Cathode material and method for manufacturing the same

Abstract

This invention discloses a cathode material and its manufacturing method. The material includes a cathode active material and a coating layer, wherein the coating layer covers the outer surface of the cathode active material. The coating layer includes coating material particles with a core-shell structure. The core of the core-shell structure is an adsorbent material, and the outer shell is a deoxygenating material. The adsorbent material includes a porous adsorbent material. The porous adsorbent material in the core-shell structure can directly absorb oxygen released from the coated cathode active material. The deoxygenating material in the outer shell of the core-shell structure can directly capture the adsorbed oxygen molecules from the adsorbent material, allowing the adsorbent material to continue to free up adsorption space, thereby improving adsorption efficiency and safety performance. This effectively adsorbs and removes oxygen released from the cathode active material inside the cathode material, improving the safety performance of the battery.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to cathode materials and their manufacturing methods. Background Technology

[0002] Currently, increasing the nickel content of cathode materials is one of the important directions for improving battery energy density. However, increasing the nickel content can lead to a phase transition in the cathode material under high temperature and pressure, releasing a large amount of oxygen. The released oxygen reacts with the electrolyte and negative electrode in the battery, generating a large amount of heat, causing the separator to shrink and break, resulting in short circuits and thermal runaway. Therefore, suppressing the release of oxygen and heat from the cathode material and increasing the stability of the cathode material can effectively delay the occurrence of thermal runaway in the cell, thereby improving the cell's safety performance.

[0003] Currently, the main methods for suppressing oxygen release and heat generation from battery cathode materials are adding porous oxygen-absorbing additives to the cathode sheet and coating the surface of the cathode material with a layer of elemental metal. Adding porous oxygen-absorbing additives to the cathode sheet can absorb the oxygen released by the cathode material, thus mitigating oxygen release. However, these materials generally have low conductivity, which can affect electron conduction in the active layer, increasing internal resistance and impacting cell performance. Furthermore, insufficient contact between the oxygen absorber and the active material can lead to untimely or missed absorption of released oxygen. Coating the surface of the cathode material with a layer of elemental metal allows the elemental metal to react with the released oxygen, achieving oxygen absorption. However, during cycling, the elemental metal can detach from the cathode material due to deformation and breakage, forming metallic foreign matter. This can easily increase self-discharge and internal short circuits, increasing safety hazards. Summary of the Invention

[0004] To address the problems of the prior art, this application provides a cathode material and its manufacturing method, which can effectively adsorb and remove oxygen released by the cathode active material inside the cathode material, thereby improving the safety performance of the battery.

[0005] Specifically, in the first aspect, this application provides a positive electrode material, the material comprising a positive electrode active material and a coating layer, the coating layer being coated on the outer surface of the positive electrode active material;

[0006] The coating layer includes coating material particles, which have a core-shell structure. The core of the core-shell structure is an adsorbent material, and the outer shell is a deoxygenating material. The adsorbent material includes porous adsorbent materials.

[0007] In some embodiments, the thickness of the coating layer is 0.5-3 μm; the coating material particles further include a liquid-retaining material layer, which coats the outer surface of the deoxidizing material.

[0008] In some embodiments, the mass ratio of the adsorbent material, the deoxygenating material, and the liquid-retaining material layer is (80-90):(5-10):(5-10);

[0009] And / or,

[0010] The liquid-retaining material includes one or a mixture of polyacrylate, diethyl polyacrylate, and polymethyl methacrylate;

[0011] And / or,

[0012] The thickness of the liquid-retaining material layer is 200nm-1000nm.

[0013] In some embodiments, the porous adsorbent material includes one or more of porous carbon materials, porous MOFs, porous ZIFs, and porous silicon-carbon materials;

[0014] And / or, the deoxidizing material comprises one or more of the following: catechol, pyrogallol, p-methoxyphenol, cresol, tert-butylcatechol, p-phenylenediamine, polyethyleneimine, acetyldopamine, ethylenediamine, and diphenylamine; and / or;

[0015] The thickness of the outer shell layer formed by the deoxidizing material is 50nm-200nm.

[0016] In some embodiments, the coating layer further includes a conductive agent and a binder, wherein the mass ratio of the coating material particles to the conductive agent and the binder is (90-95):(5-10):(2-5);

[0017] And / or, the conductive agent includes one or more of graphene, conductive graphite, and carbon nanotubes;

[0018] And / or, the adhesive comprises one or more of PVDF, PTFE, CMC, and PAA.

