Positive electrode material, and preparation method therefor and use thereof

Abstract

The present application relates to the field of lithium-ion batteries, and provides a positive electrode material, and a preparation method therefor and a use thereof. The positive electrode material comprises first core particles and a first coating layer coating the surfaces of the first core particles. The chemical general formula of the first core particles is LiaFebTiAlc(PO4)d, and the first coating layer is a carbon layer, wherein 7.5≤a≤14.5, 5≤b≤10, 0.1≤c≤0.2, and a / 3+1.02×(2 / 3b+1+c)≤d≤a / 3+1.05×(2 / 3b+1+c). The positive electrode material in embodiments of the present application has both a relatively high capacity and a relatively high compacted density.

Description

Cathode materials, their preparation methods and applications Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to a cathode material, its preparation method, and its application. Background Technology

[0002] Lithium iron phosphate (LFP) batteries, as a type of power battery, possess high safety, long lifespan, and superior charging performance, and are widely used in new energy vehicles. With increasingly demanding requirements for the driving range of lithium-ion batteries, there is a need for cathode active materials with high compaction density to improve the mass energy density and volumetric energy density of LFP batteries. Traditional methods of increasing the compaction density of LFP materials lead to a decrease in capacity, thus doping is often necessary to improve capacity. However, conventional metal dopants hinder the growth of LFP crystals, resulting in a low compaction density. In other words, traditional LFP cathode materials struggle to simultaneously achieve both high capacity and high compaction density. Summary of the Invention

[0003] In view of the technical problems existing in the background art, this application provides a cathode material, its preparation method and application, aiming to solve the technical problem that traditional lithium iron phosphate cathode materials are difficult to have both high capacity and high compaction density at the same time.

[0004] In a first aspect, embodiments of this application provide a cathode material, the cathode material comprising a first core particle and a first coating layer covering the surface of the first core particle, wherein the chemical formula of the first core particle is Li. a Fe b TiAl c (PO4) d The first coating layer is a carbon layer; wherein, 7.5≤a≤14.5, 5≤b≤10, 0.1≤c≤0.2, a / 3+1.02×(2 / 3b+1+c)≤d≤a / 3+1.05×(2 / 3b+1+c).

[0005] In the technical solution of this application embodiment, the doping elements in the first core particle of the cathode material are trivalent titanium and aluminum. Compared with the traditional cathode material doped with tetravalent titanium, trivalent titanium has a larger ionic radius and is easier to dop in the iron sites. At the same time, because the doping of trivalent titanium does not require a reduction reaction, it can be doped at a lower temperature, so the doping effect of trivalent titanium is better and the diffusion of titanium is more uniform. By co-doping the cathode material with aluminum and trivalent titanium, the compaction density can be increased, and the ionic conductivity of the cathode material can also be improved, thereby improving the capacity of the cathode material. Thus, the cathode material of this application embodiment has both high capacity and high compaction density.

[0006] In some embodiments, the compaction density of the positive electrode material is 2.45 g / cm³. 3 ~2.6g / cm 3 .

[0007] In this embodiment, within the range of the compaction density of the aforementioned cathode material, it is beneficial to improve the energy density of the cathode material.

[0008] In some embodiments, the carbon layer comprises 0.7% to 2.3% by mass in the cathode material.

[0009] In this embodiment, within the range of the mass percentage of the carbon layer in the cathode material, it is beneficial to improve the electronic conductivity of the cathode material.

[0010] Secondly, embodiments of this application provide a method for preparing a cathode material, comprising the following steps:

[0011] The titanium source, the first lithium source, and the phosphorus source are subjected to a first reaction treatment to obtain the preparative material;

[0012] The prepared materials and aluminum source are subjected to a second reaction treatment to obtain lithium titanium phosphate material;

[0013] The lithium titanium phosphate material, along with an iron source, a second lithium source, and a carbon source, undergoes a third reaction treatment to obtain the cathode material.

[0014] The titanium element in the titanium source has a oxidation state of +3. The cathode material includes a first core particle and a first coating layer covering the surface of the first core particle. The chemical formula of the first core particle is Li. a Fe b TiAl c (PO4) d The first coating layer is a carbon layer; wherein, 7.5≤a≤14.5, 5≤b≤10, 0.1≤c≤0.2, a / 3+1.02×(2 / 3b+1+c)≤d≤a / 3+1.05×(2 / 3b+1+c).

[0015] In the technical solution of this application embodiment, a preliminary material is first obtained by reacting a titanium source, a first lithium source, and a phosphorus source through a first reaction. Then, the preliminary material and an aluminum source are reacted through a second reaction to obtain lithium titanium phosphate material. The lithium titanium phosphate material includes two doping elements: trivalent titanium and aluminum. It has high activity and high purity, and its primary particle size is small, which is beneficial for subsequent doping in the third reaction process. Furthermore, by introducing trivalent titanium, the ionic radius of trivalent titanium is larger than that of tetravalent titanium, making it easier to dope at iron sites. Since the doping of trivalent titanium does not require a reduction reaction, it can be carried out at lower temperatures, resulting in better doping effects and more uniform titanium diffusion. By co-doping the cathode material with aluminum and trivalent titanium, the compaction density is increased, and the ionic conductivity and capacity of the cathode material are also improved. Therefore, the cathode material obtained by the cathode material preparation method of this application embodiment has both high capacity and high compaction density.

[0016] In some embodiments, the lithium titanium phosphate material includes a second core particle and a second coating layer covering the surface of the second core particle, wherein the chemical formula of the second core particle is Li3Ti(PO4)2, and the second coating layer includes aluminum.

[0017] In this embodiment, lithium titanium phosphate material reacts with a second lithium source, an iron source, and a carbon source to obtain a cathode material. By introducing titanium and aluminum elements, lithium and phosphate are added, which is beneficial to improving the compaction density and capacity of the cathode material.

[0018] In some embodiments, the molar ratio of titanium, lithium and phosphorus in the mixture of the titanium source, the first lithium source and the phosphorus source is 1:(3.2-3.8):(2.1-2.5).

[0019] In this embodiment, the molar ratio of titanium, lithium and phosphorus in the mixture of titanium source, first lithium source and phosphorus source is kept to be 1:(3.2~3.8):(2.1~2.5), which is beneficial to obtain second core particles with appropriate molar ratio of each element, and obtain lithium titanium phosphate material with appropriate molar ratio of each element, thereby improving the compaction density and capacity of the cathode material.

[0020] In some embodiments, the molar ratio of titanium in the preparative material to aluminum in the aluminum source is 1:(0.1 to 0.2).

[0021] In this embodiment, the molar ratio of titanium in the preparative material to aluminum in the aluminum source is kept within the range of 1:(0.1 to 0.2) to obtain lithium titanium phosphate material with appropriate titanium and aluminum doping amounts, thereby obtaining a cathode material with appropriate titanium and aluminum doping amounts, which is beneficial to balance the capacity and compaction density of the cathode material.

[0022] In some embodiments, the molar ratio of titanium in the lithium titanium phosphate material, iron in the iron source, lithium in the second lithium source, and carbon in the carbon source is 1:(5-10):(5.2-11):(12-36).

[0023] In this embodiment, the molar ratio of titanium in the lithium titanium phosphate material, iron in the iron source, lithium in the second lithium source, and carbon in the carbon source is kept within the range of 1:(5-10):(5.2-11):(12-36) to obtain a cathode material with a suitable molar ratio of each element, which is beneficial to balance the capacity and compaction density of the cathode material.

[0024] In some embodiments, the temperature of the first reaction treatment is 200°C to 350°C.

[0025] In some embodiments, the pressure of the first reaction process is 10 MPa to 20 MPa.

[0026] In some embodiments, the first reaction treatment time is 5h to 15h.

[0027] In this embodiment, the temperature of the first reaction treatment is kept in the range of 200℃ to 350℃, the pressure is kept in the range of 10MPa to 20MPa, and the time is kept in the range of 5h to 15h, which is conducive to the titanium source, the first lithium source and the phosphorus source being processed by the first reaction to obtain the preparative material.

[0028] In some embodiments, the titanium source includes titanium trichloride.

[0029] In this embodiment, the titanium source includes titanium trichloride. Compared with traditional cathode materials doped with tetravalent titanium, trivalent titanium has a larger ionic radius and is easier to dop at iron sites. At the same time, because the doping of trivalent titanium does not require a reduction reaction, it can be carried out at a lower temperature, and the doping effect of trivalent titanium is better, with more uniform titanium diffusion.

[0030] In some embodiments, the first lithium source includes at least one of lithium hydroxide, lithium oxide, lithium dihydrogen phosphate, and lithium monohydrogen phosphate.

