Two-dimensional material coated lead composite material and preparation method thereof, lead paste, electrode and lead-acid battery

Abstract

The present invention discloses a two-dimensional material-coated lead composite material, a preparation method thereof, a lead paste, an electrode, and a lead-acid battery. The preparation method comprises: a mixing step of mixing a MXene material with one or more of metallic lead, a metallic lead alloy, and a lead compound to obtain a mixture or composite; and a heating step of mixing a component A with the mixture or composite and then heating the mixture or composite, wherein the component A is a simple substance of element A, a hydride of element A, or a compound capable of reacting to generate a simple substance of element A or a hydride of element A, so that the MXene material and element A react to form a MAX phase structure. The two-dimensional material-coated lead composite material obtained by the present invention has a coating structure with a dense core and a fluffy, sealed shell. This effectively mitigates the integrity of the core-shell structure during the significant volume changes of the active material during the electrode material preparation process and the charge-discharge process, thereby ensuring the stability of the electrode material.

Description

Technical Field

[0001] The present invention belongs to the technical field of new materials and lead-acid batteries, and in particular relates to a two-dimensional material-coated lead composite material and a preparation method thereof, a lead paste, an electrode and a lead-acid battery. Background Art

[0002] Lead-acid batteries, with their high cost-effectiveness, high recycling rate, and superior safety, hold the largest market share and are the most widely used secondary battery in the battery market, particularly in electric bicycles and energy storage. Despite over 150 years of history, lead-acid batteries still suffer from issues such as negative electrode sulfation, low positive electrode conductivity, softening and shedding, and grid corrosion. Most of these issues stem from the significant volume change (>100%) during the conversion of lead powder to lead sulfate during charge and discharge. For example, dense lead powder in the negative electrode transforms into spongy lead sulfate, while dense lead dioxide in the positive electrode transforms into fluffy lead sulfate. Such large volume changes can, on the one hand, lead to the pulverization of active materials and their shedding from the grid, resulting in a shorter cycle life for lead-acid batteries. On the other hand, they can also lead to significant contact resistance between active materials, severely hampering the lead-acid battery's rate performance and low-temperature performance. In order to improve the electrochemical performance of lead-acid batteries, some additives are usually added to the positive and negative electrodes and pastes, such as carbon-containing components such as graphite, graphene, carbon fiber, or inorganic materials such as short fibers. Their addition can partially improve the initial performance of the battery, but with long-term circulation, lead sulfate will still grow on its own, resulting in a decrease in the structural strength of the active material and / or the grid, and a shortened battery life. Summary of the Invention

[0003] The purpose of the present invention is to address the problem of large volume changes of active materials in lead-acid battery electrodes during charging and discharging, and to provide a novel two-dimensional material-coated lead composite material and a preparation method thereof. Based on the excellent softness of the two-dimensional material MXene, lead powder, an electrode material for a lead-acid battery, is coated, and a portion of the MXene material is bonded through a heating step to achieve bonding and encapsulation of the electrode material, thereby obtaining a two-dimensional material-coated lead composite material with a stable coating structure; the coating structure has a dense core, a fluffy shell and a partially blocked structure, which can effectively alleviate the huge volume changes of the lead powder when it is converted into lead sulfate during charging and discharging, and effectively prevent the growth and aggregation of non-conductive lead sulfate crystals, thereby improving the conductivity of the entire electrode, and improving the cycle life, rate performance and low-temperature performance of the lead-acid battery.

[0004] A first aspect of the present invention provides a method for preparing a two-dimensional material-coated lead composite material, comprising the following steps:

[0005] Mixing step: mixing the MXene material with one or more of metallic lead, metallic lead alloy, and lead compound to obtain a mixture or composite;

[0006] Heating step: Component A is mixed with the above mixture and then heated, wherein the component A is a simple substance of element A, a hydride of element A, or a compound that can react to generate the simple substance of element A or the hydride of element A, so that part of the MXene material reacts with element A to form a MAX phase structure, thereby realizing the bonding and encapsulation of the MXene material to the lead or lead compound.

[0007] In some embodiments, the chemical formula of the MXene material is represented by M n+1 X n T x , wherein M is selected from one or more transition metal elements, X is selected from one or more carbon, nitrogen or boron elements, T x Represents a functional group, including one or more of -F, -Cl, -Br, -I, -O, -S, -OH, -NH4, 1≤ n ≤4.

[0008] In some embodiments, the element A is selected from one or more of aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), iron (Fe), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), cadmium (Cd), indium (In), tin (Sn), lead (Pb), bismuth (Bi), and antimony (Sb).

[0009] In some embodiments, M in the above MXene material is selected from at least one of titanium (Ti), vanadium (V), molybdenum (Mo), niobium (Nb), tantalum (Ta), tungsten (W), and chromium (Cr).

[0010] In some embodiments, in the heating step, the element A is selected from tin (Sn) and / or silicon (Si).

[0011] In some embodiments, in the heating step, the element A is selected from tin (Sn).

[0012] In some embodiments, the mixing step more specifically includes: dispersing the MXene material with one or more of metallic lead, metallic lead alloy, and lead compound in a solvent, and then drying to obtain a mixture.

[0013] In some embodiments, a carbon material is further added in the mixing step, and the carbon material includes one or more of graphene, graphite, carbon nanotubes, porous carbon, and carbon fiber.

[0014] In some embodiments, the lead compound is selected from one or more of basic lead sulfate, lead sulfate, lead oxide, and red lead.

[0015] In some embodiments, in the mixing step, the amount of the MXene material added is in a range of 0.01 wt.% to 90 wt.% by mass; preferably, 0.5 wt.% to 20 wt.%; and more preferably, 1 wt.% to 3 wt.%.

[0016] In some embodiments, in the heating step, the reaction temperature of the heating treatment is between 200°C and 1000°C; preferably, between 600°C and 800°C.

[0017] In some embodiments, in the heating step, the heating treatment time is between 0.1 h and 100 h; preferably, between 6 h and 20 h.

[0018] The second aspect of the present invention provides a two-dimensional material-coated lead composite material, which includes a coating layer and a core, wherein the core is one or more of metallic lead, metallic lead alloy, and lead compound, and the coating layer is a MXene material.

