A high-rate composite electrode for semi-solid batteries and a method of preparing the same
By constructing a double-layer cathode on the current collector and using a composite electrode design of porous conjugated conductive polymer and low-porosity cathode material, the problems of complex interfacial reactions and poor transport capacity of semi-solid lithium-ion batteries are solved, and the high-rate performance and cycle stability are improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HUAZHONG UNIV OF SCI & TECH
- Filing Date
- 2024-05-30
- Publication Date
- 2026-07-14
Smart Images
Figure CN118572024B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semi-solid-state battery technology, and more specifically, relates to a high-rate composite electrode for semi-solid-state batteries and its preparation method. Background Technology
[0002] Since their commercialization, lithium-ion batteries have gained widespread attention worldwide due to their advantages such as high efficiency, light weight, and environmental friendliness. Currently, lithium-ion batteries are used in various aspects of our lives, such as mobile phones, smart laptops, and large-scale energy storage power stations. In recent years, with continuous technological advancements in lithium-ion batteries, breakthroughs in energy density and power density have led to their rapid adoption and promotion in new energy electric vehicles. However, limited by the theoretical specific capacity of electrode materials, the driving range of electric vehicles is unlikely to be significantly improved in the short term. Furthermore, frequent electric vehicle fires have prompted battery experts to develop safer power batteries.
[0003] Solid-state lithium-ion batteries, due to their use of solid electrolytes, avoid the use of flammable organic electrolytes and separators. The anode can be a higher-energy-density metallic lithium anode, thus significantly improving battery safety and energy density, making them considered the most promising next-generation power battery system. However, current solid-state lithium-ion batteries suffer from poor contact interfaces, slow kinetics leading to excessive interfacial impedance, and their rate performance needs improvement, preventing large-scale vehicle adoption. Furthermore, solid-state electrolytes face challenges such as immature manufacturing processes and high costs. Therefore, many battery manufacturers have chosen a compromise strategy, opting to develop semi-solid-state batteries. The cathode is the core component of the battery, but current designs for cathodes are generally inadequate. Even with the addition of small amounts of liquid electrolytes or gel electrolytes, the cathode still exhibits complex interfacial reactions and poor ion and electron transport capabilities, causing the battery to fall far short of its designed energy density. Summary of the Invention
[0004] To address the aforementioned deficiencies or improvement needs of existing technologies, the present invention aims to provide a high-rate composite electrode for semi-solid-state batteries and its preparation method. This involves constructing a double-layer electrode on a current collector, wherein the first positive electrode layer near the current collector uses a porous conjugated conductive polymer with a higher porosity than the second positive electrode layer further away from the current collector. This allows for a gradient capillary force design along the longitudinal dimension of the electrode, facilitating electrolyte enrichment and improving the rate performance of the semi-solid-state battery. The resulting positive electrode exhibits high rate capability, improving issues such as poor transport dynamics and interface stability within the positive electrode of semi-solid-state batteries. This, in turn, enhances the energy density and cycle stability of the semi-solid-state battery, clearly distinguishing it from traditional positive electrode structures (which often employ a one-step coating process, resulting in only a single positive electrode layer).
[0005] To achieve the above objectives, according to one aspect of the present invention, a composite electrode for a semi-solid-state battery is provided, characterized in that it comprises, from bottom to top, a current collector, a first positive electrode layer, and a second positive electrode layer, wherein the first positive electrode layer is formed by coating and rolling raw materials including a porous conjugated conductive polymer, a first positive electrode material powder, and a binder, and the second positive electrode layer is formed by rolling raw materials including a second positive electrode material powder, polytetrafluoroethylene, a solid electrolyte powder, and a conductive agent.
[0006] Furthermore, the porosity of the first positive electrode layer is greater than that of the second positive electrode layer.
[0007] As a further preferred embodiment of the present invention, the thickness of the first positive electrode layer is 100-300 μm, and the thickness of the second positive electrode layer is 20-80 μm;
[0008] The porosity of the first positive electrode layer is 25-35%, and the porosity of the second positive electrode layer is 10-20%.