[0031] In some embodiments, the phosphorus source includes at least one of lithium dihydrogen phosphate and lithium monohydrogen phosphate.

[0032] In some embodiments, the iron source includes iron phosphate.

[0033] In this embodiment, the use of the first lithium source, phosphorus source, and iron source reduces the introduction of impurities, which is beneficial for preparing high-purity preparative materials and thus for preparing high-purity cathode materials.

[0034] In some embodiments, the second lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium oxalate, and lithium acetate.

[0035] In this embodiment, the use of the second lithium source reduces the introduction of impurities, which is beneficial for preparing cathode materials with higher purity.

[0036] In some embodiments, the step of treating the titanium source, the first lithium source, and the phosphorus source with the first reaction further includes adding a reducing agent.

[0037] In this embodiment, a reducing agent is added to the titanium source, the first lithium source, and the phosphorus source during the first reaction treatment step to prevent trivalent titanium from being oxidized during the reaction.

[0038] In some embodiments, the molar ratio of the reducing agent to the titanium element in the titanium source is (0.1 to 0.2):1.

[0039] In this embodiment, within the range of the molar ratio of titanium in the reducing agent and the titanium source, it is beneficial to fully prevent trivalent titanium from being oxidized during the reaction.

[0040] In some embodiments, the reducing agent includes at least one of hydrazine hydrate, sodium sulfite, and hypophosphorous acid.

[0041] In this embodiment, the selection of the aforementioned reducing agent reduces the introduction of impurities, which is beneficial for preparing cathode materials with higher purity.

[0042] In some embodiments, the second reaction treatment of the preparative material and aluminum source includes the following steps:

[0043] The prepared materials, dispersant and aluminum source are mixed to form a first slurry, and the pH value of the first slurry is adjusted to 8-10;

[0044] The first slurry was subjected to solid-liquid separation to obtain a solid product;

[0045] The solid product is subjected to a first calcination treatment to obtain the lithium titanium phosphate material.

[0046] In this embodiment, the second reaction process described above can prepare lithium titanium phosphate material with high activity, high purity and small primary particle size, which is beneficial to the uniform mixing of raw materials in the subsequent third reaction process, thereby improving the uniformity of the distribution of titanium and aluminum elements in the first core particles, which is beneficial to improving the compaction density and capacity of the cathode material.

[0047] In some embodiments, the lithium titanium phosphate material, along with an iron source, a second lithium source, and a carbon source, undergoes a third reaction treatment to obtain a cathode material, comprising the following steps:

[0048] The lithium titanium phosphate material, the iron source, the second lithium source, and the carbon source are mixed to form a second slurry;

[0049] The second slurry is ground until the particle size of the particles in the second slurry is 300nm to 600nm;

[0050] The second slurry is subjected to solid-liquid separation to obtain a mixture.

[0051] The mixture is subjected to a second calcination treatment to obtain the positive electrode material.

[0052] In this embodiment, in the third reaction process described above, lithium titanium phosphate material is mixed with an iron source, a second lithium source, and a carbon source to form a second slurry. The second slurry is then ground until the particle size of the particles in the second slurry is 300nm to 600nm. This allows the raw materials to be mixed evenly and to have more sufficient contact with each other. As a result, during the second calcination process, the titanium and aluminum elements are more evenly distributed in the first core particles of the cathode material, which is beneficial to improving the compaction density and capacity of the cathode material.

[0053] In some embodiments, the calcination temperature of the second calcination treatment is 700°C to 850°C.

[0054] In some embodiments, the calcination time for the second calcination treatment is 6h to 15h.

[0055] In this embodiment, maintaining the calcination temperature of the second calcination treatment within the range of 700℃ to 850℃ and the calcination time within the range of 6h to 15h is beneficial for the mixture to undergo the second calcination treatment to obtain the cathode material.

[0056] Thirdly, embodiments of this application provide a positive electrode sheet, including a current collector and an active layer located on the surface of the current collector, wherein the active layer includes the positive electrode material described in any of the above claims or the positive electrode material prepared by the preparation method of the positive electrode material described in any of the above claims.

[0057] In this embodiment, the positive electrode sheet contains the aforementioned positive electrode material, and therefore has good electrochemical performance.

[0058] Fourthly, embodiments of this application provide a secondary battery, including the aforementioned positive electrode.

[0059] In this embodiment, the secondary battery includes the aforementioned positive electrode, thus possessing comprehensively improved electrochemical performance, and can be well applied in multiple application scenarios.

[0060] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0061] To more clearly illustrate the technical solution of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0062] Figure 1 is a schematic flowchart of the preparation method of the cathode material provided in the embodiments of this application;

[0063] Figure 2 is a scanning electron microscope (SEM) image of the cathode material in Example 1 of the present invention;

[0064] Figure 3 is a SEM image of the cathode material in Example 2 of the present invention. Detailed Implementation

[0065] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0067] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0068] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0069] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0070] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0071] In the description of the embodiments of this application, the technical terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of this application.

[0072] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0073] With increasingly demanding requirements for the driving range of lithium-ion batteries, there is a need for cathode active materials with high compaction density to improve the mass energy density and volumetric energy density of lithium iron phosphate (LFP) batteries. Traditional methods of increasing the compaction density of LFP materials lead to a decrease in the capacity of LFP materials, thus doping is often necessary to improve the capacity of LFP materials. However, conventional metal dopants hinder the growth of LFP crystals, resulting in a low compaction density of LFP materials. In other words, traditional LFP cathode materials struggle to simultaneously achieve both high capacity and high compaction density.

[0074] To address the technical challenge of simultaneously achieving high capacity and high compaction density in lithium iron phosphate cathode materials, this application provides a cathode material, its preparation method, a cathode electrode sheet, a secondary battery, and an electrical device. The cathode material is co-doped with trivalent titanium and aluminum, thereby achieving both high capacity and high compaction density, which in turn improves the electrochemical performance of the cathode electrode sheet and the secondary battery.

[0075] In a first aspect, embodiments of this application provide a cathode material, comprising a first core particle and a first coating layer covering the surface of the first core particle, wherein the chemical formula of the first core particle is Li. a Fe b TiAl c (PO4) d The first coating layer is a carbon layer; where 7.5≤a≤14.5, 5.0≤b≤10.0, 0.10≤c≤0.20, and a / 3+1.02×(2 / 3b+1+c)≤d≤a / 3+1.05×(2 / 3b+1+c).

[0076] In the technical solution of this application embodiment, the doping elements in the first core particle of the cathode material are trivalent titanium and aluminum. Compared with the traditional cathode material doped with tetravalent titanium, trivalent titanium has a larger ionic radius and is easier to dop in the iron sites. At the same time, because the doping of trivalent titanium does not require a reduction reaction, it can be doped at a lower temperature, so the doping effect of trivalent titanium is better and the diffusion of titanium is more uniform. By co-doping the cathode material with aluminum and trivalent titanium, the compaction density can be increased, and the ionic conductivity of the cathode material can also be improved, thereby improving the capacity of the cathode material. Thus, the cathode material of this application embodiment has both high capacity and high compaction density.

[0077] Alternatively, a = 7.5, 8.0, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14 or 14.5, or a can be within the range of any two of the above values.

[0078] Alternatively, b = 5.0, 5.5, 6, 6.5, 7, 7.5, 8.0, 8.5, 9, 9.5 or 10.0, or b can be within the range of any two of the above values.

[0079] Alternatively, c = 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19 or 0.20, or c can be within the range of any two of the above values.

[0080] Alternatively, d = a / 3 + 1.02 × (2 / 3b + 1 + c), a / 3 + 1.025 × (2 / 3b + 1 + c), a / 3 + 1.03 × (2 / 3b + 1 + c), a / 3 + 1.035 × (2 / 3b + 1 + c), a / 3 + 1.04 × (2 / 3b + 1 + c), a / 3 + 1.045 × (2 / 3b + 1 + c), or a / 3 + 1.05 × (2 / 3b + 1 + c), or d can be within the range of any two of the above values.

[0081] In some embodiments, 7.2 ≤ d ≤ 13.

[0082] Alternatively, d = 7.2, 7.3, 8, 8.5, 9, 9.6, 10, 10.3, 10.5, 11, 12, 12.3 or 13, or d can be within the range of any two of the above values.

[0083] In some embodiments, the compaction density of the cathode material is 2.45 g / cm³. 3 ~2.60g / cm 3 .

