Lithium-ion positive electrode material, preparation method therefor and application thereof

Abstract

Disclosed are a lithium-ion positive electrode material, a preparation method therefor and an application thereof. The lithium-ion positive electrode material has a crack resistance strength of 4-15 MPa, and has high-strength crystals and grain boundaries, which improve the structural stability of the material, and effectively inhibit internal cracks from propagating to an interface, thereby improving the cycle stability and service life of the material.

Description

A lithium-ion battery cathode material, its preparation method and application

[0001] Cross-references to related applications

[0002] This disclosure claims priority to Chinese Patent Application No. 2024109102998, filed on July 9, 2024, entitled "A Lithium-ion Battery Cathode Material, Its Preparation Method and Application", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of lithium battery technology, and more specifically, to a lithium battery cathode material, its preparation method, and its application. Background Technology

[0004] The rapid development of lithium-ion batteries has driven the rapid development of ternary cathode materials. Ternary cathode materials have advantages such as high specific capacity, moderate price, low toxicity, and relatively abundant resources. However, ternary materials also have many problems, especially nickel-rich ternary materials, which have poor battery cycle performance, undergo multi-stage phase transitions during charge and discharge, and are prone to residual stress due to large volume changes during charge and discharge, leading to mechanical fracture.

[0005] To improve the tap density of ternary materials while suppressing surface side reactions, the ternary materials are prepared as secondary particles consisting of densely packed primary particles. This significantly reduces the contact between the primary particles and the electrolyte, thereby minimizing interfacial side reactions. However, secondary particles still bring new problems: First, secondary particles require a very dense arrangement of primary particles, especially a dense interface, to effectively block the contact between the internal primary particles and the electrolyte. This dense secondary particle structure greatly increases the difficulty of synthesis. Second, the expansion and contraction of the secondary particles during charging and discharging causes an increase in internal stress. Long-term cycling allows these stresses to gradually accumulate, leading to microcracks inside and on the surface of the secondary particles, eventually causing the entire secondary particle to break.

[0006] The mechanical fracture of ternary cathode materials develops through the following process: During charging, as Li... + As Li is extracted, the interlayer spacing of the ternary material gradually increases. This is mainly due to the extraction of Li. + Electrostatic repulsion between layers increases after delithiation. When the high delithiation state is reached, the interlayer spacing shrinks. This shrinkage may be due to the transition of Li. +Structural slippage caused by delamination from the interlayer may also be due to the participation of oxygen in redox reactions, leading to reduced electrostatic repulsion and a smaller interlayer spacing. During discharge, the change in interlayer spacing is completely opposite to that during charging. In a single charge-discharge cycle, the layered material undergoes four expansion and contraction cycles, inevitably generating residual stress during volume changes. The accumulation of residual stress leads to microcracks at grain boundaries between particles, increasing contact with the electrolyte, exacerbating interfacial side reactions, further accelerating the propagation of microcracks, and ultimately causing particle breakage, resulting in decreased battery capacity or even failure. Therefore, the final breakage of polycrystalline ternary cathode material particles is related to the deformation of the ternary cathode material's unit cell and the failure of its grain boundaries. Both unit cells and grain boundaries jointly influence whether cathode materials are prone to cracking during use; therefore, providing cathode materials with both high-strength crystals and high-strength grain boundaries is of great significance.

[0007] Therefore, there is an urgent need to provide cathode materials that simultaneously possess high-strength crystals and grain boundaries to improve the material's ability to resist the formation of internal cracks during cycling, thereby enhancing the material's cycling stability and lifespan.

[0008] In view of this, this disclosure is hereby made.

[0009] Summary of the Invention

[0010] The purpose of this disclosure is to provide a lithium-ion battery cathode material, its preparation method and application, which aims to improve the material's ability to resist the formation of internal cracks during cycling, thereby improving the material's cycle stability and lifespan.

[0011] This disclosure is implemented as follows:

[0012] In a first aspect, this disclosure provides a lithium battery cathode material, wherein the crack resistance of the lithium battery cathode material is 4-15 MPa;

[0013] in,

[0014] In the formula, St represents the crushing strength, which is obtained through an indentation test and is measured in MPa. This represents the average crushing strength, measured in MPa. n is the sample size, n≥10;

[0015] This refers to the maximum change in shear strain during the initial charging process;

[0016] It refers to the change in shear strain after 10 charge-discharge cycles, t=10;

[0017] [Corrected according to Rule 91, March 24, 2026] This refers to the shear strain measured under static conditions after 10 charge-discharge cycles. This refers to the shear strain measured under static conditions before the first charge;

[0018] a and c represent the unit cell parameters.

[0019] In an optional embodiment, the crack resistance of the lithium battery cathode material is 6-15 MPa;

[0020] St=2.8×P / (πd 2 );

[0021] P represents the maximum pressure value before the pressure drop point in the indentation test, in mN;

[0022] d represents the particle diameter of the lithium battery cathode material, in μm;

[0023] The value ranges from 0.2 to 0.3. The value of is 0.01-0.20, and the value of St is 90-140 MPa;

[0024] c and a were obtained by X-ray diffraction (XRD).

[0025] In an optional implementation, the general formula of the lithium-ion battery cathode material is Li. x Ni a Co b M c M' 1-a-b-c A y O 2-y ;

[0026] In the general formula, M is selected from at least one of Al and Mn;

[0027] M' is selected from at least one of Zr, Sr, Mo, Ba, W, B, Ti, Mg, Li, Si, Ca, Cu, La, Ce, Bi, In, Al, Nb, and Y;

[0028] A is selected from at least one of P and F;

[0029] 0.95≤x<1.1, a>0, b>0, c>0, 0.95≤(a+b+c)≤1, 0≤y≤0.01.

[0030] Secondly, this disclosure also provides a method for preparing a lithium battery cathode material, comprising: preparing a lithium battery cathode material that meets the requirements for crack resistance strength.

[0031] In an optional embodiment, the precursor core is prepared by co-precipitation reaction of nickel salt, cobalt salt and M salt;

[0032] The precursor core is mixed with a strengthening solution and reacted, and then calcined to obtain a strengthened precursor core; wherein, the raw materials in the strengthening solution are calcined to obtain a strengthening agent; the strengthening agent is selected from at least one of LiAlO2, LiMn2O4 and LiCoPO4;

[0033] A ternary precursor with a core-shell structure is obtained by co-precipitation reaction using nickel salt, cobalt salt, M salt and a first doping element compound to reinforce the precursor core and then grow the outer shell; wherein the doping element contained in the first doping element compound is selected from at least one of Ti, Al, Zr and Mg.

[0034] The ternary precursor is mixed with a lithium source and calcined; or, the ternary precursor, the second doping element compound, and the lithium source are mixed and calcined; the doping element contained in the second doping element compound is selected from at least one of Zr, Sr, Mo, Ba, W, B, Ti, Mg, Li, F, Si, Ca, Cu, La, P, Ce, Bi, In, Nb, and Y.

[0035] In an optional implementation, the primary particles of the precursor core are arranged radially in a radial pattern and have a porosity of 4%-12%.

[0036] In an optional embodiment, the preparation process of the precursor core includes: preparing a base liquid in a reaction vessel, and passing a first mixed metal salt solution, a first precipitant solution, and a first complexing agent solution into the base liquid to carry out a co-precipitation reaction, wherein the process of preparing the precursor core satisfies at least one of features A1-E1:

[0037] Feature A1: The reaction temperature of the coprecipitation reaction is controlled at 75℃-95℃;

[0038] Feature B1: The reaction pH for controlling the coprecipitation reaction is 10.5-11.5;

[0039] Feature C1: Stop feeding after the particle size D50 reaches 2-17μm;

[0040] Feature D1: The coprecipitation reaction is carried out under an inert atmosphere, and the rotation speed is 400 rpm-800 rpm during the reaction.

[0041] Feature E1: After the co-precipitation reaction is completed, the product is aged, followed by alkali washing, water washing, and drying.

[0042] In an optional implementation, the process of preparing the precursor kernel satisfies at least one of the following: feature F1 - feature K1.

[0043] Feature F1: The first complexing agent solution is an ammonia solution with a mass fraction of 18%-22%, and the ammonia concentration in the reaction vessel is controlled at 3g / L-7g / L during the precipitation process;

[0044] Feature G1: The total molar concentration of metal ions in the first mixed metal salt solution is 1.8M-2.2M, and the flow rate of the first mixed metal salt solution is 400L / h-500L / h;

[0045] Feature H1: The molar ratio of nickel, cobalt and M in the first mixed metal salt solution is (35-98):(1-35):(1-35);

[0046] Feature I1: The salts in the first mixed metal salt solution are selected from any one of nitrates, chlorides, and sulfates;

[0047] Feature J1: The first precipitant solution is a sodium hydroxide solution with a mass fraction of 30%-34%;

[0048] Characteristic K1: The concentration of ammonia in the bottom solution is 4.5 g / L-5.5 g / L, and the pH value is 11.8-12.2.

