Lead-acid battery of gradient-density active substance and preparation process of lead-acid battery

Abstract

The invention discloses a lead-acid battery with gradient density active substances and a preparation process, and relates to the technical field of battery preparation, the lead-acid battery comprises positive plates, negative plates and a battery shell, the positive plates and the negative plates are arranged in parallel and distributed in a staggered manner to form electrodes, and partition plates are arranged between the positive plates and the negative plates which are arranged in a staggered manner; grids are arranged at the centers of the positive plate and the negative plate, and the positive plate is composed of the grid at the center and positive active substances filled at the two sides. By designing gradient density distribution of active substances along the thickness direction of the polar plate, the number of active reaction sites in unit volume can be increased by a middle high-apparent-density region, and the energy density and high-rate charge-discharge performance of the battery are enhanced; the porous structure of the edge low-apparent-density region can provide sufficient channels for ion migration, alleviate the problems of volume expansion and falling of active substances in charge-discharge cycles, and greatly prolong the cycle life of the battery.

Description

Technical Field

[0001] This invention relates to the field of battery manufacturing technology, specifically to a lead-acid battery with gradient density active materials and its manufacturing process. Background Technology

[0002] Lead-acid batteries are widely used in new energy vehicles, energy storage systems, backup power supplies, and other fields due to their low cost, high reliability, and excellent high-current discharge performance. However, as market demands for battery energy density, cycle life, and safety performance continue to rise, the technological bottlenecks of traditional lead-acid batteries are becoming increasingly apparent. Their core shortcomings lie in low utilization of active materials, easy shedding and failure during cycling, and insufficient ion conduction efficiency.

[0003] However, in existing technologies, the positive and negative electrode active materials of lead-acid batteries are mostly filled with uniform density, which makes it difficult to meet the dual requirements of "high energy density" and "long cycle life". If the active material is densified as a whole to increase energy density, it will lead to narrow ion migration channels, and reaction products will easily accumulate during charging and discharging, which will aggravate the volume expansion and shedding of the active material and shorten the battery cycle life. If the porosity of the active material is too high to ensure ion conduction, it will reduce the number of active reaction sites per unit volume, resulting in a decrease in battery energy density and charge / discharge rate performance. Summary of the Invention

[0004] The purpose of this invention is to provide a lead-acid battery with gradient density active materials and a preparation process thereof, in order to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a lead-acid battery with gradient density active material, comprising a positive electrode plate, a negative electrode plate, and a battery casing. The positive and negative electrode plates are arranged in parallel and staggered to form electrodes. A separator is provided between the staggered positive and negative electrode plates. A grid is provided at the center of each of the positive and negative electrode plates. The positive electrode plate is composed of a central grid and positive active material filled on both sides. The negative electrode plate is composed of a central grid and negative active material filled on both sides. The distribution of the positive and negative active materials is such that they vary in gradient along the thickness direction of the positive electrode plate, and the apparent density (apparent density is the mass per unit volume of a substance in its natural packing state, which is different from the true density of a substance and can be used to represent the packing density of porous materials) in the central region is greater than that in the edge region. The battery casing is filled with an electrolyte, which acts as an ion transport medium to conduct ions and complete the charge migration inside the battery, forming a complete current loop in conjunction with the electron flow of the positive and negative electrode plates.

[0006] Preferably, a cover is installed on the top of the battery casing, and the interior of the battery casing is provided with multiple sets of equally spaced compartments. An electrolyte filling port is provided on the surface of the cover directly above each compartment, and the electrolyte filling port is sealed with a sealing plug.

[0007] Preferably, the top of the grid is provided with tabs, and connecting bridges are connected between tabs of the same polarity. Several positive and negative plates form a battery unit and are installed inside the compartment. Battery units in two adjacent compartments are connected in series by connecting bridges, and a set of connecting bridges at both ends pass through the casing to form electrode contacts.

