A fluorinated carbon thick electrode and its preparation method and primary battery

Abstract

This invention provides a fluorinated carbon thick electrode, its preparation method, and a primary battery. The fluorinated carbon thick electrode is obtained by optimizing the slurry formulation and performing multiple coating processes. This method is simple and feasible, requires minimal equipment, and the resulting thick electrode is pressure-resistant and not prone to cracking. The lithium fluorinated carbon battery composed of this electrode and lithium metal exhibits extremely high areal capacity, with material utilization rates exceeding 94%. Electrodes of arbitrary thickness can be obtained through multiple coating processes, and the fabrication method is simple. The battery made by matching the resulting fluorinated carbon thick electrode with an alkali metal anode has the advantages of high areal capacity and high volumetric capacity.

Description

Technical Field

[0001] This invention belongs to the field of primary battery technology, specifically relating to a fluorinated carbon thick electrode, its preparation method, and a primary battery. Background Technology

[0002] Fluorinated carbon / lithium batteries are high-energy-density primary batteries with a wide operating temperature range, low self-discharge, and long storage life, making them widely used in various civilian and military devices. However, due to the limited reserves of lithium resources on Earth, much research has focused on the development of sodium and potassium-ion batteries. In recent years, however, extensive research into new battery systems has revealed that fluorinated carbon can undergo electrochemical reactions with sodium and potassium ions, indicating that fluorinated carbon materials can be matched with metallic sodium and potassium to create novel primary batteries.

[0003] With the widespread application and popularization of electronic devices, the market demand for high-energy-density primary batteries is becoming increasingly urgent. Traditional methods of preparing thin-film electrodes or other powder-based electrodes are no longer sufficient to meet these needs. Therefore, there is an urgent need to develop a new electrode fabrication technology to obtain thick fluorinated carbon electrodes. Furthermore, although significant progress has been made in theoretical research on fluorinated carbon / sodium and fluorinated carbon / potassium batteries, their practical application still requires a rationally designed fluorinated carbon electrode that is compatible with the corresponding alkali metal.

[0004] Patent document CN112201770A discloses a method for preparing a fluorocarbon electrode, the method comprising: 1) coating an electrode slurry onto a current collector and drying it to obtain an electrode film; 2) repeating the operation of coating the electrode slurry onto the electrode film obtained in the previous operation and drying it at least once to obtain the electrode sheet, thereby increasing the active material loading on the current collector per unit area and improving the energy density of the electrode sheet.

[0005] It is evident that a common method for improving energy density is to achieve high areal capacity by increasing electrode thickness. Thicker electrodes mean greater utilization of the battery's internal space, resulting in higher energy density and reduced costs. However, in the fabrication of thick electrodes, increasing thickness increases their susceptibility to cracking and detachment, especially for electrodes prepared using traditional wet coating processes. This is the reason for the limited areal capacity of wet-coated electrodes. Furthermore, increased electrode thickness leads to deterioration in kinetic properties, preventing the material from fully reacting and reducing the utilization rate of active materials.

[0006] Therefore, a new electrode fabrication process is needed to develop high-performance fluorinated carbon thick electrodes to meet the requirements of alkali metal primary batteries for increased energy density. Summary of the Invention

[0007] To address the aforementioned problems, this invention aims to provide a method for preparing and applying a fluorinated carbon thick electrode. This invention obtains a fluorinated carbon thick electrode by optimizing the slurry formulation and performing multiple coating processes. This method is simple and feasible, requires minimal equipment, and the resulting thick electrode is pressure-resistant and not prone to cracking. The lithium fluorinated carbon battery composed of this electrode and lithium metal exhibits an extremely high areal specific capacity, with material utilization rates all exceeding 94%.

