Anti-bulge lead-acid storage battery

Abstract

The invention discloses an anti-bulge lead-acid storage battery, and relates to the technical field of lead-acid storage batteries, the anti-bulge lead-acid storage battery is characterized in that double-layer lead paste is embedded in a positive plate, the bottom layer is a microporous layer, the surface layer is a macroporous layer, and a gradient pore structure is formed to optimize a gas emission path; graphene-stannic oxide whiskers are embedded into the negative plate to construct a three-dimensional conductive network so as to reduce polarization voltage; the composite partition plate comprises a first glass fiber pad, an anti-puncture layer and a second glass fiber pad which are different in pore diameter, electrolyte distribution is optimized, and puncture resistance is enhanced; a composite shell is composed of a polypropylene inner layer, a buffer layer and a polypropylene-carbon fiber composite outer layer and can generate reversible deformation along with pressure change. A two-stage pressure relief unit is formed by a first-stage mechanical pressure relief valve for maintaining micro-positive pressure and slowly releasing gas and a second-stage piezoelectric ceramic pressure relief valve for instantly opening and timely relieving pressure under the condition of overcharge or fault; through cooperation of the structure and the material, the swelling of the battery is improved, the cycle life is prolonged, and the problem that the existing lead-acid storage battery is easy to swell is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of lead-acid batteries, and particularly to an anti-bulging lead-acid battery. Background Art

[0002] Due to its advantages such as low cost, high reliability, and mature recycling system, lead-acid batteries play an important role in fields such as automotive starting, electric vehicle power systems, energy storage systems, and uninterruptible power supplies (UPS). However, the long-existing bulging problem of lead-acid batteries seriously restricts their performance and safety. During the charge and discharge process, due to oxygen evolution at the positive electrode and hydrogen evolution at the negative electrode, the accumulated released gas causes the internal pressure of the lead-acid battery housing to increase. Coupled with the vaporization of the electrolyte in a high-temperature environment, it is extremely easy to cause the housing to expand or even rupture, resulting in electrolyte leakage, capacity attenuation, and safety hazards.

[0003] Currently, in the existing technologies, the improvements for the bulging problem mainly focus on the following directions: Electrode structure optimization: Traditional lead-acid batteries adopt a uniformly porous electrode design (porosity 45-55%), which can ensure electrolyte infiltration, but the gas diffusion path is single, and it is easy to form retention inside the electrode plate. Among them, the existing technology has proposed adding carbon fiber to the electrode to enhance conductivity, but its uniformly distributed pores cannot direct gas flow, and the carbon material exacerbates the hydrogen evolution side reaction.

[0004] Electrolyte additives: Adding sodium sulfate, phosphoric acid, etc. can inhibit the generation of some gases, but it is difficult to balance the conductivity and the effect of inhibiting gas release.

[0005] Housing pressure relief design: Conventional pressure relief valves (such as rubber one-way valves) usually open at a pressure of 15-20 kPa, with a slow response speed (>200 ms), and cannot cope with sudden overcharging or a sharp increase in gas at high temperatures. In addition, the outer shell of the existing lead-acid battery is usually a rigid housing made of ABS plastic. When the gas release pressure inside the housing increases, it lacks the ability to adapt to deformation, is difficult to restore its original shape after deformation, and is prone to fatigue cracking after repeated deformation.

[0006] Despite the certain effects achieved by the above improvements, there are still the following technical bottlenecks: The contradiction between electrode pores and gas management: A uniform pore structure cannot balance the requirements of high reaction activity and rapid gas exhaust. Gas retention causes local pressure concentration, leading to the expansion and deformation of the electrode plate, the shedding of the active material on the grid of the electrode plate, and a decrease in the capacity of the lead-acid battery; Side effects caused by the introduction of carbon materials: Although adding carbon black or graphene to the negative electrode improves conductivity, its highly catalytic active surface exacerbates the hydrogen evolution reaction, further intensifying the bulging phenomenon of the lead-acid battery; Limitations of static pressure relief: Traditional pressure relief valves respond passively and cannot match the dynamic internal pressure of the battery. Frequent pressure relief results in electrolyte loss and accelerates battery failure; Poor adaptability to high-temperature environments: The thermal expansion coefficient of the existing housing material does not match that of the electrode plate. The bulging rate increases above 45°C, resulting in a sharp drop in the cycle life of the lead-acid battery.

[0007] Therefore, the problems existing in the current prior art are as follows:

[0008] (1) The electrode pore structure is single, the gas diffusion path is chaotic, directional gas conduction cannot be achieved, gas cannot be discharged in time, which is easy to cause bulging, and it is easy to cause the shedding of the active material on the grid, affecting the battery capacity; (2) The hydrogen evolution side reaction of the carbon material modified negative electrode is significant, and there is a lack of efficient inhibition means; (3) The pressure response of the housing is lagging, and the static pressure relief mechanism is difficult to match the dynamic internal pressure change.

[0009] In summary, it is found that the prior art has at least the following technical problems:

[0010] In the existing lead-acid battery, there are technical problems that gas release cannot be discharged in time, the hydrogen evolution reaction is difficult to efficiently inhibit, and the pressure inside the shell cannot be released in time, resulting in the problem that the lead-acid battery is easy to bulge. Summary of the Invention

[0011] The purpose of the present invention is to provide an anti-bulging lead-acid battery to solve the technical problems existing in the existing lead-acid battery, namely, gas release cannot be discharged in time, the hydrogen evolution reaction is difficult to efficiently inhibit, and the pressure inside the shell cannot be released in time.