[0049] In an optional embodiment, the preparation process of the reinforced precursor core includes: mixing the precursor core with the reinforcement solution and then sonicating it, reacting it for 10 min to 60 min at a temperature of 100℃-150℃ and a pressure of 10MPa-20MPa, followed by solid-liquid separation, and calcining the obtained solid material.

[0050] In an optional implementation, the preparation process of the reinforced precursor core satisfies at least one of feature A2-feature F2:

[0051] Feature A2: The strengthening solution also contains a thickener, and the viscosity of the strengthening solution is adjusted to 5 mPa·s-8 mPa·s by controlling the amount of thickener.

[0052] Feature B2: When feature A2 is satisfied, the thickener is selected from at least one of carbomer, xanthan gum, gelatin and starch;

[0053] Feature C2: 1g of precursor core corresponds to 90mL-110mL of reinforcement solution;

[0054] Feature D2: Control the ultrasound time to 10 min-60 min;

[0055] Feature E2: The calcination temperature is controlled at 600℃-700℃, and the calcination time is 3h-8h;

[0056] Feature F2: The solid material is first dried at 80℃-120℃ for 5h-10h, and then calcined.

[0057] In an optional embodiment, the preparation process of the ternary precursor with a core-shell structure includes: adding the reinforced precursor core to the bottom liquid in the reactor, and introducing the second mixed metal salt solution, the second precipitant solution, and the second complexing agent solution into the reactor to carry out a co-precipitation reaction;

[0058] The second mixed metal salt solution contains nickel salt, cobalt salt, M salt and a first doping element compound. By controlling the addition rate of the second mixed metal salt solution, the addition rate of nickel, cobalt and M elements during the reaction process is controlled to be lower than the addition rate when preparing the precursor core.

[0059] In an optional implementation, the preparation process of the ternary precursor with a core-shell structure satisfies at least one of features A3-I3:

[0060] Feature A3: The total molar concentration of nickel, cobalt and M elements in the second mixed metal salt solution is 1.8M-2.2M, the flow rate of the second mixed metal salt solution is 100L / h-200L / h, and the pH value of the second mixed metal salt solution is adjusted to 2-5;

[0061] Feature B3: The total molar amount of metal is calculated based on the total molar amount of nickel, cobalt and M elements. The ratio of the total molar amount of metal in the core of the reinforced precursor to the total molar amount of metal in the second mixed metal salt solution is (4-12):1.

[0062] Feature C3: In the second mixed metal salt solution, the molar ratio of nickel, cobalt and M is (30-60):(20-35):(20-35);

[0063] Characteristic D3: The reaction temperature for the coprecipitation reaction is 75℃-95℃, and the reaction pH is 10.8-11.2;

[0064] Feature E3: The second complexing agent solution is an ammonia solution with a mass fraction of 18%-22%, and the ammonia concentration in the reaction vessel is controlled at 3g / L-7g / L during the precipitation process;

[0065] Feature F3: The first dopant compound is selected from at least one of titanium disulfide, sodium aluminate, zirconium nitrate, zirconium acetate, zirconium sulfate, magnesium sulfate, and magnesium nitrate;

[0066] Feature G3: The bottom liquid in the reactor is water, and the second precipitant solution is a sodium hydroxide solution with a mass fraction of 30%-40%;

[0067] Feature H3: The coprecipitation reaction is carried out under an inert atmosphere, and the rotation speed is 300 rpm-500 rpm during the reaction.

[0068] Feature I3: After the second mixed metal salt solution is added, the reaction continues for 0.5h-2.0h, followed by solid-liquid separation. The obtained solid material is then washed with water and dried.

[0069] In an optional implementation, the process of mixing and calcining the ternary precursor, the second dopant compound, and the lithium source satisfies at least one of characteristics A4-F4:

[0070] Feature A4: The molar ratio of the total amount of nickel, cobalt and M elements in the ternary precursor to the lithium content in the lithium source is 1:(1.05-1.1);

[0071] Feature B4: The lithium source is selected from lithium hydroxide;

[0072] Characteristic C4: The second dopant compound is selected from at least one of oxides, fluorides, carbonates, hydroxides, nitrides, borides, and nitrates;

[0073] Feature D4: During the calcination process, the first calcination is carried out at 400℃-500℃ for 2h-6h, followed by a second calcination at 750℃-850℃ for 10h-15h.

[0074] Feature E4: Calcination is carried out in an oxygen-containing atmosphere;

[0075] Feature F4: First, the ternary precursor, the second doped element compound, and the lithium source are mixed and ground, and then calcined.

[0076] Thirdly, this disclosure also provides a positive electrode sheet, comprising the lithium battery positive electrode material in any of the above embodiments or the lithium battery positive electrode material prepared by the preparation method in any of the above embodiments.

[0077] Fourthly, this disclosure also provides a lithium battery, including the positive electrode sheet in the above embodiments.

[0078] This disclosure offers the following advantages: by constructing a formula for calculating crack resistance strength, the ability of polycrystalline cathode materials to resist the formation of internal cracks during cycling is evaluated. Taking into account the influence of unit cells and grain boundaries, the crack resistance strength is made to meet a specific value range. Cathode materials with crack resistance strength meeting this specific value range possess high-strength crystals and grain boundaries, which can improve the structural stability of the material, effectively suppress the propagation of internal cracks to the interface, and thus improve the cycling stability and lifespan of the material. Attached Figure Description

[0079] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this disclosure and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0080] Figure 1 is an ion cross-sectional view of the cathode material prepared in Example 1;

[0081] Figure 2 is an ion cross-sectional view of the cathode material prepared in Comparative Example 1;

[0082] Figure 3 is a cross-sectional view of the cathode material prepared in Example 1;

[0083] Figure 4 is a cross-sectional view of the cathode material prepared in Comparative Example 2;

[0084] Figure 5 shows the XRD patterns of the precursor core and precursor material in Example 1;

[0085] Figure 6 shows the TEM and EDS images of the cathode material prepared in Example 1; (a) represents the TEM image, and (b) represents the EDS image.

[0086] Figure 7 shows the TEM and EDS images of the cathode material prepared in Example 4; (a) represents the TEM image, and (b) represents the EDS image. Detailed Implementation

[0087] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions in the embodiments of this disclosure 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.

[0088] This disclosure provides a lithium-ion battery cathode material, which is a secondary particle formed by the agglomeration of primary particles, belonging to polycrystalline materials. The general formula of the lithium-ion battery cathode material is Li. x Ni a Co b M c M' 1-a-b-c A y O 2-y .

[0089] The parameters in the general formula are explained as follows:

[0090] M is selected from at least one of Al and Mn, and M can be any one or both of the above.

[0091] M' is selected from at least one of Zr, Sr, Mo, Ba, W, B, Ti, Mg, Li, Si, Ca, Cu, La, Ce, Bi, In, Al, Nb, and Y, and M' can be any one or more of the above.

[0092] A is selected from at least one of P and F, and can be any one or both of them.

[0093] x, y, a, b, and c are expressed in mol, and 0.95 ≤ x < 1.1. Specifically, x can be 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.03, 1.05, 1.08, 1.10, etc.

[0094] Given a > 0, b > 0, c > 0, and 0.95 ≤ (a + b + c) ≤ 1, where a + b + c can be 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, etc. When a + b + c = 1, there is no element M'.

[0095] 0 ≤ y ≤ 0.01, and the value of y can be 0.000, 0.003, 0.005, 0.008, 0.010, etc. When the value of y is 0, the cathode material does not contain element A.

[0096] The inventors discovered that crystal strength and grain boundary strength simultaneously determine the ability of a cathode material to resist the formation of internal cracks during cycling, and their relationship can be expressed by the following formula:

[0097] In the formula, St represents the crushing strength, obtained through an indentation test, in MPa; the pressure calculated from the maximum pressure value before the pressure drop point during the test is taken as the crushing strength of the material, St=2.8×P / (πd 2 P represents the maximum pressure value before the pressure drop point, in mN; d represents the particle diameter of the lithium battery cathode material, in μm.

[0098] This represents the average crushing strength. n is the sample size, n≥10;

[0099] This refers to the maximum change in shear strain during the initial charging process, reflecting the degree of immediate deformation of the material; that is:

[0100] [Corrected according to Rule 91, March 24, 2026] It refers to the change in shear strain after 10 charge-discharge cycles (i.e., t=10), reflecting the irreversible strain accumulated during the material cycling process. This refers to the shear strain measured under static conditions after 10 charge-discharge cycles. This refers to the shear strain measured under static conditions before the first charge;

[0101] c represents the unit cell parameter; a represents the unit cell parameter. c and a are obtained by X-ray diffraction (XRD).

[0102] The crack resistance of the lithium battery cathode material provided in this embodiment is 4-15 MPa, preferably 6-15 MPa, and can be 4 MPa, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa, 15 MPa, etc., or any value among the above adjacent values.

