Secondary battery and method for manufacturing secondary battery

Abstract

To provide a secondary battery capable of achieving both capacity increase and self-discharge suppression.SOLUTION: A secondary battery 1 according to the present disclosure includes a positive electrode, a negative electrode, and a separator 50 disposed between the positive electrode and the negative electrode, wherein the positive electrode includes a positive electrode active material 40 containing at least one of nickel hydroxide and manganese oxide, the negative electrode includes a negative electrode current collector 10 and a negative electrode active material 20, a first metal layer 11 is disposed on a surface of the negative electrode current collector, a second metal layer 12 is disposed on a surface of the first metal layer, the first metal layer has higher alkali corrosion resistance than the second metal layer, and the negative electrode active material contains porous carbon.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a secondary battery and a method for manufacturing a secondary battery, and more particularly to an alkaline secondary battery and a method for manufacturing an alkaline secondary battery. [Background technology]

[0002] In recent years, the importance of batteries has rapidly increased in many industries, and various new battery systems that have advantages mainly in terms of capacity, energy density, and rechargeability have been developed and improved.

[0003] Patent Document 1 discloses an alkaline secondary battery in which the zinc negative electrode uses porous carbon as the base material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-187977 Summary of the Invention [Problem to be solved by the invention]

[0005] It is preferable to consider the overvoltage caused by hydrogen generation during the charge and discharge process of secondary batteries. In addition, improving the charge and discharge capacity of secondary batteries and improving the self-discharge characteristics by expanding the plateau range (the region where the voltage remains constant relative to the change in battery capacity during charge and discharge evaluation) are issues that must always be addressed.

[0006] The present disclosure has been made to solve such problems, and has an object to provide a secondary battery that achieves both increased capacity and suppressed self-discharge. [Means for solving the problem]

[0007] The secondary battery according to the present disclosure includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode includes a positive electrode active material containing at least one of nickel hydroxide and manganese oxide, and the negative electrode includes a negative electrode current collector and a negative electrode active material, wherein a first metal layer is disposed on a surface of the negative electrode current collector and a second metal layer is disposed on a surface of the first metal layer, the first metal layer having higher alkaline corrosion resistance than the second metal layer, and the negative electrode active material contains porous carbon. This makes it possible to provide a secondary battery that achieves both increased capacity and reduced self-discharge.

[0008] The negative electrode current collector may contain a metal selected from Cu, Fe, and Ni, or an alloy containing at least one of them, the first metal layer may contain In, and the second metal layer may contain a metal selected from Sn and Zn, or an alloy thereof, thereby providing a secondary battery that achieves both increased capacity and reduced self-discharge.

[0009] The thickness of the first metal layer may be 1 μm or less, and the thickness of the second metal layer may be 5 μm or more, thereby providing a secondary battery that achieves both increased capacity and reduced self-discharge.

[0010] The first metal layer and the second metal layer may be entirely or partially alloyed, thereby providing a secondary battery that achieves both increased capacity and reduced self-discharge.

[0011] The method for manufacturing a secondary battery according to the present disclosure includes forming a first metal layer on the surface of a negative electrode current collector by a first plating process, and forming a second metal layer on the surface of the first metal layer by a second plating process, the first metal layer having higher alkaline corrosion resistance than the second metal layer, thereby providing a secondary battery that achieves both increased capacity and reduced self-discharge. [Effects of the Invention]

[0012] The present disclosure makes it possible to provide a secondary battery that achieves both increased capacity and reduced self-discharge. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram illustrating an example of a secondary battery according to a first embodiment. [Figure 2] 1 is a graph showing evaluation results of secondary batteries of Examples and Comparative Examples. [Figure 3] 1 is a graph showing evaluation results of secondary batteries of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Fig. 1(a) is a diagram showing an example structure of a secondary battery 1 according to the present disclosure. The secondary battery 1 shown in the example of Fig. 1(a) has a configuration including a negative electrode current collector 10, a negative electrode active material 20, a positive electrode current collector 30, a positive electrode active material 40, and a separator 50, some of which are immersed in an electrolyte solution 60. In the present disclosure, the negative electrode current collector 10 and the negative electrode active material 20 are referred to as the negative electrode, and the positive electrode current collector 30 and the positive electrode active material 40 are referred to as the positive electrode.

