A high loading dry method electrode and a method of making the same
By employing a dry electrode fabrication method involving multiple thinning and stacking, the problems of low compaction density and large electrode thickness in traditional dry electrodes have been solved. This method achieves high conductivity and short transport path for high-load electrodes, thereby improving the electrochemical performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GUIZHOU MEILING POWER SUPPLY CO LTD
- Filing Date
- 2024-08-20
- Publication Date
- 2026-05-12
Smart Images
Figure CN118825183B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of chemical energy storage battery technology, specifically to a high-load dry electrode and its preparation method. Background Technology
[0002] Lithium-ion batteries, as a new generation of electrochemical energy storage power source, are widely used in electronic products such as electric vehicles, smart grids, communication base stations, and drones due to their advantages such as high energy density, high operating voltage, low self-discharge rate, and long cycle life.
[0003] Researching the preparation of high-load electrode sheets is one of the important directions for improving the energy density of lithium-ion batteries. Compared with the traditional wet electrode preparation process, the dry process is more suitable for the preparation of high-load electrodes and has a higher theoretical energy density. In addition, dry electrodes have advantages such as low manufacturing cost and less pollution.
[0004] The traditional dry electrode fabrication process involves mixing, fiberization, hot-pressing thinning, and composite formation of a self-supporting film with a current collector. The hot-pressing thinning step involves hot-pressing the fiberized powder into a relatively thick film, typically ≥500µm thick, and then repeatedly hot-pressing to thin the film to the desired loading capacity. For high-loading electrodes, fewer hot-pressing thinning cycles are required, resulting in lower compaction density and greater thickness. However, traditional dry-process high-loading electrodes suffer from low compaction density, large electrode thickness, and high resistivity, leading to severe polarization and poor rate performance in the prepared lithium-ion batteries. Therefore, this application proposes a high-compactness, high-conductivity, high-loading dry electrode fabrication process. Summary of the Invention
[0005] The present invention aims to provide a high-load dry electrode and its preparation method. The method obtains a thin film with higher compaction density by multiple thinning, and obtains an electrode with high loading capacity by stacking and compositing. The film prepared by this method has a high compaction density, and under the same loading conditions, it is thinner, with a shorter ion / electron transport path, resulting in better power characteristics of the prepared battery.
[0006] To achieve the above objectives, the present invention provides the following technical solution:
[0007] A method for preparing a high-load dry electrode includes the following steps:
[0008] S1. The conductive agent and the binder are stirred and mixed under certain low temperature and speed conditions to obtain intermediate 1;
[0009] S2. Construction of conductive network: Intermediate 1 is stirred under certain low temperature and speed conditions to achieve low-degree fiberization and obtain intermediate 2;
[0010] S3, Active material mixing: Add active material to intermediate 2 and stir at low speed to obtain intermediate 3;
[0011] S4. Fiberization: The intermediate 3 is stirred and fiberized to obtain a granular mixture of active materials;
[0012] S5. Preparation of high-pressure self-supporting films: The active material mixture is repeatedly rolled and thinned using a hot pressing device until the compaction density reaches the set value, resulting in multiple high-pressure self-supporting films.
[0013] S6. Preparation of high-load dry electrode sheet: Multiple self-supporting films are sequentially bonded to the current collector using conductive adhesive to obtain a composite self-supporting film until the load reaches the design value. Then, the composite self-supporting film and the current collector are hot-pressed to obtain a high-load dry electrode sheet.
[0014] Working principle and beneficial effects of the present invention:
[0015] This application achieves low-level fibrosis of the binder by controlling the stirring temperature and speed, resulting in a three-dimensional conductive network structure with a uniform mixture of conductive agent and binder. Then, by repeatedly adding active material in incremental amounts, the active material is uniformly dispersed within the three-dimensional conductive network structure, yielding a high-conductivity fibrous powder. The fibrous powder prepared by this method exhibits more uniform and dense contact between the active material and the conductive agent, resulting in higher conductivity, easier compaction, and greater advantages for the preparation of high-compact self-supporting films.
