A positive electrode plate of a soft package battery cell, a preparation method thereof, and a battery
By mixing lithium transition metal oxides with lithium iron phosphate or lithium manganese iron phosphate in the positive electrode of lithium-ion batteries, the problems of complex processes, high costs and poor safety in existing technologies are solved, and high energy density and safety are improved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG CHAOWEI CHUANGYUAN INDUSTRAIAL
- Filing Date
- 2026-02-09
- Publication Date
- 2026-06-19
AI Technical Summary
Existing lithium-ion battery cathode designs are complex, costly, have poor safety, and insufficient energy density. In particular, lithium transition metal oxides have thermal stability issues, and lithium manganese iron phosphate poses a risk of declining cycle performance.
The positive electrode design employs a random mixture of lithium transition metal oxide and lithium iron phosphate or lithium manganese iron phosphate, utilizing the high thermal stability of both to block heat transfer, combined with a simple preparation process to improve safety and energy density.
It effectively blocks the thermal decomposition of lithium transition metal oxides, reduces the risk of thermal runaway, improves the specific energy and safety performance of the battery cell, and maintains a low manufacturing cost.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, and relates to a positive electrode sheet of a soft-pack battery cell, its preparation method and battery, specifically to a lithium-ion battery positive electrode material system, and a lithium-ion battery using this positive electrode material system. Background Technology
[0002] Lithium iron phosphate (LFP) has become the most widely used cathode material for lithium-ion batteries in the current new energy industry due to its abundant raw materials, low price, and excellent safety.
[0003] Compared with lithium iron phosphate materials, lithium transition metal oxides, typically represented by lithium cobalt oxide and ternary materials, have higher specific capacity and specific energy, but their safety is far inferior to that of lithium iron phosphate materials.
[0004] CN121097026A describes a positive electrode sheet and its preparation method. The positive electrode sheet includes: a positive current collector, a first positive electrode coating of a first active material (lithium iron phosphate), a second positive electrode coating of a second active material (lithium nickel cobalt manganese oxide), and a third positive electrode coating on a solid electrolyte layer (titanium niobate). This design has three problems: First, the numerous coatings lead to a complex and cumbersome preparation process, low yield, and high manufacturing cost; second, the addition of the expensive solid electrolyte layer not only increases material costs but also reduces the energy density of the battery cell; third, the use of pure lithium nickel cobalt manganese oxide as the active material in the second positive electrode coating still poses a high safety risk.
[0005] CN120637383A describes a positive electrode sheet for a large pouch cell and its preparation method. The positive electrode sheet includes an aluminum foil current collector, a first positive electrode coating composed of a lithium manganese iron phosphate layer, and a second positive electrode coating composed of a lithium transition metal oxide positive electrode material, lithium manganese iron phosphate, and an ion transport enhancement material. This design has two problems: first, the multiple coatings lead to a complex and cumbersome preparation process, low yield, and high manufacturing cost; third, while the introduction of lithium manganese iron phosphate optimizes the safety risks of the cell, it also introduces the risk of decreased cycle performance due to manganese leaching.
[0006] The industry urgently needs lithium-ion battery products with high safety performance and energy density, low cost, and cycle performance that meets usage requirements. Summary of the Invention
[0007] To address industry needs, this invention provides a positive electrode sheet for a pouch cell, its preparation method, and the battery itself. The active materials in the positive electrode sheet provided by this invention include lithium iron phosphate (LFP) and lithium transition metal oxides, and may also contain lithium manganese iron phosphate (LMFP), with the components randomly mixed. The solution of this invention can significantly optimize the safety performance of lithium transition metal oxides while increasing the energy density of lithium iron phosphate cells. During internal short circuits, the high thermal stability of the dispersed lithium iron phosphate and lithium manganese iron phosphate materials effectively blocks the heat transfer of thermally decomposed lithium transition metal oxide materials. Furthermore, the preparation process is simple and does not increase manufacturing costs.
[0008] The present invention adopts the following technical solution: In a first aspect, the present invention provides a positive electrode sheet for a pouch cell, the positive electrode sheet comprising a positive electrode material layer covering the surface of a current collector; The active material in the cathode material layer is a random mixture of two components, lithium transition metal oxide and lithium iron phosphate (LFP), or a random mixture of three components, lithium transition metal oxide, lithium iron phosphate (LFP) and lithium manganese iron phosphate (LMFP).
[0009] Preferably, the lithium transition metal oxide includes any one or a combination of at least two of the following: lithium nickel cobalt manganese oxide (NCM), lithium cobalt oxide, lithium manganese oxide, or lithium nickel oxide.
