Method for manufacturing a positive electrode material for a secondary battery

Abstract

A method for manufacturing a cathode material of a secondary battery. First, a lithium metal phosphate material and a first conductive carbon are provided. The lithium metal phosphate material is composed of a plurality of secondary particles. Each of the plurality of secondary particles is formed by aggregation of a plurality of primary particles. A void is formed between the plurality of primary particles. Then, the lithium metal phosphate material and the first conductive carbon are mixed in a mechanical manner to form a composite material. In the composite material, the first conductive carbon is uniformly distributed in the voids between the particles. Then, an adhesive, a solvent, and a second conductive carbon are provided. Finally, the composite material, the adhesive, the solvent, and the second conductive carbon are mixed to form a cathode material for constituting a positive electrode plate.

Description

Technical Field

[0001] This case relates to a method for manufacturing a cathode material for a secondary battery, especially a method for manufacturing a cathode material for a secondary battery that can stably improve the charge and discharge performance of the battery. Background Art

[0002] In today's rapidly developing technology, reusable secondary batteries are widely used in fields such as electric vehicles and energy storage. In order to pursue higher efficiency and convenience, these secondary batteries are required to have good energy density and charge and discharge performance. It is worth noting that the performance of secondary batteries is usually closely related to the cathode materials selected.

[0003] As a cathode material for secondary batteries, for example, lithium metal phosphate (LiMPO4) needs to be mixed with conductive carbon, binder, and solvent to make an electrode. However, in this existing manufacturing process, various process parameters need to be adjusted to ensure the uniformity of each component, and then provide good charge and discharge performance. Since the process parameters need to be adjusted extremely precisely, it is difficult to ensure the uniformity of each component in the electrode, and the uneven composition will have an adverse effect on the performance of the battery.

[0004] In view of this, how to develop a method for manufacturing a cathode material for a secondary battery that can stably improve the charge and discharge performance of the battery is an important issue that this technical field urgently wants to solve. Summary of the Invention

[0005] The object of the present case is to provide a method for manufacturing a positive electrode material for a secondary battery that can stably improve the charge and discharge performance of the battery. The lithium metal phosphate material is composed of a plurality of secondary particles, and each of the plurality of secondary particles is composed of a plurality of primary particles. The lithium metal phosphate material and a first conductive carbon are formed into a composite material by a mechanical method such as mechanical fusion, so that the first conductive carbon in the composite material is uniformly distributed in the inter-particle voids formed between the plurality of primary particles. The composite material is then mixed with a second conductive carbon, an adhesive, and a solvent, for example, by a defoaming mixer to form a positive electrode material, and then coated on a substrate such as an aluminum foil to form a positive electrode plate. By pre-mixing a part of the conductive carbon with the lithium metal phosphate material in a mechanical manner, the conductive carbon is uniformly distributed between the primary particles of the lithium metal phosphate material, thereby reducing the interface impedance caused by the inter-particle voids and improving the uniformity of the material composition. Since a part of the conductive carbon already exists in the composite material, when the composite material, the adhesive, and the solvent are mixed into a slurry subsequently, only a small amount of conductive carbon needs to be added to form the required positive electrode material. By adding less conductive carbon during the slurry mixing, the viscosity of the slurry can be reduced and the solid content can be increased, thereby increasing the surface density (loading density) of the positive electrode material on the substrate and further improving the adhesion between the positive electrode material and the substrate. The positive electrode material formed by the foregoing method has a simple manufacturing process and is easy to control. The positive electrode plate prepared therefrom also maintains a high capacitance at a high charge and discharge rate (C-rate) and has good fast charging performance.

[0006] To achieve the above object, the present case provides a method for manufacturing a positive electrode material for a secondary battery, which includes the steps of: (a) providing a lithium metal phosphate material and a first conductive carbon, wherein the lithium metal phosphate material is composed of a plurality of secondary particles, each of the plurality of secondary particles is aggregated by a plurality of primary particles, and an inter-particle void is formed between the plurality of primary particles; (b) mixing the lithium metal phosphate material and the first conductive carbon in a mechanical manner to form a composite material, wherein in the composite material, the first conductive carbon is uniformly distributed in the inter-particle voids; (c) providing a second conductive carbon, an adhesive, and a solvent; and (d) mixing the composite material, the second conductive carbon, the adhesive, and the solvent to form a positive electrode material for constituting a positive electrode plate.