[0012] The many technical effects that can be produced by the preferred technical solutions provided by the present invention will be elaborated in detail below.

[0013] To solve the above technical problems, the present invention provides the following technical solutions:

[0014] The present invention provides a lead-acid battery resistant to bulging, which includes a positive plate. A double-layer lead paste including a microporous layer at the bottom layer and a macroporous layer at the surface layer is embedded in the positive plate to form a gradient pore structure. The pores of the double-layer lead paste gradually increase from the inside to the outside of the positive plate to form a directional gas conduction channel; and a negative plate, on which graphene-tin dioxide whiskers are embedded to construct a three-dimensional conductive network to reduce the polarization voltage; and a composite separator, which includes a first glass fiber mat, a puncture-proof layer, and a second glass fiber mat. The pore diameter of the second glass fiber mat is larger than that of the first glass fiber mat; during installation, the first glass fiber mat faces the positive plate, and the second glass fiber mat faces the negative plate; and a composite housing, which includes a polypropylene inner layer, a buffer layer, and a polypropylene and carbon fiber composite outer layer from the inside to the outside, and is used to adapt to the expansion and deformation as the air pressure in the housing increases and the recovery deformation as the air pressure in the housing decreases; the positive plate - the composite separator - the negative plate are alternately arranged and laminated to form a plate group, which is arranged in the composite housing; and a two-stage pressure relief unit is arranged on the top of the composite housing, and the two-stage pressure relief unit includes a first-stage mechanical pressure relief valve and a second-stage piezoelectric ceramic pressure relief valve; under normal charging, the first-stage mechanical pressure relief valve maintains a slightly positive pressure in the composite housing to slowly release steady-state gas; under overcharging or sudden failure, the second-stage piezoelectric ceramic pressure relief valve instantaneously opens to relieve pressure to prevent the composite housing from over-expanding or rupturing.

[0015] In one embodiment, the positive plate includes a positive plate grid and the double-layer lead paste; the main rib bars of the positive plate grid are radially arranged within the plate frame, and the thickness of the rib bar located at the center of the plate frame is less than that of the rib bar located at the edge of the plate frame; short-cut glass fibers are added to the microporous layer of the double-layer lead paste, and nano-carbon fibers are added to the macroporous layer.

[0016] In one embodiment, the lead paste of the microporous layer is coated on the rib bars of the positive plate grid, and the thickness is controlled within 0.3 - 0.5 mm, the porosity is controlled within 45 - 50%, the pore diameter is controlled within 50 - 100 μm, and the addition amount of short-cut glass fibers is controlled within 0.5 - 1.0 wt%; the lead paste of the macroporous layer is coated on the microporous lead paste, and the thickness is controlled within 1.2 - 1.5 mm, the porosity is controlled within 30 - 35%, the pore diameter is controlled within 20 - 50 μm, and the addition amount of nano-carbon fibers is controlled within 1.0 - 1.5 wt%.

[0017] In one embodiment, the short-cut length of the short-cut glass fibers is 3 - 4.5 mm.

[0018] In one embodiment, the negative electrode plate includes a negative electrode grid and negative electrode paste; the ribs of the negative electrode grid are vertically and staggeredly arranged, and the ribs located within the plate frame have the same thickness; the graphene-tin dioxide whisker is composed of nitrogen-doped graphene sheets and tin dioxide, and the tin dioxide forms a composite structure of graphene base + tin dioxide whiskers by growing tin dioxide whiskers on the surface of the graphene sheets through chemical vapor deposition process; and the graphene-tin dioxide whiskers are embedded in the negative electrode paste, and the graphene in the graphene-tin dioxide whiskers forms a longitudinal conductive main path in the negative electrode paste, and the tin dioxide whiskers vertically penetrate the negative electrode paste to form longitudinal conductive branch paths, which are used to improve the electron passability.

[0019] In one embodiment, the buffer layer includes honeycomb aluminum and silica gel, and the silica gel is filled in the honeycomb aluminum and wraps the honeycomb aluminum.

[0020] In one embodiment, the thickness of the first glass fiber mat is controlled to be 0.3 - 0.4 mm, and the pore diameter is 5 - 10 μm. The small pore diameter is used to prevent short circuit caused by lead crystal puncture; the anti-puncture layer is a composite layer of polyethylene and glass fiber mat, and the thickness of the anti-puncture layer is controlled to be 0.5 - 0.7 mm, and the pore diameter is 20 - 30 μm; the thickness of the second glass fiber mat is controlled to be 0.4 - 0.6 mm, and the pore diameter is 30 - 50 μm. The large pore diameter is used to guide the gas generated by the negative electrode plate to discharge from the composite separator; and the pore diameters of the first glass fiber mat, the anti-puncture layer, and the second glass fiber mat increase in sequence to form a gradient pore diameter, which is used to promote and guide the flow direction of the electrolyte, and form a liquid storage between the first glass fiber mat and the second glass fiber mat to increase the electrolyte retention.

[0021] In one embodiment, an alumina coating is coated on the first glass fiber mat, which is used to reduce the pore diameter of the first glass fiber mat and improve the pressure resistance to avoid the growth and puncture short circuit of lead crystals, and improve the thermal stability of the first glass fiber mat to reduce the shrinkage of the composite separator.