[0010] Preferably, the chemical formula of the lithium nickel cobalt manganese oxide ternary material (NCM) is LiNi. x Co y Mn z O2, x+y+z=1. More preferably, x=0.30~0.95, y=0.05~0.95; even further, x can preferably be 0.30~0.75, which can effectively improve the electrochemical performance of the cathode material while synergistically improving the battery safety performance with lithium iron phosphate (or lithium manganese iron phosphate).
[0011] Preferably, the lithium manganese iron phosphate has an orthorhombic olivine-type crystal structure and the chemical formula LiMn. x Fe 1-x PO4, where 0.55≤x≤0.85.
[0012] Preferably, the mass percentage of the three components of lithium transition metal oxide, lithium iron phosphate (LFP), and lithium manganese iron phosphate (LMFP) in the active material is (5%–70%):(10%–70%):(0–30%).
[0013] Preferably, the current collector is a carbon-coated aluminum foil with a double-sided carbon coating; More preferably, the aluminum foil in the current collector carbon-coated aluminum foil has a thickness of 10-16 μm, and the carbon coating layer on the surface of the aluminum foil has a thickness of 0.5-2.0 μm.
[0014] Preferably, the positive electrode material layer further includes a conductive agent and a binder. The conductive agent includes any one or at least a combination of two of conductive graphite, conductive carbon black, acetylene black, carbon nanotubes, or graphene. The binder includes any one or a combination of two of polyvinylidene fluoride and polytetrafluoroethylene.
[0015] Preferably, the mass ratio of active material, conductive agent and binder in the positive electrode material layer is (80%~98%):(1%~10%):(1%~10%).
[0016] Preferably, the thickness of the positive electrode material layer after roll forming is 90–190 μm.
[0017] In a second aspect, the present invention provides a method for preparing the positive electrode sheet described in the first aspect, the method comprising: forming a slurry containing the active material; The slurry is coated onto the current collector, and then rolled and die-cut to form a positive electrode sheet.
[0018] Preferably, the preparation method includes: S1: Add the adhesive to N-methylpyrrolidone (NMP) according to the calculated amount, and stir to form a glue solution; S2: Add the conductive agent to the adhesive solution according to the calculated amount, and stir to form a conductive agent adhesive solution; S3: Add the active materials to the conductive agent solution in calculated amounts according to their D50 values, from smallest to largest, and stir to form a slurry. Adding the active materials to the conductive agent solution in ascending order of D50 promotes uniform dispersion of the active materials in the slurry. Specifically, first add the active material with the smallest D50 to the conductive agent solution in calculated amounts and stir for 1 hour; then add the second smallest active material in calculated amounts and stir for 1 hour; and so on, until the active material with the largest D50 is added and stirred for 1 hour. Then, continue stirring the resulting slurry at high speed for 2 hours, adjust the viscosity with NMP, and form the final slurry. S4: The slurry is coated onto the aluminum foil current collector according to the areal density, and then formed into a positive electrode sheet after rolling and die cutting.
[0019] Thirdly, the present invention provides a pouch cell, the pouch cell comprising the positive electrode sheet described in the first aspect.
[0020] Typically, a pouch cell includes a positive electrode, a negative electrode, a separator, and an electrolyte. The separator is positioned between the positive and negative electrodes to prevent short circuits and to provide lithium electrolyte. + The electrolyte acts as a conductor of active ions.
[0021] In this invention, the negative electrode sheet includes a copper foil and a negative electrode material layer.
[0022] In this invention, the negative electrode active material in the negative electrode material layer includes at least one of artificial graphite, natural graphite, hard carbon, and silicon carbide. The negative electrode material layer may also optionally include a negative electrode conductive agent, a negative electrode binder, and the negative electrode active material. The negative electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The negative electrode binder includes at least one of styrene-butadiene rubber, waterborne acrylic resin, polyacrylamide, polyvinyl alcohol, and carboxymethyl chitosan.
[0023] In the soft-pack battery cell of the present invention, the separator used can be any known porous structure separator with good chemical and mechanical stability, and may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. It can be a single layer or a multilayer composite.
[0024] In this invention, the outer packaging of the soft-pack battery cell is an aluminum-plastic film with a thickness of 60–170 μm.
[0025] Fourthly, the present invention provides a power battery, the power battery comprising the soft-pack cells described in the third aspect.
