Battery positive electrode plate and manufacturing method thereof, battery

Abstract

The present invention discloses a composite positive electrode material, a positive electrode plate and its manufacturing method, and a battery. The composite positive electrode material includes a ternary material (11) and a phase change material (12). The phase change material (12) undergoes a phase transition during the charge / discharge cycle of the ternary material (11). The ternary material (11) has a single crystal structure, and the phase change material (12) has a single crystal structure or a polycrystalline structure and is coated on the surface of the ternary material (11). The mass fraction ratio of the ternary material (11) to the phase change material (12) is 80:20 to 99.8:0.2. The ternary material (11) has a nanohardness of 0.001 to 5 GPa, and the phase change material (12) has a nanohardness of 0.01 to 10 GPa.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority from Chinese Patent Application No. 202010821206.6, entitled "Composite positive electrode material, positive electrode plate and manufacturing method thereof, and battery," filed with the State Intellectual Property Office of the People's Republic of China on August 14, 2020, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to the technical field of batteries, and more particularly to a composite positive electrode material, a positive electrode plate and its manufacturing method, and a battery. [Background technology]

[0003] Because of its high energy density, ternary materials are widely used as cathode materials for electric vehicle batteries. As the requirements for energy density of electric vehicles continue to increase, the ternary materials used are also becoming increasingly popular. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 to LiNi 0.5 Co 0.2 Mn 0.3 O2, and many ternary material companies have already 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 We have begun to develop high nickel materials such as O2, LiNiO2, and NCA.

[0004] However, ternary high-nickel materials have problems such as poor room-temperature cycling performance, increased DCIR (direct current resistance at a specific load and discharge current) after cycling, severe post-cycling gas generation, and poor safety performance. To solve these problems with ternary high-nickel materials, current technological approaches use optimization of coating, doping, and sintering processes to maximize the structural stability of the material, mitigate capacity degradation due to phase transitions during long-term cycling, and improve the safety of the material. However, these technological approaches cannot fundamentally solve the phase transition changes within a fixed charge / discharge range of the material, and only improve the structural stability of the material. Summary of the Invention

[0005] The present invention has been made to solve at least one of the above problems. Specifically, a composite positive electrode material according to one aspect of the present invention includes a ternary material and a phase change material, the phase change material undergoes a phase transition in the charge / discharge range of the ternary material, the ternary material has a single crystal structure, the phase change material has a single crystal structure or a polycrystalline structure, and is coated on the surface of the ternary material, the mass fraction ratio of the ternary material to the phase change material is 80:20 to 99.8:0.2, and the nanohardness of the ternary material is 0.001 to 5 GPa the nano-hardness of the phase-change material is 0.01-10 GPa, the D50 of the ternary material is 3.0-6.0 μm, and the D50 of the primary particles of the phase-change material is 10-50 nm.

[0006] In one embodiment of the present invention, the nano-hardness of the ternary material is 0.2-1.4 GPa, and the nano-hardness of the phase-change material is 1.5-3.5 GPa.

[0007] In one embodiment of the present invention, the tap density of the ternary material is 2.0 to 2.8 g / cm 3 and the tap density of the phase change material is 0.8 to 1.5 g / cm 3 is.

[0008] In one embodiment of the present invention, the D50 of the ternary material is 3.5-5.0 μm, and the particle size D50 of the primary particles of the phase change material is 20-40 nm.

[0009] In one embodiment of the present invention, the chemical formula of the ternary material is LiNi x Co y M z O2, where x+y+z=1 and M includes Mn, Al, Zr, Ti, Y, Sr, or W.

[0010] In one embodiment of the present invention, the ternary material comprises a nickel-cobalt-manganese ternary material or a nickel-cobalt-aluminum ternary material.

[0011] In one embodiment of the present invention, the phase change material has an olivine structure and the chemical formula of the phase change material is LiA v B w PO4, where v+w=1, A contains Fe, Co, Mn, Ni, Cr, or V, and B contains Fe, Co, Mn, Ni, Cr, or V.

[0012] In one embodiment of the present invention, the phase change material includes lithium iron manganese phosphate, lithium vanadium manganese phosphate or lithium iron chromium phosphate.

[0013] According to another aspect of the present invention, there is provided a method for preparing a composite cathode material according to the present invention, comprising: feeding a ternary material, a phase change material, and an NMP solvent in a mechanofusion apparatus at a certain mass ratio to fuse them to form a composite material; and sintering the fused composite material at a certain temperature to obtain the composite cathode material, wherein the ternary material is a single crystal material, and the particle size D50 of the ternary material is 3.0-6.0 μm; the phase change material is a single crystal material or a secondary spheroidized material, and the particle size D50 of the primary particle of the phase change material is 10-50 nm; the mass fraction ratio of the ternary material to the phase change material is 80:20-99.8:0.2; and the nano-hardness of the ternary material is 0.001-5. GPa and the nano-hardness of the phase change material is 0.01 to 10 GPa.

[0014] In one embodiment of the present invention, the rotation speed of the mechanofusion device is 4000 to 7000 r / min, and the fusion time is 10 to 30 min.

[0015] In one embodiment of the present invention, the rotation speed of the mechanofusion device is 4500 to 6500 r / min, and the fusion time is 15 to 25 minutes.

[0016] In one embodiment of the present invention, the composite material is fired at a temperature of 80 to 120° C. for a firing time of 0.5 to 2.5 hours.

[0017] In one embodiment of the present invention, the composite material is baked at a temperature of 95 to 105° C. for a baking time of 1 to 2 hours.

[0018] A positive electrode plate according to yet another embodiment of the present invention includes a current collector and the composite positive electrode material according to the present invention disposed on the current collector.

[0019] In one embodiment of the present invention, the intensity ratio of the crystal orientation (003) / (110) of the positive electrode plate after compression is 10-100.

