Cylindrical battery with thermal safety battery cell

Abstract

The invention belongs to the technical field of cylindrical lithium ion secondary batteries, and relates to a cylindrical battery with a thermal safety cell, a preparation method of the cylindrical battery comprises the following steps: step 1, material type selection: a material A is a nickel-cobalt-manganese ternary positive electrode material (LiNixCoyMn1-x-yO2), a filling material B is a nickel-cobalt-manganese single-crystal material, and a coating material C is lithium iron phosphate or a lithium iron manganese phosphate material; 2, compounding and coating the materials, namely coating the material A and the material C as well as the material B and the material C in advance to obtain a material D and a material E respectively; further mixing the pre-mixed material D and the pre-mixed material E to obtain a final material F; step 3, battery cell trial production: matching the final material F with a battery cell raw material to prepare a positive plate, and preparing a lithium ion battery; and finally, the thermal stability of the battery cell is tested, and the battery cell can bear a 150 DEG C hot box without firing and explosion. The cylindrical battery prepared by the preparation method disclosed by the invention has high energy and high power density, and the thermal safety performance is obviously superior to that of an existing battery cell through optimization of a positive electrode material and matching of selected materials such as a diaphragm.

Description

Technical Field

[0001] The invention belongs to the technical field of cylindrical lithium-ion secondary batteries, and in particular relates to a cylindrical battery with a thermally safe battery core. Background Art

[0002] As global energy policies shift toward renewable energy, lithium batteries have attracted much attention as important energy storage and power devices. As the demand for energy density increases, the nickel content of positive electrode materials also increases, which places higher demands on the thermal stability of high-nickel materials.

[0003] At present, the national standard clearly stipulates that the battery cell must remain in a 130°C hot box test for 30 minutes without catching fire or exploding. However, when the nickel content accounts for more than 90% of the positive electrode material, there is a risk of failure in the battery cell test; because high-nickel materials have poor stability at high temperatures, they are prone to phase and structural changes, releasing oxygen and generating large amounts of heat, triggering a series of side reactions and increasing the risk of thermal runaway, which in turn leads to frequent safety accidents in application scenarios, seriously restricting the large-scale application of lithium batteries. Summary of the invention

[0004] In order to solve the problem that the above-mentioned high-nickel material has poor stability at high temperatures and increased risk of thermal runaway, the present invention provides a cylindrical battery with a thermally safe battery cell.

[0005] The technical solution adopted by the present invention is: A cylindrical battery with a thermally safe battery cell, the preparation method of which comprises the following steps: Step 1: Material type selection: Material A: Select nickel-cobalt-manganese ternary positive electrode material (LiNixCoyMn1-x-yO2), where the X ratio is greater than 0.9, and the particle size D50 of the material is 9~15 microns, such as Figure 1 As shown; Material B: Select nickel-cobalt-manganese single crystal material, the ratio of each element is equivalent to that of material A, or the nickel content is slightly higher than that of material A. The particle size D50 of this material is 3~5 microns. Figure 2 As shown; Material C: Select lithium iron phosphate or lithium iron manganese phosphate material, the particle size range is 50~200nm, such as Figure 3 As shown; Step 2: Material compounding and coating: Material A and material C are pre-coated to obtain material D, and material B and material C are pre-coated to obtain material E; the pre-mixed material D and material E are further mixed to obtain the final material F, such as Figure 4 As shown; Step 3: Cell trial production: The final material F is combined with the raw materials of the battery cell to make the positive electrode sheet, which is assembled into a cylindrical battery cell with the corresponding negative electrode sheet, isolation membrane, etc., and the electrolyte is injected. The lithium-ion battery is obtained through the formation and aging processes; finally, the thermal stability of the battery cell is tested at different temperatures.

[0006] Preferably, in step 2, the pre-coating ratio of material A and material C is 2% to 5%, and the pre-coating ratio of material B and material C is 2% to 5%.

[0007] Preferably, in step 2, the mixing ratio of material D to material E is 7:3 or 8:2.

[0008] The cylindrical battery with a thermally safe cell obtained through the above steps can withstand a 150°C hot box without catching fire or exploding after the thermal stability performance test of the cell.

