Positive electrode plate and lithium-ion battery using the same

Abstract

To provide a positive electrode plate that can reduce the manufacturing cost of a battery, increase the pressed density of the electrode plate, and improve the volumetric energy density and cycle performance of the battery, and a lithium-ion battery using the positive electrode plate.SOLUTION: The present application provides a positive electrode plate and a lithium-ion battery. The positive electrode plate includes a current collector and a positive electrode active material layer. The positive electrode active material layer s a first active material layer and a second active material layer, both of which are provided in a composite manner. The first active material layer includes a spinel-type lithium manganese oxide material and a ternary material. The second active material layer includes a phosphate material. The dimensions of the single crystals of the spinel-type lithium manganese oxide and the ternary material are D1 and D2, respectively, and satisfy the following formula (1).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims priority to a Chinese patent application bearing application number 202410396103.8, filed with the China Patent Office on April 2, 2024, the entire contents of which are incorporated herein by reference.

[0002] The present application relates to a lithium ion battery, and more particularly to a positive electrode plate and a lithium ion battery using the same. [Background technology]

[0003] Lithium manganese iron phosphate materials have superior rate and low-temperature performance, but their dual-voltage platform makes battery management system (BMS) design more difficult. Therefore, lithium manganese iron phosphate materials are commonly mixed with ternary materials to smooth the charge / discharge curve, improve cycle stability, and enhance cycle performance. Some researchers are also exploring the use of lithium manganese oxide, which is cheaper, has a higher applied voltage, and can be mixed with lithium manganese iron phosphate. The combination of high-energy-density ternary materials, low-cost lithium manganese oxide materials, and long-cycle lithium manganese iron phosphate materials can lead to the realization of batteries with long cycle life and low cost.

[0004] However, related technologies typically involve directly mixing the three materials to form a slurry, which is then uniformly coated. However, the large differences in particle size, density, and pH of the three materials make uniform mixing difficult, resulting in difficult electrode plate processing. Furthermore, electrode plates obtained by simultaneously mixing the three materials have uneven particle distribution, which prevents the advantages of each material from being fully utilized. Another approach involves preparing the ternary material and the lithium manganese iron phosphate material as separate coatings and then applying them as a composite coating. However, this approach fails to utilize the gap-filling effect of the lithium manganese iron phosphate relative to the ternary material, resulting in a lower compacted density. Furthermore, the cost reduction and energy density improvement benefits of the simply formulated lithium manganese iron phosphate are not fully realized. Therefore, a low-cost, compacted electrode plate system design that meets energy density and cycle performance requirements is needed. Summary of the Invention [Problem to be solved by the invention]

[0005] The present application provides a positive electrode plate that can reduce the manufacturing cost of a battery, increase the pressed density of the electrode plate, and improve the volumetric energy density and cycle performance of the battery, and a lithium-ion battery using this positive electrode plate. [Means for solving the problem]

[0006] The present application provides a positive electrode plate comprising a current collector and a positive electrode active material layer coated on at least one side of the current collector, the positive electrode active material layer comprising a composite first active material layer and a second active material layer, the first active material layer including a spinel-type lithium manganese oxide material and a ternary material, the second active material layer including a phosphate material, the spinel-type lithium manganese oxide material containing lithium manganese oxide single crystal particles, the ternary material containing ternary single crystal particles, the primary particles of the spinel-type lithium manganese oxide material being D1, the primary particles of the ternary material being D2, and the spinel-type lithium manganese oxide material and the ternary material satisfying the following formula (1):

[0007]

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[0008] The present application further provides a lithium-ion battery, which includes the positive electrode plate described above. [Effects of the Invention]

[0009] The beneficial effects of the present application are as follows: The positive electrode plate provided in the present application is designed by controlling the morphology of the single crystal of the spinel-type lithium manganese oxide material and limiting both the size of the primary particles of the ternary material and the size of the primary particles of the lithium manganese oxide. When the dimensions satisfy the condition D2≧3.2*D1, the stacking density of the electrode plate can be optimized, and the volumetric energy density of the cell can be increased. On the other hand, when D2<3.2*D1, the optimal combination of the ternary material and the spinel-type lithium manganese oxide material cannot be achieved, and the maximum packing density cannot be achieved, resulting in a decrease in the volumetric energy density of the cell. In addition, taking advantage of the significant differences in pH values ​​between spinel lithium manganese oxide materials (pH 9.4-10.4), ternary materials (pH 10.4-12.0), and phosphate materials (pH 8.3-9.4), when mixing a spinel lithium manganese oxide material with a ternary material, if the dimensions of both materials satisfy the condition D2 ≥ 3.2 * D1, not only can the instability of the slurry obtained by directly mixing lithium manganese iron phosphate with the ternary material be avoided, but also weight balance effects can be maintained, the cost of the positive electrode system can be reduced, and the occurrence of interfacial layering between the phosphate material and the ternary material can be reduced, improving cycle performance. Furthermore, the application of a spinel lithium manganese oxide material to an electrode plate can improve the rate performance of the ternary material. Therefore, the positive electrode plate provided herein has excellent cycle performance, rate performance, and low cost.

