A lead-acid battery formation process

Abstract

This invention discloses a lead-acid battery formation process, belonging to the field of lead-acid battery technology. The lead-acid battery formation process includes the following steps: S1, initial charging of the battery; S2, standard charge-discharge cycle stage; S3, over-discharge-charge operation, and then repeating the over-discharge-charge cycle; S4, final charging. The over-discharge step of this invention increases the initial battery capacity by approximately 3%, effectively improving the defect of low initial capacity in continuously cast and rolled plate batteries; the 100% DOD cycle life is increased by more than 30%, significantly extending the battery's service life; at the same time, the process is simple to implement, requiring no new equipment, and can be implemented using existing internal formation charge-discharge power supplies and control systems, resulting in low modification costs.

Description

Technical Field

[0001] This invention relates to the field of lead-acid battery technology, and in particular to a lead-acid battery formation process. Background Technology

[0002] Lead-acid batteries are one of the most widely used chemical power sources. Their positive electrode grids are mainly manufactured using processes such as gravity casting and continuous casting and rolling. Among these, the continuous casting and rolling process, through continuous casting and rolling, can achieve high-efficiency and high-consistency production of grids, and the grids have fine grain structure and excellent mechanical properties. The corrosion resistance of the positive electrode grids is significantly improved compared with traditional gravity casting, making it an important development direction for lead-acid battery grid manufacturing.

[0003] However, while continuously cast and rolled positive grids improve corrosion resistance, they also present a technical challenge. Due to the fine grain structure and dense surface of continuously cast and rolled grids, their chemical activity is relatively low. In the high-temperature and high-humidity environment of the electrode curing process, the grid surface is not prone to uniform and moderate oxidation corrosion, making it difficult to form a dense and firmly bonded pre-corrosion layer (PbO / PbSO4 transition layer) at the grid-lead paste interface. This pre-corrosion layer is a crucial interface between the positive grid and lead paste, and its thickness and density directly determine the growth quality of the corrosion layer during subsequent formation processes. During subsequent charge-discharge processes within the battery, due to the absence or poor structure of the pre-corrosion layer, the newly formed corrosion layer (mainly PbO2) on the positive grid surface has a loose structure, coarse grains, and poor density, leading to increased interfacial contact resistance between the corrosion layer and the grid substrate, resulting in a high-resistivity corrosion layer. This high-resistivity layer generates a significant polarization voltage drop during battery charging and discharging. On the one hand, it reduces the utilization rate of the positive electrode active material, resulting in a lower initial battery capacity. On the other hand, it accelerates the separation of the grid from the corrosion layer, causing rapid capacity decay during cycling and leading to a shorter battery cycle life.

[0004] To address the aforementioned issues, existing technologies primarily focus on controlling the formation current curve (such as multi-stage constant current formation and segmented pulse formation), adjusting the amount of acid added to the electrolyte, and optimizing curing process parameters. However, none of these methods effectively solve the fundamental problem of corrosion layer structure deterioration during the internal formation process of continuously cast and rolled grids. Therefore, there is an urgent need for an internal formation process that can improve the microstructure of the corrosion layer in continuously cast and rolled grids, reduce interfacial resistance, and simultaneously enhance the initial capacity and cycle life of the battery. Summary of the Invention

[0005] This invention provides a lead-acid battery formation process that can solve the technical problems in the prior art where insufficient pre-corrosion layer in continuously cast and rolled grids leads to a loose corrosion layer structure, coarse grains, poor density, and high interfacial contact resistance on the surface of the positive grid after internal formation, resulting in low initial battery capacity and short cycle life.

[0006] The objective of this invention can be achieved through the following technical solutions: A lead-acid battery formation process includes the following steps: S1. Perform the initial charge on the battery; S2, Perform the standard charge-discharge cycle phase; S3. Perform an over-discharge-charge operation, and then repeat the over-discharge-charge cycle. S4. Perform final charging.