[0009] As a further preferred embodiment of the present invention, the compaction density of the first positive electrode layer is 2.3–4.3 g / cm³. -2 The compaction density of the second positive electrode layer is 3.05–4.5 g / cm³. -2 Furthermore, the compaction density of the second positive electrode layer is greater than that of the first positive electrode layer.
[0010] As a further preferred embodiment of the present invention, the porous conjugated conductive polymer is specifically at least one of polypyrrole, polyaniline, and polydioxythiophene.
[0011] The first cathode material powder and the second cathode material powder are independently selected from lithium iron phosphate, ternary materials, and lithium-rich manganese-based materials.
[0012] As a further preferred embodiment of the present invention, the solid electrolyte powder is specifically made of perovskite-type LLTO, garnet-structured LLZO, or glass-ceramic Li7P3S. 11 tetragonal Li 10 GeP2S 12 tetragonal Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Lithium-silver-germanium ore type 5.5 PS 4.5 Cl 1.5 Lithium-silver-germanium ore type 6.6 Si 0.6 Sb 0.4 At least one of S5I.
[0013] As a further preferred embodiment of the present invention, in the second positive electrode layer, the proportion of solid electrolyte powder in the sum of the mass of the second positive electrode material powder, polytetrafluoroethylene, solid electrolyte powder and conductive agent is 5% to 25%.
[0014] The conductive agent is specifically at least one of carbon nanofibers (CNF), carbon nanotubes (CNT), graphene, activated carbon, acetylene black, Ketjen black, and super P.
[0015] According to another aspect of the present invention, the present invention provides a method for preparing the above-mentioned composite electrode for semi-solid-state batteries, characterized by comprising the following steps:
[0016] S1. Prepare a porous conjugated conductive polymer with a pore size of 15–40 nm and a specific surface area of 20–50 m². 2 g -1 ;
[0017] S2. Prepare a slurry by mixing the porous conjugated conductive polymer, the first positive electrode material powder, the binder and the solvent, coat it on the current collector, and then dry and roll it to obtain the first positive electrode layer.
[0018] S3. Based on dry processing, the second positive electrode material powder, polytetrafluoroethylene, solid electrolyte powder and conductive agent are fully mixed and formed into a self-supporting film by hot rolling. Then, the self-supporting film is rolled onto the first positive electrode to obtain a composite electrode for semi-solid batteries.
[0019] As a further preferred embodiment of the present invention, the porous conjugated conductive polymer is specifically at least one of polypyrrole, polyaniline, and polydioxythiophene.
[0020] Step S1 specifically involves completely dissolving the monomers, surfactants, and initiators of the conductive polymer in water or ethanol, and obtaining a porous conjugated conductive polymer by centrifugal drying.
[0021] Specifically, the monomer of the conductive polymer is at least one of aniline, pyrrole, and dioxothiophene;
[0022] The surfactant is one of hexadecyltrimethylammonium bromide, sodium alkyl sulfonate, sodium alkyl aryl sulfonate, sodium alkyl sulfate, and sodium secondary alkyl sulfate; preferably, the sodium alkyl sulfonate is sodium dodecyl sulfonate, the sodium alkyl aryl sulfonate is sodium dodecylbenzene sulfonate, and the sodium alkyl sulfate is sodium dodecyl sulfate.
[0023] As a further preferred embodiment of the present invention, in step S2, the porous conjugated conductive polymer accounts for 0.5% to 5.0% of the total mass of the porous conjugated conductive polymer, the first positive electrode material powder, and the binder.
[0024] According to another aspect of the present invention, the present invention provides a semi-solid lithium-ion battery, characterized in that its positive electrode is a composite electrode used in the above-mentioned semi-solid battery, and a liquid electrolyte or gel electrolyte is added thereto.
