a portion where the reaction current density is the highest and is a region of 2.64 mA / cm ² , and the maximum and the minimum are the average reaction current density of 2.56 mA / cm ^2.
It can be seen that the reaction current density distribution is only ± 3% with respect to cm ² .

FIG. 4 is a diagram showing the calculation results of the electrode reaction distribution in the comparative example shown in FIG. In the figure, A is a region of 2.18 mA / cm ² where the reaction current density is the lowest, and B is a region of 2.94 mA / cm ² where the reaction current density is the highest. From this figure, it can be seen that the reaction current density distribution of ± 15% of the maximum and minimum with respect to the average reaction current density occurs, and the electrode reactions are particularly concentrated near the current collecting terminals.

As described above, when the electrode reaction concentrates on the electrode in the vicinity of the current collecting terminal, the temperature locally rises due to the heat generated by the electrode reaction, and the risk of thermal runaway of the battery increases. Although thermal runaway does not occur during normal charge / discharge, it is more likely to occur if terminals are shorted carelessly or a large current exceeding the standard is applied to the battery.

FIG. 5 is a diagram showing discharge curves of the first embodiment and a comparative example. The test conditions are as follows. The test temperature is 25 degrees Celsius, 3 hours at a 1C rate (current value at which discharge is completed in 1 hour), and a constant current of an upper limit voltage of 4.1 V /
After charging at a constant voltage for 10 minutes and resting, the battery was discharged to a battery voltage of 3 V at a rate of 1 C. In this embodiment in which a plurality of current collecting terminals are provided for each electrode, the discharge voltage is higher and the discharge time is longer than in the comparative example, and it can be seen that uniformity of the reaction current density distribution improves the battery discharge characteristics. .

Embodiment 2 FIG. FIG. 6 is a plan view of the battery according to the second embodiment, and has a structure in which each of the positive electrode current collecting terminal and the negative electrode current collecting terminal is taken out of the battery container from two places via the seal portion 9. . By adopting such a structure of the current collecting terminal, a plurality of current collecting terminals can be welded outside the battery container, so that a welded portion when the plurality of current collecting terminals are welded inside the battery container occupies. There is an advantage that the space can be effectively utilized, the effective electrode can be filled up to just before the battery container, and the volume energy density is improved, and at the same time, the welding step is eliminated in the step of forming the electrode into a winding form. In addition, as shown in the plan view of FIG. 7, each of the positive electrode current collecting terminal and the negative electrode current collecting terminal has a structure in which each of the positive electrode current collecting terminal and the negative electrode current It becomes unnecessary to weld the terminals and the negative current collecting terminals.

Embodiment 3 FIG. 8 is a plan view of the battery according to the third embodiment, and has a structure in which a positive electrode current collecting terminal and a negative electrode current collecting terminal are drawn out from the opposite direction of the battery container via a seal portion 9. With such a structure of the current collecting terminal, the electrode reaction distribution can be further flattened, and the local concentration of the reaction current density can be reduced. In addition, since the current collecting terminals are relatively far from each other, a short circuit due to careless handling can be suppressed, and handling during battery manufacturing or initial characteristic evaluation before shipping can be facilitated.

Embodiment 4 Embodiment 4 relates to an adhesive type battery. An adhesive is applied to each of the two separators on one side of the negative electrode manufactured in the first embodiment. Thereafter, before the adhesive is dried, it is brought into close contact with both sides of the negative electrode, bonded and then dried to form a negative electrode with a separator. As an adhesive, 7 parts by weight of PVDF was dissolved and 9 parts by weight of aluminum oxide powder were dispersed in N
Use MP solution. In the case of bonding with this adhesive, when the electrolytic solution is injected, an adhesive layer having ion conductivity holding the electrolytic solution is formed. A 25 μm porous polypropylene sheet is used as a separator. The adhesive is PV
In addition to DF, a polymer such as polyvinyl alcohol, polyvinyl butyrate, and polymethyl methacrylate may be used. The aluminum oxide powder is added so that the adhesive layer easily becomes a porous body, and may be a fine powder such as graphite or silica gel, or may not be added. Solvent is also NM
Not limited to P. The concentration is not limited to 5 parts by weight.

The positive electrode prepared in the first embodiment was sandwiched between the separator surfaces of the two negative electrodes with a separator to form a rolled-up battery body. The battery body was housed in a battery container, and an electrolyte was injected. Thereafter, the battery container is sealed and hermetically sealed.

Table 1 shows that the batteries shown in Embodiment 4 and Comparative Example were 4.15 V and 4.25 at an ambient temperature of 53 degrees Celsius.
V and 4.35 V, and the result is that a 2.5 mm diameter iron nail was inserted into the center of the battery. In the fourth embodiment, there is no abnormality under any conditions, and heat is generated by overdischarge by bonding the current collecting terminal structure, the electrode, and the separator.
It can be seen that ignition and the like can be suppressed.

[0029]

[Table 1]

Although the structure in which the negative electrode and the separator are bonded is shown in the fourth embodiment, the same effect can be obtained by bonding the positive electrode and the separator, or by bonding both the positive electrode and the negative electrode. Can be Furthermore, it is not necessary to bond the entire surface of the separator and the electrode, and it is sufficient that at least one portion is bonded.