[0022] In one embodiment, the primary mechanical pressure relief valve includes a silica gel diaphragm and a spring, the opening pressure is 12 kPa, and the response time is 200 - 300 ms.

[0023] In one embodiment, the secondary piezoelectric ceramic pressure relief valve includes a piezoelectric ceramic sheet, a control unit, and a pressure sensor. The pressure sensor and the piezoelectric ceramic sheet are both electrically connected to the control unit. The pressure sensor detects the pressure inside the composite housing. The opening threshold of the secondary piezoelectric ceramic pressure relief valve is that the internal pressure of the composite housing is greater than 20 kPa or the pressure change rate is greater than 5 kPa / s, and the response time is <50 ms. It is used to perform emergency pressure relief on the composite housing when the lead-acid battery is overcharged or suddenly fails.

[0024] The beneficial effects of the present invention are as follows:

[0025] In the present invention, by embedding a double-layered lead paste including a microporous layer at the bottom layer and a macroporous layer at the surface layer on the positive plate, a gradient pore structure is formed. The pores of the double-layered lead paste gradually increase from the inside to the outside of the positive plate to form a directional gas conduction channel. The composite separator includes a first fiberglass mat, a puncture-proof layer, and a second fiberglass mat. The pore diameter of the second fiberglass mat is larger than that of the first fiberglass mat. During installation, the first fiberglass mat faces the positive plate, and the second fiberglass mat faces the negative plate. Cooperating with the double-stage pressure relief unit provided at the top of the composite housing, gas directional guidance and pressure dynamic balance are achieved.

[0026] (1) Optimize the pore structure of the positive plate and improve the gas emission efficiency

[0027] It is difficult for the gas inside the positive plate of a traditional lead-acid battery to be effectively discharged and is likely to accumulate during the charge and discharge process, resulting in an increase in the internal pressure of the battery. In the present invention, by embedding a double-layered lead paste in the positive plate, with a microporous layer at the bottom layer and a macroporous layer at the surface layer, a gradient pore structure is formed, which forms the main channel for gas discharge from the positive plate. This structure can guide the precipitated gas to be discharged along a predetermined direction, improve the gas emission efficiency, and reduce the risk of internal gas accumulation. Cooperating with the structure of the composite separator with an increasing pore diameter from the positive plate side to the negative plate side, the gas from the positive plate is guided into the space between the puncture-proof layer and the second fiberglass mat of the composite separator. The gas from the negative plate also passes through the second fiberglass mat and enters the space between the puncture-proof layer and the second fiberglass mat. The gas from the positive and negative plates can accelerate and overflow from the composite separator and diffuse to the double-stage pressure relief unit. The gas residence time is shortened from 30 s to 8 s, reducing the swelling caused by the continuous increase in the internal pressure of the battery due to gas retention, thereby reducing the occurrence of swelling. It can also reduce the shedding of the active material caused by the irregular overflow of gas on the positive and negative plates, resulting in a reduction in the battery capacity.

[0028] (2) Optimize the structure of the composite separator and improve the battery stability

[0029] The composite separator adopts a multi-layer design. During installation, the first fiberglass mat faces the positive electrode plate, and the second fiberglass mat faces the negative electrode plate. This structure can also optimize the distribution of the electrolyte, improve the uniformity of the reaction between the positive and negative electrode plates and the electrolyte. At the same time, compared with the separator of traditional lead-acid batteries, the composite separator of this application also enhances the puncture resistance, reduces the risk of short circuit caused by lead crystal puncture, and improves the overall stability and safety of the battery.

[0030] (3) Adopt graphene-tin dioxide whisker negative electrode material to reduce the polarization voltage

[0031] In traditional lead-acid batteries, the negative electrode plate is prone to hydrogen evolution reaction, which leads to an increase in water loss in the battery, and then accelerates the battery aging. In the present invention, graphene-tin dioxide whiskers are embedded in the negative electrode plate to construct a three-dimensional conductive network, improve the overall conductivity and specific surface area of the negative electrode plate, thereby improving the electron transfer efficiency, reducing the internal resistance, realizing the reduction of the polarization voltage, reducing the driving force of the hydrogen evolution reaction, reducing the occurrence of the hydrogen evolution reaction, and improving the cycle life and charge-discharge performance of the lead-acid battery.

[0032] (4) Innovative composite housing design to enhance the pressure regulation ability

[0033] The traditional battery housing is prone to irreversible deformation or rupture when the internal pressure increases. The composite housing of the present invention adopts a multi-layer structure, which sequentially includes a polypropylene inner layer, a buffer layer, and a polypropylene and carbon fiber composite outer layer from the inside to the outside. Among them, the buffer layer can absorb the deformation caused by the internal pressure change, so that the housing can expand and deform when the air pressure increases, return to its original state when the air pressure decreases, and reduce the influence of external high-frequency vibration on the active substances on the positive and negative electrode plates (especially when used as a power battery on an electric vehicle), reducing the additional loss of battery capacity. This deformable housing design can effectively reduce the irreversible expansion of the internal gas accumulation on the battery housing and the influence of external vibration conduction on the battery capacity, and improve the safety and durability of the battery.

[0034] (5) Dual-stage pressure relief unit to improve safety

[0035] The dual-stage pressure relief valve unit realizes hierarchical pressure management of the composite housing by setting a primary mechanical pressure relief valve and a secondary piezoelectric ceramic pressure relief valve. By maintaining a slightly positive pressure in the composite housing through the primary mechanical pressure relief valve, it helps to maintain the efficiency of oxygen recombination. When the pressure in the composite housing reaches the pressure at which the mechanical pressure relief valve opens, it can also release the steady-state gas in the housing to avoid excessive accumulation of internal gas.