[0025] Compared with the prior art, the present invention, through the above-described technical solution, sequentially sets a first positive electrode and a second positive electrode on the current collector. The first positive electrode layer closer to the current collector uses a porous conjugated conductive polymer with a porosity greater than that of the second positive electrode layer farther from the current collector. This enables the design of gradient capillary force in the longitudinal dimension of the electrode, which helps to enrich the electrolyte and improve the rate performance of the semi-solid battery.
[0026] The first positive electrode layer uses a porous conjugated conductive polymer (e.g., polypyrrole, polyaniline, polydioxythiophene), which not only increases the electrode porosity, aids in electrolyte enrichment, and improves the rate performance of the semi-solid-state battery, but also improves the conductivity inside the electrode. Adding a solid electrolyte to the second positive electrode layer (the amount of solid electrolyte can be small, i.e., the solid electrolyte powder accounts for 5% to 25% of the total mass of the second positive electrode material powder, polytetrafluoroethylene, solid electrolyte powder, and conductive agent) significantly improves ionic conductivity. The second positive electrode layer in this invention has even lower porosity (preferably prepared using a dry method). Combined with the porous conjugated conductive polymer and the high-porosity first positive electrode layer, a gradient porosity distribution can be achieved throughout the battery, reducing electrolyte residue, minimizing interfacial side reactions, improving the cycle stability of the semi-solid-state battery, and providing high-rate performance. Furthermore, because this invention reduces the amount of electrolyte used, it also improves battery safety.
[0027] During the research and development phase of this invention, the design of the composite electrode, the selection of conductive agents, and the coating process of the slurry were thoroughly screened. Traditional conductive agents have small dimensions and high specific surface areas, making it difficult to design composite electrodes with gradient porosity. To achieve high porosity, a high amount of conductive agent needs to be added to the electrode, making it difficult to meet practical requirements for the overall energy density of the battery. When rolling the second layer of the electrode, applying higher pressure is required to achieve lower porosity, which can easily affect the porosity of the first layer of the electrode. On the other hand, an excessively high specific surface area of the conductive agent will lead to a significant increase in the amount of solvent used in the slurry preparation process, requiring a longer time and higher energy consumption for solvent drying. In addition, the wetting effect is poor when adding a small amount of electrolyte later. Therefore, this invention selects a porous conjugated conductive polymer with a relatively small specific surface area and superior conductivity as the conductive agent in the electrode preparation. Traditional slurry preparation processes require a large amount of solvent and a long stirring time, while the solid electrolytes used (such as the sulfide solid electrolytes used in the later examples) are often materials sensitive to air and water, making traditional processes unsuitable. Furthermore, simply mixing and pressing solid electrolyte and cathode material powder to prepare the second layer results in poor interface contact between the two layers of the composite electrode and between the second electrode and the solid electrolyte, which is detrimental to ion / electron transport at the interface. Therefore, a dry process was selected in this invention. The dry process is simple to prepare, requires no solvent addition, avoids the solvent drying process, and produces electrodes with higher compaction density, meeting the needs of practical applications. In addition, incorporating a certain amount of conductive agent (such as conductive carbon) into the second electrode further improves the electrode's conductivity.
[0028] Specifically, the present invention can achieve the following beneficial effects:
[0029] 1. Traditional coating processes often use small-sized conductive agents, resulting in poor electrode conductivity after assembling semi-solid-state batteries. Even with the addition of a small amount of electrolyte, the ionic / electronic conductivity of the electrode cannot be guaranteed, and side reactions at the positive and negative electrode interfaces cannot be effectively suppressed. This invention employs two coating processes to prepare a composite electrode with gradient capillary forces in the longitudinal dimension. On the side near the current collector, a porous conjugated conductive polymer is used, utilizing its capillary action to facilitate electrolyte enrichment, thereby significantly improving lithium-ion kinetics in the longitudinal direction. On the side away from the current collector, a low-porosity, high-density positive electrode is prepared using solid electrolyte powder, minimizing electrolyte residue and improving interfacial stability.
