Porous positive electrode material and preparation method and application thereof

Abstract

The invention discloses a porous positive electrode material as well as a preparation method and application thereof, and relates to the technical field of positive electrode materials. Repeating the coating treatment, the de-oxidant treatment and the first sintering treatment for n times to prepare the porous positive electrode material, and the de-oxidant treatment comprises the following steps: reducing the temperature of the coated system to-50 DEG C to-20 DEG C, treating for 0.6-1.5 hours, and then raising the temperature of the system to 5-200 DEG C and treating for 0.1-1.5 hours under the triphase point pressure of water. The de-oxidant treatment is a cold drying process, the solution is solidified through rapid cooling, then the solidified solution is vaporized and discharged through rapid heating, and the solute is completely reserved on the surface of the primary crystal grain; the coating rate of the porous positive electrode material is high, and the primary crystal grains with the coating layer on the surface are more. The preparation method is simple and convenient, and the multi-layer coated porous positive electrode material can be prepared after repeating for n times. The side reaction between the prepared lithium ion battery and electrolyte in the cycle process is weakened, and the cycle performance is remarkably improved.

Description

Technical Field

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

[0002] With the continuous development of lithium-ion battery technology, the performance requirements for cathode materials are becoming increasingly stringent, especially in terms of cycle stability, rate performance, and thermal safety. To improve the interfacial stability and electrochemical performance of cathode materials, surface coating technology is widely used in material modification. Among these methods, grain-level shell coating is an effective approach. By constructing a uniform coating layer on the surface of primary grains, side reactions between the electrolyte and the material can be suppressed, the dissolution of transition metal ions can be reduced, and the structural stability of the material under high voltage can be improved.

[0003] In existing technologies, common coating methods mainly include water-wash coating and one-time sintering coating. In the water-wash coating process, the synthesized cathode material is typically mixed with a compound solution containing the coating element and a dispersant. After stirring and dispersing, the solvent is removed by drying, and then high-temperature sintering is performed to form a target compound shell on the material surface. This method is based on post-processing coating of pre-synthesized materials, the operation is relatively independent, and it is applicable to various material systems.

[0004] One-time sintering coating involves co-mixing the precursor material, lithium source, and a compound solution of the coating element, simultaneously completing crystal growth and coating layer formation during a single sintering process. This method achieves in-situ coating through co-sintering, which is beneficial for the interfacial bonding between the coating layer and the substrate material.

[0005] However, both methods have limitations in practical applications. During the water-washing coating process, due to the inherent agglomeration characteristics or microporous structure of the cathode material, the coating solution cannot fully penetrate to the surface of the primary grains inside the material. This results in some inner grains failing to effectively form a coating layer, affecting the uniformity and integrity of the overall coating. While single-sintering coating can achieve better interfacial contact, the entire coating process is completed in a single sintering, lacking a process window for subsequently introducing different coating components. Therefore, it cannot achieve multi-layer, gradient, or multi-component composite coating structures, limiting its application in complex coating designs.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a porous cathode material, its preparation method, and its application, so as to improve or solve the above-mentioned technical problems.

[0008] This invention is implemented as follows: In a first aspect, the present invention provides a method for preparing a porous cathode material, comprising the following steps: After repeating the coating process, desizing process, and first sintering process n times, a porous cathode material is prepared. In the (n+1)th repeated operation, the product after the first sintering treatment in the nth time is used as the raw material for the (n+1)th coating treatment; 1≤n≤3; The descaling process includes: lowering the temperature of the coated system to -50°C to -20°C for 0.6h to 1.5h, and then raising the temperature of the system to 5°C to 200°C for 0.1h to 1.5h under the triple point pressure of water.

[0009] Secondly, the present invention provides a porous cathode material prepared by the preparation method of any of the foregoing embodiments, wherein the chemical formula of the porous cathode material is Li. s Ni x Co y Mn z M w N p O2, wherein M is at least one of Al, W, and Ti, and N is at least one of Zr, Mg, Y, Sr, Sb, Ca, Nb, Mo, and B; 0.9 ≤ s ≤ 1.1, x ≥ 0.9, 0 <y+z≤0.1,0.0001≤p≤0.01,w=0.005-0.05。

[0010] Thirdly, the present invention provides a lithium-ion battery comprising a porous cathode material prepared by any of the preparation methods described in the foregoing embodiments or a porous cathode material as described in the foregoing embodiments.