[0015] Fig. 1(b) is an enlarged view of the area surrounded by the dotted line in Fig. 1(a), namely, the vicinity of the surface of the negative electrode current collector 10. As shown in Fig. 1(b), a first metal layer 11 and a second metal layer 12 are formed on the surface of the negative electrode current collector 10, and a porous material 110, an inorganic additive 120, and a binder 130 are formed on the surface of the second metal layer 12. Hereinafter, the porous material 110, the inorganic additive 120, and the binder 130 will be referred to as a negative electrode active material 20.

[0016] The negative electrode current collector 10 may be made of any material as long as it is electrically conductive, such as metal or graphite, with metal being preferred in terms of electrical conductivity and workability. The metal may be a metal selected from Cu, Fe, or Ni, or stainless steel or an alloy containing at least one of the above metals. Furthermore, the metal may be surface-treated by plating, reflow plating, etching, or the like, with plated metal being preferred in terms of operating potential. An example of the negative electrode current collector 10 is a Cu foil plated with Ni.

[0017] The first metal layer 11 formed on the surface of the negative electrode current collector 10 is a metal material with low hydrogen generating overvoltage and high alkaline corrosion resistance, and is a material with high hydrogen generating overvoltage that easily forms an alloy with the current collector and also easily forms an alloy with the first metal layer 11, and for example, In is preferred.

[0018] The second metal layer 12 formed on the surface of the first metal layer 11 is made of a metal material having lower alkaline corrosion resistance than the metal material contained in the first metal layer 11, and preferably contains, for example, a metal selected from Sn and Zn, or an alloy thereof. The thickness of the first metal layer 11 is preferably 1 μm or less, and the thickness of the second metal layer 12 is preferably 5 μm or more. The first metal layer 11 and the second metal layer 12 are preferably formed by plating. That is, the method for producing a secondary battery according to the present disclosure forms the first metal layer 11 on the surface of the negative electrode current collector 10 by a first plating process, and forms the second metal layer 12 on the surface of the first metal layer 11 by a second plating process.

[0019] The first metal layer 11 and the second metal layer 12 may be at least one layer, or may be laminated, such as a third metal layer containing the same metal material as the first metal layer 11 on the first metal layer 11 and the second metal layer 12, a fourth metal layer containing the same metal material as the second metal layer 12 on the third metal layer, etc. The laminate of the first metal layer 11 and the second metal layer 12 may be alloyed in whole or in part. Either or both of the first metal layer 11 and the second metal layer 12 may contain a very small amount of another metal.

[0020] The entire or part of the stack of first metal layer 11 and second metal layer 12 may be alloyed by carrying out a treatment to promote alloying, such as heating.

[0021] The negative electrode active material 20 is disposed on the surface of the negative electrode current collector 10, and a porous material 110, an inorganic additive 120, and a binder 130 are formed thereon.

[0022] The porous material 110 preferably contains porous carbon (activated carbon), which is carbon powder particles that have a large specific surface area and exhibit high hydrophilicity. 2 True density and 500m 2 / g~5000m 2 The average particle size and pore distribution of the porous carbon are not particularly limited, and the porous carbon may have a single particle size or may contain different particle sizes.

[0023] The method for forming the negative electrode active material 20 is not limited, but examples include a method in which an ink is produced by mixing a porous material 110, an inorganic additive 120, a binder 130, a conductive additive, zinc oxide, an inorganic or organic additive, a surfactant, etc., and then the ink is applied to the negative electrode active material 20, dried, and pressed to form the negative electrode active material 20. The weight ratio of the ink is preferably composite (porous carbon):conductive additive:zinc oxide:additive:binder=approximately 90:10:1:0.1:7. The surfactant may be contained in any amount.

[0024] In addition, the negative electrode active material 20 according to the present disclosure may contain an appropriate amount of powder or alloy powder made of the same or similar metal as the first metal layer 11 and the second metal layer 12 laminated on the negative electrode current collector 10. This allows the degree of suppression of self-discharge to be controlled. The amount is not particularly limited, but is preferably within 10 wt % of the porous carbon.

