Positive electrode composite, method for producing the same, and use thereof

Abstract

The application relates to the technical field of lithium batteries, in particular to a positive electrode composite material and a preparation method and application thereof. The surface energy of the (003) crystal face of the positive electrode composite material is less than or equal to 1.023 J / m 2 The (003) crystal face of the positive electrode composite material provided by the application has low surface energy, can inhibit particle breakage, reduce the number of crystal boundaries, and improve cycle performance.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a positive electrode composite material, its preparation method, and its application. Background Technology

[0002] With the rollout of the timetable for banning the sale of gasoline-powered vehicles, the promotion and application of new energy vehicles is inevitable. Lithium-ion batteries are the core component of new energy vehicles, and cathode materials are the decisive factor affecting their performance. Currently, ternary cathode materials face the following two problems, impacting their practical application and user experience:

[0003] 1) Compared to phosphate-based cathode materials, ternary cathode materials have a shorter cycle life. This is mainly due to volume expansion and contraction during charging and discharging, particle breakage leading to the continuous formation of the passivation layer (CEI film) on the cathode surface, and loss of electrical contact, resulting in the loss of active lithium and the formation of dead lithium. The main reason for particle breakage is the presence of numerous grain boundaries in ternary cathode materials, where significant stress exists during lithium insertion / extraction. 2) The global reserves of cobalt, the main raw material used in ternary cathode materials, are low, making it difficult to meet the rapid development of new energy vehicles. Therefore, low-cobalt ternary cathode materials have been developed. However, the reduction in cobalt content in low-cobalt ternary cathode materials leads to a decrease in material conductivity, rate performance, and interface stability, an increase in impedance during cycling, and swelling; moreover, the residual alkali content increases. Therefore, conventional low-cobalt or cobalt-free ternary cathode materials cannot meet the requirements of new energy vehicles. Summary of the Invention

[0004] Therefore, it is necessary to provide a cathode composite material, its preparation method and application. The cathode composite material is a single crystal material with directional growth characteristics, which can suppress particle breakage, reduce the number of grain boundaries and improve cycle performance.

[0005] In a first aspect, this application provides a positive electrode composite material, wherein the surface energy of the (003) crystal plane of the positive electrode composite material is ≤1.023 J / m. 2 .

[0006] In some embodiments, the cathode composite material is a single-crystal cathode composite material.

[0007] In some embodiments, the positive electrode composite material includes:

[0008] A cathode material, comprising a ternary cathode material and a metal composite oxide doped in the ternary cathode material, wherein the metal composite oxide comprises tin oxide and tungsten oxide;

[0009] A coating layer is applied to the surface of the positive electrode material, and the coating layer is made of materials including Co3O4 and Li. 1+m Al m Ti 2-m (PO4)3, where 0.1≤m≤1.

[0010] In some embodiments, the positive electrode composite material satisfies at least one of the following characteristics:

[0011] 1) The molar mass ratio of the metal composite oxide to the ternary cathode material is (0.1-0.3):100;

[0012] 2) In the metal composite oxide, the molar ratio of tin oxide to tungsten oxide is (1-2):3;

[0013] 3) In the coating layer, the Co3O4 and Li 1+m Al m Ti 2-m The molar ratio of (PO4)3 is (1-2):3;

[0014] 4) The thickness of the coating layer is 5 nm to 100 nm;

[0015] 5) During the formation of the coating layer, the Co3O4 and the Li 1+m Al m Ti 2-m (PO4)3 reacts to form LiCoO2, wherein the Li 1+m Al m Ti 2-m Al, Ti and PO4 in (PO4)3 3- It enters the LiCoO2 lattice.

[0016] In some embodiments, the molecular formula of the ternary cathode material is Li. z Ni a Co b Mn (1-a-b) O2, the molecular formula of the metal composite oxide is dSnO2·WO3, and the molecular formula of the cathode material is Li. z Ni a Co b Mn (1-a-b) (dSnO2·WO3) c O2; where 1.02≤z≤1.1, 0.6≤a≤0.95, 0.05≤b≤0.4, 0.001≤c≤0.003, 1 / 3≤d≤2 / 3.

[0017] Secondly, this application provides a method for preparing the positive electrode composite material as described in the first aspect, comprising the following steps:

[0018] A nickel source, a cobalt source, a manganese source, and the aforementioned metal composite oxide are dispersed in a first solvent to form a first slurry, and the first slurry is dried to form a first material;

[0019] The first material is mixed with a lithium source and calcined to prepare the cathode material;

[0020] The Co3O4 and the Li 1+m Al m Ti 2-m (PO4)3 is dispersed in a second solvent to form a second slurry, and the second slurry is dried to form a second material;

[0021] The positive electrode material is mixed with the second material and calcined to form the coating layer on the surface of the positive electrode material.

[0022] In some implementations, at least one of the following features is satisfied:

[0023] 1) The metal composite oxide is prepared by the following method:

[0024] Tin oxide and tungsten oxide are dispersed in a third solvent to form a third slurry, and the third slurry is dried to obtain the metal composite oxide;

[0025] 2) The conditions for roasting the first material and the lithium source mixture include: roasting atmosphere is oxygen-containing gas, roasting temperature is 850℃~950℃, and roasting time is 10h~16h.