[0011] The present invention has the following beneficial effects: In the method for preparing porous cathode materials provided in this invention, the desizing process employs a cold-drying technique. First, the solution is rapidly cooled to solidify, then rapidly heated to vaporize, quickly removing the solvent from the system. This ensures the solute is well retained on the surface of the primary grains of the porous cathode material, resulting in a high coating rate and a large number of primary grains with a coating layer on the surface. The preparation method provided by this invention is simple; by repeating the coating process, desizing process, and first sintering process n times, a multi-layered porous cathode material can be prepared.

[0012] The side reactions between the lithium-ion battery and the electrolyte are weakened during cycling, resulting in significantly improved cycle performance. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention 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 or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0014] In a first aspect, the present invention provides a method for preparing a porous cathode material as described in the foregoing embodiments, comprising the following steps: After repeating the coating process, desizing process, and first sintering process n times, a porous cathode material is prepared. In the (n+1)th repeated operation, the product after the first sintering treatment in the nth time is used as the raw material for the (n+1)th coating treatment; 1≤n≤3; The descaling process includes: lowering the temperature of the coated system to -50°C to -20°C for 0.6h to 1.5h, and then raising the temperature of the system to 5°C to 200°C for 0.1h to 1.5h under the triple point pressure of water.

[0015] It should be noted that the coating process is carried out in a closed, constant-temperature system, and the additives are added in solution form.

[0016] The desolventizing process of this invention employs a cold-drying process, which first rapidly cools down the solution to solidify it, and then rapidly heats it up to vaporize the solidified solution, quickly removing the solvent from the system. This ensures that the solute is well retained on the surface of the primary grains of the porous cathode material, resulting in a porous cathode material with a high coating rate and a large number of primary grains with a coating layer on the surface.

[0017] For example, if repeated twice, the steps include a first coating treatment, a desizing treatment, and a first sintering treatment. After this round of steps is completed, the product of the first sintering treatment is used as raw material for a second repetition, that is, the coating treatment, desizing treatment, and first sintering treatment are performed again.

[0018] In an optional embodiment, the coating process includes: mixing the positive electrode material and water in a certain proportion, adding an additive, and then coating the material at a temperature of 30℃-50℃ for 1 min-30 min; wherein the solid-liquid ratio of the positive electrode material and water is 1:(0.5-2), and the concentration of the additive is 0.5mol / L-3mol / L.

[0019] Additives function through two main mechanisms: bulk doping and surface coating. Specifically, cations in the additives (such as aluminum ions) enter the lattice of the cathode material during high-temperature sintering, partially replacing transition metal sites. This can suppress harmful phase transitions and lattice oxygen evolution during charging and discharging, improving structural stability and safety. Additive ions can also occupy vacancies of nickel ions migrating from the lithium layer, forming energy barriers, reducing nickel-lithium mixing, ensuring unobstructed lithium ion channels, and improving capacity and rate performance. In addition, a stable lattice structure can reduce side reactions between the material and the electrolyte, reduce the dissolution of transition metal ions (such as manganese ions), and extend cycle life.

[0020] If the amount of additive is too small, the coating layer will be discontinuous and defective, failing to effectively isolate the electrolyte; if the doping concentration is too low, it will be insufficient to stabilize the entire crystal lattice; the improvement effect will be negligible, and the material performance will still be dominated by its intrinsic defects. If the amount of additive is too large, excessive doping may lead to crystal lattice distortion, or introduce too many inert ions, which will hinder the diffusion of lithium ions, resulting in a significant decrease in capacity and rate performance.

[0021] For example, the solid-liquid ratio of the cathode material and water can be selected from any one of 1:0.5, 1:1, 1:1.5 and 1:2, or other values ​​in the range of 1:(0.5-2), depending on actual needs; the concentration of the additive can be selected from any one of 0.5mol / L, 1mol / L, 1.5mol / L, 2mol / L, 2.5mol / L and 3mol / L, or other values ​​in the range of 0.5mol / L-3mol / L, depending on actual needs.

[0022] Preferably, during the coating process, the additive is added at a rate of 50 mL / min to 70 mL / min.

[0023] In an optional embodiment, the additive is selected from at least one of aluminum source, tungsten source and titanium source; The aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum phosphate, and aluminum chloride. The tungsten source is selected from at least one of ammonium tungstate, ammonium metatungstate, ammonium paratungstate (AMT), phosphotungstic acid, and sodium tungstate; Titanium sources include titanium dihydrogen phosphate.