[0016] Furthermore, this application describes a high-load dry electrode sheet prepared by compositing multiple high-compaction thin films. Electrodes prepared using this method exhibit higher compaction density, resulting in closer contact between the active material and the conductive agent, leading to higher electrode conductivity. Additionally, under the same loading conditions, the electrode thickness is smaller, reducing the ion / electron transport path and thus improving the rate performance of the electrode.
[0017] Optimally, the active materials used are LiCoO2, LiMn2O4, LiFePO4, and LiNi. 1-x-y Co y Mn x O2, LiNi 1-x- y Co y Al x O2, LiM x Mn 2-x O4 (where M is Fe or Co doped atoms) is used as the positive electrode material for lithium-ion batteries, or as the negative electrode material for lithium-ion batteries such as graphite, soft carbon, and hard carbon, with the active material accounting for 90% to 98% of the mass.
[0018] Ideally, the adhesive used is polytetrafluoroethylene (PTFE), and the adhesive mass percentage is 1% to 5%.
[0019] Ideally, the conductive agent used is one or more of carbon nanotubes (CNTs), superconducting carbon black (SP), conductive graphite (KS-6), and Ketjen black (KB), with the conductive agent accounting for 1% to 5% by mass.
[0020] Ideally, S1 controls the stirring speed to be between 200 and 800 r / min, the mixing temperature to be between 5 and 25°C, and the mixing time to be between 10 and 30 min.
[0021] Ideally, the stirring speed of S2 is 1500-3000 r / min, the mixing temperature is 25-50℃, and the mixing time is 10-30 min.
[0022] Ideally, the stirring speed of S3 is controlled at 200–800 r / min, and the stirring time is 10–30 min.
[0023] Ideally, in step S4, the intermediate material 3 is fiberized using a high-speed shear fiberizing device, with the stirring speed controlled at 3500–6000 r / min and the stirring time at 10–30 min.
[0024] Ideally, the hot pressing temperature in S5 is controlled at 80-150°C and the hot pressing temperature in S6 is 80-150°C, and the active material is added to the intermediate 2 in small amounts and multiple times in S3. Attached Figure Description
[0025] Figure 1 Electrode scan diagram of fibrous powder;
[0026] Figure 2 This is a comparison chart of electrode thickness;
[0027] Figure 3 Comparison chart of electrode resistance tests;
[0028] Figure 4 A comparison chart of battery specific energy tests;
[0029] Figure 5 This is a comparison chart of battery rate performance. Detailed Implementation
[0030] The following detailed description illustrates the specific implementation method:
[0031] Example 1: 30g of polytetrafluoroethylene (PTFE) and 30g of conductive carbon black (SP) were added to a high-speed mixer and stirred at 600 rpm at 25°C for 10 minutes. The speed was then increased to 1500 rpm and mixed at 30°C for 10 minutes to achieve low-level fiberization. 940g of lithium cobalt oxide (LCO) was added to the mixing tank in five portions, stirred at 600 rpm for 10 minutes each time, and then the speed was increased to 5000 rpm and mixed for 20 minutes to achieve uniform dispersion of the active material in the conductive network. The mixed powder was then hot-pressed at 120°C to a loading of 3.8g / 100cm³. 2 Two films were stacked sequentially and then hot-pressed together to obtain a loading of 7.6 g / 100 cm². 2 A self-supporting membrane is formed. The positive electrode is obtained by hot pressing the self-supporting membrane with the current collector.
[0032] Example 2: 30g of polytetrafluoroethylene (PTFE) and 30g of conductive carbon black (SP) were added to a high-speed mixer and stirred at 600 rpm at 25°C for 10 minutes. The speed was then increased to 1500 rpm and mixed at 40°C for 10 minutes to achieve low-level fiberization. 940g of lithium cobalt oxide (LCO) was added to the mixing tank in five portions, stirred at 600 rpm for 10 minutes each time, and then the speed was increased to 5000 rpm and mixed for 20 minutes to achieve uniform dispersion of the active material in the conductive network. The mixed powder was then hot-pressed at 120°C to a loading of 3.8g / 100cm³. 2 Two films were stacked sequentially and then hot-pressed together to obtain a loading of 7.6 g / 100 cm². 2 A self-supporting membrane is formed. The positive electrode is obtained by hot pressing the self-supporting membrane with the current collector.