[0026] Compared with the prior art, the present invention has the following beneficial effects: (1) In the positive electrode sheet of the pouch cell provided by the present invention, the active material is a random mixture of two components, lithium transition metal oxide and lithium iron phosphate (LFP), or a random mixture of three components, lithium transition metal oxide, lithium iron phosphate (LFP) and lithium manganese iron phosphate (LMFP). Since both lithium iron phosphate and lithium manganese iron phosphate materials have high thermal stability, the lithium transition metal oxide material in the positive electrode sheet undergoes thermal decomposition during the internal short circuit. The lithium iron phosphate and lithium manganese iron phosphate uniformly dispersed in the positive electrode sheet can effectively block heat transfer, slow down the further diffusion of thermal decomposition, thereby delaying the local temperature rise caused by puncture, inhibiting energy release and blocking the thermal runaway chain reaction, and reducing the risk of thermal runaway of the pouch cell; the solution of the present invention can optimize the safety of the pouch cell.
[0027] (2) In the positive electrode of the pouch cell provided by the present invention, the active material is a two-component lithium transition metal oxide and lithium iron phosphate (LFP), or a three-component lithium transition metal oxide, lithium iron phosphate (LFP), and lithium manganese iron phosphate (LMFP). Compared with lithium iron phosphate cells, the addition of lithium transition metal oxide, which has higher specific capacity and specific energy, improves the specific energy of the pouch cell. Detailed Implementation
[0028] The present invention will be further described in detail below with reference to specific embodiments and comparative examples. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.
[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.
[0030] The present invention will be further described below with reference to specific embodiments.
[0031] Example 1 Lithium transition metal oxide materials are selected from ternary materials, specifically LiNi. 0.6 Co 0.2 Mn 0.2 O2(NCM622), lithium manganese iron phosphate material uses LiMn 0.7 Fe 0.3 PO4 (MF73).
[0032] The ratio of the three active materials is: NCM622: Lithium iron phosphate (LFP): Lithium manganese iron phosphate (MF73) = 50%:30%:20%; The ratio of active material: conductive agent: binder in the positive electrode material layer is 93%:4.0%:3.0%. Manufacturing 20Ah soft-pack battery cells.
[0033] Production steps: S1: Pour the adhesive into N-methylpyrrolidone (NMP) according to the calculated amount, and stir for 12 hours to form a glue solution; Preferably, the adhesive is Solvay 5130 PVDF.
[0034] S2: Add the conductive agent to the adhesive solution according to the calculated amount, and stir at high speed for 2 hours to form a conductive agent adhesive solution; Preferably, the conductive agent contains carbon black and carbon nanotubes.
[0035] S3: According to the calculated amount of D50, add the active material to the conductive agent solution in order of increasing D50, and stir at high speed for 5 hours to form a slurry; Preferably, MF73 is added first, and the mixture is stirred at high speed for 1 hour; then lithium iron phosphate is added, and the mixture is stirred at high speed for 1 hour; then NCM622 is added, and the mixture is stirred at high speed for 3 hours. S4: Measure the viscosity of the slurry, and add an appropriate amount of NMP according to the test results to adjust the viscosity to the set value.
[0036] S5: Apply the slurry onto the carbon-coated aluminum foil current collector according to the set areal density; preferably, the areal density is 14.5–21.5 mg / cm³. 2 .
[0037] S6: After rolling and die cutting, a positive electrode sheet is formed; S7: According to the design requirements, the negative electrode slurry with graphite as the active material is taken from the production line and formed into a negative electrode sheet after coating, rolling and die cutting. S8: The positive electrode, negative electrode and separator are stacked to form a core; Preferably, the diaphragm is a wet-coated diaphragm with a thickness of 12+4μm. S9: After assembly, baking, liquid injection, formation, and capacity testing, cell 1 is formed; Preferably, the electrolyte is a liquid electrolyte with a LiPF6 content of 1 mol / L.
[0038] Example 2 The ratio of the two active materials is: NCM622: Lithium iron phosphate (LFP) = 50%:50%; the rest of the information is the same as in Example 1, forming cell 2.
[0039] Example 3 The ratio of the three active materials is: NCM622: Lithium iron phosphate LFP: MF73 = 35%: 55%: 10%; the rest of the information is the same as in Example 1, forming cell 3.
[0040] Example 4 The ratio of the two active materials is: NCM622: Lithium iron phosphate (LFP) = 35%: 65%; the rest of the information is the same as in Example 1, forming cell 4.
[0041] Example 5 Lithium transition metal oxide materials are selected from ternary materials, specifically LiNi. 0.8 Co 0.1 Mn 0.1 O(NCM811); the ratio of the three active materials is: NCM822: lithium iron phosphate LFP: MF73 = 50%:30%:20%; the rest of the information is the same as in Example 1, forming cell 5.
[0042] Example 6 Lithium transition metal oxide materials are selected from ternary materials, specifically LiNi. 0.8 Co 0.1 Mn 0.1 O(NCM811); the ratio of the two active materials is: NCM811: Lithium iron phosphate (LFP) = 50%: 50%; the rest of the information is the same as in Example 1, forming cell 6.