[0036] Through the secondary piezoelectric ceramic pressure relief valve, in the case of overcharging or sudden failure of the battery, when sudden overpressure occurs in the composite housing, it can instantaneously open the valve body for pressure relief with an extremely high response speed, quickly release the internal pressure, and prevent the composite housing from overpressurizing and overexpanding, resulting in irreversible deformation or rupture of the housing.

[0037] (6) Performance improvement of battery cycle life and capacity retention rate

[0038] For the lead-acid battery of the present invention, when the battery temperature is maintained below 45°C and under the cycle of 90% charge-discharge capacity, the cycle life is increased from 400 times to 435 times, and the capacity attenuation rate is reduced; moreover, the capacity retention rate of the lead-acid battery of the present invention is about 85%, which is improved compared with the capacity retention rate of only about 70% for traditional lead-acid batteries; the lead-acid battery of the present invention is suitable for use in start-stop systems with high-frequency start-stop requirements.

[0039] The present invention provides a bulge-proof lead-acid battery. By optimizing the plate structure, separator structure and materials, and housing design, and introducing a two-stage pressure relief unit, it effectively solves the bulge problem of lead-acid batteries caused by the inability to timely discharge evolved gas, high polarization voltage, and pressure accumulation in the housing during use. It can effectively inhibit the bulge phenomenon, improve the service life, safety, and charge-discharge performance of the battery, and has significant technical advantages and application value. Brief Description of the Drawings

[0040] In order to more clearly illustrate the technical solutions of the present invention, the drawings required for implementation will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0041] Figure 1 is a schematic structural diagram of the bulge-proof lead-acid battery of the present invention;

[0042] Figure 2 is a schematic structural diagram of the negative plate grid of the present invention;

[0043] Figure 3 is a schematic structural diagram of the positive plate grid of the present invention;

[0044] Figure 4 is a schematic combined structural diagram of the positive plate, negative plate and composite separator of the present invention.

[0045] Among them, the reference numerals are as follows:

[0046] 1. Positive plate; 11. Positive plate grid; 111. Main rib; 112. Auxiliary rib;

[0047] 2. Negative plate; 21. Negative plate grid

[0048] 3. Composite separator

[0049] 4. Composite housing

[0050] 5. Dual-stage pressure relief unit; 51. First-stage mechanical pressure relief valve; 52. Second-stage piezoelectric ceramic pressure relief valve Detailed implementation manners

[0051] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention

[0052] A bulging-proof lead-acid battery is provided in the detailed implementation manners, which effectively solves the technical problems of the existing lead-acid batteries, such as the gas release cannot be discharged in time, it is difficult to efficiently inhibit the hydrogen evolution reaction, and the pressure inside the shell cannot be released in time, and avoids the problem that the lead-acid battery is prone to bulging

[0053] The first embodiment of the bulging-proof lead-acid battery is as Figures 1 to 4 shown, including a positive plate 1, in which a double-layer lead paste including a microporous layer at the bottom layer and a macroporous layer at the surface layer is embedded to form a gradient pore structure, and the pores of the double-layer lead paste gradually increase from the inside to the outside of the positive plate 1 to form a directional gas conduction channel; and a negative plate 2, on which graphene-tin dioxide whiskers are embedded to construct a three-dimensional conductive network to reduce the polarization voltage; and a composite separator 3, the composite separator 3 includes a first glass fiber mat, a puncture-proof layer and a second glass fiber mat, and the pore diameter of the second glass fiber mat is larger than that of the first glass fiber mat; during installation, the first glass fiber mat faces the positive plate 1, and the second glass fiber mat faces the negative plate 2; and a composite housing 4, the composite housing 4 is provided from the inside to the outside with a polypropylene inner layer, a buffer layer, a polypropylene and carbon fiber composite outer layer, which is used to adapt to the expansion deformation as the air pressure inside the shell increases and the recovery deformation as the air pressure inside the shell decreases; the positive plate 1 - the composite separator 3 - the negative plate 2 are alternately arranged and laminated to form a plate group, and are arranged inside the composite housing 4; and a dual-stage pressure relief unit 5 provided at the top of the composite housing 4, the dual-stage pressure relief unit 5 includes a first-stage mechanical pressure relief valve 51 and a second-stage piezoelectric ceramic pressure relief valve 52; under normal charging, the first-stage mechanical pressure relief valve 51 maintains a slightly positive pressure inside the composite housing 4 and slowly releases the steady-state gas; under overcharging or sudden failure, the second-stage piezoelectric ceramic pressure relief valve 52 instantaneously opens to relieve pressure, avoiding excessive expansion or rupture of the composite housing 4

[0054] The present invention provides a lead-acid battery resistant to bulging. By optimizing the plate structure, separator structure and materials, and the housing design, and introducing a two-stage pressure relief unit 5, it effectively solves the problem of bulging of lead-acid batteries during use due to the inability to timely discharge evolved gas, high polarization voltage, and pressure accumulation in the housing, and can effectively inhibit the bulging phenomenon, improving the service life, safety, and charge and discharge performance of the battery. Among them, the specific improvements are as follows:

