Electrode rolling process for reducing electrode thickness rebound, battery electrodes and batteries
By employing high-temperature, long-term baking and secondary rolling processes, the problem of lithium battery electrode thickness rebound was solved, a tightly bonded structure was constructed, and the bonding strength of the electrode and battery performance were improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIAOGAN CORNEX NEW ENERGY INNOVATION TECHNOLOGY CO LTD
- Filing Date
- 2024-07-29
- Publication Date
- 2026-06-30
AI Technical Summary
Existing lithium battery electrodes suffer from severe thickness rebound in the later stages of manufacturing, leading to problems such as winding and battery bulging. Current preheating methods have short heating times and low temperatures, which cannot effectively improve the curing degree of the binder, thus affecting battery performance.
After baking the electrode at high temperature for a long time, it is then rolled a second time to build a tight and uniform bonding structure between the active material and the current collector. The adhesive is completely cured by baking at high temperature, which enhances the bonding strength to resist mechanical stress.
It effectively reduces electrode thickness rebound, improves the bonding strength between active material and current collector, reduces morphological changes during battery manufacturing, and improves battery performance.
Smart Images
Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium battery technology, specifically to an electrode rolling process for reducing electrode thickness rebound, battery electrodes, and batteries. Background Technology
[0002] The performance of lithium-ion batteries is greatly influenced by electrode design and manufacturing processes. In the later stages of electrode manufacturing, electrodes that have already been rolled to the predetermined thickness may experience a thickness increase after subsequent processing or storage; this phenomenon is called electrode rebound. Excessive electrode rebound can lead to misalignment of the tabs during winding and, after electrolyte injection, cause the overall battery thickness to exceed the design value, resulting in battery bulging. Therefore, to maintain stable negative electrode thickness, certain measures need to be taken to reduce negative electrode thickness rebound.
[0003] Existing processes for reducing electrode thickness rebound mostly involve treating the electrode after slurry coating to reduce the rebound of electrode thickness after rolling. For example, invention patent CN117878253A discloses a method for preparing a negative electrode, which reduces the thickness ratio of the first rolling and increases the thickness ratio of the second rolling by modifying the ratio between two rolling processes, thereby reducing the rebound rate of the electrode and the particle breakage of the active material. Building on this, invention patent CN117810367A discloses a negative electrode and its rolling method, which further softens the electrode by preheating before the second rolling to achieve a better effect in reducing the rebound rate of the electrode.
[0004] In the above process, the preheating method before the secondary rolling is mainly to help soften the material so that it can better adapt to the rolling pressure. However, the heating time is short and the heating temperature is low, which is not enough to affect the curing degree of the binder in the electrode material and other factors, so the effect on improving battery performance is relatively limited. Summary of the Invention
[0005] To address the aforementioned problems, the first aspect of this invention aims to provide an electrode rolling process for reducing electrode thickness rebound, which can improve the bonding strength between the electrode active material and the current collector, more effectively reduce electrode thickness rebound, and enable the battery electrode and battery prepared using the electrode rolling process to have better performance.
[0006] The second aspect of this invention aims to provide a battery electrode.
[0007] The third aspect of this invention aims to provide a battery.
[0008] According to a first aspect of the present invention, the present invention provides an electrode rolling process for reducing electrode thickness rebound, comprising the following steps:
[0009] S1. The electrode sheet after slurry coating is baked at a temperature of 160-180℃ for 20-30 minutes.
[0010] S2. Perform a second rolling process on the electrode sheet obtained in step S1 until the target thickness is reached.
[0011] Compared to short-term, low-temperature preheating, this invention uses high-temperature, long-term baking, which helps the binder to fully cure. This not only strengthens the connection between active material particles but also enhances the adhesion between the active material and the current collector. This improvement in the bonding performance of the electrode material can effectively resist mechanical stress during battery manufacturing, thereby controlling the increase in electrode thickness and more effectively reducing electrode thickness rebound.
[0012] Preferably, in step S1, the slurry includes artificial graphite, SP conductive agent, binder, and solvent.