[0019] In some embodiments, the positive electrode active material includes one or more mixtures of lithium nickel cobalt manganese oxide ternary materials, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, and layered oxides; preferably, the positive electrode active material includes materials with the general chemical formula LiNi. x Co y High-nickel ternary materials of MnO2, wherein x≥0.7.

[0020] Secondly, this application provides a method for manufacturing a cathode material, the method comprising:

[0021] The first porous precursor material particles were prepared by synthesizing cobalt salt and 2-methylimidazole.

[0022] The first porous precursor material particles are combined with a deoxidizing material to prepare coated material particles.

[0023] The coating material particles are mixed with a conductive agent and a binder to obtain a coating layer material;

[0024] A positive electrode material is prepared by coating the surface of the positive electrode active material with the coating layer material.

[0025] In some embodiments, the mass ratio of the cobalt salt to 2-methylimidazole is 1:(3-6);

[0026] And / or,

[0027] When preparing the first porous precursor material particles and deoxygenating material into coating material particles, a liquid-retaining material is also added.

[0028] And / or,

[0029] The mass ratio of the coating material particles to the conductive agent and the binder is (90-95):(5-10):(2-5).

[0030] In some embodiments, the preparation of the first porous precursor material particles by synthesizing cobalt salt and 2-methylimidazole includes:

[0031] Cobalt salt and 2-methylimidazole were uniformly mixed in a solvent to prepare a mixed solution, and then the mixture was heated to react and synthesize a three-dimensional porous precursor material.

[0032] The three-dimensional porous precursor material was ball-milled to prepare the first porous precursor material particles.

[0033] And / or,

[0034] The step of preparing coating material particles by combining the first porous precursor material particles with deoxidizing material and liquid-retaining material includes:

[0035] After uniformly dispersing the first porous precursor material particles into a solution containing deoxygenating material, centrifuging, filtering, and air-drying are performed to obtain the second porous precursor material particles with deoxygenating material adsorbed on the surface.

[0036] The liquid-retaining material was ball-milled and then uniformly dispersed in a solvent to prepare a polymer colloidal solution.

[0037] The polymer gel solution is uniformly coated onto the surface of the second porous precursor material particles by spray drying, and then heated and dried to obtain coated material particles.

[0038] In some embodiments, the solvent includes at least one of water, DMF, ethylene glycol, and methanol;

[0039] And / or,

[0040] The concentration of the mixed solution is 10-100 g / L;

[0041] And / or,

[0042] The temperature of the heating reaction is 100-200℃, and the reaction time is 1-6h;

[0043] And / or,

[0044] The solvent in the solution containing the deoxygenating material is at least one of water, ethanol and methanol, and the concentration of the solution containing the deoxygenating material is 5-10 g / L.

[0045] And / or,

[0046] The spray drying temperature is 60-100℃.

[0047] According to the specific embodiments provided in this application, the following technical effects are disclosed:

[0048] In this application, a coating layer composed of core-shell structured coating material particles is coated on the surface of the positive electrode active material. The core of the core-shell structure of the coating material particles is an adsorbent material that adsorbs oxygen released by the positive electrode active material, and the outer shell of the core-shell structure is a deoxygenating material that provides hydrogen atoms needed for free radicals to stabilize the oxidation reaction. The adsorbent material directly absorbs the oxygen released by the coated positive electrode active material. The deoxygenating material coated on the outer surface of the adsorbent material can directly capture the adsorbed oxygen molecules from the adsorbent material, allowing the adsorbent material to continue to free up adsorption space, thereby improving adsorption efficiency and safety performance. It can effectively adsorb and remove oxygen released by the positive electrode active material inside the positive electrode material, thereby improving the safety performance of the battery.

[0049] Furthermore, in this application, the deoxygenating material is coated with a liquid-retaining material, which on the one hand increases the liquid retention of the lithium battery and improves the cycle capacity, and on the other hand, due to the toughness of the polymer, improves the contact between the positive electrode active materials, reduces the contact resistance, and improves the electrochemical performance. Attached Figure Description

[0050] The disclosure of this application will become more readily understood with reference to the accompanying drawings. It will be readily understood by those skilled in the art that these drawings are for illustrative purposes only and are not intended to limit the scope of protection of this application. Furthermore, similar numbers in the drawings are used to denote similar components, wherein:

[0051] Figure 1 This is a schematic diagram of the structure of the cathode material provided in the embodiments of this application;

[0052] Figure 2 This is a schematic diagram of the structure of the coating material particles provided in the embodiments of this application.

[0053] Among them: 1. Positive electrode active material; 2. Coating layer; 21. Adsorbent material; 22. Deoxygenating material; 23. Liquid retention material layer. Detailed Implementation

[0054] Some embodiments of this application are described below with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this application and are not intended to limit the scope of protection of this application.

