Positive electrode material and preparation method thereof, secondary battery and electric device
Through the interlayer stacking theory and particle size distribution optimization, positive electrode materials with high stacking efficiency are prepared, which solves the problem of increasing the compaction density of electrode materials and achieves an increase in battery energy density.
Patent Information
- Application Number
- CN202510805607.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-06-17
- Publication Date
- 2025-09-16
AI Technical Summary
现有技术中，电极材料的压实密度提升难以提高，且传统方法周期长，缺少对粒度分布的考量。
By establishing an apparent volume expression based on the interlayer stacking theory, the particle size distribution curve is obtained by peak fitting, the expected mixing mass ratio of the positive electrode is optimized, and a positive electrode material with high stacking efficiency is prepared.
The compaction density of the positive electrode material has been increased to 3.8g/cm3~3.98g/cm3, improving the energy density and performance of the battery.
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Figure CN120646924A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a positive electrode material and a preparation method thereof, a secondary battery, and an electrical device. Background Art
[0002] As the core energy carrier of modern society, the energy density of batteries directly determines the device's endurance, integration rate and application expansion capabilities. How to improve the energy density of batteries has always been a key breakthrough direction for improving battery performance.
[0003] Improving the compaction density of electrode materials is one of the important ways to increase the volumetric energy density of batteries. However, the compaction density of electrode materials still needs to be improved. Summary of the Invention
[0004] Based on this, it is necessary to provide a positive electrode material capable of improving the compaction density, a preparation method thereof, a secondary battery, and an electrical device.
[0005] In a first aspect of the present application, a method for preparing a positive electrode material is provided.
[0006] A method for preparing a positive electrode material comprises the following steps:
[0007] Step S1, obtaining multiple groups of target precursor raw materials, wherein the particle size distributions of different target precursor raw materials satisfy different particle size distribution curves; wherein the different particle size distribution curves are obtained by peak fitting of a theoretical stacking curve, and the theoretical stacking curve is obtained by solving the apparent volume expression established according to the interlayer stacking theory for the minimum apparent volume;
[0008] Step S2, using different target precursor raw materials to prepare different positive electrode materials;
[0009] Step S3: mixing the different positive electrode materials and compacting them to obtain a positive electrode material; wherein the mixing mass ratio of the different positive electrode materials is the integral area ratio of the corresponding different particle size distribution curves.
[0010] In some embodiments, the process of solving the minimum apparent volume includes:
[0011] According to the interlayer stacking theory, n narrow size groups are established, and the ratio of the upper limit to the lower limit of the particle size in each narrow size group, as well as the upper limit or lower limit of the particle size of any narrow size group, are determined; wherein the lower limit of the particle size of the next narrow size group is the same as the upper limit of the particle size of the previous narrow size group, and n≥2.
[0012] In some embodiments, the ratio is 2.24;
[0013] The upper limit of the particle size of the first narrow size group is 1.79 μm;
[0014] The lower limit of the particle size of the nth narrow size group is 20.14 μm.
[0015] In some embodiments, the theoretical stacking curve is subjected to a secondary peak fitting to obtain the following two different particle size distribution curves:
[0016]
[0017]
[0018] Where y1 and y2 represent volume percentages; x is the particle size in μm.
[0019] In some embodiments, the theoretical stacking curve is subjected to three peak fittings to obtain the following three different particle size distribution curves:
[0020]
[0021]
[0022]
[0023] Where y1, y2 and y3 represent volume percentages; x is the particle size in μm.
[0024] In some embodiments, the steps of preparing the positive electrode include:
[0025] The different target precursor raw materials are mixed with lithium salt and dopant respectively and calcined to obtain primary materials corresponding to the different target precursor raw materials; the different primary materials are mixed with coating agent respectively and sintered to obtain the positive electrode materials corresponding to the different target precursor raw materials.
[0026] In some embodiments, the calcination process comprises: heating to 650°C to 1000°C at a heating rate of 5°C / min to 10°C / min, and keeping the temperature for 6h to 15h; and / or
[0027] The sintering process includes: heating to 300° C. to 700° C. at a heating rate of 5° C. / min to 10° C. / min, and keeping the temperature for 4 hours to 10 hours.
