Electrode solvent-free preparation method for regulating and controlling porosity of electrode through carbon material additive and application of electrode solvent-free preparation method

Abstract

The invention relates to an electrode solvent-free preparation method for regulating and controlling the porosity of an electrode through a carbon material additive and application thereof.The preparation method comprises the steps that firstly, an active material, a conductive agent, a binder and the carbon material additive serve as raw materials, the dosage is determined on the basis of the following formula, and the raw materials are mixed to be uniform, omega AM, Omega CA, Omega B and Omega AC are active materials, a conductive agent, a binder and a carbon material additive are designed in percentage by mass in the electrode plate, and rho AM, rho CA, rho B and rho AM are true densities of the active materials, the conductive agent, the binder and the carbon material additive; and carrying out dry-method tabletting, hot-pressing treatment and surface treatment in sequence to obtain the electrode. Compared with the prior art, by regulating and controlling the proportion and distribution of the carbon material additive, the porosity of the electrode is optimized so as to improve the overall performance of the lithium ion battery. The method is environment-friendly and efficient, the capacity retention ratio and the rate capability of the electrode can be remarkably improved, and the method is suitable for large-scale industrial application.

Description

Technical Field

[0001] This invention belongs to the field of chemical power source technology, and relates to an electrode manufacturing process for lithium-ion batteries, particularly a solvent-free electrode preparation method that regulates electrode porosity through carbon material additives and its application in the preparation of lithium-ion batteries as thick electrodes. Background Technology

[0002] Lithium-ion batteries, due to their high energy density, long cycle life, and environmental friendliness, have become the core energy source for portable electronic devices, electric vehicles, and large-scale energy storage systems. However, in the lithium-ion battery production process, the electrode preparation process has a crucial impact on battery performance. Currently, the mainstream electrode preparation method is the wet coating process, which involves mixing active materials, conductive agents, binders, and solvents to form a slurry, then coating the slurry onto a metal current collector (such as aluminum or copper foil), and finally removing the solvent through a drying process to form the electrode. However, this wet coating process has many limitations and problems, and solvent-free preparation methods are gradually becoming an important alternative technology. Solvents widely used in wet coating processes, such as N-methylpyrrolidone (NMP), are not only expensive but also volatile and toxic, posing potential hazards to the environment and the health of operators. Although solvent loss can be reduced through recycling equipment in modern industry, solvent handling and recycling increase equipment complexity and energy consumption. In contrast, solvent-free preparation methods completely avoid the use of solvents, greatly reducing the risk of environmental pollution and energy consumption, and meeting the current global requirements for green manufacturing and carbon neutrality. In wet coating processes, the procurement, transportation, and storage of solvents, as well as waste gas treatment systems, constitute significant cost sources. Solvent-free preparation methods, however, directly utilize powder materials for processing, eliminating solvent-related steps and equipment, thus significantly reducing production costs. Furthermore, solvent-free processes improve material utilization and reduce waste, which is crucial for lowering electrode production costs. Wet coating processes involve multiple steps, including mixing, coating, drying, and solvent recovery, while solvent-free preparation methods simplify the process by eliminating solvent mixing and drying steps. Through dry pressing or extrusion molding, solvent-free processes can directly process powder materials into shapes. This simplification not only improves production efficiency but also reduces impurities and inhomogeneities that may be introduced during the process. In wet coating processes, the viscosity of the slurry, the solvent evaporation rate, and the coating uniformity all affect the final electrode's pore structure and performance. Solvent-free preparation methods, by adjusting the proportion of powder particles, particle size distribution, and processing parameters, allow for more flexible control of the electrode's porosity and microstructure. This precise pore control helps to achieve a balance between specific capacity, rate performance, and mechanical stability in the electrode.

