JP5261861B2 - Secondary battery - Google Patents

Description

  The present invention relates to a secondary battery in which an electrode plate is accommodated in an exterior member and sealed, and electrode terminals connected to the electrode plate are led out from an outer peripheral edge of the exterior member.

An electrode in which a positive electrode plate in which a positive electrode active material is applied to a positive electrode side current collector made of metal foil and a negative electrode plate in which a negative electrode side current collector made of metal foil is applied to a negative electrode active material are alternately stacked via separators 2. Description of the Related Art Conventionally, a secondary battery in which a laminate is housed in an exterior member and sealed, and a positive electrode plate and a negative electrode plate are connected to a positive electrode terminal and a negative electrode terminal, respectively, and the electrode terminal is led out from the exterior member is known. Yes. Such secondary batteries are required to have further improved output density and longer life (for example, see Patent Document 1).
JP-A-9-213301

An object of this invention is to provide the secondary battery which can aim at the improvement of output density and lifetime.
In order to achieve the above object, according to the present invention, a current collector and a plurality of electrodes having electrode layers formed on a main surface of a part of the current collector and stacked via separators An exterior member that is formed of a plate and a film-like member and accommodates and seals the laminated electrode plates in a flat plate shape; and an external member that is connected to the electrode plate and that is connected to the outer periphery of the exterior member and a electrode terminal is derived to the electrode terminal includes a positive terminal, the electrode plate, the includes a positive electrode plate connected to the positive terminal, and the positive electrode terminal, the positive electrode plate The positive electrode side current collector has a main component made of the same material, and a thin secondary battery that satisfies the following conditional expression (1) is provided.

Sa> Sb Formula (1)
However, in the above-mentioned conditional expression (1), Sa is a cross-sectional area of the positive electrode terminal, Sb is the total cross-sectional area of the positive electrode side current collector.

In the present invention, the cross-sectional area of the positive electrode terminal (Sa), is larger than the total cross-sectional area of the positive electrode side current collector having the positive electrode plate connected to the positive terminal (Sb). Thus, the resistance of the positive electrode terminal is less than the resistance of the positive electrode side current collector, it is possible to improve the output density.

Further, by satisfying the conditional expressions (1), since the heat generation of the positive electrode terminal is smaller than the heat generation of the positive-electrode current collector, the heat of the positive electrode side current collector is transferred to the positive electrode terminal, further from the positive terminal Since heat is radiated to the outside, the temperature rise of the secondary battery can be suppressed and the battery life can be extended.

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

  FIG. 1 is a plan view showing the entirety of a thin secondary battery (hereinafter also simply referred to as “thin battery”) according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view taken along line II-II in FIG. is there.

FIG. 1 shows one thin battery (unit battery). An assembled battery having a desired voltage and capacity is configured by connecting a plurality of the thin batteries 10.

  The overall configuration of the thin battery 10 according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. The thin battery 10 of this example is a lithium-based thin secondary battery and includes three positive plates. 101, seven separators 102, three negative plates 103, a positive electrode terminal 104, a negative electrode terminal 105, an upper exterior member 106, a lower exterior member 107, and an electrolyte (not shown). Yes. The number of the positive electrode plate 101, the separator 102, and the negative electrode plate 103 is not limited at all, and may be one positive electrode plate 101, three separators 102, and one negative electrode plate 103, and if necessary, the positive electrode The number of plates 101, the negative electrode plate 103, and the separator 102 can be selected and configured. In FIG. 2, for convenience of explanation, the positive electrode plate 101, the separator 102, the negative electrode plate 103, and the exterior members 106 and 107 are illustrated as being separated from each other. .

  The positive electrode plate 101 of this embodiment includes a positive electrode current collector 101a connected to the positive electrode terminal 104 via a positive electrode lead 101c, and a positive electrode layer 101b formed on both main surfaces of the positive electrode current collector 101a. Have. Similarly, the negative electrode plate 103 includes a negative electrode side current collector 103a connected to the negative electrode terminal 105 via a negative electrode lead 103c, and a negative electrode layer 103b formed on both main surfaces of the negative electrode side current collector 103a. Have. Further, a separator 102 is interposed between the positive electrode layer 101 b of the positive electrode plate 101 and the negative electrode layer 103 b of the negative electrode plate 103.