[0055] As described in the background section, high-nickel cathode materials release large amounts of oxygen under high temperature and pressure. This released oxygen reacts with the electrolyte and negative electrode in the battery, generating significant heat. This can cause the lithium battery separator to shrink and become damaged, leading to short circuits and thermal runaway. Currently, suppressing oxygen release and heat generation from electrode materials mainly involves adding porous oxygen-absorbing additives to the cathode sheet to absorb the oxygen released by the cathode material, and coating the surface of the cathode material with elemental metals to react with the released oxygen. However, adding porous oxygen-absorbing additives can affect electron conduction, impacting cell performance. Furthermore, insufficient contact with the active material can lead to delayed or even missed oxygen absorption. Coating with elemental metals can easily result in the elemental metals deforming and breaking off from the cathode material during battery cycling, forming metallic foreign objects. This can increase self-discharge and internal short circuits, increasing safety hazards.

[0056] To address the aforementioned issues, this application creatively proposes a cathode material and its manufacturing method. A coating layer composed of core-shell structured coating material particles is applied to the outer surface of the cathode active material. The core of the core-shell structure of the coating material particles is an adsorbent material that adsorbs oxygen released from the cathode active material, while the outer shell provides hydrogen atoms needed for free radicals to stabilize the oxidation reaction. The adsorbent material directly absorbs the oxygen released from the coated cathode active material. The deoxygenated material coating the outer surface of the adsorbent material can directly capture the adsorbed oxygen molecules from the adsorbent material, allowing the adsorbent material to continue to free up adsorption space, thus improving adsorption efficiency and safety performance. This effectively adsorbs and removes oxygen released from the cathode active material inside the cathode material, improving battery safety performance.

[0057] The following are optional technical solutions for this application, but are not intended to limit the technical solutions provided in this application. The technical objectives and beneficial effects of this application can be better achieved through the following optional technical solutions.

[0058] Firstly, this application provides a cathode material, referring to... Figure 1As shown, the positive electrode material includes a positive electrode active material 1 and a coating layer 2, with the coating layer 2 covering the outer surface of the positive electrode active material 1; the positive electrode active material 1 and the coating layer 2 covering the outer surface of the positive electrode active material 1 form a core-shell structure with the positive electrode active material 1 as the core and the coating layer 2 as the shell.

[0059] The coating layer 2 includes coating material particles, which have a core-shell structure. The core of the core-shell structure is an adsorbent material 21, and the outer shell is a deoxygenating material 22. The adsorbent material 21 includes porous adsorbent material.

[0060] In some embodiments, the thickness of the coating layer 2 is 0.5-3 μm; optionally, the thickness of the coating layer 2 can be 0.5 μm, 0.9 μm, 1.3 μm, 1.5 μm, 1.8 μm, 2.5 μm, 3 μm, or any thickness value within the above range. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0061] Reference Figure 2 As shown, the coating material particles also include a liquid-retaining material layer 23, which covers the outer surface of the deoxidizing material 22.

[0062] In some embodiments, the mass ratio of adsorbent material 21, deoxygenating material 22, and liquid-retaining material layer 23 is (80-90):(5-10):(5-10); and / or,

[0063] Liquid-retaining materials include one or more of polyacrylate, diethyl polyacrylic acid, and polymethyl methacrylate; and / or,

[0064] The thickness of the liquid-retaining material layer 23 is 200nm-1000nm.

[0065] For example, the mass ratio of adsorbent material 21, deoxygenating material 22, and liquid-retaining material layer 23 can be (80:5:5), (90:10:10), (85:7:8), (80:10:10), (90:5:5), (88:8:6), or any ratio within the range above. For space limitations and for the sake of brevity, this application will not exhaustively list all the specific ratios included in the stated range. The thickness of the liquid-retaining material layer can be 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 760nm, 800nm, 900nm, 1000nm, or any thickness value within the range above. For space limitations and for the sake of brevity, this application will not exhaustively list all the specific values ​​included in the stated range.

[0066] In some embodiments, the porous adsorbent material includes one or more of porous carbon materials, porous MOFs, porous ZIFs, and porous silicon-carbon materials;

[0067] And / or, the deoxidizing material 22 includes one or more of the following: catechol, pyrogallol, p-methoxyphenol, cresol, tert-butylcatechol, p-phenylenediamine, polyethyleneimine, acetyldopamine, ethylenediamine, and diphenylamine; and / or;

[0068] The thickness of the outer shell layer formed by the deoxidizing material 22 is 50nm-200nm. For example, the thickness of the outer shell layer formed by the deoxidizing material can be any thickness value within the range of 50nm, 70nm, 90nm, 110nm, 130nm, 150nm, 170nm, 190nm, 200nm or above. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific values ​​included in the range.

