A method for manufacturing a positive electrode sheet by multi-layer coating

Abstract

The application discloses a kind of multilayer coating preparation positive plate method, it is related to battery material preparation technical field, specifically is sequentially first slurry, second slurry, third slurry is coated on positive current collector, each slurry coating is dried or all slurry coating is dried, and it is prepared by rolling;Wherein, active substance in the first slurry is ternary material;Active substance in the second slurry is lithium manganate;Active substance in third slurry is lithium iron phosphate.The application sequentially coats slurry containing active substance with weak to strong safety performance on current collector, prepares positive plate, solves the problem that, in traditional composite slurry coating method, due to some active substance has greater water absorption, so that the positive plate is prone to brittle fracture when drying, thereby affecting battery performance and production efficiency.

Description

Technical Field

[0001] This invention relates to the field of battery material preparation technology, specifically a method for preparing a positive electrode sheet through multilayer coating. Background Technology

[0002] Lithium-ion batteries are widely used in smartphones, laptops, Bluetooth devices, and wearable devices due to their advantages such as high energy density, no memory effect, and long lifespan. However, with the large-scale application of lithium-ion batteries, battery safety issues are becoming increasingly prominent.

[0003] The cathode material of existing lithium-ion batteries is usually made by mixing various active materials together, coating them onto the current collector, and then pressing them with a drying roller. However, in this case, the active materials have a high water absorption rate, which greatly reduces their safety performance. Therefore, improvements are needed. Summary of the Invention

[0004] The purpose of this invention is to at least solve one of the technical problems existing in the prior art, and to provide a method for preparing a positive electrode sheet by multilayer coating.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing a positive electrode sheet by multilayer coating involves sequentially coating a first slurry, a second slurry, and a third slurry onto a positive electrode current collector, drying each slurry after coating or drying all slurries after coating, and then rolling to obtain the electrode sheet.

[0007] The active material in the first slurry is a ternary material;

[0008] The active material in the second slurry is lithium manganese oxide;

[0009] The active material in the third slurry is lithium iron phosphate.

[0010] As a preferred embodiment of the present invention, the medium particle size of the ternary material is 2-10 μm;

[0011] The medium particle size of the lithium manganese oxide is 15-23 μm.

[0012] The medium particle size of the lithium iron phosphate is 0.5-3 μm.

[0013] As a preferred embodiment of the present invention, the compacted density of the first slurry after drying and roller pressing is 3.5-3.8 g / cm³. 3 ;

[0014] The compacted density of the second slurry after drying and roller pressing is 2.8-3.1 g / cm³. 3 ;

[0015] The compacted density of the third slurry after drying and roller pressing is 2.0-2.3 g / cm³.3 .

[0016] As a preferred embodiment of the present invention, after coating the third slurry, a fourth slurry is coated, which contains ceramic particles; after coating the fourth slurry, it is dried and then fired.

[0017] As a preferred embodiment of the present invention, the ceramic particles include at least one of alumina, boehmite, magnesium oxide, titanium oxide, zirconium oxide, silicon oxide, and yttrium oxide.

[0018] As a preferred embodiment of the present invention, the calcination temperature is 160-350℃.

[0019] As a preferred embodiment of the present invention, the drying temperature is 90-120℃ and the drying time is 1-3h.

[0020] As a preferred embodiment of the present invention, the first slurry, the second slurry, and the third slurry further include a conductive agent, a binder, and a solvent.

[0021] The beneficial effects of this invention are as follows: This invention sequentially coats a slurry containing active materials with safety performance ranging from weak to strong onto a current collector to prepare a positive electrode sheet. This solves the problem in traditional composite slurry coating methods where some active materials have a high water absorption rate, making the electrode sheet prone to brittleness during drying, thus affecting battery performance and production efficiency. In addition, the final layer of ceramic coating can suppress the reaction between the active material of the battery positive electrode and the electrolyte membrane during charging and discharging, preventing internal short circuits and further improving the safety performance of the battery. Detailed Implementation

[0022] A method for preparing a positive electrode sheet by multilayer coating involves sequentially coating a first slurry, a second slurry, and a third slurry onto a positive electrode current collector, drying each slurry after coating or drying all slurries after coating, and then rolling to obtain the electrode sheet.

[0023] The active material in the first slurry is a ternary material, which accounts for 80-85 wt% of the mass of the first slurry.