[0019] In some embodiments, a MAX phase structure is also present in the above-mentioned two-dimensional material-coated lead composite material, and the MAX phase structure is obtained by heating a portion of the MXene material and component A, wherein the component A is a simple substance of element A, a hydride of element A, or a compound that can react to generate the simple substance of element A or the hydride of element A.

[0020] In some embodiments, the above-mentioned A element is selected from one or more of aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), iron (Fe), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), cadmium (Cd), indium (In), tin (Sn), lead (Pb), bismuth (Bi), and antimony (Sb). The heat treatment allows the MXene material to react with the A element to form the MAX phase structure, thereby realizing the bonding and encapsulation of the MXene material to the lead or lead compound.

[0021] In some embodiments, the two-dimensional material-coated lead composite material further comprises: a carbon material, wherein the carbon material comprises: one or more of graphene, graphite, carbon nanotubes, porous carbon, and carbon fiber.

[0022] In some embodiments, the lead compound is selected from one or more of basic lead sulfate, lead sulfate, lead oxide, and red lead.

[0023] In some embodiments, the amount of the MXene material added to the two-dimensional material-coated lead composite material is in a mass percentage range of 0.01 wt.% to 90 wt.%; preferably, 0.5 wt.% to 20 wt.%; more preferably, 1 wt.% to 3 wt.%.

[0024] In some embodiments, the coating layer has a thickness ranging from 0.3 nm to 20 μm; preferably, from 1 nm to 50 nm.

[0025] In some embodiments, the thickness of the MAX phase structure is between 0.3 nm and 2 μm.

[0026] The third aspect of the present invention provides a method for preparing a two-dimensional material-coated lead composite material, the steps comprising: mixing a MXene material with one or more of metallic lead, metallic lead alloy, and lead compound in a solution, and filtering and drying the mixture.

[0027] A fourth aspect of the present invention provides a two-dimensional material-coated lead composite material prepared by the above-mentioned preparation method, or the use of the above-mentioned two-dimensional material-coated lead composite material as an electrode material for a lead-acid battery.

[0028] A fifth aspect of the present invention provides a lead paste for a lead-acid battery, including a positive electrode lead paste or a negative electrode lead paste, wherein the lead paste contains the two-dimensional material-coated lead composite material prepared by the above-mentioned preparation method, or the above-mentioned two-dimensional material-coated lead composite material.

[0029] The sixth aspect of the present invention provides a method for preparing the above-mentioned lead paste, comprising the following steps: mixing the two-dimensional material-coated lead composite material and auxiliary materials to obtain a dry material mixture; adding water and sulfuric acid solution to the dry material mixture and stirring to obtain a wet material mixture; and allowing the wet material mixture to solidify to obtain the lead paste.

[0030] The seventh aspect of the present invention provides an electrode for a lead-acid battery, including a positive electrode or a negative electrode, which electrode contains the two-dimensional material-coated lead composite material prepared by the above-mentioned preparation method, or the above-mentioned two-dimensional material-coated lead composite material.

[0031] An eighth aspect of the present invention provides a lead-acid battery comprising the above-mentioned electrode.

[0032] A ninth aspect of the present invention provides an electric vehicle comprising the above-mentioned lead-acid battery.

[0033] The beneficial technical effect of the present invention is that:

[0034] 1. The two-dimensional material-coated lead composite material and its preparation method provided by the present invention utilize the excellent softness of the two-dimensional material MXene to coat lead powder, a lead-acid battery electrode material. The excess two-dimensional MXene after coating is then bonded and encapsulated to form a MAX phase structure through bonding, thereby obtaining a two-dimensional material-coated lead composite material. The coating structure has a dense core and a fluffy, sealed shell. This unique coating structure differs from previously reported two-dimensional material coating structures because the two-dimensional MXene is converted into a dense MAX phase structure with strong bonding, resolving the problem of the two-dimensional material being easily damaged and collapsed during volume changes in traditional two-dimensional material coating structures. This effectively mitigates the integrity of the core-shell structure during the significant volume changes of the active material during the electrode material preparation process and the charge-discharge process, thereby ensuring the stability of the electrode material.

[0035] 2. The MXene and MAX phase structures in the two-dimensional material-coated lead composite material provided by the present invention both have excellent electrical conductivity and a two-dimensional layered structure. The two-dimensional material-coated lead composite material of the present invention can be used as an electrode material for a lead-acid battery, thereby further facilitating the function of a conductive agent. In particular, the two-dimensional layered structure can effectively change the point-to-point contact mode of conventional granular conductive agents. The structure of the two-dimensional material-coated active material enables the conductive mode between the active material and the conductive agent to be a surface-to-surface contact mode, thereby greatly improving the conductivity of the electrode material. This not only improves the conversion efficiency of the active material during the formation process, but also improves the conductivity of the entire electrode, thereby enhancing the rate performance and cycle stability of lead-acid batteries.

[0036] 3. The two-dimensional material-coated lead composite material provided by the present invention has excellent corrosion resistance and oxidation resistance. It is not easily oxidized and corroded in the positive or negative electrode of a lead-acid battery and in the environment of a sulfuric acid electrolyte. While improving the conductivity of the lead-acid battery, it can also ensure the stability of the lead-acid battery electrode, avoiding the permanent loss of battery energy density and cycle life caused by oxidation and corrosion of the lead-acid battery electrode; in particular, the MAX phase material containing tin and silicon groups generated after the encapsulation reaction also has good bonding performance with the lead-based grid, preventing the shedding of active substances; even if it is oxidized on the surface, the product tin dioxide still has high conductivity, ensuring that the entire electrode has high conductivity.

[0037] 4. The two-dimensional material-coated lead composite material provided by the present invention also has a high specific surface area and high strength. While increasing its contact area and porosity with the positive electrode lead paste, it also enhances the electrode strength, solves the problem of easy softening and falling off of lead-acid battery electrodes, and improves the life and rate performance of lead-acid batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1The MXene material Ti3C2T prepared in Example 1 of the present invention x XRD spectrum of

[0039] Figure 2 This is a TEM image of the MAX phase Ti3SnC2 bonded and blocked MXene-coated lead powder composite material prepared in Example 1 of the present invention;

[0040] Figure 3 The spherical aberration electron micrograph (a) and the corresponding structural schematic (b) of the MAX phase Ti3SnC2 end-capping portion generated by the bonding reaction of the two-dimensional material MXene in the two-dimensional material MXene-coated lead composite material in Example 1 of the present invention are shown;

[0041] Figure 4 This is a schematic diagram of the structure of the two-dimensional material MXene coated lead or lead compound particles of the present invention;

[0042] Figure 5 This is a photo of the solution containing acetylene black, CNTs, and MXene.