[0007] In one embodiment, the composition of the lithium metal phosphate material includes LiMPO4, wherein M is selected from iron, nickel, cobalt, manganese, magnesium, titanium, aluminum, tin, chromium, vanadium, molybdenum, and combinations thereof.

[0008] In one embodiment, the particle size range of the plurality of primary particles is between 50 nm and 500 nm.

[0009] In one embodiment, the particle size range of several secondary particles is between 2 μm and 100 μm.

[0010] In one embodiment, the particle size range of the first conductive carbon is between 10 nm and 200 nm.

[0011] In one embodiment, the mechanical method is a Mechanofusion method.

[0012] In one embodiment, the operating temperature range of the mechanical method is between 25 °C and 35 °C.

[0013] In one embodiment, the rotational speed range of the mechanical method is between 100 rpm and 2000 rpm.

[0014] In one embodiment, the weight percentage of the first conductive carbon in the composite material is between 0.5% and 10%.

[0015] In one embodiment, step (d) further includes the steps of: (d1) coating the positive electrode material on a substrate and drying it to form a positive electrode plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a flowchart of the manufacturing method of the positive electrode material of the secondary battery in this case.

[0017] Figure 2 It is a schematic structural diagram of the secondary particles in this case.

[0018] Figure 3 It is a schematic structural diagram of the composite material in this case.

[0019] Figure 4 It is a schematic structural diagram of the positive electrode plate composed of the positive electrode material in this case.

[0020] Figure 5A It is the potential-capacity charge curve of the control group and Example 1 in this case at different charge-discharge rates (C-rate).

[0021] Figure 5B It is the potential-capacity discharge curve of the control group and Example 1 in this case at different charge-discharge rates (C-rate).

[0022] Figure 6A It is the potential-capacity charge curve of the control group and Example 2 in this case at different charge-discharge rates (C-rate).

[0023] Figure 6B It is the potential-capacity discharge curve of the control group and Example 2 in this case at different charge-discharge rates (C-rate).

[0024] Figure 7A It is the potential-capacity charge curve of the control group and Example 3 in this case at different charge-discharge rates (C-rate).

[0025] Figure 7B It is the potential-capacitance discharge curves of the control group and Demonstration Example 3 in this case at different charge-discharge rates (C-rate).

[0026] Figure 8A It is the potential-capacitance charge curves of the control group and Demonstration Example 4 in this case at different charge-discharge rates (C-rate).

[0027] Figure 8B It is the potential-capacitance discharge curves of the control group and Demonstration Example 4 in this case at different charge-discharge rates (C-rate).

[0028] Figure 9A It is the capacitance-cycle number charge curves of the control group, Demonstration Example 1, Demonstration Example 2, Demonstration Example 3, and Demonstration Example 4 in this case at different charge-discharge rates (C-rate).

[0029] Figure 9B It is the capacitance-cycle number discharge curves of the control group, Demonstration Example 1, Demonstration Example 2, Demonstration Example 3, and Demonstration Example 4 in this case at different charge-discharge rates (C-rate).

[0030] Among them, the reference numerals are explained as follows:

[0031] 1: Composite material

[0032] 2: Positive plate

[0033] 10: Secondary particle

[0034] 100: Primary particle

[0035] 200: Inter-particle void

[0036] B: Adhesive

[0037] C1: First conductive carbon

[0038] C2: Second conductive carbon

[0039] S: Substrate

[0040] S1, S2, S3, S4: Steps Detailed implementation manners

[0041] Some typical embodiments reflecting the features and advantages of this case will be described in detail in the following description. It should be understood that this case can have various changes in different aspects, all of which do not depart from the scope of this case, and the descriptions and drawings therein are essentially for illustrative purposes and not for limiting this case.

