Lithium-carbon fluoride button cell

Abstract

According to the lithium-carbon fluoride button battery, a carbon fluoride material, a conductive agent and a binding agent are used for manufacturing a positive plate, deionized water is compounded with one or more of ethyl alcohol, propyl alcohol, N-methyl pyrrolidone (NMP) and butanone, then the carbon fluoride material is successfully wetted, the problems in the carbon fluoride application process are solved, and the lithium-carbon fluoride button battery has the advantages that the lithium-carbon fluoride button battery can be applied to a lithium battery; the positive electrode forming effect is ensured; meanwhile, different binders, conductive agents and the carbon fluoride material are matched for use, so that the liquid absorption expansion rate of the positive electrode is reduced from 32% to below 10%, the polarization phenomenon in the battery is effectively reduced, the internal resistance of the battery is reduced, and finally, the high-capacity and high-voltage lithium-carbon fluoride button battery is obtained.

Description

Technical Field

[0001] This invention relates to battery processing technology, and more particularly to a lithium-carbon fluoride button battery. Background Technology

[0002] With continuous technological advancements, lithium batteries, as high-energy-density electrochemical energy storage devices, have been widely used in defense, aerospace, and civilian electronics. Among them, primary lithium batteries with metallic lithium as the negative electrode are diverse and have high specific energy. Currently, the most representative commercially available type is the lithium-manganese dioxide battery, with a mass energy density of approximately 280-350 Wh / kg and a nominal voltage of 3V. However, with the rapid development of electrical appliances, the market has placed higher demands on battery energy density.

[0003] Lithium-fluorinated carbon (CFCC) primary batteries are battery systems that use fluorinated carbon as the positive electrode and metallic lithium as the negative electrode. Their theoretical specific energy is as high as 2180 Wh / kg, and their actual energy density can reach over 500 Wh / kg. Compared to lithium-manganese dioxide batteries, they not only have higher energy density but also advantages such as stable discharge voltage, low self-discharge rate, and excellent high-temperature discharge performance. Currently, there are no lithium-fluorinated carbon (CFCC) button battery products on the market. Therefore, how to apply fluorinated carbon materials to the button battery manufacturing process and develop high-energy, long-range primary button battery products is a topic worthy of in-depth research. Summary of the Invention

[0004] The purpose of this invention is to provide a lithium-carbon fluoride button battery.

[0005] The technical solution to achieve the objective of this invention is: a lithium-carbon fluoride button battery, comprising a positive electrode, wherein the preparation process of the positive electrode comprises the following steps: 1) The fluorocarbon material, conductive agent, and binder are physically mixed to obtain a uniformly mixed dry powder; the mass percentage of each component in the mixed powder is as follows: Fluorocarbon materials 85%-92%, Conductive agent 3-10%, Adhesive 2-6%; The fluorinated carbon material is fluorinated graphite and / or fluorinated graphene; The conductive agent is one or more of the following: conductive graphite, expanded graphite, acetylene black, conductive carbon black, graphene, and carbon nanotubes. The adhesive is polytetrafluoroethylene and / or polyacrylic acid; 2) Add 10%-40% of the weight of the wetting agent to the dry powder obtained in step 1) and stir again; after stirring, dry at 120°C for 12 hours; wherein, the wetting agent is one or more of deionized water mixed with ethanol, propanol, N-methylpyrrolidone (NMP), and butanone, and the concentration of the wetting agent is above 99%; 3) Grind the dried powder from step 2) into positive electrode sheets.

[0006] Fluorocarbon materials have small particles and a wetting angle with water greater than 90 degrees, making them difficult to wet. This leads to difficulties in forming fluorocarbon electrode sheets and severe swelling after liquid absorption. Fluorocarbon is a highly hydrophobic, low surface energy material with strong surface chemical inertness and weak interaction with strongly polar molecules such as water. The inventors discovered through experiments that solvents such as ethanol, acetone, and N-methylpyrrolidone (NMP) have moderate surface tension. Although their polarity is higher than that of non-polar solvents, it is still much lower than that of water, and some solvents can pass through the dipole- The dipole interaction produces a weak interaction with the fluorinated carbon surface. When deionized water is combined with one or more of ethanol, propanol, N-methylpyrrolidone (NMP), and butanone, the wettability is better than that of water-based fluorinated carbon materials, which can be successfully wetted. This overcomes the difficulties in the application process of fluorinated carbon and ensures the positive electrode forming effect. At the same time, the carboxyl groups in polyacrylic acid form hydrogen bonds and chemical bonds with the surface of active materials, resulting in high bonding strength. Polytetrafluoroethylene relies on molecular chain entanglement to form physical bonding, which has weak bonding strength but outstanding flexibility. By using different binders and conductive agents in combination with fluorinated carbon materials, the electrode forming can be stabilized, the positive electrode liquid absorption expansion rate can be reduced from 32% to below 10%, and the internal polarization phenomenon of the battery can be effectively reduced, the internal resistance of the battery can be reduced, and finally a high-capacity, high-voltage lithium-fluorinated carbon button battery can be obtained. Detailed Implementation