[0026] 3) The conditions for calcining the positive electrode material and the second material mixture include: the calcination atmosphere is an oxygen-containing gas, the calcination temperature is 850℃~950℃, and the calcination time is 6h~12h;

[0027] 4) The temperature for drying the first slurry is 550℃~650℃;

[0028] 5) The drying temperatures for the second slurry and the third slurry are independently 200℃~350℃.

[0029] In some embodiments, the preparation method satisfies at least one of the following characteristics:

[0030] 1) The particle size D of the first slurry, the second slurry, and the third slurry 50 Each is independently less than or equal to 0.1 μm;

[0031] 2) The particle size of the positive electrode material is 3.2 μm ≤ D 50 ≤4.2μm;

[0032] 3) D of the second material 50 ≤0.3μm;

[0033] 4) The particle size of the positive electrode composite material is 3.4 μm ≤ D 50 ≤4.2μm.

[0034] In some embodiments, the preparation method satisfies at least one of the following characteristics:

[0035] 1) The nickel source includes nickel hydroxide and / or nickel oxide;

[0036] 2) The cobalt source includes cobalt hydroxide and / or cobalt oxide;

[0037] 3) The manganese source includes one or more of manganese carbonate, manganese trioxide, and manganese dioxide;

[0038] 4) The lithium source includes one or more of lithium hydroxide, lithium carbonate, and lithium acetate;

[0039] 5) The molar ratio of the first material to the lithium source is 1:(1.02~1.10);

[0040] 6) The molar mass ratio of the positive electrode material to the second material is 100:(1-3).

[0041] Thirdly, this application provides a battery comprising the positive electrode composite material described in the first aspect.

[0042] The cathode composite material (003) provided in this application has a low surface energy of the crystal plane, which can promote the directional growth of the cathode composite material along the (003) crystal plane, realize the directional growth of the cathode composite material, form a slender single crystal cathode composite material, reduce the number of grain boundaries and the stress of the lithium insertion / extraction process, suppress the breakage of cathode composite material particles, and improve the battery cycle performance; at the same time, it can also improve the lithium ion diffusion ability, thereby improving the battery rate performance. Attached Figure Description

[0043] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0044] Figure 1 This is a schematic diagram of a method for preparing a positive electrode composite material according to one embodiment;

[0045] Figures 2-5The images are scanning electron microscope (SEM) images of the positive electrode composite materials prepared in Example 1 and Comparative Examples 1-3. Detailed Implementation

[0046] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0047] 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 belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0048] the term

[0049] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0050] "Metal composite oxides" are complex oxides composed of two or more metal oxides. For example, iron(Fe3O4) can be considered as a metal composite oxide (FeO·Fe2O3) formed by iron(FeO) and ferric(Fe2O3).

[0051] Traditional ternary cathode materials contain numerous grain boundaries with high stress, leading to easy particle breakage. Furthermore, the low reserves of cobalt, a key element in ternary cathode materials, limit their development, resulting in the development of low-cobalt or cobalt-free ternary cathode materials. However, low-cobalt or cobalt-free ternary cathode materials exhibit lower conductivity, rate performance, interfacial stability, and DCR, higher residual alkali content, and are prone to swelling. Therefore, this application provides a cathode composite material to prevent particle breakage in ternary cathode materials, improve their cycle performance and rate performance, and is particularly suitable for preparing low-cobalt or cobalt-free ternary cathode materials.

[0052] In a first aspect, this application provides a cathode composite material, wherein the surface energy of the (003) crystal plane of the cathode composite material is ≤1.023 J / m. 2 .

[0053] The cathode composite material (003) provided in this application has a low surface energy of the crystal plane, which can promote the directional growth of the cathode composite material along the (003) crystal plane, realize the directional growth of the cathode composite material, form a slender single crystal cathode composite material, reduce the number of grain boundaries and the stress of the lithium insertion / extraction process, suppress the breakage of cathode composite material particles, and improve the battery cycle performance; at the same time, it can also improve the lithium ion diffusion ability, thereby improving the battery rate performance.

[0054] In some embodiments, the cathode composite material is a single-crystal cathode composite material.

[0055] In some embodiments, the cathode composite material includes: a cathode material and a coating layer covering the surface of the cathode material; the cathode material includes a ternary cathode material and a metal composite oxide doped in the ternary cathode material; the metal composite oxide includes tin oxide and tungsten oxide; the coating layer material includes Co3O4 and Li. 1+m Al m Ti 2-m (PO4)3, where 0.1≤m≤1.

[0056] The cathode composite material provided in this application is doped with a metal composite oxide formed by tin oxide and tungsten oxide, thereby reducing the surface energy of the (003) crystal plane. Furthermore, by simultaneously employing Co3O4 and Li... 1+m Al m Ti 2-m (PO4)3 was used as a coating material, Li 1+m Al m Ti 2-m (PO4)3 can effectively enhance interfacial activity and improve battery rate performance; Co3O4 can react with residual alkali on the surface, which not only reduces the residual alkali content, but also the generated LiCoO2, along with the internal cathode material (matrix) of the coating layer, has a layered structure, which is beneficial to improving the adhesion between the coating layer and the substrate and reducing their contact resistance, thereby improving the cycle performance of the battery. Furthermore, during the formation of the coating layer, Li... 1+m Al m Ti 2-m Al, Ti and PO4 in (PO4)3 3- It can enter the LiCoO2 lattice, thereby stabilizing its crystal structure.

