A lead-acid starting battery for automobiles with a carbon-coated negative electrode separator and its preparation method

Abstract

This invention discloses a lead-acid automotive starting battery with a carbon-coated negative electrode separator and its preparation method, belonging to the field of automotive lead-acid battery technology. By applying a conductive carbon material coating to the surface of the separator, the separator is tightly attached to the negative electrode active material, forming a porous conductive layer that balances conductivity and porosity. During charging, this effectively guides electron conduction and uniformly distributes the electrolyte, solving the problems of sulfate precipitation and reduced charge acceptance in traditional lead-acid batteries at low charging rates or in partially charged states, thus improving the battery's charging efficiency and cycle life.

Description

Technical Field

[0001] This invention relates to the field of lead-acid battery technology, specifically to a lead-acid battery for automotive starting systems, and more particularly to a lead-acid battery with a conductive carbon coating on the surface of the negative electrode separator to improve the overall performance of the battery and its preparation method. Background Technology

[0002] Lead-acid batteries, as a mature energy storage device, are widely used in automotive starting, backup power, and energy storage systems due to their advantages such as low cost, mature manufacturing process, and high reliability. Among them, valve-regulated lead-acid batteries (VRLA) have seen widespread application in recent years due to their maintenance-free nature and good sealing performance.

[0003] However, with the increasing prevalence of start-stop systems in automobiles and the rising performance requirements for energy storage systems, traditional lead-acid batteries have revealed some technical bottlenecks in practical applications. Particularly under frequent start-stop cycles and partial state of charge (PSoC) conditions, batteries are prone to negative electrode sulfation, leading to decreased charge acceptance, increased internal resistance, and accelerated capacity decay, thereby shortening battery lifespan.

[0004] To address these issues, researchers have attempted to improve battery performance by optimizing electrode materials, refining electrolyte formulations, and adjusting plate structures. For example, high-surface-area activated carbon materials are used as additives (e.g., patent publication number JP2002367613A) to enhance electrode conductivity and electrochemical activity; or additives are added to the electrolyte (e.g., patent publication number CN119852555A) to improve its conductivity and stability. However, these methods still have limitations in practical applications, such as high material costs, complex processes, and poor long-term stability.

[0005] In recent years, some studies have proposed applying a conductive carbon material coating, such as activated carbon or graphite, to the surface of the negative electrode separator to form a porous conductive layer, enhance electron conductivity, and improve the uniformity of electrolyte distribution. This method can improve the battery's charge acceptance and cycle life to some extent, but further optimization of the coating's composition, structure, and process parameters is still needed to achieve even better performance improvements.

[0006] Therefore, there is an urgent need to develop a lead-acid battery structure that is simple in structure, low in cost, and has excellent performance, so as to effectively improve the battery's charge acceptance capacity in a partially charged state, extend the battery's service life, and meet the higher requirements of modern automotive start-stop systems and energy storage systems for battery performance. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and propose an automotive starting lead-acid battery with a carbon-coated negative electrode separator and its preparation method. By applying a conductive carbon material coating to the surface of the separator, the separator is made to adhere closely to the negative electrode active material, forming a porous conductive layer that balances conductivity and porosity, effectively guides electron conduction and uniformly distributes the electrolyte, thereby improving the battery's charging efficiency and cycle life.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a lead-acid battery for automobile starting with a carbon-coated negative electrode separator, comprising a positive electrode plate, a negative electrode plate, a separator disposed therebetween, and an electrolyte. The improvement lies in that at least the surface of the separator facing the negative electrode plate is provided with a conductive carbon coating.

[0010] The conductive carbon layer comprises the following components by weight: 30-60 parts graphite, 20-40 parts activated carbon, 10-30 parts acetylene black, 5-15 parts binder, 0.005-0.05 parts titanium carbide (MXene), and 0.003-0.06 parts vanadium carbide.

[0011] Preferably, the conductive carbon coating has a porosity of 30%-50% to ensure uniform distribution of the electrolyte and effective electron conduction, and a specific surface area of ​​100-300 m². 2 / g, with an electrical conductivity of 10-100 S / cm.

[0012] Furthermore, the thickness of the conductive carbon coating is 0.1-0.2 mm, and the coating amount is 0.5%-1.5% of the mass of the negative electrode lead paste.

[0013] Furthermore, the adhesive is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

[0014] Furthermore, the partition is a glass fiber partition to enhance its mechanical strength and corrosion resistance;

[0015] The electrolyte has a density of 1.28 g / cm³. 3 A sulfuric acid solution containing 0.5% phosphoric acid by mass;

[0016] The active material of the negative electrode plate contains 0.2% stannous sulfate by mass.