[0020] According to yet another aspect of the present invention, there is provided a method for producing a positive electrode plate according to the present invention, comprising the steps of: adding PVDF having an F-containing group and / or a carboxyl group, an ester group, or an amino group in a polymer chain to a certain amount of NMP solvent to form a PVDF solution; adding a certain amount of a conductive material to the PVDF solution and stirring to form a slurry; after a certain period of time, adding the composite positive electrode material according to the present invention to the slurry and stirring sufficiently to obtain a final slurry; and applying the final slurry to a current collector, followed by high-temperature firing to remove the NMP solvent in the slurry, rolling and slicing to obtain a positive electrode plate.

[0021] In one embodiment of the present invention, the method further comprises the step of adding an amount of lithium carbonate to the slurry before the step of obtaining the final slurry.

[0022] A battery according to a further aspect of the present invention comprises a positive electrode plate according to the present invention, a negative electrode plate, and a separator disposed between the positive and negative electrode plates.

[0023] In the composite positive electrode material, positive electrode plate, manufacturing method thereof, and battery according to the present invention, the positive electrode material comprises a ternary single crystal material and a phase change material coated on the surface of the ternary single crystal material. The ternary single crystal material itself has the advantages of high high-temperature performance, little gas generation, and high safety. Meanwhile, the phase change material coated on the surface of the ternary material can increase the thermal runaway onset temperature of the ternary material and the battery and reduce heat dissipation during thermal runaway, thereby improving safety. Furthermore, the phase change material can mitigate or delay the phase transition of the ternary material during the charge and discharge cycles, thereby reducing capacity degradation due to the phase transition of the ternary material during long-term cycling, thereby improving the cycle performance of the battery and reducing the increase in resistance during material aging, thereby improving battery safety.

[0024] Furthermore, in the embodiments of the present invention, the nano-hardness of the ternary material and the phase change material is limited to restrict the directional orientation of the (003) crystal orientation of the ternary material, and the tap density of the ternary material and the phase change material is limited to achieve a high green density of the electrode plate, thereby ensuring the energy density of the battery. [Brief explanation of the drawings]

[0025] In order to more clearly describe the technical means in the embodiments of the present invention, the following briefly introduces drawings necessary for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative efforts.

[0026] [Figure 1] 1 is a schematic diagram showing the configuration of a composite positive electrode material according to an embodiment of the present invention. [Figure 2] 1 is a CV graph showing a conventional ternary material and a composite cathode material according to an embodiment of the present invention. [Figure 3] 3 shows an enlarged view of a portion of the CV graph shown in FIG. 2. [Figure 4] 1 shows the directional orientation of the (003) crystal orientation of a ternary single crystal material and a composite cathode material according to an embodiment of the present invention. [Figure 5] 1 shows XRD patterns of a conventional ternary material and a composite positive electrode material according to an embodiment of the present invention after compression. [Figure 6] 1 is a schematic flow chart illustrating a method for making a composite cathode material according to the present invention. [Figure 7] 1 is a schematic flow chart showing a method for manufacturing a positive electrode plate according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] In the following description, many specific details are provided to provide a more thorough understanding of the present invention. However, as will be apparent to those skilled in the art, the present invention can be practiced without one or more of these details. In other instances, some technical features known in the art will not be described to avoid confusion with the present invention.

[0028] It is understood that the present invention may be embodied in many different forms and should not be construed as limited to the examples provided herein. Rather, these examples are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity, and like reference numerals refer to like elements throughout.

[0029] It should be understood that when an element or layer is referred to as being "on," "adjacent to," or "connected to" or "coupled to" another element or layer, the element or layer may be directly on, adjacent to, connected to, or coupled to the other element or layer, or intervening elements or layers may be present. Rather, when an element is referred to as being "directly on," "directly adjacent to," or "directly connected to," or "directly coupled to," there are no intervening elements or layers. It should be understood that, although terms such as first, second, and third may be used to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Thus, without departing from the teachings of the present invention, a first element, first component, first region, first layer or first portion discussed below may be referred to as a second element, second component, second region, second layer or second portion.

[0030] Spatial relationship terms such as "below," "below," "below," "below," "above," and the like may be used herein for convenience of description to describe the relationship of one element or feature to other elements or features shown in the figures. As will be understood, in addition to the orientation shown in the figures, the spatial relationship terms are intended to further encompass different orientations of the device during use and operation. For example, if the device in the figures is inverted, elements or features described as being "below" or "beneath" or "below" other elements or features would be oriented so as to be "above" the other elements or features. Thus, the exemplary terms "below" and "below" may include both above and below orientations. The device may be oriented in another orientation (rotated 90 degrees or oriented in another direction), and the spatial relationship descriptors used herein would be interpreted accordingly.

[0031] The purpose of the terms used herein is to describe specific embodiments only and is not intended to limit the present invention. As used herein, the singular forms "a," "one," and "the" are intended to include the plural forms unless the context clearly dictates otherwise. It is further understood that the terms "comprise" and / or "comprise," when used herein, specify the presence of said features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. As used herein, the term "and / or" includes any and all combinations of the associated listed items.

[0032] In order to thoroughly understand the present invention, the following description will provide detailed structures to explain the technical means of the present invention. Preferred embodiments of the present invention will be described in detail as follows, but in addition to these detailed descriptions, the present invention can also have other embodiments.

[0033] As mentioned above, ternary high-nickel materials have problems such as poor room-temperature cycling performance, increased DCIR (direct current resistance at a specific load and discharge current) after cycling, severe post-cycling gas generation, and poor safety performance. To address these issues with ternary high-nickel materials, current techniques optimize coating, doping, and sintering processes to maximize the structural stability of the material, thereby mitigating capacity degradation due to phase transitions during long-term cycling and improving the safety of the material. However, these techniques do not fundamentally address the phase transition changes within a fixed charge / discharge range of the material and only improve its structural stability. The present invention addresses these current issues by improving the cycling performance and safety of the material through improved material stability from the perspectives of plate design and battery design.