[0007] Furthermore, in step S1, the initial charging current is 0.05C to 0.2C.

[0008] Furthermore, in step S1, the initial charging time is terminated when the charged amount reaches 1.5 to 3.0 times the rated capacity of the battery.

[0009] Further, in step S2, the specific steps of the standard charge and discharge are as follows: discharge at a current of 0.1C to 0.5C for 0.5 to 1 hour, and then charge at a current of 0.1C to 0.2C to full capacity.

[0010] Furthermore, in step S2, the number of standard charge-discharge cycles is 2 to 5.

[0011] Further, in step S3, the specific steps of the over-discharge-charge are as follows: first, perform two stages of stepped discharge, with a resting time of 3 to 60 minutes between the two stages of discharge; after the overall discharge is completed, charge to full capacity with a current of 0.1C to 0.3C.

[0012] Furthermore, the termination voltage of each stage of the two-stage stepped discharge is 0.5 to 1.0 V per cell; the discharge current of the first stage is 0.1 C to 0.5 C, and the discharge current of the second stage is 0.1 C to 0.5 C.

[0013] Furthermore, in step S3, the number of over-discharge-charge cycles is 2 to 5.

[0014] Furthermore, in step S4, the final charging includes final capacity determination and shaping charging.

[0015] Furthermore, the specific steps for determining the final capacity are as follows: discharge the cell at a current of 0.1C to 0.3C until the cell voltage is 1.75V / cell.

[0016] Furthermore, the specific steps of the shaping charge are as follows: perform two-stage constant current charging at a current of 0.1C to 0.2C until full capacity.

[0017] The beneficial effects of this invention are: 1. In the formation process of this invention, S1 initial charging initially converts the positive and negative electrode active materials into PbO2 and spongy lead, establishing a basic capacity and providing energy for subsequent reactions; S2 standard charge-discharge cycle further activates the electrodes, promoting the full conversion of active materials and initially forming a corrosion layer with a certain structure; S3 through deep over-discharge and multiple charge-discharge cycles, the corrosion layer on the positive grid surface is induced to dissolve and recrystallize by over-discharge, effectively refining the grains, increasing the density of the corrosion layer, reducing the interfacial contact resistance, and repairing the defects of insufficient pre-corrosion layer; S4 final charging completes capacity determination and shaping charging, ensuring that the battery reaches the optimal charge-discharge state, thereby synergistically achieving the beneficial effects of improving the initial capacity of the battery and extending the cycle life.

[0018] 2. The over-discharge step of this invention increases the initial capacity of the battery by about 3%, effectively improving the defect of low initial capacity of continuously cast and rolled plate batteries; the 100% DOD cycle life is increased by more than 30%, significantly extending the battery's service life; at the same time, the process is simple to implement, requiring no new equipment, and can be implemented using existing internal formation charging and discharging power supplies and control systems, resulting in low modification costs. Detailed Implementation

[0019] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0020] A lead-acid battery formation process includes the following steps: S1. Perform the initial charge on the battery; S2, Perform the standard charge-discharge cycle phase; S3. Perform an over-discharge-charge operation, and then repeat the over-discharge-charge cycle. S4. Perform final charging.

[0021] In the formation process of this invention, S1, the initial charge, initially converts the positive and negative electrode active materials into PbO2 and spongy lead, establishing a basic capacity and providing energy for subsequent reactions. S2, a standard charge-discharge cycle, further activates the electrodes, promoting the full conversion of active materials and initially forming a corrosion layer with a certain structure. S3, through deep over-discharge and multiple charge-discharge cycles, utilizes over-discharge to induce dissolution and recrystallization of the corrosion layer on the positive grid surface, effectively refining the grains, increasing the density of the corrosion layer, reducing interfacial contact resistance, and simultaneously repairing defects caused by insufficient pre-corrosion. S4, the final charge, completes capacity determination and shaping charging, ensuring the battery reaches its optimal charge-discharge state. The synergistic effect of these steps achieves an increase in initial battery capacity and a significant extension of cycle life. Furthermore, the process is simple, requires no additional equipment, and has good industrial application value.