[0007] The preferred embodiments of the present invention will be described in detail below. Example 1

[0008] A lithium-carbon fluoride button battery includes a positive electrode, the preparation process of which includes the following steps: 1) Fluorinated graphite, conductive agent, and binder are physically stirred and mixed to obtain a uniformly mixed dry powder; the mass percentages of each component of the mixed powder are as follows: fluorinated carbon 85%, conductive agent 10%, binder 7%; the conductive agent is conductive graphite; the binder is polytetrafluoroethylene; 2) Add 15% of the weight of the wetting agent to the dry powder obtained in step 1) and stir again; after stirring, dry at 120°C for 12 hours; wherein the wetting agent is deionized water mixed with ethanol, the weight of the deionized water is 10% of the weight of the dry powder, and the weight of the ethanol is 5% of the weight of the dry powder; 3) The dried powder is crushed into positive electrode sheets, and the positive electrode sheets are assembled with other conventional raw materials to obtain lithium-carbon fluoride button batteries.

[0009] Examples 2-12, Comparative Examples 1-2 Examples 2-12 and Comparative Examples 1-2 have the same positive electrode preparation process as Example 1, except that the raw materials used in the positive electrode are slightly different. Specific parameters are shown in Table 1.

[0010] Table 1

[0011] Table 2 shows a performance comparison of the positive electrode sheets and assembled lithium-fluorinated carbon button batteries obtained in Examples 1-12 and Comparative Examples 1-2 of the present invention. Simultaneously, commercially available lithium manganese button batteries from leading companies were purchased as Comparative Example 3 for comparison with each example. The positive electrode expansion rate was calculated using the following formula: (thickness of positive electrode sheet after liquid absorption - thickness of positive electrode sheet before liquid absorption) / thickness of positive electrode sheet before liquid absorption * 100%. Battery internal resistance: 3.0V voltage, tested with an AC 1kHz resistance tester; Discharge mode 1: At 25℃, with a constant resistance load of 1KΩ and a cutoff voltage of 2.0V, record the discharge capacity; Discharge mode 2: 10mA / 5s, 5s / min, 24h / day, cutoff voltage 2.2V, record the number of pulse discharges; The specific results are as follows: Table 2

[0012] As shown in Table 2, Comparative Example 1 used only 15% of the dry powder weight of deionized water for wetting, making it difficult to form the fluorinated carbon material electrode sheet. Furthermore, the electrode sheet swelled severely after absorbing liquid, resulting in a significant increase in internal resistance and low battery capacity. Examples 5-12, using the positive electrode sheet manufacturing process parameters of this invention, employed a dual-component wetting agent and different binders, reducing the positive electrode liquid absorption swelling rate from 32% to below 10%. This solved the problem of large volume expansion of the fluorinated carbon material affecting battery structural stability and improved battery capacity. Comparative Example 2 used a small amount of fluorinated carbon, resulting in high battery internal resistance and low discharge capacity. Examples 1-12 showed a significant increase in the number of 10mA pulse discharges compared to the comparative examples, especially Example 12, which increased the number of discharges to 15375, an improvement of over 53% compared to Comparative Examples 2 and 3. This solved the problem of increased polarization and low discharge capacity during high-rate discharge in the prior art, achieving high-power discharge performance for the battery.

[0013] The amounts of conductive agent and binder in the mixed powder of this invention are comparable to those of the corresponding components in commercially available lithium manganese button batteries. This invention uses different binders and conductive agents in combination with fluorinated carbon materials, and prepares the positive electrode through processes such as dry mixing, wet mixing, sheet forming, and final composite with a metal mesh. This effectively improves the compaction density and contact properties of the fluorinated carbon material, resulting in stable battery capacity and enhanced performance.

[0014] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent process transformations made using the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A lithium-carbon fluoride button cell, comprising a positive electrode, characterized in that: The manufacturing process of the positive electrode includes the following steps: 1) The fluorocarbon material, conductive agent, and binder are physically mixed to obtain a uniformly mixed dry powder; the mass percentage of each component in the mixed powder is as follows: Fluorocarbon materials 85%-92%, Conductive agent 3-10%, Adhesive 2-6%; The fluorinated carbon material is fluorinated graphite and / or fluorinated graphene; The conductive agent is one or more of the following: conductive graphite, expanded graphite, acetylene black, conductive carbon black, graphene, and carbon nanotubes. The adhesive is polytetrafluoroethylene and / or polyacrylic acid; 2) Add 10%-40% of the weight of the wetting agent to the dry powder obtained in step 1) and stir again; after stirring, dry at 120°C for 12 hours; wherein, the wetting agent is one or more of deionized water mixed with ethanol, propanol, N-methylpyrrolidone (NMP), and butanone. 3) Grind the dried powder into positive electrode sheets.

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