[0013] Preferably, in step S1, the baking temperature is 160°C.
[0014] Preferably, in step S1, the baking time is 20 minutes.
[0015] Preferably, step S2 further includes the following steps:
[0016] S2.1. Perform a first rolling process on the electrode sheet obtained in step S1, rolling it to the first target thickness.
[0017] S2.2. Perform a second rolling process on the electrode sheet obtained in step S2.1, rolling it to the second target thickness.
[0018] The second target thickness is 85% to 95% of the first target thickness.
[0019] Generally, choosing a lower initial roll thickness helps reduce damage to the active material layer during the rolling process. However, after the electrode has undergone high-temperature baking, the curing of the binder makes the material more stable. Therefore, when a deeper roll is applied during the initial roll, the active material layer is no longer significantly damaged. Instead, the active material particles and binder can be quickly and effectively distributed in a dense and uniform manner on the current collector. This dense structure is less prone to significant morphological changes in subsequent processing steps, thus reducing thickness rebound.
[0020] Preferably, the second target thickness is 85% of the first target thickness.
[0021] Preferably, in step S2, the rolling pressure of the secondary rolling is 750-950 MPa.
[0022] Preferably, in step S2, the rolling speed of the secondary rolling is 10-20 m / min.
[0023] According to a second aspect of the present invention, the present invention provides a battery electrode sheet prepared according to the above-described electrode sheet rolling process.
[0024] According to a third aspect of the present invention, the present invention provides a battery comprising battery electrodes as described above.
[0025] The beneficial effects of this invention are as follows:
[0026] 1. In this application, high temperature and long time baking can improve the bonding strength between the active material of the electrode and the current collector to resist the mechanical stress in the battery manufacturing process, thereby controlling the electrode thickness and more effectively reducing the electrode thickness rebound.
[0027] 2. In this application, after high-temperature baking, the ratio between the two rolling processes is further improved to construct a tight and uniform structural foundation, so that the active material particles are firmly fixed on the current collector, thereby further reducing the risk of thickness rebound. Detailed Implementation
[0028] The present invention will be further described below with reference to specific embodiments. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.
[0029] The raw materials used in the following examples are all conventional chemicals purchased from the market.
[0030] Example 1
[0031] The negative electrode sheet, made from artificial graphite, SP powder, CMC powder, SBR adhesive, NMP solvent, and H2O, has an areal density of 175 g / m³. 2 The coated electrode sheets were placed in an oven for baking at 160℃ for 20 minutes. After baking, the electrode sheets were placed on a roller press for secondary rolling. First, the sheets were rolled to the first target thickness of 138±2μm, and then rolled to the second target thickness of 118±2μm. The rolling speed for both rolling operations was 15m / min, and the pressure for both operations was 880MPa.
[0032] Example 2
[0033] It is basically the same as Example 1, except that the baking temperature is 170°C.
[0034] Example 3
[0035] It is basically the same as Example 1, except that the baking temperature is 180°C.
[0036] Example 4
[0037] It is basically the same as Example 1, except that the baking time is 25 minutes.
[0038] Example 5
[0039] It is basically the same as Example 1, except that the baking time is 30 minutes.
[0040] Example 6
[0041] It is basically the same as Example 1, except that: it is first rolled to a first target thickness of 131±2μm.
[0042] Example 7
[0043] It is basically the same as Example 1, except that: it is first rolled to a first target thickness of 124±2μm.
[0044] Comparative Example 1
[0045] The process is basically the same as in Example 1, except that: after the slurry coating is completed, the electrode is not baked, but is directly placed on the roller press for secondary rolling. First, it is rolled to the first target thickness of 138±2μm, and then rolled to the second target thickness of 118±2μm.
[0046] Comparative Example 2
[0047] It is basically the same as Example 1, except that the baking temperature is 150°C.
[0048] Comparative Example 3
[0049] It is basically the same as Example 1, except that the baking time is 10 minutes.