[0103] The value ranges from 0.2 to 0.3, such as 0.20, 0.22, 0.25, 0.28, and 0.30.

[0104] The value ranges from 0.01 to 0.20, such as 0.01, 0.03, 0.05, 0.08, 0.10, 0.12, 0.15, 0.18, and 0.20.

[0105] The value of St ranges from 90 to 140 MPa, such as 90 MPa, 100 MPa, 110 MPa, 120 MPa, 130 MPa, 140 MPa, etc.

[0106] It should be noted that the crack resistance strength parameters provided in this disclosure can comprehensively evaluate various factors that cause internal cracks in cathode materials, including the crystal structure itself and grain boundary strength. This reflects the crystal's resistance to deformation during the charging process; This reflects the permanent deformation that occurs during crystal cycling, indicating an irreversible phase transition. Both of these factors reflect the influence of the crystal structure itself on the formation of internal cracks. Crushing strength reflects the strength of grain boundaries; in polycrystalline materials, cracks first form at grain boundaries (the contact surfaces between primary particles) because grain boundaries have lower bonding strength than the internal crystal structure. Experimental verification shows that the greater the crack resistance, the smaller the rate of change in specific surface area after equal charge-discharge cycles. Specific surface area reflects the degree of microcrack formation; the more microcracks formed, the worse the material's cycling stability. In summary, the greater the crack resistance, the higher the cycling stability of the material.

[0107] Cell deformation is an inherent characteristic of materials, and this problem is usually mitigated by improving chemical bond strength through doping. For grain boundary failure, it is typically improved by controlling the grain shape of primary particles and their morphology after aggregation, as well as by using doping elements. The inventors also provide a method for preparing a lithium-ion battery cathode material, which uses doping elements in conjunction with the core and shell to ensure the product's crack resistance meets requirements. The specific preparation process is as follows:

[0108] This disclosure provides a method for preparing a lithium-ion battery cathode material, including the following steps:

[0109] S1. Preparation of precursor core

[0110] The precursor core is prepared by co-precipitation reaction of nickel salt, cobalt salt and M salt (i.e. salt containing element M in the general formula). M salt can be manganese salt or aluminum salt.

[0111] In some embodiments, the primary particles of the precursor core are arranged radially in a radial pattern, and the porosity is 4%-12% (e.g., 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, etc.). The radial arrangement of primary particles and the maintenance of a certain porosity are beneficial to stress dissipation, to suppressing the formation of intergranular cracks during the cycling process of the cathode material, and to delaying the irreversible phase transformation from the layered phase to the rock salt phase, thereby improving the structural stability of the ternary cathode material.

[0112] In some embodiments, the preparation process of the precursor core includes: preparing a base liquid in a reactor, introducing a first mixed metal salt solution, a first precipitant solution, and a first complexing agent solution into the base liquid, and carrying out a co-precipitation reaction under an inert atmosphere. The reaction temperature of the co-precipitation reaction is controlled at 75℃-95℃, the reaction pH value is 10.5-11.5, and the rotation speed is 400rpm-800rpm. The particles gradually grow, and the feed is stopped after the particle size D50 reaches 2-17μm. After the co-precipitation reaction is completed, aging is carried out, followed by alkali washing, water washing, and drying. Alkali washing removes sodium and sulfur residues, water washing removes residual alkali from the surface, and drying removes moisture. After drying, the core can be sieved to obtain a precursor core with a particle size that meets the requirements.

[0113] Specifically, the reaction temperature for the coprecipitation reaction can be 75℃, 80℃, 85℃, 90℃, 95℃, etc., the pH value can be 10.5, 10.8, 11.0, 11.2, 11.5, etc., and the rotation speed can be 400rpm, 500rpm, 600rpm, 700rpm, 800rpm, etc. The particle size of the product is monitored during the reaction, and the particle size D50 is controlled to be 2μm, 5μm, 8μm, 10μm, 12μm, 15μm, 17μm, etc. at the end of the reaction. The inert atmosphere can be nitrogen, but is not limited to this. Alkaline washing can be performed using a hot, dilute alkaline solution to effectively remove sodium and sulfur residues.

[0114] In some embodiments, the first complexing agent solution is an ammonia solution with a mass fraction of 18%-22%, and the ammonia concentration in the reaction vessel during precipitation is controlled to be 3g / L-7g / L by adjusting the addition rate of the first complexing agent solution; the first precipitant solution is a sodium hydroxide solution with a mass fraction of 30%-34%, and the pH value of the system is controlled to meet the requirements by adjusting the addition rate of the first precipitant solution. Specifically, the mass fraction of the ammonia solution can be 18%, 20%, 22%, etc., and the ammonia concentration in the reaction vessel during precipitation can be controlled to be 3g / L, 4g / L, 5g / L, 6g / L, 7g / L, etc.; the mass fraction of the sodium hydroxide solution can be 30%, 31%, 32%, 33%, 34%, etc.

[0115] In some embodiments, the molar ratio of nickel, cobalt, and M in the first mixed metal salt solution is (35-98):(1-35):(1-35), the total molar concentration of metal ions in the first mixed metal salt solution is 1.8M-2.2M, and the flow rate of the first mixed metal salt solution is 400L / h-500L / h. By further adjusting the composition, concentration, and addition rate of the first mixed metal salt solution, the deposition rate can be controlled, resulting in a porous morphology in the precursor core.

[0116] Specifically, in the first mixed metal salt solution, the molar ratio of nickel, cobalt, and element M can be 35:30:35, 40:30:30, 50:20:30, 60:20:20, 70:10:20, 80:10:10, 90:5:5, 98:1:1, etc. The total molar concentration of metal ions in the first mixed metal salt solution refers to the total concentration of nickel, cobalt, and element M, and can be 1.8M, 1.9M, 2.0M, 2.1M, 2.2M, etc. The flow rate of the first mixed metal salt solution can be 400 L / h, 420 L / h, 450 L / h, 480 L / h, 500 L / h, etc.

[0117] Furthermore, the salt in the first mixed metal salt solution is selected from any one of nitrates, chlorides, and sulfates, and can be any one of the above salts, such as all of them being nitrates, using nickel nitrate, cobalt nitrate, and manganese nitrate (or aluminum nitrate) as raw materials.

[0118] In some embodiments, the substrate solution can be prepared using an aqueous ammonia solution and a sodium hydroxide solution, with an ammonia concentration of 4.5 g / L-5.5 g / L and a pH value of 11.8-12.2 to meet the co-precipitation reaction conditions. Specifically, the ammonia concentration in the substrate solution can be 4.5 g / L, 5.0 g / L, 5.5 g / L, etc., and the pH value can be 11.8, 11.9, 12.0, 12.1, 12.2, etc., with the volume of the substrate solution occupying 60%-80% of the reactor volume.

[0119] S2. Preparation of reinforced precursor core

[0120] The precursor core is mixed with a strengthening solution and reacted. After calcination, a strengthening agent is introduced to obtain a strengthened precursor core. The introduced strengthening agent is selected from at least one of LiAlO2, LiMn2O4, and LiCoPO4, and can be any one or more of these. The grain boundaries of the primary particles in the precursor core are strengthened using a sol-gel method, thereby enhancing the grain boundary strength of the primary particles.

[0121] In some embodiments, the preparation process of the reinforced precursor core includes: mixing the precursor core with a reinforcing solution and sonicating for 10-60 minutes, then reacting for 10-60 minutes at a temperature of 100℃-150℃ and a pressure of 10MPa-20MPa. After the reaction is complete, the solid and liquid are separated, and the resulting solid material is calcined. The reaction is carried out under high temperature and high pressure conditions, and the reaction liquid is pressurized by heating to vaporize the solvent, ensuring that the precursor core is completely impregnated.

[0122] Specifically, the ultrasonic mixing time between the precursor core and the reinforcement solution can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, etc. The high-temperature and high-pressure reaction can be carried out in a general high-pressure reactor. The reaction temperature can be controlled at 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc., and the reaction pressure can be controlled at 10 MPa, 13 MPa, 15 MPa, 18 MPa, 20 MPa, etc. The pressure holding reaction time can be 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, etc.

[0123] The raw materials in the strengthening solution can be calcined to obtain the aforementioned strengthening agent. For example, if the strengthening agent is LiMn2O4, the raw materials can be manganese acetate and lithium hydroxide.

[0124] In some embodiments, the strengthening solution also contains a thickener. The amount of thickener is adjusted to make the viscosity of the strengthening solution 5 mPa·s-8 mPa·s. Higher viscosity is beneficial for the strengthening solution to remain in the pores of the precursor core, further crystallizing during calcination. That is, if the viscosity is too low, the doping amount is also low; if the viscosity is too high, it is not easy to enter the pores, resulting in an excessively low doping amount. The thickener is selected from at least one of carbomer, xanthan gum, gelatin, and starch, and the thickener can be any one or more of the above. 1g of precursor core corresponds to 90mL-110mL of strengthening solution, such as 90mL, 95mL, 100mL, 105mL, or 110mL.

