Active material slurry including a lead-carbon composite and manufacturing method thereof

Abstract

The present invention relates to an electrode active material slurry comprising a lead-carbon composite for improving the performance of an asymmetric hybrid battery, and more specifically, to an electrode active material slurry comprising a lead-carbon composite comprising a carbon material, a conductive material and lead powder, a binder and a diluent, wherein the content of the binder is controlled to minimize the generation of irreversible lead sulfate (PbSO4) and hydrogen gas (H2) in a lead-acid battery, thereby having the effect of not causing performance degradation, and a method for manufacturing the same.

Description

Technology Field

[0001] The present invention relates to an electrode active material slurry comprising a lead-carbon composite for improving the performance of an asymmetric hybrid battery and a method for manufacturing the same. Background Technology

[0002] Energy Storage System (ESS) batteries are a technology that stores generated electrical energy and can be used in emergencies. It is a collective term for devices and solutions used to expand the introduction of new energy, improve energy efficiency, and stabilize power supply systems, and is receiving attention as an important technology that will lead the global energy market in the future.

[0003] Lead-acid batteries are characterized by their relatively low cost, simple manufacturing process, and technical stability, and their applications are diverse, including automobiles, HEVs (Hybrid Electric Vehicles), energy storage systems, UPS (Uninterruptible Power Supplies), and telecommunications.

[0004] The negative and positive electrodes of a lead-acid battery are composed of lead, and the sulfuric acid electrolyte provides electrical conductivity; the sulfuric acid induces electrical interactions within the battery and plays a role in storing electrical energy.

[0005] The total chemical reaction of a lead-acid battery is Pb(s) + PbO2(s) + 2HS4 - (aq) → 2PbSO4(s) + 2H + It can be expressed as (aq) + 2H2O(l), and the primary purpose is to obtain the electromotive force generated as lead (Pb) becomes lead sulfate (PbSO4). This reaction is mutually reversible, and if electricity is supplied again, lead sulfate (PbSO4) can be recycled back into lead (Pb), and this is called a 'rechargeable battery' or 'secondary battery' (hereinafter referred to as a 'lead-acid battery').

[0006] The problems associated with such lead-acid batteries include relatively low energy density compared to other batteries such as lithium-ion and nickel-hydrogen batteries, difficulty in weight reduction, and loss of output and cycle performance caused by irreversible lead sulfate (PbSO4) crystals formed at the negative electrode during the discharge process.

[0007] Furthermore, hydrogen gas (H2) is generated as a byproduct during the charging and discharging process of lead-acid batteries. This hydrogen gas, along with the evaporation of the electrolyte—a significant issue in lead-acid batteries—significantly affects the stability and lifespan of the battery. Moreover, this has emerged as an even greater problem in actual operating environments due to the influence of various external factors such as high heat and vibration, and technology is required to address this issue. Prior art literature

[0008] Korean Registered Patent No. 10-2497879 (February 6, 2023) The problem to be solved

[0009] The present invention aims to provide an electrode active material slurry for improving the performance of an asymmetric hybrid battery and a lead-acid battery using the same, which minimizes the generation of irreversible lead sulfate (PbSO4) and hydrogen gas (H2) by controlling the binder content when preparing an electrode active material slurry containing a lead-carbon composite for surface coating of a negative electrode plate composed of lead (Pb) among the components of a conventional lead-acid battery, thereby solving the problems of the conventional technology described above. means of solving the problem

[0010] The electrode active material slurry of the present invention for achieving the above objective comprises a carbon material, a lead-carbon composite including a conductive material and lead powder, a binder, and a diluent, wherein the binder is included in an amount of 5% to 10% by weight relative to 100% by weight of the total electrode active material slurry.

[0011] In the electrode active material slurry of the present invention, the carbon material may be one or more selected from glass carbon, graphite, carbon nanopowder, and activated carbon, and the activated carbon may be one or more selected from commercial products such as BA21E, BS7, CA31, CEP21K, CEP21KS, and CEP21KSN.

[0012] In the electrode active material slurry of the present invention, the conductive material may be one or more selected from carbon black and graphite.

[0013] In the electrode active material slurry of the present invention, the binder may be any one selected from polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and polytetrafluoroethylene (PTFE).

[0014] In the electrode active material slurry of the present invention, the diluent may be one or more selected from distilled water, ethanol, and isopropyl alcohol (IPA).