[0043] Example 7 Lithium transition metal oxide materials are selected from ternary materials, specifically LiNi. 0.8 Co 0.1 Mn 0.1 O(NCM811); the ratio of the three active materials is: NCM811: Lithium iron phosphate LFP: MF73 = 35%: 55%: 10%; the rest of the information is the same as in Example 1, forming cell 7.
[0044] Example 8 Lithium transition metal oxide materials are selected from ternary materials, specifically LiNi. 0.8 Co 0.1 Mn 0.1 O(NCM811); the ratio of the two active materials is: NCM811: Lithium iron phosphate (LFP) = 35%: 65%; the rest of the information is the same as in Example 1, forming cell 8.
[0045] Comparative Example 1: The active material is pure ternary material NCM622; the rest of the information is the same as in Example 1, forming cell 9.
[0046] Comparative Example 2: The active material is pure ternary material NCM811; the rest of the information is the same as in Example 1, forming cell 10.
[0047] Comparative Example 3: The active material is pure lithium iron phosphate; the rest of the information is the same as in Example 1, forming cell 11.
[0048] Mass specific energy, room temperature cycling, and needle puncture tests were performed on the examples and comparative examples.
[0049] Mass energy density test: Charge and discharge at 0.5C at room temperature; Room temperature cycling test: At room temperature, it is fully charged at 0.5C constant current and 4.2V constant voltage, then left to stand for 20 minutes, discharged at 1C to 2.5V, and then left to stand for another 20 minutes before starting the next cycle; Needle penetration test: Fill the chamber at room temperature with constant current and constant voltage of 0.5C and 4.2V, and perform a needle penetration test using a steel needle with a diameter of φ6 within 12 hours.
[0050] The test results are shown in Table 1.
[0051] Table 1 Test Results The test results show that, compared with Comparative Examples 1 and 2, the addition of lithium iron phosphate greatly improves the safety of the battery cell. The needle penetration test result changed from violent fire to no smoke or smoke without fire.
[0052] The test results show that, compared with Comparative Examples 1 and 2, the addition of lithium iron phosphate improved the cycle performance of the battery cell.
[0053] The test results show that, compared with Comparative Example 3, the addition of transition metal oxides improved the energy density of the battery cell, increasing it by at least 13 Wh / Kg from the original 182 Wh / Kg.
[0054] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A positive electrode sheet for a pouch cell, characterized in that, The positive electrode includes a positive electrode material layer covering the surface of the current collector; The active material in the cathode material layer is a random mixture of lithium transition metal oxide and lithium iron phosphate (LFP).
2. A positive electrode sheet for a pouch cell, characterized in that, The positive electrode includes a positive electrode material layer covering the surface of the current collector; The active material in the cathode material layer is a random mixture of three components: lithium transition metal oxide, lithium iron phosphate (LFP), and lithium manganese iron phosphate (LMFP).
3. The positive electrode of the pouch cell according to claim 1 or 2, characterized in that, The lithium transition metal oxide includes any one or a combination of at least two of the following: lithium nickel cobalt manganese oxide (NCM), lithium cobalt oxide, lithium manganese oxide, or lithium nickel oxide.
4. The positive electrode of the soft-pack battery cell according to claim 3, characterized in that, The lithium nickel cobalt manganese oxide ternary material (NCM) is LiNi x Co y Mn z O2, x+y+z=1, where x=0.30~0.95, y=0.05~0.95; x is preferably 0.30~0.
75.
5. The positive electrode of the soft-pack battery cell according to claim 2, characterized in that, The lithium manganese iron phosphate described herein has an orthorhombic olivine-type crystal structure and the chemical formula LiMn. x Fe 1-x PO4, where 0.55≤x≤0.
85.
6. The positive electrode of the pouch cell according to claim 1 or 2, characterized in that, The mass percentages of lithium transition metal oxide, lithium iron phosphate (LFP), and lithium manganese iron phosphate (LMFP) in the active material are (5%–70%):(10%–70%):(0–30%).
7. The positive electrode of the pouch cell according to claim 1 or 2, characterized in that, The current collector is a carbon-coated aluminum foil with a double-sided carbon coating.
8. The method for preparing the positive electrode sheet of the pouch cell according to claim 1 or 2, characterized in that, The preparation method includes: A slurry containing the active material is formed; The slurry is coated onto the current collector, and then rolled and die-cut to form a positive electrode sheet.
9. A pouch cell, characterized in that, Includes the positive electrode sheet as described in claim 1 or 2.
10. A power battery, characterized in that, The power battery includes the pouch cell as described in claim 9.