[0084] In this embodiment, within the aforementioned compaction density range of the cathode material, it is advantageous to obtain higher capacity and energy density. Optionally, the compaction density of the cathode material is 2.45 g / cm³. 3 2.48 g / cm 3 2.5g / cm 3 2.52g / cm 3 2.55g / cm 3 2.58g / cm 3 Or 2.60 g / cm 3 Alternatively, the compaction density of the cathode material can also be within the range between any two of the aforementioned compaction densities.

[0085] In some embodiments, the BET specific surface area of ​​the cathode material is 7.6 m². 2 / g~16.8m 2 / g.

[0086] In this embodiment, within the range of the BET specific surface area of ​​the aforementioned cathode material, it is beneficial to improve the reactivity of the cathode material, thereby increasing its capacity and charge / discharge rate. Optionally, the BET specific surface area of ​​the cathode material is 9.87 m². 2 / g~14.9m 2 / g. Further optionally, the BET specific surface area of ​​the cathode material is 9.87m². 2 / g, 10m 2 / g、11m 2 / g、12m 2 / g、13m 2 / g、14m 2 / g or 14.9m 2 / g, or the BET specific surface area of ​​the cathode material can also be within the range between any two of the above BET specific surface areas.

[0087] In some embodiments, the pH value of the positive electrode material is 8.03 to 9.86.

[0088] In this embodiment, within the pH range of the aforementioned positive electrode material, it is beneficial to improve the charge-discharge efficiency and cycle life of the positive electrode material. Optionally, the pH value of the positive electrode material is 8.38 to 9.48. Further optionally, the pH value of the positive electrode material is 8.38, 8.4, 8.6, 8.8, 9, 9.2, 9.4, or 9.48, or the pH value of the positive electrode material can also be within the range between any two of the aforementioned pH values.

[0089] In some embodiments, the resistivity of the positive electrode material powder is 10.3 Ωcm to 369.7 Ωcm.

[0090] In this embodiment, within the range of the resistivity of the cathode material powder, it is beneficial to improve the capacity and rate performance of the cathode material. Optionally, the resistivity of the cathode material powder is 8.9 Ωcm to 26.8 Ωcm. More optionally, the resistivity of the cathode material powder is 8.9 Ωcm, 9 Ωcm, 12 Ωcm, 16 Ωcm, 20 Ωcm, 22 Ωcm, 24 Ωcm, 26 Ωcm, or 26.8 Ωcm, or the resistivity of the cathode material powder may be within the range between any two of the above-mentioned powder resistivities.

[0091] In some embodiments, the tap density of the cathode material is 0.89 g / mL to 1.09 g / mL.

[0092] In this embodiment, within the aforementioned tap density range of the positive electrode material, it is beneficial to improve the energy density of the positive electrode material. Optionally, the tap density of the positive electrode material is 0.99 g / mL to 1.05 g / mL. More optionally, the tap density of the positive electrode material is 0.99 g / mL, 1 g / mL, 1.01 g / mL, 1.02 g / mL, 1.03 g / mL, 1.04 g / mL, or 1.05 g / mL, or the tap density of the positive electrode material can also be within the range between any two of the above tap densities.

[0093] In some embodiments, the D10 particle size of the cathode material is 0.32 μm to 0.69 μm.

[0094] In some embodiments, the D50 particle size of the cathode material is 0.97 μm to 1.55 μm.

[0095] In some embodiments, the D90 particle size of the cathode material is 7.66 μm to 19.57 μm.

[0096] It is understandable that D10 particle size refers to the particle size corresponding to 10% of the cumulative particle size distribution of the cathode material, that is, 10% of the particles are smaller than D10 particle size; D50 particle size refers to the particle size corresponding to 50% of the cumulative particle size distribution of the cathode material, that is, 50% of the particles are smaller than D50 particle size; and D90 particle size refers to the particle size corresponding to 90% of the cumulative particle size distribution of the cathode material, that is, 90% of the particles are smaller than D90 particle size.

[0097] In this embodiment, the particle size of the cathode material is suitable within the range of D10, D50, and D90 particle sizes, which is beneficial to improving the capacity and compaction density of the cathode material. Optionally, the D10 particle size of the cathode material is 0.46 μm to 0.68 μm. Further, the D10 particle size of the cathode material is 0.46 μm, 0.5 μm, 0.52 μm, 0.54 μm, 0.56 μm, 0.58 μm, 0.6 μm, 0.64 μm, or 0.68 μm, or the D10 particle size of the cathode material can also be within the range between any two of the above-mentioned D10 particle sizes. Optionally, the D50 particle size of the cathode material is 1.11 μm to 1.48 μm. Further, the D50 particle size of the positive electrode material is 1.11 μm, 1.15 μm, 1.2 μm, 1.25 μm, 1.3 μm, 1.35 μm, 1.4 μm, or 1.48 μm, or the D50 particle size of the positive electrode material can also be within the range of any two of the above-mentioned D50 particle sizes. Optionally, the D90 particle size of the positive electrode material is 9.36 μm to 13.47 μm. Further, the D90 particle size of the positive electrode material is 9.36 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, or 13.47 μm, or the D90 particle size of the positive electrode material can also be within the range of any two of the above-mentioned D90 particle sizes.

[0098] In some embodiments, the carbon layer comprises 0.7% to 2.3% by mass in the cathode material.

[0099] In this embodiment, within the aforementioned mass percentage range of the carbon layer in the cathode material, it is beneficial to improve the electronic conductivity of the cathode material. Optionally, the mass percentage of the carbon layer in the cathode material is 1.02% to 1.87%. More optionally, the mass percentage of the carbon layer in the cathode material is 1.02%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, or 1.87%, or the mass percentage of the carbon layer in the cathode material can also be within the range of any two of the aforementioned mass percentages.

[0100] Please refer to Figure 1. Secondly, according to an embodiment of this application, a method for preparing a cathode material is provided, comprising the following steps:

[0101] S10: The titanium source, the first lithium source, and the phosphorus source are processed by the first reaction to obtain the preparative material.

[0102] S20: The preparatory materials and aluminum source are processed by the second reaction to obtain lithium titanium phosphate material.

[0103] S30: Lithium titanium phosphate material, along with an iron source, a second lithium source, and a carbon source, undergo a third reaction to obtain the cathode material.

[0104] In this process, the titanium element in the titanium source has a oxidation state of +3. The cathode material includes a first core particle and a first coating layer covering the surface of the first core particle. The chemical formula of the first core particle is Li. a Fe b TiAl c (PO4) d The first coating layer is a carbon layer; where 7.5≤a≤14.5, 5.0≤b≤10.0, 0.10≤c≤0.20, and a / 3+1.02×(2 / 3b+1+c)≤d≤a / 3+1.05×(2 / 3b+1+c).

[0105] In the technical solution of this application embodiment, a preliminary material is first obtained by reacting a titanium source, a first lithium source, and a phosphorus source through a first reaction. Then, the preliminary material and an aluminum source are reacted through a second reaction to obtain lithium titanium phosphate material. The lithium titanium phosphate material includes two doping elements: trivalent titanium and aluminum. It has high activity and high purity, and its primary particle size is small, which is beneficial for subsequent doping in the third reaction process. Furthermore, by introducing trivalent titanium, the ionic radius of trivalent titanium is larger than that of tetravalent titanium, making it easier to dope at iron sites. Since the doping of trivalent titanium does not require a reduction reaction, it can be carried out at lower temperatures, resulting in better doping effects and more uniform titanium diffusion. By co-doping the cathode material with aluminum and trivalent titanium, the compaction density is increased, and the ionic conductivity and capacity of the cathode material are also improved. Therefore, the cathode material obtained by the cathode material preparation method of this application embodiment has both high capacity and high compaction density.

[0106] In some embodiments, the lithium titanium phosphate material includes a second core particle and a second coating layer covering the surface of the second core particle. The chemical formula of the second core particle is Li3Ti(PO4)2, and the second coating layer includes aluminum.

[0107] In this embodiment, lithium titanium phosphate material reacts with a second lithium source, an iron source, and a carbon source to obtain a cathode material. By introducing titanium and aluminum elements, lithium and phosphate are added, which is beneficial to improving the compaction density and capacity of the cathode material.

[0108] In some embodiments, the second coating layer comprises Al2O3.

[0109] In some embodiments, the molar ratio of titanium, lithium and phosphorus in the mixture of titanium source, first lithium source and phosphorus source is 1:(3.2-3.8):(2.1-2.5).

[0110] In this embodiment, the molar ratio of titanium, lithium and phosphorus in the mixture of titanium source, first lithium source and phosphorus source is kept to be 1:(3.2~3.8):(2.1~2.5), which is beneficial to obtain second core particles with appropriate molar ratio of each element, and obtain lithium titanium phosphate material with appropriate molar ratio of each element, thereby improving the compaction density and capacity of the cathode material.