In this embodiment, LiMn ₂ O ₄ belonging to a lithium-containing composite oxide is used as a positive electrode active material, carbon black belonging to a carbon-based material is used as a conductive material, and polyvinylidene fluoride (PVDF) is used as a binder. A positive electrode active material and a conductive material are mixed, and a slurry is prepared by uniformly dispersing the mixed positive electrode active material and the conductive material in N-methyl-2-pyrrolidone (NMP) in which polyvinylidene fluoride is dissolved. The slurry is uniformly applied on the aluminum metal foil to be the positive electrode current collector 101a, NMP is evaporated, and the roll is pressed by a roll press to produce the positive electrode layer 101b on the aluminum metal foil 101a. The weight ratio of LiMn ₂ O ₄ to be mixed, carbon black, and polyvinylidene fluoride (PVDF) is 75 to 85:10 to 20: 5 to 10, preferably 85: 10: 5 to 75:20. : 5. After the positive electrode layer 101b is manufactured, the positive electrode plate 101 is obtained by cutting into a predetermined size. The thickness of the positive electrode layer 101b of the positive electrode plate 101 of this embodiment is preferably 50 μm to 150 μm, and more preferably 60 μm to 120 μm.

As the positive electrode active material, in addition to LiMn ₂ O ₄ , lithium manganese composite oxide (LiMnO ₂ ), layered structure LiMnO ₂ , spinel structure LiMnO ₂ , LiMnO ₄ ), lithium nickel composite oxide (LiNiO ₂ ), lithium cobalt oxide (LiCoO ₂ ), lithium iron phosphate compound (LiFePO ₄ ), lithium manganese phosphate compound (LiMnPO ₄ ), lithium vanadium composite oxide (LiV ₂ O ₄ ), lithium titanium composite oxide (LiTi ₂ O ₄ ), Other lithium composite oxides such as LiM _X O _Y (M is a transition element, X and Y include a constant ratio and an indefinite ratio) can be given.

  In this embodiment, hard carbon belonging to a carbon-based material is used as a negative electrode active material, and polyvinylidene fluoride (PVDF) is used as a binder. Hard carbon and polyvinylidene fluoride (PVDF) are mixed at a weight ratio of 90:10 and dispersed in N-methyl-2-pyrrolidone (NMP) to produce a slurry. It apply | coats uniformly on the copper metal foil used as 103a, NMP is evaporated, It rolls with a roll press, and the negative electrode layer 103b is produced on the copper metal foil 103a. The prepared negative electrode layer 103b is cut into a predetermined size to obtain the negative electrode plate 103.

  Examples of the negative electrode active material include materials that occlude and release lithium ions of the positive electrode active material, such as amorphous carbon including hard carbon, non-graphitizable carbon, graphitizable carbon, or graphite. I can do it.

  The separator 102 prevents the short-circuit between the positive electrode plate 101 and the negative electrode plate 103 described above, and may have a function of holding an electrolyte. The separator 102 is a microporous film made of polyolefin such as polyethylene (PE) or polypropylene (PP), for example, and when an overcurrent flows, the pores of the film are blocked by the heat generation, thereby blocking the current. It also has. The separator of the present invention is not limited to a single-layer film such as polyolefin, but a three-layer structure in which a polypropylene layer is sandwiched with polyethylene layers, or a laminate of a polyolefin microporous film and an organic nonwoven fabric can be used. . By forming the separator 102 in multiple layers, various functions such as an overcurrent prevention function, an electrolyte holding function, and a separator shape maintenance (rigidity improvement) function can be provided. Further, instead of the separator 102, a gel electrolyte or an intrinsic polymer electrolyte can be used.

  The positive electrode plates 101 and the negative electrode plates 103 are alternately stacked in such an order that the separators 102 are positioned between the positive electrode plates 101 and the negative electrode plates 103, and further, the separators are provided at the uppermost and lowermost parts. 102 are stacked one by one.

  Each of the three positive plates 101 has a positive current collector 101a connected to a positive electrode terminal 104 made of metal foil via a positive lead 101c, while the three negative plates 103 have a negative electrode side A current collector 103a is connected to a negative electrode terminal 105, also made of metal foil, through a negative electrode lead 103c.