[0030] 2. This invention selects a porous conjugated conductive polymer as the conductive agent for the first positive electrode layer, which significantly improves the conductivity of the first positive electrode layer. Compared with existing technologies, this invention solves the problem of slow and insufficient lithium-ion diffusion in traditional electrodes in lithium batteries, thus contributing to the performance of semi-solid-state batteries. Thanks to the porous structure and excellent flexibility of the conductive polymer, it can buffer large volume strain in the electrode.
[0031] 3. Furthermore, the present invention utilizes a conjugated conductive polymer, which inherits the advantages of known conjugated conductive polymers in the prior art. For example, heteroatoms on the conjugated conductive polymer, such as oxygen and nitrogen, exhibit a strong adsorption effect on lithium ions, which can improve the rapid wetting of the electrolyte in the electrode and inhibit lithium dendrite growth, thereby improving the coulombic efficiency and long-cycle performance of the battery. In addition, the use of conjugated conductive polymers can broaden the operating temperature range of the battery.
[0032] 4. The high-rate composite electrode for semi-solid-state batteries obtained by this invention can be prepared through a two-step rolling process, improving the problems of poor transport dynamics and interface stability within the positive electrode in semi-solid-state batteries, thereby enhancing the energy density and cycle stability of the semi-solid-state batteries. The second positive electrode layer in this invention can be prepared using a dry process, which is highly operable, has low manufacturing costs, and can also maximize the protection of the solid electrolyte from contamination. Furthermore, the use of a dry process for the second positive electrode layer allows for precise control of the electrode thickness, resulting in higher compaction density and superior mechanical properties, which helps improve the interfacial contact between the active components and the solid electrolyte, thus enhancing the electrode's ion conductivity. Attached Figure Description
[0033] Figure 1 This is a flowchart of a method for preparing a high-rate composite electrode for a semi-solid-state battery according to the present invention.
[0034] Figure 2 This is a schematic diagram of the component distribution in a high-rate composite electrode for semi-solid batteries according to the present invention. Detailed Implementation
[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.
[0036] The method for preparing the high-rate composite electrode for semi-solid-state batteries in this invention generally involves first preparing a porous conjugated conductive polymer (such as polypyrrole, polyaniline, or polydioxythiophene) according to existing technology. Specifically, the preparation process may involve completely dissolving the monomer, surfactant, and initiator of the conductive polymer in water or ethanol, and obtaining the porous conjugated conductive polymer by centrifugal drying. The polymerization method may be one of the following: direct oxidation of monomers, free radical coupling, deprotonation, or chain growth. The polymerization temperature may be -20 to 60°C. Then, a first positive electrode layer and a second positive electrode layer are sequentially prepared on a current collector.
[0037] Taking the use of aluminum foil current collector as an example, the prepared porous conjugated conductive polymer, the first positive electrode material powder, and the binder can be mixed and slurried, and then coated onto the aluminum foil current collector as the first positive electrode layer; then, a membrane electrode prepared by the second positive electrode powder, solid electrolyte, and binder (i.e., polytetrafluoroethylene) is rolled onto the first positive electrode layer using a dry process as the second positive electrode layer. Figure 2 As shown, the first positive electrode uses a porous conjugated conductive polymer with high porosity (correspondingly, slightly lower compaction density). The porous conjugated conductive polymer has high conductivity, which can ensure rate performance. The second positive electrode uses a solid electrolyte with lower porosity and higher compaction density than the first positive electrode.