[0050] Comparative Example 4
[0051] It is basically the same as Example 1, except that: it is first rolled to a first target thickness of 168±2μm.
[0052] Comparative Example 5
[0053] The process is basically the same as in Example 1, except that after baking, the electrode is placed on a roller press for one rolling process until the target thickness of 118±2μm is reached.
[0054] Battery manufacturing
[0055] The negative and positive electrode sheets obtained through the above-mentioned electrode rolling process are sliced by a slicing machine, stacked by a stacking machine, and then processed into batteries through baking, hot pressing and sealing, formation, and capacity testing.
[0056] Performance testing
[0057] Table 1. Effect of different heating temperatures on rebound rate
[0058] Heating temperature (°C) 24-hour rebound (%) 36-hour rebound (%) Example 1 160℃ 1.22 1.48 Example 2 170℃ 1.24 1.67 Example 3 180℃ 1.33 1.7 Comparative Example 1 none 4 5.1 Comparative Example 2 150℃ 1.7 2.2
[0059] Table 1 shows that high-temperature baking has a significant impact on the rebound rate. When the baking temperature is low, a more pronounced increase in rebound occurs after prolonged storage. This is because insufficient baking temperature leads to incomplete curing of the adhesive, thus affecting the long-term stability of the material. The lowest rebound rate is achieved at a preferred heating temperature of 160℃.
[0060] Table 2. Effect of different heating times on rebound rate
[0061] Heating time (min) 24-hour rebound (%) 36-hour rebound (%) Example 1 20min 1.22 1.48 Example 4 25min 1.4 1.7 Example 5 30min 1.4 1.82 Comparative Example 1 none 4 5.1 Comparative Example 3 10min 2.74 3.76
[0062] As shown in Table 2, a short baking time will significantly increase the rebound rate. The rebound rate is lowest when the heating time is 20 minutes.
[0063] Table 3. Effect of different first target thicknesses on rebound rate
[0064] Theoretically, a lower initial roll thickness helps reduce damage to the active material layer during the rolling process, thus lowering the rebound rate. However, as shown in Table 3, the rebound rate decreases significantly when the initial roll thickness is deeper. This is because the curing of the binder after high-temperature baking of the electrode makes the material sufficiently stable. A deeper initial roll thickness prevents significant damage to the active material layer and instead allows for a rapid and effective formation of a dense and uniform distribution of active material particles and binder on the current collector. Preferably, the rebound rate is lowest when the second target thickness is 85% of the first target thickness.
Claims
1. An electrode rolling process for reducing electrode thickness rebound, characterized in that, Includes the following steps: S1. Bake the electrode sheets after the slurry coating is completed. The baking temperature is 160~180℃ and the baking time is 20~30min. S2. Perform a second rolling process on the electrode sheet obtained in step S1 to achieve the target thickness; In step S1, the slurry includes artificial graphite, SP powder, CMC powder, SBR adhesive, NMP solvent, and H2O. Step S2 further includes the following steps: S2.
1. Perform a first rolling process on the electrode sheet obtained in step S1, rolling it to the first target thickness; S2.
2. Perform a second rolling process on the electrode sheet obtained in step S2.1, rolling it to the second target thickness; The second target thickness is 85% of the first target thickness.
2. The electrode rolling process for reducing electrode thickness rebound according to claim 1, characterized in that, In step S1, the baking temperature is 160°C.
3. The electrode rolling process for reducing electrode thickness rebound according to claim 1, characterized in that, In step S1, the baking time is 20 minutes.
4. The electrode rolling process for reducing electrode thickness rebound according to claim 1, characterized in that, In step S2, the rolling pressure of the secondary rolling is 750~950 MPa.
5. The electrode rolling process for reducing electrode thickness rebound according to claim 1, characterized in that, In step S2, the rolling speed of the secondary rolling is 10m / min to 20m / min.
6. A battery electrode, characterized in that... ， The electrode is prepared by the rolling process according to any one of claims 1-5.
7. A battery, characterized in that, Includes the battery electrode as described in claim 6.