  Examples of the material constituting the positive electrode terminal 104 include an electrochemically stable metal material such as aluminum or an aluminum alloy.

  In the present embodiment, the positive electrode terminal 104 has a cross-sectional area Sa larger than the total cross-sectional area (total cross-sectional area) Sb of all the positive electrode side current collectors 101a so as to satisfy the following conditional expression (1). .

Sa> Sb Formula (1)
Thereby, since the resistance of the positive electrode terminal 104 becomes smaller than the resistance of the positive electrode current collector 101a, the output density can be improved. Further, since the cross-sectional area Sa of the positive electrode terminal 104 is made larger than the total cross-sectional area Sb of the positive electrode side current collector 101a, the heat generation of the positive electrode terminal 104 becomes smaller than the heat generation of the positive electrode side current collector 101a. Since the heat of the current collector 101a is transmitted to the positive electrode terminal 104 and further radiated from the positive electrode terminal 104 to the outside, the temperature rise of the thin battery 10 can be suppressed and the life of the thin battery 10 can be extended.

  In the present embodiment, the cross-sectional area Sa of the positive electrode terminal 104 is a cross-sectional area along a direction substantially perpendicular to the lead-out direction of the positive electrode terminal 104, and the width of the positive electrode terminal 104 shown in FIG. It is calculated by multiplying Wa by the thickness Ta of the positive terminal 104 shown in FIG. Similarly, the cross-sectional area of the positive current collector 101a constituting the total cross-sectional area Sb is also a cross-sectional area along a direction substantially perpendicular to the direction in which the positive terminal 104 is led out, and is shown in FIG. The width Wb of the current collector 101a is multiplied by the thickness Tb of the positive current collector 101a shown in FIG. 2 and the number of layers of the positive current collector 101a (for example, the number of layers in this embodiment is 3). Is calculated by

  Furthermore, when the cross-sectional shape of the positive electrode terminal 104 changes along the lead-out direction of the positive electrode terminal 104, the cross-sectional area Sa of the positive electrode terminal 104 is the smallest cross-sectional area among them. Similarly, when the cross-sectional shape of the positive current collector 101a changes along the lead-out direction of the positive terminal 104, the total cross-sectional area Sb of the positive current collector 101a is the smallest cross-sectional area among them. It is.

  In the present embodiment, the positive electrode terminal 104 has a volume Va smaller than the total volume Vb of all the positive electrode side current collectors 101a so as to satisfy the following conditional expression (2). The volume Va is smaller than ½ of the total volume of the positive electrode side current collector 101a so as to satisfy the formula (3).

Va <Vb Formula (2)
Va <1/2 × Vb Formula (3)
At this time, the positive electrode terminal 104 is set to satisfy the following conditional expression (4), and is preferably set to satisfy the following conditional expression (5).

Sa <Sb × Lb / La (4)
Sa <1/2 × Sb × Lb / La (5)
By satisfying the above relational expression, the resistance per volume (weight) of the positive electrode terminal 104 becomes smaller than the resistance per volume (weight) of the positive electrode side current collector 101a, and the output density of the thin battery 10 is improved. I can do it.

The volume Va of the positive electrode terminal 104 is calculated by multiplying the cross-sectional area Sa of the positive electrode terminal 104 by the length La (see FIG. 1) of the positive electrode terminal 104 (Va = Sa × La). Similarly, the total volume Vb of the positive electrode current collector 101a is calculated by multiplying the total cross-sectional area Sb of the positive electrode current collector 101a by the length Lb (see FIG. 1) of the positive electrode current collector 101a (see FIG. 1). Vb = Sb × Lb). The length La of the positive electrode terminal 104 is the total length of the positive electrode terminal 104 along the lead-out direction. Similarly, the length Lb of the positive electrode current collector 101a is a length along the lead-out direction of the stacked positive electrode current collector 101a and includes the lead portion 101c. In addition, when the length of each laminated | stacked positive electrode side collector 101a differs, Lb is calculated by those average values.

  Examples of the material constituting the negative electrode terminal 105 include nickel, copper, and stainless steel. The negative electrode terminal 105 is also set so as to satisfy the above conditional expressions (1) to (5). However, since the positive electrode terminal 104 generally has a higher resistance than the negative electrode terminal 105, the positive electrode terminal 104 The terminal 104 can obtain a larger output density improvement effect and cooling effect than the negative electrode terminal 105.