[0024] In an optional embodiment, the desiccant treatment involves a cooling process at a rate of 0.5°C / min to 2.0°C / min and a heating process at a rate of 1.5°C / min to 3.5°C / min.

[0025] In one embodiment of the present invention, the desiccant treatment is carried out in a closed container, and the rate is controlled by placing the closed container in a constant temperature chamber and adjusting the parameters of the constant temperature chamber; in other embodiments of the present invention, reasonable adjustments can be made according to actual needs.

[0026] In an optional embodiment, the desiccant treatment is carried out in a vacuum environment under pressure ≤600Pa.

[0027] And / or, the desiccant treatment time is 2 min-8 min.

[0028] It should be noted that the solvent removal process primarily involves removing the solvent from the coated system. Under vacuum conditions, the ambient pressure is significantly reduced, and the boiling point of the liquid also drops substantially. This means that solvent removal can be achieved at lower temperatures, which helps to preserve the original microstructure of the material to the greatest extent possible. Furthermore, it ensures thorough removal of deep solvent layers, reduces residual impurities, and prevents the re-agglomeration of solute particles.

[0029] If solvent removal is performed directly at high temperatures, the excessively high temperature will damage the fine structure of the cathode material precursor (such as hydroxides or carbonates), potentially leading to particle agglomeration, changes in crystallinity, or crack formation. Vacuum low-temperature solvent removal can preserve the original microstructure of the material to the greatest extent possible.

[0030] In an optional implementation, the preparation of the cathode material includes: The lithium source, nickel source, cobalt source and manganese source are mixed in a molar ratio of (0.9-1.1):x:y:z and then subjected to a second sintering treatment to obtain the cathode material, wherein x≥0.9, 0<y+z≤0.1, and x+y+z=1; The second sintering process includes: raising the system temperature to 550℃-650℃ at a rate of 1.5℃ / min-3.5℃ / min and holding it at that temperature for 3.5h-6h, then raising the temperature to 700℃-820℃ at a rate of 1.5℃ / min-3.5℃ / min and sintering for 8.5h-9.5h; and cooling the system to room temperature at a rate of 1.5℃ / min-3.5℃ / min after the second sintering process is completed.

[0031] It should be noted that the lithium, nickel, cobalt, and manganese sources can be compounds containing lithium, nickel, cobalt, and manganese elements respectively, or they can be cathode material precursors and lithium-containing compounds containing at least two of the elements nickel, cobalt, and manganese. The types of materials can be selected appropriately according to actual needs. For example, lithium salts can be selected from lithium carbonate, lithium hydroxide, etc.; nickel sources can be selected from nickel sulfate, nickel nitrate, nickel chloride, etc.; cobalt sources can be selected from cobalt sulfate, cobalt chloride, etc.; manganese sources can be selected from manganese sulfate, manganese chloride, etc.; and cathode material precursors can be selected from nickel cobalt manganese hydroxide, nickel cobalt aluminum hydroxide, etc.

[0032] The slow heating at low temperatures during sintering is to thoroughly and smoothly remove volatile components (such as adsorbed water, water of crystallization, and residual solvents) from the precursor. Slow heating allows sufficient time for the thermal decomposition reaction to proceed fully from the surface inwards, preventing incomplete decomposition from introducing impurities or amorphous phases into subsequent high-temperature stages, which could affect the purity of the final product. If the temperature rises too quickly, these volatile components will rapidly vaporize inside the material, generating enormous pressure that can cause particle breakage, pulverization, or excessive porosity, thus destroying the intended spherical or dense morphology.

[0033] The slow heating during the high-temperature stage of sintering provides sufficient motive force and time for atomic diffusion. This is beneficial for obtaining structures with good crystallinity, complete crystal form, and low cation mixing degree; the enhanced mass transport at high temperature stage allows particles to bind more tightly through mass migration, achieving a certain degree of densification.

[0034] During sintering, the holding time directly affects the grain size: too long a time will cause the grains to grow excessively, reducing the specific surface area and potentially affecting the rate performance; too short a time will result in incomplete reaction.

[0035] Controlling the cooling rate is to avoid excessive temperature difference between the inside and outside of the material due to rapid cooling, which can generate thermal stress and cause microcracks in the particles.