[0003] Despite the advantages mentioned above, controlling electrode porosity remains a significant technical challenge in practical operation. Porosity is a crucial parameter of the electrode structure, directly impacting the lithium-ion diffusion rate and overall electrode performance. Excessive porosity reduces the electrode's energy density, while insufficient porosity restricts lithium-ion transport channels, leading to decreased rate performance. Therefore, solvent-free processes require precise porosity control through optimizing the particle size, morphology, and distribution of powder particles without solvent-assisted dispersion. In wet processes, solvents act as dispersion media, aiding in uniform particle distribution and reducing random pore distribution. However, in solvent-free methods, the lack of liquid lubrication between powder particles makes them prone to agglomeration, resulting in an inhomogeneous electrode microstructure and hindering precise porosity control. Furthermore, pressing pressure and speed significantly affect porosity in solvent-free processes. Excessive pressing pressure can over-compress pores, compressing lithium-ion transport channels; insufficient pressure can compromise electrode mechanical strength, impacting overall battery reliability. Therefore, solvent-free processes require finding the optimal balance between tableting parameters and electrode porosity. While wet processes create pores through solvent evaporation, solvent-free processes rely entirely on the gaps and distribution between particles. Thus, it is necessary to introduce functional materials or optimize powder formulations to achieve stable pore formation and control.

[0004] Currently, electrode porosity is typically controlled by adding solutes soluble in the electrolyte as additives. For example, CN113328098A discloses controlling the porosity of the negative electrode sheet by adding additives dissolved in the electrolyte. However, since the solvents in the reported method may be partially or completely dissolved in the solvents used in wet coating techniques, uneven deposition of the additives due to solvent gradient evaporation during the subsequent drying process may adversely affect the pore-forming effect. Furthermore, CN117727878A discloses using solutes soluble in the electrolyte as additives to control porosity during dry electrode preparation, and points out that the additives dissolve during the subsequent addition of electrolyte for battery assembly. However, when the electrode thickness is much greater than conventional thicknesses, such as greater than 1000 micrometers, sufficient electrolyte wetting and solvent dissolution cannot be guaranteed. These methods place strict requirements on the electrode preparation process and may also adversely affect the electrode performance. Summary of the Invention

[0005] The purpose of this invention is to provide a solvent-free electrode preparation method that uses carbon material additives to regulate electrode porosity. By controlling the proportion and distribution of carbon material additives, the electrode porosity is optimized to improve the overall performance of lithium-ion batteries. This invention is not only environmentally friendly and efficient, but also significantly improves the capacity retention and rate performance of the electrode, making it suitable for large-scale industrial applications.

[0006] The objective of this invention can be achieved through the following technical solutions: A first aspect of the present invention provides a solvent-free electrode preparation method, comprising the following steps: Using active materials, conductive agents, binders, and carbon material additives as raw materials, the dosage is determined based on the following formula and the mixture is then thoroughly mixed: In the formula, e The target porosity of the electrode sheet, r coat The electrode sheet density (which can be calculated based on the thickness and loading of the target electrode. Before fabricating the electrode, the electrode density is calculated based on the known thickness of the target electrode and the loading per unit area). oh AM This represents the designed mass percentage of the active material in the electrode sheet. r AM The true density of the active material. oh CA This represents the designed mass percentage of the conductive agent in the electrode sheet. r CA The true density of the conductive agent. oh B This represents the designed mass percentage of the binder in the electrode sheet. r B The true density of the adhesive. oh AC This represents the mass percentage of carbon material additives in the electrode sheet. r AM True density of carbon material additives; The electrodes are obtained by sequentially performing dry compression and hot pressing.

[0007] Carbon materials, with their ultra-high specific surface area, exhibit unique value in solvent-free preparation methods due to their high specific surface area and specific microporous structure. Their low active capacity and high specific surface area make them not only an important component of the conductive network but also a crucial tool for pore structure regulation. Carbon materials typically possess a specific surface area of ​​hundreds to thousands of square meters per gram, and their microporous structure can significantly improve electrode porosity. During mixing, carbon particles can act as a "supporting framework," forming a stable pore network during tableting, thus ensuring smooth lithium-ion transport. While carbon materials generally have a low specific capacity and good chemical stability, their contribution to the overall capacity of lithium-ion batteries is limited. However, this low capacity characteristic allows for optimization of the pore structure without significantly reducing the overall energy density of the electrode. This characteristic makes carbon materials play a key role in balancing electrode porosity and capacity. The porosity distribution can be further optimized by adjusting the particle size distribution of the carbon materials. For example, using large-particle-size carbon materials can generate larger transport channels, while small-particle-size carbon materials can fill micropores, providing a more uniform pore distribution. This multi-particle-size synergistic distribution strategy provides an important approach for achieving precise control of porosity in solvent-free processes.

