Cathode material and preparation method thereof, cathode slurry and preparation method thereof, cathode sheet, lithium ion battery and electric device

Abstract

The application belongs to the technical field of batteries, and particularly relates to a positive electrode material and a preparation method thereof, a positive electrode slurry and a preparation method thereof, a positive electrode sheet, a lithium ion battery and an electric device. The positive electrode material comprises: first positive electrode material particles, including a lithium iron manganese phosphate material core and a bifunctional coating layer, and the bifunctional coating layer is coated on at least part of the surface of the core; second positive electrode material particles, including nickel-cobalt-manganese ternary material particles; the bifunctional coating layer contains a hindered amine light stabilizer, and the structure of the hindered amine light stabilizer is R1-L-R2, R1 is a hindered amine group; R2 is an anchoring group, which is coordinated with metal ions on the surface of the lithium iron manganese phosphate core, and the anchoring group is selected from at least one of a derivative group of a carboxyl group, a derivative group of a hydroxyl group, a derivative group of a phosphate group, a derivative group of an amino group and a derivative group of an acyl group; and L is a connecting carrier. The positive electrode material has excellent energy density, safety, rate performance and cycle performance.

Description

Technical Field

[0001] This application belongs to the field of battery technology, specifically relating to cathode materials and their preparation methods, cathode slurry and their preparation methods, cathode sheets, lithium-ion batteries and electrical devices. Background Technology

[0002] Ternary cathode materials (NCM) offer high energy density and excellent rate performance, but suffer from poor thermal stability and safety, and are costly. Lithium manganese iron phosphate (LMFP) cathode materials, while possessing excellent safety, cycle life, and a high voltage platform, suffer from low ionic conductivity and poor rate and low-temperature performance. To combine their respective advantages, related technologies have attempted to use ternary cathode materials in combination with LMFP cathode materials. However, due to the significant difference in conductivity between LMFP and NCM, traditional composite materials struggle to preferentially construct a highly efficient conductive network on the surface of the low-conductivity LMFP particles during the homogenization process, resulting in high overall internal resistance and poor rate performance of the cathode material. Therefore, further improvements to the cathode material are needed. Summary of the Invention

[0003] This application aims to at least partially address one of the technical problems in related technologies. To this end, this application proposes a positive electrode material and its preparation method, a positive electrode slurry and its preparation method, a positive electrode sheet, a lithium-ion battery, and an electrical device. This positive electrode material exhibits excellent energy density, safety, cycle performance, or rate performance.

[0004] A first aspect of this application provides a cathode material comprising: The first cathode material particle includes a lithium manganese iron phosphate core and a bifunctional coating layer, wherein the bifunctional coating layer coats at least a portion of the surface of the core. The second cathode material particles include nickel-cobalt-manganese ternary material particles. The bifunctional coating layer contains a hindered amine light stabilizer with the structure R1-L-R2, wherein R1 is a hindered amine group; R2 is an anchoring group that is connected to the metal ions on the surface of the lithium manganese iron phosphate core via a coordinate bond, and the anchoring group is selected from at least one of carboxyl derivatives, hydroxyl derivatives, phosphate ester derivatives, amino derivatives, and acyl derivatives; L is a linker.

[0005] This application combines hindered amine light stabilizer-coated lithium manganese iron phosphate (LMFP) with nickel-cobalt-manganese ternary material (NCM) to significantly improve battery cycle stability, rate performance, and lifespan. The hindered amine light stabilizer molecule contains hindered amine groups and anchoring groups: the hindered amine groups face the electrolyte, efficiently capturing oxygen and free radicals, interrupting the electrolyte chain reaction, inhibiting electrolyte decomposition, HF corrosion, and manganese dissolution, reducing internal resistance, and compensating for the rate drop of LMFP; the anchoring groups coordinate with metal ions on the LMFP surface, achieving strong anchoring and guiding the conductive agent to preferentially coat the LMFP, improving its electronic conductivity; in addition, the anchoring groups can simultaneously coordinate with metal ions on the surfaces of both LMFP and NCM, enhancing the binding force between the two, guiding the conductive agent to accumulate at the interface, and inhibiting volume expansion. After compounding, LMFP provides safety and long cycle life, while NCM provides high energy density and rate performance, achieving the optimal balance of overall battery electrochemical performance.

[0006] According to embodiments of this application, the lithium manganese iron phosphate material core comprises the compound shown in Formula 1: Li m Mn x Fe y M 1-x-y PO4 Formula 1 In Formula 1, 0.9≤m≤1.1, 0.3≤x≤0.9, 0≤y≤0.8, and M is selected from at least one of Zn, Al, Na, K, Mg, Nb, Mo, and W; The nickel-cobalt-manganese ternary material particles include the compound shown in Formula 2: Li 1+n Ni a Co b Mn c Q d O2 type 2 In Equation 2, 0≤n≤0.3, 0.3≤a≤0.9, 0.1≤b≤0.3, 0.1≤c<0.3, 0≤d≤0.1, and a+b+c+d=1; Q is selected from at least one of B, Na, K, Mg, Al, Ca, Ti, Fe, Zn, Sr, Y, Zr, Nb, Mo, Sn, Ba, Ta, and W.