[0038] The following are specific examples:
[0039] Example 1
[0040] Step 1: Referring to existing technology, pyrrole monomer and hexadecyltrimethylammonium bromide are dispersed in water in an ice-water bath at 0°C. Then, a ferric chloride solution of a certain concentration is slowly added dropwise, wherein the ferric chloride concentration is more than twice the monomer concentration, and the monomer concentration is greater than 0.1 mol / L. -1 After the addition was complete, the reaction continued for 12 hours, followed by centrifugation and washing until the solution pH reached 7. Finally, it was dried in a vacuum oven at 60°C to obtain polypyrrole powder for use. The pore size distribution of the polypyrrole powder was 15–20 nm, and the specific surface area was ~35 m². 2 g -1 ;
[0041] Step 2: A slurry is prepared by mixing ternary 811 powder, polypyrrole, and polyvinylidene fluoride binder at a mass ratio of 95:3:2 (wherein, the polyvinylidene fluoride binder is pre-dissolved in NMP; other solvents can also be used). This slurry is then coated onto an aluminum foil current collector, transferred to an 80°C vacuum oven for drying, and subsequently rolled. The electrode thickness is ~170 μm, and the compaction density is ~3.3 g / cm³. -2 With a porosity of ~28%, the first positive electrode layer was obtained;
[0042] Step 3: Thoroughly mix ternary 811, polytetrafluoroethylene, LLZO, and carbon nanotubes (dry method, the same below), with a mass ratio controlled at 90:2:6:2. Then, roll the mixture in a machine to form a self-supporting film, and quickly roll it onto the first positive electrode layer. The thickness is controlled at ~30 μm, and the compaction density is ~3.7 g / cm³. -2 The porosity is ~18%.
[0043] Example 2
[0044] Step 1: Referring to existing technology, aniline monomer and hexadecyltrimethylammonium bromide are slowly added to a hydrochloric acid solution of a certain concentration in an ice-water bath at 0°C. Then, ammonium persulfate is dissolved in a certain volume of hydrochloric acid solution and slowly added dropwise to the aniline solution. The concentration of ammonium persulfate is greater than the concentration of the monomer, and the monomer concentration is greater than 0.4 mol / L. -1 The hydrochloric acid concentration is less than 5 mol / L. -1 After reacting for 3 hours, the solution was centrifuged and washed until the pH reached 7; finally, it was dried in a vacuum oven at 60°C for use; the pore size distribution of the polyaniline powder was 25–35 nm, and the specific surface area was ~42 m². 2 g -1 ;
[0045] Step 2: A slurry is prepared by mixing ternary 811 powder, polyaniline, and binder at a mass ratio of 96:2:2. This slurry is then coated onto an aluminum foil current collector, transferred to an 80°C vacuum oven for drying, and subsequently rolled. The electrode thickness is ~180 μm, and the compaction density is ~3.4 g / cm³. -2 With a porosity of ~26%, the first positive electrode layer was obtained;
[0046] Step 3, combine ternary 811, polytetrafluoroethylene, and Li7P3S 11 The mixture is thoroughly mixed with Super P at a mass ratio of 88:2:8:2, then rolled on a machine to form a self-supporting film, which is then rapidly rolled onto the first positive electrode layer. The thickness is controlled to be ~20 μm, and the compaction density is ~3.8 g / cm³. -2 The porosity is ~16%.
[0047] Example 3
[0048] Step 1: Referring to existing technology, pyrrole monomer and sodium dodecylbenzenesulfonate are dispersed in water at room temperature. Then, a certain concentration of ammonium persulfate solution is slowly added dropwise. The concentration of ammonium persulfate is greater than the concentration of the monomer. To control the polymerization rate, an inert gas is purged throughout the process. After the addition is complete, the reaction continues for 12 hours, followed by centrifugation and washing until the solution pH = 7. Finally, it is dried in a vacuum oven at 60°C for use. The polypyrrole powder has a pore size distribution of 15–25 nm and a specific surface area of ~38 m². 2 g-1 ;
[0049] Step 2: A slurry is prepared by mixing lithium iron phosphate powder, polypyrrole, and polyvinylidene fluoride binder at a mass ratio of 94:4:2. This slurry is then coated onto an aluminum foil current collector, transferred to an 80°C vacuum oven for drying, and subsequently rolled. The electrode thickness is ~170 μm, and the compaction density is ~2.3 g / cm³. -2 With a porosity of ~32%, the first positive electrode layer was obtained;
[0050] Step 3: Lithium iron phosphate, polytetrafluoroethylene, LLTO, and carbon nanotubes are thoroughly mixed in a mass ratio of 85:2:11:2. This mixture is then rolled on a machine to form a self-supporting film, which is rapidly rolled onto the first positive electrode layer. The thickness is controlled to be ~30 μm, and the compaction density is ~3.1 g / cm³. -2 The porosity is ~20%.