[0028] In a second aspect of the present application, a positive electrode material prepared by the above-mentioned method for preparing the positive electrode material is provided.
[0029] In a third aspect of the present application, a secondary battery comprising the above-mentioned positive electrode material is provided.
[0030] In a fourth aspect of the present application, an electrical device including the above-mentioned secondary battery is provided.
[0031] The preparation method of the above-mentioned positive electrode material obtains the theoretical stacking curve corresponding to high stacking efficiency by solving the apparent volume minimum value of the apparent volume expression established based on the interlayer stacking theory; then, by peak fitting the theoretical stacking curve, it is converted into a particle size distribution curve combination that conforms to the log-normal distribution form; and further, the target precursor raw material corresponds to the obtained particle size distribution curve, and the expected mixing mass ratio of the obtained positive electrode corresponds to the integral area ratio of the particle size distribution curve, thereby optimizing and improving the compaction density of the obtained positive electrode material from the level of particle size distribution. BRIEF DESCRIPTION OF THE DRAWINGS
[0032] To more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.
[0033] Figure 1 The lower cumulative particle size distribution curve and the frequency particle size distribution curve obtained in Example 1 are shown.
[0034] Figure 2 This is a schematic diagram of the peak fitting results obtained in Example 1.
[0035] Figure 3 This is a schematic diagram of the peak fitting results obtained in Example 2. DETAILED DESCRIPTION
[0036] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar modifications without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.
[0037] In the description of this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise specifically defined. In this application, "at least one" means more than one, such as one, two, or more than two. "Multiple" or "several" means at least two, such as two, three, etc.
[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.
[0039] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.
[0040] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
[0041] In this application, “above” or “below” includes the number itself. For example, “1 below” includes 1.
[0042] Unless otherwise specified, the temperature parameters in this application allow for both constant temperature treatment and temperature fluctuations within a certain temperature range. It should be understood that the constant temperature treatment allows for temperature fluctuations within the accuracy range of instrument control. Fluctuations within ranges such as ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are permitted.
[0043] As the core energy carrier of modern society, the energy density of batteries directly determines the device's endurance, integration rate and application expansion capabilities. How to improve the energy density of batteries has always been a key breakthrough direction for improving battery performance.
[0044] Currently, the main method for increasing the compaction density of positive electrode materials is to mix raw materials of different particle sizes multiple times at various mass ratios, repeating this experiment to obtain a product with a higher compaction density and the corresponding raw material mass ratio. This method has inherent limitations due to its long cycle time and only considers the average particle size of the raw materials, ignoring the particle size distribution.
[0045] Based on this, the first aspect of the present application provides a preparation method for a positive electrode material with a higher compaction density taking into account the particle size distribution.
[0046] The preparation method of the positive electrode material comprises the following steps:
[0047] Step S1, obtaining multiple groups of target precursor raw materials, wherein the particle size distributions of different target precursor raw materials satisfy different particle size distribution curves; wherein the different particle size distribution curves are obtained by peak fitting of a theoretical stacking curve, and the theoretical stacking curve is obtained by solving the apparent volume expression established according to the interlayer stacking theory for the minimum apparent volume;
[0048] Step S2, using different target precursor raw materials to prepare different cathode materials;
[0049] Step S3: mixing different positive electrode materials and compacting them to obtain positive electrode materials; wherein the mixing mass ratio of the different positive electrode materials is the integral area ratio of their corresponding different particle size distribution curves.
[0050] The above-mentioned preparation method of the positive electrode material corresponds the particle size distribution of the target precursor raw material to the particle size distribution curve obtained by peak decomposition of the theoretical stacking curve, and corresponds the obtained positive electrode expected mixing mass ratio to the integral area ratio of the particle size distribution curve, thereby obtaining a combination of positive electrode expectations corresponding to a higher stacking efficiency. By taking the particle size distribution of each material into account, the compaction density of the positive electrode material is effectively improved.