[0036] In an optional embodiment, the preparation of the cathode material may further include the addition of a pore-forming agent, one or more oxides or salts; The pore-forming agent is selected from at least one of potassium sulfate and sodium sulfate; The oxide is a metal oxide, and the metal element is selected from at least one of Zr, Mg, Y, Sr, Sb, Ca, Nb, and Mo; the molar ratio of the metal elements ranges from 0.0001 to 0.01. Salts are selected from at least one of carbonates, sulfates, and nitrates.

[0037] For example, zirconium ions in zirconium oxide partially replace nickel or cobalt ions in the cathode material, stabilizing the crystal structure, inhibiting harmful phase transitions, reducing cation mixing, and improving battery cycle life. Some undoped zirconium oxide particles, or those in nanoparticle form, adhere to the surface of the cathode material particles, forming an extremely thin protective layer that physically isolates the highly active cathode material from the corrosive electrolyte, reducing transition metal dissolution and electrolyte decomposition, and lowering interfacial impedance.

[0038] After sintering, the cathode material reacts with H2O and CO2 in the air during cooling and storage, generating a large amount of residues such as lithium hydroxide and lithium carbonate. These residues can worsen the subsequent processability of the cathode material, making the resulting battery prone to gas swelling and posing a safety hazard. They can also increase interfacial impedance, affecting rate performance and capacity. The addition of potassium sulfate reacts with lithium hydroxide and lithium carbonate to generate lithium sulfate, which has lower solubility, thus facilitating the effective removal of residual lithium and causing less damage to the cathode material's structure. Introducing pure water, on the other hand, will cause a large amount of lithium to dissolve from the material, damaging its structure.

[0039] In an optional embodiment, the first sintering treatment includes: raising the system temperature to 300℃-500℃ at a rate of 1.5℃ / min-3.5℃ / min and holding it at that temperature for 3.5h-8h, and then cooling it to room temperature at a rate of 1.5℃ / min-3.5℃ / min after the second sintering treatment is completed.

[0040] Secondly, this invention provides a porous cathode material, the chemical formula of which is Li. s Ni x Co y Mn z M w N p O2, wherein M is at least one of Al, W, and Ti, and N is at least one of Zr, Mg, Y, Sr, Sb, Ca, Nb, Mo, and B; 0.9 ≤ s ≤ 1.1, x ≥ 0.9, 0 <y+z≤0.1,0.0001≤p≤0.01,w=0.005-0.05。

[0041] Where M represents the element type corresponding to the additive, the addition of the additive is beneficial to improve the discharge capacity of the battery and improve the capacity retention rate.

[0042] Thirdly, the present invention provides a lithium-ion battery comprising a porous cathode material prepared by any of the preparation methods described in the foregoing embodiments or a porous cathode material as described in the foregoing embodiments.

[0043] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0044] Example 1 This embodiment provides a porous cathode material, the preparation of which includes the following steps: (1) Preparation of cathode materials 3kg of cathode material precursor Ni was added in proportion. 0.96 Co 0.02 Mn 0.02 (OH)₂, 1.4 kg lithium hydroxide, 9.27 g ZrO₂, and 60 g potassium sulfate were mixed evenly and then placed in a sintering furnace for a second sintering treatment. The sintering curve was as follows: the temperature was increased to 600℃ at a rate of 3℃ / min and held for 5 h, then increased to 760℃ at a rate of 2℃ / min and sintered for 9 h, and finally cooled to room temperature at a rate of 2℃ / min to obtain the product with the chemical formula Li. 1.0 (Ni 0.96 Co 0.02 Mn 0.02 O2 cathode material.

[0045] (2) Preparation of porous cathode materials (a) Coating treatment Prepare an AlCl3 additive solution with a concentration of 0.5 mol / L.

[0046] Place the sealed container in a constant temperature chamber, mix 3 kg of the positive electrode material obtained in step (1) and water in the sealed container at a mass ratio of 1:0.5, and then add 600 mL of additive solution at a rate of 60 mL / min. Stir for a total of 15 min from the start of adding the additive solution to the end of the addition.

[0047] (b) De-drying treatment The temperature chamber was cooled to -20℃ at a rate of 1.0℃ / min and held for 1 hour. Then, the sealed container was evacuated to a pressure of 600Pa. Subsequently, the temperature chamber was heated to 110℃ at a rate of 3.0℃ / min and held for 15 minutes.