[0015] In addition, to achieve the above objectives, the method for preparing an electrode active material slurry according to the present invention may include the steps of: preparing a lead-carbon composite by mixing a carbon material, a conductive material, and lead powder; and preparing an electrode active material slurry by adding a binder and a diluent to the lead-carbon composite and mixing them.

[0016] At this time, the binder may be included in an amount of 5% to 10% by weight relative to 100% by weight of the total electrode active material slurry.

[0017] In the method for preparing an electrode active material slurry of the present invention, the step of preparing the lead-carbon composite and the step of preparing the electrode active material slurry may be mixed at 100 rpm to 500 rpm for 12 hours to 24 hours. Effects of the invention

[0018] The electrode active material slurry containing the lead-carbon composite of the present invention has the effect of minimizing the generation of irreversible lead sulfate (PbSO4) and hydrogen gas (H2) in a lead-acid battery.

[0019] In addition, the electrode active material slurry comprising a lead-carbon composite according to the present invention can be easily applied to the manufacture of energy storage systems (ESS), particularly secondary batteries for industrial, household, and automotive use, thereby improving their electrochemical performance. Brief explanation of the drawing

[0020] Figure 1 is a scanning electron microscope (SEM) image of a carbon material candidate group. Figure 2 shows data measured by Linear Sweep Voltametry (LSV) for each carbon material candidate group. Figure 3 shows data measured by cyclic voltammetry (CV) for each carbon material candidate group. Figures 4 to 7 are time-voltage graphs of electrode active material slurries according to binder content. Specific details for implementing the invention

[0021] Terms such as “composed” or “comprising” used in the specification should not be interpreted as necessarily including all of the various components described in the specification, and should be interpreted as meaning that some of the components may not be included and additional components may be included.

[0022] The present invention will be described below with reference to the illustrated drawings. However, this is merely a reference for the detailed explanation of the invention and the invention is not limited thereto; various modifications and applications are possible within the scope of the invention based on the description below.

[0023] FIG. 1 is a scanning electron microscope (SEM) image of a group of carbon material candidates, and FIG. 1 (a) to (f) are, in order, commercial products glassy carbon, graphite, carbon nano powder, carbon nano fiber, activated carbon, and activated charcoal, and FIG. 1 (g) to (l) are, in order, commercial products of activated carbon (POWERCARBONTECHNOLOGY) BA21E, BS7, CA31, CEP21K, CEP21KS, and CEP21KSN.

[0024] As shown in Fig. 1, the particle shape and particle size of the carbon material can be roughly confirmed through a scanning electron microscope (SEM), and

[0025] Among carbon materials with a particle size of approximately 5 to 10 µm, the remaining carbon materials can be used, excluding activated charcoal with a large particle size and carbon nanofibers with a shape unsuitable for use as coating materials. Among these, activated carbon with a high specific surface area can be utilized.

[0026] Carbon materials can be mixed and used as needed. In the case of activated carbon with a relatively high specific surface area, it can be mixed with carbon materials that have a low specific surface area or high overpotential to suppress hydrogen gas generation.

[0027] Linear Sweep Voltametry (LSV) was measured as shown in Figure 2 to identify a carbon material suitable for suppressing hydrogen generation when a mixture of carbon materials is used.

[0028] Figure 2 shows data measured by Linear Sweep Voltametry (LSV) for each carbon material candidate group.

[0029] Linear Sweep Voltametry (LSV) can verify the overpotential characteristics required for the hydrogen evolution reaction of candidate substances. Here, "potential" refers to voltage, and it was calculated based on the reversible hydrogen electrode (RHE). It can be said that hydrogen evolution is suppressed if the voltage is lower (based on the hydrogen evolution reaction) at the same current density.

[0030] Materials with high hydrogen evolution reaction (HER) overpotential can be used preferentially. However, since high overpotential does not necessarily mean that the charge and discharge efficiency of a lead-acid battery will increase, activated carbon, which has a high specific surface area, can be mixed and used.

[0031] Figure 3 shows data measured by cyclic voltammetry (CV) for each carbon material candidate group, and reveals the electrochemical reactivity and capacitor performance for each carbon material candidate group. In the cyclic voltammetry (CV) graph, the voltage was calculated based on lead oxide (PbO2), and the charge / discharge performance and overvoltage can be checked simultaneously.