[0008] This invention utilizes low-cost, commercially available carbon materials as the pores of the electrode. It leverages the low density, high specific surface area, and excellent conductivity of carbon materials to create pores and increase porosity. On one hand, carbon materials possess very low theoretical specific capacity and good chemical stability, ensuring they do not affect the performance and stability of the electrode active material. Simultaneously, the conductivity of carbon materials guarantees the continuity of the electron conduction pathway within the electrode, preventing the formation of dead zones due to interrupted electron pathways caused by electrode pores.

[0009] Furthermore, the carbon material additive is selected from activated carbon, acetylene black, or Ketjen black, with a particle size distribution of 10-50 nm. oh AC ≤30%.

[0010] Furthermore, the active material is selected from one of lithium iron phosphate (LiFePO4), graphite, lithium nickel cobalt manganese oxide ternary material (NCM), or silicon carbide (SiC); The conductive agent is selected from SuperP, vapor-grown carbon fiber (VGCF), single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT), etc.

[0011] Furthermore, the adhesive is selected from one of polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), or styrene-butadiene rubber (SBR).

[0012] Furthermore, the mixing process employs one of mechanical stirring, airflow mixing, planetary ball milling, or mortar grinding. By thoroughly mixing and homogenizing the above raw materials, the particle distribution of the mixture is ensured to be uniform, and the powder has good flowability.

[0013] Furthermore, in the dry tableting process, the compression pressure is 5~20 MPa.

[0014] Furthermore, in the hot pressing process, the hot pressing temperature is 100~150℃, the hot pressing pressure is 1.5~2.5 MPa, the hot pressing pressure is preferably 1.7 MPa, and the hot pressing time is preferably 10~60 min.

[0015] Furthermore, the electrode has a porosity of 10-55% and a thickness of 10-3000 μm.

[0016] A second aspect of the present invention provides the application of an electrode prepared by any of the methods described above in the preparation of lithium-ion batteries as a thick electrode.

[0017] Compared with the prior art, the present invention has the following characteristics: The preparation method provided by this invention combines solvent-free preparation with carbon material-based porosity control. During the solvent-free preparation of the thick electrode, a certain amount of carbon material is introduced as a pore-forming agent to control the electrode porosity. The added activated carbon is uniformly dispersed inside the electrode, forming a porous electrode structure with uniform pore size and controllable porosity. The carbon material used in this invention does not introduce any potential additional residual substances during the thick electrode preparation process and can also act as a conductive aid dispersed inside the thick electrode, helping to improve its conductivity. This achieves the preparation of a thick electrode with controllable porosity, thereby improving battery performance.

[0018] This invention offers advantages in the precision and range of porosity control. At high porosity, the introduction of carbon materials can maintain the integrity of the electrode structure to a certain extent, preventing excessively large pores from causing structural collapse. The density and specific surface area of ​​the same carbon material are very stable; by controlling the carbon content, the electrode porosity can be controlled, effectively avoiding the problems of additive residue and incomplete pore formation caused by the sacrificial phase of organic additives used in existing technologies (such as CN117727878A) to adjust electrode porosity. Attached Figure Description

[0019] Figure 1 The images shown are SEM images of the surface morphology of the electrode sheets in Examples 1, 2, 3 and 4, where Figures A, B, C and D are the surface images of the electrode sheets with target porosities of 10%, 20%, 25% and 35%, respectively.

[0020] Figure 2 The images are SEM images processed by computer image processing software. Figures A, B, C, and D are images of the electrode surface with target porosities of 10%, 20%, 25%, and 35%, respectively. The white areas are the pore areas fitted by the software.

[0021] Figure 3 This shows the correspondence between the carbon material content of the electrode sheet and the target porosity and actual porosity in Examples 1, 2, 3 and 4.

[0022] Figure 4 This is a comparison of the rate performance of half-cells assembled with electrodes of four different carbon material contents in Examples 1, 2, 3 and 4.

[0023] Figure 5 The capacity data for the half-cells assembled with electrodes from Example 1 and Comparative Example 1 under long-term cycling at 0.1C are shown. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0025] The following are more detailed implementation examples, which further illustrate the technical solution of the present invention and the technical effects that can be obtained.

[0026] In the following embodiments, unless otherwise specified, the raw materials, reagents or processing techniques are all conventional commercial products or conventional processing techniques in the art.