[0009] The beneficial effects of the present invention are: 1. The cylindrical battery produced by the present invention takes into account both high energy and high power density. By optimizing the positive electrode material and selecting materials such as the diaphragm, the optimal solution shows that the battery cell does not catch fire or explode in a 150°C hot box test, and its thermal safety performance is significantly better than that of existing battery cells.

[0010] 2. The optimization of the positive electrode material of the present invention lies in that the selected material A is a nickel-cobalt-manganese ternary positive electrode material (LiNixCoyMn1-x-yO2), which can ensure the energy density of the battery cell; the selected material B is a nickel-cobalt-manganese single crystal material, which mainly serves to fill the pores of the material and increase the compaction density of the material; the selected material C of the present invention is lithium iron phosphate or lithium iron manganese phosphate material, which has good thermal stability as a coating material, a small particle size, a large specific surface area, and can be well attached to the surface of the material; material A and material C are premixed to obtain material D, and material B and material C are premixed to obtain material E. This premixing method avoids large-scale agglomeration of single particles, thereby ensuring a better coating effect; material D and material E are further mixed to obtain the final material F. Material F takes into account both high energy and high power density. Without affecting the high energy density of the battery cell, it can significantly improve the thermal stability performance of the battery cell and improve the thermal safety performance of the battery cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is an electron microscope image of the specific morphology of material A in the present invention; Figure 2 This is an electron microscope image of the specific morphology of material B in the present invention; Figure 3 This is an electron microscope image of the specific morphology of material C in the present invention; Figure 4 This is an electron microscope image of the specific morphology of material F in the present invention. DETAILED DESCRIPTION

[0012] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0013] A cylindrical battery with a thermally safe battery cell, the preparation method of which comprises the following steps: Step 1: Material type selection: ① Material A: Nickel-cobalt-manganese ternary positive electrode material (LiNixCoyMn1-x-yO2) is selected. To ensure the energy density of the battery cell, the X ratio is greater than 0.9. The particle size D50 of the material is 9~15 microns. The specific morphology is as follows: Figure 1 As shown, it is defined as material A in the present invention.

[0014] ② Material B: Select nickel-cobalt-manganese single crystal material, the ratio of each element is equivalent to that of material A, or the nickel content is slightly higher than that of material A. The particle size D50 of this material is 3~5 microns. Its main function is to fill the pores of the material and increase the compaction density of the material. The specific morphology is as follows: Figure 2 As shown, it is defined as material B in the present invention.

[0015] ③Material C: The selected coating material is lithium iron phosphate or lithium iron manganese phosphate. This material has good thermal stability, small particle size, large specific surface area, and can be well attached to the surface of the material. The particle size range is 50~200nm. The specific morphology is as follows: Figure 3 As shown, it is defined as material C in the present invention.

[0016] Step 2: Material compounding and coating: ① Pre-coat material A and material C, and define the pre-mixed product as material D. Meanwhile, pre-coat material B and material C, and define the pre-mixed product as material E. This pre-mixing method avoids large-scale agglomeration of single particles, thereby ensuring a better coating effect. The coating ratio can be adjusted according to design requirements, and the preferred coating ratio is 2%~5%. This will significantly improve the safety performance without affecting compaction and capacity.

[0017] ② The pre-mixed material D and material E are further mixed to obtain the final material F, whose morphology is as follows Figure 4 As shown; the mixing ratio of material D and material E can be adapted according to the energy density. The relevant principle is that the higher the proportion of E material, the better the thermal stability. The preferred ratio D:E is 7:3 or 8:2 to ensure the optimal energy density and safety characteristics.

[0018] Step 3: Cell trial production: The above-mentioned final material F is selected, matched with materials such as SP, PVDF, and organic solvent N-methylpyrrolidone, dispersed according to the existing technology, coated on aluminum foil, and finally made into a positive electrode sheet, wherein the binder ratio of all samples is set to 1~2%, and the sum of the proportions of conductive carbon black and positive electrode materials is 98~99%. It is assembled into a cylindrical battery cell with the corresponding negative electrode sheet, isolation membrane, etc., injected with electrolyte, and a lithium-ion battery is obtained through formation and aging processes, that is, a cylindrical battery with a thermally safe battery cell is obtained. Finally, the thermal stability performance of the battery cell at different temperatures is tested.

[0019] In order to test the thermal stability of the battery cell at different temperatures, the following test is conducted to compare the comparative example with the embodiment to highlight the thermal safety performance and thermal stability performance of the battery cell of the present invention.

