Ternary positive electrode composite material and preparation method thereof, positive electrode plate, battery and electric equipment

Abstract

The invention provides a ternary positive electrode composite material and a preparation method thereof, a positive electrode plate, a battery and electric equipment. The ternary positive electrode composite material comprises a ternary material core and a coating layer coating the surface of the core, the coating layer comprises a fast ion conductor, the composition of the fast ion conductor is Li < 1 + x > Ti < 2-x > Al < x > (PO4) < 3 >, and x is more than 0 and less than or equal to 0.5; the coating rate of the coating layer is greater than or equal to 90%; the content of free lithium ions on the surface of the ternary positive electrode composite material is less than or equal to 600ppm. The ternary positive electrode composite material disclosed by the invention has good rate capability and cycling stability.

Description

Technical Field

[0001] The present invention relates to a ternary positive electrode composite material, in particular to a ternary positive electrode composite material and a preparation method thereof, a positive electrode sheet, a battery, and an electrical device, belonging to the technical field of batteries. Background Art

[0002] Ternary cathode materials, with their high operating potential and theoretical capacity (≈280 mAh / g), are widely used in various energy storage systems, particularly in electric vehicles. However, during cycling, their surface state is unstable, prone to side reactions with the electrolyte, resulting in grain boundary failure and rapid capacity decay. Particularly at high operating potentials, electrolyte decomposition and metal ion dissolution can cause surface structure collapse, leading to irreversible phase transformations. Furthermore, oxidation of the nickel element causes oxygen release and gassing within the lattice, raising safety concerns.

[0003] Therefore, improving the surface stability of ternary cathode materials is an effective way to improve their cycling stability and high-temperature performance. Surface modification of ternary cathode materials is currently the most commonly used method, primarily involving solid-phase and liquid-phase methods. The solid-phase method involves uniformly mixing the cathode material and coating material using methods such as ball milling and grinding before curing at high temperatures. The liquid-phase method involves first adding the cathode material to a dispersing solvent, then adding soluble or insoluble materials, uniformly mixing, and drying and calcining.

[0004] However, the rate performance and cycle stability of the ternary positive electrode materials prepared by existing technologies need to be further improved. Summary of the Invention

[0005] The present invention provides a ternary positive electrode composite material having excellent rate performance and cycle stability.

[0006] The present invention also provides a method for preparing a ternary positive electrode composite material. The preparation method is simple to operate, and the prepared ternary positive electrode composite material has excellent rate performance and cycle stability.

[0007] The present invention also provides a positive electrode plate, which includes the above-mentioned ternary positive electrode composite material or the ternary positive electrode composite material prepared by the above-mentioned preparation method.

[0008] The present invention also provides a battery, which includes the above-mentioned positive electrode plate and has excellent rate performance and cycle stability.

[0009] The present invention also provides an electrical device, which includes the battery and has excellent performance.

[0010] The present invention provides a ternary positive electrode composite material, comprising a ternary material core and a coating layer coated on the surface of the core, wherein the coating layer comprises a fast ion conductor, and the composition of the fast ion conductor is Li 1+x Ti 2-x Al x (PO4)3,0<x≤0.5;

[0011] The coating rate of the coating layer is ≥90%;

[0012] The free lithium ion content on the surface of the ternary positive electrode composite material is ≤600ppm.

[0013] In the ternary cathode composite material as described above, the molar ratio of the fast ion conductor to the ternary material core is 0.1% to 0.5%.

[0014] The ternary positive electrode composite material as described above, wherein the thickness of the coating layer is ≤10 nm.

[0015] The ternary positive electrode composite material as described above, wherein the Al element content in the ternary positive electrode composite material is ≤600 ppm, preferably 110-210 ppm;

[0016] And / or, the Ti element content in the ternary positive electrode composite material is ≤4500 ppm, preferably 1300-1900 ppm;

[0017] And / or, the P element content in the ternary positive electrode composite material is ≤4500 ppm, preferably 1500~2100 ppm.

[0018] As described above, the ternary cathode composite material, wherein the fast ion conductor includes Ti 4+ .

[0019] The ternary cathode composite material as described above, wherein the composition of the core of the ternary material is Li a Ni 1-b- c Co b Mn c O2, 1<a≤1.1, 0.3<1-bc≤0.8, 0 <b≤0.4,0<c≤0.4。

[0020] The ternary cathode composite material as described above, wherein the core of the ternary material is a secondary particle formed by agglomeration of primary particles;

[0021] The size of the primary particles is 100-500 nm, and the size of the secondary particles is 1.6-6.5 μm.

[0022] A second aspect of the present invention provides a method for preparing the ternary cathode composite material as described above, the preparation method comprising the following steps:

[0023] 1) subjecting a raw material system comprising nickel, cobalt, and manganese hydroxides and lithium hydroxide to a first hydrothermal reaction to obtain a ternary cathode material intermediate suspension;

[0024] 2) adding a phosphorus source, a titanium source, and an aluminum source to the suspension of the ternary cathode material intermediate to obtain a ternary cathode composite material intermediate through a second hydrothermal reaction;

[0025] 3) calcining the ternary cathode composite material intermediate to obtain the ternary cathode composite material.

[0026] The preparation method as described above, wherein in step 1), the temperature of the first hydrothermal reaction is 200-280° C. and the time is 3-6 hours;

[0027] And / or, in step 2), the temperature of the second hydrothermal reaction is 170°C to 200°C, and the time is 12 to 24 hours;

[0028] And / or, in step 3), the calcination treatment includes a first calcination treatment and a second calcination treatment performed sequentially, the first calcination treatment is performed at a temperature of 400-600° C. and for a time of 4-8 hours; the second calcination treatment is performed at a temperature of 800-950° C. and for a time of 8-12 hours.

[0029] The third aspect of the present invention provides a positive electrode plate, comprising a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the ternary positive electrode composite material provided by the first aspect of the present invention or the ternary positive electrode composite material prepared by the preparation method of the second aspect of the present invention.

[0030] A fourth aspect of the present invention provides a battery, comprising the positive electrode sheet provided by the third aspect of the present invention.

[0031] A fifth aspect of the present invention provides an electrical device comprising the battery described in the fourth aspect of the present invention.

[0032] The implementation of the present invention has at least the following advantages:

[0033] 1) The ternary positive electrode composite material provided by the present invention includes a ternary material core and a coating layer coated on the surface of the core, wherein the coating layer includes a lithium titanium aluminum phosphate fast ion conductor of a specific composition, and the coverage of the coating layer is ≥90%, and the free lithium ion content on the surface of the ternary composite material is ≤600ppm. The fast ion conductor has good ion conductivity and can significantly improve the rate performance of the battery, while the high coverage improves the structural stability of the ternary material, so that the battery has good cycle performance. In addition, the lower free lithium ion content means that the content of lithium ions in the form of oxides, hydroxides and carbonates on the surface of the ternary composite material is low, which can further avoid side reactions between the ternary positive electrode composite material and the electrolyte, improve its interface stability, and thus improve the cycle performance.