[0051] Exemplarily, the process of establishing an apparent volume expression based on the interlayer packing theory includes:
[0052] Set up n narrow size groups g i (i=1~n, n≥2), narrow size group g i The ratio of the upper and lower limits of particle size is a constant value b, and the narrow particle size group g i The lower limit of particle size is equal to the narrow size group g i-1 The upper limit of granularity;
[0053] The narrow size group g i The interlayer stacking is performed to form the first stacking group G1 corresponding to the odd narrow particle group and the second stacking group G2 corresponding to the even narrow particle group; the specific method of interlayer stacking is: mix g1 with g3 of the interlayer, and further mix the mixed g3' with g5, and so on to the last odd group g o (o=n or o=n-1), forming the first stacking group G1 corresponding to the odd narrow particle size group. Similarly, mix g2 with the interlayer g4, and then mix the mixed g4' with g6, and so on to the last even group g e(e=n-1 or e=n), forming the second stacking group G2 corresponding to the even-numbered narrow particle size group.
[0054] For example, let V i Narrow size group g i Particle volume, V vi Narrow size group g i Void volume, V ai Narrow size group g i Apparent volume. Narrow size group g i The apparent volume V ai It can be expressed by the following formula:
[0055]
[0056] Furthermore, V i and V vi The sum of is V ai , through conversion, we can obtain the following relationship:
[0057]
[0058] It can be understood that the sum of the apparent volumes of G1 and G2 is the sum of the apparent volumes after stacking V a , when the void volume is equal to the particle volume, the apparent volume V a The expression of is formula (1), which is:
[0059]
[0060] In formula (1):
[0061]
[0062]
[0063] Among them, ε i Narrow size group g i The void ratio, V i Narrow size group g i The particle volume. And, due to V i 、V vi 、V ai and ε iThere is a conversion relationship between them. This expression can also be replaced by other equivalent forms. Determining two of them can convert to other values. k and j correspond to the number of odd and even numbers in the number n, respectively. For example, if n=10, then k=5 (the 5 odd numbers are 1, 3, 5, 7, 9), j=5 (the 5 even numbers are 2, 4, 6, 8, 10); if n=11, then k=6 (the 6 odd numbers are 1, 3, 5, 7, 9, 11), j=5 (the 5 even numbers are 2, 4, 6, 8, 10).
[0064] In some embodiments, the process of finding the minimum apparent volume includes:
[0065] According to the interlayer accumulation theory, n narrow size groups are established, and the ratio of the upper limit to the lower limit of the particle size in each narrow size group, as well as the upper limit or lower limit of the particle size of any narrow size group, are determined; wherein, the lower limit of the particle size of the next narrow size group is the same as the upper limit of the particle size of the previous narrow size group, and n≥2.
[0066] In some embodiments, the ratio of the upper limit of particle size to the lower limit of particle size in each narrow size group is b, and satisfies: b≥√5.
[0067] In some embodiments, the ratio b is ≤ 2.44.
[0068] In some embodiments, considering the particle size of common electrode materials and combining theoretical errors, the narrow particle size group g i The ratio of the upper limit of particle size to the lower limit of particle size may be, but is not limited to, √5, 2.24, 2.3, 2.34, 2.4, 2.44 or other values within the range of √5 to 2.44.
[0069] In some embodiments, to obtain electrode materials with better electrical properties, the target precursor particles have a D10 of ≥ 2 μm and a D90 of ≤ 20 μm. Optionally, the upper limit of the particle size of the first narrow size group is set to be ≤ 2 μm, and the lower limit of the particle size of the nth narrow size group is set to be ≥ 20 μm, so that the above particle size constraints can be converted into constraints for the apparent volume expression.
[0070] In some embodiments, considering the actual state of the accumulation of granular materials, ε i ≥0.3.
[0071] In some embodiments, the ratio b is 2.24;
[0072] The upper limit of the particle size of the first narrow size group is 1.79 μm;
[0073] The lower limit of the particle size of the nth narrow size group is 20.14 μm.
[0074] In some embodiments, the theoretical stacking curve is subjected to secondary peak splitting to obtain the following two different particle size distribution curves:
[0075]
[0076]
[0077] Where y1 and y2 represent volume percentages; x is the particle size in μm.