[0055] By optimizing the pore structure of the positive plate, the gas emission efficiency is improved. In a traditional lead-acid battery, it is difficult for the gas inside the positive plate 1 to be effectively discharged and is prone to accumulate during charge and discharge, resulting in an increase in the internal pressure of the battery. In the present invention, a double-layer lead paste is embedded in the positive plate 1, where the bottom layer is a microporous layer and the surface layer is a macroporous layer, forming a gradient pore structure, which forms the main channel for the gas to be discharged from the positive plate 1. This structure can guide the evolved gas to be discharged along a predetermined direction, improve the gas emission efficiency, and reduce the risk of internal gas accumulation. Cooperating with the structure of the composite separator 3 with an increasing pore diameter from the side of the positive plate 1 to the side of the negative plate 2, the gas from the positive plate 1 is guided into the space between the puncture-proof layer of the composite separator 3 and the second fiberglass mat, and the gas from the negative plate 2 also passes through the second fiberglass mat and enters the space between the puncture-proof layer and the second fiberglass mat. The gas from the positive and negative plates 2 can accelerate and overflow from the composite separator 3 and diffuse to the two-stage pressure relief unit 5. The gas residence time is shortened from 30 s to 8 s, reducing the bulging caused by the continuous increase in the internal pressure of the battery due to gas retention, thereby reducing the occurrence of the bulging phenomenon. It can also reduce the shedding of the active material on the positive and negative plates 2 caused by the irregular overflow of gas, resulting in a reduction in the battery capacity.

[0056] By optimizing the composite separator structure, the battery stability is improved. The composite separator 3 adopts a multi-layer design, and during installation, the first fiberglass mat faces the positive plate 1 and the second fiberglass mat faces the negative plate 2. This structure can also optimize the distribution of the electrolyte and improve the uniformity of the reaction between the positive and negative plates 2 and the electrolyte. At the same time, compared with the separator of a traditional lead-acid battery, the composite separator 3 of the present application also enhances the puncture resistance, reduces the risk of short circuit caused by lead crystal puncture, and improves the overall stability and safety of the battery.

[0057] By using a graphene-tin dioxide whisker negative electrode material, the polarization voltage is reduced. In a traditional lead-acid battery, the negative plate 2 is prone to hydrogen evolution reaction, resulting in an increase in water loss inside the battery, which in turn accelerates the battery aging. In the present invention, graphene-tin dioxide whiskers are embedded in the negative plate 2 to construct a three-dimensional conductive network, improving the overall conductivity and specific surface area of the negative plate 2, thereby enhancing the electron transfer efficiency, reducing the internal resistance, and thus achieving a reduction in the polarization voltage, reducing the driving force of the hydrogen evolution reaction, reducing the occurrence of the hydrogen evolution reaction, and improving the cycle life and charge and discharge performance of the lead-acid battery.

[0058] By adopting the composite structure of the composite shell, the pressure regulation ability is enhanced; the traditional battery shell is prone to irreversible deformation or rupture when the internal pressure increases. The composite shell 4 of the present invention adopts a multi-layer structure, which sequentially includes a polypropylene inner layer, a buffer layer, and a polypropylene and carbon fiber composite outer layer from the inside to the outside; wherein, the buffer layer can absorb the deformation caused by the internal pressure change, so that the shell can expand and deform when the air pressure increases, return to its original state when the air pressure decreases, and reduce the influence of external high-frequency vibration on the active substances on the positive and negative plates 2 (especially when used as a power battery in an electric vehicle), reducing the additional loss of battery capacity; this deformable shell design can effectively reduce the irreversible expansion of the internal gas accumulation on the battery shell and the influence of external vibration conduction on the battery capacity, improving the safety and durability of the battery.

[0059] By means of a bipolar pressure relief unit, the safety is improved; the bipolar pressure relief valve unit realizes hierarchical pressure management of the composite shell 4 by setting a primary mechanical pressure relief valve 51 and a secondary piezoelectric ceramic pressure relief valve 52; by maintaining a slightly positive pressure in the composite shell 4 through the primary mechanical pressure relief valve 51, under the slightly positive pressure, it helps to maintain the efficiency of oxygen recombination, and when the pressure in the composite shell 4 reaches the pressure at which the mechanical pressure relief valve opens, it can also release the steady-state gas in the shell, avoiding excessive accumulation of internal gas.

[0060] Through the secondary piezoelectric ceramic pressure relief valve 52, in the case of overcharging or sudden failure of the battery, when there is a sudden overpressure in the composite shell 4, it can instantaneously open the valve body for pressure relief at an extremely high response speed, quickly releasing the internal pressure, and avoiding overexpansion of the composite shell 4 due to overpressure, resulting in irreversible deformation of the shell or shell rupture.

[0061] Improve the performance of the battery cycle life and capacity retention rate; for the lead-acid battery of the present invention, when the temperature of the battery is kept below 45°C and under the cycle of 90% charge and discharge capacity, the cycle life is increased from 400 times to 435 times, and the capacity attenuation rate is reduced; and the capacity retention rate of the lead-acid battery of the present invention is about 85%, compared with the capacity retention rate of only about 70% of the traditional lead-acid battery, it is improved; the lead-acid battery of the present invention is suitable for use in a start-stop system with high-frequency start-stop requirements.