[0034] 2) The preparation method of the ternary positive electrode composite material provided by the present invention adopts a hydrothermal method to first synthesize and prepare a ternary positive electrode material intermediate, then directly coat the intermediate with a fast ion conductor, and finally perform a calcination treatment to convert the ternary positive electrode material intermediate in the core into a ternary positive electrode material. Compared with directly adding the ternary positive electrode material to an aqueous solution containing a coating source for coating, the intermediate is not sensitive to water, has fewer side reactions, can avoid the formation of lithium hydroxide, lithium carbonate, and lithium oxide, and reduce the free lithium content on the surface of the coated material, so that the material has a low free lithium content while obtaining a high coating rate through liquid phase coating. In addition, in the above-mentioned coating process, the coating source can in situ nucleate and grow on the surface of the ternary positive electrode material intermediate to obtain a coating layer. The coating layer has good uniformity and is not easy to fall off, which can effectively improve the cycle stability of the ternary positive electrode composite material. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the X-ray photoelectron spectrum of the ternary cathode composite material of Example 1;

[0036] Figure 2 This is the X-ray photoelectron spectrum of the button battery made of the ternary positive electrode composite material of Example 1 after charging. DETAILED DESCRIPTION

[0037] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0038] On the one hand, the present invention provides a ternary cathode composite material, comprising a ternary material core and a coating layer coated on the surface of the core, wherein the coating layer comprises a fast ion conductor, and the fast ion conductor is composed of Li 1+x Ti 2-x Al x (PO4)3, 0<x≤0.5; the coverage rate of the coating layer is ≥90%; the free lithium ion content on the surface of the ternary positive electrode composite material is ≤600ppm.

[0039] The ternary cathode composite material provided by the present invention is a material with a core-shell structure, wherein the coating layer of the shell comprises a fast ion conductor and the core is a ternary material.

[0040] Among them, the composition of the fast ion conductor is Li 1+x Ti 2-x Al x (PO4)3, 0<x≤0.5. Specifically, x includes but is not limited to 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5 or any other value greater than 0 and less than or equal to 0.5.

[0041] The coverage rate of the coating layer in the present invention refers to the ratio of the coverage area of the coating layer on the surface of the inner core to the total surface area of the inner core.

[0042] Free lithium ions refer to lithium hydroxide or other lithium-containing compounds attached to the surface of the ternary cathode composite material. Specifically, the free lithium ion content is ≤ 600 ppm, such as 600 ppm, 500 ppm, 400 ppm, 300 ppm, 200 ppm, 100 ppm, or any other value not exceeding 600 ppm.

[0043] When the ternary positive electrode composite material provided by the present invention is used in a battery, it can significantly improve the rate performance and cycle stability of the battery. The inventor analyzed this and believed that the reason may be that: on the one hand, by constructing a core-shell structure including a coating layer of a fast ion conductor and a core of a ternary material, the migration impedance of the ions is reduced, excellent ionic conductivity is provided, and the rate performance is improved. On the other hand, the coating layer with a high coverage rate reduces the direct contact between the core of the ternary material and the electrolyte, reduces the side reaction between the electrolyte and the core of the ternary material, and improves the cycle stability. In addition, the lower free lithium ion content means that the content of lithium ions in the form of oxides, hydroxides and carbonates on the surface of the ternary composite material is low, which can further avoid the side reaction between the ternary positive electrode composite material and the electrolyte, improve its interface stability, and thus improve the cycle performance.

[0044] Furthermore, in one embodiment of the present invention, the molar ratio of the fast ion conductor to the ternary material core is 0.1% to 0.5%. For example, the molar ratio of the fast ion conductor to the ternary material core can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any other value between 0.1% and 0.5%.

[0045] When the molar ratio of the fast ion conductor to the ternary material is within the above range, it can not only enhance the ionic conductivity of the material and reduce the charge transfer resistance of the electrode material, but also further reduce the contact between the core of the ternary material and the electrolyte, reduce the frequency of side reactions, and improve the rate performance and cycle stability.

[0046] Furthermore, in a specific embodiment of the present invention, the thickness of the coating layer is ≤10 nm.

[0047] The coating layer thickness in the present invention refers to the average thickness of the coating layer.

[0048] The thickness of the coating layer can be detected by common methods in the art, such as scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, etc.

[0049] In detail, the thickness of the coating layer includes but is not limited to 10 nm, 8 nm, 6 nm, 4 nm, 2 nm, 1 nm, or any value not higher than 10 nm.

[0050] When the coating layer thickness is within the above range, it can not only reduce the obstacles to charge transfer and maintain a high ionic conductivity, but also avoid the additional impedance caused by the coating layer being too thick, further improving the battery's rate performance and cycle stability.

[0051] Furthermore, in one embodiment of the present invention, the Al content in the ternary positive electrode composite material is ≤600 ppm, preferably 110-210 ppm;

[0052] And / or, the Ti element content in the ternary positive electrode composite material is ≤4500ppm, preferably 1300~1900ppm;

[0053] And / or, the P element content in the ternary positive electrode composite material is ≤4500 ppm, preferably 1500~2100 ppm.

[0054] It can be understood that the Al element content, Ti element content and P element content in the ternary positive electrode composite material can be controlled by controlling the type and addition amount of the aluminum source, titanium source and phosphorus source during the preparation process.

[0055] An element analyzer can be used to test the content of various elements in the ternary positive electrode composite material.

[0056] The Al element content includes but is not limited to 600 ppm, 550 ppm, 500 ppm, 450 ppm, 400 ppm, 350 ppm, 300 ppm, 250 ppm, 200 ppm, 150 ppm, 100 ppm or any other value not higher than 600 ppm.

[0057] The content of Ti element includes but is not limited to 4500 ppm, 4000 ppm, 3500 ppm, 3000 ppm, 2500 ppm, 2000 ppm, 1500 ppm, 1000 ppm or any other value not exceeding 4500 ppm.

[0058] When the Al element content, the Ti element content and the P element content are within the above ranges, the overall performance of the ternary positive electrode composite material can be improved, the stability of the ternary positive electrode composite material can be improved, and the stability of the ternary positive electrode composite material can be improved, especially the stability of the ternary positive electrode composite material in a high temperature environment.

[0059] As a preferred embodiment, the fast ion conductor includes Ti 4+ , that is, the Ti element in the fast ion conductor is at least partially Ti 4+ Exists in the form of ions.