[0057] In this application, m can be any value between 0.1 and 1, for example, m can be 0.2, 0.4, 0.6, 0.8, or 1.0. In this application, the selection of the ternary cathode material is not limited; commonly used ternary cathode materials in the lithium battery field can be selected, especially suitable for selecting low-cobalt or cobalt-free ternary cathode materials. In some embodiments, the molecular formula of the ternary cathode material is Li.z Ni a Co b Mn (1-a-b) O2, where 1.02≤z≤1.1, 0.6≤a≤0.95, 0.05≤b≤0.4.

[0058] In some embodiments, the molecular formula of the metal composite oxide is dSnO2·WO3, where 1 / 3 ≤ d ≤ 2 / 3.

[0059] In some implementations, the molecular formula of the cathode material is Li. z Ni a Co b Mn (1-a-b) (dSnO2·WO3) c O2, where 1.02≤z≤1.1, 0.6≤a≤0.95, 0.05≤b≤0.4, 0.001≤c≤0.003. By controlling the atomic number of each element in the cathode material within this range, compared to cathode materials without metal composite oxides, the surface energy of the cathode composite material on the (003) crystal plane can be reduced (by at least 0.2 J / m). 2 (Above), thereby promoting the directional growth of the cathode composite material along the (003) crystal plane.

[0060] In some embodiments, the molar ratio of the metal composite oxide to the ternary cathode material is (0.1–0.3):100, for example, 0.1:100, 0.15:100, 0.2:100, and 0.25:100. By adjusting the molar ratio of the metal composite oxide to the ternary cathode material within this range, it is possible to ensure the generation of materials oriented along the (003) crystal plane without significantly affecting the relative capacity.

[0061] In some embodiments, the molar ratio of tin oxide to tungsten oxide in the metal composite oxide is (1-2):3, for example, 1:3, 1.2:3, 1.5:3, or 1.8:3. By adjusting the molar ratio of tin oxide to tungsten oxide within this range, the radially oriented growth of the cathode composite material can be effectively controlled.

[0062] In some embodiments, Co3O4 and Li are present in the coating layer. 1+m Al m Ti 2-m The molar ratio of (PO4)3 is (1-2):3, for example, 1:3, 1.2:3, 1.5:3, 1.8:3. This is achieved by combining Co3O4 and Li... 1+m Al m Ti 2-mBy controlling the molar ratio of (PO4)3 within this range, sufficient adhesion between the coating layer and the internal cathode material can be ensured while improving the rate performance of the cathode composite material.

[0063] In some embodiments, the thickness of the coating layer is 5 nm to 100 nm, for example, 10 nm, 30 nm, 50 nm, or 100 nm. By controlling the thickness of the coating layer within the above range, the cycle performance of the cathode composite material can be improved without affecting its specific capacity.

[0064] Please see Figure 1 Secondly, this application provides a method for preparing the positive electrode composite material as described in the first aspect, comprising the following steps:

[0065] S100: A nickel source, a cobalt source, a manganese source, and a metal composite oxide are dispersed in a first solvent to form a first slurry, and the first slurry is dried to form a first material;

[0066] S200: The first material is mixed with a lithium source and calcined to prepare the cathode material;

[0067] S300: Combining Co3O4 and Li 1+m Al m Ti 2-m (PO4)3 is dispersed in a second solvent to form a second slurry, and the second slurry is dried to form a second material;

[0068] S400: The cathode material is mixed with the second material and calcined to form a coating layer on the surface of the cathode material.

[0069] S100: Preparation of the first material.

[0070] In some embodiments, the step of preparing the first material includes:

[0071] S101: Tin oxide and tungsten oxide are dispersed in a third solvent to form a third slurry, and the third slurry is dried to obtain a metal composite oxide;

[0072] S102: Disperse nickel source, cobalt source, manganese source and metal composite oxide in a first solvent to form a first slurry, and dry the first slurry to form a first material.

[0073] In some embodiments, the particle size D of the first slurry and the third slurry 50 Each is independently less than or equal to 0.1 μm.

[0074] In this application, the types of the first solvent and the third solvent are not limited, and solvents commonly used in the field of lithium batteries can be selected. For example, the first solvent and the third solvent can be water, preferably deionized water.

[0075] In this application, the selection of nickel, cobalt, and manganese sources is not limited, and commonly used metal compounds in the art can be selected. In some embodiments, the nickel source includes nickel hydroxide and / or nickel oxide; the cobalt source includes cobalt hydroxide and / or cobalt oxide; and the manganese source includes one or more of manganese carbonate, manganese trioxide, and manganese dioxide.

[0076] In some embodiments, after dispersing tin oxide and tungsten oxide in a third solvent, the method further includes milling the formed dispersion to adjust the particle size of the third slurry within the stated range.

[0077] In some embodiments, after dispersing the nickel source, cobalt source, manganese source and metal composite oxide in a first solvent, the method further includes a step of milling the formed dispersion to adjust the particle size of the first slurry within the stated range.

