Positive electrode material and preparation method thereof, lithium ion battery and electric device

Abstract

The present application belongs to the field of battery technology and specifically relates to a positive electrode material and a preparation method thereof, a lithium-ion battery and an electric device. The positive electrode material includes a composition shown in Formula 1, Li a Fe b M c (PO4) d Q e In formula 1, 0.95≤ a ≤1.10,0.7≤ b ≤1,0≤ c ≤0.5,0.95≤ d ≤1.10,0≤ e ≤0.05, M includes at least one of Ti, Mg, Zn, Cu, Sr, Al, Zr, Y, Co, W, Ca, Nb, Sn, Sb, Mo, V, B, and Na, and Q includes at least one of Si, S, F, Cl, Br, and I; and meets the following requirements: 80nm≤L 10 ≤200nm; 150nm≤L 50 ≤500nm; 400nm≤L 90 ≤1000nm; 1

Description

Technical Field

[0001] The present application belongs to the field of battery technology, and specifically relates to positive electrode materials and preparation methods thereof, lithium-ion batteries and electrical devices. Background Art

[0002] In recent years, as countries around the world have introduced policies to support the development of new energy vehicles and energy storage industries, lithium iron phosphate (LFP) has continued to expand its market share due to its advantages such as high safety, long life and low cost. However, with the continuous development of policies and markets, the existing lithium iron phosphate (compression density is generally 2.5g / cm 3 Around) can no longer meet the higher requirements of new energy vehicle endurance and energy efficiency of energy storage systems, so the development of high-pressure compacted lithium iron phosphate has become one of the current hot directions.

[0003] At present, some researchers have adopted the sand grinding particle size grading method to achieve this. This method mainly grinds the raw materials into different particle sizes and then mixes them in a certain proportion to achieve the grading effect. However, due to the difference in temperature for the full reaction of large and small particles, when the large particles reach the appropriate temperature, the small particles are overburned, resulting in the melting and growth of the small particles, which makes it impossible to effectively improve the grading effect and compaction density. In addition, the preparation process is long and complicated, which is not conducive to large-scale production. At the same time, the increase in compaction density may also have a negative impact on the electrochemical performance of the battery. Therefore, how to improve the compaction density of LFP while ensuring the existing electrochemical performance has received continuous attention from those skilled in the art. Summary of the Invention

[0004] The present application aims to solve at least one of the technical problems in the related art to a certain extent. To this end, the present application proposes a high compaction density positive electrode material with better electrochemical performance.

[0005] In a first aspect of the present application, a positive electrode material is provided. According to an embodiment of the present application, the positive electrode material comprises a composition shown in Formula 1,

[0006] Li a Fe b M c (PO4) d Q e Formula 1

[0007] In formula 1, 0.95≤ a ≤1.10,0.7≤ b ≤1,0≤ c ≤0.5,0.95≤ d ≤1.10,0≤ e≤0.05, M includes at least one of Ti, Mg, Zn, Cu, Sr, Al, Zr, Y, Co, W, Ca, Nb, Sn, Sb, Mo, V, B, and Na, and Q includes at least one of Si, S, F, Cl, Br, and I;

[0008] The positive electrode material satisfies:

[0009] 80nm≤L 10 ≤200nm;

[0010] 150nm≤L 50 ≤500nm;

[0011] 400nm≤L 90 ≤1000nm;

[0012] 1 <S<2;

[0013] Among them, L 10 , L 50 , L 90 is the sub-grain size corresponding to when the cumulative volume percentage of the sub-grain size Ln of the positive electrode material reaches 10%, 50% and 90% respectively, and S is the skewness coefficient of the sub-grain size sample of the positive electrode material obtained by the third-order dynamic moment method.

[0014] The positive electrode material of the present application meets the above conditions, and its compaction density and electrochemical specific capacity are both good, thereby effectively improving the energy density and electrochemical performance of lithium-ion batteries using the positive electrode material.

[0015] According to an embodiment of the present application, the positive electrode material satisfies at least one of the following conditions:

[0016] 100nm≤L 10 ≤180nm;

[0017] 200nm≤L 50 ≤400nm;

[0018] 500nm≤L 90 ≤900nm;

[0019] 1.2 <S<1.9。

[0020] According to the embodiment of the present application, 1.3≤(L 90 -L 10 ) / L 50 ≤2.2; preferably 1.5≤(L 90 -L 10 ) / L 50 ≤2.0.

[0021] According to an embodiment of the present application, the kurtosis coefficient K of the sub-grain size of the positive electrode material obtained by the fourth-order moment method satisfies: 4 < K < 8; preferably 4.5 < K < 7.5.

[0022] According to an embodiment of the present application, the sub-grain size distribution curve of the positive electrode material includes only one peak.

[0023] According to an embodiment of the present application, the unit cell volume of the positive electrode material is 287.0 Å 3 ~293.0 Å 3 , preferably 288.000 Å 3 ~292.000 Å 3 .

[0024] According to an embodiment of the present application, based on the total weight of the positive electrode material, the carbon content in the positive electrode material is 0.7 wt% to 2 wt%, preferably 1 wt% to 1.5 wt%.

[0025] According to an embodiment of the present application, the tap density of the positive electrode material is 2.6 g / cm 3 ~2.9 g / cm 3 .