[0017] The positive electrode plate uses a high-tin-calcium alloy grid, wherein the tin content is 1.5%-1.7%.

[0018] Secondly, the present invention also provides a method for preparing the aforementioned automotive starting lead-acid battery, the key of which lies in the step of preparing a porous conductive carbon layer on the surface of the negative electrode separator, the step comprising:

[0019] Graphite, activated carbon, acetylene black, titanium carbide, and vanadium carbide are mixed evenly in proportion, and then a binder and solvent are added and mixed to prepare a uniform slurry.

[0020] The slurry is applied to the surface of the partition plate by scraping, dipping, or spraying.

[0021] After drying, the porous conductive carbon layer is formed.

[0022] Carbon materials are bonded to the surface of the separator through an adhesive to form a porous conductive carbon layer.

[0023] Further, the solvent is N-methylpyrrolidone or water, and during preparation, 80-125 parts of solvent are added by weight.

[0024] Furthermore, the final battery assembly and formation yields the automotive starting lead-acid battery. During the battery formation stage, a stepped charging system is adopted: first, it is charged at a constant current of 0.15C to 2.4V / cell, and then charged at a constant current of 0.08C until the current drops to 0.02C.

[0025] Furthermore, the drying conditions are: drying at 60-80℃ for 1-2 hours.

[0026] The reaction mechanism of this invention:

[0027] This invention improves battery performance synergistically in two ways by introducing a conductive carbon coating with specific components and structure:

[0028] Enhanced Conductive Network: MXene, with its high conductivity and two-dimensional layered structure, forms a continuous conductive network with graphite, acetylene black, and other materials. Vanadium carbide fills the gaps in the network, reducing the coating's bulk resistance. During battery charging and discharging, electrons are rapidly transferred, reducing energy loss and improving electrochemical reaction efficiency.

[0029] Suppressing negative electrode sulfation: Vanadium carbide surface defect sites on Pb 2+ Ions have an adsorption effect, altering the growth direction of lead sulfate crystals and promoting the formation of fine, uniform lead sulfate crystals. MXene accelerates the growth of Pb... 2+ Migration further inhibits the formation of coarse lead sulfate crystals, delays sulfation of the negative electrode plate, and extends battery life.

[0030] The beneficial effects of this invention are:

[0031] 1) The porous conductive layer provides abundant electron conduction paths, reduces the resistance to electron transport, promotes the rapid movement of charges, and enables electrons to be conducted to the negative electrode active material more quickly during charging, thereby improving the battery's charge acceptance capability.

[0032] 2) The high conductivity of conductive carbon materials reduces the resistance to electron transport in the electrodes, thereby reducing the overall internal resistance of the battery and improving its energy efficiency.

[0033] 3) The carbon coating on the negative electrode separator forms a highly conductive porous network, which optimizes the conduction efficiency of electrons from the active material to the main circuit, effectively reduces the resistance to low-temperature discharge, and significantly increases the cold start current.

[0034] 4) The carbon coating reduces sulfate deposition at the negative electrode, lowers the risk of micro-short circuits, stabilizes the electrochemical structure, and the barrier-like effect of the carbon coating effectively reduces the self-discharge rate. The high-porosity carbon coating improves gas diffusion channels, preventing hydrogen evolution from accumulating on the electrode surface, thereby delaying and reducing the hydrogen escape rate. Detailed Implementation

[0035] To make the technical problem to be solved, the technical solution, and the beneficial effects of the present invention clearer, the following embodiments are provided to further illustrate the present invention in detail. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0036] The performance testing method used in this invention:

[0037] 1) Cold start performance (-18℃, CCA)

[0038] Test conditions: The battery was frozen to -18°C in a constant temperature chamber and kept there for at least 4 hours to allow the battery to reach thermal equilibrium inside and outside.

[0039] Test method: According to SAE J537 / J300 standards, a constant load is applied to the battery at -18℃ to reduce its current to the CCA rating, and the voltage is checked to see if it remains ≥7.2V within 30 seconds. The maximum discharge current is recorded as the actual CCA.

[0040] 2) Charging acceptance capability (0.2C)

[0041] Test conditions: room temperature (20-25℃), the battery is first discharged at 0.1C to the cutoff voltage (about 10.5V), and then left to stand for 1 hour.

[0042] Test method: Charge at a constant current of 0.2C to 14.4V (±0.1V), then switch to constant voltage charging until the current drops to C / 100 (approximately 1% of the battery capacity). Calculate the recovered capacity (charge amount / discharge amount × 100%), which is the charging acceptance capability.