  The positive electrode plate 101, the negative electrode plate 103, the separator 102, and the like are sealed by the upper exterior member 106 and the lower exterior member 107. The upper exterior member 106 and the lower exterior member 107 are, for example, flexible films such as a resin-metal thin film laminate material obtained by laminating both surfaces of a resin film such as polyethylene or polypropylene, or a metal foil such as aluminum with a resin such as polyethylene or polypropylene. It is made of a material having properties.

  The upper exterior member 106 and the lower exterior member 107 enclose the positive electrode plate 101, the negative electrode plate 103, the separator 102, a part of the positive electrode terminal 104, and a part of the negative electrode terminal 105, and the exterior members 106, 107. After injecting a liquid electrolyte with a lithium salt such as lithium perchlorate or lithium borofluoride as a solute in an organic liquid solvent, the outer periphery of the upper exterior member 106 and the lower battery exterior member 107 is heat-sealed into the space formed by It seals by methods, such as.

  Examples of the liquid electrolyte organic liquid solvent sealed in the space formed by the exterior members 106 and 107 include ester solvents such as propylene carbonate (PC), ethylene carbonate (EC), and dimethyl carbonate (DMC). The organic liquid solvent of the present invention is not limited to this. An organic liquid solvent prepared by mixing and preparing an ether solvent such as γ-butylactone (γ-BL) and dietoshietane (DEE) in an ester solvent. It can also be used.

  The positive electrode terminal 104 is led out from one end of the sealed exterior members 106 and 107, but there is a gap at the joint between the upper exterior member 106 and the lower exterior member 107 by the thickness of the positive electrode terminal 104. Therefore, in order to maintain the sealing performance in the thin battery 10, a sealing film made of polyethylene or polypropylene is applied to the portion where the positive electrode terminal 104 and the exterior members 106 and 107 are in contact with each other. Can also be interposed. Similarly, the negative electrode terminal 105 is led out from the other end portion of the sealed exterior members 106 and 107. Here, similarly to the positive electrode terminal 104 side, the negative electrode terminal 105 and the exterior members 106 and 107 It is also possible to interpose a seal film at the part where the contact is made. In any of the positive electrode terminal 104 and the negative electrode terminal 105, it is desirable from the viewpoint of heat-sealing that the seal film is made of the same type of resin as the resin constituting the exterior members 106 and 107.

  The embodiment described above is described for facilitating the understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  Hereinafter, the effects of the present invention were confirmed by examples and comparative examples that further embody the present invention. The following examples and comparative examples are for confirming the effects of the thin battery according to the above-described embodiment.

Example 1
A powder prepared by mixing carbon black (conductive material) and polyvinylidene fluoride (PVDF) with LiMn ₂ O ₄ (positive electrode active material) is dispersed in N-methyl-2-pyrrolidone (NMP) to form a slurry, and this slurry is used as the positive electrode side. After apply | coating to both main surfaces of a collector and drying, it compressed and cut | judged and produced the positive electrode plate. In Example 1, an aluminum foil having a width of 70 mm, a length (Lb) of 160 mm, and a thickness of 20 μm was used as the positive electrode side current collector.

  Hard carbon (negative electrode active material) is mixed with polyvinylidene fluoride (PVDF) and dispersed in N-methyl-2-pyrrolidone (NMP) to form a slurry. This slurry is made of copper metal foil (negative electrode side current collector). After being applied and dried, it was compressed and cut to prepare a negative electrode plate.

The positive electrode plate and the negative electrode plate thus produced were alternately laminated while sandwiching a separator between them to form an electrode laminate. At this time, in Example 1, since the three positive electrode plates described above were laminated, the total cross-sectional area (Sb) of the positive electrode side current collector was 4.2 mm ² (= 20 μm × 70 mm × 3 layers).

Each positive current collector extending from the electrode laminate was welded to the positive terminal, and each negative current collector extending from the laminate was welded to the nickel negative terminal. In Example 1, an aluminum foil having a width of 45 mm, a length (La) of 50 mm, a thickness of 100 μm, and a cross-sectional area (Sa) of 4.5 mm ² was used as the positive electrode terminal. Table 1 shows the production conditions of the positive electrode side current collector and the positive electrode terminal of the thin battery produced in Example 1.