[0026] In a second aspect of the present application, there is provided a method for preparing the positive electrode material described above. According to an embodiment of the present application, the method includes spray-drying a first mixture to obtain a spray-dried material; subjecting the spray-dried material to a first sintering to obtain a lithium iron phosphate precursor; subjecting a second mixture containing the lithium iron phosphate precursor to a second sintering to obtain the positive electrode material, wherein the first mixture includes iron phosphate, a lithium source, and a carbon source; the first mixture includes the iron phosphate, the lithium source, the carbon source, and an M 1 source; the first mixture includes the iron phosphate, the lithium source, the carbon source, and the M 1 source and a Q 1 source; or the first mixture includes the iron phosphate, the lithium source, the carbon source, and the Q 1 source. The second mixture includes the lithium iron phosphate precursor and an M 2 source; the second mixture includes the lithium iron phosphate precursor, the M 2 source and a Q 2 source; or the lithium iron phosphate precursor and the Q 2 source. The M in the M 1 source and the M in the M 1 element and the M in the M 2 source and the M in the M 2 element each independently includes at least one of Ti, Mg, Zn, Cu, Sr, Al, Zr, Y, Co, W, Ca, Nb, Sn, Sb, Mo, V, B, Na; Q1 Q in the source 1 Elements and Q 2 Q in the source 2 The elements independently include at least one of Si, S, F, Cl, Br, and I. The preparation process of the positive electrode material provided in the present application is simple, the cost is relatively low, and it is suitable for industrialization. The preparation process only requires one grinding and one crushing, and a high-density product can be obtained by dry coating, which is suitable for large-scale production.

[0027] According to an embodiment of the present application, the iron phosphate satisfies at least one of the following conditions:

[0028] The iron-phosphorus molar ratio Fe / P of the ferric phosphate is 0.95-0.98;

[0029] The particle size D of the iron phosphate 50 4μm~20μm;

[0030] The specific surface area of ​​the iron phosphate is 6 m 2 / g~12m 2 / g.

[0031] According to an embodiment of the present application, the method satisfies at least one of the following conditions:

[0032] The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium phosphate and lithium nitrate;

[0033] The M 1 Sources include M 1 At least one of an oxide, hydroxide, carbonate, halide, silicate and sulfate of an element;

[0034] The M 2 Sources include M 2 At least one of an oxide, hydroxide, carbonate, halide, silicate and sulfate of an element;

[0035] The Q 1 Sources include Li and / or M 1 At least one of sulfate, silicate, and halide;

[0036] The Q 2 Sources include Li and / or M 2 At least one of sulfate, silicate, and halide;

[0037] The carbon source includes at least one of glucose, sucrose and an organic polymer.

[0038] According to an embodiment of the present application, spray-drying the first mixture includes:

[0039] mixing the first mixture with a solvent to obtain a dispersion;

[0040] Grinding the dispersion to obtain a grinding slurry;

[0041] The grinding slurry is spray-dried to obtain the spray-dried material.

[0042] According to an embodiment of the present application, the method satisfies at least one of the following conditions:

[0043] The solvent includes deionized water;

[0044] The solid content of the dispersion is ≥35%;

[0045] The particle size of the grinding slurry meets the following requirements: 50 It is 0.1 μm to 0.6 μm, preferably 0.25 μm to 0.5 μm.

[0046] According to an embodiment of the present application, the method satisfies at least one of the following conditions:

[0047] The sintering temperature of the primary sintering is 700°C to 850°C;

[0048] The sintering time of the primary sintering is 6h~16h;

[0049] The sintering temperature of the secondary sintering is 650°C to 800°C;

[0050] The sintering time of the secondary sintering is 4h~20h.

[0051] In a third aspect, the present application provides a lithium-ion battery comprising the cathode material described in the first aspect of the present application or the cathode material prepared by the method of the second aspect. Thus, the lithium-ion battery has a high energy density, excellent electrochemical performance, and excellent cycle stability.

[0052] The fourth aspect of the present application provides an electrical device comprising the lithium-ion battery described in the third aspect of the present application. The electrical device has all the features and advantages of the lithium-ion battery described above, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a scanning electron microscope photograph of the primary crushed material III in Example 1 of the present application.

[0054] Figure 2 This is a scanning electron microscope photograph of the finished lithium iron phosphate positive electrode material in Example 1 of the present application.

[0055] Figure 3 1 is the sub-grain size distribution curve of the positive electrode material in Example 1 and Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0056] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present application, but should not be understood as limiting the present application.

[0057] This application is based on the inventor's discovery and understanding of the following facts and problems:

[0058] With the higher requirements of electric vehicles for endurance and energy storage systems for energy efficiency, how to improve the compaction density of positive electrode materials has become one of the important research directions. However, the current particle grading method, on the one hand, cannot maximize the compaction density, and on the other hand, the preparation process is long and complicated, which is not conducive to large-scale production, and may also have a negative impact on its electrochemical performance. The inventors of this application have found through research that the micromorphology of lithium iron phosphate positive electrode materials is closely related to their capacity and compaction density. By adjusting certain processes, LFP materials with specific micromorphology are prepared, showing a higher compaction density, and the batteries prepared therefrom have a higher energy density.

[0059] In view of this, the present application overcomes the problems in the related art that it is difficult to achieve both the compaction density and electrochemical performance of lithium iron phosphate and the complex process flow for preparing high-compaction samples, and provides a high-compaction, high-electrochemical performance lithium iron phosphate positive electrode material and its preparation method, lithium-ion battery and electrical device.

