Lead storage battery, CNT reinforced lead-based grid thereof, preparation method and application of CNT reinforced lead-based grid

Abstract

The invention belongs to the field of lead-acid batteries, and particularly relates to a lead storage battery and a CNT reinforced lead-based grid, a preparation method and application thereof, and the preparation method of the CNT reinforced lead-based grid comprises the following steps: mixing CNT and lead powder to obtain a mixture; the mixture is pressed and formed and then subjected to microwave sintering in the protective gas atmosphere, and a carbon nano tube-lead composite middle prefabricated block is obtained; and adding the CNT-lead composite intermediate precast block into molten lead liquid, carrying out ultrasonic cavitation treatment, and then carrying out pouring molding, so as to obtain the CNT reinforced lead-based grid. According to the method disclosed by the invention, the strength and toughness of the material are remarkably improved, the material has excellent mechanical properties, and the excellent discharge current density and super-long cycle life of the lead-acid storage battery can be improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrochemical cell manufacturing, in particular to a lead-acid battery grid. BACKGROUND

[0002] In traditional lead-acid batteries, the positive plate is much more damaged than the negative plate due to overcharging (being in an oxidized state) or severe oxygen evolution, etc. Therefore, improving the performance of the positive plate is an indispensable link to improve the overall performance of the lead-acid battery. The introduction of carbon nanotubes can effectively reduce lead oxide impurities and inhibit grid oxidation during grid hot processing, while also exerting its high electrical conductivity and dispersion strengthening effect on lead alloy, thereby improving the electrochemical performance and mechanical properties of the positive grid, and thus providing an effective way to improve the performance of lead-acid batteries.

[0003] For example, the patent document with publication number CN114094112A discloses casting a positive grid by co-melting carbon nanotubes with a positive alloy, which has good corrosion inhibition effect, reduces the corrosion rate of the grid, and to some extent, improves the hydrogen evolution potential, thereby significantly improving the corrosion resistance. However, in this invention, carbon nanotubes are directly co-melted with lead alloy, which easily causes oxidation and uneven dispersion. The patent document with publication number CN112614980A discloses adding carbon nanotubes and graphene to the positive lead paste and covering the lead paste on the grid blank to obtain a graphene lead-carbon battery positive grid. The composite grid has strong charge acceptance and long service life, which is superior to ordinary lead-carbon battery positive grids and significantly better than ordinary lead-acid battery positive plates. However, in this invention, only the lead paste is modified with carbon nanotubes, and the grid part is not involved, which cannot improve the mechanical properties of the positive plate. SUMMARY

[0004] To solve the problems of existing lead-acid battery grids, the present application provides a preparation method of CNT reinforced lead-based grid, aiming to solve the problem of unsatisfactory CNT reinforcement performance caused by the mismatch between CNT and lead material structure.

[0005] The second object of the present application is to provide a CNT reinforced lead-based grid prepared by the preparation method and its application in lead-acid batteries.

[0006] The third object of the present application is to provide a lead-acid battery containing the CNT reinforced lead-based grid.

[0007] The carbon nanotubes (CNT) are introduced into the lead-based composite system as a reinforcing phase, and compared with the traditional carbon material, the particularity mainly embodies two aspects: one is that the CNT is expected to build a continuous three-dimensional conductive network in the lead matrix by virtue of the extremely high aspect ratio and excellent intrinsic conductivity, so as to significantly improve the conductivity and structural strength of the composite material; the other is that the interface wettability and easy agglomeration between the CNT and the lead matrix constitute a new technical challenge to be overcome. Specifically, the huge specific surface area and surface energy of the CNT make it easy to agglomerate due to van der Waals force in the lead matrix, and it is difficult to achieve uniform dispersion, which not only limits the play of its reinforcing effect, but even deteriorates the electrical properties of the material due to the incomplete conductive network. At the same time, the poor wettability between the CNT and the lead matrix leads to weak interfacial bonding, which hinders the effective transmission of electrons at the interface, and may become a crack source in the service process, affecting the mechanical stability and durability of the composite material. In addition, how to realize the uniform dispersion and stable combination of the CNT in the high-density and low-activity lead matrix by a feasible process method without seriously damaging the structure of the CNT itself under the premise of accurately controlling the distribution and orientation of the CNT in the matrix is a new process problem to be solved for preparing high-performance CNT / lead composite materials.