[0042] Please refer to Figures 1 to 4 。 Figure 1Flow chart of the manufacturing method of the positive electrode material of the secondary battery in this case. Figure 2 Schematic diagram of the structure of the secondary particles in this case. Figure 3 Schematic diagram of the structure of the composite material in this case. Figure 4 Schematic diagram of the structure of the positive electrode plate composed of the positive electrode material in this case. First, as shown in step S1, a lithium metal phosphate material and a first conductive carbon C1 are provided. The lithium metal phosphate material is composed of a plurality of secondary particles 10. As Figure 2 shown, each of the plurality of secondary particles 10 is aggregated by a plurality of primary particles 100, and an inter-particle gap 200 is formed between the plurality of primary particles 100. The composition of the lithium metal phosphate material includes LiMPO4, where M is selected from iron, nickel, cobalt, manganese, magnesium, titanium, aluminum, tin, chromium, vanadium, molybdenum, and combinations thereof. In this embodiment, the lithium metal phosphate material is, for example, a lithium iron phosphate with carbon coating (LFP / C), and the first conductive carbon C1 is, for example, Super P. Super P has high purity and good electrical conductivity, and will disperse around the particles to form a branched conductive network, enabling the electrolyte to ideally contact the oxide particles, thereby increasing the overall electrical conductivity of the positive electrode plate 2. Of course, this case is not limited thereto, and the first conductive carbon C1 can also be, for example, carbon materials such as carbon nanotubes or graphene. In this embodiment, the particle size range of the plurality of primary particles 100 is between 50 nm and 500 nm. The particle size range of the plurality of secondary particles 10 is between 2 μm and 100 μm. The particle size range of the first conductive carbon C1 is between 10 nm and 200 nm.

[0043] Next, as shown in step S2, the lithium metal phosphate material such as LFP / C and the first conductive carbon C1 such as Super P are mechanically mixed to form a composite material 1. As Figure 3 shown, in the composite material 1, the first conductive carbon C1 such as Super P is uniformly distributed in the inter-particle gap 200. By distributing the conductive carbon between the primary particles 100, the interface impedance inside the secondary particles 10 such as lithium metal phosphate (LFP) can be reduced. In this embodiment, the mechanical method is, for example, a Mechanofusion method, and the working temperature range is, for example, between 25 °C and 35 °C, and the rotation speed range is, for example, between 100 rpm and 2000 rpm. In the composite material 1, the weight percentage of the first conductive carbon C1 such as Super P is, for example, between 0.5% and 10%.

[0044] Then, as shown in step S3, a second conductive carbon C2, an adhesive B, and a solvent are provided. In this embodiment, the second conductive carbon C2 is, for example, Super P, the adhesive B is, for example, polyvinylidene fluoride (PVDF), and the solvent is, for example, N-methyl-2-pyrrolidone (NMP).

[0045] Finally, as shown in step S4, composite material 1, second conductive carbon C2, adhesive B, and a solvent are mixed to form a positive electrode material. In this embodiment, the positive electrode material is formed by mixing, for example, in a degassing mixer. When mixing, the weight ratio of the lithium metal phosphate material, the total amount of conductive carbon (the total of the first conductive carbon C1 and the second conductive carbon C2), and the adhesive B is, for example, 8:1:1. Of course, the weight ratio can be adjusted according to actual needs, and this case is not limited thereto. In this embodiment, the positive electrode material formed by mixing composite material 1, adhesive B, solvent, and second conductive carbon C2 is coated on a substrate S, such as an aluminum foil, and dried to form a positive electrode plate 2. The structure of the positive electrode plate 2 is as Figure 4 shown. Composite material 1 is located on substrate S, adhesive B is located on the outer layer of the secondary particles 10, and second conductive carbon C2 is located between the secondary particles 10.

[0046] The manufacturing process and effects of this case will be described in detail below by way of exemplary examples.

[0047] Exemplary Example 1:

[0048] Provide a lithium metal phosphate material and a first conductive carbon. The lithium metal phosphate material is composed of a plurality of secondary particles, and each of the plurality of secondary particles is aggregated from a plurality of primary particles. The lithium metal phosphate material is lithium iron phosphate with carbon coating (LFP / C), and the first conductive carbon is Super P. The lithium iron phosphate (LFP) secondary particles are spherical and aggregated from a plurality of primary particles. A particle gap is formed between the plurality of primary particles.