[0060] In a first aspect of the present application, a positive electrode material is provided. According to an embodiment of the present application, the positive electrode material comprises a composition shown in Formula 1,

[0061] Li a Fe b M c (PO4) d Q e Formula 1

[0062] In formula 1, 0.95≤ a ≤1.10,0.7≤ b ≤1,0≤ c ≤0.5, 0.95≤ d ≤1.10,0≤ e ≤0.05, M includes at least one of Ti, Mg, Zn, Cu, Sr, Al, Zr, Y, Co, W, Ca, Nb, Sn, Sb, Mo, V, B, and Na, and Q includes at least one of F, Cl, Br, I, Si, and S;

[0063] The positive electrode material satisfies:

[0064] 80nm≤L 10≤200nm;

[0065] 150nm≤L 50 ≤500nm;

[0066] 400nm≤L 90 ≤1000nm;

[0067] 1 <S<2;

[0068] Among them, L 10 , L 50 , L 90 is the sub-grain size corresponding to when the cumulative volume percentage of the sub-grain size Ln of the positive electrode material reaches 10%, 50% and 90% respectively, and S is the skewness coefficient of the sub-grain size sample of the positive electrode material obtained by the third-order dynamic moment method.

[0069] The positive electrode material of the present application meets the above conditions, and its compaction density and electrochemical specific capacity are both good, thereby effectively improving the energy density and electrochemical performance of lithium-ion batteries using the positive electrode material.

[0070] It should be noted that the sub-grain size Ln of the positive electrode material is obtained by using the powder X-ray diffraction pattern obtained by using CuKα ray powder X-ray diffraction measurement and the Fundamental Parameter method fitting algorithm to perform size statistics. 50 As a physical quantity that represents the median value of the number distribution, it can represent the size of the sub-grain size. The smaller the sub-grain size, the shorter the migration path of lithium ions in the positive electrode material and the higher the diffusion rate, that is, the positive electrode material has better kinetic performance. However, too small a sub-grain size will lead to a low compaction density of the positive electrode material. This application controls the L 10 , L 50 , L 90 Within the above range, the positive electrode material can achieve a higher compaction density and also have better kinetic performance.

[0071] In some embodiments, L 10 Specifically, it can be 100 nm to 180 nm, for example, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, etc.; L 50 Specifically, it can be 200nm~400nm, for example, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc.; L 50Specifically, it can be 500nm~900nm, for example, it can be 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 750nm, 800nm, 850nm, 900nm, 950nm, 1000nm, etc.

[0072] The dynamic moment method is a method for analyzing and processing data based on the concept of moment (moment) in statistics and probability theory. The dynamic moment method is widely used in statistics, mainly to describe the characteristics of data distribution. The skewness coefficient (or skewness coefficient) S of the subgrain size of the positive electrode material calculated using the dynamic moment method can be used as a characteristic number to measure the deviation of the subgrain size distribution from the normal distribution, and is used to measure the uniformity of the subgrain size of the positive electrode material. The skewness coefficient S measures the symmetry of the data distribution through the third-order central moment. The skewness coefficient formula is: Skewness coefficient S = E[(X-μ) 3 ] / σ 3 ; where E[(X-μ) 3 ] is the third-order central moment, X is the subgrain size of each particle, μ is the mean, and σ is the standard deviation. A skewness coefficient S of 0 indicates a symmetrical distribution; a skewness coefficient S greater than 0 indicates positive skewness; and a skewness coefficient S less than 0 indicates negative skewness. By controlling the skewness coefficient S of the positive electrode material within the above range, the present application can obtain a positive electrode material with a moderate subgrain size, resulting in a higher compaction density and electrochemical performance.

[0073] In some embodiments, the skewness coefficient S may be specifically 1.2 to 1.9, for example, 1.01, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 1.99, etc. Within the above range, a positive electrode material with a moderate subgrain size can be obtained, further improving the compaction density and electrochemical performance of the positive electrode material.

[0074] According to the embodiment of the present application, the sub-grain size distribution K of the positive electrode material 90 Satisfy: 1.3≤K 90 =(L 90 -L 10 ) / L 50 ≤2.2, in some specific embodiments, 1.5≤K 90 =(L 90 -L 10 ) / L 50 ≤2.0. As an example, (L 90 -L 10 ) / L 50 Specifically, it can be 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, etc. Thus, the compaction density and electrochemical performance of the positive electrode material can be further improved.

[0075] K 90 can reflect the uniformity of the distribution of sub - grain sizes. When K 90 is too large or too small, the uniformity of the sub - grain size distribution of the positive electrode material deteriorates, the tap density of the positive electrode material will decrease, and K 90 does not meet the requirements, and the tap density and electrochemical performance of the positive electrode material will decrease.

[0076] According to an embodiment of the present application, the kurtosis coefficient K of the sub - grain size of the positive electrode material obtained by the fourth - order moment method satisfies: 4 < K < 8; in some specific embodiments, 4.5 < K < 7.5. As an example, K can specifically be 4.1, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 7.9, etc.

[0077] The kurtosis coefficient of the sub - grain size of the positive electrode material calculated by the moment method is used as a characteristic number to measure the deviation of the sub - grain size distribution from the normal distribution, and can be used to measure the sharpness of the sub - grain size distribution of the positive electrode material. The formula for the kurtosis coefficient (or kurtosis coefficient) K is: kurtosis coefficient = E[(X - μ) 4 / σ 4 , where E[(X - μ) 4 is the fourth - order central moment, X is the sub - grain size of each particle, μ is the average value, and σ is the standard deviation. A kurtosis coefficient of 3 indicates a normal peak; greater than 3 indicates a sharp peak; less than 3 indicates a flat peak. By controlling the kurtosis coefficient of the positive electrode material within the above range, the tap density and electrochemical performance of the positive electrode material can be further improved.