[0051] Example 4
[0052] Step 1: Referring to existing technology, at room temperature, aniline monomer and sodium dodecylbenzenesulfonate are slowly added to a hydrochloric acid solution of a certain concentration. Then, ammonium persulfate is dissolved in a certain volume of hydrochloric acid solution and slowly added dropwise to the aniline solution. The concentration of ammonium persulfate is greater than the concentration of the monomer, and the monomer concentration is greater than 0.4 mol / L. -1 The hydrochloric acid concentration is less than 5 mol / L. -1 After reacting for 2 hours, the solution was centrifuged and washed until the pH reached 7; finally, it was dried in a vacuum oven at 60°C for use; the pore size distribution of the polyaniline powder was 25–35 nm, and the specific surface area was ~42 m². 2 g -1 ;
[0053] Step 2: A slurry is prepared by mixing lithium iron phosphate powder, polyaniline, and a binder at a mass ratio of 96:2:2. This slurry is then coated onto an aluminum foil current collector, transferred to an 80°C vacuum oven for drying, and subsequently rolled. The electrode thickness is ~180 μm, and the compaction density is ~2.3 g / cm³. -2 With a porosity of ~30%, the first positive electrode layer was obtained;
[0054] Step 3, mix ternary 811, polytetrafluoroethylene, and Li 5.5 PS 4.5 Cl 1.5 The mixture is thoroughly mixed with graphene at a mass ratio of 86:2:10:2, then rolled on a machine to form a self-supporting film, which is then rapidly rolled onto the first positive electrode layer. The thickness is controlled to be ~20μm, and the compaction density is ~3.8g / cm³. -2 The porosity is ~16%.
[0055] Example 5
[0056] Step 1: Referring to existing technology, at room temperature, aniline monomer and sodium secondary alkyl sulfate are slowly added to a hydrochloric acid solution of a certain concentration. Then, ammonium persulfate is dissolved in a certain volume of hydrochloric acid solution and slowly added dropwise to the aniline solution. The concentration of ammonium persulfate is greater than the concentration of the monomer, and the monomer concentration is greater than 0.4 mol / L. -1 Hydrochloric acid concentration less than 5 mol / L -1 After reacting for 2 hours, the solution was centrifuged and washed until the pH reached 7; finally, it was dried in a vacuum oven at 60°C for use; the pore size distribution of the polyaniline powder was 25–35 nm, and the specific surface area was ~45 m². 2 g -1 ;
[0057] Step 2: A slurry is prepared by mixing ternary 811 powder, polyaniline, and binder at a mass ratio of 96:2:2. This slurry is then coated onto an aluminum foil current collector, transferred to an 80°C vacuum oven for drying, and subsequently rolled. The electrode thickness is ~175 μm, and the compaction density is ~3.8 g / cm³. -2 With a porosity of ~26%, the first positive electrode layer was obtained;
[0058] Step 3, add lithium-rich manganese, polytetrafluoroethylene, and Li 10 GeP2S 12 The mixture is thoroughly mixed with acetylene black at a mass ratio of 80:2:16:2, then rolled on a machine to form a self-supporting film, which is then rapidly rolled onto the first layer of positive electrode. The thickness is controlled to be ~25μm, and the compaction density is ~2.8g / cm³. -2 The porosity is ~19%.
[0059] Comparative Example 1
[0060] Ternary 811, polytetrafluoroethylene, LLZO, and super P were thoroughly mixed in a mass ratio of 84:2:12:2. The mixture was then rolled on a machine to form a self-supporting film with a thickness of approximately 200 μm and a compaction density of approximately 4.0 g / cm³. -2 The porosity is ~20%.