[0049] The lithium metal phosphate material and the first conductive carbon are mixed mechanically to form a composite material. The first conductive carbon is uniformly distributed in the particle gap. The composite material is prepared by mixing at a working temperature range between 25°C and 35°C by the Mechanofusion method at a rotation speed of 600 rpm for 10 minutes and then at a rotation speed of 1200 rpm for 30 minutes. In the composite material, the weight percentage of the first conductive carbon is approximately 0.47%.

[0050] Provide a second conductive carbon, an adhesive, and a solvent. The second conductive carbon is Super P, the adhesive is PVDF, and the solvent is NMP.

[0051] Mix the composite material, the second conductive carbon, the adhesive, and the solvent to form a positive electrode material, and then coat the positive electrode material on a substrate and dry it to form a positive electrode plate. When mixing, the weight ratio of the lithium metal phosphate material, the conductive carbon (the sum of the first conductive carbon and the second conductive carbon), and the adhesive is 8:1:1. In other words, the weight of the second conductive carbon added needs to be adjusted accordingly considering the weight percentage of the first conductive carbon in the composite material. Since the weight percentage of the first conductive carbon in the composite material in this exemplary embodiment is approximately 0.47%, the weight ratio of the composite material, the second conductive carbon, and the adhesive is 8.04:0.96:1. When mixing, first add the solvent into a defoaming mixer and operate it at a speed of 1200 rpm for 30 minutes. Then, add the second conductive carbon and the adhesive and operate it at a speed of 1200 rpm for 30 minutes. Finally, add the composite material and operate it at a speed of 1200 rpm for 60 minutes, and then operate it at 130 rpm for 30 minutes. After mixing is completed, coat the formed positive electrode material on a substrate made of aluminum foil and dry it to form a positive electrode plate.

[0052] Exemplary Embodiment Two:

[0053] The manufacturing process of Exemplary Embodiment Two is substantially the same as that of Exemplary Embodiment One. In the composite material of Exemplary Embodiment Two, the weight percentage of the first conductive carbon is approximately 1.21%. Accordingly, the weight ratio of the composite material, the second conductive carbon, and the adhesive added to the defoaming mixer in Exemplary Embodiment Two is 8.1:0.9:1.

[0054] Exemplary Embodiment Three:

[0055] The manufacturing process of Exemplary Embodiment Three is substantially the same as that of Exemplary Embodiment One. In the composite material of Exemplary Embodiment Three, the weight percentage of the first conductive carbon is approximately 3.65%. Accordingly, the weight ratio of the composite material, the second conductive carbon, and the adhesive added to the defoaming mixer in Exemplary Embodiment Three is 8.3:0.7:1.

[0056] Exemplary Embodiment Four:

[0057] The manufacturing process of Exemplary Embodiment Four is substantially the same as that of Exemplary Embodiment One. However, in the composite material of Exemplary Embodiment Four, the weight percentage of the first conductive carbon is approximately 8.09%. Accordingly, the weight ratio of the composite material, the second conductive carbon, and the adhesive added to the defoaming mixer in Exemplary Embodiment Four is 8.17:0.3:1.

[0058] Control Group:

[0059] In the control group, the lithium metal phosphate material was not pre-mixed with the first conductive carbon to form a composite material. Instead, the lithium metal phosphate material, the second conductive carbon, and the adhesive were directly added to the defoaming mixer at a weight ratio of 8:1:1, and a positive electrode plate was formed using the same manufacturing process as in Exemplary Embodiment One.

[0060] Please refer to Figures 5A to 8B . Figures 5A to 5B These are the charge-discharge test curves of the control group and Example 1 of this case at charge-discharge rates (C-rate) of 1C, 3C, and 5C respectively. Figures 6A to 6B These are the charge-discharge test curves of the control group and Example 2 of this case at charge-discharge rates (C-rate) of 1C, 3C, and 5C respectively. Figures 7A to 7B These are the charge-discharge test curves of the control group and Example 3 of this case at charge-discharge rates (C-rate) of 1C, 3C, and 5C respectively. Figures 8A to 8B These are the charge-discharge test curves of the control group and Example 4 of this case at charge-discharge rates (C-rate) of 1C, 3C, and 5C respectively. Figures 5A to 8B These are the results of the half-cell tests of the positive plates of Example 1 to 4 and the control group of this case under the same conditions. As shown in the figure, when Example 1 to 4 of this case are charged and discharged at charge-discharge rates (C-rate) of 1C, 3C, and 5C, their capacitances are all greater than that of the control group. It is worth noting that under the condition of a higher charge-discharge rate (C-rate), the capacitances of Example 1 to 4 are more significantly improved compared with the control group, showing good fast-charging performance.