[0125] In some embodiments, the calcination temperature is controlled at 600℃-700℃, and the calcination time is 3h-8h. After calcination, a reinforcing agent can be introduced into the precursor core to strengthen the grain boundary strength of the primary particles. Specifically, the calcination temperature can be 600℃, 620℃, 650℃, 680℃, 700℃, etc., and the calcination time can be 3h, 4h, 5h, 6h, 7h, 8h, etc.

[0126] In some embodiments, the solid material can be dried at 80℃-120℃ for 5h-10h before calcination to fully remove surface moisture before calcination. Specifically, the drying temperature can be 80℃, 90℃, 100℃, 110℃, 120℃, etc.; the drying time can be 5h, 6h, 7h, 8h, 9h, 10h, etc.

[0127] S3. Preparation of ternary precursors with core-shell structures

[0128] By using a co-precipitation reaction of nickel salt, cobalt salt, M salt and a compound of the first dopant element, a shell is grown on the basis of strengthening the precursor core, resulting in a ternary precursor with a core-shell structure.

[0129] In some embodiments, the preparation process of a ternary precursor with a core-shell structure includes: adding a reinforced precursor core to a bottom liquid in a reaction vessel, and introducing a second mixed metal salt solution, a second precipitant solution, and a second complexing agent solution into the reaction vessel for a co-precipitation reaction; wherein the second mixed metal salt solution contains nickel salt, cobalt salt, M salt, and a first dopant element compound, and by controlling the addition rate of the second mixed metal salt solution, the addition rate of nickel, cobalt, and M elements during the reaction is made lower than the addition rate when preparing the precursor core. By reducing the addition rate of the second mixed metal salt solution to control the co-precipitation reaction rate, it is beneficial to obtain a denser shell.

[0130] Furthermore, in the second mixed metal salt solution, the molar ratio of nickel, cobalt, and M is (30-60):(20-35):(20-35), preparing a dense, low-Ni-content, element-doped shell. This helps reduce contact with the electrolyte, and the element doping and low Ni content improve the strength and stability of the crystal structure, enhancing its strain resistance and suppressing the propagation of internal cracks to the interface. In the second mixed metal salt solution, the total molar concentration of nickel, cobalt, and M is 1.8M-2.2M. Before adding it to the reactor, the pH of the second mixed metal salt solution is adjusted to 2-5 by adding acid to prevent precipitation. During precipitation, a peristaltic pump can be used to slowly drip the second mixed metal salt solution into the reactor, controlling the flow rate to 100L / h-200L / h.

[0131] Specifically, in the second mixed metal salt solution, the molar ratio of nickel, cobalt, and element M can be 30:35:35, 40:30:30, 50:25:25, 60:20:20, etc. The total molar concentration of nickel, cobalt, and element M in the second mixed metal salt solution can be 1.8M, 1.9M, 2.0M, 2.1M, 2.2M, etc. Before adding it to the reaction vessel, the pH value of the second mixed metal salt solution can be adjusted to 3.5, 3.8, 4.0, 4.2, 4.5, etc. The flow rate of the second mixed metal salt solution can be 100L / h, 120L / h, 150L / h, 180L / h, 200L / h, etc.

[0132] Furthermore, the total molar amount of metal is calculated based on the total molar amounts of nickel, cobalt, and M elements. The ratio of the total molar amount of metal in the core of the reinforced precursor to the total molar amount of metal in the second mixed metal salt solution is (4-12):1. By adjusting the amounts of the core and shell, the ratio of the core and shell can be better controlled, thereby improving the electrochemical performance of the material. Specifically, the ratio of the total molar amount of metal in the core of the reinforced precursor to the total molar amount of metal in the second mixed metal salt solution can be 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, 11:1, 12:1, etc.

[0133] The first doping element compound contains at least one doping element selected from Ti, Al, Zr, and Mg, and the doping element can be any one or more of the above. The first doping element compound is selected from at least one of titanium disulfate, sodium aluminate, zirconium nitrate, zirconium acetate, zirconium sulfate, magnesium sulfate, and magnesium nitrate, and the amount used is adjusted according to the doping amount of the doping element.

[0134] In some embodiments, the bottom liquid in the reactor is water, and the volume of water added to the reactor can be 15%-25% of the reactor volume. The second precipitant solution is a sodium hydroxide solution with a mass fraction of 30%-40%, and the pH value during the reaction is maintained at 10.8-11.2 by adjusting the addition rate of the second precipitant solution. The second complexing agent solution is an ammonia solution with a mass fraction of 18%-22%, and the ammonia concentration in the reactor is controlled at 3g / L-7g / L during the precipitation process. Specifically, the mass fraction of the sodium hydroxide solution can be 30%, 32%, 34%, 36%, 38%, 40%, etc., and the pH value during the reaction can be 10.8, 10.9, 11.0, 11.1, 11.2, etc.; the mass fraction of the ammonia solution can be 18%, 19%, 20%, 21%, 22%, etc., and the ammonia concentration in the reactor can be controlled at 3g / L, 4g / L, 5g / L, 6g / L, 7g / L, etc. during the precipitation process.

[0135] In some embodiments, the precipitation process can be carried out in an inert atmosphere (such as nitrogen), the reaction temperature of the coprecipitation reaction is 75℃-95℃, and the rotation speed during the reaction is 300rpm-500rpm to ensure a uniform reaction rate. Specifically, the reaction temperature can be 75℃, 80℃, 85℃, 90℃, 95℃, etc., and the rotation speed during the reaction can be 300rpm, 400rpm, 500rpm, etc.

[0136] Furthermore, after the second mixed metal salt solution is added, the reaction continues for 0.5h-2.0h (e.g., 0.5h, 1.0h, 1.5h, 2.0h, etc.), followed by solid-liquid separation. The obtained solid material is then washed with water and dried to obtain a precursor with a dense outer shell.

[0137] S4. Preparation of ternary cathode materials

[0138] The ternary precursor, the second doped element compound, and the lithium source were mixed and calcined to obtain the ternary cathode material.

[0139] The dopant element in the second dopant compound is selected from at least one of Zr, Sr, Mo, Ba, W, B, Ti, Mg, Li, F, Si, Ca, Cu, La, P, Ce, Bi, In, Nb, and Y. The dopant element in the second dopant compound can be any one or more of the above. The second dopant compound is selected from at least one of oxides, fluorides, carbonates, hydroxides, nitrides, borides, and nitrates. The dopant element can be any one or more of the above. By adjusting the amount of the second dopant compound, the doping level of the dopant element meets the requirements.

[0140] In some embodiments, the lithium source can be lithium hydroxide, but is not limited thereto. The molar ratio of the total amount of nickel, cobalt and M elements in the ternary precursor to the lithium content in the lithium source is 1:(1.05-1.1), and can be 1:1.05, 1:1.06, 1:1.07, 1:1.08, 1:1.09, 1:1.10, etc.

[0141] In some embodiments, calcination is carried out in an oxygen-containing atmosphere. During the calcination process, a first calcination is performed at 400℃-500℃ for 2-6 hours, followed by a second calcination at 750℃-850℃ for 10-15 hours. Through this two-stage calcination process, first a low-temperature calcination and then a high-temperature calcination, a uniform lithium-ion battery cathode material is obtained. Specifically, the oxygen-containing atmosphere can be an oxygen atmosphere, but is not limited to it. The temperature of the first calcination can be 400℃, 420℃, 450℃, 480℃, 500℃, etc., and the first calcination time can be 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, etc.; the temperature of the second calcination can be 750℃, 780℃, 800℃, 820℃, 850℃, etc., and the second calcination time can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, etc.

[0142] In some embodiments, the ternary precursor, the second doped element compound, and the lithium source are first mixed and ground, and then calcined. Grinding helps to better mix the raw materials evenly, which is beneficial to improving the uniformity of the cathode material.

[0143] It should be noted that the lithium battery cathode material prepared in the embodiments of this disclosure has high crack resistance, a core-shell structure, primary particles in the core are arranged radially in a radial pattern and have a certain porosity; the outer shell is relatively dense and has doped elements and a low Ni content.

[0144] This disclosure also provides a positive electrode sheet, including the above-mentioned lithium battery positive electrode material, with a positive electrode active coating on the positive electrode sheet, and the lithium battery positive electrode material present in the positive electrode active coating.

[0145] This disclosure also provides a lithium battery, including the above-mentioned positive electrode, and may also include a negative electrode, electrolyte, separator, etc., to form a complete battery structure with good cycle performance.

[0146] Specifically, the types of negative electrode, electrolyte, and separator are not limited. During the charging and discharging process of a secondary battery, active ions are inserted and removed back and forth between the positive and negative electrode, while the electrolyte plays the role of conducting ions between the positive and negative electrode.