[0111] Optionally, in the mixture of titanium source, first lithium source and phosphorus source, the molar ratio of titanium element to lithium element is 1:3.2, 1:3.3, 1:3.4, 1:3.5, 1:3.6, 1:3.7 or 1:3.8. Alternatively, in the mixture of titanium source, first lithium source and phosphorus source, the molar ratio of titanium element to lithium element can also be within the range between any two of the above molar ratios.

[0112] Optionally, in the mixture of titanium source, first lithium source and phosphorus source, the molar ratio of titanium element to phosphorus element is 1:2.1, 1:2.2, 1:2.3, 1:2.4 or 1:2.5, or the molar ratio of titanium element to phosphorus element in the mixture of titanium source, first lithium source and phosphorus source can also be within the range between any two of the above molar ratios.

[0113] In some embodiments, the molar ratio of titanium in the preparative material to aluminum in the aluminum source is 1:(0.1 to 0.2).

[0114] In this embodiment, the molar ratio of titanium in the preparative material to aluminum in the aluminum source is kept within the range of 1:(0.1 to 0.2) to obtain lithium titanium phosphate material with appropriate titanium and aluminum doping amounts, thereby obtaining a cathode material with appropriate titanium and aluminum doping amounts, which is beneficial to balance the capacity and compaction density of the cathode material.

[0115] Optionally, the molar ratio of titanium in the preparatory material to aluminum in the aluminum source is 1:0.1, 1:0.11, 1:0.12, 1:0.13, 1:0.14, 1:0.15, 1:0.16, 1:0.17, 1:0.18, 1:0.19 or 1:0.2, or the molar ratio of titanium in the preparatory material to aluminum in the aluminum source can be within the range of any two of the above molar ratios.

[0116] In some embodiments, the molar ratio of titanium in the lithium titanium phosphate material, iron in the iron source, lithium in the second lithium source, and carbon in the carbon source is 1:(5-10):(5.2-11):(12-36).

[0117] In this embodiment, the molar ratio of titanium in the lithium titanium phosphate material, iron in the iron source, lithium in the second lithium source, and carbon in the carbon source is kept within the range of 1:(5-10):(5.2-11):(12-36) to obtain a cathode material with a suitable molar ratio of each element, which is beneficial to balance the capacity and compaction density of the cathode material.

[0118] Optionally, the molar ratio of titanium in the lithium titanium phosphate material to iron in the iron source is 1:5, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9, 1:9.5 or 1:10. Alternatively, the molar ratio of titanium in the lithium titanium phosphate material to iron in the iron source can also be within the range of any two of the above molar ratios.

[0119] Optionally, the molar ratio of titanium in the lithium titanium phosphate material to lithium in the second lithium source is 1:5.2, 1:5.5, 1:6, 1:7, 1:8, 1:9, 1:10 or 1:11. Alternatively, the molar ratio of titanium in the lithium titanium phosphate material to lithium in the second lithium source may also be within the range of any two of the above molar ratios.

[0120] Optionally, the molar ratio of titanium in the lithium titanium phosphate material to carbon in the carbon source is 1:12, 1:15, 1:20, 1:25, 1:30 or 1:36, or the molar ratio of titanium in the lithium titanium phosphate material to carbon in the carbon source can be within the range of any two of the above molar ratios.

[0121] In some embodiments, the temperature of the first reaction treatment is 200°C to 350°C.

[0122] Optionally, the temperature of the first reaction treatment is 200°C, 220°C, 250°C, 280°C, 300°C, 320°C, or 350°C, or the temperature of the first reaction treatment may be within any two of the above temperatures.

[0123] In some embodiments, the pressure of the first reaction treatment is 10 MPa to 20 MPa.

[0124] Optionally, the pressure of the first reaction treatment is 10 MPa, 12 MPa, 14 MPa, 16 MPa, 18 MPa or 20 MPa, or the pressure of the first reaction treatment may be within the range of any two of the above pressures.

[0125] In some embodiments, the first reaction treatment time is 5h to 15h.

[0126] Optionally, the duration of the first reaction treatment is 5h, 7h, 9h, 11h, 13h or 15h, or the duration of the first reaction treatment may be within any two of the above-mentioned times.

[0127] In this embodiment, the temperature of the first reaction treatment is kept in the range of 200℃ to 350℃, the pressure is kept in the range of 10MPa to 20MPa, and the time is kept in the range of 5h to 15h, which is conducive to the titanium source, the first lithium source and the phosphorus source being processed by the first reaction to obtain the preparative material.

[0128] In some embodiments, the titanium source includes titanium trichloride.

[0129] In this embodiment, the titanium source includes titanium trichloride. Compared with traditional cathode materials doped with tetravalent titanium, trivalent titanium has a larger ionic radius and is easier to dop at iron sites. At the same time, because the doping of trivalent titanium does not require a reduction reaction, it can be carried out at a lower temperature, and the doping effect of trivalent titanium is better, with more uniform titanium diffusion.

[0130] In some embodiments, the first lithium source includes at least one of lithium hydroxide, lithium oxide, lithium dihydrogen phosphate, and lithium monohydrogen phosphate.

[0131] In some embodiments, the phosphorus source includes at least one of lithium dihydrogen phosphate and lithium monohydrogen phosphate.

[0132] In some embodiments, the iron source includes iron phosphate.

[0133] In this embodiment, the use of the first lithium source, phosphorus source, and iron source reduces the introduction of impurities, which is beneficial for preparing high-purity preparative materials and thus for preparing high-purity cathode materials.

[0134] In some embodiments, the second lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium oxalate, and lithium acetate.

[0135] In this embodiment, the use of the second lithium source reduces the introduction of impurities, which is beneficial for preparing cathode materials with higher purity.

[0136] In some embodiments, the step of treating the titanium source, the first lithium source, and the phosphorus source with the first reaction further includes adding a reducing agent.

[0137] In this embodiment, a reducing agent is added to the titanium source, the first lithium source, and the phosphorus source during the first reaction treatment step to prevent trivalent titanium from being oxidized during the reaction.

[0138] In some embodiments, the molar ratio of the reducing agent to the titanium element in the titanium source is (0.1 to 0.2):1.

[0139] In this embodiment, within the range of the molar ratio of titanium in the reducing agent and the titanium source, it is beneficial to fully prevent trivalent titanium from being oxidized during the reaction.

[0140] Optionally, the molar ratio of the reducing agent to the titanium element in the titanium source is 0.1:1, 0.12:1, 0.14:1, 0.16:1, 0.18:1, or 0.2:1, or the molar ratio of the reducing agent to the titanium element in the titanium source can also be within the range between any two of the above molar ratios.

[0141] In some embodiments, the reducing agent includes at least one of hydrazine hydrate, sodium sulfite, and hypophosphorous acid.

[0142] In this embodiment, the selection of the aforementioned reducing agent reduces the introduction of impurities, which is beneficial for preparing cathode materials with higher purity.

[0143] In some embodiments, the titanium source, the first lithium source, and the phosphorus source are subjected to a first reaction treatment to obtain the preparative material, including the following steps:

[0144] The titanium source, the first lithium source, the phosphorus source and the reducing agent are mixed to prepare the first mixed raw material;

[0145] The first mixed raw material is added to a high-pressure reactor for high-pressure hydrothermal reaction to obtain the preparative material.

[0146] In some embodiments, the solvent for the first mixed raw material is at least one of distilled water, deionized water, or pure water.

[0147] In some embodiments, during the process of adding the first mixed raw material into a high-pressure reactor for high-pressure hydrothermal reaction, the first mixed raw material is continuously stirred.

[0148] In some embodiments, the stirring rate is 100 r / min to 300 r / min.

[0149] Optionally, the stirring rate is 100 r / min, 150 r / min, 200 r / min, 250 r / min or 300 r / min, or the stirring rate may be within any two of the above rates.

[0150] In some embodiments, during the process of adding the first mixed raw material to a high-pressure reactor for high-pressure hydrothermal reaction, a pH adjuster is used to maintain the pH value of the first mixed raw material at 10.5 to 11.5.

[0151] Optionally, during the high-pressure hydrothermal reaction of the first mixed raw material in a high-pressure reactor, a pH adjuster is used to maintain the pH value of the first mixed raw material at 10.5, 10.6, 10.7, 10.8, 10.9, 11, 11.1, 11.2, 11.3, 11.4, or 11.5. Alternatively, the pH value of the first mixed raw material may also be within the range of any two of the above pH values. It is understood that the pH values ​​in this application are all pH values ​​measured at 25°C.