[0008] Preferably, the partition is made of ultra-fine glass fiber cotton and polypropylene composite, the thickness of the partition is 1.2-1.8mm, and the interior of the partition has through holes with a diameter of 50-200μm evenly distributed along the thickness direction, the through holes being filled with nano-silica particles.

[0009] This invention also discloses a preparation process for a lead-acid battery with gradient density active materials, the process of which is as follows: preparation of current collector → preparation of lead paste → application of paste → electrode curing → electrode formation, specifically including: Step 1: Use lead-calcium alloy or lead-calcium-tin alloy to form a mesh structure through wire drawing; Step 2: Mix solid raw materials, liquid raw materials, and additives to form a paste-like mixture; Step 3: Use a stepped pressure control method, with the current collector as the framework, and fill with lead paste with a gradient density distribution; Step 4: After drying in a room temperature and low humidity environment to remove free water from the lead paste, it is then heated and humidified to trigger a solid-phase reaction of the lead paste, forming a precursor of the active substance. Step 5: Immerse the cured electrode plate in dilute sulfuric acid electrolyte and connect it to a DC power supply to allow the electrode plate to undergo an electrochemical reaction, converting the precursor of the active material into the active material. Wash away the free sulfuric acid with deionized water and dry to obtain the electrode plate.

[0010] Preferably, the preparation process utilizes a paste mixing machine, a paste application device, a curing chamber, and a formation tank. The paste mixing machine is equipped with lead paste for both the positive and negative electrodes. The curing chamber promotes the dehydration and solidification of the lead paste, causing a solid-phase reaction to generate precursors of active substances. The formation tank provides an electrolyte environment and a DC electric field for the cured lead paste, converting the precursors of active substances into active substances through an electrochemical reaction. The paste application device includes a paste supply tank and a paste application mechanism. The paste application mechanism includes a supply manifold and several supply branch pipes. The supply manifold is connected to the paste supply tank, and the several supply branch pipes have the same diameter. The interior of the coating tunnel has several square seats arranged in a manner. The feed branch pipes are connected to the square seats from the upper and lower sides of the coating tunnel. A pair of facing cone plates are provided on the side of each square seat. The two cone plates form a coating taper (the taper refers to the angle at which the two cone plates converge towards the middle). A bending transition section is formed between the square seats and the cone plates through a bending process. The coating taper of the cone plates arranged in a straight line has a continuous gradient change. In step three, the stepped pressure control method is used in which the grid continuously passes through a pair of cone plates arranged according to the gradient change of the taper, and the coating is completed by the pressure of the cone plate ends on the grid.

[0011] Preferably, a pusher plate is slidably connected inside the paste supply tank, a hydraulic cylinder is provided at the top of the paste supply tank, the output end of the hydraulic cylinder is fixedly connected to the pusher plate, a feed pipe is connected to the outer wall of the paste supply tank, lead paste is added to the paste supply tank through the feed pipe, an air injection port is provided on the outer wall of the paste supply tank, an air plug is installed inside the air injection port, gas is filled into the lower part of the pusher plate through the air injection port to prevent the lead paste from contacting the pusher plate.

[0012] Preferably, the side of the cone plate is provided with reinforcing ribs, which are used to suppress the deformation of the cone plate under pressure. Both ends of the reinforcing ribs are provided with limiting rods, which control the distance between the openings of the two cone plates, thereby adjusting the taper of the paste application mechanism during paste application.

[0013] Preferably, in step four, gradient power microwave-assisted curing is used. The microwave emission source is arranged along the thickness direction of the electrode plate. The microwave power corresponding to the central region of the electrode plate is 300-500W, and the microwave power corresponding to the edge region is 100-200W. The microwave thermal effect accelerates the solid-phase reaction rate and densification degree of the lead paste in the central region, while suppressing excessive densification in the edge region.