[0010] The lithium-ion battery provided in the present application employs the above-described positive electrode plate and is excellent in cycle performance, rate performance, and low cost. [Brief explanation of the drawings]

[0011] [Figure 1] The first active material layer according to the present invention is the positive electrode plate placed on the side closer to the current collector. [Figure 2] The second active material layer according to the present invention is the positive electrode plate disposed on the side closer to the current collector. DETAILED DESCRIPTION OF THE INVENTION

[0012] In order to allow those skilled in the art to better understand the technical solutions in the present disclosure, the technical solutions in the present disclosure will be clearly and completely described in combination with the following examples and drawings of the examples. Obviously, the described examples are only a part, but not all, of the embodiments in the present disclosure.

[0013] Example 1 1. Preparation of the Positive Electrode Plate (1) Preparation of materials for making the positive electrode plate A positive electrode plate according to this example was fabricated. Positive electrode active materials that can be used for each active material layer in the positive electrode plate are shown in Table 1. The phosphate material used here is LiMn 0.6 Fe 0.4 PO4 has D3=200 nm.

[0014] Table 1 is a table describing the materials for making the positive electrode plate.

[0015] [Table 1]

[0016] (2) Method of making the positive electrode plate The spinel-type lithium manganese oxide material and ternary material shown in Table 1 are mixed in a mass ratio of 1:1. Next, the resulting mixed material, conductive carbon black, CNT, and PVDF are mixed in a mass ratio of 96:1:1:2. These materials are mixed and stirred uniformly using NMP as a solvent, and a first active material layer slurry is obtained.

[0017] The phosphate material, conductive carbon black, CNT, and PVDF shown in Table 1 are mixed in a mass ratio of 96:1:1:2. Next, these materials are mixed and stirred uniformly using NMP as a solvent, and a second active material layer slurry is obtained.

[0018] The first active material layer slurry and the second active material layer slurry were both applied onto a carbon-coated aluminum foil, with the first active material layer being applied on the side closer to the aluminum foil, and the surface density being 40 g / m 2 and the areal density of the second active material layer is 160 g / m 2 The positive electrode plate is obtained by drying, cold pressing (the electrode plate elongation rate is 0.5 to 0.7%), and die-cutting.

[0019] 2. Preparation of the Negative Electrode Plate A slurry of anode material (graphite), conductive agent (acetylene black), adhesive CMC, and SBR in a mass ratio of 94:1:2:3 is applied to a copper foil current collector. After vacuum drying, a cathode plate is obtained.

[0020] 3. Battery assembly The positive electrode plate, separator (a 14 μm separator manufactured by Sembcorp) and negative electrode plate prepared above are stacked in this order so that the separator acts as an isolator between the positive and negative electrodes, and then stacked or wound to obtain a cell. The cell is placed in an exterior (aluminum shell or flexible packaging, etc.) and dried. After that, an electrolyte (ZP507 type from China Blue Sky) is added at a liquid injection rate of 5.0 g / Ah. After vacuum sealing, standing, molding, capacity grading and other processes, a test secondary battery is obtained. In this example, the cathode active materials selected for fabricating the first and second active material layers, along with their primary particles, are variables, and different treatment groups and control groups are established. In Example 1, the variables for Treatment Groups 1A to 4A and Control Groups 1A to 2A are shown in Table 2. Except for the aforementioned differences, the steps for fabricating the cathode plate and lithium-ion battery in this example are consistent with the methods described above. The positive electrode plate produced from treatment group 1A of Example 1 is shown in FIG. 1, and the positive electrode plate produced from treatment group 5A of Example 1 is shown in FIG. Table 2 explains the variables of treatment groups 1A to 4A and control groups 1A to 2A in Example 1.