[0024] The active material in the second slurry is lithium manganese oxide, which accounts for 75-85 wt% of the second slurry by mass.

[0025] The active material in the third slurry is lithium iron phosphate, which accounts for 80-90 wt% of the mass of the third slurry.

[0026] Specifically, the medium particle size of the ternary material is 2-10 μm;

[0027] The medium particle size of the lithium manganese oxide is 15-23 μm.

[0028] The medium particle size of the lithium iron phosphate is 0.5-3 μm.

[0029] Specifically, the compacted density of the first slurry after drying and roller pressing is 3.5-3.8 g / cm³. 3 ;

[0030] The compacted density of the second slurry after drying and roller pressing is 2.8-3.1 g / cm³. 3 ;

[0031] The compacted density of the third slurry after drying and roller pressing is 2.0-2.3 g / cm³. 3 .

[0032] In some embodiments, after the third slurry is coated, a fourth slurry is also coated, which contains 70-80 wt% ceramic particles; after the fourth slurry is coated, it is dried and then calcined.

[0033] Preferably, the ceramic particles include at least one of alumina, boehmite, magnesium oxide, titanium oxide, zirconium oxide, silicon oxide, and yttrium oxide.

[0034] Preferably, the calcination temperature is 160-350℃.

[0035] Furthermore, the drying temperature is 90-120℃, and the drying time is 1-3 hours.

[0036] Furthermore, the first slurry, the second slurry, and the third slurry also include a conductive agent, a binder, and a solvent. Specifically, the conductive agent is at least one of vapor-grown carbon fiber, acetylene black, conductive carbon black, graphitized carbon fiber, or carbon nanotubes.

[0037] The binder is PVDF or PTFE, and the solvent is one of NMP, DMF or DMA.

[0038] The following embodiments further illustrate the technical solution of the present invention.

[0039] Example 1

[0040] A method for preparing a positive electrode sheet by multilayer coating involves sequentially coating a first slurry, a second slurry, and a third slurry onto a positive electrode current collector (aluminum foil), vacuum drying each slurry after coating, and then rolling to obtain the electrode sheet.

[0041] The active material in the first slurry is a ternary material, which accounts for 80 wt% of the mass of the first slurry; the conductive agent and binder solution account for 15 wt% and 5 wt%, respectively.

[0042] The active material in the second slurry is lithium manganese oxide, which accounts for 75 wt% of the total mass of the second slurry; the conductive agent and binder solution account for 18 wt% and 7 wt%, respectively.

[0043] The active material in the third slurry is lithium iron phosphate, which accounts for 80 wt% of the total mass of the third slurry. The conductive agent and binder solution account for 12 wt% and 8 wt%, respectively.

[0044] The conductive agent is conductive carbon black;

[0045] The binder is PVDF, and the solvent is NMP.

[0046] The adhesive solution is specifically prepared by adding the adhesive to a solvent to form a 10wt% adhesive solution.

[0047] The medium particle size of the ternary material is 5 μm.

[0048] The medium particle size of the lithium manganese oxide is 18 μm.

[0049] The medium particle size of the lithium iron phosphate is 1 μm.

[0050] The compacted density of the first slurry after drying and roller pressing is 3.5 g / cm³. 3 ;

[0051] The compacted density of the second slurry after drying and roller pressing is 2.8 g / cm³. 3 ;

[0052] The compacted density of the third slurry after drying and roller pressing is 2.0 g / cm³. 3 .

[0053] Each layer of slurry is coated with a thickness of 100μm, and then compacted according to the compaction density of each layer of slurry.

[0054] The drying temperature is 90℃ and the drying time is 2 hours.

[0055] Example 2

[0056] A method for preparing a positive electrode sheet by multilayer coating involves sequentially coating a first slurry, a second slurry, and a third slurry onto a positive electrode current collector (aluminum foil), vacuum drying each slurry after coating, and then rolling to obtain the electrode sheet.

[0057] The active material in the first slurry is a ternary material, which accounts for 82 wt% of the mass of the first slurry; the conductive agent and binder solution account for 14 wt% and 4 wt%, respectively.

[0058] The active material in the second slurry is lithium manganese oxide, which accounts for 79 wt% of the total mass of the second slurry; the conductive agent and binder solution account for 15 wt% and 6 wt%, respectively.