[0078] In this application, there are no restrictions on the drying method of the first slurry and the third slurry. Commonly used drying processes can be selected. For example, the drying method of the first slurry and the third slurry can be spray drying. The drying temperature of the first slurry can be 550℃~650℃, and the drying temperature of the third slurry can be 200℃~350℃.

[0079] S200: Preparation of cathode materials.

[0080] In this application, the type of lithium source is not limited; any lithium-containing compound commonly used in the field of lithium batteries may be selected. In some embodiments, the lithium source includes one or more of lithium hydroxide, lithium carbonate, and lithium acetate.

[0081] In some embodiments, the molar ratio of the first material to the lithium source is 1:(1.02 to 1.10).

[0082] In some embodiments, the calcination conditions in step S200 include: the calcination atmosphere is an oxygen-containing gas, the calcination temperature is 850℃~950℃, and the calcination time is 10h~16h.

[0083] It is understandable that after calcination, a crushing step may be included to control the particle size of the cathode material within a reasonable range. The specific crushing process could be airflow crushing.

[0084] In some embodiments, the particle size of the cathode material is 3.2 μm ≤ D 50 ≤4.2μm.

[0085] S300: Preparation of the second material.

[0086] In this application, the type of the second solvent is not limited, and any solvent commonly used in the field of lithium batteries can be selected. For example, the second solvent can be water, preferably deionized water.

[0087] In some embodiments, the particle size D of the second slurry 50 ≤0.1μm.

[0088] In some implementations, the D of the second material 50 ≤0.3μm.

[0089] In this application, there are no restrictions on the method of drying the second slurry. Any commonly used drying process can be selected. For example, the method of drying the second slurry can be spray drying, and the drying temperature of the second slurry can be 200℃~350℃.

[0090] It is understandable that after drying, a crushing step may be included to control the particle size of the second material within a reasonable range. The specific crushing process could be airflow crushing.

[0091] In some embodiments, the molar mass ratio of the positive electrode material to the second material is 100:(1-3).

[0092] S300: Preparation of positive electrode composite materials.

[0093] In some embodiments, the particle size of the cathode composite material is 3.4 μm ≤ D 50 ≤4.2μm.

[0094] In some embodiments, the conditions for calcining the mixture of the cathode material and the second material include: calcination atmosphere containing oxygen gas, calcination temperature of 850°C to 950°C, and calcination time of 6h to 12h.

[0095] In some embodiments, the molar mass ratio of the positive electrode material to the second material is 100:(1-3).

[0096] It is understandable that after calcination, a crushing step may be included to control the particle size of the cathode composite material within a reasonable range. The specific crushing process could be airflow crushing.

[0097] In this application, the oxygen-containing gas can specifically be oxygen or a mixture of oxygen and an inert gas, wherein the mass concentration of oxygen in the mixture of oxygen and an inert gas is >80%; the inert gas can specifically be helium and / or argon.

[0098] Thirdly, this application provides a battery comprising the positive electrode composite material described in the first aspect.

[0099] In this application, the battery can specifically be a lithium-ion battery. It is understood that the battery may also include other essential components, such as a positive current collector, a negative electrode, a separator, and an electrolyte. The materials for the positive current collector, negative electrode, separator, and electrolyte are not limited; any materials commonly used in the lithium battery field may be selected.

[0100] The present application will be further described in detail below with reference to specific embodiments.

[0101] Example 1

[0102] 1) Tin oxide (SnO2) and tungsten oxide (WO3) were dispersed in deionized water at a molar ratio of 1:3 to form dispersion 1. Dispersion 1 was then milled in a sand mill to obtain slurry 1 with a particle size D50 of 0.08 μm. Slurry 1 was then spray-dried at 250°C to obtain material 1.

[0103] 2) Nickel hydroxide, cobalt hydroxide, manganese carbonate, and material 1 were weighed and dispersed in deionized water according to a molar ratio of nickel, cobalt, and manganese to material 1 of 0.82:0.1:0.08:0.001 to form dispersion 2. Dispersion 2 was then milled in a sand mill to obtain slurry 2 with a particle size D50 of 0.08 μm. Slurry 2 was then spray-dried at 550℃ to obtain material 2.

[0104] 3) Material 2 and lithium hydroxide were weighed at a molar ratio of 1:1.04 and mixed in a high-speed mixer to obtain material 3. Material 3 was then calcined in a roller furnace and followed by air jet crushing to obtain material 4 (Li) with a particle size D50 of 3.4 μm. 1.04 Ni 0.82 Co 0.1 Mn 0.08 (1 / 3 SnO2·WO3) 0.001 O2). The roasting process is as follows: the roasting temperature is 880℃, the roasting atmosphere is oxygen, and the roasting time is 16h;

[0105] 4) Mix Co3O4 and Li at a molar ratio of 1:3. 1.4 Al 0.4 Ti 1.6 (PO4)3 was dispersed in deionized water to form dispersion 3. Dispersion 3 was then milled in a sand mill to obtain slurry 3 with a particle size D50 of 0.08 μm. Slurry 3 was then spray-dried at 250°C and crushed to obtain material 5 with a particle size D50 of 0.2 μm.