[0034] The idea of ​​the present invention is to improve the cycle performance and safety of ternary materials by coating the surface of the ternary material with a phase change material based on improving the structural stability of the main body material. The general idea is to utilize the charge / discharge characteristics of different materials to share more of the charge / discharge tasks in the charge / discharge range of about 4.25 V (potential relative to Li) of the high-nickel material, thereby mitigating or delaying the phase transition during the charge / discharge period of the material. Furthermore, by uniformly coating the surface of the ternary material with a phase change material, the coating layer acts as a heat shield, further increasing the onset temperature of thermal runaway of the material and reducing the heat released during the thermal runaway process.

[0035] As shown in FIG. 1 , the composite positive electrode material of the present invention includes a ternary material 11 and a phase change material 12. The phase change material 12 undergoes a phase transition during the charge and discharge cycles of the ternary material. The phase change material 12 serves to mitigate or delay the phase transition of the ternary material during the charge and discharge cycles, thereby mitigating the capacity degradation caused by the phase transition of the ternary material during long-term cycling, thereby improving the cycle performance of the battery, reducing the increase in resistance during the aging process of the material, and improving the safety of the battery.

[0036] Illustratively, the mass ratio of the ternary material to the phase-change material is 80:20 to 99.8:0.2, and illustratively, the mass ratio of the ternary material to the phase-change material is 90:10 to 95:5.

[0037] Illustratively, in an embodiment of the present invention, the chemical formula of the ternary material is LiNi x Co y M z O2, where x+y+z=1, and M includes, but is not limited to, Mn, Al, Zr, Ti, Y, Sr, or W. By way of example, the ternary material includes a nickel-cobalt-manganese ternary material (i.e., NCM) or a nickel-cobalt-aluminum ternary material (i.e., NCA). By way of example, the ternary material is a high-nickel ternary material, such as LiNi x Co y M z In O2, x is greater than 0.6.

[0038] The phase change material has a single crystal structure or a polycrystalline structure. For example, the phase change material has an olivine structure. The chemical formula of the phase change material is LiA v B w PO4, where v+w=1, A includes, but is not limited to, Fe, Co, Mn, Ni, Cr, or V, and B includes, but is not limited to, Fe, Co, Mn, Ni, Cr, or V. Exemplary phase change materials include lithium manganese iron phosphate, lithium manganese vanadium phosphate, or lithium chromium iron phosphate. Exemplary phase change materials include lithium manganese iron phosphate (LMFP), which has the structure LiMn x Fe y PO4, where the value of x ranges from 0.05 to 0.95, preferably from 0.5 to 0.85, the value of y ranges from 0.05 to 0.95, preferably from 0.15 to 0.5, and the material is a single crystal material.

[0039] In this example, the phase change material undergoes a phase transition between 4.0 and 2.0 V, and when the phase change material and the high-nickel material are used to form a composite positive electrode material, the structural phase transition of the high-nickel material at 4.25 V (potential relative to Li) can be weakened or delayed.

[0040] For example, the ternary material is NCM811, and the composite material is a ternary material coated with LMFP. The CV curves of a battery plate made with the composite material are shown in Figures 2 and 3. Figure 3 is a partial enlargement of Figure 2, with Curve 1 showing the CV curve of NCM811 and Curve 2 showing the CV curve of the composite cathode material. As can be seen from Figures 2 and 3, the CV curve of the plate made with the composite cathode material exhibits a new oxidation peak around 4.15 V, while the current intensity of the oxidation peak of the NCM811 material at about 4.25 V is reduced. This indicates that adding a certain amount of an existing material (e.g., lithium iron manganese phosphate, lithium vanadium manganese phosphate, lithium iron chromium phosphate, etc.) that undergoes a phase transition between 4.0 and 2.0 V, e.g., between 3.95 and 4.15 V, can weaken or delay the structural phase transition of high-nickel materials at 4.25 V (potential relative to Li).

[0041] Furthermore, in order to further improve the cycle performance and safety of the battery, the present invention uses a single crystal material as the ternary material, and a single crystal ternary material coated with a phase transition material such as LMFP as the composite material. In this way, the ternary single crystal material itself has the advantages of high high-temperature performance, little gas generation, and high safety, while the phase transition material is uniformly coated on the surface of the ternary material, and the coating layer has a heat-insulating effect, which further increases the thermal runaway onset temperature of the material and reduces the heat released during the thermal runaway process, thereby improving the safety performance of the material.

[0042] Furthermore, a single-crystal material is used as the ternary material. The single-crystal ternary material exhibits directional orientation in the (003) crystal direction after compression of the electrode plates. As shown in Figure 4, this directional orientation causes expansion in the thickness direction of the material, affecting battery performance, leading to uneven distribution of the battery electrolyte during charging and discharging, causing lithium precipitation, and deteriorating battery performance. In accordance with an embodiment of the present invention, the surface of the ternary material is coated with an LMFP material whose primary particles are nanoscale. This coating layer effectively prevents the directional orientation of the (003) crystal direction of the ternary material, reducing the expansion of the ternary material and electrode plates in the thickness direction and improving battery performance.

[0043] Furthermore, in order to better restrict the directional orientation of the 003 crystal orientation of the ternary single crystal material, in the embodiment of the present invention, the nano-hardness of the ternary material and the coating material is limited. For example, the nano-hardness of the ternary material is 0.001 to 5 GPa and the nanohardness of the coating material is 0.01 to 10 GPa. Illustratively, the nanohardness of the ternary material is 0.2 to 1.4 GPa, and the nanohardness of the coating material is 1.5 to 3.5 GPa. By limiting the nanohardness of the ternary material and the coating material, it is possible to restrict the directional orientation of the 003 crystal orientation of the ternary single crystal material, thereby reducing expansion of the ternary material and the electrode plate in the thickness direction and improving battery performance.

[0044] Figure 5 shows XRD patterns of a conventional ternary material and a composite positive electrode material according to an embodiment of the present invention after compression. Curve 3 shows the XRD pattern of the conventional ternary material after compression, and curve 4 shows the XRD pattern of the composite positive electrode material according to an embodiment of the present invention after compression. As shown in Figure 5, the (003) / (110) intensity ratio in the XRD of the composite positive electrode material according to an embodiment of the present invention after compression is lower than the (003) / (110) intensity ratio in the XRD of the conventional ternary material after compression, indicating that the directional orientation of the (003) plane in the ternary single crystal material is suppressed. Illustratively, in the embodiment of the present invention, the (003) / (110) intensity ratio in the XRD of the conventional ternary material after compression ranges from 5 to 200, and the (003) / (110) intensity ratio in the XRD of the composite positive electrode material according to an embodiment of the present invention after compression ranges from 10 to 100.