[0061] Comparative Example 2
[0062] Lithium iron phosphate, polytetrafluoroethylene, Li 5.5 PS 4.5 Cl 1.5 The mixture is thoroughly mixed with carbon nanotubes at a mass ratio of 84:2:12:2, and then rolled on a machine to form a self-supporting film with a thickness of ~200 μm and a compaction density of ~2.9 g / cm³. -2 The porosity is ~30%.
[0063] Comparative Example 3
[0064] Lithium-rich manganese, polytetrafluoroethylene, Li 10 GeP2S 12 The mixture is thoroughly mixed with carbon nanotubes at a mass ratio of 88:2:8:2, and then rolled on a machine to form a self-supporting film with a thickness of ~200μm and a compaction density of ~2.6g / cm³. -2 The porosity is ~32%.
[0065] The basic parameters of each embodiment are summarized in Table 1.
[0066] Table 1
[0067]
[0068] Electrolytes were added dropwise to the composite electrodes prepared in each embodiment and comparative example. The added electrolytes were commercially available high-voltage resistant electrolytes, with the lithium salt being LiPF6 at a concentration of 1M. These electrodes were then used as positive electrodes to construct semi-solid-state lithium-ion batteries in the order of positive electrode-solid electrolyte-negative electrode (the negative electrode materials and solid electrolytes used in each battery are shown in Table 2). The electrochemical performance of these batteries was tested at 30°C and standard atmospheric pressure, and the results are shown in Table 2.
[0069] Table 2
[0070]
[0071]
[0072] All tests were conducted at 30°C and standard atmospheric pressure. Table 2 shows that when the cathode material is ternary 811, the capacity retention rates at 0.2C, 100 cycles, and 1C, 500 cycles obtained based on this invention are superior to Comparative Example 1. When the cathode material is lithium iron phosphate, the capacity retention rates at 0.2C, 100 cycles, and 1C, 500 cycles obtained based on this invention in Example 3 are superior to Comparative Example 2 in terms of first-cycle capacity, capacity retention rates at 0.2C, 100 cycles, and 1C, 500 cycles. When the first layer of the cathode material is lithium iron phosphate and the second layer is ternary 811, the capacity retention rate at 0.2C, 100 cycles, and 1C, 500 cycles obtained based on this invention is further improved compared to Example 3, but the capacity retention rates at 0.2C, 100 cycles, and 1C, 500 cycles are slightly worse than in Example 3. This is mainly due to the excellent stability of lithium iron phosphate itself. When the first layer of the cathode material is ternary 811 and the second layer is lithium-rich manganese, the first-cycle capacity of Example 5 obtained based on the present invention is further improved, but the capacity retention rate at 0.2C, 100 cycles and at 1C, 500 cycles is slightly worse than that of Examples 1 and 2.
[0073] Compared to the control sample, the batteries prepared in each embodiment exhibited excellent high-rate cycle stability at 0.1C (e.g., at 1C). This is mainly attributed to the systematic optimization of the cathode structure, which significantly improved the overall ionic conductivity of the battery, resulting in a marked improvement in battery performance at high rates. Furthermore, due to the high theoretical specific capacity of lithium-rich manganese-based materials, using them as cathode materials can also achieve high initial capacity. However, their cycle stability is significantly worse than that of the embodiments, indicating that in addition to high-quality materials, further design of the electrode structure is needed to achieve optimal battery performance.
[0074] The above embodiments are merely examples. For instance, the current collector can be any material other than aluminum foil; and for another example, the positive electrode material powder in the first and second layers can be any other positive electrode material powder, which can be the same or different.