[0048] (c) First sintering treatment The material after the descaling treatment in step (b) was then transferred to a sintering furnace for the first sintering treatment. The sintering curve was as follows: the temperature was increased to 400℃ at a rate of 2.0℃ / min, held for 5 hours, and then cooled to room temperature at a rate of 2.0℃ / min to obtain a porous cathode material with the chemical formula Li. 1.00 Ni 0.955 Co 0.020 Mn 0.020 Al 0.005 O2.

[0049] Example 2 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Example 1, the only difference being: (2) Preparation of porous cathode materials (a) Coating treatment Prepare an AlCl3 additive solution with a concentration of 1.0 mol / L.

[0050] The chemical formula of the porous cathode material is Li 1.00 Ni 0.95 Co 0.02 Mn 0.02 Al 0.01 O2.

[0051] Example 3 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Example 1, the only difference being: (2) Preparation of porous cathode materials (a) Coating treatment Prepare an AlCl3 additive solution with a concentration of 2.0 mol / L.

[0052] The chemical formula of the porous cathode material is Li 1.00 Ni 0.94 Co 0.02 Mn 0.02 Al 0.02 O2.

[0053] Example 4 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Example 1, the only difference being: (2) Preparation of porous cathode materials (a) Coating treatment Prepare an AMT (ammonium paratungstate) additive solution with a concentration of 1.0 mol / L.

[0054] The chemical formula of the porous cathode material is Li 1.00 Ni 0.95 Co 0.02 Mn 0.02 W 0.01 O2.

[0055] Example 5 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Example 1, the only difference being: (a) Coating treatment Prepare a mixed additive solution of AlCl3 and AMT with a concentration of 1.0 mol / L and a volume ratio of 1:1.

[0056] The chemical formula of the porous cathode material is Li 1.000 Ni 0.950 Co 0.020 Mn0.020 Al 0.005 W 0.005 O2.

[0057] Example 6 This embodiment provides a porous cathode material, which is obtained by repeating two coating processes, a desizing process, and a sintering process. The process includes the following steps: The implementation steps of the first round of coating treatment, desizing treatment, and first sintering treatment are the same as in Example 1; the implementation steps of the second round of coating treatment, desizing treatment, and first sintering treatment are the same as in the first round, with the only difference being as follows: (a2) Coating treatment Prepare an AMT additive solution with a concentration of 0.5 mol / L.

[0058] 3 kg of porous cathode material (chemical formula Li) that has undergone a first sintering process was placed in a sealed container. 1.00 Ni 0.955 Co 0.02 0Mn 0.020 Al 0.005 O2 and water are mixed and treated at a mass ratio of 1:0.5.

[0059] (b2) During the desiccant treatment, the temperature was raised to 110°C and held for 15 minutes.

[0060] (c2) First sintering treatment The chemical formula of the porous cathode material is Li 1.000 Ni 0.950 Co 0.020 Mn 0.020 Al 0.005 W 0.005 O2.

[0061] Example 7 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Embodiment 2, the only difference being: (2) Preparation of porous cathode materials (b) During the desolventizing process, the temperature is raised to 110°C and held for 6 minutes. The solvent in a solidified state is directly vaporized and discharged within 2 minutes.

[0062] Example 8 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Embodiment 2, the only difference being: (2) Preparation of porous cathode materials (b) During the desiccant treatment, the temperature was raised to 110°C and held for 30 minutes.

[0063] Example 9 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Embodiment 2, the only difference being: (2) Preparation of porous cathode materials (b) During the desiccant treatment, the temperature was raised to 110°C and held for 1 hour.

[0064] Example 10 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Embodiment 2, the only difference being: (2) Preparation of porous cathode materials (b) During the desiccant treatment, the temperature of the constant temperature chamber is increased to 110°C at a rate of 1.0°C / min.

[0065] Example 11 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Embodiment 2, the only difference being: (2) Preparation of porous cathode materials (b) During the desiccant treatment, the temperature of the constant temperature chamber is increased to 110°C at a rate of 2.0°C / min.

[0066] Example 12 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Embodiment 2, the only difference being: (2) Preparation of porous cathode materials (b) During the desiccant treatment, the temperature of the constant temperature chamber is increased to 60°C at a rate of 3.0°C / min.

[0067] Example 13 This embodiment provides a porous cathode material, the preparation steps of which are the same as those in Embodiment 2, the only difference being: (2) Preparation of porous cathode materials (b) During the desiccant treatment, the temperature of the constant temperature chamber is increased to 180°C at a rate of 3.0°C / min.