[0027] Example 1 A solvent-free method for preparing lithium-ion battery electrodes by controlling electrode porosity through carbon material additives includes the following steps: Step 1: Lithium iron phosphate (LFP) was selected as the electrode active material, SuperP as the conductive agent, polytetrafluoroethylene (PTFE) as the binder, and activated carbon (AC) as the carbon material additive. The target porosity of the electrode was 10%, and the bulk density was 2.5 g / cm³. -3 .

[0028] Step 2: According to the formula: Substitute into e (10%) r coat (2.5g cm) -3 ), oh AM (93.5%) oh CA (3%) oh B (3.5%) r AM (3.5 g cm) -3 ), r CA (2.0 g cm) -3 ), r B (2.2 g cm) -3 ), r AC (0.39 g cm) -3 ), calculated oh CA It is 4.33%.

[0029] Step 3: Weigh a certain amount of LFP, SuperP and PTFE in a mass ratio of 93.5:3:3.5, and additionally weigh 2.41%wt (total amount of LFP, SuperP and PTFE) of activated carbon additive. After mixing the materials, place them in a high-speed mixer at a stirring speed of 4500 rpm for 210 s. Use high-speed shear stress to fiberize the binder, and at the same time, fully mix and homogenize the above raw materials to ensure that the particle distribution of the mixture is uniform and the powder has good uniformity.

[0030] Step 4: Use a hot roller press at 120℃ to press the uniformly mixed powder material into sheet electrodes. The roller linear speed is 0.75 m / min, and the roller pressure is 1.8 t.

[0031] Step 5: The pressed electrode is subjected to hot pressing treatment at 120℃ and 2.0MPa for 60s to improve the mechanical strength and conductivity of the electrode, and further optimize the stability of porosity.

[0032] Example 2 A solvent-free method for preparing lithium-ion battery electrodes by controlling electrode porosity through carbon material additives includes the following steps: Step 1: Lithium iron phosphate (LFP) was selected as the electrode active material, SuperP as the conductive agent, polytetrafluoroethylene (PTFE) as the binder, and activated carbon (AC) as the carbon material additive. The target porosity of the electrode was 20%, and the bulk density was 2.5 g / cm³. -3 .

[0033] Step 2: According to the formula: Substitute into e (20%) r coat (2.5g cm) -3 ), ohAM (93.5%) oh CA (3%) oh B (3.5%) r AM (3.5 g cm) -3 ), r CA (2.0 g cm) -3 ), r B (2.2 g cm) -3 ), r AC (0.39 g cm) -3 ), calculated oh AC It is 2.56%.

[0034] Step 3: Weigh a certain amount of LFP, SuperP and PTFE in a mass ratio of 93.5:3:3.5, and additionally weigh 0.86 wt (total amount of LFP, SuperP and PTFE) of activated carbon additive. After mixing the materials, place them in a high-speed mixer at a stirring speed of 4500 rpm for 210 s. Use high-speed shear stress to fiberize the binder, and at the same time, fully mix and homogenize the above raw materials to ensure that the particle distribution of the mixture is uniform and the powder has good uniformity.

[0035] Step 4: Use a hot roller press at 120℃ to press the uniformly mixed powder material into sheet electrodes. The roller linear speed is 0.75 m / min, and the roller pressure is 1.8 t.

[0036] Step 5: The pressed electrode is subjected to hot pressing treatment at 120℃ and 2.0MPa for 60s to improve the mechanical strength and conductivity of the electrode, and further optimize the stability of porosity.

[0037] Example 3 A solvent-free method for preparing lithium-ion battery electrodes by controlling electrode porosity through carbon material additives includes the following steps: Step 1: Lithium iron phosphate (LFP) was selected as the electrode active material, SuperP as the conductive agent, polytetrafluoroethylene (PTFE) as the binder, and activated carbon (AC) as the carbon material additive. The target porosity of the electrode was 25%, and the bulk density was 2.2 g / cm³. -3 .

[0038] Step 2: According to the formula: Substitute into e (25%) rcoat (2.2g cm) -3 ), oh AM (93.5%) oh CA (3%) oh B (3.5%) r AM (3.5 g cm) -3 ), r CA (2.0 g cm) -3 ), r B (2.2 g cm) -3 ), r AC (0.39 g cm) -3 ), calculated oh AC It is 1.67%.