[0014] Compared with the prior art, the beneficial effects of the present invention are: 1. In the battery of the present invention, by designing a gradient density distribution of active material along the thickness direction of the electrode plate, the high apparent density region in the middle can increase the number of active reaction sites per unit volume, thereby enhancing the battery energy density and high-rate charge and discharge performance; the porous structure of the low apparent density region at the edge can provide sufficient channels for ion migration, alleviate the problem of volume expansion and shedding of active material during charge and discharge cycles, and significantly extend the battery cycle life.

[0015] 2. In the preparation process of this invention, the gradient tapered paste coating mechanism combined with step-type pressure control accurately achieves gradient density molding of active materials. Combined with gradient power microwave-assisted curing, it further enhances the differentiated effect of densification in the middle of the electrode plate and retention of edge pores. The gas isolation and real-time pressure monitoring design of the paste supply tank avoids lead paste adhesion loss, improves the uniformity and controllability of paste coating, reduces material waste in the production process, adapts to the needs of large-scale mass production, and significantly improves production efficiency and product yield.

[0016] 3. In the preparation process of this invention, the paste coating mechanism optimizes the flow channel design through a bending transition section, and is reinforced with reinforcing ribs and limiting rods to effectively prevent the cone plate from deforming under pressure, ensuring the stability of the gradient taper and the accurate transmission of the paste coating pressure; the gradient temperature and humidity drying-curing process before formation, combined with the segmented current-controlled formation process, reduces the accumulation of lead sulfate crystals, improves the conversion efficiency of the active material precursor to the target active material, and at the same time reduces the residual stress inside the electrode plate, reduces the risk of electrode plate cracking during use, and further ensures the long-term cycle stability and performance consistency of the battery. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of a lead-acid battery with gradient density active material according to the present invention; Figure 2 This is a simplified diagram of the positive and negative electrode structures of a lead-acid battery with gradient density active material according to the present invention. Figure 3 This is an overall process flow diagram of the preparation process of a lead-acid battery with gradient density active material according to the present invention. Figure 4 This is a schematic diagram of the coating equipment used in the preparation process of a lead-acid battery with gradient density active material according to the present invention. Figure 5 This is a schematic diagram of the paste supply tank in the preparation process of a lead-acid battery with gradient density active material according to the present invention. Figure 6 This is a schematic diagram of the paste-coating mechanism in the preparation process of a lead-acid battery with gradient density active material according to the present invention. Figure 7 This is a process flow diagram of the paste coating mechanism in the preparation process of a lead-acid battery with gradient density active material according to the present invention.

[0018] In the diagram: 1. Positive electrode plate; 11. Grid; 102. Positive electrode active material; 13. Tab; 14. Connecting bridge; 2. Negative electrode plate; 202. Negative electrode active material; 3. Separator; 4. Battery casing; 41. Casing cover; 42. Electrolyte filling port; 43. Compartment; 5. Paste mixing machine; 6. Paste application equipment; 61. Paste supply tank; 611. Push plate; 612. Hydraulic cylinder; 613. Air injection port; 614. Feed pipe; 62. Paste application mechanism; 621. Feed manifold; 622. Feed branch pipe; 623. Square base; 624. Bending transition section; 625. Conical plate; 626. Reinforcing rib; 627. Limiting rod; 628. Paste application tunnel; 7. Curing chamber; 8. Formation tank. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Example 1: Refer to Figure 1-2 As shown: A lead-acid battery with gradient density active material includes a positive electrode plate 1, a negative electrode plate 2, and a battery casing 4. The positive electrode plate 1 and the negative electrode plate 2 are arranged in parallel and staggered to form electrodes. A separator 3 is provided between the staggered positive electrode plate 1 and the negative electrode plate 2. A grid 11 is provided at the center of both the positive electrode plate 1 and the negative electrode plate 2. The positive electrode plate 1 is composed of the central grid 11 and positive active material 102 filled on both sides. The negative electrode plate 2 is composed of the central grid 11 and negative active material 202 filled on both sides. The distribution of the positive active material 102 and the negative active material 202 is such that it changes in a gradient along the thickness direction of the positive electrode plate 1, and the apparent density in the central region is greater than that in the edge region. The battery casing 4 is filled with an electrolyte. The electrolyte acts as an ion transport medium to conduct ions to complete the charge migration inside the battery, forming a complete current loop with the electron flow of the positive electrode plate 1 and the negative electrode plate 2.