[0152] In some embodiments, the pH adjuster includes ammonia.

[0153] In some embodiments, adding the first mixed raw material to a high-pressure reactor for high-pressure hydrothermal reaction to obtain the preparative material includes the following steps:

[0154] The first mixed raw material is added to a high-pressure reactor for high-pressure hydrothermal reaction;

[0155] The reaction products of the high-pressure hydrothermal reaction are washed and dried to obtain the preparative material.

[0156] In some embodiments, the reaction products of the high-pressure hydrothermal reaction are washed using countercurrent washing. The reaction products of the high-pressure hydrothermal reaction are countercurrently washed with a washing solution until the conductivity of the washing solution is less than or equal to 200 μS / cm.

[0157] In some embodiments, the washing solution for countercurrent washing is pure water or deionized water.

[0158] In some embodiments, the reaction products of the high-pressure hydrothermal reaction are dried by baking.

[0159] In some embodiments, the drying time is 8h to 24h.

[0160] In some embodiments, the drying temperature is 90°C to 110°C.

[0161] In some embodiments, the second reaction treatment of the preparative material and the aluminum source includes the following steps:

[0162] The prepared materials, dispersant and aluminum source are mixed to form a first slurry, and the pH value of the first slurry is adjusted to 8-10;

[0163] Solid product is obtained by solid-liquid separation of the first slurry;

[0164] The solid product was subjected to a first calcination treatment to obtain lithium titanium phosphate material.

[0165] In this embodiment, the second reaction process described above can prepare lithium titanium phosphate material with high activity, high purity and small primary particle size, which is beneficial to the uniform mixing of raw materials in the subsequent third reaction process, thereby improving the uniformity of the distribution of titanium and aluminum elements in the first core particles, which is beneficial to improving the compaction density and capacity of the cathode material.

[0166] Optionally, the pH value of the first slurry is 8, 8.2, 8.4, 8.6, 8.8, 9, 9.2, 9.4, 9.6, 9.8 or 10, or the pH value of the first slurry may be within the range of any two of the above pH values.

[0167] In some embodiments, the solvent for the first slurry may be selected from at least one of deionized water, pure water, or ultrapure water.

[0168] In some embodiments, the calcination temperature of the first calcination treatment is 600°C to 800°C.

[0169] Optionally, the calcination temperature of the first calcination treatment is 600℃, 620℃, 640℃, 660℃, 680℃, 700℃, 720℃, 740℃, 760℃, 780℃ or 800℃, or the calcination temperature of the first calcination treatment may be within the range of any two of the above temperatures.

[0170] In some embodiments, the calcination time for the first calcination treatment is 6h to 12h.

[0171] Optionally, the calcination time of the first calcination treatment is 6h, 7h, 8h, 9h, 10h, 11h or 12h, or the calcination time of the first calcination treatment can be within any two of the above times.

[0172] In some embodiments, the first calcination treatment is performed under a protective gas atmosphere.

[0173] In some embodiments, the protective gas includes at least one of nitrogen and argon.

[0174] In some embodiments, after the solid product undergoes a first calcination treatment, the resulting lithium titanium phosphate material is cooled to 25°C to 50°C before being discharged.

[0175] Optionally, after the solid product undergoes a first calcination treatment, the resulting lithium titanium phosphate material is cooled to 25°C, 30°C, 35°C, 40°C, 45°C, or 50°C before being discharged. Alternatively, the discharge temperature can be within the range of any two of the above temperatures.

[0176] In some embodiments, a first slurry is prepared by combining preparative materials, a dispersant, and an aluminum source, and the temperature of the first slurry is controlled at 30°C to 60°C during the process of adjusting the pH value of the first slurry to 8 to 10.

[0177] Optionally, the first slurry is prepared by combining the preparative materials, dispersant and aluminum source, and the temperature of the first slurry is controlled at 30°C, 35°C, 40°C, 45°C, 50°C, 55°C or 60°C during the process of adjusting the pH value of the first slurry to 8 to 10. Alternatively, the temperature of the first slurry can be within any two of the above-mentioned temperature ranges.

[0178] In some embodiments, adjusting the pH of the first slurry to 8-10 includes the following steps:

[0179] Carbon dioxide is introduced into the first slurry to adjust its pH to 8-10.

[0180] In this embodiment, adjusting the pH value of the first slurry to 8-10 is beneficial for forming a first slurry that includes solid products.

[0181] In some embodiments, carbon dioxide is introduced into the first slurry for 2 to 4 hours.

[0182] Optionally, the time for introducing carbon dioxide into the first slurry is 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, or 4h, or the time for introducing carbon dioxide into the first slurry can also be within any two of the above-mentioned times.

[0183] In some embodiments, the dispersant includes at least one of polyethylene glycol and polyvinyl alcohol.

[0184] In some embodiments, the dispersant includes at least one of PEG2000, PEG4000, PEG6000, PVA105, PVA203, and PVA205.

[0185] In some embodiments, the aluminum source includes sodium aluminate or an aqueous solution containing sodium aluminate.

[0186] In some embodiments, the concentration of the sodium aluminate solution is 0.02 mol / L to 0.1 mol / L.

[0187] Optionally, the concentration of the sodium aluminate solution is 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, or 0.1 mol / L, or the concentration of the sodium aluminate solution may be within any two of the above concentrations.

[0188] In some embodiments, the following steps are included before the solid product undergoes the first calcination treatment:

[0189] The solid product is washed and dried.

[0190] In some embodiments, the solid product is washed using a countercurrent washing method. The solid product is countercurrently washed with a washing solution until the conductivity of the washing solution after washing is less than or equal to 200 μS / cm.

[0191] In some embodiments, the washing solution for countercurrent washing is pure water or deionized water.

[0192] In some embodiments, the solid product is dried by spray drying.

[0193] In some embodiments, the inlet air temperature of the spray dryer is 150°C to 350°C, and the outlet air temperature of the spray dryer is 60°C to 110°C.

[0194] Optionally, the inlet air temperature for spray drying is 150℃, 180℃, 200℃, 220℃, 250℃, 280℃, 300℃, 320℃, or 350℃, or the inlet air temperature for spray drying may be within the range of any two of the above temperatures. Optionally, the outlet air temperature for spray drying is 60℃, 70℃, 80℃, 90℃, 100℃, or 110℃, or the outlet air temperature for spray drying may be within the range of any two of the above temperatures.

[0195] In some embodiments, the lithium titanium phosphate material, an iron source, a second lithium source, and a carbon source are subjected to a third reaction treatment to obtain the cathode material, comprising the following steps:

[0196] The lithium titanium phosphate material is mixed with an iron source, a second lithium source, and a carbon source to form a second slurry;

[0197] The second slurry is ground until the particle size of the particles in the second slurry is 300nm to 600nm;

[0198] The second slurry is subjected to solid-liquid separation to obtain a mixture.

[0199] The mixture is subjected to a second calcination treatment to obtain the cathode material.

[0200] In this embodiment, in the third reaction process described above, lithium titanium phosphate material is mixed with an iron source, a second lithium source, and a carbon source to form a second slurry. The second slurry is then ground until the particle size of the particles in the second slurry is 300nm to 600nm. This allows the raw materials to be mixed evenly and to have more sufficient contact with each other. As a result, during the second calcination process, the titanium and aluminum elements are more evenly distributed in the first core particles of the cathode material, which is beneficial to improving the compaction density and capacity of the cathode material.

[0201] Optionally, the second slurry is ground until the particle size of the particles in the second slurry is 300nm, 350nm, 400nm, 450nm, 500nm, 550nm or 600nm, or the particle size of the particles in the second slurry can be within the range of any two of the above particle sizes.

[0202] In some embodiments, the solvent for the second slurry is water. Specifically, the solvent for the second slurry may be selected from at least one of deionized water, pure water, or ultrapure water.

[0203] In some embodiments, the calcination temperature of the second calcination treatment is 700°C to 850°C.

[0204] Optionally, the calcination temperature of the second calcination treatment is 700℃, 720℃, 740℃, 760℃, 780℃, 800℃, 810℃, 830℃ or 850℃, or the calcination temperature of the second calcination treatment may be within the range of any two of the above temperatures.

[0205] In some embodiments, the calcination time for the second calcination treatment is 6h to 15h.

[0206] Optionally, the calcination time of the second calcination treatment is 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h, or the calcination time of the second calcination treatment can be within any two of the above times.

[0207] In some embodiments, the second calcination treatment is performed under a protective gas atmosphere.

[0208] In some embodiments, after the mixture undergoes a first calcination treatment, the resulting cathode material is cooled to 25°C to 50°C before being discharged.