[0078] In some embodiments, the theoretical stacking curve is split three times to obtain the following three different particle size distribution curves:
[0079]
[0080]
[0081]
[0082] Where y1, y2 and y3 represent volume percentages; x is the particle size in μm.
[0083] The theoretical stacking curve corresponds to the particle size distribution at the apparent volume minimum, and this particle size distribution generally does not conform to the lognormal distribution model. The above method obtains multiple particle size distribution curves corresponding to the theoretical stacking curve by performing peak fitting on the theoretical stacking curve. It can be understood that the parameters obtained by solving equation (1) directly correspond to the lower cumulative particle size distribution curve. By differentiating the lower cumulative particle size distribution curve, the frequency particle size distribution curve can be obtained.
[0084] In some embodiments, the particle size distribution of the target precursor material conforms to a lognormal distribution, and the correlation coefficient R squared of the fit is greater than 0.98. Alternatively, the correlation coefficient R squared is greater than 0.99. The target precursor material having a particle size distribution conforming to a lognormal distribution can be prepared using existing techniques.
[0085] In some embodiments, the particle size distribution of the target precursor material has a mean absolute error of less than 10% from the corresponding particle size distribution curve.
[0086] In some embodiments, the average absolute error between the expected particle size distribution of the positive electrode and the corresponding particle size distribution curve is less than 10%.
[0087] Unless otherwise specified, the mean absolute error is calculated based on D10, D20, D30, D40, D50, D60, D70, D80, and D90.
[0088] In some embodiments, Matlab is used to solve the apparent volume V of equation (1)a The minimum value of .
[0089] In some embodiments, the steps of preparing the positive electrode include:
[0090] Different target precursor raw materials are mixed with lithium salt and dopant respectively and calcined to obtain primary materials corresponding to different target precursor raw materials; different primary materials are mixed with coating agent respectively and sintered to obtain positive electrode materials corresponding to different target precursor raw materials.
[0091] In some embodiments, the target precursor material includes a precursor material of an NCA material or a precursor material of an NCM material.
[0092] In some embodiments, the lithium salt includes one or more of lithium carbonate or lithium hydroxide.
[0093] In some embodiments, the dopant includes one or more of simple oxides of magnesium, aluminum, titanium, and zirconium and simple hydroxides thereof, or composite oxides of two or more of magnesium, aluminum, titanium, and zirconium and composite hydroxides thereof.
[0094] In some embodiments, the coating additive includes one or more oxides of magnesium, aluminum, tungsten, zirconium, etc., and LATP.
[0095] In some embodiments, the ratio of the molar amount of lithium ions in the lithium salt to the total molar amount of transition metals in the precursor raw material is (1.02-1.06):1.
[0096] In some embodiments, the calcination process includes: heating the temperature to 650° C. to 1000° C. at a heating rate of 5° C. / min to 10° C. / min, and keeping the temperature for 6 h to 15 h.
[0097] In some embodiments, the sintering process includes: heating the temperature to 300° C. to 700° C. at a heating rate of 5° C. / min to 10° C. / min, and keeping the temperature for 4 h to 10 h.
[0098] In some embodiments, the steps of preparing a single-crystal positive electrode material include: mixing a target precursor raw material with D50 < 6 μm with a lithium salt and a dopant, heating the mixture to 750°C ~ 1000°C at a heating rate of 5°C / min ~ 10°C / min, and calcining the mixture for 8h ~ 15h to obtain a primary material; heating the mixture to 300°C ~ 700°C at a heating rate of 5°C / min ~ 10°C / min, and sintering the mixture for 4h ~ 10h to obtain a single-crystal positive electrode material.
[0099] In some embodiments, the steps of preparing an agglomerated positive electrode material include: mixing a target precursor raw material with D50>5μm with a lithium salt and a dopant, heating the material to 650℃~850℃ at a heating rate of 5℃ / min~10℃ / min, and calcining the material for 8h~12h to obtain a primary material; heating the material to 300℃~700℃ at a heating rate of 5℃ / min~10℃ / min, and sintering the material for 4h~10h to obtain an agglomerated positive electrode material.