[0078] According to an embodiment of the present application, the sub - grain size distribution curve of the positive electrode material includes only one peak. Thus, the preparation of the positive electrode material is simpler, without the complex operation of grading multiple positive electrode materials with different particle sizes, and the obtained positive electrode material has a higher tap density.

[0079] According to an embodiment of the present application, the unit cell volume of the positive electrode material is 287.0 Å 3 ~293.0 Å 3 , specifically it can be 288.000 Å 3 ~292.000 Å 3 , for example, it can be 287.0 Å 3 , 288.0 Å 3 , 289.0 Å 3 , 290.0 Å 3 , 291.0 Å 3 , 292.0 Å 3 , 293.0 Å 3 and so on. Within the above range of unit cell volumes, the positive electrode material can be packed more closely, thereby obtaining a higher tap density.

[0080] According to an embodiment of the present application, based on the total weight of the positive electrode material, the carbon content in the positive electrode material is 0.7wt%~2wt%, specifically 1wt%~1.5wt%, for example, 0.7wt%, 1wt%, 1.2wt%, 1.4wt%, 1.6wt%, 1.8wt%, 2wt%, and the like. The carbon content within the above range is conducive to obtaining a positive electrode material with a suitable morphology, thereby helping to increase the compaction density of the positive electrode material, and at the same time can effectively improve the conductivity of the positive electrode material, thereby improving the electrochemical performance of the positive electrode material. It should be noted that the carbon in the positive electrode material is mainly coated on the surface and exists in the positive electrode material in the form of a carbon coating layer.

[0081] According to the embodiment of the present application, the compaction density of the positive electrode material is 2.6 g / cm 3 ~2.9g / cm 3 , specifically 2.6 g / cm 3 , 2.62g / cm 3 , 2.64g / cm 3 , 2.66g / cm 3 , 2.68g / cm 3 , 2.70g / cm 3 , 2.72g / cm 3 , 2.74g / cm 3 , 2.76g / cm 3 , 2.78g / cm 3 , 2.80g / cm 3 , 2.82g / cm 3 , 2.84g / cm 3 , 2.86g / cm 3 , 2.88g / cm 3 , 2.90g / cm 3 Within the above compaction density range, the performance of lithium-ion batteries using the positive electrode material can be effectively improved.

[0082] In a second aspect of the present application, a method for preparing the aforementioned positive electrode material is provided. According to an embodiment of the present application, the method comprises the following steps:

[0083] S10: spray-drying the first mixture to obtain a spray-dried material.

[0084] In this step, the first mixture can be prepared by mixing iron phosphate, lithium source, optional M 1 Source, optional Q 1 The iron phosphate, lithium source, optional M 1 Source, optional Q 1There is no particular restriction on the specific method of mixing the lithium source and the carbon source, and there is no particular requirement for the order of adding the materials, which can be flexibly selected according to actual needs. As an example, a mixer can be used to mix the iron phosphate, lithium source, and optional M 1 Source, optional Q 1 The source is mixed with the carbon source.

[0085] It should be noted that the optional M in this article 1 Source is the raw material used in this step and can be M 1 Source, or no M 1 Source; similarly, optional Q 1 Source is the raw material used in this step and can have Q 1 Source, or no Q 1 As an example, in this step, iron phosphate, lithium source and carbon source can be mixed. 1 Mix the source with the carbon source, and you can mix the iron phosphate, lithium source, M 1 Source, Q 1 Source and carbon source are mixed, iron phosphate, lithium source, Q 1 The source is mixed with the carbon source.

[0086] In some embodiments, iron phosphate, lithium source, optional M 1 Source, optional Q 1 The source and the carbon source can be weighed and mixed according to the stoichiometric ratio of Li, Fe, M, P, and Q in Formula 1. The amount of the carbon source added is such that the carbon content accounts for 0.7 wt% to 2.0 wt% of the mass percentage of the target prepared positive electrode material.

[0087] It should be noted that M 1 Source is one of the sources of the M element in formula 1, M 1 M in the source 1 Elements and M in subsequent steps 2 M in the source 2 The elements together constitute the M element in formula 1. Similarly, Q 1 The source is one of the sources of the Q element in formula 1, Q 1 Q in the source 1 Q in elements and subsequent steps 2 Q in the source 2 The elements together constitute the Q element in formula 1. In addition, M 1 M in the source 1 Elements and Q 1 Q in the source 1 Elements can be provided by the same substance, namely M 1 Source and Q 1 The source can be the same substance, such as sodium sulfate, which can provide Na element (M 1 elements) and S elements (Q1 element); Similarly, M 2 Source and Q 2 The source can also be the same substance.

[0088] In some embodiments, spray-drying the first mixture includes: mixing the first mixture with a solvent to obtain a dispersion; grinding the dispersion to obtain a grinding slurry; and spray-drying the grinding slurry to obtain the spray-dried material.

[0089] In some embodiments, the type of solvent and the solid content of the dispersion are not particularly limited, as long as they can be fully dispersed and do not interact with the iron phosphate, lithium source, optional M 1 Source, optional Q 1 For production cost considerations, the solvent in this application can be deionized water, and the solid content of the dispersion is ≥35% (specifically, 35%, 40%, 45%, 50%, 55%, 60%, etc.).