[0032] As shown in Figures 3 (b) and (c), it can be seen that activated carbon exhibits mostly similar levels of electrochemical characteristics and that the amount of oxidation and reduction varies, which allows for the indirect verification of charge and discharge capacity. Additionally, activated carbon can be used in combination with materials such as glassy carbon, which has a relatively low level of hydrogen generation.

[0033] Based on these results, the carbon material used in the electrode active material slurry of the present invention may be one or more selected from glass carbon, graphite, carbon nanopowder, and activated carbon, and the activated carbon may be one or more selected from commercial products such as BA21E, BS7, CA31, CEP21K, CEP21KS, and CEP21KSN.

[0034] The electrode active material slurry of the present invention comprises a carbon material, a conductive material, lead powder, a binder, and a diluent.

[0035] The above conductive material is one or more selected from carbon black and graphite.

[0036] The above binder is used to attach a carbon material to a cathode plate, and the binder is used by mixing one or more selected from polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and polytetrafluoroethylene (PTFE) with methylpyrrolidone (NMP) and deionized water (DI water), or by using it alone.

[0037] The above diluent controls the viscosity so that the electrode active material slurry is well coated onto the lead-acid battery electrode plate, and uses one selected from distilled water, ethanol, and isopropyl alcohol (IPA).

[0038] In order to determine the optimal content of the binder included in the electrode active material slurry, a charging performance experiment was performed on a lead-acid battery with electrode active material slurry according to the binder content.

[0039] The electrode active material slurry for the charging performance test of a lead-acid battery is prepared by the following method.

[0040] Considering electrochemical reactivity, conductivity, and hydrogen evolution reaction, activated carbon as a carbon material, graphite as a conductive material, and lead powder are mixed in a ball mill process at 350 rpm for 24 hours to obtain a lead-carbon composite. An electrode active material slurry is prepared by adding a binder and a diluent to the lead-carbon composite. Here, the binder content is added differently at 5 wt%, 10 wt%, and 15 wt% relative to 100 wt% of the total electrode active material slurry, respectively, and mixed with the lead-carbon composite to prepare a final electrode active material slurry.

[0041] The above electrode active material slurry is evenly applied to a lead (Pb) electrode plate obtained from a commercial battery. At this time, the application method of the slurry may be any one selected from a brush method, a roller method, a spray method, a spin coating method, and an immersion coating method, but is not necessarily limited thereto.

[0042] Each electrode plate coated with an electrode active material slurry is completely dried by heat treatment in an oven at a temperature of 40°C to 60°C for 24 to 48 hours to manufacture an electrode active material slurry coated electrode (PbC).

[0043] In a battery for evaluating charge / discharge performance, the negative electrode uses an electrode active material slurry coated electrode (PbC) with an electrode slurry according to the above binder content, the positive electrode uses a positive plate used in commercial batteries, the separator between the negative electrode and the positive electrode uses an AGM (absorbed glass mat) separator used in commercial batteries identical to the positive electrode, and the electrolyte uses directly manufactured sulfuric acid with a specific gravity of 1.280. At this time, the control cell (Pb cell) uses a negative electrode plate (Pb electrode plate) used in commercial batteries without an electrode active material slurry applied.

[0044] The battery configured in this way is evaluated for charge and discharge performance at three C-rates (Current-rates) at room temperature (20°C to 25°C). Discharge is performed using the constant current (CC) method at 0.2 C-rate, 0.5 C-rate, and 1 C-rate, and charge is performed using the constant current constant voltage (CCCV) method at a limiting voltage of 2.4 V and a set current of 0.2 A to evaluate charge and discharge performance by charging 1 Ah. The results are shown in FIGS. 4 to 7.

[0045] Figures 4 to 7 are time-voltage graphs evaluating the charge-discharge performance of lead-acid batteries with electrode active material slurries applied according to binder content.

[0046] FIG. 4 is a time-voltage graph evaluating the charge-discharge performance of a control group (Pb cell), FIG. 5 is a time-voltage graph evaluating the charge-discharge performance of a lead-acid battery (hereinafter also referred to as '5 wt% PbC') with an electrode active material slurry with a binder content of 5 wt%, FIG. 6 is a time-voltage graph evaluating the charge-discharge performance of a lead-acid battery (hereinafter also referred to as '10 wt% PbC') with an electrode active material slurry with a binder content of 10 wt%, and FIG. 7 is a time-voltage graph evaluating the charge-discharge performance of a lead-acid battery (hereinafter also referred to as '15 wt% PbC') with an electrode active material slurry with a binder content of 15 wt%.