[0100] In a second aspect of the present application, a positive electrode material prepared by the above-mentioned method for preparing the positive electrode material is provided.
[0101] In some embodiments, the positive electrode material has a compacted density of 3.1 g / cm 3 ~3.98g / cm 3 .
[0102] In some embodiments, for precursor materials with D10 ≥ 2 μm and D90 ≤ 20 μm, the compacted density of the cathode material can be 3.8 g / cm 3 ~3.98g / cm 3 Precursor materials with D10 ≥ 2 μm and D90 ≤ 20 μm usually have good electrical properties, but the compaction density of the cathode materials obtained from them is usually difficult to reach 3.8 g / cm 3 The above method can be used to prepare a compacted density of 3.8g / cm 3 ~3.98g / cm 3 positive electrode material.
[0103] In a third aspect of the present application, a secondary battery comprising the above-mentioned positive electrode material is provided. The secondary battery comprises a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the positive electrode sheet comprises the above-mentioned positive electrode material.
[0104] In a fourth aspect, the present application provides an electrical device comprising the aforementioned secondary battery. The electrical device may include a mobile device and an electric vehicle. The mobile device may be a mobile phone, a laptop computer, etc.; the electric vehicle may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
[0105] The present application is further described in detail below with reference to specific embodiments.
[0106] In the following specific examples and comparative examples, the raw materials used, unless otherwise specified, are all commercially available products; the instruments used, unless otherwise specified, are all commercially available products; and the processes used, unless otherwise specified, are all routinely selected by those skilled in the art.
[0107] Example 1
[0108] This embodiment provides a high compaction density NCM9055 positive electrode material.
[0109] The preparation method of the high compaction density NCM9055 positive electrode material of this embodiment is as follows:
[0110] Step S1, obtaining multiple groups of target precursor raw materials, wherein the particle size distributions of different target precursor raw materials satisfy different particle size distribution curves; wherein the different particle size distribution curves are obtained by peak fitting of a theoretical stacking curve, and the theoretical stacking curve is obtained by solving the apparent volume expression established according to the interlayer stacking theory for the minimum apparent volume;
[0111] Among them, 5 narrow size groups were established according to the interlayer accumulation theory. The ratio of the upper limit to the lower limit of each narrow size group was 2.24. i The particle size ranges of (i=1~5) are 0.8~1.79, 1.79~4.01, 4.01~8.99, 8.99~20.14, and 20.14~45.12 (the unit of particle size is μm). The expressions between the parameters of each narrow particle size group are shown in Table 1. The apparent volume V a The expression of V a =V a4 +V a5 .
[0112] Table 1
[0113]
[0114] Use Matlab to solve V a The minimum value (script see the end of this example), and set V1+V2+V3+V4+V5=100, set V1<10 and V5<10 from D10≥2μm, D90≤20μm, set 1≥ε i ≥0.3. Solve for V a Minimum value, get V a The particle volume, apparent volume, and void volume are further obtained, as shown in Table 2.
[0115] Table 2
[0116]
[0117] Based on the data in Table 2, the corresponding lower cumulative particle size distribution curve is obtained. The theoretical stacking curve (frequency particle size distribution curve) is obtained by differentiating the lower cumulative particle size distribution curve. Figure 1 , Figure 1: The lower cumulative particle size distribution curve and the theoretical stacking curve obtained in this example.
[0118] The theoretical stacking curve is fitted with peaks to obtain a particle size distribution curve that conforms to the logarithmic normal distribution. Figure 2 and Table 3, Figure 2 This is a schematic diagram of the results based on bimodal peak fitting. Figure 2 The equations of the two corresponding particle size distribution curves are shown in Table 3.
[0119] Table 3
[0120]
[0121] Step S2, using different target precursor raw materials to prepare different cathode materials;
[0122] For positive electrode A (satisfying curve X_1 in Table 3): the precursor raw materials, lithium salt and dopant are mixed, heated to 900℃ at a heating rate of 7.5℃ / min and calcined for 10h, crushed to obtain a primary material; then the coating agent is added, the temperature is raised to 500℃ at a heating rate of 7.5℃ / min and sintered for 8h to obtain a single crystal positive electrode A. Among them, the precursor raw materials are Ni 0.6 Co 0.2 Mn 0.2 (OH)2, its particle size distribution conforms to the particle size curve X_1 of the small particles calculated above, and the average absolute error between the particle size distribution tested by Malvern particle size analyzer and the particle size curve X_1 is 3.92%; the lithium salt is lithium carbonate, the dopant is the oxide of magnesium, aluminum, titanium, and zirconium, and the coating agent is the oxide of magnesium, aluminum, tungsten, and zirconium.