[0090] According to the embodiment of the present application, the particle size of the grinding slurry satisfies: D 50 is 0.1 μm to 0.6 μm, specifically 0.25 μm to 0.5 μm, for example, the D 50 Specifically, it can be 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.55 μm, 0.6 μm, etc. Meeting the above particle size range is conducive to obtaining a positive electrode material with a suitable sub-grain size and particle size range, thereby helping to improve the compaction density of the positive electrode material.

[0091] According to the embodiments of the present application, the iron-phosphorus molar ratio Fe / P of the ferric phosphate is 0.95-0.98, specifically 0.95, 0.955, 0.96, 0.965, 0.97, 0.975, 0.98, etc. Meeting the above Fe / P range is conducive to obtaining a positive electrode material with a suitable micromorphology, thereby helping to increase the compaction density of the positive electrode material.

[0092] According to the embodiment of the present application, the particle size D of the iron phosphate is 50 4μm~20μm, specifically 4μm, 6μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, etc. 50 range, which is conducive to obtaining positive electrode materials with suitable micromorphology, and further conducive to improving the compaction density of positive electrode materials.

[0093] According to the embodiment of the present application, the specific surface area of ​​the iron phosphate is 6m 2 / g~12m 2 / g, such as 6m 2 / g、7m 2 / g、8m 2 / g、9m 2 / g、10m 2 / g、11m 2 / g、12m 2 / g, etc. Meeting the above BET range is conducive to obtaining a positive electrode material with a suitable micromorphology, and further conducive to improving the compaction density of the positive electrode material.

[0094] According to an embodiment of the present application, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium phosphate, and lithium nitrate, thereby allowing sufficient iron phosphate reaction to occur, thereby obtaining a high-quality positive electrode material.

[0095] According to an embodiment of the present application, the M 1 Sources include M 1 At least one of the oxides, hydroxides, carbonates, halides, silicates and sulfates of an element. 1 The element includes at least one of Ti, Mg, Zn, Cu, Sr, Al, Zr, Y, Co, W, Ca, Nb, Sn, Sb, Mo, V, B, and Na. In some embodiments, M 1 Elements can be doped into the lattice of the positive electrode material, thereby improving the electrochemical performance of the positive electrode material.

[0096] According to an embodiment of the present application, the Q 1 Q in the source 1 The element includes at least one of Si, S, F, Cl, Br, and I. 1 The source may include Li and / or M 1 In some embodiments, Q 1 Elements can be doped into the lattice of the positive electrode material, thereby improving the electrochemical performance of the positive electrode material.

[0097] I understand, Q 1 The source may include Li and / or M 1 At least one of sulfate, silicate, and halide refers to Q 1 The source may include Li sulfate, Li silicate, Li halide, M 1 Sulfate, M 1 Silicate, M 1 At least one of the halides.

[0098] According to an embodiment of the present application, the carbon source includes at least one of glucose, sucrose, and an organic polymer. Thus, a good carbon coating layer can be formed on the surface of the positive electrode material, thereby improving the conductivity of the positive electrode material and increasing the compaction density of the positive electrode material.

[0099] According to the embodiments of the present application, the specific operation mode and parameters of the spray drying are not particularly limited and can be performed with reference to conventional techniques. It is understood that the particle size and morphology of the spray-dried material can be adjusted by appropriately adjusting the spray drying parameters.

[0100] S20: sintering the spray-dried material once to obtain a lithium iron phosphate precursor.

[0101] In this step, the iron phosphate can react with the lithium source to generate lithium iron phosphate by sintering once. 1 M in the source 1 Element, Q 1 Q in the source 1 Elements can be doped into the crystal structure of lithium iron phosphate, and the carbon source can form a carbon coating layer on the surface of lithium iron phosphate.

[0102] According to an embodiment of the present application, the sintering temperature of the primary sintering is 700°C to 850°C, specifically 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C, 790°C, 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, etc. Within the above temperature range, it is beneficial to obtain a positive electrode material with a suitable microstructure, thereby improving the compaction density and electrochemical performance of the positive electrode material.

[0103] According to the embodiments of the present application, the sintering time of the primary sintering is 6 hours to 16 hours, specifically 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, etc. The above time range can ensure that the reaction is fully completed without wasting time.

[0104] According to the embodiments of the present application, the product of the primary sintering can be crushed after the primary sintering is completed, thereby dissociating the agglomerated particles in the product of the primary sintering to obtain a positive electrode material with a suitable particle size.

[0105] According to the embodiments of the present application, there is no particular limitation on the crushing equipment that can be used, as long as it can break up the agglomerated lithium iron phosphate. Considering production costs, the crushing equipment can be at least one of a mechanical mill and a jet mill.

[0106] S30: performing secondary sintering on the second mixture containing the lithium iron phosphate precursor to obtain the positive electrode material.

[0107] In this step, the second mixture can be prepared by mixing the lithium iron phosphate precursor, the optional M 2 Source with optional Q 2 The lithium iron phosphate precursor, the optional M 2 Source with optional Q 2 Source mixing can be performed by dry coating. In some embodiments, the dry coating equipment is not particularly limited, as long as it can be used to mix lithium iron phosphate, optional M 2 Source with optional Q 2 Considering the production cost, the dry coating equipment can be at least one of a high-pressure mixer and a plowshare mixer.

[0108] It should be noted that the optional M in this article 2 Source is the raw material used in this step and can be M 2 Source, or no M 2 Source; similarly, optional Q 2 Source is the raw material used in this step and can have Q 2 Source, or no Q 2 As an example, in this step, the lithium iron phosphate precursor can be directly used, and the lithium iron phosphate precursor can be mixed with M 2 The source can be mixed to make lithium iron phosphate precursor, M 2 Source and Q 2 Source mixing, you can also mix the lithium iron phosphate precursor with Q 2 Source mixing.