[0021] [Table 2]

[0022] Treatment group 5A In this process group, the positive electrode plate is fabricated with reference to the formulation provided in Process Group 1A of Example 1. This process group differs from Process Group 1A of Example 1 in that, when fabricating the positive electrode plate, a second active material layer slurry is applied to the side closer to the aluminum foil. Except for the aforementioned differences, the fabrication of the lithium-ion battery in this process group is strictly consistent with Process Group 1A of Example 1. Here, the positive electrode active material used for the second active material layer closer to the aluminum foil is LiMn with a D3 of 200 nm. 0.6 Fe 0.4 PO4, and for the first active material layer on the side away from the aluminum foil, the positive active material used was LiMn2O4 with a D1 of 0.5 μm and LiNi with a D2 of 3 μm. 0.8 Co 0.1 Mn 0.1 It is O2.

[0023] Control group 3A In this control group, the positive electrode plate is fabricated with reference to the formulation provided in Treatment Group 1A of Example 1. This control group differs from Treatment Group 1A of Example 1 in that when fabricating the positive electrode plate, only NCM811 is used for the first active material layer, and a mixture of lithium iron manganese phosphate material and lithium manganese oxide material is used for the second active material layer. Except for the aforementioned differences, the fabrication of the lithium ion battery in this control group is strictly consistent with Treatment Group 1A of Example 1. Here, for the first active material layer closest to the aluminum foil, the positive electrode active material used is LiNi with a D2 of 3 μm. 0.8 Co 0.1 Mn 0.1 For the second active material layer away from the aluminum foil, the positive electrode active material used is LiMnO with a D1 of 0.5 μm and LiMn with a D3 of 200 nm. 0.6 Fe 0.4 It is PO4.

[0024] Control group 4A In this control group, the positive electrode plate is fabricated with reference to the formulation provided in Treatment Group 1A. This control group differs from Treatment Group 1A in that, when fabricating the positive electrode plate, the material used for the first active material layer is NCM811, and the material used for the second active material layer is lithium manganese iron phosphate. Except for the aforementioned differences, the fabrication of the lithium ion battery in this control group is strictly consistent with Treatment Group 1A in Example 1. Here, for the first active material layer closest to the aluminum foil, the positive electrode active material used is LiNi with a D2 of 3 μm. 0.8 Co 0.1 Mn 0.1 O2, and for the second active material layer away from the aluminum foil, the positive electrode active material used is LiMn with a D3 of 200 nm. 0.6 Fe 0.4 It is PO4.

[0025] Control group 5A In this control group, the positive electrode plate is fabricated with reference to the formulation provided in Treatment Group 1A of Example 1. This control group differs from Treatment Group 1A of Example 1 in that, when fabricating the positive electrode plate, the material used for the first active material layer is NCM811, and the material used for the second active material layer is lithium manganate. Except for the aforementioned differences, the fabrication of the lithium-ion battery according to this control group is strictly consistent with Treatment Group 1A of Example 1. Here, for the first active material layer closest to the aluminum foil, the positive electrode active material used is LiNi with a D2 of 3 μm. 0.8 Co 0.1 Mn 0.1 O2, and for the second active material layer on the side away from the aluminum foil, the positive active material used is LiMn2O4 with a D1 of 0.5 μm.

[0026] Control group 6A In this control group, the positive electrode plate is fabricated with reference to the formulation provided in Treatment Group 1A of Example 1. This control group differs from Treatment Group 1A of Example 1 in that there is only one active material layer when fabricating the positive electrode plate, and this active material layer is obtained by mixing NCM811 and lithium manganese iron phosphate material at an areal density ratio of 2:8. Except for the above-mentioned differences, the fabrication of the lithium ion battery according to this control group is strictly consistent with Treatment Group 1A of Example 1. Here, for the active material layer, the positive electrode active material used is LiNi with D2 of 3 μm. 0.8 Co0.1Mn 0.1 O2 and LiMn with D3 of 200 nm 0.6 Fe 0.4 It is PO4.

[0027] Control group 7A In this control group, the positive electrode plate is fabricated with reference to the formulation provided in Treatment Group 1A of Example 1. This control group differs from Treatment Group 1A of Example 1 in that there is only one active material layer when fabricating the positive electrode plate, and this active material layer is obtained by mixing NCM811, lithium iron manganese phosphate, and lithium manganese oxide. Except for the above-mentioned differences, the fabrication of the lithium-ion battery in this control group is strictly consistent with Treatment Group 1A of Example 1. Here, for the active material layer, the positive electrode active materials used are LiMn2O4 with D1 of 0.5 μm and LiNi with D2 of 3 μm. 0.8 Co 0.1 Mn 0.1 O2, D3 200nm LiMn 0.6 Fe 0.4 Specifically, the procedure for preparing the electrode plate for this control group is as follows: Spinel-type lithium manganese oxide material (LiMn2O4), ternary material (LiNi 0.8 Co 0.1 Mn 0.1 O2) and phosphate materials (LiMn 0.6 Fe 0.4 PO4) are mixed in a mass ratio of 1:1:1, and then the mixed positive electrode active material, conductive carbon black, CNT, and PVDF are mixed in a mass ratio of 96:1:1:2. These materials are uniformly mixed and stirred using NMP as a solvent to obtain a positive electrode active material layer slurry. This positive electrode active material layer slurry is applied to the surface of aluminum foil, and then dried, cold pressed, and punched to obtain a positive electrode plate.