[0062] As one of the optional implementation manners

[0063] Regarding the specific structure of the above-mentioned positive plate 1, this embodiment is as follows Figure 3 As shown, the positive plate 1 includes a positive plate grid 11 and a double-layer lead paste; the main rib strips 111 of the positive plate grid 11 are arranged radially in the plate frame, and the thickness of the rib strip located at the center of the plate frame is smaller than the thickness of the rib strip located at the edge of the plate frame; short-cut glass fibers are added to the microporous layer of the double-layer lead paste, and nano-carbon fibers are added to the macroporous layer.

[0064] Among them, the width of the main rib 111 of the positive grid 11 is 1.0 - 1.2 mm. The positive grid 11 also has auxiliary ribs 112 which are perpendicular to the opposite sides of the frame and intersect with the main ribs 111. The width of the auxiliary ribs 112 is 0.6 - 0.8 mm. The thickness of the ribs at the center of the frame is 2.0 mm, and the thickness of the ribs at the edge of the frame is 2.5 mm, which helps to optimize the current distribution of the positive plate 1, reduce the edge effect, and improve the charge and discharge performance of the positive plate 1.

[0065] The short cutting length of the chopped glass fiber is 3 - 4.5 mm.

[0066] When in application, the whole positive grid 11 is made of lead - calcium - tin alloy, which helps to improve the corrosion resistance of the positive grid 11. The chopped glass fiber has the performance of enhancing mechanical support. In the paste of the microporous layer, the chopped glass fiber can enhance the creep resistance of the positive plate 1, reduce the expansion rate of the positive plate 1 compared with the traditional positive plate 1, and prevent the substances on the positive grid 11 from falling off. And the nano - carbon fiber added in the macroporous layer helps to expand the pores and improve the paste forming of the macroporous layer, avoid the shedding of the active substances, and at the same time realize rapid gas conduction and reduce gas retention.

[0067] Regarding the above - mentioned double - layer paste using the layer - by - layer coating process, specifically, the paste of the microporous layer is coated on the ribs of the positive grid, and the thickness is controlled at 0.3 - 0.5 mm, the porosity is controlled at 45 - 50%, the pore diameter is controlled at 50 - 100 μm, and the addition amount of the chopped glass fiber is controlled at 0.5 - 1.0 wt%. The paste of the macroporous layer is coated on the microporous paste, and the thickness is controlled at 1.2 - 1.5 mm, the porosity is controlled at 30 - 35%, the pore diameter is controlled at 20 - 50 μm, and the addition amount of the nano - carbon fiber is controlled at 1.0 - 1.5 wt%.

[0068] Among them, the wt% here refers to the mass percentage.

[0069] Regarding the specific structure of the above - mentioned negative plate 2, in this embodiment, as Figure 2 shown, the negative plate 2 includes a negative grid 21 and a negative paste. The ribs of the negative grid 21 are arranged vertically and cross - staggeredly, and the thickness of the ribs located within the frame is the same. The graphene - tin dioxide whisker is composed of nitrogen - doped graphene sheets and tin dioxide. Tin dioxide grows tin dioxide whiskers on the surface of the graphene sheets through chemical vapor deposition to form a composite structure of graphene base + tin dioxide whiskers. And the graphene - tin dioxide whiskers are embedded in the negative paste. The graphene in the graphene - tin dioxide whiskers forms a longitudinal conductive main path in the negative paste, and the tin dioxide whiskers vertically penetrate the negative paste to form longitudinal conductive branches, which are used to improve the electron conductivity.

[0070] Among them, the ribs of the negative plate grid 21 are vertically and staggeredly arranged, and the thickness of the ribs located within the plate frame is consistent, ensuring uniform current distribution and maintaining the stability of the current density. Nitrogen doping treatment of the graphene sheets can increase their surface hydrophilicity and promote electrolyte infiltration.

[0071] During application, the negative plate grid 21 is made of lead-calcium alloy, and 2-5 μm of tin is plated on its surface, which increases the hydrogen evolution overpotential of the negative plate 2 by 50 mV. The higher the overpotential, the greater the energy barrier required for the hydrogen evolution reaction, and the more difficult the reaction is to occur. Thus, the occurrence of the hydrogen evolution reaction is inhibited, the generation of hydrogen is reduced, and the bulging phenomenon and safety risk of the battery are decreased.

[0072] Since the dangling bonds at the edges of graphene are high-activity sites for hydrogen evolution, SnO2 whiskers grow vertically on the surface of graphene to cover its edges, reducing the exposed catalytic active sites and controlling the generation of the hydrogen evolution reaction. At the same time, taking advantage of the ultra-high conductivity and high specific surface area of the graphene sheets to provide a high-speed electron transport channel to make up for the poor intrinsic conductivity of tin dioxide, the tin dioxide whiskers are anchored on the surface of graphene and vertically embedded in the lead paste of the negative plate 2 to prevent stacking when the graphene-tin dioxide whiskers are embedded in the negative lead paste, thereby maintaining a high specific surface area, enhancing the overall conductivity of the negative plate 2, improving the electron transport efficiency, reducing the internal resistance, reducing the polarization voltage, reducing the driving force of the hydrogen evolution reaction, reducing the occurrence of the hydrogen evolution reaction, and enhancing the cycle life and charge-discharge performance of the lead-acid battery.

[0073] Regarding the specific structure of the buffer layer of the above composite housing 4, the buffer layer includes honeycomb aluminum and silica gel, and the silica gel is filled in the honeycomb aluminum and wraps the honeycomb aluminum.