[0123] For positive electrode prospect B (satisfying curve X_2 in Table 3): the precursor raw materials, lithium salt and dopant are mixed, heated to 750℃ at a heating rate of 7.5℃ / min and calcined for 10h, crushed to obtain a primary material; then the coating agent is added, the temperature is raised to 500℃ at a heating rate of 7.5℃ / min and sintered for 8h to obtain agglomerated positive electrode prospect A. Among them, the precursor raw materials are Ni 0.9 Co 0.05 Mn 0.05 (OH)2, its particle size distribution conforms to the large particle size curve X_2 calculated above, and the average absolute error between the particle size distribution tested by Malvern particle size analyzer and the particle size curve X_2 is 3.71%; the lithium salt is lithium hydroxide, the dopant is magnesium, aluminum, and zirconium oxides, and the coating agent is LATP.
[0124] Step S3: Weigh and mix the positive electrode material A and the positive electrode material B prepared above according to the corresponding integrated area ratio of 31:69, and compact them to obtain an NCM9055 positive electrode material with a high compaction density.
[0125] The matlab script used in this example is:
[0126] fun = @(x)x(7) / (1-x(2)) / x(4)+x(6) / (1-x(1)) / x(3) / x(5);
[0127] x0 = [0.3,0.4,0.4,0.4,0.4,5,5];
[0128] A = [];
[0129] b = [];
[0130] Aeq = [];
[0131] beq = [];
[0132] lb = [0.3,0.3,0.3,0.3,0.3,0,0];
[0133] ub = [1,1,1,1,1,10,100];
[0134] function [c,ceq] = constr(x)
[0135] c(1) = -x(6) / (1-x(1))×(1-x(3)) / x(3);
[0136] c(2) = -x(7) / (1-x(2))×(1-x(4)) / x(4);
[0137] c(3) = -x(6) / (1-x(1)) / x(3)×(1-x(5)) / x(5);
[0138] c(4) = x(6) / (1-x(1))×(1-x(3)) / x(3)-100;
[0139] c(5) = x(7) / (1-x(2))×(1-x(4)) / x(4)-100;
[0140] c(6) = x(6) / (1-x(1)) / x(3)×(1-x(5)) / x(5)-100;
[0141] c(7) = 90-x(6)-x(7)-x(6) / (1-x(1))×(1-x(3)) / x(3)-x(7) / (1-x(2))×(1-x(4)) / x(4);
[0142] ceq=x(6)+x(7)+x(6) / (1-x(1))×(1-x(3)) / x(3)+x(7) / (1-x(2))×(1-x(4)) / x(4)+x(6) / (1-x(1)) / x(3)×(1-x(5)) / x(5)-100;
[0143] end;
[0144] nonlcon = @constr;
[0145] [x,fval,exitflag,output] = fmincon(fun,x0,A,b,Aeq,beq,lb,ub,nonlcon);
[0146] Example 2
[0147] This embodiment provides a high compaction density NCM9055 positive electrode material.
[0148] The preparation method of the high compaction density NCM9055 positive electrode material in this embodiment is different from that in Example 1 in that: the theoretical stacking curve is subjected to three-peak peak fitting, and the particle size distribution curve obtained in this embodiment is shown in FIG. Figure 3 and Table 4, Figure 3 This is a schematic diagram of the results based on three-peak fitting. Figure 3 The equations of the corresponding three particle size distribution curves are shown in Table 4;
[0149] For the positive electrode A (satisfying the curve Y_1 in Table 4): the precursor material is Ni 0.5 Co 0.2 Mn 0.3 (OH)2, its particle size distribution conforms to the particle size curve Y_1 in Table 4, with an average absolute error of 3.89%; the lithium salt is lithium carbonate, the dopant is magnesium, aluminum, titanium, and zirconium oxide, and the coating agent is magnesium, aluminum, tungsten, and zirconium oxide.