[0045] Furthermore, in this embodiment, the coating material is a material such as LMFP, and the green density of LMFP is low, which affects the energy density of the battery. Therefore, in this embodiment, the tap densities of the ternary material and the coating material are limited to achieve a high green density of the electrode plate and ensure the energy density of the battery. For example, in this embodiment, the tap density of the ternary material is 2.0 to 2.8 g / cm. 3 and the tap density of the coating material is 0.8 to 1.5 g / cm 3 is.

[0046] Furthermore, in this embodiment, in order to achieve uniform distribution of the coating material on the surface of the ternary single crystal material, a material whose primary particles are nanoscale is used as the coating material, the D50 of the ternary material is 3.0 to 6.0 μm, and the particle size D50 of the primary particles of the coating material is 10 to 50 nm.

[0047] Furthermore, in an embodiment of the present invention, in order to improve the safety performance of the material and the battery, a certain amount of lithium carbonate may be added to the slurry of the composite positive electrode material. The lithium carbonate can generate gas in the event of battery failure, thereby accelerating the reversal and opening time of the CID and explosion-proof valve and preventing the occurrence of more serious thermal runaway. For example, the lithium carbonate content of the composite positive electrode material is 2 to 10%.

[0048] In the composite positive electrode material according to the embodiment of the present invention, a ternary single crystalline material is used, and the surface of the ternary single crystalline material is coated. In this way, the ternary single crystalline material itself has the advantages of high high-temperature performance, little gas generation, and high safety. Meanwhile, the coating material provides a heat-insulating effect on the surface of the ternary material, which can increase the thermal runaway onset temperature of the ternary material and the battery and reduce the heat release during thermal runaway, thereby improving safety. In addition, the coating material can mitigate or delay the phase transition of the ternary material during the charge and discharge interval, and mitigate the capacity degradation caused by the phase transition of the ternary material during long-term cycling, thereby improving the cycling performance of the battery and reducing the increase in resistance during the aging process of the material, thereby improving the safety of the battery.

[0049] Furthermore, in the embodiments of the present invention, the nano-hardness of the ternary material and the coating material is limited to restrict the directional orientation of the (003) crystal orientation of the ternary material, and the tap density of the ternary material and the coating material is limited to realize a high green density of the electrode plate, thereby ensuring the energy density of the battery.

[0050] According to another embodiment of the present invention, a method for producing the composite positive electrode material according to the present invention includes the following steps 101 and 102, as shown in FIG.

[0051] In step 101, a certain mass ratio of the ternary material, the phase change material, and the NMP solvent is placed in a mechanofusion device to fuse together to form a composite material.

[0052] Illustratively, in this embodiment, the ternary material is a single crystal material, and the particle size D50 of the ternary material is 3.0-6.0 μm; the phase change material is a single crystal material or a secondary spheroidized material, and the particle size D50 of the primary particle of the phase change material is 10-50 nm; the mass fraction ratio of the ternary material to the phase change material is 80:20-99.8:0.2; and the nano-hardness of the ternary material is 0.001-5. GPa The nano-hardness of the phase transition material is 0.01 to 10 GPa.

[0053] Examples of the ternary material and phase transition material are as described above, and a description thereof will be omitted here.

[0054] The above-mentioned ternary material and phase change material can be manufactured by a general method in this field. For example, NCM is used as the ternary material and LMFP is used as the phase change material. The manufacturing method thereof is, for example, as follows.

[0055] The manufacturing method of the ternary material is as follows: Ternary material precursor (Ni x Co y Mn z (OH)2) and a lithium source are mixed, and then pre-sintered, first sintered, first crushed, second sintered and second crushed to obtain a ternary material; the lithium source is one or more of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium acetate; The sintering conditions for the pre-sintering are a sintering temperature of 200 to 500°C and a sintering time of 4 to 6 hours.

[0056] The first sintering includes a constant temperature stage, a temperature increase stage, and a temperature decrease stage, and the temperature of the first constant temperature stage is 800-1000°C, and the time of the first constant temperature stage is 5-8 hours, the temperature of the second constant temperature stage is 1000-1100°C, and the time of the second constant temperature stage is 8-10 hours, and the temperature of the third constant temperature stage is 1100-1200°C, and the time of the third constant temperature stage is 5-10 hours; the temperature in the first temperature-raising stage is 200 to 800°C, and the temperature-raising time in the first temperature-raising stage is 1.5 to 3.5 hours; the temperature in the second temperature-raising stage is 800 to 1000°C, and the temperature-raising time in the second temperature-raising stage is 1.5 to 3.5 hours; the temperature in the third temperature-raising stage is 1000 to 1200°C, and the temperature-raising time in the third temperature-raising stage is 1.0 to 2.5 hours; The temperature in the first temperature-reducing stage is 1200 to 800°C, and the temperature-reducing time in the first temperature-reducing stage is 1.5 to 3 hours, and the temperature in the second temperature-reducing stage is 800 to 200°C, and the temperature-reducing time in the second temperature-reducing stage is 0.5 to 2 hours.

[0057] The first crushing is carried out as follows. As a preliminary crushing, the polycrystalline body is subjected to first ball milling. The rotation speed of the first ball milling is 4000 to 8000 r / min, preferably 5500 to 7500 r / min. Subsequently, air crushing is carried out. The pressure of the air crushing is 5 to 10 MPa, preferably 6.5 to 8.5 MPa.

[0058] Before the second sintering, a coating agent is added to the crushed material, and the coating agent includes one or more of the elements Ti3O4, Mg(OH)2, W2O3, Al2O3, Co(OH)2, and H3BO3.

[0059] The sintering conditions for the second sintering are that the temperature for the second sintering is 500 to 800°C, and preferably 550 to 750°C.