[0074] During application, the honeycomb aluminum provides high compressive capacity to maintain strength, while the elasticity of the filled and wrapped silica gel provides the restoring force for plastic deformation and can also absorb the energy of high-frequency vibration, enhancing the deformation capacity and safety of the composite housing 4, and contributing to improving the stability of the charge-discharge performance of the lead-acid battery.

[0075] Regarding the specific structure of the above composite separator 3, the thickness of the first glass fiber mat is controlled at 0.3 - 0.4 mm, and the pore diameter is 5 - 10 μm. The small pore diameter is used to prevent short circuit caused by lead crystal puncture; the puncture-proof layer is a composite layer of polyethylene and the glass fiber mat, and the thickness of the puncture-proof layer is controlled at 0.5 - 0.7 mm, and the pore diameter is 20 - 30 μm; the thickness of the second glass fiber mat is controlled at 0.4 - 0.6 mm, and the pore diameter is 30 - 50 μm. The large pore diameter is used to guide the gas generated by the negative plate 2 to discharge from the composite separator 3; and the pore diameters of the first glass fiber mat, the puncture-proof layer, and the second glass fiber mat increase in sequence to form a gradient pore diameter, which is used to promote and guide the flow direction of the electrolyte and form a liquid storage between the first glass fiber mat and the second glass fiber mat, enhancing the electrolyte retention.

[0076] During application, the structure of the composite separator 3 with gradually increasing pore diameter from the positive plate 1 side to the negative plate 2 side can guide the gas from the positive plate 1 into the space between the puncture-proof layer of the composite separator 3 and the second fiberglass mat. The gas from the negative plate 2 also passes through the second fiberglass mat and enters the space between the puncture-proof layer and the second fiberglass mat. The gases from the positive and negative plates 2 can then accelerate and overflow from the composite separator 3 and diffuse to the double-stage pressure relief unit 5.

[0077] Regarding the specific structure and performance of the above-mentioned primary mechanical pressure relief valve 51, the primary mechanical pressure relief valve 51 includes a silicone diaphragm and a spring, with an opening pressure of 12 kPa and a response time of 200 - 300 ms.

[0078] During the floating charge stage of the lead-acid battery when a small amount of gas is released, when the internal pressure in the composite housing 4 accumulates to be greater than 12 kPa, the opening condition of the primary mechanical pressure relief valve 51 can be triggered. By opening the primary mechanical pressure relief valve 51, the steady-state gas in the composite housing 4 is slowly released, preventing the frequent triggering of the secondary piezoelectric ceramic pressure relief valve 52, which may cause excessive gas release and lead to water loss in the electrolyte (lost in the form of hydrogen and oxygen).

[0079] Regarding the specific structure and performance of the above-mentioned secondary mechanical pressure relief valve, the secondary piezoelectric ceramic pressure relief valve 52 includes a piezoelectric ceramic sheet, a control unit, and a pressure sensor. Both the pressure sensor and the piezoelectric ceramic sheet are electrically connected to the control unit. The pressure sensor detects the pressure inside the composite housing 4. The opening threshold of the secondary piezoelectric ceramic pressure relief valve 52 is that the internal pressure of the composite housing 4 is greater than 20 kPa or the pressure change rate is greater than 5 kPa / s, and the response time < 50 ms. It is used to perform emergency pressure relief on the composite housing 4 when the lead-acid battery experiences overcharge or sudden failure.

[0080] During application, the internal pressure of the composite housing 4 is monitored in real time through the pressure sensor. The control unit receives the pressure signal feedback from the pressure sensor. When the internal pressure of the composite housing 4 is greater than 20 kPa, the control unit applies a voltage to the piezoelectric ceramic sheet. The piezoelectric ceramic sheet deforms, and the secondary piezoelectric ceramic pressure relief valve 52 instantaneously deforms and opens to release the gas inside the composite housing 4 for emergency pressure relief.

[0081] The second embodiment of the anti-bulging lead-acid battery. The difference between this embodiment and the first embodiment is that the structure of the first fiberglass mat is strengthened. The first fiberglass mat is coated with an alumina coating, which is used to reduce the pore diameter of the first fiberglass mat and improve the pressure resistance to avoid short circuit caused by lead crystal growth piercing the composite separator 3, and to improve the thermal stability of the first fiberglass mat and reduce the shrinkage of the composite separator 3.

[0082] When in application, the alumina coating can enhance the compressive capacity of the first fiberglass mat in the composite separator 3, reduce the degree of compression of the composite separator 3 due to thermal expansion and contraction and the high pressure inside the shell during the charging and discharging heat generation of the battery, and help extend the service life of the composite separator 3; when the lead-acid battery is floating charged or overcharged at high temperature, it can prevent the positive plate 1 and the negative plate 2 from contacting and short-circuiting due to the shrinkage of the composite separator 3, thereby extending the service life of the lead-acid battery.