[0060] When the ternary cathode composite material is used as a cathode material in a battery, the Ti in the fast ion conductor 4+ Can participate in the redox reaction, making Ti 4+ Transformed into Ti 3+ It can improve the charge storage capacity, increase the battery capacity, and further improve the ionic conductivity and battery charge and discharge rate, thereby improving battery performance.

[0061] Furthermore, in one embodiment of the present invention, the composition of the core of the ternary material is Li a Ni 1-b- c Co b Mn c O2, 1<a≤1.1, 0.3<1-bc≤0.8, 0 <b≤0.4,0<c≤0.4。

[0062] Nickel in ternary materials increases the material's energy density, cobalt helps improve the material's structural stability, thereby extending the battery's cycle life, and manganese helps improve the material's thermal stability, enhancing battery safety. However, nickel and cobalt are relatively expensive. Ternary materials with the above composition offer an optimal balance between energy density, cycle life, safety, and cost.

[0063] In a specific embodiment of the present invention, the core of the ternary material is a secondary particle formed by agglomeration of primary particles; the size of the primary particles is 100-500 nm, and the size of the secondary particles is 1.6-6.5 μm.

[0064] The size of primary particles refers to the average equivalent particle size of primary particles, while the size of secondary particles refers to the equivalent average particle size of secondary particles, which can also be considered as the average equivalent particle size of the core. The equivalent particle size refers to the equivalent particle size of spherical particles of the same material when the material particles are the same or similar to those of the same material particles.

[0065] In detail, the size of the primary particles includes but is not limited to 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm or a range between any two of them; the size of the secondary particles includes but is not limited to 1.6μm, 2.0μm, 2.5μm, 3.0μm, 3.5μm, 4.0μm, 4.5μm, 5.0μm, 5.5μm, 6.0μm, 6.5μm or a range between any two of them.

[0066] When the primary particle size is within the above range, the secondary particle formation density can be increased, resulting in a more uniform distribution of the secondary particles, which helps improve the overall performance of the electrode material, including increasing the cycle life and stability of the battery. Furthermore, when the secondary particle size is within the above range, it helps form a good conductive network, reducing internal resistance, thereby improving the battery's charge and discharge efficiency. It also provides superior mechanical strength and structural stability, reducing material structural damage during the charge and discharge process, and further improving the battery's cycle stability.

[0067] Another aspect of the present invention provides a method for preparing the ternary cathode composite material as described above, the preparation method comprising the following steps:

[0068] 1) subjecting a raw material system comprising nickel, cobalt, and manganese hydroxides and lithium hydroxide to a first hydrothermal reaction to obtain a ternary cathode material intermediate suspension;

[0069] 2) adding a phosphorus source, a titanium source, and an aluminum source to the suspension of the ternary cathode material intermediate, and obtaining a ternary cathode composite material intermediate through a second hydrothermal reaction;

[0070] 3) calcining the ternary cathode composite material intermediate to obtain the ternary cathode composite material.

[0071] In some embodiments, in step 1), nickel cobalt manganese hydroxide and lithium hydroxide are added to a solvent and stirred evenly to obtain a raw material system. The raw material system is heated to a set temperature using a heating device and stirred for a set time, and naturally cooled to room temperature to obtain a ternary positive electrode material intermediate suspension.

[0072] The present invention is not limited to a specific type of solvent, and any common type in the art may be selected. For example, the solvent includes, but is not limited to, at least one of deionized water, ethylene glycol, 1,2-propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and polyethylene glycol. In one embodiment, the solvent comprises deionized water at a volume fraction of not less than 50%.

[0073] Typically, the molar ratio of nickel-cobalt-manganese hydroxide to lithium hydroxide is close to 1:1. However, in actual production, to ensure sufficient lithiation reaction, a slight excess of lithium hydroxide is often used to compensate for potential lithium loss during the high-temperature reaction. This excess lithium hydroxide also ensures that lithium is fully embedded in the nickel-cobalt-manganese metal oxide lattice, forming a stable layered structure. Specifically, the molar ratio of nickel-cobalt-manganese hydroxide to lithium hydroxide is 1:1 to 1:1.4.

[0074] It is understood that in order to improve the uniformity of the various components in the raw material system, a suitable stirring speed can be selected. In one embodiment, the speed is 250 r / min to 400 r / min.

[0075] The present invention does not limit the specific device for stirring treatment, and a suitable device can be selected according to actual conditions. In one specific embodiment, a high-pressure reactor is used, and a magnetic stirring rotor is used for stirring treatment, wherein the magnetic stirring rotor types include aluminum nickel cobalt, samarium cobalt, ferrite, etc. as magnetic materials.

[0076] The filling ratio of the autoclave is 30% to 60%. The filling ratio of the autoclave refers to the ratio of the volume of liquid added to the reactor to the reactor's total volume. Within this range, the raw materials are well mixed and heat transferred, thereby improving reaction efficiency. A filling ratio below this range will result in inadequate mixing of the reactants, while a filling ratio above this range will affect stirring.

[0077] Step 2) adding a phosphorus source, a titanium source, and an aluminum source to the suspension of the ternary cathode material intermediate, heating the suspension to a set temperature using a heating device and stirring the suspension for a set time, naturally cooling the suspension to room temperature, and then filtering and drying the suspension for a set time to obtain a ternary cathode composite material intermediate.

[0078] In one specific embodiment, the phosphorus source is NH4H2PO4, the titanium source is (CH3CH3CHO)4Ti, and the aluminum source is Al(NO3)3·9H2O.

[0079] Furthermore, the molar ratio of NH4H2PO4, (CH3CH3CHO)4Ti, and Al(NO3)3·9H2O is 3:2-x:x (0 <x<0.5)。

[0080] Furthermore, the molar ratio of the addition amount of NH4H2PO4 to the above-mentioned nickel-cobalt-manganese hydroxide is 0.3:100~15:100; the molar ratio of the addition amount of (CH3CH3CHO)4Ti to the above-mentioned nickel-cobalt-manganese hydroxide is 0.15:100~10:100; and the molar ratio of the addition amount of Al(NO3)3·9H2O to the above-mentioned nickel-cobalt-manganese hydroxide is (0~2.5):100.

[0081] The present invention does not limit the specific type of heating equipment, and a suitable heating equipment can be selected according to actual conditions, such as an oven, microwave heating, etc.

[0082] In step 3), the ternary cathode composite material intermediate is calcined to obtain the ternary cathode composite material.

[0083] Calcination transforms the ternary cathode composite intermediate into the final ternary cathode composite. This calcination process completes the chemical reactions within the material, resulting in a ternary cathode material with excellent electrochemical performance. Calcination also removes organic matter and moisture from the intermediate and improves the material's crystallinity and stability.