[0008] To achieve the above objectives, the present invention provides a method for preparing a fluorinated carbon thick electrode, the method comprising the following steps:

[0009] (1) Mix the fluorinated carbon active material, binder, conductive agent 1 and conductive agent 2 in a certain proportion, add solvent and stir to form electrode slurry;

[0010] (2) Apply the slurry described in step (1) to one or both sides of the mesh metal current collector;

[0011] (3) After coating, the electrode is dried at a constant temperature until it is semi-solid to obtain an electrode sheet. Then, the electrode slurry is coated on the electrode sheet obtained in the previous operation and dried at a constant temperature until the electrode sheet is semi-solid. The above operation is repeated. After the last coating is completed and dried at a constant temperature until it is semi-solid, it is transferred to an oven for vacuum drying to obtain a fluorinated carbon thick electrode. The electrode sheet is coated at least four times.

[0012] Furthermore, during the coating process, the coating thickness increases in a stepwise manner. By increasing the coating thickness in a stepwise manner during the coating process, not only can the problem of the electrode sheet cracking and falling off as the electrode thickness increases be avoided, but this process can also increase the kinetic characteristics of the electrode sheet, allowing the materials in the electrode to react fully, improving the utilization rate of active materials, and improving the performance of the battery.

[0013] Furthermore, the fluorinated carbon active material in step (1) includes one or more of fluorinated graphite, fluorinated carbon nanotubes, fluorinated graphene, fluorinated carbon fibers, fluorinated carbon nanodiscs, and fluorinated coke.

[0014] Furthermore, the adhesive is characterized in that it is polyvinylidene fluoride (PVDF) with a molecular weight of 1000 to 10000.

[0015] Furthermore, the conductive agent 1 in step (1) comprises one or more of multi-walled carbon nanotubes (MWCNTs), single-walled carbon nanotubes (SWCNTs), vapor-grown carbon fibers (VGCFs), and carbon nanofibers (CNFs); the conductive agent 2 in step (1) comprises one or more of superconducting carbon black, acetylene black, Ketjen black, and conductive graphite spheres. The conductive agent 1 has a one-dimensional structure, and the conductive agent 2 has a zero-dimensional structure. The one-dimensional conductive agent 1 can form a network structure in the active material layer, while the zero-dimensional conductive agent 2 fills the gaps in the network structure composed of one-dimensional materials, so that the entire active material can be surrounded by the conductive agent, thereby improving the conductivity of the electrode and further improving the performance of the electrode.

[0016] Furthermore, in step (1), the mass ratio of fluorinated carbon, adhesive, conductive agent 1, and conductive agent 2 is (80-96)%:(1-14)%:(1-14)%:(1-14)%; and the solid content of the slurry in step (1) is 25%-50%.

[0017] Furthermore, the mesh metal current collector in step (2) is one of stainless steel mesh, nickel mesh, titanium mesh, copper mesh, aluminum mesh, tungsten mesh, molybdenum mesh, zirconium mesh or platinum mesh.

[0018] Furthermore, in step (3), the constant temperature drying temperature range is 25-50℃; the vacuum drying temperature is 50-80℃.

[0019] Furthermore, the coating method includes one or more of spraying, scraping, and spin coating.

[0020] The present invention also provides a primary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte; characterized in that the positive electrode is a fluorinated carbon thick electrode prepared by the above method, and the negative electrode is one of lithium, sodium, and potassium metals.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. An improvement on the traditional coating method, this method is simple to prepare and allows for adjustments to the electrode thickness (200µm~3000µm) as needed. The slurry composition and ratio can also be optimized according to the desired discharge characteristics. Furthermore, single-sided or double-sided coating can be selected based on the battery configuration, offering good flexibility. Because the mesh current collector acts as a framework, the resulting electrode exhibits excellent mechanical properties. Additionally, the electrode is heated to a semi-solid state during coating, without being completely dried, and multiple coating processes are performed on this semi-solid state. This prevents the final electrode from cracking and ensures that it is not damaged by vertical pressure, unlike traditional thick powder-coated electrodes.