[0147] In other embodiments, it may not be in the form of a secondary battery, but may be in the form of a battery module, battery pack, etc.

[0148] This disclosure provides an apparatus including the aforementioned secondary battery, battery module, or battery pack. The secondary battery, battery module, or battery pack can serve as a power source for the apparatus or as an energy storage unit. This apparatus can be, but is not limited to, mobile devices (e.g., mobile phones, laptops), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0149] The features and performance of this disclosure will be further described in detail below with reference to embodiments.

[0150] This disclosure provides cathode materials as shown in Tables 1 and 2, and evaluates the crack resistance of said cathode materials; further, its cycle performance and electrochemical performance are tested, and the results are listed in Table 3. The methods for characterizing and testing the cathode materials prepared in the examples and comparative examples are as follows:

[0151] (1) The overall and cross-sectional microstructure of the material was observed using a JEOL JSM-6490LV scanning electron microscope. To obtain a complete cross-sectional morphology of the sample, the sample was cut using a focused ion beam method. Porosity analysis was performed on the ion-cut profile. The porosity analysis method is as follows: the porosity of the ion-cut profile was measured using NanoMeasurer software.

[0152] (2) The active material was coated onto an ultrathin aluminum foil and assembled into a mold battery with a beryllium window. In-situ XRD testing was then performed on an EMPYREAN XRD diffractometer. During the test, the battery underwent charge-discharge cycles at a current density of 0.1C. The 2θ range of the X-ray scan was 10–60°, and each scan cycle was 600 s. The values ​​of cell parameters c and a were recorded during charging at 3–4.5V, and the values ​​of cell parameters c and a after 10 cycles. The values ​​were then calculated. and

[0153] (3) Particle size: The MS3000 laser particle size analyzer was used for testing.

[0154] (4) Tap density TD: The tap density of powder products shall be determined in accordance with GB / T 21354-2008.

[0155] (5) BET Specific Surface Area: The specific surface area of ​​the material was obtained by analyzing the nitrogen adsorption-desorption curve data in the low-to-medium pressure stage using the BET formula. The test was conducted on an Autosorb IQ2 fully automated specific surface area and pore size analyzer manufactured by Antonpax Instruments GmbH, Austria. The BET (denoted as BET) of the cathode material during the first charge was measured and calculated separately.0 ) and the BET (denoted as BET) after 100 charge-discharge cycles of the positive electrode material. t The sampling method after cycling is as follows: After cycling, the battery is flexibly disassembled, the electrode is removed, the electrode is immersed in DMSO and stirred until the electrode powder is completely removed. The electrode powder is rinsed with ethanol 5 times and dried at 60°C to constant weight. The carbon material and positive electrode material in the electrode powder are separated by a magnetic separator. The separated positive electrode material is the sample to be tested.

[0156] (6) Chemical composition analysis was performed using a PE Avio200 inductively coupled plasma optical emission spectrometer (ICP-OES).

[0157] (7) The samples were characterized using a FEI Titan Cubed G2 60-300 transmission electron microscope. First, selected area electron diffraction (SAED) was used to obtain local diffraction patterns to determine the crystal structure. Then, high-resolution atomic arrangement images were obtained using high-angle annular dark-field imaging (HAADF-STEM) mode, and the elemental distribution of the material was qualitatively and quantitatively analyzed using an EDS detector.

[0158] (8) Crushing strength determination: The prepared powder was dispersed in NMP by ultrasonic treatment. The resulting dispersion was dropped onto a smooth silicon wafer of 2cm*2cm and dried under a heating lamp to obtain a well-dispersed sample. The sample was observed under an optical microscope, and particles with a spacing of more than 100μm on the silicon wafer were selected. Using a planar indentation head with a diameter of 100μm, the marked particles were indented on a CSM UNHT nanoindenter to obtain the pressure-displacement relationship curve. In the real-time monitoring of the indentation experiment, the particle was judged to have been crushed when the pressure suddenly dropped. The crushing strength (St) of the particle was calculated according to formula (1) based on the maximum pressure P before the pressure suddenly dropped. n particles were taken for each sample for testing, and the average crushing strength was calculated according to formula (2).

[0159] St=2.8×P / (πd 2 ) formula (1);

[0160] In the formula, St represents the crushing strength in MPa; P represents the maximum pressure value before the pressure drop point in mN; and d represents the particle diameter of the lithium battery cathode material in μm. The average crushing intensity is represented by n, which is the sample size. In the specific implementation of this disclosure, n = 10.

[0161] (9) Electrochemical performance: Rate performance was tested using the LANHE CT2001A battery testing system.

[0162] Electrode preparation method: Ternary cathode material, conductive carbon black, and PVDF were weighed at a mass ratio of 8:1:1, thoroughly ground, and placed in a bottle. An appropriate amount of NMP solvent was added, and the mixture was stirred for 24 hours to form a homogeneous slurry. The slurry was then uniformly coated onto a clean aluminum foil using a wet film preparation device, with the loading controlled at 2.5 ± 0.05 mg / cm³. 2 Then, it is placed in a vacuum drying oven at 100℃ for 24 hours to dry until no material adheres. Then, the electrode sheet is placed on a hydraulic press and rolled with a pressure of 6MPa.

[0163] Button battery assembly: The positive electrode sheet is further punched into a circular electrode sheet with a diameter of 12mm. Then, a lithium metal disc is used as the negative electrode, Celgard2300 is used as the separator, and 1M LiPF6 solution (the solvent is a mixed solution of EMC, DC and DMC with a volume ratio of 1:1:1) is used as the electrolyte to assemble a CR2032 type button battery.

[0164] The particle size D50, TD, BET, crushing strength and other parameters obtained by the examples and comparative examples are shown in Tables 1, 2 and 3, and the crack resistance is calculated as shown in Table 2.

[0165] Table 1. Chemical formula, D50, and TD test results of cathode materials.

[0166] [Corrected according to Rule 91, March 24, 2026] Table 2: Cathode materials provided in each embodiment and comparative example

[0167] Table 3. Cyclic performance and electrochemical performance test results for each example and comparative example.

[0168] As can be seen from the data in Tables 1, 2, and 3, the greater the crack resistance of the cathode material, the higher the specific surface area change rate (BET). t / BET 0 The smaller the value, the greater the crack resistance of the material, the stronger its ability to resist microcrack formation during charge-discharge cycles, and the better its cycle stability. The crack resistance of the comparative example exceeds the range defined in this application, resulting in a significant decrease in cycle performance.

[0169] Example 1

[0170] This embodiment provides a lithium battery cathode material (LiN). i0.761 Co 0.11 Mn 0.123 Ti 0.006 The preparation method of O2, corresponding to the product of Example 1 above, includes the following steps:

[0171] (1) Preparation of precursor kernel

[0172] Metal sulfates were weighed and dissolved in deionized water at a nickel-cobalt-manganese molar ratio of 8:1:1 to form a metal salt solution with a total metal ion molar concentration of 2M. 70% by volume of a co-precipitation base solution with an ammonia concentration of 5 g / L and a pH of 12 ± 0.2 was added to the reactor. Nitrogen gas was introduced, and the metal salt solution, precipitant sodium hydroxide solution (30 wt%), and complexing agent ammonia solution (20 wt%) were simultaneously added to the reactor via a feed pump. The temperature was raised to 85℃, and the co-precipitation reaction was carried out with stirring at 600 rpm. During the reaction, the ammonia flow rate was adjusted to stabilize the ammonia concentration at 4 g / L, the sodium hydroxide flow rate was adjusted to stabilize the reaction pH at 11, and the metal salt solution flow rate was adjusted to 450 L / h. The reaction conditions were maintained until the D50 particle size reached 8 μm, at which point the feed was stopped, and the mixture was aged for 12 h. After aging, the slurry was washed with 60 g / L NaOH solution at 80°C to remove sodium and sulfur residues, then rinsed with pure water at 80°C, dried at 120°C for 12 h, and sieved to obtain the ternary precursor core (porosity 8.44%).

[0173] (2) Preparation of reinforced precursor

[0174] Prepare a strengthening solution, which is an aqueous solution containing 2 wt% manganese acetate, 0.15 wt% lithium hydroxide, and 1.5 wt% starch, with a viscosity of 6.5 mPa·s.

[0175] The precursor core obtained in step (1) was added to the reinforcement solution at a solid-liquid ratio of 1 g: 100 mL. After sonication for 30 min, a reaction solution was obtained. The reaction solution was placed in a high-pressure reactor, and the solvent was vaporized by heating to pressurize the reaction solution. The heating temperature was controlled at 100–110 °C, and the pressure was controlled at 15 MPa to ensure that the precursor core was completely wetted. After holding the pressure for 30 min, the reaction solution was filtered. The filtered solid material was dried at 100 °C for 8 h, and then calcined at 650 °C for 6 h. After cooling, the reinforced precursor core was obtained.