[0022] In some embodiments, in step S1, the initial charging current is 0.05C to 0.2C. This small current range is beneficial for the uniform conversion of active materials and avoids overheating and deformation of the electrode plates. If the current is too small, the formation efficiency will be low and the time will be too long. If the current is too large, it may cause the active material on the electrode plates to fall off or the grid to corrode unevenly.

[0023] In some embodiments, in step S1, the initial charging time is terminated when the charged amount reaches 1.5 to 3.0 times the rated capacity of the battery. This overcharge ensures that the positive and negative electrode active materials are fully converted and a basic capacity is established. If the overcharge is too small, the active materials will not be fully converted and the initial capacity will be low. If the overcharge is too large, excessive gas production may occur, which may damage the electrode structure.

[0024] In some embodiments, the specific steps of the standard charge-discharge process in step S2 are as follows: discharging at a current of 0.1C to 0.5C for 0.5 to 1 hour, and then charging to full capacity at a current of 0.1C to 0.2C. These parameters enable the electrode to initially activate and form an initial corrosion layer. If the discharge time is too short or the current is too small, the activation will be insufficient; if the discharge time is too long or the current is too large, it will easily lead to coarsening of PbSO4 crystals and affect subsequent capacity.

[0025] In some embodiments, in step S2, the number of standard charge-discharge cycles is 2 to 5. This number of cycles promotes the stabilization of the active material and the formation of a basic etched layer. Too few cycles result in insufficient activation and an incomplete etched layer, while too many cycles prolong the formation cycle and increase energy consumption without significant gain.

[0026] In some embodiments, the specific steps of over-discharge-charge in step S3 are as follows: first, perform two stages of stepped discharge, with a resting time of 3–60 minutes between the two stages; after the overall discharge is completed, charge to full capacity with a current of 0.1C–0.3C. Performing two stages of stepped discharge and setting a resting time of 3–60 minutes between the two stages allows the electrolyte concentration to become more uniform and reduces concentration polarization, thereby ensuring that the corrosion layer on the positive grid surface can be deeply and uniformly decomposed by discharge; subsequently, charge to full capacity with a current of 0.1C–0.3C, using a suitable charging current to promote the dissolution of Pb. 2+ Recrystallization occurs on the grid surface, forming a fine-grained, dense PbO2 corrosion layer that is firmly bonded to the substrate. The synergistic effect of this two-stage stepped discharge and resting / recharging process effectively refines the corrosion layer grains and reduces interfacial contact resistance, thereby improving the utilization rate of the positive electrode active material. This significantly improves both the initial capacity and cycle life of the battery, while the process is mild and controllable, making it suitable for industrial production.

[0027] In some embodiments, the termination voltage of each stage of the two-stage stepped discharge is 0.5–1.0V per cell; the discharge current of the first stage is 0.1C–0.5C, and the discharge current of the second stage is 0.1C–0.5C. This setting ensures that the etched layer is fully and uniformly dissolved, providing conditions for subsequent recrystallization; if the termination voltage is too high or the current is too low, the dissolution will be incomplete, and if the termination voltage is too low or the current is too high, it may damage the grid substrate or cause excessive shedding of active material.

[0028] In some embodiments, the number of over-discharge-charge cycles in step S3 is 2 to 5. Multiple cycles allow the etched layer to repeatedly dissolve and recrystallize, refining and densifying the grains. Too few cycles result in insufficient structural improvement, while too many cycles lead to a lengthy process and an increased risk of battery over-discharge.

[0029] In some embodiments, step S4 includes final capacity determination and reshaping charging.

[0030] In some embodiments, the specific steps for determining the final capacity are as follows: discharging the battery at a current of 0.1C to 0.3C until the cell voltage reaches 1.75V / cell. This step can accurately calibrate the actual capacity of the battery. If the current is too small, the test time will be too long; if the current is too large, the capacity will be too low and will not reflect the true state.