[0023] 2. During the coating process, the coating thickness increases in a stepwise manner. By increasing the coating thickness in a stepwise manner during the coating process, not only can the problem of the electrode sheet cracking and falling off as the electrode thickness increases be avoided, but this process can also increase the kinetic characteristics of the electrode sheet, so that the materials in the electrode can fully react, improve the utilization rate of active materials, and improve the performance of the battery.

[0024] 3. By combining a one-dimensional conductive agent (1) with a zero-dimensional conductive agent (2), a one-dimensional conductive agent (1) can form a network structure in the active material layer, while the zero-dimensional conductive agent (2) fills the gaps in the network structure composed of one-dimensional materials to construct a three-dimensional conductive network. This allows the active material in the electrode to be completely surrounded by the conductive agent, improving the conductivity of the electrode and further enhancing its performance. The resulting thick electrode has extremely high areal specific capacity and volumetric specific capacity. If it is used to make a lithium fluoride carbon battery, it can achieve more than twice the volumetric specific capacity of commercial batteries. Attached Figure Description

[0025] Figure 1 The following is an external view of the thick electrode provided in Examples 1-5.

[0026] Figure 2 The discharge curve is shown in Example 1.

[0027] Figure 3 The discharge curve is shown in Example 2.

[0028] Figure 4 The discharge curve is shown in Example 3.

[0029] Figure 5 The discharge curve is shown in Example 4.

[0030] Figure 6 The discharge curve is shown in Example 5.

[0031] Figure 7 The discharge curve is for Comparative Example 1.

[0032] Figure 8 The discharge curve is for Comparative Example 2.

[0033] Figure 9 The discharge curve is for Comparative Example 3.

[0034] Figure 10 This is a diagram showing the appearance of the electrode during the coating and drying process of Comparative Example 3. Detailed Implementation

[0035] To make the technical solution and advantages of the present invention clearer, the present invention and its beneficial effects will be described in further detail below with reference to specific embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0036] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0037] Example 1

[0038] Fluorinated graphite, polyvinylidene fluoride (Mw=5130), multi-walled carbon nanotubes, and Super P were mixed and ground evenly in a ratio of 90:6:2:2. N-methylpyrrolidone solvent was added, and the mixture was stirred to form a slurry with a solid content of 37%. The slurry was coated onto a flat 100-mesh stainless steel mesh using a doctor blade and dried at 35°C until semi-solid. The coating process was repeated four times, with doctor blade spacing of 1.5 mm, 1.5 mm, 2 mm, and 2 mm respectively. After the final drying to semi-solid state, the slurry was transferred to an oven and dried at 60°C for 12 hours. It was then punched into a 1 cm diameter disc electrode and placed in a vacuum oven for later use. The disc electrode was assembled with lithium metal to form a coin cell for testing. A PP separator was used, and the electrolyte was 1 M LiBF4 dissolved in a mixture of ethylene glycol dimethyl ether and propylene carbonate.

[0039] Example 2

[0040] Fluorinated graphite, polyvinylidene fluoride (Mw=5130), multi-walled carbon nanotubes, and Super P were mixed and ground evenly in a ratio of 90:6:2:2. N-methylpyrrolidone solvent was added, and the mixture was stirred to form a slurry with a solid content of 40%. The slurry was coated onto a flat 80-mesh aluminum mesh using a doctor blade and dried at 35°C until semi-solid. The coating process was repeated four times, with doctor blade spacing of 1.5 mm, 1.5 mm, 2 mm, and 2 mm respectively. After the final drying to semi-solid state, the slurry was transferred to an oven and dried at 60°C for 12 hours. It was then punched into a 1 cm diameter disc electrode and stored in a vacuum oven for later use. The disc electrode was assembled with lithium metal to form a coin cell for testing. A PP separator was used, and the electrolyte was 1 M LiBF4 dissolved in a mixture of ethylene glycol dimethyl ether and propylene carbonate.