[0069] In some embodiments, the coating layer 2 further includes a conductive agent and a binder, wherein the mass ratio of the coating material particles to the conductive agent and the binder is (90-95):(5-10):(2-5); and / or, the conductive agent includes one or more of graphene, conductive graphite, and carbon nanotubes;

[0070] And / or, the adhesive includes one or more of PVDF, PTFE, CMC, and PAA.

[0071] For example, the mass ratio of the coating material particles to the conductive agent and the binder can be (90:5:2), (95:10:5), (90:10:5), (93:5:2), (94:10:5), (92.5:7:3), or any ratio within the above range. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific ratios included in the range.

[0072] Carbon nanotubes are preferred as the conductive agent to enhance the conductivity of the coating layer. Furthermore, the toughness of the polymer liquid retainer improves the contact performance between the coated cathode materials, thereby reducing contact resistance and enhancing the overall electrochemical performance of the lithium battery.

[0073] In some embodiments, the positive electrode active material 1 includes one or more of lithium nickel cobalt manganese oxide ternary materials, lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, and layered oxide compounds; preferably, the positive electrode active material includes materials with the general chemical formula LiNi. x Co y The high-nickel ternary material of MnO2, wherein x ≥ 0.7. For example, x can be 0.7, 1, 2, 2.5, 3, or any other point value greater than or equal to 0.7. Due to space limitations and for the sake of brevity, this application will not exhaustively list the specific point values ​​included in the range.

[0074] This application also provides a method for manufacturing a cathode material, the method comprising:

[0075] S1. The first porous precursor material particles were prepared by synthesizing cobalt salt and 2-methylimidazole.

[0076] Cobalt salts are substances composed of cobalt ions and acid radicals, and may also contain other ions in a certain proportion. In this application, the cobalt salt may be at least one of cobalt chloride, cobalt sulfate, cobalt nitrate, cobalt acetate, cobalt nitrate, or cobalt sulfate.

[0077] S2. Prepare coating material particles by combining the first porous precursor material particles with the deoxidizing material.

[0078] Deoxidizing materials include one or more of the following: catechol, pyrogallol, p-methoxyphenol, cresol, tert-butylcatechol, p-phenylenediamine, polyethyleneimine, acetyldopamine, ethylenediamine, and diphenylamine.

[0079] S3. Mix the coating material particles with the conductive agent and binder to obtain the coating layer material.

[0080] The conductive agent includes one or more of graphene, conductive graphite, and carbon nanotubes, and the binder includes one or more of PVDF, PTFE, CMC, and PAA.

[0081] S4. A positive electrode material is prepared by coating the surface of the positive electrode active material with a coating layer material.

[0082] In some embodiments, the mass ratio of cobalt salt to 2-methylimidazole is 1:(3-6);

[0083] And / or, when preparing coating material particles from the first porous precursor material particles and the deoxidizing material, a liquid-retaining material is also added; and / or,

[0084] The mass ratio of coating material particles to conductive agent and binder is (90-95):(5-10):(2-5).

[0085] For example, the mass ratio of cobalt salt to 2-methylimidazole is 1:3, 1:3.8, 1:4, 1:4.5, 1:5, 1:6, or any ratio within the above range. For space limitations and for the sake of brevity, this application will not exhaustively list all the specific ratios included in the range. The mass ratio of coating material particles to conductive agent and binder is 90:5:2, 90:10:5, 95:5:2, 93:5:2, 94:10:5, 92:7:3, 91.5:8:4, or any ratio within the above range. For space limitations and for the sake of brevity, this application will not exhaustively list all the specific ratios included in the range. In addition, when the first porous precursor material particles and deoxygenating material are prepared into coating material particles, a liquid-retaining material is also added. A layer of polymer liquid-retaining material is coated on the outside of the porous material. On the one hand, it can increase the liquid retention of the lithium battery and improve the cycle capacity. On the other hand, due to the toughness of the polymer, it improves the contact between the positive electrode active materials, reduces the contact resistance, and improves the electrochemical performance.

[0086] In some embodiments, step S1 includes:

[0087] S11. Cobalt salt and 2-methylimidazole are uniformly mixed in a solvent to prepare a mixed solution, and then heated to react and synthesize a three-dimensional porous precursor material.

[0088] S12. The first porous precursor material particles are prepared by ball milling the three-dimensional porous precursor material.