[0031] In some embodiments, the specific steps of the shaping charge are as follows: performing a two-stage constant current charge at a current of 0.1C to 0.2C until full capacity. The two-stage low-current charge ensures that the voltage of each cell is consistent and the active material is fully saturated. If the current is too small, the charging time will be too long; if the current is too large or the number of stages is insufficient, the equalization effect will be poor and the capacity consistency will be reduced.

[0032] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0033] Example 1 Using a 6-DMF-21 battery (rated capacity of 21Ah) as the test object, the lead-acid battery that has been vacuum-filled with acid was placed in a circulating water bath within 30 minutes, and the charging line was connected at the same time to prepare for charging. The charge / discharge machine was turned on within 60 minutes of filling with acid, and the charging was started in sequence according to the following procedure.

[0034] S1. Initial charging: 0.05C charging for 1 hour, 0.1C charging for 1 hour, 0.2C charging for 10 hours; S2, Standard charge / discharge cycle: 0.2C discharge for 0.5h, 0.2C charge for 8h, 0.2C discharge for 0.5h, 0.2C charge for 8h; S3, Multiple over-discharge stages: 0.5C discharge 0.5V / cell, stand for 3 minutes, 0.1C discharge 0.5V / cell, 0.2C charge for 11 hours; then perform over-discharge-charge cycles twice. S4, Final Charge: 0.3C discharge to 1.75V / cell, 0.2C charge for 8 hours, 0.1C charge for 8 hours.

[0035] Example 2 Using 6-DMF-21 batteries as the test subject, the lead-acid batteries that had been vacuum-filled with acid were placed in a circulating water bath within 30 minutes, and the charging circuit was connected to prepare for charging. The charge / discharge machine was turned on within 60 minutes of filling with acid, and the charging was started in sequence according to the following procedure.

[0036] S1. Initial charging: 0.05C charging for 1 hour, 0.1C charging for 1 hour, 0.2C charging for 10 hours; S2, Standard charge / discharge cycle: 0.2C discharge for 0.5h, 0.2C charge for 8h, 0.2C discharge for 0.5h, 0.2C charge for 8h; S3, Multiple over-discharge stages: 0.5C discharge 0.5V / cell, stand for 10 minutes, 0.1C discharge 0.5V / cell, 0.2C charge for 11 hours; then perform over-discharge-charge cycles twice. S4, Final Charge: 0.3C discharge to 1.75V / cell, 0.2C charge for 8 hours, 0.1C charge for 8 hours.

[0037] Example 3 Using 6-DMF-21 batteries as the test subject, the lead-acid batteries that had been vacuum-filled with acid were placed in a circulating water bath within 30 minutes, and the charging circuit was connected to prepare for charging. The charge / discharge machine was turned on within 60 minutes of filling with acid, and the charging was started in sequence according to the following procedure.

[0038] S1. Initial charging: 0.05C charging for 1 hour, 0.1C charging for 1 hour, 0.2C charging for 10 hours; S2, Standard charge / discharge cycle: 0.2C discharge for 0.5h, 0.2C charge for 8h, 0.2C discharge for 0.5h, 0.2C charge for 8h; S3, Multiple over-discharge stages: 0.5C discharge 0.5V / cell, stand for 20 minutes, 0.1C discharge 0.5V / cell, 0.2C charge for 11 hours; then perform over-discharge-charge cycles twice. S4, Final Charge: 0.3C discharge to 1.75V / cell, 0.2C charge for 8 hours, 0.1C charge for 8 hours.

[0039] Example 4 Using 6-DMF-21 batteries as the test subject, the lead-acid batteries that had been vacuum-filled with acid were placed in a circulating water bath within 30 minutes, and the charging circuit was connected to prepare for charging. The charge / discharge machine was turned on within 60 minutes of filling with acid, and the charging was started in sequence according to the following procedure.