[0109] According to an embodiment of the present application, the M 2 Sources include M 2 At least one of the oxides, hydroxides, carbonates, halides, silicates and sulfates of an element. 2 The element includes at least one of Ti, Mg, Zn, Cu, Sr, Al, Zr, Y, Co, W, Ca, Nb, Sn, Sb, Mo, V, B, and Na. Specifically, M 2 The source can form a coating layer on the surface of the lithium iron phosphate precursor, adjust the microstructure of the positive electrode material, and thus help to improve the compaction density of the positive electrode material.

[0110] According to an embodiment of the present application, the Q 2 Q in the source 2 The element includes at least one of Si, S, F, Cl, Br, and I. 2 Sources can include Li, M 2 In some embodiments, Q 2 Elements can be doped into the lattice of the positive electrode material, thereby improving the electrochemical performance of the positive electrode material.

[0111] I understand, Q 2 The source may include Li and / or M 2 At least one of sulfate, silicate, and halide refers to Q 2 The source may include Li sulfate, Li silicate, Li halide, M 2 Sulfate, M 2 Silicate, M 2 At least one of the halides.

[0112] According to an embodiment of the present application, the sintering temperature of the secondary sintering is 650°C to 800°C, specifically 650°C, 680°C, 700°C, 720°C, 750°C, 780°C, 800°C, etc. Within the above temperature range, the positive electrode material is conducive to obtaining a suitable microstructure, thereby improving the energy density and electrochemical performance of the positive electrode material.

[0113] According to the embodiments of the present application, the secondary sintering time is 4 hours to 20 hours, specifically 4 hours, 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, etc. Within the above time range, the reaction can be fully carried out without wasting time.

[0114] The preparation method of the positive electrode material of the present application has a simple process flow and is suitable for application in large-scale industrial production. The obtained positive electrode material has a high compaction density, good electrochemical performance, and excellent cycle stability.

[0115] In a third aspect, the present application provides a lithium-ion battery comprising the cathode material described in the first aspect of the present application or the cathode material prepared by the method of the second aspect. Thus, the lithium-ion battery has a high energy density, excellent electrochemical performance, and excellent cycle stability.

[0116] It is understood that there is no particular limitation on the specific type of the lithium-ion battery, which may be a primary battery or a secondary battery; the shape of the lithium-ion battery may be a cylindrical battery, a square battery, or a battery of any other shape, and according to the outer packaging classification, the lithium-ion battery may be a hard-shell battery, a soft-pack battery, etc.

[0117] Typically, a lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. The positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly through a winding or lamination process, and the electrode assembly and the electrolyte can be contained in an outer packaging. During the charge and discharge process of the lithium-ion battery, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0118] In some embodiments, the positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode current collector may include a metal foil, for example, aluminum foil. The positive electrode active material may include the positive electrode material of the first aspect of this application or the positive electrode material prepared by the method described in the second aspect of this application. The conductive agent may include acetylene black, single-walled carbon nanotubes, and other materials conventional in the art. The binder may include polyvinylidene fluoride (PVDF) and other materials conventional in the art.

[0119] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material, a thickener, a conductive agent, and a binder. The negative electrode current collector may be a metal foil, for example, copper foil. The negative electrode active material may include artificial graphite, natural graphite, silicon-containing carbon-based composite materials, lithium-containing metal composite materials, lithium metal materials, and other common negative electrode active materials in the art. The thickener may be sodium carboxymethylcellulose (CMC-Na) or other materials commonly used in the art. The conductive agent may be acetylene black or other materials commonly used in the art. The binder may be styrene-butadiene rubber or other materials commonly used in the art.

[0120] In some embodiments, the separator can be a separator known in the art that can be used in lithium-ion batteries and is stable to the electrolyte used, such as a polyethylene separator, a polypropylene separator, a polyethylene / polypropylene composite separator, etc.

[0121] The fourth aspect of the present application provides an electrical device comprising the lithium-ion battery described in the third aspect of the present application. The electrical device has all the features and advantages of the lithium-ion battery described above, which will not be described in detail here.

[0122] In some embodiments, the electrical devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.

[0123] The embodiments of the present application are described in detail below.

[0124] Example 1

[0125] Step S1: lithium carbonate, iron phosphate, titanium oxide 1, titanium oxide 4, vanadium oxide, and phosphoric acid are weighed and prepared according to the molar ratio of Li, Fe, Ti1, Ti4, V, and P of 1.050:0.97:0.01:0.01:0.01:1.030. Titanium oxide 1 is used in step S1, titanium oxide 4 is used in step S4, and the carbon source glucose accounts for 8.0% of the theoretical yield of lithium iron phosphate. The mixture is added to the solvent deionized water, the solid content is controlled at 40wt%, and the mixture is ground by a ball mill (rotation speed is 2000rpm). D 50 When the particle size reaches 0.4 μm, the machine is stopped and the primary grinding material I is obtained;

[0126] Step S2: The primary ground material I obtained in step S1 was spray dried using an atomizing disk atomizer (the inlet temperature was set to 225±°C and the outlet temperature was controlled at 100±5°C) to obtain a primary spray-dried material. The dried material was heated to 800°C at a heating rate of 2°C / min under a nitrogen atmosphere, kept at this temperature for 8 hours, and then cooled in the furnace to obtain a primary sintered material II.