[0021] A cover 41 is installed at the top of the battery casing 4. The interior of the battery casing 4 has multiple equally spaced compartments 43. An electrolyte filling port 42 is located directly above each compartment 43 on the surface of the cover 41, and the electrolyte filling port 42 is sealed with a plug. A tab 13 is installed at the top of the grid 11. Connecting bridges 14 connect the tabs 13 with the same electrode polarity. Several positive electrode plates 1 and negative electrode plates 2 form a battery unit, which is installed inside the compartment 43. Battery units in adjacent compartments 43 are connected in series via the connecting bridges 14, and a set of connecting bridges 14 at both ends passes through the cover 41 to form electrode contacts. The separator 3 is made of ultra-fine glass fiber cotton and polypropylene composite. The separator 3 has a thickness of 1.2–1.8 mm. Through holes with a diameter of 50–200 μm are evenly distributed along the thickness direction inside the separator 3, and these through holes are filled with nano-silica particles.

[0022] In this embodiment, the core design highlight lies in the gradient density distribution of the positive electrode active material 102 and the negative electrode active material 202, as well as the synergistic adaptation of the composite modified separator 3. The high apparent density of active material in the central region of the electrode plate can increase the number of active reaction sites per unit volume, thereby enhancing the energy density and charge / discharge rate performance of the battery; the low apparent density of active material in the edge region has a richer pore structure, which can provide sufficient channels for ion migration during charge / discharge cycles, alleviate the problem of volume expansion and shedding of active material, and significantly extend the cycle life of the battery.

[0023] Meanwhile, the separator 3, made of ultra-fine glass fiber cotton and polypropylene composite, has a thickness of 1.2-1.8mm, which balances mechanical support strength and ion conduction efficiency. The 50-200μm through-pores evenly distributed inside, combined with the nano-silica particles, can not only significantly improve the adsorption and storage capacity of the electrolyte and accelerate the migration rate of hydrogen ions and sulfate ions, but also effectively block the risk of micro-short circuit between the positive and negative plates and inhibit the growth and penetration of lead dendrites, further improving the safety performance and cycle stability of the battery.

[0024] The battery casing 4 features equally spaced compartments 43, allowing for the independent installation and series connection of multiple battery cells. This ensures voltage consistency between cells and facilitates easy replenishment and maintenance of the electrolyte in each compartment 43 via the electrolyte filling port 42 on the casing cover 41, reducing overall maintenance costs. The battery cells are connected in series via a wiring bridge 14, ensuring orderly connection of positive and negative terminals. The electrode contacts protrude from the casing cover 41, facilitating external assembly and use of the battery and adapting to power supply requirements in various scenarios.

[0025] Example 2: Refer to Figure 1-7The diagram illustrates a process for preparing a lead-acid battery with gradient density active materials. The process utilizes a paste mixing machine 5, a paste application device 6, a curing chamber 7, and a formation tank 8. The paste mixing machine 5 prepares lead paste for both the positive and negative electrodes. The curing chamber 7 promotes dehydration and solidification of the lead paste, leading to a solid-phase reaction that generates precursors for the active materials. The formation tank 8 provides an electrolyte environment and a DC electric field for the cured lead paste, converting the precursors into active materials through an electrochemical reaction. The paste application device 6 includes a paste supply tank 61 and a paste application mechanism 62. It includes a feeding manifold 621 and several feeding branch pipes 622. The feeding manifold 621 is connected to the paste supply tank 61. The several feeding branch pipes 622 have the same diameter. Several square seats 623 are arranged inside the paste tunnel 628. The feeding branch pipes 622 are connected to the square seats 623 from the upper and lower sides of the paste tunnel 628 respectively. A pair of facing cone plates 625 are provided on the side of the square seat 623. The two cone plates 625 form the paste taper. The square seat 623 and the cone plates 625 are bent to form a bending transition section 624.