[0040] S1. Initial charging: 0.05C charging for 1 hour, 0.1C charging for 1 hour, 0.2C charging for 10 hours; S2, Standard charge / discharge cycle: 0.2C discharge for 0.5h, 0.2C charge for 8h, 0.2C discharge for 0.5h, 0.2C charge for 8h; S3, Multiple over-discharge stages: 0.5C discharge 0.5V / cell, stand for 30 minutes, 0.1C discharge 0.5V / cell, 0.2C charge for 11 hours; then perform over-discharge-charge cycles twice. S4, Final Charge: 0.3C discharge to 1.75V / cell, 0.2C charge for 8 hours, 0.1C charge for 8 hours.

[0041] Example 5 Using 6-DMF-21 batteries as the test subject, the lead-acid batteries that had been vacuum-filled with acid were placed in a circulating water bath within 30 minutes, and the charging circuit was connected to prepare for charging. The charge / discharge machine was turned on within 60 minutes of filling with acid, and the charging was started in sequence according to the following procedure.

[0042] S1. Initial charging: 0.05C charging for 1 hour, 0.1C charging for 1 hour, 0.2C charging for 10 hours; S2, Standard charge / discharge cycle: 0.2C discharge for 0.5h, 0.2C charge for 8h, 0.2C discharge for 0.5h, 0.2C charge for 8h; S3, Multiple over-discharge stages: 0.5C discharge 0.5V / cell, stand for 60min, 0.1C discharge 0.5V / cell, 0.2C charge for 11h; then perform over-discharge-charge cycles twice. S4, Final Charge: 0.3C discharge to 1.75V / cell, 0.2C charge for 8 hours, 0.1C charge for 8 hours.

[0043] Comparative Example 1 Using 6-DMF-21 batteries as the test subject, the lead-acid batteries that had been vacuum-filled with acid were placed in a circulating water bath within 30 minutes, and the charging circuit was connected to prepare for charging. The charge / discharge machine was turned on within 60 minutes of filling with acid, and the charging was started in sequence according to the following procedure.

[0044] S1. Initial charging: 0.05C charging for 1 hour, 0.1C charging for 1 hour, 0.2C charging for 10 hours; S2, Standard charge / discharge cycle: 0.2C discharge for 0.5 hours, 0.2C charge for 8 hours, 4 charge / discharge cycles; S3, Final Charge: 0.3C discharge to 1.75V / cell, 0.2C charge for 8 hours, 0.1C charge for 8 hours.

[0045] Comparative Example 2 Using 6-DMF-21 batteries as the test subject, the lead-acid batteries that had been vacuum-filled with acid were placed in a circulating water bath within 30 minutes, and the charging circuit was connected to prepare for charging. The charge / discharge machine was turned on within 60 minutes of filling with acid, and the charging was started in sequence according to the following procedure.

[0046] S1. Initial charging: 0.05C charging for 1 hour, 0.1C charging for 1 hour, 0.2C charging for 10 hours; S2, Standard charge-discharge cycle: 0.2C discharge for 1 hour, 0.2C charge for 8 hours, 4 charge-discharge cycles; S3, Final Charge: 0.3C discharge to 1.75V / cell, 0.2C charge for 8 hours, 0.1C charge for 8 hours.

[0047] The initial capacity and cycle life of the batteries in Examples 1-5 and Comparative Examples 1 and 2 were tested using the following methods: 1. Initial capacity test: The test was conducted at 25±2℃ in accordance with standard GB / T 32620.1-2016. 2. Cycle life test: At 25±2℃, discharge at 10A constant current to a single cell voltage of 1.75V; then charge at 10A constant current and single cell voltage limit of 2.45V for a total charging time of 4 hours; after charging and discharging, let stand for 60 minutes, and repeat the above process until the capacity decays to 80% of the rated value to determine the end of the life. The test results are shown in Table 1.

