Porous carbon fluoride battery pole piece and preparation and application thereof

Abstract

The invention discloses a porous carbon fluoride battery pole piece and preparation and application thereof, and a preparation method comprises the following steps: dispersing a carbon fluoride positive electrode material, a conductive agent, a binder and a foaming agent in a solvent to obtain slurry; preparing the slurry into an electrode plate; and heating and foaming the electrode plate to obtain the porous carbon fluoride battery pole plate. According to the invention, the foaming agent is added in the pulping process of the carbon fluoride pole piece and is matched with the thermal insulation foaming process after the pole piece is formed, so that a pore structure with proper pore size and uniform distribution is successfully constructed. The structure can effectively control the volume expansion rate of the carbon fluoride material in the discharge process of the battery to be below 5%, and the technical defect of overlarge volume expansion of carbon fluoride in the traditional process is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium primary batteries, and in particular to a porous carbon fluoride battery pole piece and its preparation and application. Background Art

[0002] Lithium / carbon fluoride (CF) batteries, currently one of the lithium battery systems with the highest theoretical capacity and specific energy, have shown broad application prospects in military applications such as underwater weapons, unmanned underwater vehicles (UUVs), and deep space exploration due to their excellent storage life, high safety, wide operating temperature range, and high specific energy by mass. These batteries have gradually achieved a certain scale of practical application. However, the poor conductivity of CF cathode materials leads to significant polarization during discharge, limiting rate performance and accompanied by significant heat release, which affects stable operation under high-power conditions. Furthermore, unlike the lithium ion insertion-extraction reaction mechanism in lithium-ion secondary batteries, the electrochemical reaction in CF batteries is a typical conversion reaction mechanism. During discharge, the layered structure of CF gradually transforms into an amorphous structure, generating products such as carbon and lithium fluoride. This reaction is accompanied by a significant volume change, with expansion rates reaching 20%-40%. This mechanical stress on the internal structure of the battery affects its overall stability and cycling performance.

[0003] While extensive research has focused on improving the discharge rate performance of carbon fluoride cathode materials and reducing polarization and heat generation through material modification and electrolyte formulation optimization, with some even achieving high-rate discharge capabilities exceeding 20C, the issue of volume expansion during discharge remains unresolved. This volume expansion issue severely restricts the design and integration of lithium / carbon fluoride batteries in practical applications, limiting the effective utilization of their high specific energy advantage. Further technological breakthroughs and systematic research are urgently needed.

[0004] Therefore, it is necessary to provide a technical solution to the volume expansion of carbon fluoride batteries. Summary of the Invention

[0005] In view of this, the present application provides a porous carbon fluoride battery electrode and its preparation and application, which are used to solve the problem of volume expansion of carbon fluoride batteries.

[0006] In order to achieve the above technical objectives, this application adopts the following technical solutions: In a first aspect, the present application provides a method for preparing a porous fluorinated carbon battery electrode, comprising the following steps: S1. The carbon fluoride cathode material, the conductive agent, the binder, and the foaming agent are dispersed in a solvent to obtain a slurry; S2. preparing the slurry into an electrode sheet; S3. The electrode sheet is heated and foamed to obtain a porous carbon fluoride battery electrode sheet.

[0007] Preferably, the foaming agent includes one or more of potassium bicarbonate, ammonium oxalate, and acetic acid.

[0008] Preferably, the mass of the foaming agent is 0.5-2% of the mass of the solid in the slurry.

[0009] Preferably, the temperature for heating and foaming is 120-180°C.

[0010] Preferably, the heating and foaming time is 2-6 hours.

[0011] Preferably, the process of preparing the slurry into an electrode sheet is: subjecting the slurry to electrode coating, roller pressing, and drying treatments in sequence.

[0012] Preferably, the conductive agent includes SP; the solvent includes NMP; and the binder includes PVDF.

[0013] Preferably, before the step of preparing the slurry, the method further comprises the step of mixing the conductive agent and the foaming agent and performing ball milling.

[0014] In a second aspect, the present application provides a porous fluorinated carbon battery electrode.