[0060] Regarding the important parameters of the second crushing, the second crushing is performed using mechanical polishing, and the rotation speed during mechanical polishing is 2000 to 4000 r / min, preferably 2500 to 3500 r / min.Through the above process, a ternary positive electrode material is obtained.

[0061] The manufacturing method of LMFP materials is as follows: The method involves mixing FePO4, Li2CO3, glucose, and water in a certain ratio, then subjecting the mixed material to coarse and fine grinding to form an aqueous solution, spray-drying the aqueous solution to form a mixture of the three materials, and then solid-state sintering at a certain high temperature. After the first sintering, the material is air-flow pulverized to obtain the LMFP material.

[0062] In one embodiment of the present invention, the rotation speed of the mechanofusion device is 4000-7000 r / min, and the fusion time is 10-30 min. In another embodiment, the rotation speed of the mechanofusion device is 4500-6500 r / min, and the fusion time is 15-25 min.

[0063] In step 102, the fused composite material is fired at a certain temperature to obtain a composite cathode material.

[0064] For example, in one embodiment of the present invention, the composite material is baked at a temperature of 80 to 120°C for a baking time of 0.5 to 2.5 hours. For example, the composite material is baked at a temperature of 95 to 105°C for a baking time of 1 to 2 hours.

[0065] A positive electrode plate for a battery according to another aspect of the present invention includes a current collector and a composite positive electrode material according to any of the embodiments of the present invention disposed on the current collector.

[0066] Illustratively, the current collector is, for example, an aluminum foil.

[0067] For example, the intensity ratio of the crystal orientation (003) / (110) of the positive electrode plate after compression is 10-100.

[0068] The positive electrode plate of the present invention, because it uses the composite positive electrode material described in the examples of the present invention, has similar advantages, namely, it can improve the cycle performance of the battery, reduce the increase in resistance during the aging process of the material, and improve the safety of the battery.

[0069] A battery according to yet another embodiment of the present invention includes a positive electrode plate according to any of the embodiments of the present invention, a negative electrode plate, and a separator and an electrolyte disposed between the positive and negative electrode plates.

[0070] For example, the positive electrode plate includes a current collector and the composite positive electrode material described in the embodiment of the present invention disposed on the current collector, and for example, the positive electrode current collector includes aluminum foil. As can be understood, a conductive agent and a binder are further disposed on the positive electrode current collector, and for example, the mass ratio of the composite positive electrode material:binder:conductive agent is 100:2.0:2.2.

[0071] For example, the composite positive electrode material is a single-crystalline NCM coated with an LMFP material whose primary particles are nanoscale. The binder is PVDF (polyvinylidene fluoride), which has special functional groups in its polymer chain. These special functional groups include, for example, F-containing groups, carboxyl groups, ester groups, or amino groups added to the polymer chain. Adding F-containing groups can improve gel resistance, while adding carboxyl groups, ester groups, or amino groups can improve binding strength. The conductive agent is a combination of conductive agents such as conductive carbon black, CNTs of different diameters, and graphene. These conductive agents can achieve point-to-point, point-to-line, and line-to-line mutual conduction, thereby better forming a complete conductive network. Because these two materials are nanoscale and micronscale, respectively, dot-like, line-like, and even planar conductive agents are required to form a complete conductive network.

[0072] Illustratively, the negative electrode plate includes a current collector and a negative electrode material disposed on the current collector. Illustratively, the negative electrode current collector includes copper foil, and graphite is used as the negative electrode material. For example, the mass ratio of graphite:binder:CMC:conductive agent is 100:1.9:1.6:1.2. Illustratively, artificial graphite, in which secondary particles are coated with carbon, is used as the negative electrode graphite. The secondary particles are manufactured as aggregates of primary particles. The surfaces are then coated with carbon to improve conductivity. This improves rate and low-temperature performance, while reducing the inherent expansion of the graphite itself.

[0073] Illustratively, the electrolyte solution includes one or more of EC, DMC, EMC, DEC, VC, and PS, where EC is ethylene carbonate, an abbreviation for ethylene carbonate, DMC is dimethyl carbonate, an abbreviation for dimethyl carbonate, EMC is ethyl methyl carbonate, an abbreviation for ethyl methyl carbonate, DEC is diethyl carbonate, an abbreviation for diethyl carbonate, VC is vinylene carbonate, an abbreviation for vinylene carbonate, and PS is polystyrene, an abbreviation for polystyrene.

[0074] For example, the separator has a composite structure made of PE, ceramic, and adhesive.

[0075] The batteries according to the embodiments of the present invention have similar advantages, namely, they can improve the cycle performance of the battery, reduce the resistance increase during the aging process of the material, and improve the safety of the battery, because they use the composite positive electrode materials described in the embodiments of the present invention.

[0076] A method for manufacturing a positive electrode plate according to an embodiment of the present invention, according to still another aspect of the present invention, includes the following steps 201 to 204.

[0077] In step 201, PVDF is added to a certain amount of NMP solvent to form a PVDF solution, i.e., PVDF is dissolved. PVDF is used as the PVDF, specifically, PVDF specially designed for high-nickel materials. Specifically, the PVDF has F-containing groups and carboxyl groups, ester groups, or amino groups in its polymer chain, making the PVDF gel-resistant. The NMP (Chinese name: N-methylpyrrolidone, English name: N-methyl-2-pyrrolidone) solvent can prevent PVDF from coagulating. The content of NMP can be determined as needed and is not specifically limited.

[0078] In step 202, a certain amount of conductive agent material is added to the PVDF solution and stirred to form a slurry.

[0079] For example, a certain amount of conductive material is added to the PVDF solution, and then the mixture is thoroughly stirred with a vacuum high-speed material blending device, such as a vacuum high-speed planetary disperser, to form a slurry.

[0080] Illustratively, the stirring time is, for example, 10 to 50 minutes.

[0081] For example, the conductive material may be a combination of conductive carbon black, CNTs with different diameters, graphene, and other conductive materials.