[0176] (3) Preparation of ternary precursors with core-shell structure

[0177] Nickel-cobalt-manganese sulfate and titanium disulfate were dissolved in deionized water, and acid was added to adjust the pH to 4 to form a metal salt solution. The molar ratio of nickel, cobalt, and manganese in the nickel, cobalt, and manganese salts in the metal salt solution was 50:30:20. The molar concentration of the first dopant compound was 0.11 M, and the total molar concentration of nickel, cobalt, and manganese ions in the metal salt solution was 2 M. The ratio of the total molar amount of nickel, cobalt, and manganese in the core of the reinforced precursor prepared in step (2) to the total molar amount of nickel, cobalt, and manganese in the metal salt solution was 8:1.

[0178] Add 20% volume of deionized water to the reactor and purge with nitrogen. Add the core of the reinforced precursor obtained in step (2). With stirring, slowly add the metal salt solution to the reactor at a rate of 150 L / h using a peristaltic pump. Adjust the pH of the reaction solution to 11 ± 0.2 with sodium hydroxide solution and ammonia water. The ammonia concentration is 5 g / L. After the addition is complete, react for 1 h. Filter the solution and rinse with pure water at 80 °C. Dry at 120 °C for 12 h to obtain a ternary precursor with a core-shell structure.

[0179] (4) Preparation of ternary cathode materials

[0180] The ternary precursor obtained in step (3) is mixed and ground with lithium hydroxide, and then calcined to obtain the ternary cathode material with the chemical formula LiN. i0.761 Co 0.11 Mn 0.123 Ti 0.006 O2. The ternary precursor and lithium source were fed at a Li / (Ni+Co+Mn) molar ratio of 1.05. Calcination conditions: oxygen environment, heating to 450℃ at 1℃ / min and holding for 4h, then heating to 800℃ at 2℃ / min and holding for 12h.

[0181] Example 2

[0182] The difference from Example 1 is that step (1) is as follows:

[0183] Metal sulfates were weighed and dissolved in deionized water at a nickel-cobalt-manganese molar ratio of 8:1:1 to form a metal salt solution with a total metal ion molar concentration of 2M. 60% by volume of a co-precipitation base solution with an ammonia concentration of 5.5 g / L and a pH of 12 ± 0.2 was added to the reactor. Nitrogen gas was introduced, and the metal salt solution, precipitant sodium hydroxide solution (30 wt%), and complexing agent ammonia solution (20 wt%) were simultaneously added to the reactor via a feed pump. The temperature was raised to 75°C, and the co-precipitation reaction was carried out with stirring at 800 rpm. During the reaction, the flow rate of ammonia was adjusted to stabilize the ammonia concentration at 7 g / L, the flow rate of sodium hydroxide solution was adjusted to stabilize the reaction pH at 11, and the flow rate of the metal salt solution was adjusted to 450 L / h. The reaction conditions were maintained until the D50 particle size reached 8 μm, at which point the feed was stopped, and the mixture was aged for 12 h. After aging, the slurry was washed with 60 g / L NaOH solution at 80°C to remove sodium and sulfur residues, then rinsed with pure water at 80°C, dried at 120°C for 12 h, and sieved to obtain the ternary precursor core (porosity 4.13%).

[0184] Example 3

[0185] The difference from Example 1 is that step (1) is as follows:

[0186] Metal sulfates were weighed and dissolved in deionized water at a nickel-cobalt-manganese molar ratio of 8:1:1 to form a metal salt solution with a total metal ion molar concentration of 2M. 80% of the volume of co-precipitation base solution was added to the reactor. The ammonia concentration of the base solution was 4.5 g / L, and the pH was 12 ± 0.2. Nitrogen gas was introduced. The metal salt solution, precipitant sodium hydroxide solution (30 wt%), and complexing agent ammonia solution (20 wt%) were simultaneously added to the reactor via a feed pump. The temperature was raised to 95℃, and the co-precipitation reaction was carried out with stirring at 800 rpm. During the reaction, the flow rate of ammonia was adjusted to stabilize the ammonia concentration at 3 g / L, the flow rate of sodium hydroxide solution was adjusted to stabilize the reaction pH at 11, and the flow rate of the metal salt solution was adjusted to 450 L / h. The reaction conditions were maintained until the D50 particle size reached 8 μm. Feeding was then stopped, and the mixture was aged for 12 h. After aging, the slurry was washed with 60 g / L NaOH solution at 80°C to remove sodium and sulfur residues, then rinsed with pure water at 80°C, dried at 120°C for 12 h, and sieved to obtain the ternary precursor core (porosity 11.85%).

[0187] Example 4

[0188] The only difference from Example 1 is that some conditions in steps (2) to (4) are different, as follows:

[0189] In step (2): the strengthening solution is an aqueous solution containing 2 wt% aluminum isopropoxide and 0.24 wt% lithium hydroxide, with a viscosity of 5.8 mPa·s. The solid-liquid ratio of the precursor core to the strengthening solution is 1 g: 100 mL. Drying is carried out at 100℃ for 8 h, and calcination is carried out at 600℃ for 5 h.

[0190] In step (3): Nickel, cobalt, and manganese sulfates and magnesium sulfate are dissolved in deionized water, and acid is added to adjust the pH to 4 to form a metal salt solution. The molar ratio of nickel, cobalt, and manganese in the nickel, cobalt, and manganese salts in the metal salt solution is 60:20:20; the concentration of magnesium sulfate is 0.018M, and the total molar concentration of nickel, cobalt, and manganese ions in the metal salt solution is 2M. The ratio of the total molar amount of nickel, cobalt, and manganese in the core of the reinforced precursor to the total molar amount of nickel, cobalt, and manganese in the metal salt solution is 8:1. Add 20% volume of deionized water to the reactor and purge with nitrogen. Add the core of the reinforced precursor obtained in step (2). With stirring, slowly add the metal salt solution to the reactor at a rate of 100 L / h using a peristaltic pump. Adjust the pH of the reaction solution to 11 ± 0.2 with sodium hydroxide solution and ammonia water. The ammonia concentration is 3 g / L. After the addition is complete, react for 1 h. Filter the solution and rinse with pure water at 80 °C. Dry at 120 °C for 12 h to obtain a ternary precursor with a core-shell structure.

[0191] In step (4): the ternary precursor and lithium source are fed in a Li / (Ni+Co+Mn) molar ratio of 1.05. Calcination conditions: oxygen environment, heating to 500℃ at 1℃ / min and holding for 4h, then heating to 750℃ at 2℃ / min and holding for 12h.

[0192] Example 5

[0193] The only difference from Example 1 is that some conditions in steps (2) to (4) are different, as follows:

[0194] In step (2): the strengthening solution is an aqueous solution containing 2 wt% cobalt acetate, 0.75 wt% lithium acetate, 1.1 wt% phosphoric acid, and 1.8 wt% carbomer 940, with a viscosity of 7.4 mPa·s. The solid-liquid ratio of the precursor core to the strengthening solution is 1 g: 100 mL. Drying is carried out at 100 °C for 8 h, and calcination is carried out at 700 °C for 10 h.

[0195] In step (3): Nickel-cobalt-manganese sulfate and zirconium acetate are dissolved in deionized water and acid is added to adjust the pH to 5 to form a metal salt solution. The molar ratio of nickel, cobalt, and manganese in the nickel, cobalt, and manganese salts in the metal salt solution is 60:20:20; the concentration of zirconium acetate is 0.04M, and the total molar concentration of nickel, cobalt, and manganese ions in the metal salt solution is 2M. The ratio of the total molar amount of nickel, cobalt, and manganese in the core of the reinforced precursor to the total molar amount of nickel, cobalt, and manganese in the metal salt solution is 4:1. 20% volume of deionized water is added to the reactor, nitrogen gas is introduced, and the core of the reinforced precursor obtained in step (2) is added. The metal salt solution is slowly dripped into the reactor at a rate of 150L / h using a peristaltic pump while stirring. The pH of the reaction solution is adjusted to 11±0.2 with sodium hydroxide solution and ammonia water, and the ammonia concentration is 5g / L. After the dripping is completed, the reaction is carried out for 1h. The mixture is then filtered, rinsed with pure water at 80℃, and dried at 120℃ for 12h to obtain a ternary precursor with a core-shell structure.

[0196] In step (4): the ternary precursor and lithium source are fed in a Li / (Ni+Co+Mn) molar ratio of 1.05. Calcination conditions: oxygen environment, heating to 500℃ at 1℃ / min and holding for 4h, then heating to 850℃ at 2℃ / min and holding for 12h.

[0197] Example 6

[0198] The only difference from Example 1 is that some conditions in steps (2) to (4) are different, as follows:

[0199] In step (2): the strengthening solution is an aqueous solution containing 2 wt% aluminum isopropoxide and 0.24 wt% lithium hydroxide, with a viscosity of 5.8 mPa·s. The solid-liquid ratio of the precursor core to the strengthening solution is 1 g: 100 mL. Drying is carried out at 100 °C for 8 h, and calcination is carried out at 700 °C for 10 h.