[0209] Optionally, after the mixture undergoes the first calcination treatment, the resulting cathode material is cooled to 25°C, 30°C, 35°C, 40°C, 45°C, or 50°C before being discharged. Alternatively, the discharge temperature can be within the range of any two of the above temperatures.

[0210] Thirdly, embodiments of this application provide a positive electrode sheet, including a current collector and an active layer located on the surface of the current collector, wherein the active layer includes the positive electrode material described in any of the above claims or the positive electrode material prepared by the preparation method of the positive electrode material described in any of the above claims.

[0211] In this embodiment, the positive electrode sheet contains the aforementioned positive electrode material, and therefore has good electrochemical performance.

[0212] Fourthly, embodiments of this application provide a secondary battery, including the aforementioned positive electrode.

[0213] In this embodiment, the secondary battery includes the aforementioned positive electrode, thus possessing comprehensively improved electrochemical performance, and can be well applied in multiple application scenarios.

[0214] Fifthly, embodiments of this application provide an electrical device.

[0215] The electrical devices provided in this application embodiment can be, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0216] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0217] I. Preparation Method

[0218] Example 1

[0219] Methods for preparing cathode materials:

[0220] (1) Titanium trichloride, hydrazine hydrate, lithium hydroxide and lithium dihydrogen phosphate were mixed in a molar ratio of 1:0.15:1.2:2.3 and placed in a high-pressure reactor. Ammonia water was added to the high-pressure reactor to adjust the pH of the solution to 11.0. The high-pressure hydrothermal reaction was carried out at a reaction temperature of 300℃, a pressure of 17MPa and a reaction time of 10h. The stirring speed was 200r / min. The reaction product was washed and dried. The reaction product was washed countercurrently with pure water until the conductivity of the washing liquid was less than or equal to 200μS / cm. The washed reaction product was then dried at 100℃ for 16h to obtain the prepared material.

[0221] (2) The preparative materials, sodium aluminate solution and dispersant are mixed, stirred and dispersed to prepare the first slurry. The dispersant is PEG6000. The molar ratio of titanium element in the preparative materials to sodium aluminate and dispersant is 1:0.15:0.08. The concentration of sodium aluminate solution is 0.05mol / L. Carbon dioxide is introduced into the first slurry to adjust the pH value of the first slurry to 9. The carbon dioxide is introduced for 3 hours. The reaction temperature is 45℃. The first slurry is filtered to obtain a solid product. The solid product is washed and dried. The solid product is washed countercurrently with pure water until the conductivity of the washing liquid is less than or equal to 200μS / cm. The washed solid product is then spray-dried. The solid product is subjected to a first calcination treatment to obtain lithium titanium phosphate material. The calcination temperature of the first calcination treatment is 700℃ and the calcination time is 9 hours. The first calcination treatment is carried out under a nitrogen atmosphere.

[0222] (3) The lithium titanium phosphate material is mixed with iron phosphate, lithium carbonate and glucose in a molar ratio of titanium in lithium titanium phosphate, iron in iron phosphate, lithium in lithium carbonate and carbon in glucose of 1:8:8.1:24. Water is added to prepare a second slurry. The second slurry is nano-ground to a particle size of 450 nm. The second slurry is then spray-dried. The obtained material is subjected to a second calcination treatment at a calcination temperature of 800 °C for 10 h under a nitrogen atmosphere. The calcined product is then crushed, sieved and vacuum-packed to obtain the cathode material.

[0223] Cathode material:

[0224] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 10.9 Fe8TiAl 0.15 (PO4) 10.3 .

[0225] The SEM results of the cathode material in this embodiment are shown in Figure 1 below. It can be seen that the cathode material consists of spherical particles with good dispersibility.

[0226] Example 2

[0227] Methods for preparing cathode materials:

[0228] The preparation method of the positive electrode material in Example 2 is the same or similar to that in Example 1. The only difference is that in step (1) of this example, the titanium source is titanium trichloride, the first lithium source is lithium acetate, the reducing agent is sodium sulfite, and the phosphorus source is lithium dihydrogen phosphate.

[0229] Cathode material:

[0230] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 10.9 Fe8TiAl 0.15 (PO4) 10.3 .

[0231] The SEM results of the cathode material in this embodiment are shown in Figure 2 below. It can be seen that the cathode material consists of spherical particles with good dispersibility.

[0232] Example 3

[0233] Methods for preparing cathode materials:

[0234] The preparation method of the positive electrode material in Example 3 is the same or similar to that in Example 1, except that: in step (2), the aluminum source is sodium aluminate and the dispersant is polyvinyl alcohol; in step (3), the second lithium source is lithium oxalate and the carbon source is sucrose.

[0235] Cathode material:

[0236] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 10.9 Fe8TiAl 0.15 (PO4) 10.3 .

[0237] Example 4

[0238] Methods for preparing cathode materials:

[0239] The preparation method of the positive electrode material in Example 4 is the same or similar to that in Example 1, except that in step (1), titanium trichloride, hydrazine hydrate, lithium hydroxide and lithium dihydrogen phosphate are mixed in a molar ratio of 1:0.1:1.1:2.1.

[0240] Cathode material:

[0241] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 10.7 Fe8TiAl 0.15 (PO4) 10.1 .

[0242] Example 5

[0243] Methods for preparing cathode materials:

[0244] The preparation method of the positive electrode material in Example 5 is the same or similar to that in Example 1, except that in step (1), titanium trichloride, hydrazine hydrate, lithium hydroxide and lithium dihydrogen phosphate are mixed in a molar ratio of 1:0.2:1.3:2.5.

[0245] Cathode material:

[0246] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 11.0 Fe8TiAl 0.15 (PO4) 10.5 .

[0247] Example 6

[0248] Methods for preparing cathode materials:

[0249] The preparation method of the positive electrode material in Example 6 is the same or similar to that in Example 1, except that in step (1), titanium trichloride, hydrazine hydrate, lithium hydroxide and lithium dihydrogen phosphate are mixed in a molar ratio of 1:0.1:1.1:2.5.

[0250] Cathode material:

[0251] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 10.9 Fe8TiAl 0.15 (PO4) 10.5 .

[0252] Example 7

[0253] Methods for preparing cathode materials:

[0254] The preparation method of the positive electrode material in Example 7 is the same or similar to that in Example 1, except that in step (1), titanium trichloride, hydrazine hydrate, lithium hydroxide and lithium dihydrogen phosphate are mixed in a molar ratio of 1:0.1:1.3:2.5.

[0255] Cathode material:

[0256] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 11.0 Fe8TiAl 0.15 (PO4) 10.5 .

[0257] Example 8

[0258] Methods for preparing cathode materials:

[0259] The preparation method of the positive electrode material in Example 8 is the same or similar to that in Example 1, except that in step (1), titanium trichloride, hydrazine hydrate, lithium hydroxide and lithium dihydrogen phosphate are mixed in a molar ratio of 1:0.05:1:2.

[0260] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 10.8 Fe8TiAl 0.15 (PO4) 10 .

[0261] Example 9

[0262] Methods for preparing cathode materials:

[0263] The preparation method of the positive electrode material in Example 9 is the same or similar to that in Example 1, except that in step (1), titanium trichloride, hydrazine hydrate, lithium hydroxide and lithium dihydrogen phosphate are mixed in a molar ratio of 1:0.3:1.5:3.

[0264] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 11.2 Fe8TiAl 0.15 (PO4) 11 .

[0265] Example 10

[0266] The preparation method of the positive electrode material in Example 10 is the same or similar to that in Example 1, except that in step (2), the molar ratio of titanium element to sodium aluminate and dispersant in the preparative material is 1:0.1:0.05.

[0267] Cathode material:

[0268] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 10.9 Fe8TiAl 0.10 (PO4) 10.3 .

[0269] Example 11

[0270] The preparation method of the positive electrode material in Example 11 is the same or similar to that in Example 1, except that in step (2), the molar ratio of titanium element to sodium aluminate and dispersant in the preparative material is 1:0.2:0.1.

[0271] Cathode material:

[0272] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 10.9 Fe8TiAl 0.20 (PO4) 10.3 .

[0273] Example 12

[0274] The preparation method of the positive electrode material in Example 12 is the same or similar to that in Example 1. The only difference is that in step (3), the aluminum-coated lithium titanium phosphate material is mixed with iron phosphate, lithium carbonate and glucose in a molar ratio of titanium in lithium titanium phosphate material, iron in iron phosphate, lithium in lithium carbonate and carbon in glucose of 1:5:5.2:12.

[0275] Cathode material:

[0276] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 8.7 Fe5TiAl 0.15 (PO4) 7.3 .