[0082] In step 203, after a certain time, the composite cathode material according to the present invention is added to the above slurry and stirred thoroughly to obtain a final slurry.

[0083] For example, after 10 to 50 minutes, a composite positive electrode material is added to the slurry and thoroughly stirred to obtain a final slurry. The composite positive electrode material is as described above, and therefore, a detailed description thereof will be omitted here.

[0084] In step 204, the final slurry is applied to a current collector, which is then calcined at a high temperature to remove the NMP solvent in the slurry, rolled, and sliced ​​to obtain a positive electrode plate.

[0085] Illustratively, before obtaining the final slurry, the method further includes adding a certain amount of lithium carbonate to the slurry to improve the safety performance of the battery and the material.

[0086] The present invention further carries out experimental tests on the positive electrode plate manufactured by the above method and a battery using the positive electrode plate to verify the battery performance.

[0087] Specific experiments The positive electrode plate is made of the following material: composite positive electrode material: binder: conductive agent = 100:2.0:2.2. The composite positive electrode material is a ternary single crystal material coated with an LMFP material whose primary particles are nanoscale. The binder is PVDF, which has special functional groups in the polymer chain. The conductive agent is a combination of conductive carbon black, CNTs of different diameters, graphene, and other conductive agents.

[0088] The negative electrode plate had a graphite:binder:CMC:conductive agent=100:1.9:1.6:1.2 ratio, and the negative electrode graphite was artificial graphite in which secondary particles were coated with carbon. A mixed solution of EC, DMC, EMC, DEC, VC, and PS is used as the electrolyte.

[0089] The separator is made of PE, ceramic, and adhesive.

[0090] Experimental process In this experiment, the slurry's components and weight percentages were 2.1% PVDF5130, 1.9% conductive agent, and 96% composite positive electrode material (Ni83 coated with LMFP material with nanoscale primary particles). The manufacturing process involved dissolving PVDF, adding different types of conductive agent, and then adding the composite positive electrode material. The ratio of composite positive electrode material, PVDF, and conductive agent in the slurry was 96:2.1:1.9.

[0091] The experimental parameters and performance test results are shown in Tables 1 and 2 below.

[0092] [Table 1] [Table 2] The interpretation of the parameters in the above table and the explanation of the performance test method are as follows:

[0093] Regarding the crystal orientation (003) / (110) of the electrode plate after compression, the intensity ratio of (003) / (110) in XRD of the electrode plate made of the uncoated positive electrode material ranges from 5 to 200, and the intensity ratio of (003) / (110) of the electrode plate made of the composite positive electrode material coated with the ternary material ranges from 10 to 100.

[0094] Regarding the density of the green powder of the electrode plate, the density of the green powder used for the electrode plate of the ternary material is generally 3.0 g / cm 3 Due to process limitations and the possibility of material crushing, the green density is generally 3.8 g / cm 3 Not exceeding 45℃~C500 refers to the capacity retention rate of the battery. The upper limit of this range is 100% without degradation. However, there is also a sudden drop in the capacity retention rate during the battery cycling process, and the capacity retention rate is very low, below 50%. The thickness change rate / % of the battery at 60°C and -28D is mainly used to evaluate the gas generation of the battery. If the battery does not generate gas and the change rate is 0, this change rate is optimal. If the amount of gas generation of the battery is large, the change rate may exceed 100%. The rate (5C / 0.2C discharge ratio) evaluates the battery's high current discharge capability, and the value is generally 50% to 98%. Low temperature (-20°C / 25°C discharge ratio) evaluates the low temperature discharge capability of the battery, and the value varies greatly depending on the battery, and may be 5% to 90%.

[0095] Test methods and results of the above experiments Regarding particle size, 1) the test equipment is a laser particle size meter, the standard model is Malvern 2000 / 3000; 2) The test method is to disperse the material in deionized water, ultrasonicate it for 10 minutes, set the refractive index of the particles to 1.74, and provide data such as D0.01, D10, D50, D90, D99 of the volume distribution and raw data.

[0096] The tap density is tested using the Dandong Baite (BT-1001) intelligent powder comprehensive testing machine. The powder material is placed in a 100ml measuring cylinder and weighed. The measuring cylinder is placed in the testing machine and vibrated at a frequency of 300 times / min. After the vibration is completed, the volume of the powder in the measuring cylinder is measured. The tap density is calculated based on the weight and volume of the powder.

[0097] Nanohardness is measured using a nanoindenter, with continuous load changes controlled by a computer and indentation depth monitored online. The complete indentation process includes two steps: a load application process and a load release process. In the load application process, an external load is applied to the indenter, causing it to indent the sample surface. As the load increases, the indenter indents deeper into the sample. When the load reaches a maximum value, the external load is removed, leaving an indentation mark on the sample surface. Nanohardness is calculated from the applied pressure and the indentation area. Nanohardness is related to the selected crystal plane.

[0098] The crystal orientation (003) / (110) of the electrode plate after compression was measured according to the general rules for X-ray diffraction method for polycrystalline materials in JY / T 009-1996. Regarding the electrode plate green density, the uncompressed positive electrode plate is cut into a size of 40*100mm and compressed using an Ohno green density machine. The electrode plate green density is calculated based on the areal density of the electrode plate and the thickness of the electrode plate after compression.

[0099] For 45°C to C500, the test method is to set the temperature condition to 45±5°C, charge to 4.2V at a constant current of 1C, discharge to 2.5V at a constant current of 1C, and after 500 cycles, calculate the capacity retention rate, i.e., C500, based on the discharge capacity C1 of the first cycle.

[0100] Regarding the battery thickness change rate / % at 60°C and -28D, the battery was charged to 4.2V at a constant current of 0.2C, left at room temperature for 2 hours, and the initial thickness of the battery was recorded. The battery was then placed in a thermostatic cabinet at 60°C and stored for 28D, and the thickness after storage was recorded and the thickness change was calculated.

[0101] For the rate (5C / 0.2C discharge ratio), charge to 4.2V at a constant current of 0.2C at 25°C, then discharge to 2.5V at constant currents of 0.2C and 5C at different rates. Calculate the percentage of 0.2C and 5C discharge capacity.