  Next, the electrode laminate to which the electrode terminals are connected is accommodated between the two exterior members, and a part of the electrode terminals are led out from the outer peripheral edge, and the two short sides of the exterior member are After heat-sealing a total of three sides on the long side and injecting a predetermined amount of electrolyte from the opening, the remaining one side is heat-sealed while the space formed by the exterior member is decompressed. The battery sample of Example 1 was produced.

As the electrolytic solution, a solution obtained by dissolving lithium hexafluorophosphate (LiPF ₆ ) as a supporting electrolyte in a mixed solvent of polycarbonate (PC), ethylene carbonate (EC) and dimethyl carbonate (DMC) was used.

  The battery life of the battery sample of Example 1 was evaluated by the following charge / discharge cycle test. In this charge / discharge cycle test, one cycle was a charge / discharge cycle composed of four steps of charge → charge stop → discharge → discharge stop under a 45 ° C. environment, and the internal resistance value was calculated for each cycle. Then, the rate of increase of the internal resistance value after each cycle with respect to the initial internal resistance value was calculated, and the battery life was evaluated to be longer as the degree of increase in internal resistance after 1000 cycles was smaller. On the other hand, it was evaluated that the battery life was shorter as the increase in internal resistance after 1000 cycles was greater. The internal resistance value for each cycle was obtained by discharging the battery at a constant current and calculating the DC resistance using Ohm's law from the voltage drop at that time.

  In the charging step of the charge / discharge cycle, charging was performed at a current value of 10 CA (current value that discharges the entire capacity in 6 minutes), and the charging was stopped when the voltage value reached 4.2V. On the other hand, in the discharging step of the charge / discharge cycle, discharging was performed at a current value of 10 CA (current value that discharges the entire capacity in 6 minutes), and discharging was stopped when the voltage value reached 2.5V. Further, a pause time of 1 minute was provided in each pause step of the charge / discharge cycle.

  The test results of the charge / discharge cycle test of Example 1 are shown in FIG. Moreover, the power density per weight of the battery sample manufactured in Example 1 is shown in FIG.

Comparative Example 1
In Comparative Example 1, a battery sample was produced under the same conditions as in Example 1 except that the thickness of the positive electrode terminal was 50 μm. The cross-sectional area Sa of the positive electrode terminal of the battery sample of Comparative Example 1 was 2.25 mm ² . The production conditions are shown in Table 1.

  The battery life of the battery sample of Comparative Example 1 was evaluated by a charge / discharge cycle test under the same conditions as in Example 1. The test results of the charge / discharge cycle test of Comparative Example 1 are shown in FIG. Moreover, the power density per weight of the battery sample produced in Comparative Example 1 is shown in FIG.

Comparative Example 2
In Comparative Example 2, a battery sample was produced under the same conditions as in Example 1 except that the thickness of the positive electrode terminal was 200 μm. The cross-sectional area Sa of the positive electrode terminal of the battery sample of Comparative Example 2 was 9 mm ² . The production conditions are shown in Table 1.

  The battery life of the battery sample of Comparative Example 2 was evaluated by a charge / discharge cycle test under the same conditions as in Example 1. The test results of the charge / discharge cycle test of Comparative Example 2 are shown in FIG. Moreover, the power density per weight of the battery sample produced in Comparative Example 2 is shown in FIG.

Comparative Example 3
In Comparative Example 3, a battery sample was produced under the same conditions as in Example 1 except that the thickness of the positive electrode terminal was 300 μm. The cross-sectional area Sa of the positive electrode terminal of the battery sample of Comparative Example 3 was 13.5 mm ² . The production conditions are shown in Table 1.

  The battery life of the battery sample of Comparative Example 3 was evaluated by a charge / discharge cycle test under the same conditions as in Example 1. The test results of the charge / discharge cycle test of Comparative Example 3 are shown in FIG. Moreover, the power density per weight of the battery sample produced in Comparative Example 3 is shown in FIG.