[0277] Example 13

[0278] The preparation method of the positive electrode material in Example 13 is the same or similar to that in Example 1, except that in step (3), the aluminum-coated lithium titanium phosphate material is mixed with iron phosphate, lithium carbonate and glucose in a molar ratio of titanium in lithium titanium phosphate material, iron in iron phosphate, lithium in lithium carbonate and carbon in glucose of 1:10:11:36.

[0279] Cathode material:

[0280] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 14.5 Fe 10 TiAl 0.15 (PO4) 12.3 .

[0281] Example 14

[0282] The preparation method of the positive electrode material in Example 14 is the same or similar to that in Example 1. The only difference is that in step (3), the aluminum-coated lithium titanium phosphate material is mixed with iron phosphate, lithium carbonate and glucose in a molar ratio of titanium in lithium titanium phosphate material, iron in iron phosphate, lithium in lithium carbonate and carbon in glucose of 1:5:11:36.

[0283] Cathode material:

[0284] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 14.5 Fe5TiAl 0.15 (PO4) 8.5.

[0285] Example 15

[0286] The preparation method of the positive electrode material in Example 15 is the same or similar to that in Example 1. The only difference is that in step (3), the aluminum-coated lithium titanium phosphate material is mixed with iron phosphate, lithium carbonate and glucose in a molar ratio of titanium in lithium titanium phosphate material, iron in iron phosphate, lithium in lithium carbonate and carbon in glucose of 1:8:4:6.

[0287] Cathode material:

[0288] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 7.5 Fe8TiAl 0.15 (PO4) 10.3 .

[0289] Example 16

[0290] The preparation method of the cathode material in Example 16 is the same or similar to that in Example 1, except that in step (3), the aluminum-coated lithium titanium phosphate material is mixed with iron phosphate, lithium carbonate and glucose in a molar ratio of titanium in lithium titanium phosphate material, iron in iron phosphate, lithium in lithium carbonate and carbon in glucose of 1:8:7:48.

[0291] Cathode material:

[0292] In this embodiment, the cathode material includes a first core particle and a carbon layer coating the surface of the first core particle. The chemical formula of the first core particle is Li. 14.5 Fe8TiAl 0.15 (PO4) 12.3 .

[0293] Example 17

[0294] The preparation method of the positive electrode material in Example 17 is the same or similar to that in Example 1, except that: in step (1), the reaction temperature of the high-pressure hydrothermal reaction is 200℃, the reaction pressure is 10MPa, the reaction time is 5h, the stirring speed is 100r / min, and the reaction product is dried at 90℃ for 24h; in step (2), carbon dioxide is introduced into the first slurry to adjust the pH value of the first slurry to 8, the time for introducing carbon dioxide is 2h, the reaction temperature is 30℃, the washed solid product is spray-dried, the calcination temperature of the first calcination treatment is 600℃, and the calcination time is 6h; in step (3), the second slurry is nano-ground to a particle size of 300nm, the temperature of the second calcination treatment is 700℃, and the time is 6h.

[0295] Example 18

[0296] The preparation method of the positive electrode material in Example 18 is the same or similar to that in Example 1, except that: in step (1), the reaction temperature of the high-pressure hydrothermal reaction is 350°C, the reaction pressure is 20MPa, the reaction time is 15h, the stirring speed is 300r / min, and the reaction product is dried at 110°C for 8h; in step (2), carbon dioxide is introduced into the first slurry to adjust the pH value of the first slurry to 10, the carbon dioxide is introduced for 4h, the reaction temperature is 60°C, the washed solid product is spray-dried, the calcination temperature of the first calcination treatment is 800°C, and the calcination time is 12h; in step (3), the second slurry is nano-ground to a particle size of 600nm, the temperature of the second calcination treatment is 850°C, and the time is 15h.

[0297] Comparative Example 1

[0298] Methods for preparing cathode materials:

[0299] The preparation method of the cathode material in Comparative Example 1 is the same or similar to that in Example 1, the only difference is that the titanium source in step (1) is titanium tetrachloride.

[0300] Comparative Example 2

[0301] Methods for preparing cathode materials:

[0302] The preparation method of the cathode material in Comparative Example 2 is the same or similar to that in Example 1, except that no aluminum source is added in step (2).

[0303] The performance of the cathode materials in the above embodiments and comparative examples was tested. Elemental composition was determined by ICP-OES; powder resistivity was measured using the four-probe method at a pressure of 10 MPa; compaction density was measured under a pressure of 3 tons; specific surface area was determined by the gas adsorption BET method; pH value was tested according to GB / T 9724, General Rules for pH Value Determination of Chemical Reagents; free lithium content was determined by potentiometric titration; tap density was tested using a tap density meter with 5000 vibrations; D10, D50, and D90 particle sizes were measured using a laser particle size analyzer; and C and S contents were measured using a carbon-sulfur analyzer.

[0304] The test results are shown in Tables 1 to 3 below:

[0305] Table 1

[0306] Table 2

[0307] Table 3

[0308] II. Testing Methods

[0309] Secondary battery property test

[0310] The positive electrode materials prepared in the various embodiments and comparative examples were mixed with conductive carbon black and PVDF binder at a mass ratio of 90:5:5, and coated onto a 12μm thick aluminum foil. The electrode sheets were then dried in an oven at 110℃ for 10 hours. The dried electrode sheets were then punched into positive electrode discs with a diameter of 15mm and compacted to a density of 2.5g / cm³. 3 The cells were rolled and assembled in a glove box manufactured by Wig Gas Purification Technology (Suzhou) Co., Ltd., using a 16mm diameter lithium sheet as the counter electrode and 1M LiPF6 dissolved in EC:EMC:DEC in a volume ratio of 1:1:1. The resulting coin cells were then subjected to charge-discharge performance testing.

[0311] The battery performance testing system (model: CT3002A) from Wuhan Landian Electronics Technology Co., Ltd. was used. The test temperature was 25℃, and the voltage range was 2V~3.75V. Tests were conducted at 0.2C and 1C rates, respectively; and at a voltage range of 2V~3.1V, tests were conducted at 0.2C and 1C rates, respectively. The test results are shown in Table 4 below.

[0312] Table 4

[0313] III. Analysis of Test Results for Each Embodiment and Comparative Example

[0314] As shown in Tables 1-3, the compaction density of the lithium iron phosphate cathode material provided in this application is 2.41 g / mL to 2.67 g / mL, while the compaction density of the lithium iron phosphate cathode material obtained in Comparative Example 1 is 2.36 g / mL. The introduction of aluminum and tetravalent titanium into the cathode material in Comparative Example 1 resulted in a lower compaction density. The lithium iron phosphate cathode material provided in this application, through co-doping with aluminum and trivalent titanium, exhibits a higher compaction density. The compaction density of the lithium iron phosphate cathode material obtained in Comparative Example 2 is 2.59 g / mL. Since aluminum was not introduced into the lithium iron phosphate cathode material in Comparative Example 2, the reduction in compaction density caused by metal doping was mitigated. The compaction densities of Examples 1-14 and Examples 16-18 are comparable to those of the lithium iron phosphate cathode material in Comparative Example 2. Comparison with Comparative Examples 1 and 2 shows that the cathode material provided in this application has an improved compaction density.

[0315] As shown in Tables 1-3, the powder resistivity of the lithium iron phosphate cathode materials obtained in Examples 1-7 and Examples 10-11 is 8.9 Ωcm to 10.9 Ωcm, while the powder resistivity of the lithium iron phosphate cathode material obtained in Example 12 is 26.8 Ωcm. The powder resistivity of the lithium iron phosphate cathode material obtained in Example 8 is 19.6 Ωcm, and the powder resistivity of the lithium iron phosphate cathode material obtained in Example 9 is 24.6 Ωcm. Compared to other examples, the amount of titanium trichloride added in Example 8 is greater than the range value, and the amount of titanium trichloride added in Example 9 is less than the range value, both of which cause phase impurities in lithium iron phosphate, resulting in higher powder resistivity of the lithium iron phosphate cathode materials obtained in Examples 8 and 9. Because the amount of carbon source added is less than the range value, the powder resistivity of the lithium iron phosphate cathode material obtained in Example 15 is also higher. Furthermore, due to the lower carbon content, the particles of the lithium iron phosphate cathode material in Example 15 are more prone to growth, resulting in a higher compaction density. In Comparative Example 1, tetravalent titanium was used as the titanium source. The conductivity of the resulting lithium iron phosphate cathode material was lower compared to the lithium iron phosphate cathode material prepared using trivalent titanium as the titanium source. Therefore, compared to Comparative Example 1, the powder resistivity of the lithium iron phosphate cathode materials obtained in Examples 1-14 and Examples 16-18 was lower. In Comparative Example 2, no aluminum source was added, and the resulting lithium iron phosphate cathode material was not coated with alumina. Since alumina has poor conductivity, the lithium iron phosphate cathode material obtained in Comparative Example 2 had a lower powder resistivity.