[0008] In view of the problems of CNT strengthening lead, the present application provides the following solutions after in-depth research:

[0009] The preparation method of the CNT reinforced lead grid, comprising the following steps:

[0010] Step 1:

[0011] The CNT and lead powder are mixed to obtain a mixture; the mixture is pressed and molded, and then microwave sintering is carried out in a protective gas atmosphere to obtain a carbon nanotube-lead composite intermediate preform block;

[0012] Step 2:

[0013] The carbon nanotube-lead composite intermediate preform block is added to the molten lead liquid, and ultrasonic cavitation treatment is carried out, and then cast molding is carried out to obtain the CNT reinforced lead grid.

[0014] In view of the problems of poor materialization adaptability of lead and difficulty in composite reinforcement of lead grid caused by special physicochemical structure of CNT (carbon nanotube), the application innovatively performs microwave sintering on CNT and lead powder in advance, which helps to improve the interface structure of CNT and lead, improve the deep composite of lead, and reduce the oxidation of lead, and then the CNT reinforced lead grid with excellent interface adaptability can be prepared by ultrasonic cavitation and pouring of the CNT as a reinforcing material and lead liquid. The lead grid prepared by the preparation method has excellent mechanical properties, and the strength and toughness of the material are significantly improved. Meanwhile, the conductivity and interface stability are also greatly improved. The key is to realize the synergistic improvement of conductivity, mechanical strength and electrochemical activity at a very low addition amount, effectively inhibit the shedding of active material and corrosion of grid, so as to endow the lead-acid battery with excellent discharge current density and super-long cycle life.

[0015] In the application, in step 1, the weight ratio of CNT and lead powder is 10-40:1.

[0016] In the application, in step (1), the mixing process is carried out in a protective atmosphere.

[0017] Preferably, the mixing method is mechanical ball milling.

[0018] Preferably, the rotation speed of mechanical ball milling is 250-400 r / min, and further can be 300-350 r / min.

[0019] Preferably, the ball-to-material ratio of the mechanical ball milling process is 5-30:1, and considering the cost, it can be further 10-15:1.

[0020] Preferably, the mechanical ball milling time is 1-10 h, and further can be 1-5 h.

[0021] Preferably, a low-speed mechanical ball milling process at a rotation speed of 50-200 r / min is further carried out before mechanical ball milling; the low-speed mechanical ball milling time is 0.2-3 h, and further can be 0.5-1 h. In the application, the CNT and lead powder are pre-mixed by the preferred gradient ball milling process, which can further improve the interface adaptability of CNT and lead powder, and help to further strengthen the discharge current density and super-long cycle life of the lead-acid battery.

[0022] In the application, the microwave sintering process is carried out in a protective atmosphere.

[0023] Preferably, the microwave sintering temperature is 280-600℃, and further can be 300-350℃.

[0024] Preferably, the microwave power of microwave sintering is 500-2000 W, and further can be 1000-1500 W.

[0025] Preferably, the holding time of microwave sintering is 10-30 minutes.

[0026] In the present application, in step 2, the lead liquid is a molten solution obtained by heating and melting the lead-containing raw material;

[0027] Preferably, the melting temperature is above 400℃;

[0028] Preferably, the lead liquid further comprises calcium-aluminum alloy;

[0029] Preferably, the weight ratio of lead to calcium-aluminum alloy in the lead liquid is 75-90:0.1-1;

[0030] In step 2, the lead is first melted at 400-500℃, then the calcium-aluminum alloy is added, and the temperature is further increased to 600-650℃ to melt the calcium-aluminum alloy, thereby obtaining the lead liquid.

[0031] In the present application, the weight of the carbon nanotube-lead composite intermediate preform block is 5-30% of the weight of the lead liquid (a solution comprising lead and optionally calcium-aluminum alloy), and further 10-20%.

[0032] In the present application, the frequency of ultrasonic cavitation is 20-40 kHz, the ultrasonic power is 1000-3000 W, and the action time is 5-15 minutes.

[0033] The present application also provides a CNT reinforced lead grid prepared by the method.

[0034] In the present application, the preparation method can endow the prepared CNT reinforced lead grid with special physicochemical structure, and the CNT reinforced lead grid prepared by the preparation method has excellent performance.

[0035] The present application also provides an application of the CNT reinforced lead grid prepared by the method, which is used as a positive electrode to prepare a lead-acid storage battery.

[0036] The present application also provides a lead-acid storage battery comprising the CNT reinforced lead grid prepared by the method.