[0059] The active material in the third slurry is lithium iron phosphate, which accounts for 85 wt% of the total mass of the third slurry. The conductive agent and binder solution account for 9 wt% and 6 wt%, respectively.

[0060] The conductive agent is acetylene black;

[0061] The binder is PTFE and the solvent is DMA.

[0062] The adhesive solution is specifically prepared by adding the adhesive to a solvent to form a 10wt% adhesive solution.

[0063] The medium particle size of the ternary material is 6 μm.

[0064] The medium particle size of the lithium manganese oxide is 19 μm;

[0065] The medium particle size of the lithium iron phosphate is 1.2 μm.

[0066] The compacted density of the first slurry after drying and roller pressing is 3.6 g / cm³. 3 ;

[0067] The compacted density of the second slurry after drying and roller pressing is 2.9 g / cm³. 3 ;

[0068] The compacted density of the third slurry after drying and roller pressing is 2.1 g / cm³. 3 .

[0069] Each layer of slurry is coated with a thickness of 110μm, and then compacted according to the compaction density of each layer of slurry.

[0070] The drying temperature is 100℃ and the drying time is 2 hours.

[0071] Example 3

[0072] A method for preparing a positive electrode sheet by multilayer coating involves sequentially coating a first slurry, a second slurry, and a third slurry onto a positive electrode current collector (aluminum foil), vacuum drying each slurry after coating, and then rolling to obtain the electrode sheet.

[0073] The active material in the first slurry is a ternary material, which accounts for 85 wt% of the mass of the first slurry; the conductive agent and binder solution account for 11 wt% and 4 wt%, respectively.

[0074] The active material in the second slurry is lithium manganese oxide, which accounts for 78 wt% of the total mass of the second slurry; the conductive agent and binder solution account for 15 wt% and 7 wt%, respectively.

[0075] The active material in the third slurry is lithium iron phosphate, which accounts for 81 wt% of the total mass of the third slurry. The conductive agent and binder solution account for 11 wt% and 8 wt%, respectively.

[0076] The conductive agent is vapor-grown carbon fiber;

[0077] The binder is PVDF and the solvent is DMF.

[0078] The adhesive solution is specifically prepared by adding the adhesive to a solvent to form a 7wt% adhesive solution.

[0079] The medium particle size of the ternary material is 8 μm.

[0080] The medium particle size of the lithium manganese oxide is 20 μm;

[0081] The medium particle size of the lithium iron phosphate is 2 μm.

[0082] The compacted density of the first slurry after drying and roller pressing is 3.8 g / cm³. 3 ;

[0083] The compacted density of the second slurry after drying and roller pressing is 3.1 g / cm³. 3 ;

[0084] The compacted density of the third slurry after drying and roller pressing is 2.3 g / cm³. 3 .

[0085] Each layer of slurry is coated with a thickness of 90μm, and then compacted according to the compaction density of each layer of slurry.

[0086] The drying temperature is 110℃ and the drying time is 1.5h.

[0087] Example 4

[0088] This embodiment is a modification of Embodiment 3. Specifically, after coating the third slurry, a fourth slurry is applied, containing 72 wt% ceramic particles. After coating the fourth slurry, the mixture is dried and then calcined. The calcination temperature is 350°C.

[0089] The ceramic particles include alumina.

[0090] Example 5

[0091] This embodiment is a modification based on embodiment 3. Specifically, after coating the third slurry, a fourth slurry is coated, which contains 75 wt% ceramic particles. After coating the fourth slurry, the mixture is dried and then calcined.

[0092] The ceramic particles include boehmite.

[0093] Example 6

[0094] This embodiment is a modification based on embodiment 3. Specifically, all slurry is vacuum dried after coating.

[0095] Comparative Example 1 (One-time coating)

[0096] A method for preparing a positive electrode sheet by multilayer coating involves coating a positive electrode slurry onto a positive electrode current collector (aluminum foil), drying each slurry after coating or vacuum drying all slurries after coating, and then rolling to obtain the electrode sheet.

[0097] The active materials in the positive electrode slurry are ternary materials, lithium manganese oxide, and lithium iron phosphate, accounting for 80 wt% of the positive electrode slurry by mass; the conductive agent and binder solution account for 15 wt% and 5 wt%, respectively.

[0098] The conductive agent is conductive carbon black;

[0099] The binder is PVDF, and the solvent is NMP.

[0100] The adhesive solution is specifically prepared by adding the adhesive to a solvent to form a 10wt% adhesive solution.