[0127] Step S3: crush the primary sintered material II obtained in step S2 by using a jet mill, 50 When the particle size reaches 1.3 μm, the machine is stopped and the primary crushed material III is obtained. The scanning electron microscope photo of the material is shown in Figure 1 ;

[0128] Step S4: Mix the primary crushed material III obtained in step S3 with titanium oxide 4 to obtain a uniform mixture IV.

[0129] Step S5: The uniform mixture IV obtained in step S4 was heated to 730°C at a heating rate of 2°C / min under N2 atmosphere, kept at this temperature for 8 hours, and then cooled in the furnace to obtain a lithium iron phosphate positive electrode material, the scanning electron microscope photo of which is shown in FIG. Figure 2 .

[0130] Example 2:

[0131] The method of Example 1 is followed, except that in step S1, the molar ratio of Li, Fe, Ti1, Ti4, V, and P is 1.050:0.97:0.01:0.01:0.01:1.000, and the rest are the same, to obtain the lithium iron phosphate positive electrode material.

[0132] Example 3:

[0133] The method of Example 1 is followed, except that in step S1, the molar ratio of Li, Fe, Ti1, Ti4, V, and P is 1.050:0.97:0.01:0.01:0.01:1.080, and the rest are the same to obtain the lithium iron phosphate positive electrode material.

[0134] Examples 4 to 21

[0135] According to the method of Example 1, the specific differences are shown in Table 1.

[0136] Comparative Example 1:

[0137] The method of Example 1 is followed, except that in step S1, the molar ratio of Li, Fe, Ti1, Ti4, V, and P is 1.050:0.97:0.01:0.01:0.01:0.920, and the rest are the same to obtain the lithium iron phosphate positive electrode material.

[0138] Comparative Example 2:

[0139] The method of Example 1 is followed, except that in step S2, the dried material is heated to 400° C. at a heating rate of 2° C. / min under a N 2 atmosphere and kept warm for 6 h. The rest of the process is the same to obtain the lithium iron phosphate positive electrode material.

[0140] Table 1: Preparation parameters

[0141]

[0142]

[0143]

[0144] Performance testing:

[0145] 1. Unit Cell Volume: Measured using a Rigaku Smartlab 9KW rotating target diffractometer with a scanning range of 10°–80°, voltage of 40 kV, current of 200 mA, step size of 0.02°, and scan time of 2° / min. The results were refined and calculated using the WPPF method in SmartLab Studio II software to obtain the unit cell volume.

[0146] 2. Subgrain size and subgrain size distribution: Subgrain size L 10 , L 50 , L 90 :Tested by Rigaku rotating target diffractometer Smartlab 9KW, range 10°~80°, voltage 40kV, current 200mA, step 0.02°, scan time 2° / min. The test results were obtained by statistically calculating the sub-grain size using the WPPF sub-grain size distribution function of SmartLab Studio II software according to the Fundamental Parameter method (FP method). The sub-grain size distribution curves of the positive electrode materials in Example 1 and Comparative Example 1 are shown in Figure 3 .

[0147] 3. Compaction density: Measured using Sansi Zongheng (UTM7305) compaction density meter. Weigh 1±0.01g of sample and select a pressure of 3T for testing.

[0148] 4. Carbon content: Measured using Beijing Wanlianda CS-901B high-frequency infrared carbon and sulfur analyzer. Weigh 0.2±0.05g of sample for testing.

[0149] 5. D 50 : 1) Malvern 3000-LV particle size analyzer; 2) Dispersant: water; 3) Opacity: 10%-15%; 4) Refractive index: 1.74; 5) Test cycles: 2 times.

[0150] 6. 0.1C First Charge and Discharge Specific Capacity: The electrochemical performance of R2025 button cells was tested using the Shenzhen Xinweier Battery Testing System. The first charge and discharge capacity test conditions were: 25°C, 0.1C charge and discharge, voltage range 2.5V~4.2V, and constant voltage charge cutoff current of 0.05C. The battery preparation process is as follows:

[0151] Pole sheet preparation: The positive electrode material, conductive agent SuperP and polyvinylidene fluoride (PVDF) were mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a mass ratio of 96.5:1.5:2 to form a uniform slurry. The slurry was coated on aluminum foil and dried at 120°C for 12 hours. The pole sheet was compacted to 2.5g / cm 3 , and then stamped into a positive electrode sheet with a diameter of 12 mm.

[0152] Battery Assembly: In an argon-filled glove box with water and oxygen contents less than 5 ppm, the positive electrode, separator, negative electrode, and electrolyte were assembled into R2025 button cells and allowed to rest for 6 hours. The negative electrode used a 15.6 mm diameter, 0.45 mm thick lithium metal sheet; the separator used a 25 μm polypropylene microporous membrane (Celgard 2325); and the electrolyte used a 1 mol / L mixture of equal parts LiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC).

[0153] Table 2: Test results

[0154]

[0155]

[0156] The above test results show that the sub-grain size of the positive electrode material is controlled to meet 80nm≤L 10 ≤200nm; 150nm≤L 50 ≤500nm; 400nm≤L 90≤1000 nm; 1 < S < 2. The tap density of the positive electrode material is relatively high, and the charge-discharge specific capacity of the lithium-ion battery using this positive electrode material remains at a relatively high level.

[0157] In the description of the present application, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0158] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.