[0043] 3) Self-discharge rate (25℃, 30 days)

[0044] Test conditions: Charge the battery to full capacity (open circuit voltage approximately 12.6±0.05V), place it in a 25℃ environment for 30 days, and avoid load interference.

[0045] Test method: Record the open circuit voltage before and after storage and measure the capacity change by discharging with constant current. Calculate the self-discharge rate: (initial capacity - remaining capacity) / initial capacity × 100%.

[0046] 4) Internal resistance (mΩ)

[0047] Test conditions: room temperature 25℃, battery fully charged and left to stand for 30 minutes to restore thermal equilibrium.

[0048] Test method: Use an AC impedance meter (EIS) to measure the voltage and current response at a frequency of 1kHz and calculate the internal resistance.

[0049] Example 1

[0050] 1. Conductive carbon material coating formula: 30g graphite, 20g activated carbon, 10g acetylene black, 5g polytetrafluoroethylene (PTFE) binder, 80g N-methylpyrrolidone (NMP) solvent, 0.005g titanium carbide, and 0.003g vanadium carbide.

[0051] 2. Preparation of conductive carbon material coating:

[0052] Graphite, activated carbon, and acetylene black were mixed evenly, and then binder and solvent were added and stirred to form a homogeneous slurry. The slurry was then uniformly coated onto the surface of a fiberglass partition using a scraping method. After drying at 60°C for 1 hour, a porous conductive layer with a thickness of 0.1 mm was formed, with a coating weight of 0.5% of the lead paste mass. The porosity of this coating was measured to be 30%, and the specific surface area was 100 m². 2 / g, conductivity 10S / cm.

[0053] 3. Battery assembly and formation:

[0054] The positive electrode uses a high-tin-calcium alloy grid with a tin content of 1.6%; the negative electrode lead paste contains 0.2 wt% stannous sulfate. The electrolyte has a density of 1.28 g / cm³. 3 An H2SO4 solution containing 0.5 wt% phosphoric acid was prepared. A separator coated with a conductive coating was placed between the positive and negative electrodes, with the coating facing the negative electrode.

[0055] A stepped charging method was used: first, the voltage was charged at 0.15C to 2.4V per cell, and then at 0.08C until the current dropped to 0.02C. The test results are shown in Table 1.

[0056] Table 1 Test Results of Example 1

[0057]

[0058] Example 2

[0059] 1. Conductive carbon material coating formula: Graphite 38g, activated carbon 25g, acetylene black 15g, polyvinylidene fluoride (PVDF) binder 8g, N-methylpyrrolidone (NMP) solvent 95g, titanium carbide 0.015g, vanadium carbide 0.02g.

[0060] 2. Preparation of conductive carbon material coating:

[0061] Graphite, activated carbon, and acetylene black were mixed evenly, and then a binder and solvent were added and stirred to form a homogeneous slurry. The slurry was then uniformly coated onto the surface of a fiberglass partition using a dip-coating method. After drying at 65°C for 1.2 hours, a porous conductive layer with a thickness of 0.13 mm was formed, with a coating weight of 0.8% of the lead paste mass. The porosity of this coating was measured to be 35%, and the specific surface area was 150 m². 2 / g, conductivity 30S / cm.

[0062] 3. Battery assembly and formation:

[0063] The positive electrode uses a high-tin-calcium alloy grid with a tin content of 1.6%; the negative electrode lead paste contains 0.2 wt% stannous sulfate. The electrolyte has a density of 1.31 g / cm³. 3 An H2SO4 solution containing 0.6 wt% phosphoric acid was prepared. A separator coated with a conductive coating was placed between the positive and negative electrodes, with the coating facing the negative electrode.

[0064] A stepped charging method was used: first, the voltage was charged at 0.15C to 2.4V per cell, and then at 0.08C until the current dropped to 0.02C. The test results are shown in Table 2.

[0065] Table 2 Test Results of Example 2

[0066]

[0067] Example 3

[0068] 1. Conductive carbon material coating formula: 50g graphite, 35g activated carbon, 25g acetylene black, 12g binder made of sodium carboxymethyl cellulose (CMC) and styrene-butadiene rubber (SBR) in a 1:1 ratio, 115g deionized water, 0.04g titanium carbide, and 0.05g vanadium carbide.

[0069] 2. Preparation of conductive carbon material coating:

[0070] Graphite, activated carbon, and acetylene black were mixed evenly, and then binder and solvent were added and stirred to form a homogeneous slurry. The slurry was then evenly coated onto the surface of a fiberglass partition using a spraying method. After drying at 75°C for 1.8 hours, a porous conductive layer with a thickness of 0.18 mm was formed, with a coating weight of 1.2% of the lead paste mass. The porosity of this coating was measured to be 45%, and the specific surface area was 260 m². 2 / g, conductivity 80S / cm.