[0084] The preparation method provided by the present invention adopts a hydrothermal method to first synthesize and prepare a ternary positive electrode material intermediate, then directly coats a fast ion conductor on the intermediate, and finally performs a calcination treatment to convert the ternary positive electrode material intermediate in the core into a ternary positive electrode material. Compared with directly adding the ternary positive electrode material to an aqueous solution containing a coating source for coating, the intermediate is not sensitive to water, has fewer side reactions, can avoid the formation of lithium hydroxide, lithium carbonate, and lithium oxide, and reduce the free lithium content on the surface of the coated material, so that the material has a low free lithium content while obtaining a high coating rate through liquid phase coating. In addition, in the above-mentioned coating process, the coating source can in situ nucleate and grow on the surface of the ternary positive electrode material intermediate to obtain a coating layer. The coating layer has good uniformity and is not easy to fall off, which can effectively improve the cycle stability of the ternary positive electrode composite material.

[0085] In one embodiment of the present invention, in step 1), the temperature of the first hydrothermal reaction is 200-280° C., and the time is 3-6 hours.

[0086] The temperature of the first hydrothermal reaction includes, but is not limited to, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C, or any range therebetween; and the time includes, but is not limited to, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h, or any range therebetween. When the first hydrothermal reaction is carried out within the above temperature and time ranges, production efficiency can be improved, and a more uniform suspension of the ternary cathode material intermediate can be formed, laying the foundation for subsequent preparation processes.

[0087] In a specific embodiment of the present invention, in step 2), the temperature of the second hydrothermal reaction is 170°C to 200°C, and the time is 12 to 24 hours. The temperature of the second hydrothermal reaction includes but is not limited to 170°C, 175°C, 180°C, 185°C, 190°C, 195°C, 200°C, or a range between any two thereof; the time includes but is not limited to 12h, 14h, 16h, 18h, 20h, 22h, 24h, or a range between any two thereof. The above temperature and time conditions are conducive to promoting sufficient reaction between the various components, generating a more uniform material, improving the consistency of the product, and can also effectively control the occurrence of side reactions, promote crystal growth and structural optimization of the material, and enhance the stability and conductivity of the material.

[0088] In a specific embodiment of the present invention, in step 3), the calcination treatment includes a first calcination treatment and a second calcination treatment performed sequentially, the first calcination treatment is performed at a temperature of 400-600°C for 4-8 hours; the second calcination treatment is performed at a temperature of 800-950°C for 8-12 hours. Specifically, the temperature of the first calcination treatment includes but is not limited to 400°C, 420°C, 460°C, 480°C, 500°C, 520°C, 540°C, 560°C, 580°C, 600°C or a range between any two thereof, and the time includes but is not limited to 4h, 4.5h, 5h, 5.5h, 6h, 6.5h, 7h, 7.5h, 8h or a range between any two thereof; the temperature of the second calcination treatment includes but is not limited to 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 920°C, 940°C, 950°C or a range between any two thereof, and the time includes but is not limited to 8h, 9h, 10h, 11h, 12h or a range between any two thereof. Among them, the first calcination treatment can effectively remove organic matter and solvent in the intermediate at a lower temperature, reduce impurities, and prevent adverse reactions at high temperatures. This facilitates the initial conversion of intermediates to form basic metal oxides or other inorganic compounds, laying the foundation for subsequent high-temperature calcination. It also helps control the initial growth of material particles, making their size distribution more uniform, and assisting in controlling crystal growth during subsequent high-temperature treatments. The second calcination treatment helps fully form and optimize the material crystals, generating a more stable and uniform crystal structure and improving material performance. It further removes residual impurities and incomplete reaction products, improving the purity and quality of the material. It also reduces lattice defects and irregular structures in the material, improving its uniformity and stability.

[0089] In another aspect, the present invention provides a positive electrode plate, comprising a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the ternary positive electrode composite material as described above or the ternary positive electrode composite material prepared as described above.

[0090] The present invention does not particularly limit the specific type of the positive electrode current collector, and conventional materials in the art can be selected, such as at least one of aluminum foil and nickel foil.

[0091] It can be understood that the positive electrode active material layer may also include a conductive agent and a binder. The present invention does not particularly limit the specific types of the conductive agent and the binder. The conductive agent, the binder and other components can be selected from conventional substances in the field. For example, the conductive agent can be selected from one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene, and the binder can be selected from one or more of polyvinylidene fluoride (PVDF), acrylic modified PVDF, polyacrylate polymers, polyimide, styrene-butadiene rubber, and styrene-propylene rubber.

[0092] The positive electrode sheet of the present invention can be prepared by conventional technical means in the field. Specifically, the above-mentioned ternary positive electrode composite material, conductive agent, and binder can be uniformly dispersed in a solvent to obtain a positive electrode active layer slurry, and then the positive electrode active layer slurry is coated on at least one functional surface of the positive electrode collector. After drying, the positive electrode sheet of the present invention can be obtained.

[0093] The positive electrode plate provided by the present invention includes the above-mentioned ternary positive electrode composite material, so after being used in a battery, the rate performance and cycle stability of the battery can be significantly improved.

[0094] In another aspect, the present invention provides a battery comprising the positive electrode sheet as described above.

[0095] It is conceivable that the battery of the present invention includes, in addition to the above-mentioned positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.

[0096] The present invention is not strictly limited to the negative electrode active material in the negative electrode plate, such as at least one of graphite, hard carbon, soft carbon, mesophase carbon microbeads, silicon-based negative electrode materials (mainly including silicon oxide, silicon-carbon negative electrode), tin-based negative electrode materials (mainly including tin, tin alloy), etc.

[0097] The present invention is not strictly limited to the choice of electrolyte. For example, the solvent can be ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), difluoroethylene carbonate (DFEC), dipropyl carbonate, ethyl methyl carbonate (EMC), ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, sulfolane, γ-butyrolactone, etc.; the lithium salt can be, for example, one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI).

[0098] The present invention does not strictly limit the material selection of the diaphragm, such as one of polypropylene diaphragm (PP), polyethylene diaphragm (PE), polypropylene / polyethylene double-layer composite film (PP / PE), polyimide electrospun diaphragm (PI), polypropylene / polyethylene / polypropylene three-layer composite film (PP / PE / PP), cellulose non-woven fabric diaphragm, and diaphragm with ceramic coating.

[0099] During battery preparation, the positive electrode sheet, separator, and negative electrode sheet are wound or stacked to form a bare cell, which is then encapsulated in a pre-stamped aluminum-plastic film bag. The encapsulated cells are dried at 85°C, and then the electrolyte is injected into the dried cells. After the cells are stored, formed, and resealed, the battery is complete.