[0043] Figure 6 The MXene material Ti3C2Cl prepared in Example 2 of the present invention x XRD spectrum of

[0044] Figure 7 : This is a spherical aberration electron microscopy photograph of the MAX phase structure obtained by reacting Al and MXene in Example 2 of the present invention and a schematic diagram of the corresponding atomic structure;

[0045] Figure 8 XRD spectra of the MAX phase structure obtained by the synthesis reaction of different MXene materials and element A in Example 5 of the present invention;

[0046] Figure 9 These are photos of the positive electrode paste prepared and the positive electrode coated with the positive electrode paste in Example 7 of the present invention. DETAILED DESCRIPTION

[0047] The technical solutions of the present invention are described below by means of specific embodiments. It should be understood that one or more steps mentioned in the present invention do not exclude the presence of other methods and steps before and after the combination step, or other methods and steps may be inserted between these explicitly mentioned steps. It should also be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Unless otherwise specified, the numbering of each method step is only for the purpose of identifying each method step, and does not limit the order of arrangement of each method or the scope of implementation of the present invention. Changes or adjustments in their relative relationships can also be regarded as the scope of implementation of the present invention without substantial changes in the technical content.

[0048] The sources of the raw materials and instruments used in the examples are not particularly limited and can be purchased from the market or prepared according to conventional methods known to those skilled in the art.

[0049] The lead powder components commonly used in lead-acid batteries in the art include metallic lead and lead oxide, or powder of partially oxidized metallic lead.

[0050] The technical concept of the present invention is based on the applicant's previous discovery that MXene materials and elemental A or compounds containing A can undergo a reverse synthesis reaction to form a MAX phase structure (recorded in patent application number 202110557381.3). The applicant uses this synthesis reaction from MXene materials to form a MAX phase structure for the bonding and encapsulation of electrode materials (lead powder) in lead-acid batteries, resulting in a unique MXene material coating and a two-dimensional material-coated lead composite material with a MAX phase structure encapsulation, and uses this composite material as an electrode material for lead-acid batteries. The following specific examples illustrate the technical features of the present invention:

[0051] Example 1

[0052] This embodiment provides a two-dimensional material coated lead composite material and a preparation method thereof, wherein the MXene material is Ti3C2T x The preparation comprises the steps of:

[0053] (1) Weigh 200 mL of concentrated hydrochloric acid and place it in a plastic beaker. Weigh 10 g of LiF and slowly add it to the concentrated hydrochloric acid while stirring the solution with a magnet. Weigh 10 g of the raw material MAX phase - Ti3AlC2 and slowly add it to the hydrochloric acid-LiF solution. Maintain the reaction temperature at 30°C and the stirring speed at 500 rpm. The reaction is carried out for 24 hours.

[0054] (2) The reactant obtained in step 1 was washed with deionized water until the pH reached 6, and the obtained product was ultrasonically peeled off and centrifuged at 3000 rpm to obtain the upper liquid to obtain a MXene dispersion.

[0055] The steps of preparing the two-dimensional material-coated lead powder of the present invention include:

[0056] (3) 100 g of lead powder for lead-acid batteries is measured and uniformly dispersed in the MXene dispersion obtained in step 2. The mixture is stirred mechanically or ultrasonically, and then filtered and dried to obtain a mixture of MXene-coated lead powder. The coating thickness can be adjusted by adding different mass ratios of lead powder and MXene. In some embodiments, the preparation ratio of MXene in the mixture can be adjusted in the range of 0.01 wt.% to 90 wt.%. When the two-dimensional material-coated lead composite material of the present invention is used as an electrode material for a lead-acid battery, the mass ratio of the MXene material is preferably between 0.1 wt.% and 10 wt.%, more preferably between 0.5 wt.% and 5 wt.%, and even more preferably between 1 wt.% and 3 wt.%, that is, the mass ratio of the active material is increased as much as possible. In this embodiment, the mass ratio of MXene is about 1 wt.%.

[0057] (4) A mixture of Sn element (tin powder) and MXene-coated lead powder obtained in step 3 was placed in a tube furnace at a molar ratio of 1:10 for reaction. The mixture was heated to 700°C under the protection of argon and kept warm for 10 hours. After the reaction was completed, the mixture was naturally cooled to room temperature to obtain a MAX phase Ti3SnC2 bonded and blocked MXene-coated lead composite material.

[0058] Figure 1 This is the XRD test result of MXene material obtained by etching with hydrochloric acid-fluoride salt method. Figure 1 It can be seen that the MXene material presents a diffuse characteristic peak, which is related to the etching of Al element in Ti3AlC2 to generate a lamellar structure of Ti3C2T x , which leads to the expansion of the interlayer spacing; Figure 2 This is the transmission electron microscope (TEM) photograph of the MXene-coated lead powder composite material with MAX phase Ti3SnC2 bonded segments. It can be seen that the coating structure of the lead particles coated with MXene material also has a bonded MAX phase structure on the coating layer. Figure 3 The spherical aberration electron micrograph (a) and the corresponding atomic structure diagram (b) of the MAX phase Ti3SnC2 end-capping portion generated by the bonding reaction of the two-dimensional material MXene are further given, which clearly shows the MAX phase material structure of the bonded end-capping after the reaction of part of the MXene material with element A. Since the MAX phase structure is synthesized from MXene materials with at least two layers of two-dimensional sheets, the MAX phase structure can also maintain a two-dimensional sheet morphology, that is, a two-dimensional MAX phase structure end-capping is obtained. The thickness of the MAX phase structure is related to the number of layers of MXene materials involved in the synthesis reaction. Figure 3 The photo shows two layers of MXene material (Ti3C2T x) and element A atoms, the thickness of the MAX phase structure obtained by synthesizing the multilayer MXene material and element A atoms is about 2~3nm; in other embodiments, the thickness of the MAX phase structure obtained by the reaction of multilayer MXene materials and element A atoms can be between 0.3nm and 20μm. Figure 4 A schematic diagram of a two-dimensional material-coated lead composite material is provided, showing a core-shell structure model. The lead particles are coated with a soft MXene material. The overlapping edges of the MXene material also contain a MAX phase structure, which enables bonding and encapsulation of the MXene-coated lead particles, thereby improving the stability of the coating structure. It should be noted that the schematic diagram shows a spherical core. In specific embodiments, the present invention focuses on the coating structure and does not limit the shape of the core. As long as the composite material contains a MXene-coated structure, it is within the scope of the present invention.

