Positive electrode sheet, method for manufacturing the same, and lithium ion battery
By setting grooves on the positive electrode body and rolling and transferring a self-sealing layer, the thermal runaway problem of high-nickel ternary lithium-ion batteries under abuse conditions is solved, achieving a balance between safety (no fire or explosion) and electrochemical performance.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- LISHEN (QINGDAO) NEW ENERGY CO LTD
- Filing Date
- 2026-02-03
- Publication Date
- 2026-05-29
AI Technical Summary
Lithium-ion batteries with high-nickel ternary cathode materials are prone to thermal runaway when subjected to mechanical abuse or overcharging and over-discharging, leading to fires and explosions. Existing safety strategies cannot effectively suppress internal short circuits and thermal runaway, and may also result in loss of battery performance or increased costs.
A hexagonal groove is formed on the positive electrode body, and a self-sealing layer, including polyamide urea, eutectic trigger, conductive agent and binder, is rolled and transferred in the groove to form a self-sealing layer that ensures that it will not catch fire or explode under abuse conditions, while maintaining electrochemical performance.
It achieves the goal of preventing the battery from catching fire or exploding under abuse conditions such as needle penetration, hot box, and overcharge, while maintaining long cycle time and high rate performance at room temperature, thus improving the safety and electrochemical performance of lithium-ion batteries.
Smart Images
Figure CN122117786A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery technology, and in particular to a positive electrode sheet, its preparation method, and a lithium-ion battery. Background Technology
[0002] With the increasing demand for energy density in the new energy industry, high-nickel ternary cathodes have become the mainstream technology. However, their inherent poor thermal stability and low oxygen release temperature make the batteries prone to thermal runaway when subjected to mechanical abuse or overcharging and over-discharging. The temperature can exceed 600°C within seconds, causing fires and explosions.
[0003] To address this critical issue, researchers have proposed numerous safety strategies, such as ceramic-coated separators, electrolyte flame-retardant additives, or inert coating technology for the cathode. While these strategies can improve battery safety to some extent, they often lead to a loss of battery performance or increase manufacturing processes, thereby raising costs. Moreover, for high-energy-density systems, they still cannot effectively suppress the occurrence of internal short circuits and the series of chain reactions they trigger.
[0004] Therefore, there is an urgent need to develop a new technology to effectively suppress heat accumulation caused by short circuits within the battery, preventing thermal runaway and explosions at the source and significantly improving the intrinsic safety of the battery. At the same time, it is also necessary to maintain electrical performance and simplify manufacturing processes as much as possible while ensuring battery safety. This has become one of the important issues in the current development of lithium-ion battery technology, especially in the area of high-energy-density ternary cathode materials. How to improve battery safety while ensuring battery performance remains a key research focus and challenge. Summary of the Invention
[0005] The purpose of this invention is to provide a positive electrode sheet, its preparation method, and a lithium-ion battery.
[0006] To achieve the above objectives, this application adopts the following solution: A positive electrode includes a positive electrode body, a plurality of grooves disposed on the positive electrode body, and a self-sealing layer disposed within the grooves.
[0007] The groove is a hexagonal recess; preferably, the side length is 80-100 μm, the depth is 6-10 μm, and the row spacing is 150-200 μm. More preferably, the side length is 100 μm, the depth is 8 μm, and the row spacing is 150 μm.
[0008] The positive electrode body includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; Preferably, the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (95-98):(1-4):(1-4); more preferably, it is 97.8:1:1.2. Preferably, the positive electrode active material is nickel-cobalt-manganese (NCM). Preferably, the positive electrode conductive agent is one or a mixture of CNT and carbon black; preferably, it is a mixture of CNT156 and LiTX200; preferably, the mass ratio of CNT156 to LiTX200 is 6:4. Preferably, the positive electrode binder is PVDF; more preferably, it is a mixture of PVDF5130 and HSV900; preferably, the mass ratio of PVDF5130 to HSV900 is 8:4.
[0009] The self-sealing layer includes polyamide urea, eutectic trigger, conductive agent, and binder; Preferably, the mass ratio of the polyamide urea, eutectic trigger, conductive agent and binder is (85-95):(1-10):(1-5):(1-5), and more preferably 89.5:6:3:1.5; Preferably, the eutectic trigger is PEG-B; Preferably, the conductive agent is one or a mixture of CNT and carbon black; preferably, it is a mixture of CNT156 and LiTX200; preferably, the mass ratio of CNT156 to LiTX200 is 1:2. Preferably, the adhesive is PVDF-HFP.