[0071] 3. Battery assembly and formation:

[0072] The positive electrode uses a high-tin-calcium alloy grid with a tin content of 1.6%; the negative electrode lead paste contains 0.2 wt% stannous sulfate. The electrolyte has a density of 1.31 g / cm³. 3 An H2SO4 solution containing 0.7 wt% phosphoric acid was prepared. A separator coated with a conductive coating was placed between the positive and negative electrodes, with the coating facing the negative electrode.

[0073] A stepped charging method was used: first, the voltage was charged at 0.15C to 2.4V per cell, and then at 0.08C until the current dropped to 0.02C. The test results are shown in Table 3.

[0074] Table 3 Test Results of Example 3

[0075]

[0076] Example 4

[0077] 1. Conductive carbon material coating formula: 60g graphite, 40g activated carbon, 30g acetylene black, 15g styrene-butadiene rubber (SBR) binder, 125g deionized water, 0.05g titanium carbide, and 0.06g vanadium carbide.

[0078] 2. Preparation of conductive carbon material coating:

[0079] Graphite, activated carbon, and acetylene black were mixed evenly, and then binder and solvent were added and stirred to form a homogeneous slurry. The slurry was then evenly coated onto the surface of a fiberglass partition using a spraying method. After drying at 80℃ for 2 hours, a porous conductive layer with a thickness of 0.2 mm was formed, with a coating weight of 1.5% of the lead paste mass. The porosity of this coating was measured to be 50%, and the specific surface area was 300 m². 2 / g, conductivity 100S / cm.

[0080] 3. Battery assembly and formation:

[0081] The positive electrode uses a high-tin-calcium alloy grid with a tin content of 1.6%; the negative electrode lead paste contains 0.2 wt% stannous sulfate. The electrolyte has a density of 1.33 g / cm³. 3An H2SO4 solution containing 0.8 wt% phosphoric acid was used. A separator coated with a conductive coating was placed between the positive and negative electrodes, with the coating facing the negative electrode.

[0082] A stepped charging method was used: first, the voltage was charged at 0.15C to 2.4V per cell, and then at 0.08C until the current dropped to 0.02C. The test results are shown in Table 4.

[0083] Table 4 Test Results of Example 4

[0084]

[0085] Comparative Example 1

[0086] 1. Conductive carbon material coating formula: 30g graphite, 20g activated carbon, 10g acetylene black, 5g polytetrafluoroethylene (PTFE) binder, 80g N-methylpyrrolidone (NMP) solvent, and 0.003g vanadium carbide.

[0087] 2. Preparation of conductive carbon material coating:

[0088] Graphite, activated carbon, and acetylene black were mixed evenly, and then binder and solvent were added and stirred to form a homogeneous slurry. The slurry was then uniformly coated onto the surface of a fiberglass partition using a scraping method. After drying at 60°C for 1 hour, a porous conductive layer with a thickness of 0.1 mm was formed, with a coating weight of 0.5% of the lead paste mass. The porosity of this coating was measured to be 30%, and the specific surface area was 100 m². 2 / g, conductivity 10S / cm.

[0089] 3. Battery assembly and formation:

[0090] The positive electrode uses a high-tin-calcium alloy grid with a tin content of 1.6%; the negative electrode lead paste contains 0.2 wt% stannous sulfate. The electrolyte has a density of 1.28 g / cm³. 3 An H2SO4 solution containing 0.5 wt% phosphoric acid was prepared. A separator coated with a conductive coating was placed between the positive and negative electrodes, with the coating facing the negative electrode.

[0091] A stepped charging method was used: first, the voltage was charged at 0.15C to 2.4V per cell, and then at 0.08C until the current dropped to 0.02C. The test results are shown in Table 5.

[0092] Table 5. Test results of Comparative Example 1

[0093]

[0094] Comparative Example 2

[0095] 1. Conductive carbon material coating formula: 30g graphite, 20g activated carbon, 10g acetylene black, 5g polytetrafluoroethylene (PTFE) binder, 80g N-methylpyrrolidone (NMP) solvent, and 0.005g titanium carbide.

[0096] 2. Preparation of conductive carbon material coating:

[0097] Graphite, activated carbon, and acetylene black were mixed evenly, and then binder and solvent were added and stirred to form a homogeneous slurry. The slurry was then uniformly coated onto the surface of a fiberglass partition using a scraping method. After drying at 60°C for 1 hour, a porous conductive layer with a thickness of 0.1 mm was formed, with a coating weight of 0.5% of the lead paste mass. The porosity of this coating was measured to be 30%, and the specific surface area was 100 m². 2 / g, conductivity 10S / cm.