[0026] The preparation process specifically includes: 1) A grid structure is made by stretching lead-calcium alloy or lead-calcium-tin alloy into a mesh.

[0027] 2) A paste-like mixture is prepared by mixing solid raw materials, liquid raw materials and additives.

[0028] 3) A stepped pressure control method is adopted, with the current collector as the skeleton and the lead paste with a gradient density is filled; The tapered taper of the cone plate 625 has a continuous gradient change. In step 3, a stepped pressure control method is adopted, in which the grid 11 continuously passes through a pair of cone plates 625 arranged according to the tapered gradient change, and the coating is completed by the pressure of the end of the cone plate 625 on the grid 11.

[0029] 4) After drying in a room temperature and low humidity environment, the free water in the lead paste is removed. Then, after heating and humidifying, the solid-phase reaction of the lead paste is triggered to form the precursor of the active substance. Gradient power microwave-assisted curing is used. The microwave emission source is arranged along the thickness direction of the electrode plate. The microwave power corresponding to the central region of the electrode plate is 300-500W, and the microwave power corresponding to the edge region is 100-200W. The microwave thermal effect accelerates the solid-phase reaction rate and densification degree of the lead paste in the central region, while inhibiting excessive densification in the edge region.

[0030] 5) Immerse the cured electrode plate in dilute sulfuric acid electrolyte and connect it to a DC power supply to allow the electrode plate to undergo an electrochemical reaction, converting the precursor of the active material into the active material. Wash away the free sulfuric acid with deionized water and dry to obtain the electrode plate.

[0031] In this embodiment, the overall process flow can be referred to the appendix. Figure 3 The instructions state that the solid raw materials (mainly Pb3O4 or PbO), liquid raw materials (35-40% concentration dilute sulfuric acid and deionized water), and additives (short fibers, strontium carbonate, and expanding agents) required for preparing lead paste are added to the paste mixing machine 5. After thorough mixing, the paste is replenished to the paste supply tank 61 and supplied to each square seat 623 in the paste coating mechanism 62. The grid 11 passes from one side of the paste coating tunnel 628 to the other side. After the paste is applied, it is placed in the curing chamber 7 for drying and curing. After curing, it is placed in the formation tank 8 and electrified to form active substances. In the diagram, the solid arrows represent the process flow of lead paste, and the hollow arrows represent the process flow of the grid 11 or electrode plate.

[0032] The active materials on the outer sides of the positive electrode plate 1 and the negative electrode plate 2 are different, and the lead paste used in the preparation process also differs to some extent. The main difference lies in the raw materials used during paste preparation. The solid phase raw material for the positive electrode is red lead (Pb3O4) or lead monoxide (PbO), the liquid phase raw material is 40% dilute sulfuric acid + deionized water, and the additives are short fibers (polyester fibers, to enhance adhesion) and strontium carbonate (to refine PbO2 grains). The solid phase raw material for the negative electrode is lead monoxide (PbO), the liquid phase raw material is 35% dilute sulfuric acid + deionized water, and the additives are an expanding agent (barium sulfate + carbon black + sodium lignin sulfonate, to prevent sponge Pb shrinkage and agglomeration) and short fibers. The precursor formed by the solidification of the positive electrode is tetrabasic lead sulfate (4PbO·PbSO4), and the precursor formed by the solidification of the negative electrode is tribasic lead sulfate (3PbO·PbSO4·H2O). The active materials formed in the final formation are also different. The active material of the positive electrode plate 1 is PbO2 crystal, while the active material of the negative electrode plate 2 is high-porosity sponge Pb.