[0100] In another aspect, the present invention provides an electrical device comprising the battery as described above.

[0101] The present invention is not limited to the specific types of electrical devices, and can include electric vehicles, mobile phones, smart homes, robots, drones, electronic cigarettes, speakers, and any other devices that require batteries to power them.

[0102] The electrical equipment provided by the present invention includes the above-mentioned battery and thus has good electrochemical performance and stability.

[0103] Hereinafter, the ternary composite cathode material provided by the present invention will be described in detail through specific examples.

[0104] Unless otherwise specified, the reagents, materials, and instruments used in the following examples are conventional reagents, conventional materials, and conventional instruments in the art and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0105] Example 1

[0106] The preparation method of the ternary cathode composite material provided in this embodiment includes the following steps:

[0107] 1. Add 80 mL of deionized water to a 200 mL autoclave and stir (300 r / min, 2.5 cm long olive-shaped samarium cobalt magnetic stirrer) 0.1 mol of Ni (2 μm in diameter) 0.5 Co 0.2 Mn 0.3 (OH)2 and 0.12 mol of LiOH·H2O were added to a reactor. The reactor was heated to 250°C in an oven for 4 hours while stirring (400 rpm, 2.5 cm long olive-shaped samarium-cobalt magnetic stir bar) for the first hydrothermal reaction. The reaction mixture was then cooled to room temperature to obtain a suspension of the ternary cathode material intermediate.

[0108] 2. Add 0.0006 mol of NH4H2PO4 to the suspension of the ternary cathode material intermediate and stir for 5 minutes. Then add 0.00034 mol of (CH3CH3CHO)4Ti and stir for 5 minutes. Then add 0.00006 mol of Al(NO3)3·9H2O. Under stirring (400 r / min, 2.5 cm long olive-shaped samarium cobalt magnetic stirrer), heat the reactor to 180°C in an oven and keep it warm for 12 hours to carry out the second hydrothermal reaction. After the product cools to room temperature, vacuum filtration (membrane pore size: 0.22 μm) is used to collect the solid product and wash it three times with deionized water. The product is dried at 90°C for 12 hours to obtain the coated Li 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary positive electrode composite material intermediate.

[0109] 3. The above-mentioned ternary cathode composite intermediate was first heated to 500°C at 5°C / min in air for 6 h for the first calcination treatment, and then heated to 900°C for 10 h for the second calcination treatment to obtain a surface uniformly coated fast ion conductor Li 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn 0.3 O2, wherein the molar weight of the fast ion conductor calculated by step 2 is 0.0002 mol, and the molar weight of the ternary material core calculated by step 1 is 0.1 mol, and the molar ratio of the two is 0.2%.

[0110] Example 2

[0111] The preparation method of the ternary cathode composite material provided in this embodiment includes the following steps:

[0112] 1. Add 80 mL of deionized water to a 200 mL autoclave and stir (400 r / min, 2.5 cm long olive-shaped samarium cobalt magnetic stirrer) 0.1 mol of Ni 0.5 Co 0.2 Mn 0.3 (OH)2 and 0.12 mol of LiOH·H2O were added to a reactor. The reactor was heated to 250°C in an oven and maintained for 4 hours while stirring (400 rpm, using a 2.5 cm long olive-shaped samarium-cobalt magnetic stirrer) for the first hydrothermal treatment. The reactor was then cooled naturally to room temperature to obtain a suspension of the ternary cathode material intermediate.

[0113] 2. Add 0.0006 mol of NH4H2PO4 to the suspension of the ternary cathode material intermediate and stir for 5 minutes. Then add 0.00038 mol of (CH3CH3CHO)4Ti and stir for 5 minutes. Then add 0.00002 mol of Al(NO3)3·9H2O. While stirring (400 r / min, 2.5 cm long olive-shaped samarium cobalt magnetic stirrer), heat the reactor to 180°C in an oven for 12 hours. After the product cools to room temperature, vacuum filtration (membrane pore size: 0.22 μm) is used to collect the solid product and wash it three times with deionized water. The product is dried at 90°C for 12 hours and then subjected to a second hydrothermal treatment to obtain the coated Li 1.1 Ti 1.9 Al 0.1 (PO4)3 ternary positive electrode composite material intermediate.

[0114] 3. The ternary cathode composite material intermediate was first heated to 500°C at 5°C / min in air for 6 h for the first calcination treatment, and then heated to 900°C for 10 h for the second calcination treatment to obtain a surface uniformly coated fast ion conductor Li 1.1 Ti 1.9 Al 0.1 (PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn 0.3 O2, wherein the molar weight of the fast ion conductor calculated by step 2 is 0.0002 mol, and the molar weight of the ternary material core calculated by step 1 is 0.1 mol, and the molar ratio of the two is 0.2%.

[0115] Example 3

[0116] The preparation method of the ternary cathode composite material provided in this embodiment includes the following steps:

[0117] 1. Add 80 mL of deionized water to a 200 mL autoclave and stir (400 r / min, 2.5 cm long olive-shaped samarium cobalt magnetic stirrer) 0.1 mol of Ni 0.5 Co 0.2 Mn 0.3 (OH)2 and 0.12 mol of LiOH·H2O were added to a reactor. The reactor was heated to 250°C in an oven and maintained for 4 hours while stirring (400 rpm, using a 2.5 cm long olive-shaped samarium-cobalt magnetic stirrer) for the first hydrothermal treatment. The reactor was then cooled naturally to room temperature to obtain a suspension of the ternary cathode material intermediate.

[0118] 2. Add 0.0006 mol of NH4H2PO4 to the ternary cathode material intermediate suspension and stir for 5 minutes. Then add 0.0003 mol of (CH3CH3CHO)4Ti and stir for 5 minutes. Then add 0.0001 mol of Al(NO3)3·9H2O. While stirring (400 r / min, 2.5 cm long olive-shaped samarium cobalt magnetic stirrer), heat the reactor to 180°C in an oven for 12 hours. After the product cools to room temperature, vacuum filtration (membrane pore size: 0.22 μm) collects the solid product and washes it three times with deionized water. The product is dried at 90°C for 12 hours and then subjected to a second hydrothermal treatment to obtain the coated Li 1.5 Ti 1.5 Al 0.5 (PO4)3 ternary positive electrode composite material intermediate.

[0119] 3. The above-mentioned ternary cathode composite intermediate was first heated to 500°C at 5°C / min in air for 6 h for the first calcination treatment, and then heated to 900°C for 10 h for the second calcination treatment to obtain a surface uniformly coated fast ion conductor Li 1.5 Ti 1.5 Al 0.5 (PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn 0.3 O2, wherein the molar weight of the fast ion conductor calculated by step 2 is 0.0002 mol, and the molar weight of the ternary material core calculated by step 1 is 0.1 mol, and the molar ratio of the two is 0.2%.

