Method for manufacturing secondary battery

Abstract

To provide a manufacturing method of a secondary battery for improving charge / discharge capacity.SOLUTION: In the method of manufacturing a secondary battery according to the present disclosure, the secondary battery 1 includes a positive electrode including a positive electrode active material 40 containing at least one of nickel hydroxide and manganese oxide, and a negative electrode including a negative electrode active material 20 containing porous carbon, and after the assembly step of the secondary battery, has an initial charging and discharging step of activating the secondary battery, and discharges to 0 to 0.1 V at least twice or more in the initial charging and discharging step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a secondary battery, and more particularly to 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] Improving the capacity of secondary batteries is a constant challenge, and there is still room for improvement in the activation conditions during the charge and discharge process.

[0006] The present disclosure has been made to solve such problems, and aims to provide a method for manufacturing a secondary battery that improves charge / discharge capacity. [Means for solving the problem]

[0007] In the method for manufacturing a secondary battery according to the present disclosure, the secondary battery comprises a positive electrode having a positive electrode active material containing at least one of nickel hydroxide and manganese oxide, and a negative electrode having a negative electrode current collector on which a negative electrode active material containing porous carbon is formed, and after assembling the secondary battery, the method includes an initial charge / discharge step for activating the secondary battery, in which the secondary battery is discharged at least twice to a voltage of 0 to 0.1 V. This makes it possible to provide a method for manufacturing a secondary battery that improves charge / discharge capacity.

[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, thereby providing a method for producing a secondary battery with improved charge / discharge capacity.

[0009] The porous carbon is 500m 2 / g~5000m 2 / g specific surface area, The porous carbon may have chemical functional groups on a portion of its surface, thereby providing a method for producing a secondary battery that improves charge / discharge capacity.

[0010] The chemical functional group may be a hydroxyl group or a carboxyl group, thereby providing a method for producing a secondary battery with improved charge / discharge capacity. [Effects of the Invention]

[0011] The present disclosure provides a method for manufacturing a secondary battery that improves charge / discharge capacity. [Brief explanation of the drawings]

[0012] [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. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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.

[0014] 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 porous material 110, an inorganic additive 120, and a binder 130 are formed on the surface of the negative electrode current collector 10. Hereinafter, the porous material 110, the inorganic additive 120, and the binder 130 will be referred to as a negative electrode active material 20.

[0015] The negative electrode current collector 10 may be made of any material as long as it is electrically conductive, such as metal or graphite. Metal is preferred from the viewpoints of electrical conductivity and processability. The metal is preferably a material with high stability against alkalis, such as a metal selected from Cu, Fe, and 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. Plated metals are preferred from the viewpoint of operating potential. An example of the negative electrode current collector 10 is a Cu foil plated with Ni. Furthermore, Sn- or In-based plating may be applied to suppress side reactions.

[0016] 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.

[0017] 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~5000m2 Preferably, the porous carbon has a specific surface area of ​​1 / g. The average particle size and void 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. Furthermore, the porous carbon may have a chemical functional group in part, and the functional group is preferably a hydroxyl group or a carboxyl group. By introducing such hydrophilic functional groups into the porous carbon, the dispersion stability is further improved.

[0018] The method for forming the negative electrode active material 20 is not limited, but examples include a method in which an ink is prepared by mixing a porous material 110, an inorganic additive 120, a binder 130, a carbon-based conductive additive, zinc oxide, an inorganic or organic additive, a surfactant, and the like, 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 about 90:10:1:0.1:7 (composite material (porous carbon):conductive additive:zinc oxide:additive:binder). The surfactant may be contained in any amount. The solvent is preferably about 99 parts water to about 1 part alcohol-based solvent, but this may be changed as desired depending on the viscosity and target thickness.

[0019] The conductive additive is not limited to activated carbon with a large specific surface area, but is preferably one with a high hydrogen activation voltage, and may be, for example, a carbon-based conductive material such as graphite, hard carbon, or fibrous carbon, or a metal powder containing Sn as the main component. When using a highly hydrophilic carbon conductive powder, it is preferable that the particle size be 0.01 to 1 μm, the average particle size be about 0.1 μm, and the powder be easily dispersed in pure water without the addition of additives or surfactants.

[0020] The inorganic additive is preferably powder particles of bismuth oxide (Bi2O3) and indium oxide (In2O3), and the organic additive is preferably oxalic acid.

[0021] 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).

[0022] The separator 50 preferably uses either or both of a hydrophilic or hydrophilized nonwoven fabric and a microporous film such as polypropylene (PP).