[0200] In step (3): Nickel-cobalt-manganese sulfate and titanium disulfate are dissolved in deionized water, and acid is added to adjust the pH to 4 to form a metal salt solution. The molar ratio of nickel, cobalt, and manganese in the nickel, cobalt, and manganese salts in the metal salt solution is 33:33:34; the concentration of titanium disulfate is 0.1M, and the total molar concentration of nickel, cobalt, and manganese ions in the metal salt solution is 2M. The ratio of the total molar amount of nickel, cobalt, and manganese in the core of the reinforced precursor to the total molar amount of nickel, cobalt, and manganese in the metal salt solution is 12:1. Add 20% volume of deionized water to the reactor and purge with nitrogen. Add the core of the reinforced precursor obtained in step (2). With stirring, slowly add the metal salt solution to the reactor at a rate of 200 L / h using a peristaltic pump. Adjust the pH of the reaction solution to 11 ± 0.2 with sodium hydroxide solution and ammonia water. The ammonia concentration is 7 g / L. After the addition is complete, react for 1 h. Filter the solution and rinse with pure water at 80 °C. Dry at 120 °C for 12 h to obtain a ternary precursor with a core-shell structure.

[0201] (4) The ternary precursor and lithium source were fed at a Li / (Ni+Co+Mn) molar ratio of 1.05, and the doping amount of boron in boron oxide was 0.2%. Calcination conditions: oxygen environment, heating to 500℃ at 1℃ / min and holding for 4h, then heating to 850℃ at 2℃ / min and holding for 12h.

[0202] Example 7

[0203] The only difference from Example 1 is that in step (2), the strengthening solution is an aqueous solution containing 2 wt% aluminum isopropoxide, 0.24 wt% lithium hydroxide, and 0.62 wt% starch, and the viscosity of the strengthening solution is 6.5 mPa·s.

[0204] Example 8

[0205] The only difference from Example 1 is that in step (2), the strengthening solution is an aqueous solution containing 2 wt% cobalt acetate, 0.75 wt% lithium acetate, 1.1 wt% phosphoric acid, and 0.79 wt% starch, and the viscosity of the strengthening solution is 6.5 mPa·s.

[0206] Example 9

[0207] The only difference from Example 1 is that in step (2), the strengthening solution is an aqueous solution containing 2 wt% manganese acetate and 0.15 wt% lithium hydroxide, and the viscosity of the strengthening solution is 1.62 mPa·s.

[0208] Example 10

[0209] The only difference from Example 1 is that in step (2), the strengthening solution is an aqueous solution containing 2 wt% manganese acetate, 0.15 wt% lithium hydroxide, and 2.12 wt% starch, and the viscosity of the strengthening solution is 7.92 mPa·s.

[0210] Comparative Example 1 (porosity less than 4%)

[0211] The difference from Example 1 is that step (1) is as follows:

[0212] Metal sulfates were weighed and dissolved in deionized water at a nickel-cobalt-manganese molar ratio of 8:1:1 to form a metal salt solution with a total metal ion molar concentration of 2M. 50% by volume of a co-precipitation base solution with an ammonia concentration of 4 g / L and a pH of 11.5 ± 0.2 was added to the reactor. Nitrogen gas was introduced, and the metal salt solution, precipitant sodium hydroxide solution (30 wt%), and complexing agent ammonia solution (20 wt%) were simultaneously added to the reactor via a feed pump. The temperature was raised to 85℃, and the co-precipitation reaction was carried out with stirring at 600 rpm. During the reaction, the flow rate of ammonia was adjusted to stabilize the ammonia concentration at 3 g / L, the flow rate of sodium hydroxide solution was adjusted to stabilize the reaction pH at 10, and the flow rate of the metal salt solution was adjusted to 450 L / h. The reaction conditions were maintained until the D50 particle size reached 8 μm, at which point the feed was stopped, and the mixture was aged for 12 h. After aging, the slurry was washed with 60 g / L NaOH solution at 80°C to remove sodium and sulfur residues, then rinsed with pure water at 80°C, dried at 120°C for 12 h, and sieved to obtain the ternary precursor core (porosity 2.2%).

[0213] Comparative Example 2 (primary particles are granular)

[0214] The difference from Example 1 is that step (1) is as follows:

[0215] Metal sulfates were weighed and dissolved in deionized water at a nickel-cobalt-manganese molar ratio of 8:1:1 to form a metal salt solution with a total metal ion molar concentration of 2M. 50% by volume of a co-precipitation base solution with an ammonia concentration of 5 g / L and a pH of 12 ± 0.2 was added to the reactor. Nitrogen gas was introduced, and the metal salt solution, a precipitant sodium hydroxide solution (30 wt%), and a complexing agent ammonia solution (20 wt%) were simultaneously added to the reactor via a feed pump. The temperature was raised to 50°C, and the co-precipitation reaction was carried out with stirring at 300 rpm. During the reaction, the flow rate of the ammonia solution was adjusted to stabilize the ammonia concentration at 6 g / L, the flow rate of the sodium hydroxide solution was adjusted to stabilize the reaction pH at 11, and the flow rate of the metal salt solution was adjusted to 500 L / h. The reaction conditions were maintained until the D50 particle size reached 8 μm, at which point the feed was stopped, and the mixture was aged for 12 h. After aging, the slurry was washed with 60 g / L NaOH solution at 80°C to remove sodium and sulfur residues, then rinsed with pure water at 80°C, dried at 120°C for 12 h, and sieved to obtain the ternary precursor core (porosity 6.7%).

[0216] Comparative Example 3 (without a precursor shell)

[0217] The difference from Example 1 is that step (3) is omitted, and step (4) is as follows:

[0218] The ternary precursor was mixed with lithium hydroxide and titanium oxide, ground, and then calcined to obtain the ternary cathode material. The ternary precursor and lithium source were fed at a Li / (Ni+Co+Mn) molar ratio of 1.05, and the Ti doping content in the titanium oxide was 0.2%. Calcination conditions: oxygen environment, heating to 450℃ at 1℃ / min and holding for 4h, then heating to 800℃ at 2℃ / min and holding for 12h.

[0219] Comparative Example 4 (without grain boundary reinforcement)

[0220] The only difference from Example 1 is that step (2) is not performed.

[0221] Results analysis:

[0222] The ion cross-sectional images of the cathode materials prepared in Example 1 and Comparative Example 1 are shown in Figures 1 and 2, respectively. The core-shell structure can be seen, and the porosity of Example 1 is higher.

[0223] Cross-sectional views of Example 1 and Comparative Example 2 are shown in Figures 3 and 4. It can be seen that the primary particles of Example 1 are radially radial, while the primary particles of Comparative Example 2 are granular.

[0224] The XRD patterns of the precursor core and precursor material prepared in Example 1 are shown in Figure 5. It can be seen that: consistent with the card, there are no impurities on the surface, and all samples have obvious splitting of the (006) peak, (012) peak, (018) peak and (110) peak, indicating that the surface samples have good layered structure.

[0225] The TEM and EDS images of the cathode materials prepared in Examples 1 and 4 are shown in Figures 6 and 7. It can be seen that Mn or Al elements are enriched at the grain boundaries of the primary particles, indicating that the reinforcing agent is successfully distributed near the grain boundaries and reinforces the primary particles.

[0226] The above are merely preferred embodiments of this disclosure and are not intended to limit this disclosure. Various modifications and variations can be made to this disclosure by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the scope of protection of this disclosure. Industrial applicability

[0227] This disclosure evaluates the ability of polycrystalline cathode materials to resist internal crack formation during cycling by constructing a formula for calculating crack resistance strength. It comprehensively considers the influence of unit cells and grain boundaries to ensure that the crack resistance strength meets a specific range. Cathode materials with crack resistance strength meeting this specific range possess high-strength crystals and grain boundaries, which improves the material's structural stability, effectively inhibits the propagation of internal cracks to the interface, and thus improves the material's cycle stability and lifespan. The instruments used to measure each parameter in the crack resistance strength expression are all commonly used testing instruments, which are convenient to operate and easy to apply industrially.

Claims

1. [Corrected according to Rule 91, March 24, 2026] A lithium-ion battery cathode material, characterized in that, The crack resistance of the lithium battery cathode material is 4-15 MPa; in, In the formula, St represents the crushing strength, which is obtained through an indentation test and is measured in MPa. This represents the average crushing strength, expressed in MPa. n is the sample size, n≥10; This refers to the maximum change in shear strain during the initial charging process; It refers to the change in shear strain after 10 charge-discharge cycles, t=10; This refers to the shear strain measured under static conditions after 10 charge-discharge cycles. This refers to the shear strain measured under static conditions before the first charge; a and c represent the unit cell parameters.