[0028] Test Example 1 1. Test Object 1 shows the batteries prepared in each treatment group and the control group in Example 1.

[0029] 2. Test Method Room temperature cycle performance: At 25°C, a lithium-ion battery is charged at a constant current of 0.5C (nominal capacity) to a voltage of 4.2V, then charged at a constant voltage of 4.2V until the current drops below 0.05C. After leaving the battery for 10 minutes, it is discharged at a constant current of 1C or 2C until the cutoff voltage reaches 2.5V. This constitutes one charge-discharge cycle. Each lithium-ion battery is subjected to charge-discharge cycles at 25°C according to the above conditions, and the number of cycles at which the capacity retention is 80% at different discharge rates is recorded. The capacity retention is calculated according to equation (3). Capacity retention rate (%) of a lithium-ion battery after N cycles = (Nth discharge capacity / 1st discharge capacity) × 100% Equation (3)

[0030] 3. Test Results and Analysis The test results of this test example are shown in Table 3. This test example primarily examined the effects of the different spinel-type lithium manganese oxide materials, ternary materials, and phosphate materials used, as well as the placement of the first and second active material layers, on the fabricated positive electrode plates. In the treatment groups 1A to 4A of Example 1, the effects of different D1, D2, and ternary materials were primarily examined. Among these, the battery fabricated in treatment group 1A exhibited excellent rate performance and cycle performance. On the other hand, when comparing treatment group 5A with treatment group 1A, although two positive electrode active material layers were exchanged, the electrical performance of the lithium-ion battery fabricated in treatment group 5A remained at a good level.

[0031] On the other hand, in the control groups 1A to 2A, the condition D2≧3.2*D1 is not satisfied, and therefore the cycle performance of the batteries using these groups is reduced.

[0032] In Control Group 3A, the first active material layer is a ternary material, and the second active material layer is a mixture of lithium manganese iron phosphate and lithium manganese oxide, so the rate performance and cycle performance of the battery using this group are significantly reduced.Compared to Control Group 3A, in Control Group 4A, the second active material layer is an electrode plate made only of lithium manganese iron phosphate, so the cycle performance of the battery using this group is significantly reduced.

[0033] In the control group 5A, the electrode plates were prepared by applying a ternary material and lithium manganese oxide, respectively, and the rate performance and cycle performance of the battery using this group were significantly reduced.

[0034] In the control group 6A, the electrode plate was fabricated by mixing and coating a ternary material and a phosphate material, and the rate performance of the battery using this group was significantly reduced. This is thought to be because the dispersibility of the slurry obtained by mixing the phosphate material and lithium manganese oxide was poorer than that of the slurry obtained by mixing the ternary material and lithium manganese oxide.

[0035] In the control group 7A, a positive electrode plate was fabricated by mixing and coating a spinel-type lithium manganese oxide material, a ternary material, and a phosphate material. However, the positive electrode active material slurry fabricated using this method was difficult to mix uniformly, and as a result, the rate performance and cycle performance of the lithium-ion battery using this group were significantly reduced.

[0036] Table 3 shows the test results of Test Example 1.

[0037] [Table 3]

[0038] Example 2 In this example, treatment groups 1B to 5B are set with reference to treatment group 2A of Example 1. Furthermore, treatment groups 1B to 5B of Example 2 use variables m1 and P1 of the first active material layer and m2 and P2 of the second active material layer. Except for the differences noted above, the steps for fabricating the positive electrode plates and lithium-ion batteries of treatment groups 1B to 5B of Example 2 closely correspond to those of treatment group 2A of Example 1.

[0039] Table 4 describes the variables for each treatment group in Example 2.