[0068] Comparative Example 1 This comparative example provides a porous cathode material, the preparation steps of which are the same as those in Example 1, the only difference being: (2) No desizing treatment (b) was performed in the preparation of porous cathode materials.

[0069] Comparative Example 2 This comparative example provides a porous cathode material, the preparation steps of which are the same as those in Example 1, the only difference being: (2) No additive solution was added in (a) coating treatment during the preparation of porous cathode materials.

[0070] The chemical formula of the porous cathode material is Li 1.00 Ni 0.96 Co0.02 Mn 0.02 O2.

[0071] Comparative Example 3 This comparative example provides a porous cathode material, the preparation steps of which are the same as those in Example 1, the only difference being: (2) Preparation of porous cathode materials (b) De-drying treatment The sealed container was not evacuated, and the pressure inside the sealed container was 101325 Pa.

[0072] Test Example 1 This test example performs performance tests on the porous cathode materials prepared in Examples 1-13 and Comparative Examples 1-3. The test methods are as follows: Each sample was mixed with superconducting carbon black (SP) and polyvinylidene fluoride (PVDF) at a mass ratio of 94:3:3. The mixture was then prepared into a slurry using N-methylpyrrolidone (NMP). The slurry was uniformly coated onto an aluminum foil current collector to obtain the positive electrode film. Using a lithium metal sheet as the negative electrode, a polypropylene microporous membrane as the separator, and 1 mol / L LiPF6 (a 1:1 volume ratio mixture of ethylene carbonate and dimethyl carbonate) as the electrolyte, coin cells were assembled in an Ar-protected glove box. The electrical performance of the coin cells was tested under the following conditions: First charge-discharge test: charged to 4.3V at 0.1C, allowed to stand for 5 minutes, and discharged to 3.0V at 0.1C; 100-cycle test at 45℃: charged to 4.3V at 0.5C at 45℃, allowed to stand for 5 minutes, and discharged to 3.0V at 0.5C for 100 cycles. The test results are shown in Table 1.

[0073] Table 1 Performance Test Results

[0074] As can be seen from the data in Table 1: (1) Comparative Examples 1, 2 and Example 1 show that under the condition of desizing treatment, while keeping other process conditions unchanged, the cycle performance of porous cathode materials is significantly improved.

[0075] (2) Comparative Examples 1, 3 and Example 1 show that when the same process conditions are maintained and only the pressure of the desolventizing process is changed, when the desolventizing process is heated at atmospheric pressure, the solvent cannot be directly sublimated from solid to gaseous state, and the cycle performance of the porous cathode material is not significantly improved.

[0076] (3) Examples 1, 2 and 3 show that by keeping the same process conditions and only changing the concentration of additives, the cycle performance of porous cathode materials is significantly improved.

[0077] (4) Comparative Example 1 and Examples 1, 2 and 4 show that by keeping the same process conditions and only changing the type of additives, the cycle performance of the porous cathode material is significantly improved.

[0078] (5) Examples 2, 4 and 5 show that keeping the same process conditions and only changing the additive solution to a mixed additive solution of AlCl3 and AMT, the improvement of the cycle performance of porous cathode materials is better than that of a single-element additive solution.

[0079] (6) Examples 5 and 6 show that by keeping the same process conditions, changing the addition of AlCl3 and AMT mixed additive solution to first adding AlCl3 additive solution for de-adsorption treatment and then sintering and coating AlCl3, and then adding AMT additive solution for de-adsorption treatment and then sintering and coating AMT, the cycle performance of the porous cathode material is better improved.

[0080] (7) Examples 2, 7, 8 and 9 show that when the desizing time is insufficient or too long, the cycle improvement performance of porous cathode materials is poor when the same process conditions are maintained.

[0081] (8) Examples 2, 10 and 11 show that, under the same process conditions, a faster heating rate for descaling can bring better cycle improvement to porous cathode materials.

[0082] (9) Examples 2, 12 and 13 show that when the temperature of the desizing treatment is too low or too high while maintaining the same process conditions, the cycle improvement effect of the porous cathode material is poor.

[0083] In summary, the method for preparing porous cathode materials provided in this invention employs a cold-drying process for the desizing treatment. This involves first rapidly cooling the solution to solidify it, then rapidly heating it to vaporize the solidified solution, quickly removing the solvent from the system. This ensures that the solute is well retained on the surface of the primary grains of the porous cathode material, resulting in a high coating rate and a large number of primary grains with a coating layer on the surface. The preparation method provided by this invention is simple; by repeating the coating treatment, desizing treatment, and first sintering treatment n times, a multi-layered porous cathode material can be prepared.