[0059] The MXene material and the lead powder are preferably mixed in a solution. Figure 5 The photo shows the effect of mixing lead powder (yellow) for lead-acid batteries with conductive carbon black (acetylene black), carbon nanotubes (CNTs) and MXene materials in aqueous solution. It can be seen that the solution with MXene added has obvious stratification of water and black precipitate. The black precipitate is a composite of MXene-coated lead powder. In contrast, obvious yellow lead powder can still be observed in the solution with acetylene black and CNTs added. No yellow lead powder can be seen in the solution with MXene added. This is because the two-dimensional material MXene has the characteristics of softness, high specific surface area, and negative charge on the surface. It will self-assemble on the surface of the lead powder with positive charge in the solution to form a coating structure. The black precipitate is washed, collected and dried to obtain a composite material of two-dimensional material MXene-coated lead powder.

[0060] Example 2

[0061] This embodiment provides another two-dimensional material coated lead composite material and its preparation method, wherein the MXene material is Ti3C2Cl x The preparation comprises the steps of:

[0062] (1) Ti3SiC2, CuCl2, NaCl, and KCl were weighed in a molar ratio of 1:3:2:2, and the above substances were placed in an agate mortar and ground uniformly to obtain a mixture;

[0063] (2) The mixture obtained in step 1 was placed in a tube furnace and heated, and argon was introduced as a protective gas. The reaction temperature was maintained at 750 ° C and the reaction time was 24 hours. After the reaction was completed and the temperature was naturally cooled, the product was taken out and washed clean, and dispersed in N-methylpyrrolidone (NMP) solvent to obtain MXene-Ti3C2Cl x Organic dispersion.

[0064] The steps of preparing the two-dimensional material-coated lead composite material of the present invention include:

[0065] (3) 100 g of lead powder for lead-acid batteries was measured and uniformly dispersed in the MXene organic dispersion obtained in step 2. The mixture was stirred mechanically or ultrasonically, and then filtered and dried to obtain a mixture of MXene-coated lead powder. The coating thickness can be adjusted according to the different mass ratios of lead powder and MXene. In this embodiment, the mass proportion of MXene is 3 wt.%.

[0066] (4) A mixture of Al element (aluminum powder) and the MXene-coated lead powder obtained in step 3 was placed in a tube furnace at a molar ratio of 1:10 for reaction. The mixture was heated to 700°C under the protection of argon and kept warm for 10 hours. After the reaction was completed, the mixture was naturally cooled to room temperature to obtain a MAX phase Ti3AlC2 bonded and terminated MXene-coated lead powder material.

[0067] Figure 6 The MXene material Ti3C2Cl obtained by molten salt etching in this example is given. x The XRD spectrum of Figure 5 It can be seen that the MXene material presents a diffuse characteristic peak, which is related to the etching of the Al element in Ti3AlC2 to generate a lamellar structure of Ti3C2Cl2, resulting in an increase in the interlayer spacing. Figure 7 Shown is a spherical aberration electron microscope photograph of the MAX phase structure obtained after the reaction of Al element and MXene and the corresponding atomic structure schematic diagram. It can be seen that the MAX phase material structure was successfully synthesized by multi-layer MXene material and Al element atoms.

[0068] It should be noted that the lead powder in the present invention can be a powder of metallic lead alone or a powder of a metallic lead alloy.

[0069] Example 3

[0070] This embodiment provides another two-dimensional material coated lead composite material and its preparation method, wherein the MXene material Ti3C2T x The preparation was the same as in Example 1.

[0071] The steps of preparing the two-dimensional material-coated lead powder of the present invention include:

[0072] (1) 5 g of carbon nanotubes were measured and evenly dispersed in 200 mL of MXene dispersion to obtain a MXene mixed dispersion.

[0073] (2) 100 g of lead powder for lead-acid batteries was measured and evenly dispersed in the MXene mixed dispersion obtained in step 1. The mixture was stirred mechanically or ultrasonically, and then filtered and dried to obtain MXene-coated lead powder. The coating thickness can be adjusted according to the different mass ratios of lead powder and MXene.

[0074] (4) The Sn element and the MXene-coated lead powder obtained in step 3 were placed in a tube furnace at a molar ratio of 1:10 for reaction. The mixture was heated to 700 °C under the protection of argon and kept warm for 10 hours. After the reaction was completed, the mixture was naturally cooled to room temperature to obtain a MXene-coated lead powder material with MAX phase Ti3SnC2 bonded and blocked.

[0075] In another preferred embodiment, the heating temperature is 800 degrees and the holding time is 12 hours.

[0076] This embodiment obtains a modified two-dimensional material-coated lead composite material containing carbon material. In another embodiment, the carbon material added in step 1 can also be replaced by one or more of graphene, graphite, porous carbon, and carbon fiber; the electrochemical properties or mechanical properties of the two-dimensional material-coated lead composite material of the present invention are further improved by adding carbon materials with one-dimensional or two-dimensional morphology.

[0077] Example 4

[0078] This embodiment provides another two-dimensional material-coated lead composite material. The preparation method is similar to that of the embodiment, except that the lead powder in Example 1 is replaced with lead oxide (PbO2) powder to obtain a two-dimensional material-coated lead oxide composite material.

[0079] In other embodiments, the lead powder in Example 1 can also be replaced by other types of lead compounds, such as one or more of basic lead sulfate, lead sulfate, lead oxide, and red lead; or, a mixture of lead powder and these lead compounds to obtain a composite material in which a two-dimensional material is coated with two or more lead-containing materials.

[0080] Example 5

[0081] This embodiment provides two-dimensional material-coated lead composite materials synthesized from several different MXene materials and element A.

[0082] In one embodiment, the preparation method is similar to that of Example 1, except that in step 4 of Example 1, the Sn element (tin powder) is replaced with the Ga element (gallium powder), and the resulting bonded-terminated MAX phase structure is Ti3GaC2.