[0089] Step S2 includes:

[0090] S21. After uniformly dispersing the first porous precursor material particles into a solution containing deoxygenating material, centrifuge, filter, and air-dry to obtain the second porous precursor material particles with deoxygenating material adsorbed on the surface.

[0091] S22. After ball milling, the liquid-retaining material is uniformly dispersed in a solvent to prepare a polymer gel solution.

[0092] S23. The polymer gel solution is uniformly coated onto the surface of the second porous precursor material particles by spray drying, and then heated and dried to obtain coated material particles.

[0093] In some embodiments, the solvent includes at least one of water, DMF, ethylene glycol, and methanol;

[0094] And / or, the concentration of the mixed solution is 10-100 g / L;

[0095] And / or, the temperature of the heating reaction is 100-200℃, and the reaction time is 1-6h;

[0096] And / or, the solvent in the solution containing the deoxygenating material is at least one of water, ethanol and methanol, and the concentration of the solution containing the deoxygenating material is 5-10 g / L;

[0097] And / or, the spray drying temperature is 60-100℃.

[0098] In step S21, after the first porous precursor material particles are uniformly dispersed in a solution containing deoxygenating material, and before centrifugation, filtration and air drying are performed to obtain the second porous precursor material particles with deoxygenating material adsorbed on the surface, vacuum stirring is carried out for 6-12 hours to ensure that the first porous precursor material particles are uniformly dispersed in the solution containing deoxygenating material.

[0099] In step S4, the coating material obtained by uniformly mixing the coating material particles, conductive agent, and binder in step S3 is uniformly coated onto the surface of the positive electrode active material by spray drying to obtain a positive electrode material with a coating layer.

[0100] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents and instruments used, unless otherwise specified, are all commercially available conventional products.

[0101] Example 1

[0102] 1) Synthesis of the first porous precursor material

[0103] First, cobalt salt and 2-methylimidazole are uniformly mixed in water at a mass ratio of 1:4 to prepare a mixed solution with a concentration of 20 g / L. Then, the temperature is slowly raised to 120°C and the mixture is stirred for 4 hours to obtain a three-dimensional porous ZIF precursor material.

[0104] The three-dimensional porous ZIF material obtained above was ball-milled to prepare particles with a size of about 1 μm, thus obtaining the first porous precursor material.

[0105] 2) Preparation of coating material particles

[0106] First, the deoxygenating material catechol is dissolved in ethanol solvent at a concentration of 8 g / L. Then, the first porous precursor material obtained above is uniformly dispersed in the ethanol solution containing catechol and stirred under vacuum for 6 hours. After centrifugation, filtration and air drying, the second porous precursor material particles with deoxygenating material adsorbed on the surface are obtained. The thickness of the deoxygenation layer here is 100 nm.

[0107] The liquid-retaining material is ball-milled into particles with a size of 50-200 nm, and then uniformly dispersed in a dichloroethane solution to prepare a gel-like solution with a viscosity in the range of 1000-2000 ppm, thus obtaining a polymer gel-like solution.

[0108] Subsequently, the obtained second porous precursor material particles were ball-milled and transferred to a fluidized bed. The polymer gel solution was then uniformly coated onto the second porous precursor material particles by spray drying. The temperature was controlled at 60°C, and the polymer was dried and shaped to obtain the target product, which is the coated material particles. The thickness of the liquid retention layer here is about 400 nm.

[0109] 3) Preparation of cathode materials

[0110] The coating material particles prepared above are uniformly mixed with conductive agent and binder in a ratio of 90:7:3 to obtain coating layer material. The conductive agent is carbon nanotubes. The coating layer material is uniformly coated on the surface of the positive electrode active material by spray drying. The thickness of the coating layer is 1.5 μm, thus obtaining a positive electrode material with a core-shell structure.

[0111] 4) Preparation of the active layer of the positive electrode sheet

[0112] The conductive agent used is SP (super pll conductive carbon black) and carbon nanotubes, the binder is PVDF5130, and the positive electrode current collector is 10μm aluminum foil. The above-prepared positive electrode material is mixed with the conductive agent and binder in a ratio of 97:2:1, and then NMP (N-methylpyrrolidone) is added and stirred to form a uniform and stable positive electrode slurry. The positive electrode slurry is then uniformly coated onto the positive electrode current collector, with a coating surface density of 156 g / m². 2 After drying and cold pressing, a positive electrode sheet is obtained, with a compaction density of 3.4 g / cm³. 3 .