[0101] The medium particle size of the ternary material is 5 μm.

[0102] The medium particle size of the lithium manganese oxide is 18 μm.

[0103] The medium particle size of the lithium iron phosphate is 1.2 μm.

[0104] The compacted density of the positive electrode slurry after drying and roller pressing is 2.9 g / cm³. 3 ;

[0105] Each layer of slurry is coated with a thickness of 100μm, and then compacted according to the compaction density of each layer of slurry.

[0106] The drying temperature is 110℃ and the drying time is 1.5h.

[0107] According to the above embodiments and comparative examples, the positive electrode sheet is made into a battery negative electrode sheet according to the production line process. Then, the LCI8650 battery is made according to the process requirements. After charging and activation, the charge and discharge capacity is tested. Then, various tests are performed on the battery for comparison, including cycle test and nail penetration test. The test values ​​are shown in Table 1.

[0108] Needle prick test method:

[0109] 1. Charge the battery under test with a constant current of 1000mA to 4.2V, and then keep the voltage constant at 4.2V until the current drops to 20mA. At this point, the battery is considered to be fully charged.

[0110] 2. After removing the battery, let it sit at room temperature for 20 minutes, then test the battery voltage;

[0111] 3. Place the battery to be tested into the needle penetration test fixture, and connect a temperature probe to the center of the battery casing to detect the surface temperature of the battery;

[0112] 4. Activate the needle penetration test device and puncture the battery with a 3mm diameter needle at a speed of 40mm / s;

[0113] Observe the results of the entire acupuncture treatment.

[0114] The test results are shown in Table 1.

[0115] Table 1 Performance test values ​​of the examples and comparative examples

[0116]

[0117] As can be seen from the table above, the safety performance of the embodiments of the present invention is better than that of Comparative Example 1. The main reason may be that in the embodiments, a slurry containing active materials with varying safety performance is coated on the current collector to prepare the positive electrode sheet. This solves the problem in the traditional composite slurry coating method where some active materials have a high water absorption rate, making the electrode sheet prone to brittleness during drying, thus affecting the battery safety performance. In addition, in Examples 4 and 5, a ceramic coating is applied as the last layer, which can suppress the reaction between the active material of the battery positive electrode and the electrolyte membrane during charging and discharging, preventing internal short circuits, thereby further improving the battery safety performance.

[0118] Without causing conflict, those skilled in the art can freely combine and use the above-mentioned additional technical features.

[0119] The above description is only a preferred embodiment of the present invention. Any technical solution that achieves the purpose of the present invention by essentially the same means is within the protection scope of the present invention.

Claims

1. A method for preparing a positive electrode sheet through multilayer coating, characterized in that, The first slurry, the second slurry, and the third slurry are sequentially coated onto the positive electrode current collector. After each slurry is coated, it is dried, or after all slurries are coated, it is dried and then rolled. The active material in the first slurry is a ternary material; The active material in the second slurry is lithium manganese oxide; The active material in the third slurry is lithium iron phosphate; the medium particle size of the ternary material is 2-10 μm. The medium particle size of the lithium manganese oxide is 15-23 μm. The lithium iron phosphate has a medium particle size of 0.5-3 μm; the compacted density of the first slurry after drying and roller pressing is 3.5-3.8 g / cm³. 3 ; The compacted density of the second slurry after drying and roller pressing is 2.8-3.1 g / cm³. 3 ; The compacted density of the third slurry after drying and roller pressing is 2.0-2.3 g / cm³. 3 After the third slurry is applied, a fourth slurry containing ceramic particles is applied. After the fourth slurry is applied, it is dried and then fired.

2. The method for preparing a positive electrode sheet by multilayer coating according to claim 1, characterized in that, The ceramic particles include at least one of alumina, boehmite, magnesium oxide, titanium oxide, zirconium oxide, silicon oxide, and yttrium oxide.

3. The method for preparing a positive electrode sheet by multilayer coating according to claim 1, characterized in that, The roasting temperature is 160-350℃.

4. The method for preparing a positive electrode sheet by multilayer coating according to claim 1, characterized in that, The drying temperature is 90-120℃, and the drying time is 1-3 hours.

5. The method for preparing a positive electrode sheet by multilayer coating according to claim 1, characterized in that, The first slurry, the second slurry, and the third slurry also include conductive agents, binders, and solvents.

Images