[0075] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for preparing a composite electrode for a semi-solid-state battery, wherein the composite electrode for the semi-solid-state battery comprises, from bottom to top, a current collector, a first positive electrode layer, and a second positive electrode layer, wherein, The first positive electrode layer is formed by coating and rolling raw materials including a porous conjugated conductive polymer, a first positive electrode material powder and a binder; the second positive electrode layer is formed by rolling raw materials including a second positive electrode material powder, polytetrafluoroethylene, a solid electrolyte powder and a conductive agent; and the porosity of the first positive electrode layer is greater than that of the second positive electrode layer. The preparation method is characterized by the following steps: S1. Prepare a porous conjugated conductive polymer with a pore size of 15~40 nm and a specific surface area of 20~50 m². 2 g -1 ; S2. Prepare a slurry by mixing the porous conjugated conductive polymer, the first positive electrode material powder, the binder and the solvent, coat it on the current collector, and then dry and roll it to obtain the first positive electrode layer. S3. Based on dry processing, the second positive electrode material powder, polytetrafluoroethylene, solid electrolyte powder and conductive agent are fully mixed and formed into a self-supporting film by hot rolling. Then, the self-supporting film is rolled onto the first positive electrode to obtain a composite electrode for semi-solid batteries.
2. The preparation method according to claim 1, characterized in that, The porous conjugated conductive polymer is specifically at least one of polypyrrole, polyaniline, and polydioxythiophene. Step S1 specifically involves completely dissolving the monomers, surfactants, and initiators of the conductive polymer in water or ethanol, and obtaining a porous conjugated conductive polymer by centrifugal drying. Specifically, the monomer of the conductive polymer is at least one of aniline, pyrrole, and dioxothiophene; The surfactant is one of hexadecyltrimethylammonium bromide, sodium alkyl sulfonate, sodium alkyl aryl sulfonate, sodium alkyl sulfate, and sodium secondary alkyl sulfate.
3. The preparation method according to claim 2, characterized in that, The sodium alkyl sulfonate is sodium dodecyl sulfonate, the sodium alkyl aryl sulfonate is sodium dodecylbenzene sulfonate, and the sodium alkyl sulfate is sodium dodecyl sulfate.
4. The preparation method according to claim 1, characterized in that, In step S2, the porous conjugated conductive polymer accounts for 0.5% to 5.0% of the total mass of the porous conjugated conductive polymer, the first positive electrode material powder, and the binder.
5. The preparation method according to claim 1, characterized in that, The thickness of the first positive electrode layer is 100~300 μm, and the thickness of the second positive electrode layer is 20~80 μm; The porosity of the first positive electrode layer is 25-35%, and the porosity of the second positive electrode layer is 10-20%.
6. The preparation method according to claim 1, characterized in that, The compaction density of the first positive electrode layer is 2.3~4.3 g / cm³. -2 The compaction density of the second positive electrode layer is 3.05~4.5 g cm⁻¹. -2 Furthermore, the compaction density of the second positive electrode layer is greater than that of the first positive electrode layer.
7. The preparation method according to claim 1, characterized in that, The porous conjugated conductive polymer is specifically at least one of polypyrrole, polyaniline, and polydioxythiophene. The first cathode material powder and the second cathode material powder are independently selected from lithium iron phosphate, ternary materials, and lithium-rich manganese-based materials.
8. The preparation method according to claim 1, characterized in that, The solid electrolyte powder is specifically made of perovskite-type LLTO, garnet-structured LLZO, or glass-ceramic Li7P3S. 11 tetragonal Li 10 GeP2S 12 tetragonal Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Lithium-silver-germanium ore type 5.5 PS 4.5 Cl 1.5 Lithium-silver-germanium ore type 6.6 Si 0.6 Sb 0.4 At least one of S5I.
9. The preparation method according to claim 1, characterized in that, In the second positive electrode layer, the solid electrolyte powder accounts for 5% to 25% of the total mass of the second positive electrode material powder, polytetrafluoroethylene, solid electrolyte powder, and conductive agent. The conductive agent is specifically at least one of carbon nanofibers (CNF), carbon nanotubes (CNT), graphene, activated carbon, acetylene black, Ketjen black, and super P.