[0084] The side reactions between the lithium-ion battery and the electrolyte are weakened during cycling, resulting in significantly improved cycle performance.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a porous cathode material, characterized in that, Includes the following steps: After repeating the coating process, desizing process, and first sintering process n times, a porous cathode material is prepared. In the (n+1)th repeated operation, the product after the first sintering treatment in the nth time is used as the raw material for the (n+1)th coating treatment; 1≤n≤3; The deagent removal treatment includes: lowering the temperature of the coated system to -50°C to -20°C for 0.6h to 1.5h, and then raising the temperature of the system to 5°C to 200°C for 0.1h to 1.5h under the triple point pressure of water.

2. The preparation method according to claim 1, characterized in that, In the deaerator treatment, a cooling process is carried out at a rate of 0.5℃ / min-2.0℃ / min, and a heating process is carried out at a rate of 1.5℃ / min-3.5℃ / min.

3. The preparation method according to claim 2, characterized in that, The desiccant treatment is carried out in a vacuum environment under pressure ≤600Pa.

4. The preparation method according to claim 1, characterized in that, The coating process includes: mixing the positive electrode material and water in a certain proportion, adding additives, and coating the material at a temperature of 30℃-50℃ for 1 min-30 min; wherein the solid-liquid ratio of the positive electrode material and water is 1:(0.5-2), and the concentration of the additives is 0.5mol / L-3mol / L. Preferably, during the coating process, the additive is added at a rate of 50 mL / min to 70 mL / min.

5. The preparation method according to claim 4, characterized in that, The additive is selected from at least one of aluminum source, tungsten source and titanium source; The aluminum source is selected from at least one of sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum phosphate, and aluminum chloride. The tungsten source is selected from at least one of ammonium tungstate, ammonium metatungstate, ammonium paratungstate, phosphotungstic acid, and sodium tungstate; The titanium source includes titanium dihydrogen phosphate.

6. The preparation method according to claim 5, characterized in that, The preparation of the cathode material includes: The lithium source, nickel source, cobalt source and manganese source are mixed in a molar ratio of (0.9-1.1):x:y:z and then subjected to a second sintering treatment to obtain the cathode material, wherein x≥0.9, 0<y+z≤0.1, and x+y+z=1; The second sintering treatment includes: raising the system temperature to 550℃-650℃ at a rate of 1.5℃ / min-3.5℃ / min and holding it at that temperature for 3.5h-6h, then raising the temperature to 700℃-820℃ at a rate of 1.5℃ / min-3.5℃ / min and sintering for 8.5h-9.5h; after the second sintering treatment is completed, cooling the system to room temperature at a rate of 1.5℃ / min-3.5℃ / min.

7. The preparation method according to claim 6, characterized in that, The preparation of the positive electrode material also includes the addition of a pore-forming agent, one or more oxides or salts; The pore-forming agent is selected from at least one of potassium sulfate and sodium sulfate; The oxide is a metal oxide, and the metal element is selected from at least one of Zr, Mg, Y, Sr, Sb, Ca, Nb, and Mo; the molar ratio of the metal element is in the range of 0.0001-0.

01. Salts are selected from at least one of carbonates, sulfates, and nitrates.

8. The preparation method according to claim 1, characterized in that, The first sintering treatment includes: raising the system temperature to 300℃-500℃ at a rate of 1.5℃ / min-3.5℃ / min and holding it at that temperature for 3.5h-8h; and after the second sintering treatment is completed, cooling the system to room temperature at a rate of 1.5℃ / min-3.5℃ / min.

9. A porous cathode material prepared by the preparation method according to any one of claims 1-8, characterized in that, The porous cathode material has the chemical formula Li. s Ni x Co y Mn z M w N p O2, wherein M is at least one of Al, W, and Ti, and N is at least one of Zr, Mg, Y, Sr, Sb, Ca, Nb, Mo, and B; 0.9 ≤ s ≤ 1.1, x ≥ 0.9, 0 <y+z≤0.1,0.0001≤p≤0.01,w=0.005-0.05。 10. A lithium-ion battery, characterized in that, This includes porous cathode materials prepared by the preparation method according to any one of claims 1-8 or porous cathode materials according to claim 9.

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