[0031]

As described above, according to the first battery of the present invention, each electrode of the positive electrode comprising the positive electrode current collector and the positive electrode active material layer and the negative electrode comprising the negative electrode current collector and the negative electrode active material layer A battery including a battery body having a separator between the batteries, and a battery container having a seal portion for sealing and housing the battery body, wherein each of the electrodes has a plurality of positive current collecting terminals and a plurality of negative current collecting terminals. A plurality of electrodes are provided in the length direction of the electrode, and the positions of the positive electrode current collecting terminal and the negative electrode current collecting terminal are arranged so as not to overlap with each other.
This has the effect of making the distribution of the reaction current density uniform and improving the battery discharge characteristics.

According to the second battery of the present invention, since each of the plurality of positive current collecting terminals and the plurality of negative current collecting terminals extends out of the battery container from the sealing portion of the battery container, the plurality of current collecting terminals can be connected. Since welding can be performed outside the battery container, the space occupied by the welded portion when multiple current collecting terminals are welded inside the battery container can be effectively used, and the effective electrode can be filled just before the battery container. This has the effect of improving the volume energy density and eliminating the need for a welding step at the time of forming the electrode into a winding form.

According to the third battery of the present invention, since the positive electrode current collecting terminal and the negative electrode current collecting terminal extend outside the battery container from the opposite side of the battery container, the positive electrode current collecting terminals and the negative electrode current collecting terminal are separated from each other. There is no need to weld the electrical terminals.

According to the fourth battery of the present invention, since each of the positive electrode current collecting terminal and the negative electrode current collecting terminal comes out of the battery container from the opposite side of the battery container, the electrode reaction distribution is further flattened. Local concentration of the reaction current density can be reduced. In addition, since the current collecting terminals are relatively far from each other, short-circuiting due to careless handling can be suppressed, and there is an effect that handling at the time of battery manufacture or at the time of initial characteristic evaluation before shipping can be facilitated.

According to the fifth battery of the present invention, there is an effect that heat generation, ignition, and the like due to overdischarge in which at least one of the separator and the positive electrode or the separator and the negative electrode is bonded by the ionic conductive adhesive layer can be suppressed.

[Brief description of the drawings]

FIG. 1 is a layout diagram of a current collecting terminal according to the first embodiment.

FIG. 2 is a layout view of a current collecting terminal of a comparative example.

FIG. 3 is a diagram showing calculation results of an electrode reaction distribution according to the first embodiment.

FIG. 4 is a diagram showing a calculation result of an electrode reaction distribution in a comparative example.

FIG. 5 is a diagram showing discharge curves of the batteries of Embodiment 1 and Comparative Example.

FIG. 6 is a plan view of a first battery according to a second embodiment.

FIG. 7 is a plan view of a second battery according to a second embodiment.

FIG. 8 is a plan view of a battery according to a third embodiment.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 positive electrode active material layer, 2 positive electrode current collector, 3 positive electrode current collector terminal, 4 separator, 5 negative electrode active material layer, 6 negative electrode current collector, 7 negative electrode current collector terminal, 8 battery container, 9 seal portion, A, A 'Low reaction current density region, B, B' High reaction current density region,

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hisashi Shioda 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Jun Arakane 2-3-2 Marunouchi, Chiyoda-ku, Tokyo 3 Rishi Electric Co., Ltd. (72) Inventor Makiko Yoshise 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. Inside (72) Inventor Daigo Takemura 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Takashi Nishimura 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Hiroki Ozaki 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation (72) Inventor Hideo Ichimura Maru, Chiyoda-ku, Tokyo 2-3-2 Uchi, Mitsubishi Electric Co., Ltd. (72) Inventor Kenji Kawaguchi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Tokyo (72) Masaharu Moriyasu, Inventor Marunouchi 2, Chiyoda-ku, Tokyo 2-3-2, Mitsui Electric Co., Ltd. (72) Inventor Shinji Nakaguchi 2-3-2, Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 5H022 AA09 BB12 CC08 CC12 CC20 CC22 5H029 AJ02 AJ03 AK03 AL08 CJ05 DJ05 EJ01

Claims (5)

[Claims] 1. A battery body having a separator between each of a positive electrode comprising a positive electrode current collector and a positive electrode active material layer and a separator comprising a negative electrode comprising a negative electrode current collector and a negative electrode active material layer;
A battery comprising a battery container having a sealing portion for housing, wherein a plurality of positive current collecting terminals and a plurality of negative current collecting terminals are provided on each of the electrodes in the length direction of each electrode, and A battery characterized in that the current collecting terminal and the negative electrode current collecting terminal are arranged without overlapping. 2. The battery according to claim 1, wherein each of the plurality of positive electrode current collecting terminals and the plurality of negative electrode current collecting terminals protrudes out of the battery container from a sealing portion of the battery container. 3. The battery according to claim 2, wherein the positive current collecting terminal and the negative current collecting terminal extend out of the battery container from the opposite side of the battery container. 4. The battery according to claim 2, wherein each of the positive electrode current collecting terminal and the negative electrode current collecting terminal extends out of the battery container from the opposite side of the battery container. 5. The battery according to claim 1, wherein at least one of the separator and the positive electrode or the separator and the negative electrode is bonded with an ion-conductive adhesive layer.