[0150] For the positive electrode B (satisfying curve Y_2 in Table 4): the precursor material is Ni 0.6 Co 0.2 Mn 0.2 (OH)2, its particle size distribution conforms to the particle size curve Y_2 in Table 4, with an average absolute error of 3.70%; the lithium salt is lithium carbonate, the dopant is magnesium, aluminum, titanium, and zirconium oxide, and the coating agent is magnesium, aluminum, tungsten, and zirconium oxide.
[0151] For the positive electrode C (satisfying curve Y_3 in Table 4): the precursor material is Ni 0.9 Co 0.05 Mn 0.05(OH)2, its particle size distribution conforms to the particle size curve Y_3 in Table 4, with an average absolute error of 3.56%; the lithium salt is lithium hydroxide, the dopant is the oxides of magnesium, aluminum, and zirconium, and the coating agent is the fast ion conductor of LATP.
[0152] The positive electrode material A, positive electrode material B and positive electrode material C prepared above were weighed and mixed in a mass ratio of 2.6:13.7:83.7, and compacted to obtain an NCM9055 positive electrode material with a high compaction density.
[0153] Table 4
[0154]
[0155] Comparative Example 1
[0156] This comparative example provides a NCM9055 positive electrode material with a high compaction density.
[0157] The positive electrode material A and positive electrode material B used in the NCM9055 positive electrode material of this comparative example are the same as those in Example 1. The preparation method of the positive electrode material is basically the same as that in Example 1, except that the mass ratio of positive electrode material A to positive electrode material B is 50:50.
[0158] Comparative Example 2
[0159] This comparative example provides a NCM9055 positive electrode material with a high compaction density.
[0160] The positive electrode material A and positive electrode material B used in the NCM9055 positive electrode material of this comparative example are the same as those in Example 1. The preparation method of the positive electrode material is basically the same as that in Example 1, except that the mass ratio of positive electrode material A to positive electrode material B is 15:85.
[0161] Comparative Example 3
[0162] This comparative example provides a NCM9055 positive electrode material with a high compaction density.
[0163] The positive electrode material A, positive electrode material B, and positive electrode material C used in the NCM9055 positive electrode material of this comparative example are the same as those in Example 2. The preparation method of the positive electrode material is basically the same as that in Example 2, except that the positive electrode material A, positive electrode material B, and positive electrode material C are weighed and mixed in a mass ratio of 5:20:75, and compacted to obtain an NCM9055 positive electrode material with a high compaction density.
[0164] Comparative Example 4
[0165] This comparative example provides a NCM9055 positive electrode material with a high compaction density.
[0166] The positive electrode material A, positive electrode material B, and positive electrode material C used in the NCM9055 positive electrode material of this comparative example are the same as those in Example 2. The preparation method of the positive electrode material is basically the same as that in Example 2, except that the positive electrode material A, positive electrode material B, and positive electrode material C are weighed and mixed in a mass ratio of 10:5:85, and compacted to obtain an NCM9055 positive electrode material with a high compaction density.
[0167] Comparative Example 5
[0168] This comparative example provides an NCM9055 positive electrode material.
[0169] The positive electrode material A used in the NCM9055 positive electrode material of this comparative example is the same as that in Example 1. The difference in the preparation method of the positive electrode material is that the positive electrode material A and the positive electrode material B are mixed and compacted at a mass ratio of 100:0 (without adding the positive electrode material B) to obtain the NCM9055 positive electrode material.
[0170] Comparative Example 6
[0171] This comparative example provides an NCM9055 positive electrode material.
[0172] The positive electrode material B used in the NCM9055 positive electrode material of this comparative example is the same as that in Example 1. The difference in the preparation method of the positive electrode material is that the positive electrode material B and the positive electrode material A are mixed and compacted at a mass ratio of 100:0 (without adding the positive electrode material A) to obtain the NCM9055 positive electrode material.