[0113] 5) Preparation of negative electrode sheet

[0114] The negative electrode active material is graphite, the conductive agent is SP, the binder is CMC and SBR, and the negative electrode current collector is 6μm copper foil. The negative electrode active material, conductive agent, CMC, and SBR are mixed in a ratio of 96.5:1:1:1.5, then deionized water is added and stirred to form a uniform and stable negative electrode slurry. The negative electrode slurry is then uniformly coated onto the negative electrode current collector, with a coating surface density of 156 g / m². 2 After drying and cold pressing, the negative electrode sheet is obtained, with a compaction density of 1.5 g / cm³. 3 .

[0115] 6) Battery manufacturing

[0116] Selection of the separator membrane: Polypropylene membrane with a thickness of 12μm is selected as the base membrane for the separator membrane.

[0117] Cell assembly: The positive electrode sheet, separator, negative electrode sheet, and separator prepared above are arranged in sequence and assembled by winding to obtain the cell.

[0118] Preparation of electrolyte: LiPF6 was dissolved in a solvent of ethylene carbonate, methyl ethyl carbonate and diethyl carbonate in a volume ratio of 1:1:1, with a concentration of 1.2 mol / L.

[0119] Electrolyte is injected into the dry battery cell and soaked for 24 hours. Then, it is formed at 45°C. The formation process is as follows: charge to 3.4V at 0.05C and then charge to 3.75V at 0.2C. The battery cell is manufactured after aging at room temperature for 24 hours.

[0120] Example 2

[0121] The difference between this embodiment and Embodiment 1 is that in this embodiment, the temperature of the polymer gel solution prepared by uniformly dispersing the liquid-retaining material particles in dichloroethane solvent is increased to 80°C when it is uniformly coated onto the second porous precursor material particles by spray drying.

[0122] Example 3

[0123] The difference between this embodiment and Embodiment 1 is that the thickness of the coating layer in this embodiment is 3μm.

[0124] Example 4

[0125] The difference between this embodiment and Embodiment 1 is that in this embodiment, the thickness of the deoxidized layer is changed by extending the immersion time of the first porous precursor material in the deoxidized material solution, and the thickness is 150nm.

[0126] Example 5

[0127] The difference between this embodiment and Embodiment 1 is that the thickness of the liquid-retaining material layer is changed by extending the spray drying time in this embodiment, and the thickness is 800nm.

[0128] Example 6

[0129] The difference between this embodiment and Embodiment 1 is that in this embodiment, the particle size of the first porous precursor material is increased, which is equivalent to the increase of the ZIF ratio, and the ZIF particle size is increased to 1.5 μm.

[0130] Comparative Example 1

[0131] The difference between Comparative Example 1 and Example 1 is that the thickness of the coating layer is 5 μm.

[0132] Comparative Example 2

[0133] The difference between Comparative Example 2 and Example 1 is that there is no deoxidizing material layer in the coating layer.

[0134] Comparative Example 3

[0135] The difference between Comparative Example 3 and Example 1 is that there is no liquid-retaining material layer in the coating layer.

[0136] Comparative Example 4

[0137] The difference between Comparative Example 4 and Example 1 is that the coating layer does not have a deoxidizing material layer or a liquid-retaining material layer, and the liquid-retaining agent and deoxidizing agent are uniformly dispersed in the coating layer in the same mass.

[0138] Comparative Example 5

[0139] The difference between Comparative Example 5 and Example 1 is that the conductive carbon nanotubes are removed from the coating layer on the surface of the positive electrode material, and instead the conductive carbon nanotubes are dispersed into the positive electrode slurry in the same mass.

[0140] Test methods and conditions

[0141] 1. Loop testing

[0142] Cyclic performance test (tested on the Newway system):

[0143] Charging: Charge at 1C constant current and constant voltage to 4.25V, cut-off current is 0.05C, and let stand for 5 minutes; Discharging: Discharge at 1C constant current to 2.8V, and let stand for 5 minutes. One charge-discharge process is considered to complete one cycle.

[0144] Discharge capacity after the first cycle of 1C operation: 1C constant current and constant voltage charging to 4.25V, cutoff current is 0.05C, 1C constant current discharge to 2.8V. The discharge capacity measured in this step is the discharge capacity of the first cycle of 1C operation (denoted as C1).

[0145] Discharge capacity after the nth cycle of 1C operation: The device is charged to 4.25V using a constant current and constant voltage method with a cutoff current of 0.05C, and then discharged to 2.8V using a constant current method. The discharge capacity measured in this step is the cyclic discharge capacity after the nth cycle of 1C operation (denoted as C). n ).