[0037] The lead-acid storage battery of the present application comprises the CNT reinforced lead grid of the present application, and other components and parts can be known.

[0038] Advantages

[0039] 1. The present application provides a brand new carbon nanotube reinforced lead-based composite material, and it is found that the material can refine the grain, promote dispersion strengthening, effectively enhance the mechanical properties of the positive plate grid, and improve the tensile strength and elongation of the plate grid in the field of lead-acid storage batteries.

[0040] The carbon nanotube-lead composite intermediate preform prepared by the application has similar appearance to lead ingot, has the characteristics of anti-oxidation and storage resistance, can be directly added with calcium-aluminum alloy in lead-acid battery industrial production, does not need to change production equipment and production line, and is beneficial to quickly realize industrial production of new lead storage battery.

[0041] 2, The application innovatively pre-sintering CNT and lead powder by microwave, which helps to improve the interface structure of CNT and lead, improve the deep composite of lead, reduce the oxidation of lead, and then ultrasonic cavitation and pouring with lead liquid as reinforcing material, so as to prepare CNT reinforced lead grid with excellent interface matching. The grid prepared by the preparation method has excellent mechanical properties.

[0042] 3, The raw materials of the application are easy to obtain, the process is simple, the environmental pollution is small, the preparation process does not use liquid, there is no pollution emission, the raw materials can be recycled, the preparation method has good repeatability, the reaction conditions are mild and easy to operate. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 The SEM images of the carbon nanotube-lead composite intermediate preform (a, b) before sintering and (c, d) after sintering prepared for the embodiment 1 of the application.

[0044] Figure 2 The XRD images of the carbon nanotube-lead composite intermediate preform before sintering and after sintering prepared for the embodiment 1 of the application. DETAILED DESCRIPTION

[0045] In order to better understand the application, the following examples are further illustrated, but the scope of protection of the application is not limited to the scope indicated by the examples.

[0046] The application provides a preparation method of the CNT reinforced lead grid, which comprises the following steps:

[0047] Step (1): uniformly mixing carbon nanotubes and lead powder in a protective gas atmosphere, and then loading into a ball mill tank for mechanical ball milling in a protective gas atmosphere to obtain carbon nanotube-lead composite powder;

[0048] Step (2): microwave sintering the carbon nanotube-lead composite powder after compression molding in a protective gas atmosphere to obtain a carbon nanotube-lead composite intermediate preform;

[0049] Step (3): heating lead to 400-500 DEG C to melt lead, adding calcium-aluminum alloy, heating to 600-650 DEG C to melt, adding carbon nanotube-lead composite intermediate preform, and ultrasonic cavitation stirring and mixing uniformly to quickly pour to prepare carbon nanotube reinforced lead-based composite material.

[0050] In step (1), the lead powder and carbon nanotubes are subjected to low-speed ball milling (50-200 r / min) in a ball mill to make them flaky, and then subjected to high-speed ball milling (250-400 r / min) to cause cold welding and promote interface bonding;

[0051] In step (1), the ball-to-material ratio during ball milling is 5-30:1.

[0052] In step (1), the high-speed ball milling time is 1-10 h.

[0053] In step (2), the sintering process is performed by microwave sintering.

[0054] Preferably, in step (2), the sintering process is performed under a protective atmosphere, such as at least one of nitrogen gas and argon gas.

[0055] Preferably, in step (3), the melting process is assisted by ultrasonic cavitation stirring to enhance the dispersibility and interface bonding of the carbon nanotubes.

[0056] Example 1

[0057] a. Preparation of carbon nanotube-lead composite powder;

[0058] a1. 18 parts by weight of lead powder and 2 parts by weight of multi-walled carbon nanotubes are pre-dispersed in a mechanical fusion system.

[0059] a2. 20 parts by weight of the composite powder from step a1 after pre-dispersion is loaded into a stainless steel vacuum ball mill jar (ball-to-material weight ratio 10:1), and low-speed ball milling is performed at a speed of 100 r / min for 30 min in a planetary ball mill under argon atmosphere protection to obtain low-speed milled material.

[0060] a3. The low-speed milled material is subjected to high-speed ball milling at a speed of 300 r / min for 1 h under argon atmosphere protection, and the composite powder is obtained after ball milling and sieving, and is placed in argon atmosphere protection.

[0061] b. Preparation of carbon nanotube-lead composite intermediate preform;

[0062] b1. The high-speed milled material sample from step a3 is cold-pressed at a pressure of 20 MPa for 5 min in an isostatic pressing device to obtain a green body.