[0173] Test Case
[0174] The compaction density and stacking efficiency of the positive electrode materials of the embodiment and the comparative example were measured and calculated. The performance results are shown in Table 5.
[0175] Table 5
[0176]
[0177] As can be seen from Table 5, the positive electrode materials obtained in Examples 1 and 2 have a significantly improved compaction density compared to the positive electrode materials of Comparative Examples 1 to 4 obtained by mixing with other mass ratios and Comparative Examples 5 to 6 using a single particle size. In addition, the calculated stacking efficiency is consistent with the trend of the experimentally measured compaction density, further indicating that the use of stacking efficiency to evaluate the compaction density of the positive electrode material in this application is reliable. In summary, it can be seen that the preparation method of the positive electrode material of this application optimizes the ratio of the particle size distribution of different particles by taking the particle size distribution into consideration, which helps to obtain a positive electrode material with a higher compaction density.
[0178] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.
[0179] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present application, all of which fall within the scope of protection of the present application. Therefore, the scope of protection of the present invention should be based on the appended claims, and the specification may be used to interpret the content of the claims.
Claims
1. A method for preparing a positive electrode material, characterized in that: The steps include: Step S1, obtaining multiple groups of target precursor raw materials, wherein the particle size distributions of different target precursor raw materials satisfy different particle size distribution curves, wherein the different particle size distribution curves are obtained by peak fitting of a theoretical stacking curve, and the theoretical stacking curve is obtained by solving the apparent volume expression established according to the interlayer stacking theory for the minimum apparent volume; Step S2, using different target precursor raw materials to prepare different positive electrode materials; Step S3: mixing the different positive electrode materials and compacting them to obtain positive electrode materials, wherein the mixing mass ratio of the different positive electrode materials is the integral area ratio of the corresponding different particle size distribution curves.
2. The method for preparing the positive electrode material according to claim 1, wherein: The process of solving the minimum apparent volume includes: According to the interlayer stacking theory, n narrow size groups are established, and the ratio of the upper limit to the lower limit of the particle size in each narrow size group, as well as the upper limit or lower limit of the particle size of any narrow size group, are determined; wherein the lower limit of the particle size of the next narrow size group is the same as the upper limit of the particle size of the previous narrow size group, and n≥2.
3. The method for preparing the positive electrode material according to claim 2, wherein: The ratio of the upper limit of particle size to the lower limit of particle size in each narrow size group is the same, and the ratio is 2.24; The upper limit of the particle size of the first narrow size group is 1.79 μm; The lower limit of the particle size of the nth narrow size group is 20.14 μm.
4. The method for preparing the positive electrode material according to claim 3, wherein: The theoretical accumulation curve was subjected to secondary peak fitting to obtain the following two different particle size distribution curves: Where y1 and y2 represent volume percentages; x is the particle size in μm.
5. The method for preparing the positive electrode material according to claim 3, wherein: The theoretical accumulation curve was subjected to three peak fittings to obtain the following three different particle size distribution curves: Where y1, y2 and y3 represent volume percentages; x is the particle size in μm.
6. The method for preparing a positive electrode material according to any one of claims 1 to 5, wherein: The steps of preparing the positive electrode include: mixing different target precursor raw materials with lithium salt and dopant respectively and calcining them to obtain primary materials corresponding to different target precursor raw materials; The different primary materials are mixed with coating agents respectively and sintered to obtain the positive electrode materials corresponding to the different target precursor raw materials.
7. The method for preparing the positive electrode material according to claim 6, wherein: The calcination process comprises: heating to 650°C to 1000°C at a heating rate of 5°C / min to 10°C / min, and keeping the temperature for 6h to 15h; and / or The sintering process includes: heating to 300° C. to 700° C. at a heating rate of 5° C. / min to 10° C. / min, and keeping the temperature for 4 hours to 10 hours.
8. A positive electrode material, characterized in that The positive electrode material is prepared by the method for preparing the positive electrode material according to any one of claims 1 to 7.
9. A secondary battery, characterized in that: Comprising the positive electrode material according to claim 8.
10. An electrical device, characterized in that: The secondary battery according to claim 9 is included.