[0146] Repeat the above test steps repeatedly. The capacity retention rate in the Nth cycle equals the discharge capacity in the Nth cycle, C. n / First cycle discharge capacity C1.

[0147] 2. Hot Box Safety Test

[0148] The thermal chamber test conditions were as follows: the battery was heated to 130°C at room temperature at a rate of 5°C / min, held at that temperature for 30 minutes, then the temperature was stopped and the battery was continuously observed for 1 hour. The ambient temperature was then raised again to 130°C at a rate of 5°C / min and held for 30 minutes. This process was repeated with increments of 5°C, held for 30 minutes each time, until the battery failed. The failure temperature of each battery was recorded. Higher temperatures indicate higher thermal stability and better safety performance of the cell.

[0149] 3. Diaphragm resistance test

[0150] The prepared positive electrode sheet is rolled to the same thickness, and the film resistance of the electrode sheet is tested using a four-probe resistance tester.

[0151] 4. Energy density at 1C

[0152] Charging: Charge at 1C constant current and constant voltage to 4.25V, cut-off current is 0.05C, and let stand for 5 minutes; Discharging: Discharge at 1C constant current to 2.8V, and let stand for 5 minutes.

[0153] Record the battery's 1C discharge capacity C0, discharge voltage V, and weigh the battery m. Then, energy density = capacity * voltage / weight.

[0154] 5. Liquid retention test

[0155] The same weight of positive electrode sheets were immersed in the electrolyte for 4 hours, and then removed and weighed.

[0156] The test results of the batteries and positive electrode sheets prepared in Examples 1-3 and Comparative Examples 1-5 are shown in Table 1.

[0157] Table 1

[0158]

[0159] The test results in Table 1 show that:

[0160] 1) Compared with Comparative Examples 1-5, the batteries prepared in Examples 1-6 have excellent cycle performance.

[0161] 2) Compared with Comparative Examples 1-5, the batteries prepared in Examples 1-6 have excellent density.

[0162] 3) Compared with Comparative Examples 1-5, the batteries prepared in Examples 1-6 can achieve excellent liquid retention coefficients while ensuring excellent energy density and cycle performance. In particular, as shown in Examples 1, 3, and Comparative Example 1, the liquid retention coefficient of the battery can be improved by increasing the thickness of the coating layer. However, excessively thick functional layers can also lead to an increase in ionic impedance and a decrease in energy density. Therefore, overall, there are disadvantages.

[0163] 4) Compared with Comparative Examples 1-5, the batteries prepared in Examples 1-6 have higher thermal box failure temperatures and better safety performance. Comparing Examples 1-6 with Comparative Example 2, the absence of a deoxygenation layer in the coating structure resulted in a significant decrease in the thermal box failure temperature. This is presumably due to the inability to continuously adsorb oxygen released from the positive electrode, leading to a decrease in the thermal box temperature. Comparing Examples 1-6 with Comparative Example 3, the absence of a polymer liquid-retaining material layer in the coating structure resulted in a significant deterioration in the membrane resistance. This is presumably due to the lack of a tough polymer layer, which reduces the contact between the functional coating layers, thus increasing the membrane resistance and deteriorating the electrochemical performance. Comparing Examples 1-6 with Comparative Example 4, although all component ratios were the same as in Example 1, the membrane resistance also increased significantly. This is presumably due to the unevenness of the toughness region on the surface of the functional layer, leading to poor contact between the active materials, which also deteriorated the battery performance. Comparing Comparative Example 5 with Examples 1-6, the removal of the conductive carbon nanotubes from the coating layer resulted in a significant increase in membrane resistance, even though the slurry contained the same proportion of carbon nanotubes. This is presumably because when nanotubes are in the functional coating layer, they can connect the inner and outer layers of adjacent active materials, reducing battery polarization. Data from Examples 4-6 show that adjusting the thickness or mass of each functional layer in the functional agent within a certain range helps to improve the overall performance of the entire battery.

[0164] In summary, Examples 1-6 are superior to existing solutions, and the coating layer design they employ enables the battery to possess excellent overall electrochemical performance.

[0165] It should be noted that, in this document, the term "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one" does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element. Furthermore, it should be noted that the scope of the methods and apparatuses in the embodiments of this application is not limited to performing functions in the order shown or discussed, but may also include performing functions substantially simultaneously or in the reverse order, depending on the functions involved. For example, the described methods may be performed in a different order than described, and various steps may be added, omitted, or combined. Additionally, features described with reference to certain examples may be combined in other examples.