[0083] In one embodiment, the preparation method is similar to that of Example 1, except that in step 4 of Example 1, the Sn element (tin powder) is replaced with the Ge element (germanium powder), and the resulting bonded-terminated MAX phase structure is Ti3GeC2.

[0084] In one embodiment, the preparation method is similar to that of Example 1, except that the raw material MAX phase material in step 1 is Ti2AlC, and the MXene material obtained after etching is Ti2CT x The bonded and terminated MAX phase structure obtained is Ti2SnC.

[0085] In one embodiment, the preparation method is similar to that of Example 1, except that the raw material MAX phase material in step 1 is Ti2AlC, and the MXene material obtained after etching is Ti2CT x ; In step 4, the Sn element (tin powder) is replaced with the Ge element (germanium powder), and the resulting bonded and terminated MAX phase structure is Ti2GeC.

[0086] Figure 8 The XRD spectra of Ti3GaC2, Ti3GeC2, Ti2SnC and Ti2GeC with the two-dimensional MAX phase structures prepared above are given respectively. The characteristic peaks of the MAX phase structure can be seen in their XRD spectra. At the same time, compared with traditional MAX phase materials, these characteristic peaks are relatively diffuse, which is related to the fact that the obtained MAX phase structure maintains the ultra-thin two-dimensional morphology.

[0087] In this embodiment, element A is Sn, Ga, and Ge as an example. In other embodiments, element A can also be replaced by an element. For example, element A is selected from one or more of aluminum (Al), silicon (Si), phosphorus (P), sulfur (S), iron (Fe), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), cadmium (Cd), indium (In), tin (Sn), lead (Pb), bismuth (Bi), and antimony (Sb). These elements are all A component elements in the MAX phase material. Under certain reaction conditions, they can also undergo a synthetic reaction with the MXene material to achieve bonding and packaging of the coating structure.

[0088] It should be noted that in this embodiment, the MXene material undergoes a synthesis reaction with a simple substance (powder) of element A, but the synthesis reaction is not limited to the simple substance of element A. The MXene material can also react with the hydride of A, as well as other compounds that can react to generate a simple substance of element A or a hydride of element A.

[0089] In a specific embodiment, in one implementation, the preparation method is similar to that of Example 1, except that in step 4 of Example 1, the Sn element (tin powder) is replaced with aluminum hydride (AlH3), and the resulting bonded and terminated MAX phase structure is Ti3AlC2.

[0090] Example 6

[0091] This embodiment provides a lead paste for a lead-acid battery, more specifically a positive electrode lead paste, which comprises, by weight: 50-90 parts of the two-dimensional material-coated lead composite material of the present invention; 0.1-20 parts of tetrabasic lead sulfate; 3-15 parts of sulfuric acid solution, 0-2 parts of fiber material, and 5-20 parts of water.

[0092] In a preferred embodiment, the positive electrode lead paste comprises, in parts by weight: 70-90 parts of the two-dimensional material-coated lead composite material of the present invention, 0.1-20 parts of tetrabasic lead sulfate, 3-15 parts of sulfuric acid solution, 0-2 parts of fiber material, and 5-20 parts of water.

[0093] In another preferred embodiment, the positive electrode lead paste comprises, in parts by weight: 70-90 parts of two-dimensional material-coated lead powder, 0.1-10 parts of tetrabasic lead sulfate, 3-10 parts of sulfuric acid solution, 0-2 parts of fiber material, and 5-20 parts of water.

[0094] The preparation method comprises the following steps: mixing the two-dimensional material-coated lead composite material of the present invention, tetrabasic lead sulfate, and fiber material to obtain a dry material mixture; adding water and sulfuric acid solution to the dry material mixture and stirring and mixing to obtain a wet material mixture; and placing the wet material mixture for curing to obtain a composite positive electrode lead paste.

[0095] In a more specific embodiment, the steps include:

[0096] (1) Dry auxiliary material preparation step: pre-mixing the tetrabasic lead sulfate of the present invention and the fiber material to form a dry auxiliary material;

[0097] (2) Wet mixing step: adding deionized water to the mixture of the dry auxiliary material obtained in step 1 and the two-dimensional material-coated lead powder, stirring and wet mixing to obtain a slurry;

[0098] (3) Acid mixing step: adding dilute sulfuric acid to the wet-mixed slurry for acid mixing; preferably, the acid mixing time is between 10 and 20 minutes;

[0099] (4) Curing step: The acid-mixed slurry is cooled and cured to obtain the positive electrode lead paste.

[0100] The obtained positive electrode lead paste is coated on the metal grid and in the gaps, and is cured and dried at high temperature to prepare the positive electrode of the lead-acid battery.

[0101] In a specific embodiment, the positive electrode lead paste uses the two-dimensional material-coated lead composite material obtained in Example 1, which includes, by weight: 80 parts of the two-dimensional material-coated lead composite material, 10 parts of tetrabasic lead sulfate, 3 parts of sulfuric acid solution, 1 part of fiber material, and 6 parts of water.

[0102] Example 7

[0103] To illustrate the effectiveness of the two-dimensional material-coated lead composite material of the present invention as an electrode material in a lead-acid battery, the positive lead paste in this embodiment is composed of the following raw materials by weight: 8 parts sulfuric acid solution, 7.2 parts dry auxiliary materials (6 parts tetrabasic lead sulfate + 1.2 parts fiber material), 10 parts deionized water, and 80 parts of the two-dimensional material-coated lead composite material. The specific implementation steps for preparing the positive lead paste are the same as those in Example 6. The preparation method of the two-dimensional material-coated lead composite material is similar to that in Example 1. During the heat treatment step, the two-dimensional material-coated lead composite material reacts with tin powder, aluminum powder, and silicon powder to obtain a two-dimensional material-coated lead composite material with MAX phase structures Ti3SnC2, Ti3AlC2, and Ti3SiC2 bonded and terminated.

[0104] The resulting positive lead paste was applied to the lead-calcium-tin-aluminum metal grid and its interstices, then cured and dried at high temperature to produce the positive electrode for a lead-acid battery. Electrodes obtained using the same formula, but coated with different two-dimensional materials, were assembled into lead-acid batteries to test their electrochemical performance. Figure 9 Photos of the prepared positive electrode lead paste and the positive electrode coated with the positive electrode lead paste are given. The positive electrode lead paste appears viscous and can be easily scraped onto a metal grid, making it suitable for industrial scale-up production.