[0039] Step 3: Weigh a certain amount of LFP, SuperP and PTFE in a mass ratio of 93.5:3:3.5, and additionally weigh 1.67 wt (total amount of LFP, SuperP and PTFE) of activated carbon additive. After mixing the materials, place them in a high-speed mixer at a stirring speed of 4500 rpm for 210 s. Use high-speed shear stress to fiberize the binder, and at the same time, fully mix and homogenize the above raw materials to ensure that the particle distribution of the mixture is uniform and the powder has good uniformity.

[0040] Step 4: Use a hot roller press at 120℃ to press the uniformly mixed powder material into sheet electrodes. The roller linear speed is 0.75 m / min, and the roller pressure is 1.8 t.

[0041] Step 5: The pressed electrode is subjected to hot pressing treatment at 120℃ and 2.0MPa for 60s to improve the mechanical strength and conductivity of the electrode, and further optimize the stability of porosity.

[0042] Example 4 A solvent-free method for preparing lithium-ion battery electrodes by controlling electrode porosity through carbon material additives includes the following steps: Step 1: Lithium iron phosphate (LFP) was selected as the electrode active material, SuperP as the conductive agent, polytetrafluoroethylene (PTFE) as the binder, and activated carbon (AC) as the carbon material additive. The target porosity of the electrode was 30%, and the bulk density was 2.2 g / cm³. -3 .

[0043] Step 2: According to the formula: Substitute into e (30%) r coat (2.2g cm) -3 ), oh AM (93.5%) oh CA (3%) oh B (3.5%) r AM (3.5 g cm) -3 ), r CA (2.0 g cm) -3 ), r B (2.2 g cm) -3 ), r AC (0.39 g cm) -3 ), calculated oh AC It is 0.79%.

[0044] Step 3: Weigh a certain amount of LFP, SuperP and PTFE in a mass ratio of 93.5:3:3.5, and additionally weigh 0.79%wt (total amount of LFP, SuperP and PTFE) of activated carbon additive. After mixing the materials, place them in a high-speed mixer at a stirring speed of 4500 rpm for 210 s. Use high-speed shear stress to fiberize the binder, and at the same time, fully mix and homogenize the above raw materials to ensure that the particle distribution of the mixture is uniform and the powder has good uniformity.

[0045] Step 4: Use a hot roller press at 120℃ to press the uniformly mixed powder material into sheet electrodes. The roller linear speed is 0.75 m / min, and the roller pressure is 1.8 t.

[0046] Step 5: The pressed electrode is subjected to hot pressing treatment at 120℃ and 2.0MPa for 60s to improve the mechanical strength and conductivity of the electrode, and further optimize the stability of porosity.

[0047] Figure 1 The images shown are SEM images of the electrode surface morphology in Examples 1, 2, 3, and 4, where Figures A, B, C, and D are electrode surface images with target porosities of 10%, 20%, 25%, and 30%, respectively. It can be seen that as the carbon (AC) content in the electrode increases, the degree of structural fragmentation on the electrode surface gradually increases, revealing more surface pores. Figure 2The image is a SEM image after grayscale processing and void identification using computer image processing software (ImageJ). The white area represents the void area fitted by the software. It can also be observed that the void area on the electrode surface increases significantly with the increase of carbon material content. Figure 3 Based on mercury intrusion porosimetry tests, the actual porosities of the electrode sheets in the four embodiments were 9.07%, 19.55%, 24.88%, and 35.54%, respectively. Figure 4 The comparison of the rate performance of the four types of electrodes shows that increasing the content of carbon material additives to increase the porosity of the electrode can significantly improve the performance of the electrode under high-rate discharge.

[0048] Example 5 A solvent-free method for preparing lithium-ion battery electrodes by controlling electrode porosity through carbon material additives includes the following steps: Step 1: Graphite (Gr) was selected as the electrode active material, SuperP as the conductive agent, polytetrafluoroethylene (PTFE) as the binder, and activated carbon (AC) as the carbon material additive. The target porosity of the electrode was 20%, and the bulk density was 1.5 g / cm³. -3 .