[0061] Table 1 below shows the comparison of the capacitance test results when the control group, Example 1, Example 2, Example 3, and Example 4 are charged to 4.2V at a charge-discharge rate (C-rate) of 1C. As shown in Table 1, compared with the control group, the capacitances of Example 1 to 4 at a potential of 4.2V are all slightly improved, with the improvement range being approximately between 1% and 4%. Among them, Example 2 with the weight percentage of the first conductive carbon in the composite material being 1.21% is the best. It can be seen from this that in this case, by mechanically pre-distributing the lithium metal phosphate material and the conductive carbon in advance, the conductive carbon is evenly distributed and the proportion of the conductive carbon during subsequent mixing is reduced, thereby increasing the surface density during coating and the adhesion between the positive electrode material and the substrate. Thereby, the capacitance of the positive electrode material of this case is improved, showing good charge-discharge performance.

[0062] Table 1

[0063]

[0064] Table 2 below shows the comparison of the capacitance test results when the control group, Example 1, Example 2, Example 3, and Example 4 are charged to 4.2V at a 3C charge-discharge rate (C-rate). As shown in Table 2, compared with the control group, the capacitances of Examples 1 to 4 at a potential of 4.2V are all significantly improved, and the improvement range is approximately between 5% and 12%. Among them, Example 2 with the weight percentage of the first conductive carbon in the composite material being 1.21% is the best. It can be seen that in this case, by mechanically mixing the lithium metal phosphate material and the conductive carbon in advance, the conductive carbon is evenly distributed and the proportion of the conductive carbon added during subsequent mixing is reduced, thereby increasing the surface density during coating and the adhesion between the positive electrode material and the substrate. Thereby, the capacitance of the positive electrode material in this case is improved, and it has good charge-discharge performance.

[0065] Table 2

[0066]

[0067] Table 3 below shows the comparison of the capacitance test results when the control group, Example 1, Example 2, Example 3, and Example 4 are charged to 4.2V at a 5C charge-discharge rate (C-rate). As shown in Table 3, compared with the control group, the capacitances of Examples 1 to 4 at a potential of 4.2V are all significantly improved. It is worth noting that the improvement range of the capacitances of Examples 1 to 3 is approximately between 20% and 30%. Among them, Example 2 with the weight percentage of the first conductive carbon in the composite material being 1.21% is the best. It can be seen that in this case, by mechanically mixing the lithium metal phosphate material and the conductive carbon in advance, the conductive carbon is evenly distributed and the proportion of the conductive carbon added during subsequent mixing is reduced, thereby increasing the surface density during coating and the adhesion between the positive electrode material and the substrate. Thereby, the positive electrode material in this case also maintains a high capacitance at a high charge-discharge rate (C-rate) and has good fast charging performance.

[0068] Table 3

[0069]

[0070] Please refer to Figures 9A to 9B 。 Figure 9A are the capacitance-cycle number charge curves of the control group, Example 1, Example 2, Example 3, and Example 4 in this case at different charge-discharge rates (C-rate). Figure 9B are the capacitance-cycle number discharge curves of the control group, Example 1, Example 2, Example 3, and Example 4 in this case at different charge-discharge rates (C-rate). Figures 9A to 9BResults of half-cell tests on the positive plates of Examples 1 to 4 and the control group of this case under the same conditions. The control group, Example 1, Example 2, Example 3, and Example 4 were respectively subjected to capacitance tests for 5 to 10 cycles at charge-discharge rates (C-rates) of 0.1C, 0.2C, 0.5C, 1C, 3C, 5C, and 10C. As shown in the figure, at charge-discharge rates (C-rates) of 1C, 3C, and 5C, the capacitances of Examples 1 to 3 of this case were significantly higher than those of the control group. It can be seen from this that in this case, by pre-mixing the lithium metal phosphate material and the conductive carbon mechanically, the conductive carbon is evenly distributed and the proportion of conductive carbon added during subsequent mixing is reduced, thereby increasing the surface density during coating and the adhesion between the positive electrode material and the substrate. Thereby, the positive electrode material of this case also maintains a high capacitance at a high charge-discharge rate (C-rate) and has good fast charging performance.