[0105] Comparative Example 1

[0106] The two-dimensional material-coated lead composite material in the positive electrode lead paste in Example 7 was replaced by a mixture of conductive carbon black and lead powder, wherein the mass proportion of the conductive carbon black was the same as that of the MXene material, and the comparative sample 1 electrode was obtained by the same method.

[0107] Comparative Example 2

[0108] The two-dimensional material-coated lead composite material in the positive electrode lead paste in Example 7 is replaced by: a mixture of the MXene material and lead powder prepared in steps 1 to 3 in Example 1, that is, a mixture of MXene material coated with lead powder but not heat-treated for bonding and capping, which is equivalent to only van der Waals force capping between the MXene material layers.

[0109] The positive and negative electrodes of the lead-acid batteries prepared in Example 7 and Comparative Examples 1 and 2 were assembled into full lead-acid batteries to test battery performance. The lead-acid battery assembly method includes: adding a glass fiber separator with sulfuric acid electrolyte absorbed into the prepared positive and negative electrodes of the lead-acid batteries to assemble them into single cells, and connecting multiple single cells in parallel according to the test capacity requirements. The test method includes: connecting the assembled lead-acid batteries to a charge and discharge instrument, determining the test rate (0.2C~2C) and the test temperature (room temperature~-10 o C) The electrochemical cycle performance and capacity were tested at a certain rate and temperature. The test results are shown in Table 1 below.

[0110] Example 8

[0111] This embodiment provides a negative electrode lead paste and a preparation method thereof, wherein the negative electrode lead paste comprises, in parts by weight: 50-90 parts of two-dimensional material-coated lead powder, 0.1-20 parts of graphene, 3-15 parts of sulfuric acid solution, 0-2 parts of fiber material, and 5-20 parts of water.

[0112] In a preferred embodiment, the negative electrode lead paste comprises, in parts by weight: 70-90 parts of two-dimensional material-coated lead powder, 0.1-20 parts of graphene, 3-15 parts of sulfuric acid solution, 0-2 parts of fiber material, and 5-20 parts of water.

[0113] In another preferred embodiment, the negative electrode lead paste comprises, in parts by weight: 70-90 parts of two-dimensional material-coated lead powder, 0.1-10 parts of graphene, 3-10 parts of sulfuric acid solution, 0-2 parts of fiber material, and 5-20 parts of water.

[0114] The preparation method comprises the following steps: mixing two-dimensional material-coated lead powder, graphene, and fiber material to obtain a dry material mixture; adding water and sulfuric acid solution to the dry material mixture and stirring and mixing to obtain a wet material mixture; and placing the wet material mixture for curing to obtain a composite negative electrode lead paste.

[0115] In a more specific embodiment, the steps include:

[0116] 1. Dry auxiliary material preparation step: pre-mix the graphene and fiber material evenly to prepare dry auxiliary material;

[0117] 2. Wet mixing step: adding deionized water to the mixture of the dry auxiliary material obtained in step 1 and the two-dimensional material-coated lead powder, stirring and wet mixing to obtain a slurry;

[0118] 3. Acid mixing step: adding dilute sulfuric acid to the wet-mixed slurry for acid mixing; preferably, the acid mixing time is between 10 and 20 minutes;

[0119] 4. Curing step: The acid-mixed slurry is cooled and cured to obtain the negative electrode lead paste.

[0120] The obtained negative electrode lead paste is coated on the metal grid and in the gaps, and is cured and dried at high temperature to prepare the negative electrode of the lead-acid battery.

[0121] In a specific embodiment, the positive electrode lead paste uses the two-dimensional material-coated lead composite material obtained in Example 1, which includes, by weight: 80 parts of the two-dimensional material-coated lead composite material, 2 parts of graphene, 3 parts of sulfuric acid solution, and 15 parts of water.

[0122] Example 9

[0123] To illustrate the effectiveness of the two-dimensional material-coated lead composite material of the present invention as an electrode material in a lead-acid battery, the negative electrode lead paste in this example is composed of the following raw materials by weight: 8 parts sulfuric acid solution, 7.2 parts dry auxiliary materials (6 parts graphene + 1.2 parts fiber material), 10 parts deionized water, and 80 parts of the two-dimensional material-coated lead composite material. The specific steps for preparing the negative electrode lead paste are the same as those in Example 8. The preparation method of the two-dimensional material-coated lead composite material is similar to that in Example 1. During the heat treatment step, the two-dimensional material-coated lead composite material reacts with tin powder, aluminum powder, and silicon powder, respectively, to obtain a two-dimensional material-coated lead composite material with MAX phase structures, Ti3SnC2, Ti3AlC2, and Ti3SiC2 bonded and terminated.

[0124] The resulting negative electrode lead paste was applied to the lead-calcium-tin-aluminum metal grid and its interstices, then cured and dried at high temperature to form the positive electrode for a lead-acid battery. Using the same formulation, negative electrodes coated with different two-dimensional materials, including the lead composite material and paste, were assembled into lead-acid batteries for electrochemical performance testing. The negative electrode lead paste exhibited similar properties to the positive electrode lead paste, exhibiting a viscous consistency that allowed for easy scraping onto the metal grid, making it suitable for industrial scale-up.

[0125] Comparative Example 3

[0126] The two-dimensional material-coated lead composite material in the negative electrode lead paste in Example 9 was replaced by a mixture of conductive carbon black and lead powder, wherein the mass proportion of the conductive carbon black was the same as that of the MXene material, and the comparative sample 1 electrode was obtained by the same method.

[0127] Comparative Example 4

[0128] The two-dimensional material-coated lead composite material in the negative electrode lead paste in Example 9 is replaced by: a mixture of the MXene material and lead prepared in steps 1 to 3 in Example 1, that is, a mixture of MXene material coated with lead powder but not heat-treated for bonding and capping, which is equivalent to only van der Waals force capping between the MXene material layers.

[0129] The lead-acid battery negative electrode and positive electrode prepared in the above Example 9, and Comparative Examples 3 and 4 were assembled into a lead-acid full battery to test the battery performance. The lead-acid battery assembly and testing methods were similar to those for the positive electrode. The test results are shown in Table 2 below.