[0025] The conductive additive is preferably one that has conductivity and high chemical stability, such as acetylene black, carbon black, or carbon nanofiber. There are no particular restrictions on the particle size of the conductive additive, but it is preferable that the particle size be 0.1 μm to 50 μm.

[0026] The inorganic additive is preferably powder particles of bismuth oxide (Bi2O3) and indium oxide (In2O3). The average particle size of the bismuth oxide is preferably less than 1 μm, and the average particle size of the indium oxide is preferably less than 50 μm. The organic additive is preferably oxalic acid.

[0027] The binder 130 is preferably made of styrene butadiene rubber (SBR), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), modified polyolefin, or the like, due to its chemical stability.

[0028] It is preferable to use Ni, Ni-plated steel sheet, or porous nickel for the positive electrode current collector 30. It is preferable that the positive electrode active material 40 contains at least one of nickel hydroxide (Ni(OH)2) and manganese oxide (Mn2O3).

[0029] The separator 50 preferably uses either or both of a hydrophilic or hydrophilized nonwoven fabric and a microporous film such as polypropylene (PP).

[0030] The electrolyte 60 is preferably an aqueous potassium hydroxide (KOH) solution containing zinc oxide or tin oxide dissolved in a weight ratio of 0 to 15 wt % at a concentration of 3 M to 7 M. To improve performance, the electrolyte may also contain other inorganic salts such as LiOH and NaOH.

[0031] The secondary battery 1 according to the present disclosure can achieve both increased capacity and suppressed self-discharge by using, as the negative electrode active material 20, a composite active material in which highly conductive carbon powder particles and inorganic oxide powder particles are uniformly formed on the surface of porous carbon having a large specific surface area.

[0032] Furthermore, hydrogen overvoltage can be suppressed by providing a first metal layer 11 having high alkaline corrosion resistance and a second metal layer 12 having lower alkaline corrosion resistance than the first metal layer 11 on the surface of the metal foil that is the negative electrode current collector 10 that collects current from the negative electrode active material 20. In a battery in which carbon particles with a large specific surface area are arranged on the surface of the negative electrode current collector, the effects of both increasing capacity and suppressing self-discharge can be obtained by arranging one or more metals on the negative electrode current collector. [Example]

[0033] The secondary battery according to the present disclosure will be described in detail with reference to examples and comparative examples, but the secondary battery according to the present disclosure is not limited to the following examples.

[0034] Example 1 A 30 μm thick Ni foil was used as the negative electrode current collector, and In was plated to a thickness of 1 μm (first metal layer) and Zn to a thickness of 5 μm (second metal layer). 2 / g, activated carbon particles with an average particle size of 10 μm, acetylene black with a particle size of 0.04 μm, fine Bi2O3 particles with an average particle size of 3 μm, and general-purpose In2O3 and SBR dispersion were mixed in a solid weight ratio of 90:10:2.5:0.03:7, and pure water was added to give a viscosity of 10 Pa·s. The mixture was then stirred and degassed to produce a black ink.

[0035] The black ink was uniformly applied to the negative electrode current collector, dried, and roll-pressed, and a 120 μm-thick tin-plated copper foil was joined to the tab end using a resistance welder to form a negative electrode.

[0036] The positive electrode was a composite electrode of nickel Celmet and Co-coated Ni(OH)2, and was selected so that the capacity ratio of the negative electrode to the positive electrode (negative electrode capacity ÷ positive electrode capacity) was approximately 1.5. 100 μm Ni foil was welded to the terminal.

[0037] The positive electrode was entirely wrapped in a 150 μm thick hydrophilic nonwoven fabric, and two negative electrodes were used to sandwich one positive electrode, forming a secondary battery according to the present disclosure.

[0038] The secondary battery was placed in a case, and 0.5 wt%, 2.3 wt%, and 0.3 wt% of LiOH, NaOH, and ZnO were added to a 6M KOH solution as an electrolyte, respectively. After appropriate amounts were dropped, the case was sealed and left to stand for a certain period of time to prepare a single cell.