[0048] Table 1

[0049] Examples 1-5 of this invention all employ the formation process designed in this invention, and their initial capacities all reach or exceed the nominal values, with significantly extended cycle lives. As the resting time during the over-discharge stage is gradually extended (from 3 min in Example 1 to 60 min in Example 5), the initial capacity and cycle life of the battery show a continuous upward trend. This indicates that introducing an appropriate resting time during the over-discharge process facilitates a more complete dissolution-recrystallization reaction of the corrosion layer, thereby obtaining a more dense and finer-grained corrosion layer, further reducing interfacial contact resistance, improving the utilization rate of the positive electrode active material, and extending battery life.

[0050] Comparative Example 1 omits the multiple over-discharge stages of the present invention, performing final charging directly after the standard charge-discharge cycle. Its initial capacity and cycle life are significantly lower than those of the embodiments. This indicates that without the over-discharge step, the corrosion layer structure formed on the surface of the continuously cast and rolled grid is loose and has coarse grains due to insufficient pre-corrosion layer, resulting in high interface resistance, low utilization of active materials, and the corrosion layer is prone to detachment during cycling, causing rapid capacity decay.

[0051] Comparative Example 2 used a longer discharge time (1 h) in the standard charge-discharge cycle and also omitted the over-discharge stage. Its initial capacity was lower than that of Comparative Example 1, and although its cycle life was slightly higher than that of Comparative Example 1, it was still much lower than that of the Example. This indicates that simply adjusting the standard charge-discharge parameters cannot fundamentally solve the problem of poor corrosion layer structure. Over-discharge may actually lead to coarsening of PbSO4 crystals, further deteriorating the reversible ability of the active material. The slightly higher cycle life than Comparative Example 1 may be due to the deeper discharge activating the electrode to some extent, but it is still much lower than that of the Example and cannot replace the dissolution-recrystallization effect of over-discharge.

[0052] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A lead-acid battery formation process characterized by, Includes the following steps: S1. Perform the initial charge on the battery; S2, Perform the standard charge-discharge cycle phase; S3. Perform an over-discharge-charge operation, and then repeat the over-discharge-charge cycle. S4. Perform final charging.

2. The lead-acid battery formation process of claim 1, wherein, In step S1, the initial charging current is 0.05C to 0.2C.

3. The lead-acid battery formation process of claim 1, wherein, In step S1, the initial charging time is terminated when the charged amount reaches 1.5 to 3.0 times the rated capacity of the battery.

4. The lead-acid battery formation process of claim 1, wherein, In step S2, the specific steps of the standard charge and discharge are as follows: discharge at a current of 0.1C to 0.5C for 0.5 to 1 hour, and then charge at a current of 0.1C to 0.2C until full capacity.

5. The lead-acid battery formation process of claim 1 wherein, In step S2, the number of standard charge-discharge cycles is 2 to 5.

6. The lead-acid battery formation process of claim 1, wherein, In step S3, the specific steps of the over-discharge-charge process are as follows: first, perform two stages of stepped discharge, with a resting time of 3 to 60 minutes between the two stages of discharge; after the overall discharge is completed, charge to full capacity with a current of 0.1C to 0.3C.

7. The lead-acid battery formation process of claim 6, wherein, The termination voltage of each of the two stepped discharge stages is 0.5 to 1.0 V per cell; the discharge current of the first stage is 0.1 C to 0.5 C, and the discharge current of the second stage is 0.1 C to 0.5 C.

8. The lead-acid battery formation process of claim 1 wherein, In step S3, the number of over-discharge-charge cycles is 2 to 5.

9. The lead-acid battery formation process as described in claim 1, characterized in that, In step S4, the final charging includes final capacity determination and shaping charging.

10. The lead-acid battery formation process as described in claim 9, characterized in that, The specific steps for determining the final capacity are as follows: discharge the cell at a current of 0.1C to 0.3C until the cell voltage is 1.75V / cell; The specific steps of the shaping and charging are as follows: perform two-stage constant current charging at a current of 0.1C to 0.2C until full capacity.

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