A method for preparing a CMC-derived carbon / SWCNTs three-dimensional conductive agent for lithium / carbon monofluoride primary batteries

Abstract

This invention discloses a method for preparing a three-dimensional conductive agent material of CMC-derived carbon / SWCNTs and its application in lithium fluoride carbon primary batteries, belonging to the field of conductive agent preparation technology for battery cathode materials. The method includes: dissolving sodium carboxymethyl cellulose (CMC) in deionized water to form a dispersion, adding purified single-walled carbon nanotubes (SWCNTs) for dispersion, freeze-drying, pre-oxidizing in air, then carbonizing at high temperature in a CVD furnace, and finally washing and freeze-drying to obtain the CMC-derived carbon / SWCNTs three-dimensional conductive agent. By controlling the concentrations of SWCNTs and CMC and the carbonization temperature, a spatially uniform distribution of the three-dimensional conductive network in the conductive agent can be achieved. The three-dimensional conductive agent prepared by this invention not only significantly improves electron transport efficiency and electrolyte adsorption capacity, but also effectively controls the deposition behavior of the discharge product LiF, inhibiting its excessive crystallization growth, thereby reducing electrode expansion and cracking. When applied to lithium / fluoride carbon primary batteries, it can significantly improve rate performance and voltage plateau. This method is simple to operate, low in cost, and suitable for large-scale preparation.

Description

Technical Field

[0001] This invention belongs to the field of conductive agent preparation technology for battery cathode materials, specifically relating to the preparation of a three-dimensional conductive agent material based on CMC-derived carbon and highly dispersed SWCNTs composites and its application in battery cathode materials. In particular, by adjusting the concentrations of SWCNTs and CMC and the carbonization temperature, a three-dimensional conductive agent with a spatially uniform distribution of CMC-derived carbon / SWCNTs is prepared. Its main features are that the uniform dispersion of single-walled carbon nanotubes and the construction of a three-dimensional conductive network effectively improve the transport of lithium ions and free electrons between fluorinated carbon particles, thereby improving the rate performance and voltage plateau of lithium / carbon fluoride primary batteries. Background Technology

[0002] The rapid development of energy storage devices has become a key driving force in today's energy sector. Among them, lithium-ion batteries stand out due to their advantages such as low cost, stable voltage, and high portability. Li / CFx primary batteries have become a key research focus due to their high energy density, long storage life, and stable operating voltage. However, the poor electrode kinetics, low cathode electronic conductivity, and cathode expansion during discharge of fluorinated carbon materials limit their application in high-power scenarios.

[0003] Currently, methods to improve the rate performance of lithium / carbon fluoride batteries mainly involve the modification of fluoride materials, electrolyte modification, and the preparation of conductive agents. The modification of conductive agents primarily involves the composite use of various conductive materials, including carbon black, onion carbon, and graphene, to create a spatial conductive network, thereby improving the direct lithium-ion and electron transport efficiency of fluoride particles. While these methods effectively enhance the electrochemical performance of the battery, they cannot control the deposition behavior of the discharge product LiF. LiF, in a highly crystalline, dense, blocky form, deposits on the electrode surface. Its excellent insulating properties severely hinder the transport kinetics of Li+, causing electrode sheet cracking and expansion, thus affecting battery discharge performance.

[0004] Therefore, a conductive agent that can accelerate electron transfer rate while regulating LiF deposition behavior to prevent further growth is urgently needed to be developed in order to enable the application of lithium / carbon fluoride batteries in high-rate scenarios. Summary of the Invention

[0005] To address the above problems, the present invention aims to provide a method for preparing CMC-derived carbon / SWCNTs three-dimensional conductive agents for lithium / carbon fluoride primary batteries. The technical solution of this invention is as follows:

[0006] A method for preparing three-dimensional conductive agent materials of CMC-derived carbon / SWCNTs includes the following steps:

[0007] Step 1: Dissolve CMC in deionized water under certain temperature and conditions to prepare CMC dispersion solution;

[0008] Step 2: Add a certain amount of purified single-walled carbon nanotubes to the dispersion solution in Step 1 and disperse them, then freeze-dry them.

[0009] Step 3: The material obtained after freeze-drying in step 2 is subjected to pre-oxidation treatment in air to obtain a pre-oxidized product;

[0010] Step 4: Place the pre-oxidized product obtained in step 3 into a CVD furnace for high-temperature carbonization to obtain the carbonized product;

[0011] Step 5: Wash the carbonized product obtained in step 4, freeze-dry it, and obtain CMC-derived carbon / SWCNTs three-dimensional conductive agent.

[0012] Step 6: Prepare electrode sheets using the obtained three-dimensional conductive agent according to the traditional ratio of active material: binder: conductive agent = 8:1:1, and use them in coin cells.

[0013] Preferably, the specific temperature mentioned in step 1 is 40~50℃, the CMC concentration is 0.5%~3%, and the prepared dispersion solution is transparent;

[0014] Furthermore, in step 2, the content of single-walled carbon nanotubes is 5 mg / ml to 30 mg / ml, and dispersion is performed using a homogenizer at a speed of not less than 20,000 rpm for 30 to 120 minutes. Ultrasonic power is 100 W for 30 to 120 minutes.

[0015] Furthermore, the pre-oxidation temperature in step 3 is 280~320℃.

[0016] Furthermore, in step 4, the carbonization temperature is 600~1000℃ and the time is 1~6 hours.

[0017] Furthermore, deionized water is used for washing in step 5.

[0018] Furthermore, the adhesive used in step 6 is PVDF, the solvent is NMP, and the button cell model is CR2032.

[0019] This invention discloses a method for preparing three-dimensional conductive agent materials of CMC-derived carbon / SWCNTs, which has the advantages of simple operation and low cost, and is expected to be applied in the preparation of large-scale conductive agents.