[0098] 3. Battery assembly and formation:

[0099] The positive electrode uses a high-tin-calcium alloy grid with a tin content of 1.6%; the negative electrode lead paste contains 0.2 wt% stannous sulfate. The electrolyte has a density of 1.28 g / cm³. 3 An H2SO4 solution containing 0.5 wt% phosphoric acid was prepared. A separator coated with a conductive coating was placed between the positive and negative electrodes, with the coating facing the negative electrode.

[0100] A stepped charging method was used: first, the voltage was charged at 0.15C to 2.4V per cell, and then at 0.08C until the current dropped to 0.02C. The test results are shown in Table 6.

[0101] Table 6. Test results of Comparative Example 2

[0102]

[0103] By comparing the test data of Examples 1-4 with those of Comparative Examples 1-2 in Tables 1-6 above, it can be seen that:

[0104] On the one hand, the batteries of the embodiments of the present invention are significantly superior to the comparative examples in terms of cold start current, charge acceptance, internal resistance, and self-discharge rate. Furthermore, the performance of both Comparative Example 1 (without titanium carbide) and Comparative Example 2 (without vanadium carbide) shows a decline, indicating that titanium carbide and vanadium carbide play an indispensable synergistic role in the coating. Titanium carbide mainly contributes to building a highly conductive network to reduce internal resistance and improve CCA; vanadium carbide focuses on suppressing sulfation, improving charge acceptance, and cycle stability. The performance improvement is most significant when both are present. Finally, with a moderate increase in the content of functional components (titanium carbide, vanadium carbide) in the coating and optimization of the coating structure (such as in Examples 3 and 4), the overall performance of the battery shows a further improvement trend.

[0105] In summary, this invention effectively improves the low-temperature start-up capability and charging efficiency of lead-acid batteries by setting a conductive carbon coating containing a specific proportion of graphite, activated carbon, acetylene black, titanium carbide and vanadium carbide on the surface of the negative electrode separator, and reduces internal resistance and self-discharge, thus having significant industrial application value.

Claims

1. A lead-acid starting battery for automobiles with a carbon-coated negative electrode separator, comprising a positive electrode plate, a negative electrode plate, a separator disposed therebetween, and an electrolyte, characterized in that, The separator is a glass fiber separator, and a conductive carbon coating is provided on one side of the separator facing the negative electrode plate. The conductive carbon coating comprises the following components by weight: 30-60 parts graphite, 20-40 parts activated carbon, 10-30 parts acetylene black, 5-15 parts binder, 0.005-0.05 parts titanium carbide, and 0.003-0.06 parts vanadium carbide. The conductive carbon coating has a porosity of 30%-50% and a specific surface area of ​​100-300 m². 2 / g; The conductive carbon coating has a thickness of 0.1-0.2 mm and a coating amount of 0.5%-1.5% of the mass of the negative electrode lead paste. The electrolyte has a density of 1.28 g / cm³. 3 A sulfuric acid solution containing 0.5% phosphoric acid by mass; The active material of the negative electrode plate contains 0.2% stannous sulfate by mass. The positive electrode plate uses a high-tin-calcium alloy grid, wherein the tin content is 1.5%-1.7% by mass.

2. The automotive starting lead-acid battery according to claim 1, characterized in that, The adhesive is selected from one or more of polytetrafluoroethylene, polyvinylidene fluoride, sodium carboxymethyl cellulose, and styrene-butadiene rubber.

3. A method for preparing an automotive starting lead-acid battery as described in claim 1 or 2, characterized in that, The step includes preparing a porous conductive carbon layer on the surface of the negative electrode separator, the step comprising: Graphite, activated carbon, acetylene black, titanium carbide, and vanadium carbide are mixed evenly in proportion, and then a binder and solvent are added and mixed to prepare a uniform slurry. The slurry is applied to the surface of the partition plate by scraping, dipping, or spraying. The porous conductive carbon layer is formed after drying at 60-80℃ for 1-2 hours. It also includes lead-acid battery formation, in which a stepped charging system is adopted: first, constant current charging at 0.15C is used to charge to 2.4V / cell, and then constant current charging at 0.08C is used until the current drops to 0.02C, thus obtaining the automotive starting lead-acid battery.

4. The method according to claim 3, characterized in that, The solvent is N-methylpyrrolidone or water, and during preparation, 80-125 parts of solvent are added by weight.

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