[0033] The core process for preparing gradient density active material electrodes lies in paste application. This technical solution controls the gradient state of the active sites after paste application by adjusting the pressure. Specifically, several sets of paste application mechanisms 62 with different tapers are set up. The paste application mechanism 62 is connected to the bottom of the paste supply tank 61 through the feed manifold 621. Uncured lead paste is a non-Newtonian fluid, which exhibits fluid properties when subjected to shear force. The lead paste in the paste supply tank 61 is extruded outward after being pressurized and supplied to the square base 623 along each feed branch pipe 622. In this state, the lead paste exhibits fluid properties, so the thrust from the paste application mechanism 62 is equal. Then, the lead paste enters the chamber of the cone plate 625 from the chamber of the square seat 623. Under the action of constant thrust, the lead paste first forms a stable "plug flow" in the parallel flow channel of the square seat 623. After entering the narrow flow channel of the cone plate 625, it is affected by the convergence and compression of the flow channel, and the shear rate increases sharply. The total resistance changes from a single shear resistance to "shear resistance + tensile resistance", and the resistance continues to increase along the flow direction, ultimately achieving the densification of the lead paste.

[0034] Under constant thrust conditions, the taper of the cone plate 625 directly determines the degree of convergence of the flow channel. The larger the taper, the faster the flow channel converges, the greater the total resistance experienced by the lead paste, and the greater the final pressure of the paste flowing out of the narrow orifice. Based on the arrangement of active materials in the electrode plate required for the paste application process, multiple paste application mechanisms 62 are arranged in a row. An opening matching the shape of the grid 11 is opened at the center of the square base 623. The grid 11 passes through multiple paste application mechanisms 62 sequentially. Since the same mass of lead paste is simultaneously introduced into both sides of the square base 623, the lead paste from both sides simultaneously provides equal amounts of lead paste to the center. The pressure ensures that the grid 11 is in the middle position. When passing through the conical opening of the conical plate 625, the two conical plates 625 scrape the lead paste onto both sides of the grid 11. The first coating mechanism 62 has the largest taper, and the two conical plates 625 are closest to the middle. The conical plates 625 compact the lead paste and adhere it densely to the grid 11. The taper of the subsequent coating mechanisms 62 gradually decreases, and the applied lead paste becomes looser. The lead paste is coated multiple times on both sides of the grid 11. After passing through multiple coating mechanisms 62, the grid 11 is coated thicker and thicker, and the lead paste on its surface also changes in a gradient.

[0035] Example 3: According to Figure 3-7 As shown, a pusher plate 611 is slidably connected inside the paste supply tank 61. A hydraulic cylinder 612 is installed at the top of the paste supply tank 61, and the output end of the hydraulic cylinder 612 is fixedly connected to the pusher plate 611. A feed pipe 614 is connected to the outer wall of the paste supply tank 61, through which lead paste is added to the paste supply tank 61. An air injection port 613 is provided on the outer wall of the paste supply tank 61, and an air plug is installed inside the air injection port 613. Gas is filled into the area below the pusher plate 611 through the air injection port 613 to prevent the lead paste from contacting the pusher plate 611. A reinforcing rib 626 is provided on the side of the conical plate 625. The reinforcing rib 626 is used to suppress the deformation of the conical plate 625 under pressure. Limiting rods 627 are provided at both ends of the reinforcing rib 626. The opening distance between the two conical plates 625 is controlled by the limiting rods 627, thereby adjusting the taper of the paste application mechanism 62 during paste application.