[0120] Example 4

[0121] The preparation method of the ternary cathode composite material provided in this embodiment includes the following steps:

[0122] 1. Add 80 mL of deionized water to a 200 mL autoclave and stir (400 r / min, 2.5 cm long olive-shaped samarium cobalt magnetic stirrer) 0.1 mol of Ni 0.5 Co 0.2 Mn 0.3 (OH)2 and 0.12 mol of LiOH·H2O were added to a reactor. The reactor was heated to 250°C in an oven and maintained for 4 hours while stirring (400 rpm, using a 2.5 cm long olive-shaped samarium-cobalt magnetic stirrer) for the first hydrothermal treatment. The reactor was then cooled naturally to room temperature to obtain a suspension of the ternary cathode material intermediate.

[0123] 2. Add 0.0003 mol of NH4H2PO4 to the suspension of the ternary cathode material intermediate and stir for 5 minutes. Then add 0.00017 mol of (CH3CH3CHO)4Ti (tetraisopropyl titanate) and stir for 5 minutes. Then add 0.00003 mol of Al(NO3)3·9H2O. While stirring (400 r / min, 2.5 cm long olive-shaped samarium cobalt magnetic stirrer), heat the reactor to 180°C in an oven and keep it warm for 12 hours for the second hydrothermal treatment. After the product cools to room temperature, collect the solid product by vacuum filtration (filter membrane pore size: 0.22μm) and wash it three times with deionized water. The product is dried at 90°C for 12 hours to obtain the coated Li 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary positive electrode composite material intermediate.

[0124] 3. The above-mentioned ternary cathode composite intermediate was first heated to 500°C at 5°C / min in air for 6 h for the first calcination treatment, and then heated to 900°C for 10 h for the second calcination treatment to obtain a surface uniformly coated fast ion conductor Li 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn 0.3 O2, wherein the molar weight of the fast ion conductor calculated by step 2 is 0.0001 mol, and the molar weight of the ternary material core calculated by step 1 is 0.1 mol, and the molar ratio of the two is 0.1%.

[0125] Example 5

[0126] The preparation method of the ternary cathode composite material provided in this embodiment includes the following steps:

[0127] 1. Add 80 mL of deionized water to a 200 mL autoclave and stir (400 r / min, 2.5 cm long olive-shaped samarium cobalt magnetic stirrer) 0.1 mol of Ni 0.5 Co 0.2 Mn 0.3 (OH)2 and 0.12 mol of LiOH·H2O were added to a reactor. The reactor was heated in an oven to 250°C for 4 hours while stirring (400 rpm, using a 2.5 cm long olive-shaped samarium-cobalt magnetic stirrer bar) for the first hydrothermal treatment. The reactor was then cooled naturally to room temperature to obtain a suspension of the ternary cathode material intermediate.

[0128] 2. Add 0.0015 mol of NH4H2PO4 to the ternary cathode material intermediate suspension and stir for 5 minutes. Then add 0.00085 mol of (CH3CH3CHO)4Ti (tetraisopropyl titanate) and stir for 5 minutes. Then add 0.00015 mol of Al(NO3)3·9H2O. While stirring (400 r / min, 2.5 cm long olive-shaped samarium cobalt magnetic stirrer), heat the reactor to 180°C in an oven for 12 hours. After the product cools to room temperature, vacuum filtration (membrane pore size: 0.22 μm) is used to collect the solid product and wash it three times with deionized water. The product is dried at 90°C for 12 hours and then subjected to a second hydrothermal treatment to obtain the coated Li 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary positive electrode composite material intermediate.

[0129] 3. The above-mentioned ternary cathode composite intermediate was first heated to 500°C at 5°C / min in air for 6 h for the first calcination treatment, and then heated to 900°C for 10 h for the second calcination treatment to obtain a surface uniformly coated fast ion conductor Li 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn 0.3 O2, wherein the molar weight of the fast ion conductor calculated by step 2 is 0.0005 mol, and the molar weight of the ternary material core calculated by step 1 is 0.1 mol, and the molar ratio of the two is 0.5%.

[0130] Example 6

[0131] The preparation method of the ternary cathode composite material provided in this embodiment is basically the same as that in Example 1, except that:

[0132] In step 2, 0.003 mol of NH4H2PO4 was added to the suspension of the ternary cathode material intermediate and stirred for 5 min, followed by the addition of 0.0017 mol of (CH3CH3CHO)4Ti and the stirring for 5 min, and then 0.003 mol of Al(NO3)3·9H2O.

[0133] In this embodiment, the surface of the prepared 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn 0.3 O2, wherein the molar weight of the fast ion conductor is 0.001 mol, the molar weight of the ternary material core is 0.1 mol, and the molar ratio of the two is 1%.

[0134] Example 7

[0135] The preparation method of the ternary cathode composite material provided in this embodiment is basically the same as that in Example 1, except that:

[0136] In step 1, the temperature of the first hydrothermal reaction was changed to 200°C and the holding time was changed to 3 h;

[0137] In step 3, the temperature of the first calcination treatment is replaced with 400° C., and the holding time is replaced with 4 hours; the temperature of the second calcination treatment is replaced with 800° C., and the holding time is replaced with 8 hours.

[0138] In this embodiment, the surface of the prepared 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn 0.3 O2, wherein the molar weight of the fast ion conductor is 0.0002 mol, the molar weight of the ternary material core is 0.1 mol, and the molar ratio of the two is 0.2%.

[0139] Example 8

[0140] The preparation method of the ternary cathode composite material provided in this embodiment is basically the same as that in Example 1, except that:

[0141] In step 1, the temperature of the first hydrothermal reaction was changed to 200°C and the holding time was changed to 6 h;

[0142] In step 3, the temperature of the first calcination treatment is replaced with 600° C., and the holding time is replaced with 8 h; the temperature of the second calcination treatment is replaced with 950° C., and the holding time is replaced with 12 h.

[0143] In this embodiment, the surface of the prepared 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn 0.3 O2, wherein the molar weight of the fast ion conductor is 0.0002 mol, the molar weight of the ternary material core is 0.1 mol, and the molar ratio of the two is 0.2%.

[0144] Example 9

[0145] The preparation method of the ternary cathode composite material provided in this embodiment is basically the same as that in Example 1, except that:

[0146] In step 1, Ni with a particle size of about 2 μm 0.5 Co 0.2 Mn 0.3 (OH)2 is replaced by Ni with a particle size of about 1.6 μm 0.5 Co 0.2 Mn 0.3 (OH)2.