[0316] As can be seen from the data in Table 4, the specific capacity of the first charge at 0.2C (2V to 3.75V) tested in each embodiment is 161.1mAh / g to 169.9mAh / g, the specific capacity of the first charge at 0.2C (2V to 3.1V) is 156.7mAh / g to 166.8mAh / g, the specific capacity of the first discharge at 0.2C (2V to 3.1V) is 32.1mAh / g to 36.1mAh / g, the specific capacity of the first charge at 1C (2V to 3.75V) is 153.2mAh / g to 161.7mAh / g, and the specific capacity of the first discharge at 1C (2V to 3.1V) is 27.8mAh / g to 32.2mAh / g.

[0317] Compared with Comparative Example 1, the aluminum and trivalent titanium co-doped lithium iron phosphate cathode material provided in this application has higher discharge and charge specific capacities, especially the discharge specific capacity at 2V to 3.1V. The aluminum and trivalent titanium co-doped lithium iron phosphate cathode material provided in this application exhibits high discharge specific capacity at low voltages (2V to 3.1V), which can significantly improve the driving range of new energy vehicles in practical applications, ensuring a high driving range even when the battery is low. Simultaneously, the higher capacity at low voltages can effectively alleviate the electrochemical corrosion problem of the cathode current collector aluminum foil at low voltages. In Comparative Example 1, tetravalent titanium is used as the titanium source, which easily leads to the formation of impurity phases in the cathode material. The particle radius of tetravalent titanium is smaller than that of trivalent titanium, making it easier for it to mix with lithium, resulting in capacity decay.

[0318] As can be seen from the various embodiments and Comparative Example 2, the aluminum and trivalent titanium co-doped lithium iron phosphate cathode material provided in this application has higher discharge specific capacity and charge specific capacity, especially the discharge specific capacity of 2V to 3.1V.

[0319] As can be seen from the data in Tables 1 to 4, the aluminum and trivalent titanium co-doped lithium iron phosphate cathode material provided in this application, while also coated with carbon, can simultaneously possess high capacity and high compaction density, thus exhibiting high discharge and charge specific capacities at 0.2C and 1C rates. The 0.2C initial charge specific capacities (2V–3.1V) obtained in Examples 8 and 9, respectively, are 156.7 mAh / g and 157.5 mAh / g, lower than Comparative Example 1. This is because in Example 8, the amount of titanium trichloride added exceeded the range, resulting in a higher content of impurity phases and lower crystal structure integrity of the obtained lithium iron phosphate cathode material, thus causing a lower specific capacity. In Example 9, the amount of titanium trichloride added was less than the range, leading to a lower lithium-ion mobility, thus causing a lower specific capacity.

[0320] A comparison of Examples 1, 4-7, 8, and 9 shows that in the preparation method of the cathode material provided in this application, maintaining the molar ratio of titanium element in the titanium source, reducing agent, lithium element in the first lithium source, and phosphorus element in the phosphorus source at 1:(0.1-0.2):(3.3-3.8):(2.1-2.5) is beneficial for the cathode material to have both high capacity and high compaction density.

[0321] A comparison of Examples 1, 12-14 and 15 and 16 shows that in the preparation method of the cathode material provided in this application, maintaining the molar ratio of titanium, iron, lithium and carbon elements in the lithium titanium phosphate material, iron source, second lithium source and carbon source at 1:(5-10):(5.2-11):(2-6) is beneficial for the cathode material to have both high capacity and high compaction density.

[0322] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A positive electrode material, characterized in that, The cathode material includes a first core particle and a first coating layer covering the surface of the first core particle. The chemical formula of the first core particle is Li. a Fe b TiAl c (PO4) d The first coating layer is a carbon layer; wherein, 7.5≤a≤14.5, 5≤b≤10, 0.1≤c≤0.2, a / 3+1.02×(2 / 3b+1+c)≤d≤a / 3+1.05×(2 / 3b+1+c).

2. The cathode material according to claim 1, characterized in that, 8 ≤ a ≤ 14.5; and / or, The compaction density of the positive electrode material is 2.45 g / cm³. 3 ~2.6g / cm 3 ; and / or, The carbon layer comprises 0.7% to 2.3% by mass in the cathode material.

3. A method for preparing a positive electrode material, characterized in that, The steps include the following: The titanium source, the first lithium source, and the phosphorus source are subjected to a first reaction treatment to obtain the preparative material; The prepared materials and aluminum source are subjected to a second reaction treatment to obtain lithium titanium phosphate material; The lithium titanium phosphate material, along with an iron source, a second lithium source, and a carbon source, undergoes a third reaction treatment to obtain the cathode material. The titanium element in the titanium source has a oxidation state of +3. The cathode material includes a first core particle and a first coating layer covering the surface of the first core particle. The chemical formula of the first core particle is Li. a Fe b TiAl c (PO4) d The first coating layer is a carbon layer; wherein, 7.5≤a≤14.5, 5≤b≤10, 0.1≤c≤0.2, a / 3+1.02×(2 / 3b+1+c)≤d≤a / 3+1.05×(2 / 3b+1+c).

4. The method for preparing the cathode material according to claim 3, characterized in that, The lithium titanium phosphate material includes a second core particle and a second coating layer covering the surface of the second core particle. The chemical formula of the second core particle is Li3Ti(PO4)2, and the second coating layer includes aluminum.

5. The method for preparing the cathode material according to claim 3, characterized in that, In the mixture of the titanium source, the first lithium source, and the phosphorus source, the molar ratio of titanium, lithium, and phosphorus is 1:(3.2–3.8):(2.1–2.5); and / or, The molar ratio of titanium in the prepared material to aluminum in the aluminum source is 1:(0.1-0.2); and / or, The molar ratio of titanium in the lithium titanium phosphate material, iron in the iron source, lithium in the second lithium source, and carbon in the carbon source is 1:(5-10):(5.2-11):(12-36); and / or, The temperature of the first reaction treatment is 200℃~350℃; and / or, The pressure of the first reaction treatment is 10 MPa to 20 MPa; and / or, The first reaction treatment lasts for 5 to 15 hours; and / or, The titanium source includes titanium trichloride; and / or, The first lithium source includes at least one of lithium hydroxide, lithium oxide, lithium dihydrogen phosphate, and lithium monohydrogen phosphate; and / or, The phosphorus source includes at least one of lithium dihydrogen phosphate and lithium monohydrogen phosphate; and / or, The iron source includes iron phosphate; and / or, The second lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium oxalate, and lithium acetate.

6. The method for preparing the cathode material according to claim 3, characterized in that, The step of treating the titanium source, the first lithium source, and the phosphorus source with the first reaction also includes: adding a reducing agent; The molar ratio of the reducing agent to the titanium element in the titanium source is (0.1–0.2):1; and / or, The reducing agent includes at least one of hydrazine hydrate, sodium sulfite, and hypophosphorous acid.

7. The method for preparing the cathode material according to claim 3, characterized in that, The second reaction treatment of the preparative materials and aluminum source includes the following steps: The prepared materials, dispersant and aluminum source are mixed to form a first slurry, and the pH value of the first slurry is adjusted to 8-10; The first slurry was subjected to solid-liquid separation to obtain a solid product; The solid product is subjected to a first calcination treatment to obtain the lithium titanium phosphate material.

8. The method for preparing the cathode material according to claim 3, characterized in that, The lithium titanium phosphate material, along with an iron source, a second lithium source, and a carbon source, undergoes a third reaction treatment to obtain the cathode material, comprising the following steps: The lithium titanium phosphate material, the iron source, the second lithium source, and the carbon source are mixed to form a second slurry; The second slurry is ground until the particle size of the particles in the second slurry is 300nm to 600nm; The second slurry is subjected to solid-liquid separation to obtain a mixture. The mixture is subjected to a second calcination treatment to obtain the cathode material; The calcination temperature in the second calcination treatment is 700℃~850℃; and / or, The calcination time in the second calcination treatment is 6h to 15h.

9. A positive electrode sheet, characterized in that, It includes a current collector and an active layer located on the surface of the current collector, wherein the active layer comprises a positive electrode material prepared by the method of preparing the positive electrode material according to any one of claims 1 to 2 or any one of claims 3 to 8.

10. A secondary battery, characterized in that, Includes the positive electrode sheet as described in claim 9.

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