[0102] For low temperature (-20℃ / 25℃ discharge ratio), store in a thermostatic chamber at 25℃ for 6 hours, then store at -20℃ for 12 hours, charge at room temperature of 25℃ at a constant current of 0.2C up to 4.2V / cell, then discharge at a constant current of 1 / 3C down to 2.5V / cell under temperature conditions of 25℃ and -20℃. Calculate the ratio of the discharge capacity of both.

[0103] The composite positive electrode materials in Examples 1 to 14 all have excellent performance. Specifically, regarding the orientation of the compressed electrode plate manufactured from the composite positive electrode material, the larger the intensity ratio of the (003) peak to the (110) peak, the stronger the orientation of the composite positive electrode material, and the clearer the orientation in which the C axis of the composite positive electrode material is perpendicular to the current collector. The smaller the ratio, the weaker the orientation in which the C axis of the composite positive electrode material is perpendicular to the current collector, and the more irregular the distribution of its layered structure, which alleviates the change in the thickness of the electrode plate due to the contraction and expansion of the crystal lattice volume during the charge and discharge process. The ratio of the (003) peak intensity to the (110) peak intensity can reach a minimum of 11.5 and a maximum of only 20, which indicates that the composite positive electrode material produced in the examples has low orientation, which is advantageous for mitigating the degree of expansion of the electrode plate during charge and discharge. Regarding the green density of the electrode plate produced from the composite positive electrode material, a higher green density is more advantageous for improving the battery energy density, and a lower green density is less advantageous for achieving the battery energy density. In the examples, the maximum high-pressure powder density of the electrode plate was 3.62 g / cm. 3 can reach a minimum of 3.45 g / cm 3The electrode plate has a high green density, primarily due to the high tap density of both the main material and the coating material in the composite positive electrode material. For batteries fabricated with the composite positive electrode material, the capacity retention after 500 cycles at 45°C, the battery thickness change rate after 28 days of storage at 60°C, rate performance, and low-temperature discharge performance are primarily related to the particle size of the NCM in the composite positive electrode material, the particle size of the primary particles of the coating material, and the mass ratio between the main material and the coating material in the composite. The larger the particle size of the NCM in the composite, the larger the particle size of the primary particles of the coating material, which reduces the degree of side reactions between the material and the electrolyte, reduces gas generation from the material, reduces the amount of Mn dissolution from the coating material, improves cycle performance, and reduces the battery thickness change rate after storage. However, the larger the particle size, the longer the diffusion path for lithium ions, which reduces the rate performance and low-temperature performance of the battery. In the example, the composite positive electrode material had a capacity retention rate of up to 94% and a minimum of 86% after 500 cycles at 45°C, and a battery thickness change rate of up to 5% and a maximum of 12% after 28 days of storage at 60°C. The composite positive electrode material exhibited high high-temperature performance. The discharge rate at a 5C rate was up to 95% and a minimum of 85%, and the low-temperature discharge rate at -20°C was up to 85% and a minimum of 78%, demonstrating high low-temperature and rate performance.

[0104] In Comparative Example 1, the proportion of LMFP in the composite positive electrode material was too high, and the two materials had different structures. This resulted in a large diffusion resistance of lithium ions during the charge and discharge process, which in turn reduced the high-temperature cycle performance, rate performance, and low-temperature performance of the battery, as well as a reduced green density of the electrode plate.

[0105] In Comparative Example 2, the positive electrode material was not coated, and the crystal orientation of the electrode plate after compression was not well suppressed. As a result, the electrode plate expanded and contracted during the charge and discharge process of the material, causing uneven distribution of the electrolyte inside the battery and lithium precipitation inside the battery, resulting in poor cycle performance of the battery.

[0106] In Comparative Example 3, the particle size of the main NCM material in the composite positive electrode material is too large, and the diffusion path of lithium ions is too long during the charge and discharge process, resulting in poor low-temperature performance and rate performance of the battery.

[0107] In Comparative Example 4, when the particle size of the coating material LMFP in the composite positive electrode material is too large, the low temperature performance and rate performance of the battery are also reduced.

[0108] In Comparative Example 5, when the particle size of the main NCM material in the composite positive electrode material is too small, the specific surface area increases, which increases side reactions with the electrolyte, deteriorating the cycle characteristics of the battery, increasing gas generation after storage, and correspondingly decreasing the green density of the electrode plate.

[0109] In Comparative Example 6, when the particle size of the coating material LMFP in the composite positive electrode material is too small, the amount of dissolved Mn increases, the green density of the electrode plate decreases, and the high-temperature cycle performance deteriorates.

[0110] In Comparative Example 7, the hardness of the main NCM material in the composite positive electrode material is too low, so that it is preferentially compacted after compaction, and the directional orientation of the crystals is not suppressed. Also, because the hardness is too low, the particles are easily fractured after compaction, resulting in a large amount of new surface area being exposed to the electrolyte, which increases side reactions and reduces the cycling performance of the material.

[0111] In Comparative Example 8, the hardness of the main NCM material in the composite positive electrode material was too high, and the LMFP did not have an inhibitory effect on the directional orientation of its crystals. As a result, the electrode plate expanded and contracted during the charge and discharge process, causing uneven distribution of the electrolyte inside the battery and lithium precipitation inside the battery, resulting in poor cycle performance of the battery and a certain decrease in the green density of the electrode plate.

[0112] In Comparative Example 9, the hardness of the LMFP in the composite positive electrode material was too high, and the LMFP material was a nano-scale particle material. Therefore, when the electrode plate was compacted, the nano-material entered the NCM, and the LMFP did not have an inhibitory effect on the directional orientation of its crystals. The surface of the NCM material was destroyed, resulting in poor battery cycle performance.

[0113] Although exemplary embodiments have been described herein with reference to the drawings, it should be understood that the above-described exemplary embodiments are merely illustrative and are not intended to limit the scope of the present invention. Those skilled in the art may make various changes and modifications without departing from the scope and spirit of the present invention. All such changes and modifications are intended to be included within the scope of the present invention as defined in the appended claims.