[0147] In this embodiment, the surface of the prepared 1.3 Ti 1.7 Al 0.3(PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn 0.3 O2, wherein the molar weight of the fast ion conductor is 0.0002 mol, the molar weight of the ternary material core is 0.1 mol, and the molar ratio of the two is 0.2%.

[0148] Example 10

[0149] The preparation method of the ternary cathode composite material provided in this embodiment is basically the same as that in Example 1, except that:

[0150] In step 1, Ni with a particle size of about 2 μm 0.5 Co 0.2 Mn 0.3 (OH)2 is replaced by Ni with a particle size of about 4 μm 0.5 Co 0.2 Mn 0.3 (OH)2.

[0151] In this embodiment, the surface of the prepared 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn 0.3 O2, wherein the molar weight of the fast ion conductor is 0.0002 mol, the molar weight of the ternary material core is 0.1 mol, and the molar ratio of the two is 0.2%.

[0152] Example 11

[0153] The preparation method of the ternary cathode composite material provided in this embodiment is basically the same as that in Example 1, except that:

[0154] In step 1, Ni with a particle size of about 2 μm 0.5 Co 0.2 Mn 0.3 (OH)2 is replaced by Ni with a particle size of about 6.5 μm 0.5 Co 0.2 Mn 0.3 (OH)2.

[0155] In this embodiment, the surface of the prepared 1.3 Ti 1.7 Al 0.3 (PO4)3 ternary cathode composite material, wherein the core of the ternary material is composed of LiNi 0.5 Co 0.2 Mn0.3 O2, wherein the molar weight of the fast ion conductor is 0.0002 mol, the molar weight of the ternary material core is 0.1 mol, and the molar ratio of the two is 0.2%.

[0156] Comparative Example 1

[0157] The preparation method of the ternary positive electrode composite material provided in this comparative example comprises the following steps:

[0158] 0.05 mol of LiNi 0.5 Co 0.2 Mn 0.3 O2, 0.0001 mol of Li 1.3 Ti 1.7 Al 0.3 (PO₄)₃ was added to a ball mill, along with polyurethane grinding balls (1:1 ball-to-material ratio). The mixture was mixed in a ball mill at 280 rpm for 12 hours (with a 5-minute pause every 30 minutes). The product was heated in air at a rate of 5°C / min to 500°C for 6 hours, then to 900°C for 10 hours to produce a ternary cathode composite material coated with a fast ion conductor.

[0159] Comparative Example 2

[0160] The ternary positive electrode composite material provided in this comparative example is basically the same as that in comparative example 1, except that: 1.3 Ti 1.7 Al 0.3 The molar amount of (PO4)3 was changed from 0.0001 mol to 0.00015 mol.

[0161] Test Case

[0162] 1. Physical property testing

[0163] The ternary cathode composite materials provided in all embodiments and comparative examples were tested, including the following steps:

[0164] 1) Coverage test

[0165] Use an energy spectrometer to randomly select 50 secondary particles, calculate the ratio of the coverage area of the three elements Ti, Al, and P on the surface of the secondary particles to the surface area of the secondary particles, and take the average value as the coverage rate;

[0166] It should be noted that the coverage area of the three elements Ti, Al and P on the surface of secondary particles at the same time refers to the situation where the surface is covered with the three elements Ti, Al and P at the same time. If only one or two elements among Ti, Al and P are covered, it is not within the scope of statistics.

[0167] 2) Free lithium ion content detection

[0168] A potentiometric titrator is used to test the residual alkali content of the ternary positive electrode composite material, which is the free lithium ion content.

[0169] 3) Thickness detection

[0170] 50 secondary particles were randomly selected, and the thickness of the coating layer on the surface of the 50 secondary particles was randomly measured using a transmission electron microscope, and the average value was taken.

[0171] 4) Al element content, Ti element content, Ti element content detection

[0172] Inductively coupled plasma emission spectrometry was used to test the contents of Al, Ti and P in the ternary positive electrode composite material.

[0173] 5) Primary particle size and secondary particle size

[0174] 200 secondary particles and 200 primary particles were randomly selected, and the sizes of the selected 200 secondary particles and 200 primary particles were observed using a scanning electron microscope, and the average value was taken.

[0175] It should be noted that the secondary particles and primary particles selected in the above test process are randomly distributed, which can more accurately reflect the coverage, thickness, element content and size corresponding to all secondary particles, as well as the size of the primary particles.

[0176] The specific test results are shown in Table 1.

[0177] Table 1

[0178]

[0179] 2. Electrochemical performance test

[0180] The ternary cathode composite materials provided in all examples and comparative examples were used to prepare 2025 coin-shaped batteries according to the following steps: The prepared ternary cathode materials were ground with nanocarbon black and PVDF (polyvinylidene fluoride) at a mass ratio of 8:1:1 using NMP (1-methyl-2-ethylpyrrolidone as the solvent) for 30 minutes. The slurry was then evenly coated on aluminum foil and vacuum-dried at 110°C for 12 hours. The dried electrode was then formed into 14 mm φ discs. In an inert atmosphere glove box, 2025 coin-shaped batteries (1C = 165 mAh / g) were assembled using metallic lithium as the counter electrode and 1 mol / L LiPF6 (EC:DMC:EMC = 1:1:1 by volume) as the electrolyte.

[0181] 1) High temperature cycle test

[0182] Test method: Cycle three times at 45°C and 0.1C rate to activate (3-4.3V), then cycle three times at 1C rate to constant capacity, and finally cycle at 1C rate in the 14%-97% SOC range until the capacity retention rate drops below 80%. Record the number of cycles. Specific test results are shown in Table 2.

[0183] 2) X-ray photoelectron spectroscopy was performed on the ternary cathode composite material of Example 1 before being assembled into a button cell, and after the button cell was assembled, the button cell was charged at a rate of 1C at 25°C to an upper voltage limit of 4.2V, and the X-ray photoelectron spectroscopy of the ternary cathode composite material in the charged button cell was tested.

[0184] Figure 1 is the X-ray photoelectron spectrum of the ternary positive electrode composite material of Example 1, Figure 2 This is the X-ray photoelectron spectrum of the button battery made of the ternary positive electrode composite material of Example 1 after charging; Figure 1 and Figure 2 It can be seen that the X-ray photoelectron spectrum of the ternary positive electrode composite material before battery charging includes Ti 4+ Spectral peak; The X-ray photoelectron spectrum of the ternary positive electrode composite material after battery charging includes Ti 4+ Spectral peak and Ti 3+ The peak of Ti in the coating layer 4+ The peaks participate in the redox reaction during the electrical cycle to form Ti 3+ .