[0063] b2. The green body product after cold pressing in step b1 is transferred to a microwave sintering furnace, and microwave sintering is performed under argon atmosphere protection, with the microwave power set to 1000 W, and the temperature is rapidly raised to 300°C, and the temperature is maintained for 15 min before cooling down with the furnace to obtain a carbon nanotube-lead composite intermediate preform.

[0064] c. Carbon nanotube reinforced lead-based composite material is prepared;

[0065] c1. 79.85 parts by weight of lead is heated to 450℃ to melt, 0.15 parts by weight of calcium-aluminum alloy (weight ratio of calcium to aluminum is 1:1) is added, and the temperature is raised to 600℃ to melt, obtaining a lead-based grid alloy melt;

[0066] c2. 20 parts by weight of the intermediate preform block prepared in step b2 is added to the 80 parts by weight of the lead-based grid alloy melt obtained in step c1, and the temperature is kept at 600℃ to melt completely by ultrasonic cavitation assisted stirring (ultrasonic frequency 30 kHz, power 1500 W, action 10 minutes), and the ingot is rapidly cooled to obtain a carbon nanotube reinforced lead-based composite material.

[0067] Example 2

[0068] Compared with Example 1, the only difference is that in step a1: single-walled carbon nanotubes are used to replace multi-walled carbon nanotubes, and other operations and parameters are the same as those in Example 1.

[0069] Example 3

[0070] Compared with Example 1, the only difference is that in step a1: the parts by weight of lead powder and multi-walled carbon nanotubes are 16:4 respectively, and the total amount of lead powder and multi-walled carbon nanotubes and other operations and parameters are the same as those in Example 1.

[0071] Example 4

[0072] Compared with Example 1, the only difference is that in step a2, the rotation speed of low-speed ball milling is 150 r / min, and the time is 40 min; in step a3: the rotation speed of high-speed ball milling is 350 r / min, and the time is 3 h, and other operations and parameters are the same as those in Example 1.

[0073] Example 5

[0074] Compared with Example 1, the only difference is that in step b2: the microwave sintering power is 1500 W, the holding temperature is 330℃, and the processing time is 13 min, and other operations and parameters are the same as those in Example 1.

[0075] Example 6

[0076] Compared with Example 1, the only difference is that in step c2: the ultrasonic cavitation condition is power 1500 W, action 10 minutes, and other operations and parameters are the same as those in Example 1.

[0077] Example 7

[0078] Compared with Example 1, the only difference is that in step c1: the weight ratio of lead in the lead-based grid alloy melt and calcium-aluminum alloy is 89:1, and the weight ratio of the lead-based grid alloy melt and the preform is 90:10, and other operations and parameters are the same as those in Example 1.

[0079] Example 8

[0080] Compared with Example 1, the only difference is that the low-speed ball milling process in step a2 is absent, and other operations and parameters are the same as those in Example 1.

[0081] Comparative Example 1

[0082] Compared with Example 1, the only difference is that steps a and b are not performed, and in step c, no carbon nanotube-lead composite intermediate preform is added to prepare a lead-calcium positive grid alloy material, and other operations and parameters are the same as those in Example 1.

[0083] Comparative Example 2

[0084] Compared with Example 1, the only difference is that the preparation of the carbon nanotube-lead pre-mixture and the intermediate preform in steps a and b is not performed, and in step c, a physical mixture of CNT and lead is directly added to the lead liquid (the proportion of the physical mixture of CNT and lead is the same as that in the preform of Example 1, and the total amount is the same as that in the preform of Example 1), and other operations and parameters are the same as those in Example 1.

[0085] Comparative Example 3

[0086] Compared with Example 1, the only difference is that in step b2, microwave-assisted sintering is not used, but direct electric heating sintering is used, and the sintering temperature, the holding time after reaching the sintering temperature, and other operations and parameters are the same as those in Example 1.

[0087] Comparative Example 4

[0088] Compared with Example 1, the only difference is that steps a and b are not performed, but a lead skin wrapped CNT (the weight of the lead skin and CNT is the same as that in the preform of Example 1) is used to replace the preform in step c, and step c and subsequent processing are performed, and other operations and parameters are the same as those in Example 1.

[0089] Comparative Example 5

[0090] Compared with Example 1, the only difference is that in step b2, the temperature of microwave treatment is 200°C, and other operations and parameters are the same as those in Example 1.