[0130] Table 1. Electrochemical performance test results of lead-acid battery positive electrodes with lead powder coated with different two-dimensional materials

[0131]

[0132] Table 2. Electrochemical performance test results of lead-acid battery negative electrodes coated with lead powder using different two-dimensional materials

[0133]

[0134] It can be seen from the test results in Tables 1 and 2 that the electrochemical properties of the positive or negative electrode coated with the MAX phase-capped two-dimensional material MXene, including internal resistance, capacity, cycle life and low-temperature performance, are significantly better than those of the electrode coated with the uncapped two-dimensional material MXene (Comparative Examples 2 and 4) and the electrode with conductive carbon black as the conductive agent (Comparative Examples 1 and 3).

[0135] Due to the MAX phase capping, the coating structure of the 2D MXene-coated lead powder in the present invention has a dense core and a fluffy, sealed shell. This unique coating structure differs from previously reported 2D material coating structures because the 2D MXene is converted into a dense MAX phase structure with strong bonding, resolving the problem of susceptibility to damage and collapse of the 2D material during volume changes in traditional 2D material coating structures. This effectively mitigates the integrity of the core-shell structure during the significant volume changes of the active material during electrode material preparation and charge-discharge processes, thereby ensuring the stability of the electrode material.

[0136] It can also be seen that among the composite materials with different MAX phase bonded terminations, the tin-based bonded termination (Ti3SnC2) two-dimensional material MXene coated with lead powder exhibits the best electrochemical performance. This can be explained by the good compatibility between the metal tin element and the lead element, which can enable the two-dimensional MAX phase material to be evenly dispersed in the positive electrode material. At the same time, since the two-dimensional MAX phase material has better compatibility and bonding properties with the lead powder or lead compounds and lead grids in the lead-acid battery, it can also prevent the shedding of active substances and improve the stability of the positive electrode plate. In addition, when the surface of this type of tin-based two-dimensional MAX phase material is oxidized, the product is tin dioxide (SnO2), which also has good conductivity, which can ensure that the positive electrode still maintains good conductivity after long-term cycling.

[0137] It can also be seen that the two-dimensional material MXene-coated lead powder (van der Waals force capping) composite material can improve the electrochemical performance of the electrode compared with conventional conductive carbon black. This can be explained by the fact that the MXene itself has excellent conductivity and also has a two-dimensional layered structure, which can effectively change the point-point contact mode of traditional granular conductive agents; the structure of the two-dimensional material-coated active substance can make the conductive mode between the active substance and the conductive agent a surface-surface contact mode, which greatly improves the conductivity of the electrode material, not only improving the conversion efficiency of the active substance in the formation process, but also improving the conductivity of the entire electrode, and improving the rate performance and cycle stability of lead-acid.

[0138] Example 10

[0139] This embodiment provides another specific implementation of a positive electrode lead paste and a preparation method thereof, which is similar to Example 7, except that two-dimensional material MXene-coated lead powder (silicon-based bonded end-capping) and carbon nanotubes are added.

[0140] In this example, the positive electrode paste is composed of the following raw materials, by weight: 4 parts sulfuric acid solution, 6 parts dry auxiliary materials, 10 parts deionized water, and 80 parts of MXene-coated lead powder (silicon-terminated). The dry auxiliary materials include 2 parts carbon nanotubes and 4 parts tetrabasic lead sulfate. The specific steps for preparing the positive electrode paste are the same as those in Example 6. The resulting positive electrode paste is applied to the lead-calcium-tin-aluminum metal grid and into the gaps therein. The resulting positive electrode paste is then cured and dried at high temperature to prepare the positive electrode for a lead-acid battery.

[0141] Example 11

[0142] This embodiment provides another specific implementation of a negative electrode lead paste and a preparation method thereof, which is similar to Example 9, except that the negative electrode lead powder is a two-dimensional material MXene-coated lead powder (aluminum-based bonded end-capping).

[0143] In this example, the negative electrode paste is composed of the following raw materials, by weight: 5 parts sulfuric acid solution, 5 parts dry auxiliary materials, 10 parts deionized water, and 80 parts MXene-coated lead powder (aluminum-based bonded blockade). The dry auxiliary materials include 2 parts barium sulfate, 1 part sodium lignin sulfonate, and 1 part CMC. The specific steps for preparing the negative electrode paste are the same as those in Example 8. The resulting negative electrode paste is applied to the lead-calcium metal grid and the gaps therein, then cured and dried at high temperature to prepare the negative electrode for the lead-acid battery.

[0144] Example 12

[0145] This embodiment provides another implementation method of two-dimensional MXene-coated lead powder, and the specific steps include:

[0146] (1) Mechanically stirring and mixing MXene material powder and lead powder to obtain a mixture powder;

[0147] (2) Add component A to the powder of the mixture in step 1 above, stir and mix mechanically, and then heat treat to allow element A to react with the MXene material to form a MAX phase structure for bonding and end-capping.

[0148] In this embodiment, the powders are directly mixed, thus avoiding the steps of dispersion and drying in the solvent, simplifying the process flow and being suitable for large-scale industrial production. x Mix with lead powder in a mass ratio of 1: (1~10), and then add Ti3C2T x The Sn powder is added to the mixture powder at a molar ratio of 1: (0.1-0.5), and the mixture is stirred and mixed. The mixture is placed in a high-temperature reactor under an Ar atmosphere and kept at 800° C. for 12 h. The mixture is taken out after natural cooling to obtain the MXene-coated lead powder composite material of the present invention.

[0149] In a preferred embodiment, Ti3C2T x Mixed with lead powder in a mass ratio of 1:9, Ti3C2T x : Sn powder molar ratio is 1: 0.2.

[0150] The two-dimensional material-coated lead composite material of the present invention can be used as an electrode material for a lead-acid battery, resulting in a lead-acid battery with excellent performance. The present invention also encompasses electric vehicles, including electric bicycles, electric motorcycles, and electric cars, that use this lead-acid battery as an energy storage unit. The lead-acid battery of the present invention may also be used in other modes of transportation, such as start-stop power supplies for automobiles and ships.

[0151] The foregoing descriptions of specific exemplary embodiments of the present invention are for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that many variations and modifications are possible in light of the foregoing teachings. The exemplary embodiments have been selected and described for the purpose of explaining the specific principles of the invention and their practical application, thereby enabling those skilled in the art to realize and utilize a variety of exemplary embodiments of the invention and various options and modifications. The scope of the invention is intended to be defined by the claims and their equivalents.