[0185] 3) Lithium ion diffusion coefficient

[0186] Test the electrochemical impedance spectroscopy of the button battery and use formula 1 to calculate the lithium ion diffusion coefficient of the button battery ( ):

[0187] (1)

[0188] R is the gas constant (8.314 J·K -1 •mol -1 ), T is the absolute temperature (298 K), A is the area of the electrode immersed in the solution, n is the number of transferred electrons, and F is the Faraday constant (96485 C·mol -1 ), C is the concentration of lithium ions in the electrode, σ is the Warburg coefficient (through Z'-ω -1 / 2 Specific test results are shown in Table 2.

[0189] Table 2

[0190]

[0191] Combining the values in Table 1 and Table 2, we can see that:

[0192] 1) Comparative Example 1 directly coats the ternary cathode material with the titanium aluminum phosphate coating source through solid-phase mixing. The resulting coating layer is relatively thick, and the surface free lithium ion content is significantly increased, resulting in a significantly poor coverage rate. Comparative Example 2, based on Comparative Example 1, reduces the surface free lithium ion content by increasing the thickness of the coating layer, but the coverage rate is still low. In contrast, in Examples 1-3, with the same molar ratio of the coating layer, a hydrothermal method is first used to synthesize an intermediate of the ternary cathode material, and then the intermediate is directly coated with fast ions instead. Finally, calcination is performed to convert the ternary cathode material intermediate in the core into a ternary cathode material. The resulting ternary composite material has a thin coating layer and a significantly higher coverage rate. The free lithium ion content does not exceed 400 ppm. Accordingly, the number of cycles and lithium ion diffusion coefficients of Examples 1-3 are also significantly higher than those of Comparative Examples 1-2, which can provide batteries with more excellent cycle performance and rate performance.

[0193] 2) By comparing Examples 1 to 3, it can be seen that when the molar ratio of the coating layer and the thickness of the coating layer are basically the same, the ratio of the Al content and the Ti content in the coating layer of Example 1 is more suitable. A moderate Al content can make the ternary composite material have higher electrical conductivity, and a moderate Ti content is conducive to making the ternary composite material have higher ion conductivity. Therefore, the ratio of the Al content and the Ti content in Example 1 is more suitable, so its electrical conductivity and ion conductivity are better balanced, so that the cycle performance and rate performance of the battery are the best. A higher or lower ratio of the Al and Ti content in Examples 2 and 3 is not conducive to the battery achieving optimal cycle performance and rate performance.

[0194] 3) By comparing Examples 1, 4 to 6, it can be seen that too little or too much molar ratio of the fast ion conductor coating layer to the ternary material core has a significant effect on the thickness of the coating layer, the coverage rate, the free lithium ion content, and the size of the primary and secondary particles. When the molar ratio of the fast ion conductor coating layer is too large, it is not conducive to the diffusion of lithium ions, which is obviously detrimental to the rate performance of the battery. It also restricts the outward diffusion of alkaline substances, causing the alkaline substances to accumulate inside the coating layer, resulting in an increase in the free alkali content, which is also detrimental to the cycle performance of the battery. When the molar ratio of the coating layer is too small, the coating is uneven, the coverage rate is low, and it is not conducive to improving the battery cycle performance and rate performance.

[0195] 4) By comparing Example 1 and Examples 7 to 11, it can be seen that when the primary particle size of the ternary positive electrode composite material is in the range of 100 nm to 500 nm and the secondary particle size is in the range of 1.6 to 6.5 μm, the ternary positive electrode composite material can achieve a high coverage rate and a low free lithium ion content, thereby enabling the battery to have both excellent cycle performance and rate performance.

[0196] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ternary positive electrode composite material, characterized in that: It includes a ternary material core and a coating layer coated on the surface of the core, wherein the coating layer includes a fast ion conductor, and the composition of the fast ion conductor is Li 1+x Ti 2-x Al x (PO4)3,0<x≤0.5; The coating rate of the coating layer is ≥90%; The free lithium ion content on the surface of the ternary positive electrode composite material is ≤600ppm.

2. The ternary cathode composite material according to claim 1, characterized in that The molar ratio of the fast ion conductor to the ternary material core is 0.1% to 0.5%.

3. The ternary cathode composite material according to claim 1 or 2, characterized in that: The thickness of the coating layer is ≤10 nm.

4. The ternary cathode composite material according to any one of claims 1 to 3, characterized in that: The Al content in the ternary positive electrode composite material is ≤600 ppm, preferably 110-210 ppm; And / or, the Ti element content in the ternary positive electrode composite material is ≤4500 ppm, preferably 1300-1900 ppm; And / or, the P element content in the ternary positive electrode composite material is ≤4500 ppm, preferably 1500~2100 ppm.

5. The ternary cathode composite material according to any one of claims 1 to 4, characterized in that: The fast ion conductor includes Ti 4+ .

6. The ternary cathode composite material according to any one of claims 1 to 5, characterized in that: The composition of the core of the ternary material is Li a Ni 1-b-c Co b Mn c O2, 1<a≤1.1, 0.3<1-bc≤0.8, 0 <b≤0.4,0<c≤0.4。 7. The ternary cathode composite material according to any one of claims 1 to 6, characterized in that: The core of the ternary material is a secondary particle formed by the agglomeration of primary particles; The size of the primary particles is 100-500 nm, and the size of the secondary particles is 1.6-6.5 μm.

8. A method for preparing the ternary cathode composite material according to any one of claims 1 to 7, characterized in that: The preparation method comprises the following steps: 1) subjecting a raw material system comprising nickel, cobalt, and manganese hydroxides and lithium hydroxide to a first hydrothermal reaction to obtain a ternary cathode material intermediate suspension; 2) adding a phosphorus source, a titanium source, and an aluminum source to the suspension of the ternary cathode material intermediate to obtain a ternary cathode composite material intermediate through a second hydrothermal reaction; 3) calcining the ternary cathode composite material intermediate to obtain the ternary cathode composite material.

9. The preparation method according to claim 8, characterized in that In step 1), the temperature of the first hydrothermal reaction is 200-280°C and the time is 3-6 hours; And / or, in step 2), the temperature of the second hydrothermal reaction is 170°C to 200°C, and the time is 12 to 24 hours; And / or, in step 3), the calcination treatment includes a first calcination treatment and a second calcination treatment performed sequentially, the first calcination treatment is performed at a temperature of 400-600° C. and for a time of 4-8 hours; the second calcination treatment is performed at a temperature of 800-950° C. and for a time of 8-12 hours.

10. A positive electrode plate, characterized in that: The invention comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the ternary positive electrode composite material according to any one of claims 1 to 7 or the ternary positive electrode composite material prepared by the preparation method according to claim 8 or 9.

11. A battery, characterized in that: Including the positive electrode sheet according to claim 10.

12. An electrical device, characterized in that: Including the battery according to claim 11.

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