[0106] 5) Material 4 and material 5 were mixed in a high-speed mixer at a molar mass ratio of 100:3 to obtain material 6. Material 6 was then calcined in a roller furnace and followed by airflow crushing to obtain a cathode composite material (Li) with a particle size D50 of 3.6 μm. 1.04 Ni 0.82 Co 0.1 Mn 0.08 (1 / 3 SnO2·WO3) 0.001 O2)@(1 / 3Co3O4·Li 1.4 Al 0.4 Ti 1.6 (PO4)3). The calcination process is as follows: the calcination temperature is 900℃, the calcination atmosphere is oxygen, and the calcination time is 6h.

[0107] Example 2

[0108] 1) Tin oxide (SnO2) and tungsten oxide (WO3) were dispersed in deionized water at a molar ratio of 1:3 to form dispersion 1. Dispersion 1 was then milled in a sand mill to obtain slurry 1 with a particle size D50 of 0.09 μm. Slurry 1 was then spray-dried at 300°C to obtain material 1.

[0109] 2) Nickel hydroxide, cobalt hydroxide, manganese carbonate, and material 1 were weighed and dispersed in deionized water according to a molar ratio of nickel, cobalt, and manganese to material 1 of 0.7:0.1:0.2:0.002 to form dispersion 2. Dispersion 2 was then milled in a sand mill to obtain slurry 2 with a particle size D50 of 0.08 μm. Slurry 2 was then spray-dried at 600℃ to obtain material 2.

[0110] 3) Material 2 and lithium hydroxide were weighed at a molar ratio of 1:1.06 and mixed in a high-speed mixer to obtain material 3. Material 3 was then calcined in a roller furnace and followed by air jet crushing to obtain material 4 (Li) with a particle size D50 of 3.6 μm. 1.06 Ni 0.7 Co 0.1 Mn )0.2 (1 / 3 SnO2·WO3) 0.002 O2). The roasting process is as follows: the roasting temperature is 910℃, the roasting atmosphere is oxygen, and the roasting time is 12h;

[0111] 4) Mix Co3O4 and Li at a molar ratio of 1:3. 1.4 Al 0.4 Ti 1.6(PO4)3 was dispersed in deionized water to form dispersion 3. Dispersion 3 was then milled in a sand mill to obtain slurry 3 with a particle size D50 of 0.08 μm. Slurry 3 was then spray-dried at 250°C and crushed to obtain material 5 with a particle size D50 of 0.25 μm.

[0112] 5) Material 4 and material 5 were mixed in a high-speed mixer at a molar mass ratio of 100:1 to obtain material 6. Material 6 was then calcined in a roller furnace and followed by airflow crushing to obtain a cathode composite material (Li) with a particle size D50 of 3.6 μm. 1.06 Ni 0.7 Co 0.1 Mn )0.2 (1 / 3 SnO2·WO3) 0.002 O2)@(1 / 3Co3O4·Li 1.4 Al 0.4 Ti 1.6 (PO4)3). The calcination process is as follows: the calcination temperature is 900℃, the calcination atmosphere is oxygen, and the calcination time is 6h.

[0113] Example 3

[0114] 1) Tin oxide (SnO2) and tungsten oxide (WO3) were dispersed in deionized water at a molar ratio of 2:3 to form dispersion 1. Dispersion 1 was then milled in a sand mill to obtain slurry 1 with a particle size D50 of 0.09 μm. Slurry 1 was then spray-dried at 300°C to obtain material 1.

[0115] 2) Nickel hydroxide, cobalt hydroxide, manganese carbonate, and material 1 were weighed and dispersed in deionized water according to a molar ratio of nickel, cobalt, and manganese to material 1 of 0.7:0.05:0.25:0.003 to form dispersion 2. Dispersion 2 was then milled in a sand mill to obtain slurry 2 with a particle size D50 of 0.08 μm. Slurry 2 was then spray-dried at 600℃ to obtain material 2.

[0116] 3) Material 2 and lithium hydroxide were weighed at a molar ratio of 1:1.06 and mixed in a high-speed mixer to obtain material 3. Material 3 was then calcined in a roller furnace and followed by air jet crushing to obtain material 4 (Li) with a particle size D50 of 3.6 μm. 1.06 Ni 0.7 Co 0.05 Mn 0.25 (2 / 3 SnO2·WO3) 0.003 O2). The roasting process is as follows: the roasting temperature is 950℃, the roasting atmosphere is oxygen, and the roasting time is 12h;

[0117] 4) Mix Co3O4 and Li at a molar ratio of 1:2. 1.4 Al 0.4 Ti 1.6 (PO4)3 was dispersed in deionized water to form dispersion 3. Dispersion 3 was then milled in a sand mill to obtain slurry 3 with a particle size D50 of 0.08 μm. Slurry 3 was then spray-dried at 250°C and crushed to obtain material 5 with a particle size D50 of 0.25 μm.

[0118] 5) Material 4 and material 5 were mixed in a high-speed mixer at a molar mass ratio of 100:2 to obtain material 6. Material 6 was then calcined in a roller furnace and followed by airflow crushing to obtain a cathode composite material (Li) with a particle size D50 of 3.6 μm. 1.06 Ni 0.7 Co 0.05 Mn 0.25 (2 / 3 SnO2·WO3) 0.003 O2)@(1 / 2Co3O4·Li 1.4 Al 0.4 Ti 1.6 (PO4)3). The calcination process is as follows: the calcination temperature is 900℃, the calcination atmosphere is oxygen, and the calcination time is 6h.