[0020] Comparative Example 1 Material A and material B are compounded into a new material. The compounding ratio can be determined according to the required energy density and thermal stability. This time, a compounding ratio of 8:2 is used to make the positive electrode sheet, which is assembled into a cylindrical battery cell with the corresponding negative electrode sheet and isolation membrane. The electrolyte is injected and the lithium-ion battery is obtained through the formation and aging process. The thermal stability of the battery cell is tested at different temperatures. The base film of the isolation membrane is the traditional PE+alumina coating.

[0021] Comparative Example 2 Material A and material B are compounded into a new material. The compounding ratio can be determined according to the required energy density and thermal stability. This time, a compounding ratio of 8:2 is used to make the positive electrode sheet, which is assembled into a cylindrical battery cell with the corresponding negative electrode sheet, isolation membrane, etc., and the electrolyte is injected. The lithium-ion battery is obtained through the formation and aging process. The thermal stability of the battery cell is tested at different temperatures. Furthermore, the base film of the isolation membrane is traditional PE+aramid, and the aramid is meta-aramid with a coating thickness of 2-4μm, which further improves the safety performance of the battery cell.

[0022] Example 3 The material F is combined with the raw materials of the battery cell to make a positive electrode sheet, which is assembled with the corresponding negative electrode sheet, isolation membrane, etc. into a cylindrical battery cell, injected with electrolyte, and obtained through formation and aging processes to obtain a lithium-ion battery. The thermal stability of the battery cell is tested at different temperatures. The base film of the isolation membrane is a traditional PE+alumina coating.

[0023] Example 4 The material F is combined with the raw materials of the battery cell to make a positive electrode sheet, which is assembled into a cylindrical battery cell with the corresponding negative electrode sheet, isolation membrane, etc., and the electrolyte is injected. The lithium-ion battery is obtained through the formation and aging process. The thermal stability of the battery cell is tested at different temperatures. Furthermore, the base film of the isolation membrane is traditional PE+aramid, the aramid is meta-aramid, and the coating thickness is 2-4μm, which further improves the safety performance of the battery cell.

[0024] In the above tests, except for the differences between the main materials of the positive electrode and the different solutions of the separator, other auxiliary materials and processes are consistent. The test data obtained are shown in the following table: According to the comparison of the test data in the above table, it can be seen that: under the premise of not affecting the high energy density of the battery cell, the thermal stability of the battery cell made of material F is significantly improved, and the optimal solution can withstand a 150°C hot box without catching fire or exploding.

Claims

1. A cylindrical battery with a thermally safe cell, characterized in that: The preparation method thereof comprises the following steps: Step 1: Material type selection: Material A: Select nickel-cobalt-manganese ternary positive electrode material (LiNixCoyMn1-x-yO2), where the X ratio is greater than 0.9 and the particle size D50 of the material is 9~15 microns; Material B: Select nickel-cobalt-manganese single crystal material, the ratio of each element is equivalent to that of material A, or the nickel content is slightly higher than that of material A, and the particle size D50 of this material is 3~5 microns; Material C: Select lithium iron phosphate or lithium iron manganese phosphate material, with particles ranging from 50 to 200 nm; Step 2: Material compounding and coating: Material A and material C are pre-coated to obtain material D, and material B and material C are pre-coated to obtain material E; the pre-mixed material D and material E are further mixed to obtain the final material F; Step 3: Cell trial production: The final material F is combined with the raw materials of the battery cell to make the positive electrode sheet, which is assembled into a cylindrical battery cell with the corresponding negative electrode sheet, isolation membrane, etc., and the electrolyte is injected. The lithium-ion battery is obtained through the formation and aging processes; finally, the thermal stability of the battery cell is tested at different temperatures.

2. A cylindrical battery with a thermally safe cell according to claim 1, characterized in that: In step 2, the pre-coating ratio of material A and material C is 2%~5%, and the pre-coating ratio of material B and material C is 2%~5%.

3. A cylindrical battery with a thermally safe cell according to claim 1, characterized in that: In step 2, the mixing ratio of material D to material E is 7:3 or 8:

2.

4. A cylindrical battery with a thermally safe cell according to claim 1, characterized in that: After the thermal stability test of the battery cell, it can withstand a 150℃ hot box without catching fire or exploding.

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