2. The lithium-ion battery cathode material according to claim 1, characterized in that, The crack resistance of the lithium-ion battery cathode material is 6-15 MPa; St = 2.8 × P / (πd 2 ); P represents the maximum pressure value before the pressure drop point in the indentation test, in mN; d represents the particle diameter of the lithium battery cathode material, in μm; The value ranges from 0.2 to 0.

3. The value of is 0.01-0.20, and the value of St is 90-140 MPa; c and a were obtained by X-ray diffraction (XRD).

3. The lithium-ion battery cathode material according to claim 1 or 2, characterized in that, The general formula of the lithium battery cathode material is Li x Ni a Co b M c M' 1-a-b-c A y O 2-y ; In the general formula, M is selected from at least one of Al and Mn; M' is selected from at least one of Zr, Sr, Mo, Ba, W, B, Ti, Mg, Li, Si, Ca, Cu, La, Ce, Bi, In, Al, Nb, and Y; A is selected from at least one of P and F; 0.95≤x<1.1, a>0, b>0, c>0, 0.95≤(a+b+c)≤1, 0≤y≤0.

01.

4. A method for preparing a lithium-ion battery cathode material according to any one of claims 1-3, characterized in that, include: Prepare lithium-ion battery cathode materials that meet the requirements for crack resistance strength.

5. The preparation method according to claim 4, characterized in that, include: The precursor core was prepared by co-precipitation reaction of nickel salt, cobalt salt and M salt; The precursor core is mixed with a strengthening solution and reacted, and then calcined to obtain a strengthened precursor core; wherein, the raw materials in the strengthening solution are calcined to obtain a strengthening agent; the strengthening agent is selected from at least one of LiAlO2, LiMn2O4 and LiCoPO4; A co-precipitation reaction is carried out using nickel salt, cobalt salt, M salt, and a first doping element compound to grow a shell on the basis of the reinforced precursor core, thereby obtaining a ternary precursor with a core-shell structure; wherein the doping element contained in the first doping element compound is selected from at least one of Ti, Al, Zr, and Mg. The ternary precursor is mixed with a lithium source and calcined; or, the ternary precursor, the second doping element compound, and the lithium source are mixed and calcined; the doping element contained in the second doping element compound is selected from at least one of Zr, Sr, Mo, Ba, W, B, Ti, Mg, Li, F, Si, Ca, Cu, La, P, Ce, Bi, In, Nb, and Y.

6. The preparation method according to claim 5, characterized in that, The primary particles in the precursor core are arranged radially in a radial pattern, and the porosity is 4%-12%.

7. The preparation method according to claim 5 or 6, characterized in that, The preparation process of the precursor core includes: preparing a base liquid in a reaction vessel, and passing a first mixed metal salt solution, a first precipitant solution, and a first complexing agent solution into the base liquid to carry out a co-precipitation reaction. The process of preparing the precursor core satisfies at least one of features A1-E1: Feature A1: The reaction temperature of the coprecipitation reaction is controlled at 75℃-95℃; Feature B1: The reaction pH for controlling the coprecipitation reaction is 10.5-11.5; Feature C1: Stop feeding after the particle size D50 reaches 2-17μm; Feature D1: The coprecipitation reaction is carried out under an inert atmosphere, and the rotation speed is 400 rpm-800 rpm during the reaction. Feature E1: After the co-precipitation reaction is completed, the product is aged, followed by alkali washing, water washing, and drying.

8. The preparation method according to claim 7, characterized in that, The process of preparing the precursor kernel satisfies at least one of the following features: F1-K1: Feature F1: The first complexing agent solution is an ammonia solution with a mass fraction of 18%-22%, and the ammonia concentration in the reaction vessel is controlled at 3g / L-7g / L during the precipitation process; Feature G1: The total molar concentration of metal ions in the first mixed metal salt solution is 1.8M-2.2M, and the flow rate of the first mixed metal salt solution is 400L / h-500L / h; Feature H1: The molar ratio of nickel, cobalt and M in the first mixed metal salt solution is (35-98):(1-35):(1-35); Feature I1: The salt in the first mixed metal salt solution is selected from any one of nitrates, chlorides, and sulfates; Feature J1: The first precipitant solution is a sodium hydroxide solution with a mass fraction of 30%-34%; Feature K1: The concentration of ammonia in the bottom solution is 4.5 g / L-5.5 g / L, and the pH value is 11.8-12.

2.

9. The preparation method according to any one of claims 5-8, characterized in that, The preparation process of the reinforced precursor core includes: mixing the precursor core with the reinforcement solution and then sonicating it, reacting it for 10 min to 60 min at a temperature of 100℃-150℃ and a pressure of 10MPa-20MPa, followed by solid-liquid separation, and calcining the obtained solid material.

10. The preparation method according to claim 9, characterized in that, The preparation process of the reinforced precursor core satisfies at least one of the following characteristics: A2-F2: Feature A2: The strengthening solution also contains a thickener, and the viscosity of the strengthening solution is adjusted to 5 mPa·s-8 mPa·s by controlling the amount of the thickener. Feature B2: When feature A2 is satisfied, the thickener is selected from at least one of carbomer, xanthan gum, gelatin and starch; Feature C2: 1g of the precursor core corresponds to 90mL-110mL of the reinforcement solution; Feature D2: Control the ultrasound time to 10 min-60 min; Feature E2: The calcination temperature is controlled at 600℃-700℃, and the calcination time is 3h-8h; Feature F2: The solid material is first dried at 80℃-120℃ for 5h-10h, and then calcined.

11. The preparation method according to any one of claims 5-10, characterized in that, The preparation process of the ternary precursor with a core-shell structure includes: adding the core of the reinforced precursor to the bottom liquid in the reaction vessel, and introducing the second mixed metal salt solution, the second precipitant solution and the second complexing agent solution into the reaction vessel to carry out a co-precipitation reaction; The second mixed metal salt solution contains nickel salt, cobalt salt, M salt and a first doping element compound. By controlling the addition rate of the second mixed metal salt solution, the addition rate of nickel, cobalt and M elements during the reaction process is controlled to be less than the addition rate when preparing the precursor core.

12. The preparation method according to claim 11, characterized in that, The preparation process of the ternary precursor with a core-shell structure satisfies at least one of the following features: A3-I3: Feature A3: The total molar concentration of nickel, cobalt and M elements in the second mixed metal salt solution is 1.8M-2.2M, the flow rate of the second mixed metal salt solution is 100L / h-200L / h, and the pH value of the second mixed metal salt solution is adjusted to 2-5; Feature B3: The total molar amount of metal is calculated based on the total molar amount of nickel, cobalt and M elements, and the ratio of the total molar amount of metal in the core of the reinforced precursor to the total molar amount of metal in the second mixed metal salt solution is (4-12):1; Feature C3: In the second mixed metal salt solution, the molar ratio of nickel, cobalt and M is (30-60):(20-35):(20-35); Characteristic D3: The reaction temperature for the coprecipitation reaction is 75℃-95℃, and the reaction pH is 10.8-11.2; Feature E3: The second complexing agent solution is an ammonia solution with a mass fraction of 18%-22%, and the ammonia concentration in the reaction vessel is controlled at 3g / L-7g / L during the precipitation process; Feature F3: The first dopant compound is selected from at least one of titanium disulfide, sodium aluminate, zirconium nitrate, zirconium acetate, zirconium sulfate, magnesium sulfate, and magnesium nitrate; Feature G3: The bottom liquid in the reactor is water, and the second precipitant solution is a sodium hydroxide solution with a mass fraction of 30%-40%; Feature H3: The coprecipitation reaction is carried out under an inert atmosphere, and the rotation speed is 300 rpm-500 rpm during the reaction. Feature I3: After the second mixed metal salt solution is added, the reaction continues for 0.5h-2.0h, followed by solid-liquid separation, and the obtained solid material is washed with water and dried.

13. The preparation method according to any one of claims 5-12, characterized in that, The process of mixing and calcining the ternary precursor, the second doped element compound, and the lithium source satisfies at least one of features A4-F4: Feature A4: The molar ratio of the total amount of nickel, cobalt and M elements in the ternary precursor to the lithium content in the lithium source is 1:(1.05-1.1); Feature B4: The lithium source is selected from lithium hydroxide; Feature C4: The second doping element compound is selected from at least one of oxides, fluorides, carbonates, hydroxides, nitrides, borides, and nitrates; Feature D4: During the calcination process, the first calcination is carried out at 400℃-500℃ for 2h-6h, followed by a second calcination at 750℃-850℃ for 10h-15h. Feature E4: Calcination is carried out in an oxygen-containing atmosphere; Feature F4: First, the ternary precursor, the second doped element compound, and the lithium source are mixed and ground, and then calcined.

14. A positive electrode plate, characterized in that, The lithium-ion battery cathode material includes any one of the lithium-ion battery cathode materials described in claims 1-3 or any one of the lithium-ion battery cathode materials prepared by the preparation method described in claims 4-13.

15. A lithium battery, characterized in that, Includes the positive electrode sheet as described in claim 14.

Images