[0010] The present invention also includes a method for preparing the positive electrode sheet, comprising the following steps: (1) preparing a positive electrode sheet body; (2) heating and rolling an alloy roller with a pattern printed on its surface to press the positive electrode sheet body obtained in step (1); (3) preparing a self-sealing layer slurry; (4) rolling and transferring the self-sealing layer slurry obtained in step (3) onto the positive electrode sheet body with grooves obtained in step (2); (5) rolling and cutting the electrode sheet obtained in step (4) to obtain the positive electrode sheet.
[0011] Preferably, the specific steps of step (1) are as follows: mixing the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder to obtain a positive electrode slurry; preferably, the solvent of the positive electrode slurry is NMP, the solid content is 65-70%, and the viscosity is 6000-7000cp; coating the positive electrode slurry onto the positive electrode current collector and drying it to obtain the positive electrode sheet body; preferably, the single-sided areal density is 20-23 mg cm⁻¹ during coating. -2 The areal density of both sides is 40-46 mg / cm³. -2 The compacted density is 3.4-3.6 g / cm³. -3 .
[0012] Preferably, the specific steps of step (2) are as follows: heating and rolling the alloy roller with the pattern printed on the surface to roll the positive electrode body obtained in step (1); the rolling temperature is 40-80℃, the linear pressure is 0.5-0.8MPa, the running speed is 10-25m / min, the online monitoring of the embossing integrity rate is ≥98%, the depth tolerance is ±1um, and the low temperature setting is performed after embossing to eliminate aluminum foil springback; the electrode waviness is ≤1mm / 500mm.
[0013] Preferably, the specific steps of step (3) are as follows: mixing polyamide urea, eutectic trigger, conductive agent and binder to obtain a self-sealing layer slurry; the solvent of the self-sealing layer slurry is NMP, the solid content is 15-20%, and the viscosity is 4000-6000cp.
[0014] Preferably, the specific steps of step (4) are as follows: Roller transfer; the self-sealing layer slurry obtained in step (3) is roller transferred onto the positive electrode body with grooves obtained in step (2); the roller protrusion height is 6-10um, the thickness error is ±0.2um, the leakage rate is <0.5%, and a uniform, non-porous electrode film is obtained; the roller protrusion height is set in accordance with the groove depth; Flash drying eliminates solvent residue; preferably, flash drying at 90℃ results in solvent residue ≤200ppm. Hot pressing, where the slurry within the groove is subjected to secondary pressure flow; preferably, hot pressing at 80℃, linear pressure of 0.5-0.8MPa, and pressing time of 0.5-0.8s. The electrode is dried twice under vacuum at 80℃ and then wound up in the drying room to obtain the positive electrode.
[0015] The present invention also includes a lithium-ion battery, comprising the aforementioned positive electrode and negative electrode; Preferably, the negative electrode sheet is prepared in the following manner: 1) Preparation of negative electrode slurry; the negative electrode slurry comprises the following components in the following ratio: graphite: silicon carbide: LB212: SONE: LiTX200 = 66.4:30:0.1:3:0.5; preferably, the solid content of the negative electrode slurry is 35-40%, and the viscosity is 6000-8000 cps; 2) Coating the negative electrode slurry onto the negative electrode current collector; preferably, the surface density of the coating on one side is 6-7 mg / cm³. -2 The areal density of both sides is 12-14 mg / cm³. -2 The compacted density is 2.8-3.5 g / cm³. 3 The preferred value is 1.5 ± 0.3 g cm. -3 .