[0071] In summary, this case provides a manufacturing method for a secondary battery positive electrode material that stably improves the charge-discharge performance of the battery. A lithium metal phosphate material is composed of a plurality of secondary particles, and each of the plurality of secondary particles is composed of a plurality of primary particles. The lithium metal phosphate material and a first conductive carbon are formed into a composite material by a mechanical method such as mechanical fusion, so that the first conductive carbon in the composite material is evenly filled in the inter-particle voids formed between the plurality of primary particles. The composite material is then mixed with a second conductive carbon, an adhesive, and a solvent, for example, by a defoaming mixer to form a positive electrode material, which is then coated on a substrate such as an aluminum foil to form a positive electrode plate. By pre-mixing part of the conductive carbon with the lithium metal phosphate material mechanically, the conductive carbon is filled between the primary particles of the lithium metal phosphate material, thereby reducing the interface impedance caused by the inter-particle voids and improving the uniformity of the material composition. Since part of the conductive carbon already exists in the composite material, only a small amount of conductive carbon needs to be added when the composite material, the adhesive, and the solvent are mixed into a slurry subsequently to form the required positive electrode material. By adding less conductive carbon during the slurry mixing, the viscosity of the slurry can be reduced and the solid content can be increased, thereby increasing the surface density (Loading density) of the positive electrode material on the substrate and further improving the adhesion between the positive electrode material and the substrate. The positive electrode material formed by the foregoing method has a simple process and is easy to control. The positive electrode plate prepared therefrom also maintains a high capacitance at a high charge-discharge rate (C-rate) and has good fast charging performance.

[0072] This case can be modified by those skilled in the art, but all modifications shall not depart from the scope of protection as claimed in the appended patent application.

Claims

1. A method for manufacturing a positive electrode material for a secondary battery, which includes the steps of: (a) providing a lithium metal phosphate material and a first conductive carbon, wherein the lithium metal phosphate material is composed of a plurality of secondary particles, each of the plurality of secondary particles is formed by aggregation of a plurality of primary particles, and a particle - to - particle void is formed between the plurality of primary particles; (b) mechanically mixing the lithium metal phosphate material and the first conductive carbon to form a composite material, wherein in the composite material, the first conductive carbon is uniformly distributed in the particle - to - particle voids, wherein the mechanical method is a mechanical fusion method, and the rotational speed range of the mechanical method is between 100 rpm and 2000 rpm; (c) providing a second conductive carbon, an adhesive, and a solvent; and (d) mixing the composite material, the second conductive carbon, the adhesive, and the solvent to form the positive electrode material for forming a positive electrode plate.

2. The method for manufacturing a positive electrode material for a secondary battery according to claim 1, wherein the composition of the lithium metal phosphate material includes LiMPO4, wherein M is selected from iron, nickel, cobalt, manganese, magnesium, titanium, aluminum, tin, chromium, vanadium, molybdenum, and combinations thereof.

3. The method for manufacturing a positive electrode material for a secondary battery according to claim 1, wherein the particle size range of the plurality of primary particles is between 50 nm and 500 nm.

4. The method for manufacturing a positive electrode material for a secondary battery according to claim 1, wherein the particle size range of the plurality of secondary particles is between 2 μm and 100 μm.

5. The method for manufacturing a positive electrode material for a secondary battery according to claim 1, wherein the particle size range of the first conductive carbon is between 10 nm and 200 nm.

6. The method for manufacturing a positive electrode material for a secondary battery according to claim 1, wherein the working temperature range of the mechanical method is between 25 °C and 35 °C.

7. The method for manufacturing a positive electrode material for a secondary battery according to claim 1, wherein in the composite material, the weight percentage of the first conductive carbon is between 0.5% and 10%.

8. The method for manufacturing a positive electrode material for a secondary battery according to claim 1, wherein step (d) further includes the step of: (d1) coating the positive electrode material on a substrate and drying it to form the positive electrode plate.

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