[0039] This single cell was subjected to one cycle of 0.2C CC charge (Cutoff: 1.65V) and 0.2C CC discharge (Cutoff: 1.1V) and two cycles of 0.5C CC charge (Cutoff: 1.65V) and 0.5C CC discharge (Cutoff: 1.1V) to activate the battery.

[0040] <Example 2> The basic structure and materials were the same as in Example 1, but the metal on the surface of the current collector was changed from Sn to a Zn / Sn=50 / 50 alloy.

[0041] Example 3 The basic structure and materials were the same as in Example 1, but the zinc oxide in the mixture was changed to a zinc alloy.

[0042] <Comparative Example 1> Only In plating was formed on the negative electrode current collector, that is, the second metal layer was not formed.

[0043] <Comparative Example 2> The negative electrode current collector was plated with In only, i.e., no second metal layer was provided, and the amount of zinc oxide powder in the carbon powder active material was increased (activated carbon powder:AB:zinc oxide powder (particle size 0.75 μm), SBR dispersion solution = 70:10:30:6), except for which the other components were the same as in Example 2.

[0044] <Comparative Example 3> No plating was performed on the negative electrode current collector, that is, the first metal layer and the second metal layer were not provided. The carbon powder active material was the same as in Example 1.

[0045] An example of the results of charge / discharge measurements is shown in Figure 2. Improvements were confirmed in charge and discharge in Example 1 compared to Comparative Example 1.

[0046] An example of the results of the self-discharge measurement is shown in Fig. 3. It was confirmed that Example 1 had improved self-discharge properties compared to Comparative Example 1.

[0047] Table 1 shows a comparison of the results of charge / discharge measurements and self-discharge measurements. [Table 1] *1: Indicates the time it takes for the secondary battery voltage to reach 1.2V after charging has stopped and the battery has been left unused.

[0048] In Example 1, the battery capacity was significantly increased and the self-discharge characteristics were also significantly improved compared to Comparative Example 1. This shows that providing the second metal layer on the first metal layer results in a composition and configuration that suppresses hydrogen overvoltage.

[0049] For Example 2, characteristics were obtained that were approximately the same as those for Example 1. This shows that good characteristics can be obtained even when the second metal layer is made of an alloy material.

[0050] For Example 3, characteristics were obtained that were approximately the same as those for Examples 1 and 2. This shows that good characteristics can be obtained even when a zinc alloy is used instead of zinc oxide as the negative electrode active material.

[0051] By comparing the results of Comparative Examples 1, 2, and 3 with Example 1, it is clear that the lamination of the first metal layer and the second metal layer has a significant effect on the battery capacity and self-discharge characteristics.

[0052] The present disclosure is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the present disclosure. [Explanation of symbols]

[0053] 1 Secondary battery 10 Negative electrode current collector 11 1st metal layer 12 Second metal layer 20 Negative electrode active material 30 Positive electrode current collector 40 Cathode active material 50 Separator 60 Electrolyte 110 Porous materials 120 Inorganic Additives 130 Binder

Claims

1. a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; the positive electrode comprises a positive electrode active material containing at least one of nickel hydroxide and manganese oxide; the negative electrode includes a negative electrode current collector and a negative electrode active material, a first metal layer is disposed on a surface of the negative electrode current collector; a second metal layer disposed on a surface of the first metal layer; the first metal layer has higher alkali corrosion resistance than the second metal layer; The negative electrode active material includes porous carbon. Secondary battery.

2. the negative electrode current collector contains a metal selected from Cu, Fe, and Ni, or an alloy containing at least one of them, the first metal layer contains In; The second metal layer contains a metal selected from Sn and Zn, or an alloy thereof. The secondary battery according to claim 1 .

3. the thickness of the first metal layer is 1 μm or less; The thickness of the second metal layer is 5 μm or more. The secondary battery according to claim 1 or 2.

4. The stack of the first metal layer and the second metal layer is entirely or partially alloyed. The secondary battery according to claim 1 or 2.

5. forming a first metal layer on the surface of the negative electrode current collector by a first plating treatment; forming a second metal layer on the surface of the first metal layer by a second plating process; The first metal layer has higher alkaline corrosion resistance than the second metal layer. A method for manufacturing a secondary battery.

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