[0041] Example 3

[0042] Fluorinated graphene, polyvinylidene fluoride (Mw=5130), single-walled carbon nanotubes, and Super P were mixed and ground evenly in a ratio of 92:4:2:2. N-methylpyrrolidone solvent was added, and the mixture was stirred to form a slurry with a solid content of 40%. The slurry was coated onto a flat 80-mesh aluminum mesh using a doctor blade and dried at 35°C until semi-solid. The coating process was repeated four times, with doctor blade spacing of 1.5 mm, 1.5 mm, 2 mm, and 2 mm respectively. After the final drying to semi-solid state, the slurry was transferred to an oven and dried at 60°C for 12 hours. It was then punched into a 1 cm diameter disc electrode and stored in a vacuum oven for later use. The disc electrode was assembled with lithium metal to form a coin cell for testing. A PP separator was used, and the electrolyte was 1 M LiBF4 dissolved in a mixture of ethylene glycol dimethyl ether and propylene carbonate.

[0043] Example 4

[0044] Fluorinated graphite, polyvinylidene fluoride (Mw=5130), multi-walled carbon nanotubes, and Super P were mixed and ground evenly in a ratio of 90:6:2:2. N-methylpyrrolidone solvent was added and stirred to form a slurry with a solid content of 40%. The slurry was coated onto a flat aluminum mesh using a doctor blade and dried at a constant temperature of 35°C until it was semi-solid. The coating and drying process on one side with active material was repeated four times until a moist solid surface was formed. The other side was then coated and dried four times. The doctor blade spacing used for coating was 1.5 mm, 1.5 mm, 2 mm, and 2 mm, respectively. After the final drying to semi-solid state, the electrode was transferred to an oven and dried at 60°C for 12 hours to obtain a double-sided coated thick electrode. This electrode was cut into 0.8 × 0.8 cm tab-coated sheets and placed in a vacuum oven for later use. The above-mentioned disc electrode was assembled with lithium metal into a coin cell for testing. The separator used was a PP separator, and the electrolyte was 1 M LiBF4 dissolved in a mixed solution of ethylene glycol dimethyl ether and propylene carbonate.

[0045] Example 5

[0046] The difference between this embodiment and Embodiment 2 is that in this embodiment, the finished thick electrode is assembled with metallic sodium to form a button cell, the separator used is a GF / A glass fiber separator, and the electrolyte is 1 M NaPF6 dissolved in a mixed solution of ethylene glycol dimethyl ether and propylene carbonate.

[0047] Comparative Example 1

[0048] The difference between this comparative example and Example 2 is that the electrode material is composed of fluorinated graphite, polyvinylidene fluoride (Mw=5130), and multi-walled carbon nanotubes in a ratio of 90:6:4, while the other parameters are the same as in Example 2.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Example 2 is that the electrode material is composed of fluorinated graphite, polyvinylidene fluoride (Mw=5130), and Super P in a ratio of 90:6:4, while the other parameters are the same as in Example 2.

[0051] Comparative Example 3

[0052] The difference between this comparative example and Example 2 is that the electrode was thoroughly dried after each coating of slurry before subsequent coating.

[0053] Implementation effect

[0054] Figure 1 (a, b) Front and back images of the thick electrode described in Example 1; (c, d) Front and back images of the thick electrodes described in Examples 2 and 5; (e, f) Front and back images of the thick electrode described in Example 3; (g) Front and back images of the thick electrode described in Example 4. The thickness of the thick electrodes prepared in Examples 1-4 is 1400–1600 µm, and the appearance of the thick electrodes described in Examples 1-6 is as follows. Figure 1 As shown, the thick electrode in the embodiment possesses good mechanical properties and is not easily cracked or damaged; while... Figure 10 As shown, Comparative Example 3 did not fully utilize the method described in this invention, resulting in electrode cracking during the drying process. As can be seen from Example 2 and Comparative Examples 1-2, using only one-dimensional materials or zero-dimensional carbon materials cannot construct a three-dimensional network conductive structure, ultimately leading to deterioration of the battery's electrochemical performance. The discharge data corresponding to the examples are shown in Table 1 and... Figure 2-6 As shown, the fluorinated carbon thick electrode prepared by the method provided by this invention exhibits extremely high areal capacity, with a single-sided coating capacity of 100 mAh / cm². 2 On the left and right sides, double-sided coating can double the yield to 200 Ah / cm. 2 The above results show that the utilization rate of active materials is generally above 94%, which has good economic benefits. Secondly, the fluorinated carbon thick electrode is well compatible with the alkali metal negative electrode (comparative examples 2 and 5), and can be used to assemble various alkali metal primary batteries.