[0040] [Table 4]

[0041] Test Example 2 1. Test subjects 1 shows the batteries prepared in each treatment group of Example 2. 2. Test Method The test is carried out with reference to the test method in Test Example 1. 3. Test Results and Analysis The test results of this test example are shown in Table 5. Here, this test example mainly investigated the influence of the pressed density and mass ratio of the first and second active material layers on the positive electrode plates produced. From the test data, it can be seen that in treatment groups 1B to 5B, by adjusting the pressed density and mass ratio of the first and second active material layers, the pressed density of the positive electrode plate can be further optimized, and the volumetric energy density and cycle performance of the positive electrode can be improved.

[0042] Table 5 shows the test results of Test Example 2.

[0043] [Table 5]

Claims

1. A positive electrode plate, the positive electrode plate includes a current collector and a positive electrode active material layer coated on at least one side of the current collector, the positive electrode active material layer comprises a composite first active material layer and a composite second active material layer, the first active material layer includes a spinel-type lithium manganate material, a ternary material, and the second active material layer includes a phosphate material; the spinel-type lithium manganese oxide material contains lithium manganese oxide single crystal particles, and the ternary material contains ternary single crystal particles; The primary particles of the spinel-type lithium manganese oxide material are D １ and the primary particles of the ternary material are D ２ wherein the spinel-type lithium manganese oxide material and the ternary material satisfy the following formula (1): [Equation 1]

2. Primary particles D of the spinel-type lithium manganese oxide material １ is 0.5 to 2 μm, The positive electrode plate according to claim 1 .

3. The ternary material is LiNi ０．８ Co ０．１ Mn ０．１ O ２ and LiNi ０．８ Co ０．１ Al ０．１ O ２ The spinel-type lithium manganese oxide material includes any one of LiMn ２ O ４ and the phosphate material comprises LiMn ０．６ Fe ０．４ P.O. ４ Including, The positive electrode plate according to claim 1 or 2.

4. The ternary material is LiNi ０．８ Co ０．１ Mn ０．１ O ２ and D ２ is 3 μm, and the spinel-type lithium manganese oxide material is LiMn ２ O ４ and D １ is 0.5 μm, The positive electrode plate according to claim 3 .

5. The primary particles of the phosphate material are D ３ and D ３ is 100 nm to 600 nm, The positive electrode plate according to claim 1 or 2.

6. The phosphate material is LiMn ０．６ Fe ０．４ P.O. ４ and D ３ is 200 nm, The positive electrode plate according to claim 5 .

7. In the positive electrode active material layer, the mass ratio of the first active material layer is m １ and the pressed density of the first active material layer is P １ and the mass ratio of the second active material layer is m ２ and the pressed density of the second active material layer is P ２ and the pressed density of the positive electrode plate is P; The positive electrode plate satisfies the following formula (2): [Equation 2] Here, m １ :m ２ = 0.1 to 10:1, and m １ +m ２ = 1, The positive electrode plate according to claim 1 or 2.

8. In the first active material layer, the mass ratio of the spinel-type lithium manganate material to the ternary material is 0.1 to 5:

1. The positive electrode plate according to claim 7.

9. The pressed density P of the first active material layer １ is 2.9 to 3.8 g / cm ３ and / or the pressed density P of the second active material layer ２ is 2.0 to 2.5 g / cm ３ That is, The positive electrode plate according to claim 7.

10. The mass ratio m of the first active material layer １ is 0.9, and the pressed density P １ is 3.2 g / cm ３ and the mass ratio m of the second active material layer is ２ is 0.1, and the pressed density P ２ is 2.3 g / cm ３ That is, The positive electrode plate according to claim 9.

11. The positive electrode plate has a pressed density P of 2.3 to 3.6 g / cm ３ That is, The positive electrode plate according to claim 9.

12. the ratio of the areal density of the first active material layer to the areal density of the second active material layer is 5 to 60:50 to 200; The positive electrode plate according to claim 7.

13. The density of the coating surface of the first active material layer is 5 to 60 g / m ２ That is, The positive electrode plate according to claim 12.

14. The areal density of the first active material layer is 40 g / m ２ and the areal density of the second active material layer is 160 g / m ２ That is, The positive electrode plate according to claim 13.

15. the first active material layer of the first active material layer is coated on a side closer to the current collector, and the second active material layer is coated on a side of the first active material layer farther from the current collector; The positive electrode plate according to claim 1 or 2.

16. the first active material layer and the second active material layer of the first active material layer are coated on a side closer to the current collector, and the first active material layer is coated on a side of the second active material layer farther from the current collector; The positive electrode plate according to claim 1 or 2.

17. The positive electrode plate according to claim 1 or 2, Lithium-ion battery.

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