Claims

1. A method for preparing a two-dimensional material-coated lead composite material, characterized in that: The preparation method comprises the following steps: Mixing step: mixing the MXene material with one or more of metallic lead, metallic lead alloy, and lead compound to obtain a mixture or composite; Heating step: mixing component A with the mixture or composite and then heating the mixture or composite, wherein component A is a simple substance of element A, a hydride of element A, or a compound that can react to generate a simple substance of element A or a hydride of element A, so that the MXene material reacts with the element A to form a MAX phase structure, thereby obtaining a MXene material as a coating layer and a two-dimensional material-coated lead composite material containing a MAX phase structure.

2. The preparation method according to claim 1, wherein The chemical formula of the MXene material is represented by M n+1 X n T x , wherein M is selected from one or more transition metal elements, X is selected from one or more carbon, nitrogen or boron elements, T x Represents a functional group, including one or more of -F, -Cl, -Br, -I, -O, -S, -OH, -NH4, 1≤ n ≤4; And / or, the element A is selected from one or more of aluminum, silicon, phosphorus, sulfur, iron, copper, zinc, gallium, germanium, cadmium, indium, tin, lead, bismuth, and antimony.

3. The preparation method according to claim 2, wherein The M is selected from at least one of titanium, vanadium, molybdenum, niobium, tantalum, tungsten and chromium; And / or, the element A is selected from tin and / or silicon.

4. The preparation method according to claim 2, wherein The element A is selected from tin.

5. The preparation method according to claim 1, wherein The mixing step more specifically includes: dispersing the MXene material and one or more of the metal lead, metal lead alloy, and lead compound in a solvent, mixing the mixture, and then drying the mixture to obtain the mixture; And / or, in the mixing step, a carbon material is further added, wherein the carbon material includes one or more of graphene, graphite, carbon nanotubes, porous carbon, and carbon fiber; and / or, in the mixing step, the lead compound is selected from one or more of basic lead sulfate, lead sulfate, lead oxide, and red lead; And / or, in the mixing step, the amount of the MXene material added to the mixture is between 0.01 wt.% and 90 wt.% by mass.

6. The preparation method according to claim 5, wherein The addition amount of the MXene material is between 0.5 wt.% and 20 wt.% by mass.

7. The preparation method according to claim 6, wherein The addition amount of the MXene material is between 1 wt.% and 3 wt.% by mass.

8. The preparation method according to any one of claims 1 to 7, characterized in that In the heating step, the heating temperature is between 200°C and 1000°C; And / or, in the heating step, the heating time is between 0.1h and 100h.

9. The preparation method according to claim 8, wherein The heating temperature is between 600° C. and 800° C.; And / or, the heating time is between 6h and 20h.

10. A two-dimensional material-coated lead composite material, characterized in that: The two-dimensional material-coated lead composite material includes: a coating layer and a core, the core is one or more of metallic lead, metallic lead alloy, and lead compound, and the coating layer is a MXene material; the two-dimensional material-coated lead composite material also has a MAX phase structure, and the MAX phase structure is obtained by heating the MXene material and component A, and the component A is a simple substance of element A, a hydride of element A, or a compound that can generate the simple substance of element A or the hydride of element A through reaction.

11. The two-dimensional material-coated lead composite material according to claim 10, characterized in that: The element A is selected from one or more of aluminum, silicon, phosphorus, sulfur, iron, copper, zinc, gallium, germanium, cadmium, indium, tin, lead, bismuth, and antimony; And / or, the two-dimensional material-coated lead composite material further comprises: a carbon material, wherein the carbon material comprises: one or more of graphene, graphite, carbon nanotubes, porous carbon, and carbon fiber; And / or, the lead compound is selected from one or more of basic lead sulfate, lead sulfate, lead oxide, and red lead; and / or, in the two-dimensional material-coated lead composite material, the mass percentage of the MXene material is between 0.01 wt.% and 90 wt.%; and / or, the coating layer has a thickness ranging from 0.3 nm to 20 μm; And / or, the thickness of the MAX phase structure is between 0.3 nm and 2 μm.

12. The two-dimensional material-coated lead composite material according to claim 11, wherein: The mass percentage of the MXene material is between 0.5 wt.% and 20 wt.%; And / or, the coating layer has a thickness ranging from 1 nm to 50 nm.

13. The two-dimensional material-coated lead composite material according to claim 11, characterized in that: The mass percentage of the MXene material is between 1 wt.% and 3 wt.%.

14. A method for preparing the two-dimensional material-coated lead composite material according to claim 10, characterized in that: The steps of the preparation method include: The MXene material is mixed with one or more of metallic lead, metallic lead alloy, and lead compound in a solution, and then filtered and dried to obtain the result.

15. A two-dimensional material-coated lead composite material prepared by the preparation method according to any one of claims 1 to 9; or, a two-dimensional material-coated lead composite material according to any one of claims 10 to 13; or, use of the two-dimensional material-coated lead composite material obtained by the preparation method according to claim 14 as a lead-acid battery electrode material.

16. A lead paste for a lead-acid battery, comprising a positive electrode lead paste or a negative electrode lead paste, characterized in that: The lead paste contains a two-dimensional material-coated lead composite material prepared by the preparation method as described in any one of claims 1 to 9; or, a two-dimensional material-coated lead composite material as described in any one of claims 10 to 13; or, a two-dimensional material-coated lead composite material obtained by the preparation method as described in claim 14.

17. A method for preparing the lead paste according to claim 16, characterized in that the steps include: mixing the two-dimensional material-coated lead composite material and auxiliary materials to obtain a dry material mixture; adding water and sulfuric acid solution to the dry material mixture and stirring to obtain a wet material mixture; The wet material mixture is placed and solidified to obtain the lead paste.

18. An electrode for a lead-acid battery, comprising a positive electrode or a negative electrode, characterized in that: The electrode contains a two-dimensional material-coated lead composite material prepared by the preparation method as described in any one of claims 1 to 9; or, a two-dimensional material-coated lead composite material as described in any one of claims 10 to 13; or, a two-dimensional material-coated lead composite material obtained by the preparation method as described in claim 14.

19. A lead-acid battery, characterized in that: Containing the electrode according to claim 18.

20. An electric vehicle, characterized in that: Contains the lead-acid battery as claimed in claim 19.

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