[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This application enables high-nickel ternary batteries to "not catch fire or explode" under abuse conditions such as needle penetration, hot box, and overcharge by setting grooves on the positive electrode body and placing the self-sealing layer in the grooves through roll transfer printing. At the same time, it maintains long cycle time and high rate performance at room temperature, taking into account both safety and electrochemical performance. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the roller transfer printing method of the present invention; Figure 2 The figures show a comparison of the scaling performance of the embodiments and comparative examples of the present invention. Detailed Implementation
[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
[0019] Example 1: Preparation of positive electrode sheet and lithium-ion battery: 1. The preparation method of the positive electrode sheet includes the following steps: (1) Preparation of positive electrode sheet: The positive electrode slurry was prepared according to the ratio of NCM:LITX200:CNT156:PVDF5130:HSV900 = 97.80:0.6:0.4:0.8:0.4, with a solid content of 67%, a viscosity of 6700cps, and a single-sided areal density of 23mg / cm² during coating. -2 The areal density of both sides is 46 mg / cm³. -2 Compacted density 3.5 g / cm³ -3 The positive electrode body is vacuum dried at 115℃ and cooled to 25℃ for later use; (2) The positive electrode body obtained in step (1) is heated and rolled by an alloy roller with a pattern printed on its surface; specifically: the electrode obtained in step (1) is heated and rolled by an alloy roller with a pattern printed on its surface (used to prepare grooves, hexagonal pits, side length 100um, depth 6um, row spacing 150um), the rolling temperature is 60℃, the linear pressure is 0.6MPa, the running speed is 15m / min, the embossing integrity rate is monitored online (the embossing integrity rate monitored online is ≥98%, the depth tolerance is ±1um), the unqualified section is automatically marked and the subsequent section is rejected; after the embossing is completed, the low temperature is set: 40℃ cold air knife for 2s to eliminate the springback of aluminum foil; the electrode waviness is ≤1mm / 500mm.
[0020] (3) Preparation of self-sealing layer slurry: STOBA:PEG-B eutectic trigger: CNT157:LiTX200:PVDF-HFP=89.5:6:1:2:1.5 was used to prepare slurry, with NMP as solvent, 15% solid content and 4500cps viscosity; (4) Roller-pressing the self-sealing layer slurry obtained in step (3) onto the pre-patterned positive electrode sheet, including: Roller transfer printing ( Figure 1 The schematic diagram shows that the coating thickness of the self-sealing layer slurry and the uniformity of the electrode sheet are controlled by the height of the roller protrusion and the depth of the embossing pit. The self-sealing layer slurry obtained in step (3) is rolled and transferred onto the positive electrode sheet body with grooves obtained in step S2. The height of the roller protrusion is 6 μm, the thickness error is ±0.2 μm, and the leakage rate is <0.5%, resulting in a uniform and pore-free electrode sheet film. Flash drying eliminates solvent residue; flash drying at 90℃ for 30 seconds, solvent residue ≤200ppm; Hot pressing, the slurry in the groove is pressurized and flowed a second time; 80℃ hot pressing, linear pressure 0.5MPa, pressing time 0.5s; the slurry in the microcavity is pressurized and flowed a second time, forming a "rivet head" mechanical lock; STOBA film peel strength ≥1.2N / cm (180° peel, 20mm / min).
[0021] The electrode sheet is dried and wound up twice under vacuum at 80℃ and then wound up in the drying room (dew point -40℃) to obtain the "embossed-microcavity anchored" ternary positive electrode sheet.
[0022] (5) The electrode sheets obtained in step (4) are rolled and cut, and the whole sheet is compacted to 2.85 g / cm³. 3 ; 2. Preparation of lithium-ion batteries (1) Preparation of negative electrode slurry: The negative electrode slurry was prepared according to the ratio of graphite: silicon carbide: LB212: SONE: LiTX200 of 66.4:30:0.1:3:0.5, with a solid content of 37% and a viscosity of 7200 cps; (2) Coat the negative electrode slurry onto the negative electrode current collector; the surface density on one side is 6.5 mg / cm³. -2 The areal density of both sides is 13 mg / cm³. -2 The compacted weight is 1.52 g / cm³. -3 Vacuum dry at 85℃ to remove residual solvent and moisture, then cool to 25℃ for later use. (3) The positive and negative electrodes, polyethylene (PE) as separator are stacked and lithium hexafluorophosphate (LiPF6) is used as electrolyte to prepare soft-pack batteries, and electrochemical performance and safety performance are tested.
[0023] Example 2: The only difference between Example 2 and Example 1 is that in the preparation of the positive electrode sheet, the depth of the embossed hexagonal pit in step (2) is 8 μm, and the height of the roller protrusion in step (4) is 8 μm. The rest is the same as in Example 1.
[0024] Example 3: The only difference between Example 3 and Example 1 is that in the preparation of the positive electrode sheet, the depth of the embossed hexagonal pit in step (2) is 10 μm, and the height of the roller protrusion in step (4) is 10 μm. The rest is the same as in Example 1.