[0049] Step 2: According to the formula: Substitute into e (20%) r coat (1.5g cm) -3 ), oh AM (94%) oh CA (3%) oh B (3%) r AM (2.23 g cm) -3 ), r CA (2.0 g cm) -3 ), r B (2.2 g cm) -3 ), r AC (0.39 g cm) -3 ), calculated oh AC It is 3.24%.

[0050] Step 3: Weigh a certain amount of Gr, SuperP and PTFE in a mass ratio of 94:3:3, and additionally weigh 3.24%wt of activated carbon additive. After mixing the materials, place the mixture in a high-speed mixer at a speed of 4000 rpm for 180 seconds. Use high-speed shear stress to fiberize the binder, while fully mixing and homogenizing the above raw materials to ensure uniform particle distribution and good powder uniformity.

[0051] Step 4: Press the uniformly mixed powder material into sheet electrodes using a hot roller press at 120℃. The roller linear speed is 0.9 m / min, and the roller pressure is 1.2 t.

[0052] Step 5: The pressed electrode is subjected to hot pressing at 120℃ and 1.5MPa for 60s to improve the mechanical strength and conductivity of the electrode, and further optimize the stability of porosity.

[0053] Example 6 A solvent-free method for preparing lithium-ion battery electrodes by controlling electrode porosity through carbon material additives includes the following steps: Step 1: Lithium nickel cobalt manganese oxide (NCM811) was selected as the electrode active material, SuperP as the conductive agent, polytetrafluoroethylene (PTFE) as the binder, and activated carbon (AC) as the carbon material additive. The target porosity of the electrode was 20%, and the bulk density was 2.2 g / cm³. -3 .

[0054] Step 2: According to the formula: Substitute into e (20%) r coat (2.2g cm) -3 ), oh AM (92%) oh CA (4%) oh B (4%) r AM (3.6 g cm) -3 ), r CA (2.0 g cm) -3 ), r B (2.2 g cm) -3 ), r AC (0.39 g cm) -3 ), calculated oh ACIt is 2.72%.

[0055] Step 3: Weigh a certain amount of NCM811, SuperP and PTFE in a mass ratio of 92:4:4, and additionally weigh 2.72%wt of activated carbon additive. After mixing the materials, place the mixture in a high-speed mixer at a speed of 4500 rpm for 210 s. Use high-speed shear stress to fiberize the binder, and at the same time, thoroughly mix and homogenize the above raw materials to ensure that the particle distribution of the mixture is uniform and the powder has good uniformity.

[0056] Step 4: Use a hot roller press at 120℃ to press the uniformly mixed powder material into sheet electrodes. The roller linear speed is 0.6 m / min, and the roller pressure is 2 t.

[0057] Step 5: The pressed electrode is subjected to hot pressing treatment at 120℃ and 2MPa for 60s to improve the mechanical strength and conductivity of the electrode, and further optimize the stability of porosity.

[0058] Comparative Example 1 A lithium-ion battery electrode prepared by a solvent-free method includes the following steps: Step 1: Weigh and mix the active material lithium iron phosphate (LFP), SuperP conductive agent, and polytetrafluoroethylene (PTFE) binder of the positive electrode of lithium-ion battery in a ratio of 93.5:3:3.5 wt%.

[0059] Step 2: After mixing the materials, place the mixed materials in a high-speed mixer at a speed of 4500 rpm for 210 seconds. Use high-speed shear stress to fiberize the binder, and at the same time, fully mix and homogenize the above raw materials to ensure that the particle distribution of the mixture is uniform and the powder has good uniformity.

[0060] Step 3: The uniformly mixed powder material is pressed into sheet electrodes using a hot roller press at 120℃. The roller linear speed is 0.7 m / min, and the roller pressure is 2 t.

[0061] Step 4: The pressed electrode is subjected to hot pressing treatment at 120℃ and 2MPa for 60s to improve the mechanical strength and conductivity of the electrode, and further optimize the stability of porosity.

[0062] Comparative Example 2 A lithium-ion battery electrode prepared by a solvent-free method includes the following steps: Step 1: Weigh and mix the ternary material (NCM), carbon nanotube conductive agent, and polytetrafluoroethylene (PTFE) binder for the positive electrode of lithium-ion batteries in a ratio of 92:4:4wt%.