[0055] Table 1. Discharge data of fluorinated carbon thick electrode batteries among different examples

[0056]

[0057] The above are merely exemplary embodiments of this disclosure and should not be construed as limiting the scope of this disclosure. Any equivalent changes and modifications made in accordance with the teachings of this disclosure shall still fall within the scope of this disclosure. Those skilled in the art will readily conceive of other embodiments of this disclosure upon considering the specification and the disclosure of practical truths. This application is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not described in this disclosure.

Claims

1. A method for preparing a fluorinated carbon thick electrode, characterized in that, The preparation method includes the following steps: (1) Fluorocarbon active material, binder, conductive agent 1, and conductive agent 2 are mixed evenly in a certain proportion, and solvent is added and stirred to form an electrode slurry; the conductive agent 1 includes one or more of multi-walled carbon nanotubes (MWCNT), single-walled carbon nanotubes (SWCNT), vapor-grown carbon fibers (VGCF), and carbon nanofibers (CNF); the conductive agent 2 in step (1) includes one or more of superconducting carbon black, acetylene black, Ketjen black, and conductive graphite spheres; the mass ratio of fluorocarbon, binder, conductive agent 1, and conductive agent 2 is (80-96)%:(1-14)%:(1-14)%:(1-14)%; (2) The slurry described in step (1) is coated on one or both sides of the mesh metal current collector; during the coating process, the coating thickness increases in a stepwise manner; (3) After coating, the electrode is dried at a constant temperature until it is semi-solid to obtain an electrode sheet. Then, the electrode slurry is coated on the electrode sheet obtained in the previous operation and dried at a constant temperature until the electrode sheet is semi-solid. The above operation is repeated. After the last coating is completed and dried at a constant temperature until it is semi-solid, it is transferred to an oven for vacuum drying to obtain a fluorinated carbon thick electrode. The electrode sheet is coated at least four times.

2. The method for preparing a fluorinated carbon thick electrode according to claim 1, characterized in that, The fluorinated carbon active material in step (1) includes one or more of the following: fluorinated graphite, fluorinated carbon nanotubes, fluorinated graphene, fluorinated carbon fibers, fluorinated carbon nanodiscs, and fluorinated coke.

3. The method for preparing a fluorinated carbon thick electrode according to claim 1, characterized in that, The adhesive is polyvinylidene fluoride (PVDF) with a molecular weight of 1000 to 10000.

4. The method for preparing a fluorinated carbon thick electrode according to claim 1, characterized in that, The slurry solids content in step (1) is 25% to 50%.

5. The method for preparing a fluorinated carbon thick electrode according to claim 1, characterized in that, The mesh metal current collector in step (2) is one of stainless steel mesh, nickel mesh, titanium mesh, copper mesh, aluminum mesh, tungsten mesh, molybdenum mesh, zirconium mesh or platinum mesh.

6. The method for preparing a fluorinated carbon thick electrode according to claim 1, characterized in that, In step (3), the constant temperature drying temperature range is 25-50℃; the vacuum drying temperature is 50-80℃.

7. The method for preparing a fluorinated carbon thick electrode according to claim 1, characterized in that, The coating method includes one or more of spraying, scraping, and spin coating.

8. A primary battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte; characterized in that, The positive electrode is a fluorinated carbon thick electrode prepared by the method described in any one of claims 1-7, and the negative electrode is one of lithium, sodium, and potassium.

Images