[0047] In addition, in FIGS. 4 to 7, (a) shows a change in discharge voltage and (b) shows a change in charge voltage. Discharge performance can be evaluated based on changes in charge and discharge voltage over time, and the smaller the slope of the decrease in charge and discharge voltage, the better the charge and discharge characteristics. During discharge, the voltage drops, and during charge, the voltage rises.

[0048] As shown in FIGS. 4 to 7, when the capacity test of the lead-acid battery was conducted for 10 hours, the lead-acid batteries with electrode active material slurries applied with binder content of 5 wt% and 10 wt%, namely 5 wt% PbC and 10 wt% PbC, had a discharge capacity of 1 Ah, the same as the control group (Pb cell).

[0049] In particular, in the case of 10 wt% PbC, when discharged by the above method, the time taken to reach the discharge end voltage of 1.8V increases by about 17%, exhibiting stable discharge characteristics.

[0050] In contrast, the discharge capacity of 15 wt% PbC was reduced by about 45% to 50% compared to the control group (Pb cell). It is believed that when the binder content exceeds an appropriate level, it interferes with charge transfer and storage during the chemical reactions occurring during the charging and discharging process, thereby degrading performance.

[0051] As a result of the charging performance evaluation, it takes about 5 hours (18,000 seconds) for 10 wt% PbC to reach 1Ah when charging at a low rate (0.2C-rate). This represents an increase in charging speed of about 14% compared to the control group (Pb cell), which takes about 5 hours and 20 minutes (21,000 seconds), and 5 wt% PbC.

[0052] It was confirmed that 10 wt% PbC improved discharge stability at low rate (0.2 C-rate) and high rate (1 C-rate) discharges, and improved charging performance at low rate compared to other lead-acid batteries.

[0053] Table 1 below shows the charge / discharge current efficiency and charge / discharge power efficiency figures for lead-acid batteries with electrode active material slurries applied according to binder content.

[0054] division Control group (Pb cell) 5 wt% PbC 10 wt% PbC 15 wt% PbC Charge / Discharge Current Efficiency 98.1% 100% 100% 95% Charge / Discharge Power Efficiency 88.6% 90.8% 91.2% 84%

[0055] As shown in Table 1 above, it was confirmed that the charge / discharge current efficiency and charge / discharge power efficiency were the best in the 10 wt% PbC battery, which is a battery with an electrode active material slurry with a binder content of 10 wt%. The current efficiency was close to 100%, which is within the normal range, and while the power efficiency increases from the control group up to 10 wt% PbC, it drops sharply in the 15 wt% PbC battery, which is a battery with an electrode active material slurry with a binder content of 15 wt%.

[0056] As previously described, the present invention minimizes the generation of irreversible lead sulfate (PbSO4) and hydrogen gas (H2) when preparing an electrode expansion material slurry containing a lead-carbon composite on the surface of a negative electrode plate composed of lead (Pb) among the components of a lead-acid battery by appropriately controlling the binder content.

Claims

Claim 1 delete Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 delete Claim 6 delete Claim 7 A method for preparing an electrode active material slurry, comprising: a step of preparing a lead-carbon composite by mixing a carbon material, a conductive material, and lead powder; and a step of preparing an electrode active material slurry by adding and mixing a binder and a diluent to the lead-carbon composite, wherein the binder is included in an amount of 5% to 10% by weight relative to 100% by weight of the total electrode active material slurry. Claim 8 delete Claim 9 A method for preparing an electrode active material slurry according to claim 7, wherein the step of preparing the lead-carbon composite and the step of preparing the electrode active material slurry are mixed at 100 rpm to 500 rpm for 12 hours to 24 hours. Claim 10 A method for preparing an electrode active material slurry according to claim 7, characterized in that the carbon material is one or more selected from glass carbon, graphite, carbon nanopowder, and activated carbon. Claim 11 delete Claim 12 A method for preparing an electrode active material slurry according to claim 7, characterized in that the conductive material is one or more selected from carbon black and graphite. Claim 13 A method for preparing an electrode active material slurry according to claim 7, wherein the binder is selected from polyvinylidene fluoride (PVDF), styrene-butadiene rubber (SBR), and polytetrafluoroethylene (PTFE). Claim 14 A method for preparing an electrode active material slurry according to claim 7, characterized in that the diluent is one or more selected from distilled water, ethanol, and isopropyl alcohol (IPA).

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