[0119] Example 4

[0120] 1) Tin oxide (SnO2) and tungsten oxide (WO3) were dispersed in deionized water at a molar ratio of 1:2 to form dispersion 1. Dispersion 1 was then milled in a sand mill to obtain slurry 1 with a particle size D50 of 0.08 μm. Slurry 1 was then spray-dried at 300°C to obtain material 1.

[0121] 2) Nickel hydroxide, cobalt hydroxide, manganese carbonate, and material 1 were weighed and dispersed in deionized water according to a molar ratio of nickel, cobalt, and manganese to material 1 of 0.9:0.05:0.05:0.001 to form dispersion 2. Dispersion 2 was then milled in a sand mill to obtain slurry 2 with a particle size D50 of 0.08 μm. Slurry 2 was then spray-dried at 650℃ to obtain material 2.

[0122] 3) Material 2 and lithium hydroxide were weighed at a molar ratio of 1:1.08 and mixed in a high-speed mixer to obtain material 3. Material 3 was then calcined in a roller furnace and followed by air jet crushing to obtain material 4 (Li) with a particle size D50 of 3.4 μm. 1.08 Ni 0.9 Co 0.05 Mn 0.05 (1 / 2SnO2·WO3) 0.001O2). The roasting process is as follows: the roasting temperature is 860℃, the roasting atmosphere is oxygen, and the roasting time is 16h;

[0123] 4) Mix Co3O4 and Li at a molar ratio of 2:3. 1.4 Al 0.4 Ti 1.6 (PO4)3 was dispersed in deionized water to form dispersion 3. Dispersion 3 was then milled in a sand mill to obtain slurry 3 with a particle size D50 of 0.08 μm. Slurry 3 was then spray-dried at 250°C and crushed to obtain material 5 with a particle size D50 of 0.2 μm.

[0124] 5) Material 4 and material 5 were mixed in a high-speed mixer at a molar mass ratio of 100:0.3 to obtain material 6. Material 6 was then calcined in a roller furnace and followed by airflow crushing to obtain a cathode composite material (Li) with a particle size D50 of 3.6 μm. 1.08 Ni 0.9 Co 0.05 Mn 0.05 (1 / 2SnO2·WO3) 0.001 O2)@(2 / 3Co3O4·Li 1.4 Al 0.4 Ti 1.6 (PO4)3). The calcination process is as follows: the calcination temperature is 900℃, the calcination atmosphere is oxygen, and the calcination time is 6h.

[0125] Comparative Example 1

[0126] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the composite oxide is not doped with tin oxide and tungsten oxide. The specific steps are as follows:

[0127] 1) Nickel hydroxide, cobalt hydroxide, and manganese carbonate 1 were weighed and dispersed in deionized water according to a molar ratio of nickel, cobalt, and manganese of 0.82:0.1:0.079 to form dispersion 2. Dispersion 2 was then milled in a sand mill to obtain slurry 2 with a particle size D50 of 0.08 μm. Slurry 2 was then spray-dried at 550℃ to obtain material 2.

[0128] 2) Material 2 and lithium hydroxide were weighed at a molar ratio of 1:1.04 and mixed in a high-speed mixer to obtain material 3. Material 3 was then calcined in a roller furnace and followed by air jet crushing to obtain material 4 (Li) with a particle size D50 of 3.4 μm. 1.04 Ni 0.82 Co 0.1 Mn 0.08O2). The roasting process is as follows: the roasting temperature is 880℃, the roasting atmosphere is oxygen, and the roasting time is 16h;

[0129] 3) Mix Co3O4 and Li at a molar ratio of 1:3. 1.4 Al 0.4 Ti 1.6 (PO4)3 was dispersed in deionized water to form dispersion 3. Dispersion 3 was then milled in a sand mill to obtain slurry 3 with a particle size D50 of 0.08 μm. Slurry 3 was then spray-dried at 250°C and crushed to obtain material 5 with a particle size D50 of 0.2 μm.

[0130] 4) Material 4 and material 5 were mixed in a high-speed mixer at a molar mass ratio of 100:3 to obtain material 6. Material 6 was then calcined in a roller furnace and followed by airflow crushing to obtain a cathode composite material (Li) with a particle size D50 of 3.6 μm. 1.04 Ni 0.82 Co 0.1 Mn 0.08 O2@(1 / 3Co3O4·Li 1.4 Al 0.4 Ti 1.6 (PO4)3). The calcination process is as follows: the calcination temperature is 900℃, the calcination atmosphere is oxygen, and the calcination time is 6h.

[0131] Comparative Example 2

[0132] The preparation method of this comparative example is basically the same as that of Example 1, except that tungsten oxide is used instead of the composite oxide of tin oxide and tungsten oxide. Step 1) of this comparative example is as follows:

[0133] Tungsten oxide (WO3) was dispersed in deionized water to form dispersion 1. Dispersion 1 was then milled in a sand mill to obtain slurry 1 with a particle size D50 of 0.08 μm. Slurry 1 was then spray-dried at 250°C to obtain material 1.