Claims

1. A positive electrode material, characterized in that Comprising the composition shown in Formula 1, Li a Fe b M c (PO4) d Q e Formula 1 In formula 1, 0.95≤ a ≤1.10,0.7≤ b ≤1,0< c ≤0.5,0.95≤ d ≤1.10,0≤ e ≤0.05, M includes at least one of Ti, Mg, Zn, Sr, Al, Zr, Co, W, Ca, Nb, Sn, Sb, V, and Na, and Q includes at least one of Si, S, F, Cl, Br, and I; The positive electrode material satisfies: 80nm≤L 10 ≤200nm; 150nm≤L 50 ≤500nm; 500nm<L 90 ≤1000nm; 1<S<2； Among them, L 10 、L 50 、L 90 is the sub-grain size corresponding to the cumulative volume percentage of the sub-grain size Ln of the positive electrode material reaching 10%, 50% and 90%, respectively; S is the skewness coefficient of the sub-grain size sample of the positive electrode material obtained by the third-order dynamic moment method; The compaction density of the positive electrode material is 2.6 g / cm 3 ~2.9g / cm 3 .

2. The positive electrode material according to claim 1, characterized in that The positive electrode material satisfies at least one of the following conditions: 100nm≤L 10 ≤180nm; 200nm≤L 50 ≤400nm; 500nm<L 90 ≤900nm; 1.2<S<1.9。 3. The positive electrode material according to claim 1, characterized in that 1.3≤(L 90 -L 10 ) / L 50 ≤2.

2.

4. The positive electrode material according to claim 3, characterized in that 1.5≤(L 90 -L 10 ) / L 50 ≤2.

0.

5. The positive electrode material according to claim 1, characterized in that The kurtosis coefficient K of the sub-grain size of the positive electrode material obtained by the fourth-order dynamic moment method satisfies: <K<8。 6. The positive electrode material according to claim 5, characterized in that 4.5<K<7.5。 7. The positive electrode material according to claim 1, characterized in that The sub-grain size distribution curve of the positive electrode material includes only one peak.

8. The positive electrode material according to claim 1, characterized in that The unit cell volume of the cathode material is 287.0 Å 3 ~293.0Å 3 .

9. The positive electrode material according to claim 8, characterized in that The unit cell volume of the cathode material is 288.000 Å 3 ~292.000Å 3 .

10. The positive electrode material according to claim 1, characterized in that Based on the total weight of the positive electrode material, the carbon content in the positive electrode material is 0.7 wt % to 2 wt %.

11. The positive electrode material according to claim 10, characterized in that Based on the total weight of the positive electrode material, the carbon content in the positive electrode material is 1 wt% to 1.5 wt%.

12. A method for preparing the positive electrode material according to any one of claims 1 to 11, characterized in that: include: mixing the first mixture with a solvent to obtain a dispersion; Grinding the dispersion to obtain a grinding slurry; spray drying the ground slurry to obtain a spray-dried material; sintering the spray-dried material at 700° C. to 850° C. to obtain a lithium iron phosphate precursor; sintering the second mixture containing the lithium iron phosphate precursor at 650° C. to 800° C. to obtain the positive electrode material; Wherein, the first mixture includes iron phosphate, a lithium source and a carbon source; the first mixture includes the iron phosphate, the lithium source, the carbon source and M 1 Source; the first mixture comprises the iron phosphate, the lithium source, the carbon source and the M 1 Source and Q 1 Source; or the first mixture includes the iron phosphate, the lithium source, the carbon source and the Q 1 source; The second mixture includes the lithium iron phosphate precursor and M 2 Source; the second mixture comprises the lithium iron phosphate precursor, the M 2 Source and Q 2 Source; or the second mixture comprises the lithium iron phosphate precursor and the Q 2 source; The M 1 M in the source 1 Elements and the M 2 M in the source 2 The elements independently include at least one of Ti, Mg, Zn, Sr, Al, Zr, Co, W, Ca, Nb, Sn, Sb, V, and Na; The Q 1 Q in the source 1 Elements and the Q 2 Q in the source 2 The elements independently include at least one of Si, S, F, Cl, Br, and I; The particle size D of the iron phosphate 50 4μm~20μm; The particle size D of the grinding slurry 50 0.1μm~0.6μm.

13. The method according to claim 12, characterized in that The ferric phosphate satisfies at least one of the following conditions: The iron-phosphorus molar ratio Fe / P of the ferric phosphate is 0.95-0.98; The specific surface area of ​​the iron phosphate is 6 m 2 / g~12m 2 / g.

14. The method according to claim 12, characterized in that Meet at least one of the following conditions: The lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium phosphate and lithium nitrate; The M 1 Sources include M 1 At least one of an oxide, hydroxide, carbonate, halide, silicate and sulfate of an element; The M 2 Sources include M 2 At least one of an oxide, hydroxide, carbonate, halide, silicate and sulfate of an element; The Q 1 Sources include Li and / or M 1 At least one of sulfate, silicate, and halide; The Q 2 Sources include Li and / or M 2 At least one of sulfate, silicate, and halide; The carbon source includes at least one of glucose, sucrose and an organic polymer.

15. The method according to claim 12, characterized in that Meet at least one of the following conditions: The solvent includes deionized water; The solid content of the dispersion is ≥35%.

16. The method according to claim 12, characterized in that Meet at least one of the following conditions: The sintering time of the primary sintering is 6h~16h; The sintering time of the secondary sintering is 4h~20h.

17. A lithium ion battery, characterized in that: The positive electrode material comprises the positive electrode material according to any one of claims 1 to 11.

18. An electrical device, characterized in that: Including the lithium ion battery according to claim 17.

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