[0023] 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.

[0024] The method for manufacturing the secondary battery 1 according to the present disclosure is characterized in that, during the initial charge / discharge process for activating the secondary battery 1 after the assembly process of the secondary battery 1, particularly during discharge, activation conditions including a discharge pattern in which the lower limit voltage per battery cell is discharged to 0 V to 0.1 V are performed at least twice, thereby improving the charge / discharge capacity.

[0025] The performance improvement phenomenon is thought to be due to the fact that charging and discharging over a very wide potential range causes the electrolyte to diffuse widely, expanding the reaction area to areas that would not normally be reached.

[0026] By using a composite active material as the negative electrode active material 20, in which highly conductive carbon powder particles and inorganic oxide powder particles are uniformly formed on the surface of porous carbon with a large specific surface area, it is possible to achieve both increased capacity and suppressed self-discharge. [Example]

[0027] 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.

[0028] Example 1 A 30 μm thick Ni foil was used as the negative electrode current collector, and the specific surface area was 1000 m 2Black ink was prepared by mixing activated carbon particles with an average particle size of 60 μm, hydrophilic conductive carbon powder with an average particle size of approximately 0.1 μm, fine Bi2O3 particles with an average particle size of 3 μm, high-purity reagent In2O3, SBR dispersion, and Gemini surfactant E40 in a solids weight ratio of 90:10:2.5:0.03:7:0.05, adding pure water to give a viscosity of 10 Pa·s, stirring, and degassing.

[0029] 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.

[0030] 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.

[0031] The positive electrode was entirely wrapped in a 120 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.

[0032] The secondary battery was placed in a case, and 0.2 wt%, 2.5 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.

[0033] This single cell was activated by one cycle of 0.2C CC charge (Cutoff: 1.70V) and 0.2C CC discharge (Cutoff: 0V) followed by two cycles of 0.5C CC charge (Cutoff: 1.70V) and 0.5C CC discharge (Cutoff: 0V).

[0034] <Example 2> The basic configuration and materials were the same as in Example 1, but the activation voltage range of the break-in conditions was changed to 0.05V to 1.70V.

[0035] Example 3 The basic configuration and materials were the same as in Example 1, but the activation voltage range of the break-in conditions was changed to 0.10V to 1.70V.

[0036] <Comparative Example 1> The basic configuration and materials were the same as in Example 1, but the activation voltage range of the break-in conditions was changed to 0.90V to 1.70V.

[0037] <Comparative Example 2> The basic configuration and materials were the same as in Example 1, but the activation voltage range of the break-in conditions was changed to 1.10V to 1.70V.

[0038] <Comparative Example 3> The basic configuration and materials were the same as in Example 1, but the activation voltage range of the break-in conditions was changed to 0.50V to 1.70V.

[0039] An example of the results of measuring the actual battery capacity is shown in Figure 2. Compared to Comparative Example 1, Example 1 showed an improvement in the actual battery capacity.

[0040] Table 1 shows a comparison of the actual battery capacity measurements. [Table 1]

[0041] The battery capacity of Example 1 increased by 12% compared to Comparative Example 1. This suggests that by performing charge-discharge cycles with the lower limit potential lowered to 0 V, a reduction-oxidation reaction occurred within the negative electrode active material, driving and spreading the electrolyte, thereby increasing the effective reaction area of ​​the surface of the negative electrode active material involved in the reaction. Therefore, it is believed that the range within the electrode that the electrolyte can reach was maximized.

[0042] By comparing the results of Comparative Examples 1, 2, and 3 with Example 1, it is clear that bringing the lower limit of the activation voltage of the break-in conditions closer to 0 V has a significant effect on the actual battery capacity.

[0043] 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]

[0044] 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 method for manufacturing a secondary battery, The secondary battery is a positive electrode having a positive electrode active material containing at least one of nickel hydroxide and manganese oxide; a negative electrode including a negative electrode current collector on which a negative electrode active material containing porous carbon is formed, an initial charge / discharge step of activating the secondary battery after the secondary battery assembly step; In the initial charge / discharge step, the battery is discharged to 0 to 0.1 V at least twice. A method for manufacturing a 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 method for manufacturing the secondary battery according to claim 1 .

3. The porous carbon is 500 m ２ / g to 5000m ２ / g specific surface area, The porous carbon has a chemical functional group on a part of its surface. The method for manufacturing the secondary battery according to claim 1 .

4. the chemical functional group is a hydroxyl group or a carboxyl group; The method for manufacturing a secondary battery according to claim 3 .

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