[0134] Comparative Example 3

[0135] The preparation method of this comparative example is basically the same as that of Example 1, except that tin oxide is used instead of the composite oxide of tin oxide and tungsten oxide. Step 1) of this comparative example is as follows:

[0136] Tin oxide (SnO2) was dispersed in deionized water to form dispersion 1. Dispersion 1 was then milled in a sand mill to obtain slurry 1 with a particle size D50 of 0.08 μm. Slurry 1 was then spray-dried at 250°C to obtain material 1.

[0137] Comparative Example 4

[0138] The preparation method of this comparative example is basically the same as that of Example 1, except that the coating material is only Li. 1.4 Al 0.4 Ti 1.6 (PO4)3. Step 4) of this comparative example is as follows:

[0139] Li 1.4 Al 0.4 Ti 1.6 (PO4)3 was dispersed in deionized water to form dispersion 3. Dispersion 3 was then placed in a sand mill for sand milling to obtain slurry 3 with a particle size D50 of 0.08 μm. Slurry 3 was then spray-dried at 250°C and crushed to obtain material 5 with a particle size D50 of 0.2 μm.

[0140] Comparative Example 5

[0141] The preparation method of this comparative example is basically the same as that of Example 1, except that the coating material is only Co3O4. Step 4) of this comparative example is as follows:

[0142] Co3O4 was dispersed in deionized water to form dispersion 3. Dispersion 3 was then milled in a sand mill to obtain slurry 3 with a particle size D50 of 0.08 μm. Slurry 3 was then spray-dried at 250 °C and crushed to obtain material 5 with a particle size D50 of 0.2 μm.

[0143] SEM images of the cathode composite materials prepared in Example 1 and Comparative Examples 1-3 are shown below. Figures 2-5 As shown. By Figures 2-5 As can be seen, the cathode composite material provided in this application has the characteristic of directional growth, and a highly active single-crystal cathode material with directional growth has been obtained, which can reduce the DCR of the battery and improve the cycle performance of the battery. However, the cathode composite material in the comparative example does not exhibit the characteristic of directional growth, so it is difficult to reduce the DCR and will also affect the cycle performance of the battery.

[0144] The positive electrode composite materials prepared in Examples 1-4 and Comparative Examples 1-5 were subjected to relevant performance tests, and the test results are shown in Table 1 below.

[0145] The testing steps are as follows:

[0146] The cathode composite materials obtained in Examples 1-4 and Comparative Examples 1-5 were used to prepare high-performance coin cells, and the initial cycle discharge specific capacity, initial DCR, and cycle retention after 50 cycles of the coin cells were tested. The test conditions for the initial cycle discharge specific capacity were: using a Blue Electric charge-discharge apparatus, LR 2032, 0.2C, 2.5V~4.55V, vs. Li + / Li, the cyclic test conditions are 45℃, 3.0~4.3V, 0.5C / 0.5C.

[0147] Table 1

[0148]

[0149]

[0150] As shown in Table 1 above, the directionally grown high-activity interfacial single-crystal ternary cathode composite material provided in this application exhibits high specific capacity and low initial DCR, demonstrating strong application performance. Comparative Example 1 is undoped with a metal composite oxide, Comparative Example 2 is doped with only tungsten oxide, and Comparative Example 3 is doped with only tin oxide. Table 1 shows that the coin cells prepared in Comparative Examples 1-3 exhibit significantly increased DCR and significantly worsened cycle performance; the coating material in Comparative Example 4 contains only Li... 1.4 Al 0.4 Ti 1.6 (PO4)3 has a significantly different structure from the matrix layered ternary material, resulting in a markedly worse cycle performance; the coating material in Comparative Example 5 contains only Co3O4, and its lithium-ion reactivity is lower than that of Li. 1.4 Al 0.4 Ti 1.6 (PO4)3, therefore the initial DCR increased significantly; at the same time, because the added Co3O4 and the residual alkali at the interface will generate LiCoO2, without Li 1.4 Al 0. 4Ti 1.6 (PO4)3 achieves co-coating, resulting in poor cycling performance.

[0151] The surface energy changes of the (003) crystal planes of the cathode composite materials prepared in Examples 1-4 and Comparative Examples 1-3 were calculated using VASP software with a 4×4×1 expanded cell. The calculation results are shown in Table 2.

[0152] Table 2

[0153]

[0154] As shown in Table 2, compared with Comparative Example 1 (which was not doped), the surface energy of the (003) crystal plane in Example 1 is significantly reduced, while the surface energies of Comparative Examples 2 and 3 are basically the same as those of Comparative Example 1. The low surface energy of the 003 plane is beneficial for crystal growth along the 003 direction, which can further ensure the directional growth of the single-crystal cathode composite material. Figure 2 It can also be seen that the morphology of the positive electrode composite material prepared in Example 1 is significantly more slender.

[0155] The residual alkali content of the positive electrode composite materials prepared in Examples 1-4 and Comparative Examples 1-5 is shown in Table 3. The test procedure for residual alkali content is as follows: 5g of powder material was added to pure water and magnetically stirred for five minutes, then filtered, and the filtrate was subjected to potentiometric titration.