[0166] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications or equivalent substitutions made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A positive electrode material, characterized in that, The material includes a positive electrode active material (1) and a coating layer (2), wherein the coating layer covers the outer surface of the positive electrode active material; The coating layer (2) includes coating material particles, which have a core-shell structure. The core of the core-shell structure is an adsorbent material (21), and the outer shell is a deoxygenating material (22). The adsorbent material (21) includes porous adsorbent material. The thickness of the coating layer (2) is 0.5-3 μm; the coating material particles also include a liquid-retaining material layer (23), which is coated on the outer surface of the deoxidizing material (22); The deoxidizing material (22) includes one or more of the following: catechol, pyrogallol, p-methoxyphenol, cresol, tert-butylcatechol, p-phenylenediamine, polyethyleneimine, acetyldopamine, ethylenediamine, and diphenylamine. The porous adsorbent material includes one or more of porous carbon materials, porous MOFs, and porous ZIFs; The liquid-retaining material includes one or more of polyacrylate, diethyl polyacrylic acid, and polymethyl methacrylate.

2. The cathode material according to claim 1, characterized in that, The mass ratio of the adsorbent material (21), the deoxygenating material (22), and the liquid-retaining material layer (23) is (80-90):(5-10):(5-10); And / or, The thickness of the liquid-retaining material layer (23) is 200nm-1000nm.

3. The cathode material according to claim 1, characterized in that, The thickness of the outer shell layer formed by the deoxidizing material (22) is 50nm-200nm.

4. The cathode material according to claim 1, characterized in that, The coating layer (2) further includes a conductive agent and a binder, and the mass ratio of the coating material particles to the conductive agent and the binder is (90-95):(5-10):(2-5).

5. The positive electrode material according to claim 4, characterized in that, The conductive agent includes one or more of graphene, conductive graphite, and carbon nanotubes, or a mixture thereof.

6. The cathode material according to claim 4, characterized in that, The adhesive comprises one or more of PVDF, PTFE, CMC, and PAA, or a mixture thereof.

7. The cathode material according to claim 1, characterized in that, The positive electrode active material (1) includes one or more of the following: lithium nickel cobalt manganese oxide ternary material, lithium manganese oxide, and lithium cobalt oxide.

8. The cathode material according to claim 7, characterized in that, The positive electrode active material (1) includes a high-nickel ternary material.

9. A method for manufacturing a positive electrode material, characterized in that, The method for manufacturing the cathode material as described in any one of claims 1-8 includes: Cobalt salt and 2 The first porous precursor material particles were prepared by the synthesis of methylimidazole. The process involves preparing coated material particles by combining the first porous precursor material particles with a deoxidizing material and a liquid-retaining material. The deoxidizing material forms a shell, the first porous precursor material forms a core, and the outer surface of the deoxidizing material is coated with the corresponding liquid-retaining material. This process includes: After uniformly dispersing the first porous precursor material particles into a solution containing deoxygenating material, centrifuging, filtering, and air-drying are performed to obtain the second porous precursor material particles with deoxygenating material adsorbed on the surface. The liquid-retaining material was ball-milled and then uniformly dispersed in a solvent to prepare a polymer colloidal solution. The polymer gel solution is uniformly coated onto the surface of the second porous precursor material particles by spray drying, and then heated and dried to obtain coated material particles. The coating material particles are mixed with a conductive agent and a binder to obtain a coating layer material; A positive electrode material is prepared by coating the surface of the positive electrode active material with the coating layer material.

10. The method for manufacturing the cathode material according to claim 9, characterized in that, The cobalt salt and 2 The mass ratio of methylimidazole is 1:(3-6); And / or, The mass ratio of the coating material particles to the conductive agent and the binder is (90-95):(5-10):(2-5).

11. The method for manufacturing the cathode material according to claim 9, characterized in that, The cobalt salt and 2 The synthesis of methylimidazole to prepare the first porous precursor material particles includes: Cobalt salt and 2 A three-dimensional porous precursor material was synthesized by uniformly mixing methylimidazole in a solvent to prepare a mixed solution and then heating the reaction. The three-dimensional porous precursor material was ball-milled to prepare the first porous precursor material particles.

12. The method for manufacturing the cathode material according to claim 11, characterized in that, The solvent includes at least one of water, DMF, ethylene glycol, and methanol; And / or, The concentration of the mixed solution is 10-100 g / L; And / or, The temperature of the heating reaction is 100-200℃, and the reaction time is 1-6h; And / or, The solvent in the solution containing the deoxygenating material is at least one of water, ethanol and methanol, and the concentration of the solution containing the deoxygenating material is 5-10 g / L. And / or, The spray drying temperature is 60-100℃.

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