[0020] Compared with existing technologies, this technology has the following advantages: Based on the excellent conductivity, large aspect ratio, and specific surface area of ​​single-walled carbon nanotubes, this invention prepares a three-dimensional conductive agent material of CMC-derived carbon / SWCNTs. Through the addition of SWCNTs, the adsorption capacity of the conductive agent for the electrolyte and the electron transport efficiency are significantly improved, resulting in a more stable voltage platform and a higher discharge rate in Li / CFx coin cells. Simultaneously, the effective control of LiF crystal growth significantly reduces electrode expansion and cracking. Attached Figure Description

[0021] Figure 1 SEM image of the conductive agent prepared in Embodiment 1 of the present invention.

[0022] Figure 2 TEM image of the conductive agent prepared in Example 1 of the present invention.

[0023] Figure 3 Discharge performance diagram of batteries prepared using commercial conductive agents

[0024] Figure 4 The discharge performance diagram of the battery prepared in Example 1 of this invention.

[0025] Figure 5 The discharge performance diagram of the battery prepared in Example 2 of this invention.

[0026] Figure 6 SEM comparison images of electrode sheets prepared with commercial conductive agents before and after discharge.

[0027] Figure 7 This is a comparison of SEM images of the electrode sheet before and after discharge in Example 1 of the present invention.

[0028] Figure 8 SEM comparison of cross-sections of electrode sheets prepared with commercial conductive agents before and after discharge.

[0029] Figure 9 This is a SEM comparison image of the electrode sheet before and after discharge in Example 1 of the present invention.

[0030] Figure 10 This is a schematic diagram of the sample preparation of the present invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the present invention will be further described below with reference to the accompanying drawings and embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, the reagents, methods, and equipment used in this invention are conventional reagents, methods, and equipment in this technical field. All materials and reagents used are commercially available. Example

[0032] Step 1: Dissolve 1 g of CMC in 100 ml of deionized water at 50°C using a magnetic stirrer;

[0033] Step 2: Add 5-10 mg of purified SWCNTs to the dispersion solution from Step 1, and disperse using a homogenizer for 30-60 minutes, followed by sonication for 30-60 minutes. Finally, freeze-dry the resulting dispersion solution until the deionized water has completely sublimated.

[0034] Step 3: Pre-oxidize the material obtained in Step 2 in air at a temperature of 300 degrees Celsius for 1 hour.

[0035] Step 4: Place the material obtained in Step 3 in a CVD furnace and carbonize it at 800℃ for 1-2 hours to obtain a three-dimensional conductive agent of CMC-derived carbon / SWCNTs.

[0036] Step 4: Prepare electrode sheets from the obtained composite cathode material according to the ratio of active material: binder: conductive agent = 8:1:1. The electrode sheet coating thickness is 160 μm, and it is used in CR2032 coin cells. Example

[0037] This embodiment provides a method for preparing a three-dimensional conductive agent material of CMC-derived carbon / SWCNTs, which is basically the same as that in Example 1, except that the carbonization temperature of the material in CVD is 1000 ℃.

Claims

1. A method for preparing a CMC-derived carbon / SWCNTs three-dimensional conductive agent for lithium / carbon fluoride primary batteries, characterized in that, Includes the following steps: (a) Dissolve carboxymethyl cellulose (CMC) in deionized water to obtain CMC gel solution; (b) Add single-walled carbon nanotubes (SWCNTs) to the CMC solution, disperse them, and then freeze-dry them to obtain a solid precursor of CMC-coated SWCNTs; (c) The solid precursor is subjected to pre-oxidation treatment in air atmosphere at 280~320°C to obtain a pre-oxidized product; (d) The pre-oxidized product is subjected to high-temperature carbonization under an inert atmosphere to obtain a carbonized product; (e) The carbonized product is washed with water to remove sodium salts, and then freeze-dried to obtain CMC-derived carbon / SWCNTs three-dimensional conductive agent material.

2. The preparation method according to claim 1, characterized in that, In step (a), the dissolution temperature of CMC is 40~50℃, and the mass fraction of CMC in deionized water is 0.5%~3%.

3. The preparation method according to claim 1, characterized in that, In step (b), the amount of SWCNTs added to the CMC adhesive is 5 mg / mL to 30 mg / mL.

4. The preparation method according to claim 1, characterized in that, In step (b), the dispersion treatment includes homogenization treatment and ultrasonic treatment; the rotation speed of the homogenization treatment is ≥20000 rpm, and the time is 30~120 minutes; the power of the ultrasonic treatment is 100 W, and the time is 30~120 minutes.

5. The preparation method according to claim 1, characterized in that, In step (c), the pre-oxidation treatment takes 0.5 to 3 hours.

6. The preparation method according to claim 1, characterized in that, In step (d), the high-temperature carbonization temperature is 600~1000℃ and the time is 1~6 hours.

7. The preparation method according to claim 1, characterized in that, In step (e), the water washing is performed using deionized water until the washing solution is neutral and then freeze-dried.

8. A CMC-derived carbon / SWCNTs three-dimensional conductive agent material, characterized in that, Prepared by the method according to any one of claims 1-7, wherein: SWCNTs constitute a three-dimensional conductive framework; the derived carbon formed by pre-oxidation and carbonization of CMC coats the surface of SWCNTs and / or connects adjacent SWCNTs; the sodium content in the material is less than 0.1 wt%.

9. The three-dimensional conductive agent material according to claim 8, characterized in that, Compared to control materials that have not undergone pre-oxidation or have not been washed with water, this material exhibits lower electrode cracking rate and higher rate performance in lithium / carbon fluoride primary battery electrode sheets.

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