[0156] Table 3

[0157]

[0158] As shown in Table 3, the residual alkali content of the cathode composite material provided in this application is generally low. However, the residual alkali content of Comparative Example 4 is significantly higher, mainly because Co3O4 was not added, while Li3O4 was added. 1.4 Al 0.4 Ti 1.6 (PO4)3 cannot consume the residual alkali content on the surface.

[0159] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0160] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the scope of the claims.

Claims

1. A positive electrode composite material, characterized in that, The surface energy of the positive electrode composite (003) crystal plane is ≤1.023 J / m 2 ; the positive electrode composite comprises: A cathode material, comprising a ternary cathode material and a metal composite oxide doped in the ternary cathode material, wherein the metal composite oxide comprises tin oxide and tungsten oxide; a coating layer coated on a surface of the positive electrode material, a material of the coating layer including Co3O4 and Li 1+ m Al m Ti 2-m (PO4)3, where 0.1≤m≤1.

2. The positive electrode composite material as described in claim 1, characterized in that, The cathode composite material is a single-crystal cathode composite material.

3. The positive electrode composite material as described in claim 1, characterized in that, The molecular formula of the positive electrode material is Li z Ni a Co b Mn (1-a-b) (dSnO2·WO3) c O2, wherein 1.02≤z≤1.1, 0.6≤a≤0.95, 0.05≤b≤0.4, 0.001≤c≤0.003, 1 / 3≤d≤2 / 3.

4. The positive electrode composite material as described in claim 1, characterized in that, It meets at least one of the following characteristics: 1) The molar mass ratio of the metal composite oxide to the ternary cathode material is (0.1~0.3):100; 2) In the metal composite oxide, the molar ratio of tin oxide to tungsten oxide is (1~2):3; 3) in the coating layer, the molar ratio of Co3O4 and Li 1+m Al m Ti 2-m (PO4)3 is (1-2):3; 4) The thickness of the coating layer is 5nm~100nm; 5) during the process of forming the coating layer, the Co3O4 and the Li 1+m Al m Ti 2-m (PO4)3react to form LiCoO2, the Li 1+m Al m Ti 2-m Al, Ti and PO4 in the (PO4)3 3- enter the LiCoO2lattice.

5. The positive electrode composite material as described in claim 1, characterized in that, The molecular formula of the ternary cathode material is Li z Ni a Co b Mn (1-a-b) O2, the molecular formula of the metal composite oxide is dSnO2·WO3, and the molecular formula of the cathode material is Li z Ni a Co b Mn (1-a-b) (dSnO2·WO3) c O2; wherein, 1.02≤z≤1.1, 0.6≤a≤0.95, 0.05≤b≤0.4, 0.001≤c≤0.003, 1 / 3≤d≤2 / 3.

6. A method for preparing a positive electrode composite material as described in any one of claims 1 to 5, characterized in that, Includes the following steps: A nickel source, a cobalt source, a manganese source, and the aforementioned metal composite oxide are dispersed in a first solvent to form a first slurry, and the first slurry is dried to form a first material; The first material is mixed with a lithium source and calcined to prepare the cathode material; Co3O4 and Li 1+m Al m Ti 2-m (PO4)3 is dispersed in a second solvent to form a second slurry, and the second slurry is dried to form a second material; The positive electrode material is mixed with the second material and calcined to form the coating layer on the surface of the positive electrode material.

7. The preparation method according to claim 6, characterized in that, It meets at least one of the following characteristics: 1) The metal composite oxide is prepared by the following method: Tin oxide and tungsten oxide are dispersed in a third solvent to form a third slurry, and the third slurry is dried to obtain the metal composite oxide; 2) The conditions for calcining the first material and the lithium source mixture include: the calcination atmosphere is an oxygen-containing gas, the calcination temperature is 850℃~950℃, and the calcination time is 10h~16h; 3) The conditions for calcining the positive electrode material and the second material mixture include: the calcination atmosphere is an oxygen-containing gas, the calcination temperature is 850℃~950℃, and the calcination time is 6h~12h; 4) The drying temperature for the first slurry is 550℃~650℃; 5) The drying temperatures for the second slurry and the third slurry are independently 200℃~350℃.

8. The preparation method according to claim 7, characterized in that, It meets at least one of the following characteristics: 1) the particle size Dv50 of the first slurry, the second slurry and the third slurry is independently from each other less than or equal to 0.1 pm; and 50 less than or equal to 0.1 pm; and 2) The particle size of the positive electrode material is 3.2μm ≤ D 50 ≤4.2μm; 3) D of the second material 50 ≤0.3μm; 4) The particle size of the positive electrode composite material is 3.4 μm ≤ D 50 ≤4.2μm.

9. The preparation method according to any one of claims 6 to 8, characterized in that, It meets at least one of the following characteristics: 1) The nickel source includes nickel hydroxide and / or nickel oxide; 2) The cobalt source includes cobalt hydroxide and / or cobalt oxide; 3) The manganese source includes one or more of manganese carbonate, manganese trioxide, and manganese dioxide; 4) The lithium source includes one or more of lithium hydroxide, lithium carbonate, and lithium acetate; 5) The molar ratio of the first material to the lithium source is 1:(1.02~1.10). 6) The molar mass ratio of the positive electrode material to the second material is 100:(1~3).

10. A battery, characterized in that, Including the positive electrode composite material as described in any one of claims 1 to 5.

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