Discussion As shown in FIG. 3, the battery of Comparative Example 1 has a higher internal resistance increase rate than that of Example 1 and Comparative Examples 2 and 3, and thus it can be seen that the battery life is short. This is because in the battery sample of Comparative Example 1, the cross-sectional area (Sa) of the positive electrode terminal is less than or equal to the total cross-sectional area (Sb) of the positive electrode side current collector (Sa ≦ Sb), and thus the heat generation at the positive electrode terminal is large. Thus, the heat generation of the positive electrode terminal is transmitted to the positive electrode side current collector (the heat generation of the positive electrode side current collector is not dissipated to the outside from the positive electrode terminal), and the battery temperature is higher than those of Example 1, Comparative Example 2 and Comparative Example 3. It is thought that it became.

  Further, as shown in FIG. 4, the battery of Comparative Example 1 has a lower output density than that of Example 1. This is because the resistance of the positive terminal is larger than the resistance of the positive current collector, and this resistance lowers the output density.

  Further, as shown in FIG. 4, the battery of Comparative Example 3 has a lower output density than that of Example 1. This is because the weight of the positive electrode terminal is heavier than the total weight of the positive electrode side current collector.

  Furthermore, the battery of Comparative Example 2 also has a lower output density than Example 1 as shown in FIG. In general, not all current flows from end to end of the positive current collector, and on average, it flows half of the total length of the positive current collector. The resistance is considered to be about 1/2. In contrast, in the battery of Comparative Example 2, the weight of the positive electrode terminal is heavier than ½ of the total weight of the positive electrode side current collector, and thus the output density per weight is smaller than that of Example 1. It is thought that.

FIG. 1 is a plan view showing the entire thin battery according to the first embodiment of the present invention. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. FIG. 3 is a graph showing the relationship between the rate of increase in internal resistance and the number of charge / discharge cycles of the thin battery in the example. FIG. 4 is a graph showing the output density of the thin battery in the example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Secondary battery 101 ... Positive electrode plate 101a ... Positive electrode side collector 101b ... Positive electrode layer 101c ... Lead part 102 ... Separator 103 ... Negative electrode plate 103a ... Negative electrode side current collector 103b ... Negative electrode layer 103c ... Lead part 104 ... Positive electrode terminal 105 ... Negative electrode terminal 106 ... Upper exterior member 107 ... Lower exterior member

Claims (6)

A current collector, and a plurality of electrode plates having electrode layers formed on a main surface of a part of the current collector and stacked via separators;
An exterior member that is formed of a film-like member and accommodates and seals the laminated electrode plates in a flat plate shape;
An electrode terminal connected to the electrode plate and led out from an outer peripheral edge of the exterior member, and
The electrode terminal includes a positive electrode terminal,
The electrode plate includes a positive plate connected to the positive terminal,
It said positive electrode terminal, the positive electrode plate and the positive electrode side current collector included in a main component is composed of the same material,
A thin secondary battery that satisfies the following conditional expression (1).
Sa> Sb Formula (1)
However, in the above-mentioned conditional expression (1), Sa is a cross-sectional area of the positive electrode terminal, Sb is the total cross-sectional area of the positive electrode side current collector. The secondary battery according to claim 1, wherein the following conditional expression (2) is satisfied.
Sa × La <Sb × Lb (2)
However, in the above-mentioned conditional expression (2), La is the length of the positive electrode terminal, Lb is the length of the positive electrode side current collector. The secondary battery according to claim 1 or 2, wherein the following conditional expression (3) is satisfied.
Sa × La <1/2 × Sb × Lb Formula (3)
However, in the above-mentioned conditional expression (3), La is the length of the positive electrode terminal, Lb is the length of the positive electrode side current collector. The secondary battery in any one of Claims 1-3 which satisfy | fills following conditional expression (4).
Sa <Sb × Lb / La (4)
However, the conditional expression (4), La is the length of the positive electrode terminal, Lb is the length of the positive electrode side current collector. The secondary battery in any one of Claims 1-4 which satisfy | fills the following conditional expression (5).
Sa <1/2 × Sb × Lb / La (5)
However, in the above-mentioned conditional expression (5), La is the length of the positive electrode terminal, Lb is the length of the positive electrode side current collector. The secondary battery according to claim 1, wherein the positive electrode layer of the positive electrode plate contains a lithium composite oxide .

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