[0063] Step 2: Place the mixed materials in a high-speed mixer and use high-speed shear stress to fiberize the binder. At the same time, thoroughly mix and homogenize the above raw materials to ensure that the particle distribution of the mixture is uniform and the powder has good homogeneity.

[0064] Step 4: Use a hot roller press at 120℃ to press the uniformly mixed powder material into sheet electrodes. The roller linear speed is 0.6 m / min, and the roller pressure is 2 t.

[0065] Step 5: The pressed electrode is subjected to hot pressing treatment at 120℃ and 2MPa for 60s to improve the mechanical strength and conductivity of the electrode, and further optimize the stability of porosity.

[0066] Figure 5 The half-cells assembled with electrodes containing 20% ​​carbon material and Comparative Example 1 are shown to have capacity data under long-term cycling at 0.1C. Compared with Comparative Example 1 and Comparative Example 2, the electrode of Example 1 has a significant advantage in electrode capacity due to the increase in electrode thickness and porosity.

[0067] Application Examples Porosity measurement: The prepared electrode sheet was cut into 5 x 5 mm square samples and dried at 80℃ for 12 h to ensure thorough drying. The samples were then placed in a dilatometer for testing at pressures ranging from 0.1 to 400 MPa. Each sample was tested three times, and the average value was taken.

[0068] Electrochemical performance testing: The prepared electrode sheets were cut to a diameter of 12 mm and then vacuum dried in an 80℃ vacuum oven for 24 h. After drying, the electrodes were assembled with lithium sheets to form CR 2032 half-cells, and rate and long-cycle tests were performed using an electrochemical testing instrument. The test voltage range for lithium iron phosphate batteries was 2.5-4.2V, and the test voltage range for nickel-cobalt-manganese lithium oxide batteries was 2.8-4.3V.

[0069] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A solvent-free electrode preparation method, characterized in that, Includes the following steps: Using active materials, conductive agents, binders, and carbon material additives as raw materials, the dosage is determined based on the following formula and the mixture is then thoroughly mixed: In the formula, ε The target porosity of the electrode sheet, ρ coat The electrode sheet density, ω AM This represents the designed mass percentage of the active material in the electrode sheet. ρ AM The true density of the active material. ω CA This represents the designed mass percentage of the conductive agent in the electrode sheet. ρ CA The true density of the conductive agent. ω B This represents the designed mass percentage of the binder in the electrode sheet. ρ B The true density of the adhesive. ω AC This represents the mass percentage of carbon material additives in the electrode sheet. ρ AM True density of carbon material additives; The electrodes are obtained by sequentially performing dry compression and hot pressing.

2. The solvent-free electrode preparation method according to claim 1, characterized in that, The carbon material additive is selected from activated carbon, acetylene black, or Ketjen black, with a particle size distribution of 10-50 nm. ω AC ≤30%.

3. The solvent-free electrode preparation method according to claim 1, characterized in that, The active material is selected from one of lithium iron phosphate, graphite, lithium nickel cobalt manganese oxide ternary materials, or silicon carbon. The conductive agent is selected from at least one of SuperP, vapor-grown carbon fiber, single-walled carbon nanotubes, or multi-walled carbon nanotubes.

4. The solvent-free electrode preparation method according to claim 1, characterized in that, The adhesive is selected from one of polytetrafluoroethylene, polyvinylidene fluoride, or styrene-butadiene rubber.

5. The solvent-free electrode preparation method according to claim 1, characterized in that, The mixing is performed using one of the following methods: mechanical stirring, airflow mixing, planetary ball milling, or mortar grinding.

6. The solvent-free electrode preparation method according to claim 1, characterized in that, In the dry tableting process, the compression pressure is 5~20 MPa.

7. The solvent-free electrode preparation method according to claim 1, characterized in that, In the hot pressing process, the hot pressing temperature is 100~150℃ and the hot pressing pressure is 1.5~2.5 MPa.

8. The solvent-free electrode preparation method according to claim 7, characterized in that, In the hot pressing process, the hot pressing pressure is 1.7 MPa.

9. The solvent-free electrode preparation method according to claim 1, characterized in that, The electrode has a porosity of 10-55% and a thickness of 10-3000 μm.

10. The use of an electrode prepared by the method according to any one of claims 1 to 9 in the preparation of lithium-ion batteries as a thick electrode.

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