[0033] Example 3: 30g of polytetrafluoroethylene (PTFE) and 30g of conductive carbon black (SP) were added to a high-speed mixer and stirred at 600 rpm at 25°C for 10 minutes. The speed was then increased to 1500 rpm and mixed at 30°C for 10 minutes to achieve low-level fiberization. 940g of lithium cobalt oxide (LCO) was added to the mixing tank in five portions, stirred at 600 rpm for 10 minutes each time, and then the speed was increased to 5000 rpm and mixed for 20 minutes to achieve uniform dispersion of the active material in the conductive network. The mixed powder was then hot-pressed at 120°C to a loading of 3.8g / 100cm³. 2 The three films were stacked sequentially and then hot-pressed to obtain a loading of 11.4 g / 100 cm³. 2 A self-supporting membrane is formed. The positive electrode is obtained by hot pressing the self-supporting membrane with the current collector.
[0034] Comparative Example-1: 30g of polytetrafluoroethylene (PTFE) and 30g of conductive carbon black (SP) were added to a high-speed mixer and stirred at 600 rpm at 25°C for 10 minutes. The speed was then increased to 1500 rpm and the mixture was stirred at 70°C for 10 minutes. 940g of lithium cobalt oxide (LCO) was added to the mixing tank in 5 portions, and stirred at 600 rpm for 10 minutes each time. The speed was then increased to 5000 rpm and the mixture was stirred for 20 minutes. The mixed powder was then hot-pressed at 120°C to a loading of 3.8g / 100cm³. 2 Two films were stacked sequentially and then hot-pressed together to obtain a loading of 7.6 g / 100 cm². 2 A self-supporting membrane is formed. The positive electrode is obtained by hot pressing the self-supporting membrane with the current collector.
[0035] Comparative Example-2: 30g of polytetrafluoroethylene (PTFE) and 30g of conductive carbon black (SP) were added to a high-speed mixer and stirred at 600 rpm at 25°C for 10 minutes. The speed was then increased to 1500 rpm and mixed at 30°C for 10 minutes to achieve low-level fiberization. 940g of lithium cobalt oxide (LCO) was added to a mixing tank in five portions, and stirred at 600 rpm for 10 minutes each time. The speed was then increased to 5000 rpm and mixed for 20 minutes to achieve uniform dispersion of the active material in the conductive network. The mixed powder was then hot-pressed at 120°C to a loading of 7.6g / 100cm³. 2 A self-supporting membrane is formed. The positive electrode is obtained by hot pressing the self-supporting membrane with the current collector.
[0036] Comparative Example-3: 30g of polytetrafluoroethylene (PTFE) and 30g of conductive carbon black (SP) were added to a high-speed mixer and stirred at 600 rpm at 25°C for 10 minutes. The speed was then increased to 1500 rpm and mixed at 30°C for 10 minutes to achieve low-level fiberization. 940g of lithium cobalt oxide (LCO) was added to a mixing tank in five portions, and stirred at 600 rpm for 10 minutes each time. The speed was then increased to 5000 rpm and mixed for 20 minutes to achieve uniform dispersion of the active material in the conductive network. The mixed powder was then hot-pressed at 120°C to a loading of 11.4g / 100cm³. 2 A self-supporting membrane is formed. The positive electrode is obtained by hot pressing the self-supporting membrane with the current collector.
[0037] The fibrous powders prepared in the examples and comparative examples were subjected to scanning electron microscopy (SEM) tests, such as... Figure 1 As shown. The thickness and resistivity of the electrodes prepared in the examples and comparative examples were tested, as shown. Figure 2 and Figure 3As shown. The electrodes prepared in the examples and comparative examples were combined with hard carbon (HC) negative electrodes to assemble a 1Ah pouch cell with an N / P ratio of 1.2. Lithium hexafluorophosphate electrolyte was used as the electrolyte. The pouch cell was then tested for specific energy and rate capability. Figure 4 and Figure 5 As shown.