[0036] In this embodiment, after the lead paste is prepared by the paste mixing machine 5, it is supplied to the paste supply tank 61 through the feed pipe 614. The feed manifold 621 is installed at the bottom of the paste supply tank 61. After the lead paste is pressurized by the push plate 611, it is transported from the feed manifold 621 to each seat 623. Air is injected into the paste supply tank 61 through the air injection port 613. When the push plate 611 returns to the top of the paste supply tank 61, gas is supplied to the area below the push plate 611. The gas fills the area above the lead paste and transmits the pressure between the push plate 611 and the lead paste, preventing lead paste from adhering to the push plate 611.

[0037] A pressure gauge is installed on the hydraulic cylinder 612 to obtain the magnitude of the thrust applied by the hydraulic cylinder 612 in real time, so as to control the pressure of the lead paste supplying material from the paste supply tank 61 to the paste application mechanism 62, and to coordinate the pressure adjustment of the subsequent paste application mechanism 62. A reinforcing rib 626 is provided on the side of the cone plate 625 to improve the overall structural stability of the paste application mechanism 62, prevent structural deformation when the internal lead paste is forced, stabilize the paste application pressure provided by the paste application mechanism 62, and control the distance between the two reinforcing ribs 626 through the limit rod 627. The taper size can be adjusted by means of threaded connection, which facilitates the adjustment of the gradient taper of each paste application mechanism 62, so as to achieve controllable paste density distribution.

[0038] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lead-acid battery of gradient density active material, comprising positive plates (1), negative plates (2) and a battery case (4), the positive plates (1) and the negative plates (2) being arranged in parallel and staggered to form electrodes, and a separator (3) being arranged between the positive plates (1) and the negative plates (2) arranged in mutual staggered manner, characterized in that: The positive plate (1) and the negative plate (2) are provided with the grid (11) at the center, the positive plate (1) is composed of the grid (11) at the center and the positive active material (102) filled on both sides, the negative plate (2) is composed of the grid (11) at the center and the negative active material (202) filled on both sides, the distribution state of the positive active material (102) and the negative active material (202) is that the density of the central region is greater than that of the edge region along the thickness direction of the positive plate (1); the inside of the battery shell (4) is filled with electrolyte, the charge migration in the battery is completed by the ion conduction through the electrolyte as the ion transmission medium, and the complete current loop is formed by cooperating the electron flow of the positive plate (1) and the negative plate (2).

2. A lead acid battery of graded density active material as claimed in claim 1 wherein: The top end of the battery shell (4) is provided with the shell cover (41), the inside of the battery shell (4) is provided with a plurality of compartments (43) with equal intervals, the surface of the shell cover (41) is provided with the electrolyte filling port (42) above each compartment (43), and the electrolyte filling port (42) is packaged by a sealing plug.

3. A lead acid battery of graded density active material as claimed in claim 1 wherein: The top end of the grid (11) is provided with the tab (13), the tabs (13) with the same electrode polarity are communicated, a plurality of the positive plates (1) and the negative plates (2) form a battery unit and are installed in the compartment (43), the battery units between the adjacent two compartments (43) are connected in series through the positive and negative electrodes of the tab (14), and a group of tabs (14) at both ends pass through the shell cover (41) to form the electrode contact.

4. A lead acid battery of graded density active material as claimed in claim 1 wherein: The separator (3) is made of superfine glass fiber cotton and polypropylene, the thickness of the separator (3) is 1.2-1.8mm, the separator (3) is uniformly distributed with through holes with a diameter of 50-200μm along the thickness direction, and the through holes are filled with nano silicon dioxide particles.

5. A process for the production of a lead-acid battery of a gradient density active mass, for the production of a lead-acid battery of a gradient density active mass according to any one of the preceding claims 1 to 4, characterized in that, The preparation process comprises the following steps: S1, using lead-calcium alloy or lead-calcium-tin alloy, a grid-shaped structure is formed by net forming; S2, a paste-like mixture is prepared by mixing solid-phase raw materials, liquid-phase raw materials and additives; S3, a stepwise pressure control method is used, the current collector is used as a skeleton, and the lead paste is filled with a gradient distribution of density; S4, after drying treatment in a normal temperature and low humidity environment, free water in the lead paste is removed, then the temperature is increased and the humidity is increased, the solid-phase reaction of the lead paste is triggered, and the precursor of the active material is formed; S5, the cured plate is immersed in dilute sulfuric acid electrolyte and connected to a direct current power supply, the plate is allowed to undergo electrochemical reaction as an electrode, the precursor of the active material is converted into active material, free sulfuric acid is washed away with deionized water, and the electrode plate is obtained after drying.