[0083] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. An anti-bulging lead-acid battery, characterized in that: It comprises a positive electrode plate, on which a double-layer lead paste including a microporous layer at the bottom layer and a macroporous layer at the surface layer is embedded to form a gradient pore structure, wherein the pores of the double-layer lead paste gradually increase from the inside to the outside of the positive electrode plate to form a directional air guide channel; and a negative electrode plate, wherein graphene-tin dioxide whiskers are embedded in the negative electrode plate to construct a three-dimensional conductive network to reduce polarization voltage; and a composite separator, the composite separator comprising a first glass fiber mat, an anti-puncture layer and a second glass fiber mat, the pore size of the second glass fiber mat being larger than that of the first glass fiber mat; when installed, the first glass fiber mat faces the positive electrode plate, and the second glass fiber mat faces the negative electrode plate; and a composite shell, the composite shell comprising, from the inside to the outside, a polypropylene inner layer, a buffer layer, and a polypropylene and carbon fiber composite outer layer, for adapting to expansion deformation as the air pressure inside the shell increases, and recovering deformation as the air pressure inside the shell decreases; The positive electrode plate, the composite separator and the negative electrode plate are alternately arranged and stacked to form an electrode plate group, and are arranged in the composite shell; and a double-stage pressure relief unit disposed on the top of the composite shell, the double-stage pressure relief unit comprising a primary mechanical pressure relief valve and a secondary piezoelectric ceramic pressure relief valve; Under normal charging, the first-level mechanical pressure relief valve maintains a slight positive pressure in the composite shell and slowly releases steady-state gas; under overcharging or sudden failure, the second-level piezoelectric ceramic pressure relief valve opens instantly to release pressure to prevent the composite shell from over-expansion or rupture.

2. The anti-bulging lead-acid battery according to claim 1, characterized in that: The positive plate comprises a positive plate grid and the double-layer lead paste; The main ribs of the positive plate grid are arranged radially in the plate frame, and the thickness of the ribs located at the center of the plate frame is less than the thickness of the ribs located at the edge of the plate frame; The microporous layer of the double-layer lead paste is added with short-cut glass fibers, and the macroporous layer is added with nano-carbon fibers.

3. The anti-bulging lead-acid battery according to claim 2, characterized in that: The lead paste of the microporous layer is coated on the ribs of the positive plate grid, and the thickness is controlled at 0.3-0.5 mm, the porosity is controlled at 45-50%, the pore size is controlled at 50-100 μm, and the addition amount of chopped glass fiber is controlled at 0.5-1.0 wt%; The macroporous layer of lead paste is coated on the microporous lead paste, and the thickness is controlled at 1.2-1.5 mm, the porosity is controlled at 30-35%, the pore size is controlled at 20-50 μm, and the amount of nano-carbon fiber added is controlled at 1.0-1.5 wt%.

4. The anti-bulging lead-acid battery according to claim 3, characterized in that: The chopped length of the chopped glass fibers is 3-4.5 mm.

5. The anti-bulging lead-acid battery according to claim 1, characterized in that: The negative plate comprises a negative grid and negative lead paste; the ribs of the negative grid are vertically staggered, and the ribs located in the plate frame are of uniform thickness; The graphene-tin dioxide whiskers are composed of nitrogen-doped graphene sheets and tin dioxide, and the tin dioxide whiskers are grown on the surface of the graphene sheets by chemical vapor deposition to form a composite structure of graphene base + tin dioxide whiskers; The graphene-tin dioxide whiskers are embedded in the negative electrode lead paste, the graphene in the graphene-tin dioxide whiskers forms a longitudinal conductive main path in the negative electrode lead paste, and the tin dioxide whiskers vertically penetrate the negative electrode lead paste to form a longitudinal conductive branch path, which is used to improve the electron permeability.

6. The anti-bulging lead-acid battery according to claim 1, characterized in that: The buffer layer includes honeycomb aluminum and silica gel, and the silica gel is filled in the honeycomb aluminum and wraps the honeycomb aluminum.

7. The anti-bulging lead-acid battery according to claim 1, characterized in that: The thickness of the first glass fiber mat is controlled to be 0.3-0.4 mm, and the pore size is 5-10 μm. The small pore size is used to prevent lead crystals from puncturing and causing short circuits. The puncture-proof layer is a composite interlayer of polyethylene and glass fiber mat, and the thickness of the puncture-proof layer is controlled to be 0.5-0.7 mm, and the pore size is 20-30 μm; The thickness of the second glass fiber mat is controlled to be 0.4-0.6 mm, and the pore size is 30-50 μm, and the large pore size is used to guide the gas generated by the negative plate to be discharged from the composite separator; The pore sizes of the first glass fiber mat, the anti-puncture layer and the second glass fiber mat are increased successively to form a gradient pore size, which is used to promote and guide the flow direction of the electrolyte, and form a liquid storage between the first glass fiber mat and the second glass fiber mat to increase the electrolyte retention.

8. The anti-bulging lead-acid battery according to claim 7, characterized in that: The first glass fiber mat is coated with an alumina coating to reduce the pore size of the first glass fiber mat and improve the compressive strength to avoid lead crystal growth puncture short circuit, and to improve the thermal stability of the first glass fiber mat and reduce the shrinkage of the composite partition.

9. The anti-bulging lead-acid battery according to claim 1, characterized in that: The first-stage mechanical pressure relief valve includes a silicone diaphragm and a spring, with an opening pressure of 12 kPa and a response time of 200-300 ms.

10. The anti-bulging lead-acid battery according to claim 9, characterized in that: The secondary piezoelectric ceramic pressure relief valve includes a piezoelectric ceramic sheet, a control unit and a pressure sensor. The pressure sensor and the piezoelectric ceramic sheet are electrically connected to the control unit. The pressure sensor detects the pressure inside the composite shell. The opening threshold of the secondary piezoelectric ceramic pressure relief valve is that the internal pressure of the composite shell is greater than 20kPa or the pressure change rate is greater than 5kPa / s, and the response time is less than 50ms. It is used for emergency pressure relief of the composite shell when the lead-acid battery is overcharged or suddenly fails.

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