[0038] Depend on Figure 1 It can be seen that the particle distribution in Examples 1 and 2 is more compact, while the particles in Comparative Example-1 are relatively loose, and the PTFE fibers are prone to breakage. This indicates that controlling the stirring temperature and performing low-temperature stirring can effectively prevent fiber breakage and make it easier to obtain a compacted powder. Figure 2 and Figure 3 It can be seen that, under the same load conditions, Example 1 has a thinner electrode thickness and lower electrode resistance compared to Example 2, and Example 3 has a thinner electrode thickness and lower electrode resistance compared to Comparative Example 3. This demonstrates that the multilayer thin film stacking composite method in this patent can obtain a self-supporting film with thinner thickness and lower resistance. Figure 4 and Figure 5 It can be seen that Examples 1 and 2 have higher energy density and rate performance than Comparative Examples 1 and 2, and Example 3 has higher energy density and rate performance than Comparative Example 3. This shows that the battery prepared by the dry electrode preparation method of this patent has better electrochemical performance.
Claims
1. A method for preparing a high-load dry electrode, characterized in that: Includes the following steps, S1. The conductive agent and the binder are stirred and mixed under certain low temperature and speed conditions to obtain intermediate 1; S2. Construction of conductive network: Intermediate 1 is stirred under certain low temperature and speed conditions to achieve low-degree fiberization and obtain intermediate 2; S3, Active material mixing: Add active material to intermediate 2 and stir at low speed to obtain intermediate 3; S4. Fiberization: The intermediate 3 is stirred and fiberized to obtain a granular mixture of active materials; S5. Preparation of high-pressure self-supporting films: The active material mixture is repeatedly rolled and thinned using a hot pressing device until the compaction density reaches the set value, resulting in multiple high-pressure self-supporting films. S6. Preparation of high-load dry electrode sheet: Multiple self-supporting films are bonded together sequentially using conductive adhesive to obtain a composite self-supporting film until the load reaches the design value. Then, the composite self-supporting film and the current collector are hot-pressed to obtain a high-load dry electrode sheet. The binder used is polytetrafluoroethylene (PTFE), with a binder mass ratio of 1% to 5%. The conductive agent used is one or more of carbon nanotubes (CNTs), superconducting carbon black (SP), conductive graphite (KS-6), and Ketjen black (KB), with a conductive agent mass ratio of 1% to 5%. In step S1, the stirring speed is controlled at 200 to 800 r / min, the mixing temperature at 5 to 25°C, and the mixing time at 10 to 30 min. In step S2, the stirring speed is 1500 to 3000 r / min, and the mixing temperature is 25 to 50°C. The mixing temperature is ℃, and the mixing time is 10~30min; the stirring speed in step S3 is controlled at 200~800r / min, and the stirring time is 10~30min; step S4 uses a high-speed shearing fiberization device to fiberize the intermediate 3, and the stirring speed is controlled at 3500~6000r / min, and the stirring time is 10~30min; the calendering temperature in step S5 is controlled at 80~150℃ and the hot pressing temperature in step S6 is 80~150℃, and the active material is added to the intermediate 2 in small amounts and multiple times in step S3.
2. The method for preparing a high-load dry electrode according to claim 1, characterized in that: The active materials used are LiCoO2, LiMn2O4, LiFePO4, and LiNi. 1-x-y Co y Mn x O2, LiNi 1-x-y Co y Al x O2, LiM x Mn 2-x O4, where M is the positive electrode material for Fe or Co doped lithium-ion batteries, or the negative electrode material for graphite, soft carbon, or hard carbon lithium-ion batteries, with the active material accounting for 90% to 98% of the mass.
3. The electrode prepared by the high-load dry electrode preparation method according to any one of claims 1 or 2.