[0091] Comparative Example 6

[0092] Compared with Example 1, the only difference is that in step c2, no ultrasonic cavitation treatment is performed, and other operations and parameters are the same as those in Example 1.

[0093] The composite materials prepared in Examples 1-8 and Comparative Examples 1-6 were cast into positive grid plates, and the prepared lead-carbon batteries were tested for cycle performance at 30%-80% rated capacity at 25°C room temperature by coating, curing, assembling the battery, and the specific implementation method was as follows: the full charged test battery was discharged at 0.2C charge-discharge rate by 20% rated capacity, then 50% rated capacity was discharged and charged cyclically until the discharge voltage was lower than 1.75V for three times in succession, at this time the cycle number was the cycle life of the battery at 30%-80% rated capacity.

[0094] The hardness, tensile strength, discharge current density, and cycle life of the battery at 30%-80% rated capacity of the examples and comparative examples were compared, and the results are shown in Table 1:

[0095]

[0096] Each of the embodiments in the specification is expressed in a related manner, and the differences between Examples 1-8 and Comparative Examples 1-6 are only highlighted.

[0097] The above only describes the preferred embodiments of the present application, and is not intended to limit the protection scope of the present application, and any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application are included in the protection scope of the present application.

Claims

1. A method for preparing a CNT-reinforced lead substrate gate, characterized in that the steps include... include: Step 1: CNTs and lead powder are mixed to obtain a mixture; the mixture is pressed into shape and then microwave sintered under a protective atmosphere to obtain a carbon nanotube-lead composite intermediate preform. Step 2: A carbon nanotube-lead composite intermediate preform is added to molten lead and subjected to ultrasonic cavitation treatment, followed by casting to obtain the CNT-reinforced lead substrate gate.

2. The method for preparing a CNT-reinforced lead substrate gate as described in claim 1, characterized in that, In step 1, the weight ratio of lead powder to CNTs is 10~40:

1.

3. The method for preparing a CNT-reinforced lead substrate gate as described in claim 1, characterized in that, In step (1), the mixing process is carried out in a protective atmosphere; Preferably, the mixing method is mechanical ball milling; Preferably, the rotational speed of the mechanical ball mill is 250~400 r / min; Preferably, the ball-to-material ratio in the mechanical ball milling process is 5~30:1; Preferably, the mechanical ball milling time is 1~10 h; Preferably, a low-speed mechanical ball milling process at a rotation speed of 50~200 r / min is performed before mechanical ball milling; the low-speed mechanical ball milling time is 0.2~3h.

4. The method for preparing a CNT-reinforced lead substrate gate as described in claim 1, characterized in that, The microwave sintering process is carried out in a protective atmosphere; Preferably, the microwave sintering temperature is 280~600℃; Preferably, the microwave power of microwave sintering is 500~2000W; Preferably, the holding time for microwave sintering is 10 to 30 minutes.

5. The method for preparing a CNT-reinforced lead substrate gate as described in claim 1, characterized in that, In step 2, the lead liquid is a molten liquid obtained by heating and melting lead-containing raw materials; Preferably, the melting temperature is above 400°C; Preferably, calcium-aluminum alloy is also added to the lead solution; Preferably, the weight ratio of lead to calcium-aluminum alloy in the molten lead is 75~90:0.1~1; In step 2, lead is melted at 400-500°C beforehand, then calcium-aluminum alloy is added, and the temperature is further increased to 600-650°C to melt the calcium-aluminum alloy, thus obtaining the lead liquid.

6. The method for preparing a CNT-reinforced lead substrate gate as described in claim 1, characterized in that, The carbon nanotube-lead composite intermediate preform is 5-30% of the weight of the lead liquid, and further 10-20%.

7. The method for preparing a CNT-reinforced lead substrate gate as described in claim 1, characterized in that, The frequency of ultrasonic cavitation is 20~40kHz, the ultrasonic power is 1000~3000W, and the action time is 5~15 minutes.

8. A CNT-reinforced lead substrate gate prepared by the method according to any one of claims 1 to 7.

9. The application of a CNT-reinforced lead substrate gate prepared by the method according to any one of claims 1 to 7, characterized in that, It is used as the positive electrode in the manufacture of lead-acid batteries.

10. A lead-acid battery, characterized in that, The invention comprises a CNT-reinforced lead substrate gate prepared by the method described in any one of claims 1 to 7.

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