[0025] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that the positive electrode is a common ternary positive electrode, that is, the positive electrode body is directly used as the positive electrode to prepare the lithium-ion battery.
[0026] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that the positive electrode sheet is a ternary positive electrode sheet with a surface coated with a self-sealing layer slurry, which is prepared by the following steps: (1) Preparation of positive electrode sheet: The positive electrode slurry was prepared according to the ratio of NCM:LITX200:CNT156:PVDF5130:HSV900 = 97.80:0.6:0.4:0.8:0.4, with a solid content of 67%, a viscosity of 6700cps, and a single-sided areal density of 23mg / cm² during coating. -2 The areal density of both sides is 46 mg / cm³. -2 Compacted density 3.5 g / cm³ -3 The positive electrode body is vacuum dried at 115℃ and cooled to 25℃ for later use; (2) Preparation of self-sealing layer slurry: STOBA:PEG-B eutectic trigger: CNT157:LiTX200:PVDF-HFP=89.5:6:1:2:1.5 was used to prepare slurry, the solvent was NMP, the solid content was 15% and the viscosity was 4500cps; (3) The slurry from step (2) is evenly coated onto the electrode sheet to a thickness of 6 μm. The electrode sheet is then vacuum dried at 80°C, rolled, and cut to a compaction density of 2.85 g / cm³. 3 .
[0027] Table 1 shows the battery performance of the embodiments and comparative examples; Table 1
[0028] Table 1 shows that Example 2 has the best overall performance. Examples 1, 2, and 3 exhibit significant safety performance advantages compared to the comparative examples. Analysis suggests that this high-safety positive electrode sheet, through the introduction of polyethylene glycol-boronate (PEG-B) and expandable self-sealing dendritic polyamide urea (STOBA), significantly reduces the trigger temperature, ensuring film formation before the thermal runaway chain reaction begins, cutting off ion / electron channels, reducing the risk of thermal runaway, and improving the safety performance of lithium-ion batteries. Example 1 did not pass the 2x voltage test due to its thin coating, but compared to the comparative example, it passed GB38031-2025, indicating a significant improvement in safety performance. While Example 3 shows a significant improvement in safety performance, its cycle stability suffers a relatively large loss. Compared to Example 2, Comparative Example 2 shows a significant improvement in safety performance, but the internal resistance of the coated electrode sheet increases significantly, reducing the battery cycle performance to 800 cycles at 80%.
[0029] Figure 2 To compare the rate discharge performance of lithium batteries in the comparative examples and different embodiments, the figures show that Examples 1, 2, and 3 show no significant loss in rate performance compared to the comparative examples. Comparative Example 2 has the worst rate performance, with a 3C / 0.2C discharge capacity retention rate of less than 70%. Meanwhile, comparing Examples 1, 2, and 3, it can be seen that Example 3, due to its thicker coating and longer ion transport path, suffers from poorer rate performance, with a 3C / 0.2C capacity retention rate of only 71.2%.
[0030] In summary, Example 2 exhibits the best performance, enabling the high-nickel ternary battery to "not catch fire or explode" under abuse conditions such as needle penetration, hot box, and overcharge, while maintaining room temperature cycling and high rate performance, thus balancing safety and electrochemical performance.
[0031] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.
[0032] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
Claims
1. A positive electrode plate, characterized in that, It includes a positive electrode body, multiple grooves disposed on the positive electrode body, and a self-sealing layer disposed within the grooves.
2. The positive electrode sheet according to claim 1, characterized in that, The groove is a hexagonal pit; preferably, the side length is 80-100um, the depth is 6-10um, and the row spacing is 150-200um; preferably, the side length is 100um, the depth is 8um, and the row spacing is 150um.
3. The positive electrode sheet according to claim 1, characterized in that, The positive electrode body includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder; Preferably, the mass ratio of the positive electrode active material, the positive electrode conductive agent, and the positive electrode binder is (95-98):(1-4):(1-4); more preferably, it is 97.8:1:1.
2. Preferably, the positive electrode active material is nickel-cobalt-manganese (NCM). Preferably, the positive electrode conductive agent is one or a mixture of CNT and carbon black; preferably, it is a mixture of CNT156 and LiTX200; preferably, the mass ratio of CNT156 to LiTX200 is 6:
4. Preferably, the positive electrode binder is PVDF; more preferably, it is a mixture of PVDF5130 and HSV900; preferably, the mass ratio of PVDF5130 to HSV900 is 8:
4.