[0015] In a third aspect, the present application provides an application of a porous fluorinated carbon battery electrode in a primary battery. The beneficial effects of this application are as follows: By adding a foaming agent during the slurrying process of the carbon fluoride electrode and combining it with a heat-insulating foaming process after the electrode is formed, this application successfully constructs a pore structure with an appropriate pore size and uniform distribution. This structure can effectively control the volume expansion rate of the carbon fluoride material during battery discharge to below 5%, significantly improving the technical defect of excessive volume expansion of carbon fluoride in traditional processes. This optimized pore structure design not only improves the stability of the electrode structure, but more importantly, provides a reliable structural guarantee for the overall grouping design of the battery pack, which is conducive to the efficient integration and performance optimization of the battery system. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is an SEM image of the porous fluorinated carbon battery electrode of this application. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0018] The present application provides a method for preparing a porous fluorinated carbon battery electrode, comprising the following steps: S1. The carbon fluoride cathode material, the conductive agent, the binder, and the foaming agent are dispersed in a solvent to obtain a slurry; S2. preparing the slurry into an electrode sheet; S3. The electrode sheet is heated and foamed to obtain a porous carbon fluoride battery electrode sheet.

[0019] This application successfully constructs a pore structure with an appropriately sized and evenly distributed pore size by adding a foaming agent during the slurrying process of the carbon fluoride electrode, combined with a heat-insulating foaming process after the electrode is formed. This structure effectively controls the volume expansion rate of the carbon fluoride material during battery discharge to below 5%, significantly improving the technical defect of excessive volume expansion of carbon fluoride in traditional processes. This optimized pore structure design not only improves the stability of the electrode structure, but more importantly, provides a reliable structural guarantee for the overall grouping design of the battery pack, which is conducive to the efficient integration and performance optimization of the battery system.

[0020] In some embodiments, the foaming agent includes one or more of potassium bicarbonate, ammonium oxalate, and acetic acid.

[0021] In this embodiment, the main products of the foaming process of the foaming agent are gas or a small amount of residual ions that have no effect on electrical properties.

[0022] In some embodiments, the mass of the foaming agent is 0.5-2% of the mass of the solids in the slurry.

[0023] In this embodiment, a specific amount of foaming agent can be used to create pores of appropriate diameter in the electrode sheet, with a total pore volume capable of withstanding expansion during battery discharge. This maintains the electrode sheet compaction density within an appropriate range to ensure electrical performance. The solid mass in the slurry is the total amount of material in the slurry excluding the solvent.

[0024] In some embodiments, the temperature for heating and foaming is 120-180°C.

[0025] In this embodiment, the foaming temperature is maintained within a certain range, the lower limit of the temperature can also ensure complete foaming, and the highest foaming temperature will not damage the adhesive in the electrode.

[0026] In some embodiments, the heating and foaming time is 2-6 hours.

[0027] In this embodiment, too short a time may result in incomplete foaming.

[0028] In some embodiments, the process of preparing the slurry into an electrode sheet is as follows: the slurry is sequentially subjected to electrode coating, roll pressing, and drying.

[0029] In this embodiment, the specific process of preparing the electrode sheet is as follows: the active material CFx, the conductive agent, and the binder are dry-mixed, NMP is added to homogenize the mixture, and the slurry is coated. After drying at 120 degrees Celsius, the electrode sheet is roller-pressed to control the surface density of the electrode sheet to 22±0.2 mg / cm 2 .

[0030] In some embodiments, the conductive agent includes SP; the solvent includes NMP; and the binder includes PVDF.

[0031] In some embodiments, before the slurry preparation step, the method further comprises the step of mixing the conductive agent and the foaming agent and performing ball milling.

[0032] The present application provides a porous fluorinated carbon battery pole piece. The pore size distribution of the pole piece product of the present application is between 1μm and 3μm. The pore size is mainly controlled by the type of foaming agent, foaming process and slurry rolling process.

[0033] The present application provides an application of a porous fluorinated carbon battery electrode in a primary battery. The present invention is further described below through specific examples.

[0034] Example 1 A method for preparing a porous fluorinated carbon battery electrode comprises the following steps: S1. 16g of conductive agent SP and 4g of potassium bicarbonate were placed in a ball mill, 100ml of anhydrous ethanol was added, the ball mill speed was set to 650 rpm, ball milled for 4 hours, and then taken out and placed in a 50 ° C oven to dry; then the dried mixture of conductive agent and foaming agent potassium bicarbonate was mixed with 288g of dried carbon fluoride cathode material and 16g of binder PVDF, and 595g of NMP solvent was added and stirred thoroughly in a stirring tank to obtain a slurry; S2. The slurry is coated and rolled to obtain an electrode sheet; S3. Place the electrode sheet in an oven set at 130°C and keep it warm for 2 hours to complete foaming and pore formation to obtain a porous fluorinated carbon battery electrode sheet.