[0114] In the specification provided herein, many specific details are set forth. However, it will be understood that embodiments of the present invention may be practiced without these specific details. In some embodiments, well-known methods, structures and techniques are not shown in detail in order not to obscure an understanding of this specification.

[0115] Similarly, it will be understood that in the description of exemplary embodiments of the present invention, features of the present invention may be grouped together in a single embodiment, figure, or description thereof to simplify the present invention and facilitate understanding of one or more of the inventive aspects. However, this method of the present invention should not be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. More specifically, as the corresponding claims reflect, the inventive concept is capable of solving the corresponding technical problem using fewer than all features of a single disclosed embodiment. Therefore, the claims according to specific embodiments are expressly incorporated into the specific embodiments, and each claim itself is a separate embodiment of the present invention.

[0116] As will be understood by those skilled in the art, all features disclosed in this specification (including the accompanying claims, abstract and drawings) and all processes or units of any method or apparatus so disclosed may be combined in any combination other than mutual exclusivity between features. Unless expressly stated otherwise, each feature disclosed in this specification (including the accompanying claims, abstract and drawings) may be replaced with an alternative feature serving the same, equivalent or similar purpose.

[0117] Furthermore, as will be understood by those skilled in the art, although some embodiments described herein may include some features included in other embodiments but not other features included in other embodiments, a combination of features from different embodiments is within the scope of the present invention and means to form different embodiments. For example, in the claims, any of the claimed embodiments may be used in any combination.

[0118] It should be noted that the above embodiments are illustrative of the present invention, but not limiting, and that those skilled in the art may design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs in parentheses shall not be construed as limiting the claims. The present invention may be realized by hardware comprising several distinct elements and by a suitably programmed computer. In a unit claim enumerating several devices, several of such devices may be embodied by the same hardware. The use of words such as first, second, and third does not indicate any order. Such words may be construed as names.

Claims

1. A positive electrode plate for a battery, comprising: a current collector; and a composite positive electrode material disposed on the current collector, the composite positive electrode material comprising: a ternary material and a phase change material, the phase change material undergoing a phase transition during the charge / discharge range of the ternary material; the phase change material is coated on the surface of the ternary material; the mass fraction ratio of the ternary material to the phase-change material is 80:20 to 99.8:0.2; The nano-hardness of the ternary material is 0.2-1.4 GPa, and the nano-hardness of the phase-change material is 1.5-3.5 GPa; the D50 of said ternary material is 3.0-6.0 μm and the D50 of the primary particles of said phase change material is 10-50 nm; The chemical formula of the ternary material is LiNi ｘ Co ｙ M ｚ O ２ where x+y+z=1 and M comprises Mn, Al, Zr, Ti, Y, Sr, or W; The phase change material has an olivine structure, and the chemical formula of the phase change material is LiA ｖ B ｗ P.O. ４ where v+w=1, A comprises Fe, Co, Mn, Ni, Cr, or V, and B comprises Fe, Co, Mn, Ni, Cr, or V; A positive electrode plate for a battery, characterized in that the strength ratio of crystal orientation (003) / (110) after compression of the positive electrode plate is 10 to 100.

2. The tap density of the ternary material is 2.0 to 2.8 g / cm ３ and the tap density of the phase change material is 0.8 to 1.5 g / cm ３ The positive electrode plate according to claim 1, wherein

3. The positive electrode plate according to claim 1, wherein the D50 of the ternary material is 3.5-5.0 μm, and the particle size D50 of the primary particles of the phase change material is 20-40 nm.

4. 2. The positive electrode plate of claim 1, wherein the ternary material comprises a nickel-cobalt-manganese ternary material or a nickel-cobalt-aluminum ternary material.

5. 2. The positive electrode plate of claim 1, wherein the phase change material comprises lithium iron manganese phosphate, lithium vanadium manganese phosphate, or lithium iron chromium phosphate.

6. A method for producing a positive electrode plate according to any one of claims 1 to 5, comprising a method for producing a positive electrode composite material, the method for producing the positive electrode composite material comprising: placing the ternary material, the phase change material, and the NMP solvent in a mass ratio into a mechanofusion device to fuse them together to form a composite material; and firing the fused composite material at a temperature to obtain the composite cathode material; a particle size D50 of the ternary material is 3.0-6.0 μm, a particle size D50 of the primary particles of the phase change material is 10-50 nm, a mass fraction ratio of the ternary material to the phase change material is 80:20-99.8:0.2, a nano-hardness of the ternary material is 0.001-5 GPa, and a nano-hardness of the phase change material is 0.01-10 GPa.

7. 7. The method according to claim 6, wherein the rotation speed of the mechanofusion device is 4000-7000 r / min, and the fusion time is 10-30 min.

8. 8. The method according to claim 7, wherein the rotation speed of the mechanofusion device is 4500-6500 r / min, and the fusion time is 15-25 min.

9. 7. The method according to claim 6, wherein the composite material is calcined at a temperature of 80 to 120°C and for a time of 0.5 to 2.5 hours.

10. 10. The method according to claim 9, wherein the composite material is baked at a temperature of 95-105°C and for a time of 1-2 hours.

11. A method for producing a positive electrode plate according to any one of claims 1 to 5, Adding PVDF having an F-containing group and / or a carboxyl group, an ester group, or an amino group in the polymer chain to a certain amount of NMP solvent to form a PVDF solution; adding a certain amount of conductive material to the PVDF solution and stirring to form a slurry; After a certain period of time, adding the composite cathode material to the slurry and stirring thoroughly to obtain a final slurry; applying the final slurry to a current collector, followed by high-temperature firing to remove the NMP solvent in the slurry, and rolling and slicing the slurry to obtain a positive electrode plate.

12. 12. The method of claim 11, further comprising adding an amount of lithium carbonate to the slurry prior to obtaining the final slurry.

13. A battery comprising the positive electrode plate according to claim 1, a negative electrode plate, and a separator disposed between the positive electrode plate and the negative electrode plate.

Images