6. A process for the preparation of a lead acid battery of graded density active material as claimed in claim 5 wherein: The preparation process uses a paste mixing machine (5), a paste coating device (6), a curing chamber (7) and a formation tank (8), the paste mixing machine (5) is respectively configured for the lead paste of the positive and negative electrodes, the curing chamber (7) is used for promoting the lead paste to be dehydrated and shaped and to generate a precursor of the active material through a solid phase reaction, and the formation tank (8) provides an electrolyte environment and a direct current field for the cured lead paste, and the precursor of the active material is converted into the active material through an electrochemical reaction; The paste coating device (6) comprises a paste supply tank (61) and a paste coating mechanism (62), the paste coating mechanism (62) comprises a supply manifold (621), a plurality of supply branch pipes (622) and a paste coating tunnel (628), the supply manifold (621) is in communication with the paste supply tank (61), the pipe diameters of the plurality of supply branch pipes (622) are equal, a plurality of square seats (623) are arranged in the paste coating tunnel (628), the supply branch pipes (622) are respectively in communication with the square seats (623) from the upper and lower sides of the paste coating tunnel (628), one pair of taper plates (625) are arranged on the side of the square seat (623), the angles of the two taper plates (625) form a paste coating taper, and a bending excess section (624) is formed between the square seat (623) and the taper plate (625) through a bending process; The paste coating taper of the taper plate (625) changes continuously in a gradient manner, and in step S3, the stepwise pressure control method is that the grid (11) continuously passes through a plurality of taper plates (625) arranged in a pair according to the taper gradient, and the pressure of the end of the taper plate (625) on the grid (11) completes the paste coating.

7. A process for the preparation of a lead acid battery of graded density active material as claimed in claim 6 wherein: The inside of the paste supply tank (61) is slidably connected with a pushing plate (611), the top end of the paste supply tank (61) is provided with a hydraulic cylinder (612), the output end of the hydraulic cylinder (612) is fixedly connected with the pushing plate (611), the outer side wall of the paste supply tank (61) is in communication with a feeding pipe (614), the feeding pipe (614) is used for supplementing the lead paste in the paste supply tank (61), the outer side wall of the paste supply tank (61) is provided with a gas injection port (613), the inside of the gas injection port (613) is mounted with a gas plug, the gas injection port (613) is used for filling gas below the pushing plate (611) to separate the lead paste from the pushing plate (611).

8. A process for the preparation of a lead acid battery of graded density active material as claimed in claim 6 wherein: The side of the taper plate (625) is provided with a reinforcing rib (626), the reinforcing rib (626) is used for inhibiting the deformation of the taper plate (625) under pressure, and the two ends of the reinforcing rib (626) are both provided with a limiting rod (627), the opening distance of the two taper plates (625) is controlled through the limiting rod (627), so that the taper of the taper plate (625) during the paste coating is adjusted.

9. A process for the preparation of a lead acid battery of graded density active material as claimed in claim 5 wherein: In step S4, the solidification treatment is performed by gradient power microwave assistance. The microwave emission source is arranged along the thickness direction of the pole plate. The microwave power corresponding to the middle region of the pole plate is 300-500 W, and the microwave power corresponding to the edge region is 100-200 W. The microwave heat effect accelerates the solid-phase reaction rate and the densification degree of the lead paste in the middle region, and inhibits excessive densification in the edge region.

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