[0035] Example 2 A method for preparing a porous fluorinated carbon battery electrode comprises the following steps: S1. 16g of conductive agent SP and 5g of ammonium oxalate were placed in a ball mill, 150ml of anhydrous ethanol was added, the ball mill speed was set to 650 rpm, ball milled for 4 hours, and then taken out and placed in a 50 ° C oven to dry; then the dried mixture of conductive agent and foaming agent potassium bicarbonate was mixed with 288g of dried carbon fluoride cathode material and 16g of binder PVDF, and 595g of NMP solvent was added and stirred thoroughly in a stirring tank to obtain a slurry; S2. The slurry is coated and rolled to obtain an electrode sheet; S3. Place the electrode sheet in an oven set at 120°C and keep it warm for 4 hours to complete foaming and pore formation to obtain a porous fluorinated carbon battery electrode sheet.

[0036] Examples 3-5 A method for preparing a porous fluorinated carbon battery electrode is the same as that of Example 1 except that the heating temperatures in step S3 are 110° C., 180° C., and 200° C., respectively.

[0037] Examples 6-8 A method for preparing a porous fluorinated carbon battery electrode is the same as Example 1 except that the amounts of potassium bicarbonate used are 1g and 50g respectively.

[0038] Examples 9-10 A method for preparing a porous fluorinated carbon battery electrode is the same as Example 1 except that potassium bicarbonate is replaced by ammonium oxalate and acetic acid in sequence.

[0039] Comparative Example 1 A method for preparing a carbon fluoride battery electrode is the same as Example 1 except that no foaming agent is added.

[0040] Comparative Example 2 A method for preparing a fluorinated carbon battery electrode is the same as that of Example 1 except that no heating treatment is performed in step S3.

[0041] Testing and Evaluation The SEM images of the carbon fluoride battery pole pieces obtained in test examples 1, 9 and 10 are as follows: Figure 1 As shown, Figure 1 (a) is the test result of Example 1, Figure 1 (b) is the test result of Example 9, Figure 1 (c) is the test result of Example 10.

[0042] The porosity (compacted density / true density), pore size, and uniformity of different carbon fluoride battery pole pieces were calculated, and the expansion rate of different carbon fluoride battery pole pieces during discharge was tested. The test steps are as follows: the thickness of the carbon fluoride battery before discharge is measured and the volume is calculated accordingly; then, the battery is discharged at a certain rate to a cutoff voltage of 1.5V, at which point the battery thickness is measured, the battery volume is calculated, and the volume expansion rate after discharge is obtained. The results are shown in Table 1.

[0043] Table 1 Test results

[0044] This application successfully constructs a pore structure with an appropriate and uniform pore size by adding a foaming agent during the slurry preparation process of the carbon fluoride electrode and combining it with a heat-insulating foaming process after the electrode is formed. This structure reserves space in the electrode, effectively controlling the volume expansion rate of the carbon fluoride material during battery discharge to below 5%, significantly improving the technical defect of excessive volume expansion of carbon fluoride in traditional processes. This optimized pore structure design not only improves the stability of the electrode structure, but more importantly, provides a reliable structural guarantee for the overall group design of the battery pack, which is conducive to the efficient integration and performance optimization of the battery system.

[0045] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for preparing a porous fluorinated carbon battery electrode, characterized in that: The following steps are involved: Dispersing the carbon fluoride positive electrode material, the conductive agent, the binder, and the foaming agent in a solvent to obtain a slurry; preparing the slurry into an electrode sheet; The electrode sheet is heated and foamed to obtain the porous carbon fluoride battery electrode sheet.

2. The method for preparing a porous fluorinated carbon battery electrode according to claim 1, characterized in that: The foaming agent includes one or more of potassium bicarbonate, ammonium oxalate and acetic acid.

3. The method for preparing a porous fluorinated carbon battery electrode according to claim 1, characterized in that: The mass of the foaming agent is 0.5-2% of the mass of the solid in the slurry.

4. The method for preparing a porous fluorinated carbon battery electrode according to claim 1, characterized in that: The heating and foaming temperature is 120-180°C.

5. The method for preparing a porous fluorinated carbon battery electrode according to claim 1, characterized in that: The heating and foaming time is 2-6 hours.

6. The method for preparing a porous fluorinated carbon battery electrode according to claim 1, characterized in that: Before the slurry preparation step, the method further includes the step of mixing the conductive agent and the foaming agent and performing ball milling.

7. A porous fluorinated carbon battery electrode obtained by the preparation method according to any one of claims 1 to 6.

8. Use of the porous fluorinated carbon battery electrode according to claim 7 in a primary battery.

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