4. The positive electrode sheet according to claim 1, characterized in that, The self-sealing layer includes polyamide urea, eutectic trigger, conductive agent, and binder; Preferably, the mass ratio of the polyamide urea, eutectic trigger, conductive agent and binder is (85-95):(1-10):(1-5):(1-5), and more preferably 89.5:6:3:1.5; Preferably, the eutectic trigger is PEG-B; Preferably, the conductive agent is one or a mixture of CNT and carbon black; preferably, it is a mixture of CNT156 and LiTX200; preferably, the mass ratio of CNT156 to LiTX200 is 1:
2. Preferably, the adhesive is PVDF-HFP.
5. A method for preparing a positive electrode sheet according to any one of claims 1-4, characterized in that, The process includes the following steps: (1) preparing a positive electrode body; (2) heating and rolling an alloy roller with a pattern printed on its surface to press the positive electrode body obtained in step (1); (3) preparing a self-sealing layer slurry; (4) rolling and transferring the self-sealing layer slurry obtained in step (3) onto the positive electrode body with grooves obtained in step (2); (5) rolling and cutting the electrode obtained in step (4) to obtain a positive electrode.
6. The preparation method according to claim 5, characterized in that, The specific steps of step (1) are as follows: A positive electrode active material, a positive electrode conductive agent, and a positive electrode binder are mixed to obtain a positive electrode slurry; preferably, the solvent of the positive electrode slurry is NMP, the solid content is 65-70%, and the viscosity is 6000-7000 cp; the positive electrode slurry is coated onto a positive electrode current collector and dried to obtain the positive electrode sheet body; preferably, the single-sided areal density during coating is 20-23 mg / cm³. -2 The areal density of both sides is 40-46 mg / cm³. -2 The compacted density is 3.4-3.6 g / cm³. -3 .
7. The preparation method according to claim 5, characterized in that, The specific steps of step (2) are as follows: heat the alloy roller with the pattern printed on the surface and roll it to press the positive electrode body obtained in step (1); the rolling temperature is 40-80℃, the linear pressure is 0.5-0.8MPa, the running speed is 10-25m / min, the online monitoring of the embossing integrity rate is ≥98%, the depth tolerance is ±1um, and the low temperature setting is performed after embossing to eliminate the springback of aluminum foil; the electrode waviness is ≤1mm / 500mm.
8. The preparation method according to claim 5, characterized in that, The specific steps of step (3) are as follows: polyamide urea, eutectic trigger, conductive agent and binder are mixed to obtain self-sealing layer slurry; the solvent of the self-sealing layer slurry is NMP, the solid content is 15-20% and the viscosity is 4000-6000cp.
9. The preparation method according to claim 5, characterized in that, The specific steps of step (4) are as follows: Roller transfer; the self-sealing layer slurry obtained in step (3) is roller transferred onto the positive electrode body with grooves obtained in step (2); the roller protrusion height is 6-10um, the thickness error is ±0.2um, the leakage rate is <0.5%, and a uniform, non-porous electrode film is obtained; the roller protrusion height is set in accordance with the groove depth; Flash drying eliminates solvent residue; preferably, flash drying at 90℃ results in solvent residue ≤200ppm. Hot pressing involves secondary pressure flow of the slurry within the groove; preferably, hot pressing is performed at 80℃, with a linear pressure of 0.5-0.8 MPa and a pressing time of 0.5-0.8 s. The electrode is dried twice under vacuum at 80℃ and then wound up in the drying room to obtain the positive electrode.
10. A lithium-ion battery, characterized in that, Includes the positive electrode and negative electrode as described in any one of claims 1-4; Preferably, the negative electrode sheet is prepared in the following manner: 1) Preparation of negative electrode slurry; the negative electrode slurry comprises the following components in the following ratio: graphite: silicon carbide: LB212: SONE: LiTX200 = 66.4:30:0.1:3:0.5; preferably, the solid content of the negative electrode slurry is 35-40%, and the viscosity is 6000-8000 cps; 2) Coating the negative electrode slurry onto the negative electrode current collector; preferably, the surface density of the coating on one side is 6-7 mg / cm³. -2 The areal density of both sides is 12-14 mg / cm³. -2 The compacted density is 2.8-3.5 g / cm³. 3 The preferred value is 1.5 ± 0.3 g cm. -3 .