[0007] According to embodiments of this application, the above-mentioned positive electrode material satisfies at least one of the following conditions: The linker L is selected from triazine rings, benzene rings, and C2-C4 rings. 12 Any one of the alkylene chains; The anchoring group R2 is selected from at least one of methylene diphosphonic acid, vinyl triphosphonic acid, succinic acid diacyl, arylphosphonic acid, citrate tricarboxylic acid, isonicotinic acid acyl, 3-aminopropyltriethoxysilane-carboxyl hybrid group, and pentaerythritol tetrahydroxy. The mass ratio of the bifunctional coating layer to the lithium manganese iron phosphate core is 0.1:99.9~2:98, specifically 0.3:99.7~1.5:98.5; The mass ratio of the first positive electrode material particle to the second positive electrode material particle is 2~9:1, specifically 3~7:1.

[0008] According to embodiments of this application, the hindered amine light stabilizer comprises at least one of the following compounds: Formula 3-1 Formula 3-2 Formula 3-3 Equation 3-4; In Equation 3-1, n is between 0 and 8.

[0009] The hindered amine light stabilizer used in this application is a bifunctional hindered amine light stabilizer, that is, it uses a carrier to link different types of functional groups (such as hindered amine groups and anchoring groups) together, so that it plays a synergistic role in capturing oxygen free radicals, and its performance is superior to that of single-functional group stabilizers. The above-mentioned bifunctional coating layer can not only capture free radicals and inhibit manganese dissolution, but also, as an organic coating layer, has anchoring groups, which have better compatibility with the PVDF binder and NMP solvent system used subsequently. Thus, it effectively maintains the integrity of the coating layer during the homogenization process and improves the dispersion stability of the slurry.

[0010] According to embodiments of this application, the above-mentioned positive electrode material satisfies at least one of the following conditions: D of the first cathode material particles 50 The range is 0.05 µm to 10 µm, specifically 4 µm to 8 µm; D of the second cathode material particles 50 The range is 0.05 µm to 10 µm, specifically 4 µm to 8 µm.

[0011] A second aspect of this application provides a method for preparing the cathode material described in the first aspect, comprising: The lithium manganese iron phosphate material and the first solvent are mixed in the first mixture and heated to the first temperature to obtain the first mixture. The hindered amine light stabilizer and the second solvent are mixed a second time to obtain a second mixture; The first mixture and the second mixture are mixed and coated to obtain the first cathode material particles; The first cathode material particles and the second cathode material particles are mixed to obtain the cathode material.

[0012] This method enables the uniform mixing of the first and second cathode material particles, resulting in a cathode material with uniform and excellent performance. Furthermore, the process steps are simplified, the equipment requirements are lower, and the operation cycle is short and the cost is controllable.

[0013] According to an embodiment of this application, the mixed coating includes: mixing the first mixture and the second mixture at a rotation speed of 200 rpm to 4000 rpm and a temperature of 40°C to 100°C and drying them until the solvent evaporates to form the bifunctional coating layer.

[0014] According to embodiments of this application, the above method satisfies at least one of the following conditions: The first solvent and the second solvent each independently include at least one of ethanol, N-methylpyrrolidone, isopropanol, butyl acetate, N,N-dimethylformamide, tetrahydrofuran, toluene, dimethyl sulfoxide, cyclohexane, acetone and pyridine, preferably isopropanol; The mass ratio of the lithium manganese iron phosphate material to the first solvent is 1:3-5; The mass ratio of the hindered amine light stabilizer to the second solvent is 1:40-60; The first temperature is 25 ℃-100 ℃, specifically 75 ℃-85 ℃; The temperature of the second mixture is 50 ℃-100 ℃, specifically 89 ℃-91 ℃; The second mixing time is 20 min-50 min.

[0015] A third aspect of this application provides a positive electrode slurry, comprising: Organic solvents; Adhesive; Conductive agents, including zero-dimensional conductive agents and one-dimensional / two-dimensional conductive agents; And the positive electrode material as described in the first aspect, wherein, based on the total mass of the conductive agent, 60%-80% of the zero-dimensional conductive agent is distributed on the surface of the first positive electrode material particles in the positive electrode material.

[0016] According to embodiments of this application, the above-mentioned positive electrode slurry satisfies at least one of the following conditions: The adhesive includes PVDF; The conductive agent includes at least one of Super P, acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon fiber, preferably at least one of a mixture of Super P and carbon nanotubes or a mixture of Super P and graphene. The organic solvent includes N-methylpyrrolidone.

[0017] A fourth aspect of this application provides a method for preparing the positive electrode slurry described in the third aspect, comprising: The first positive electrode material particles, the first binder, the first conductive agent and the first organic solvent are mixed to obtain the first slurry; The first slurry, the second positive electrode material particles, the second binder, the second conductive agent, and the second organic solvent are mixed to obtain the positive electrode slurry; The mass ratio of the first conductive agent to the second conductive agent is not less than 1:1.

[0018] This method enables the first conductive agent to adhere as much as possible to the surface of the first positive electrode material particles, thereby forming a point-to-surface contact conductive network on the surface of the first positive electrode material particles. This conductive network improves the conductivity of the first positive electrode material particles, thus enhancing the conductivity of the positive electrode material. Simultaneously, the second conductive agent is dispersed in the gaps between the particles, working synergistically with the first slurry to form a surface conductive network and construct a complete electron transport path.

[0019] According to embodiments of this application, the above method satisfies at least one of the following conditions: The first conductive agent is a zero-dimensional conductive agent, selected from at least one of Super P, acetylene black, and Ketjen black; The second conductive agent is a one-dimensional / two-dimensional conductive agent, selected from at least one of carbon nanotubes, graphene, and carbon fibers; The first organic solvent and the second organic solvent each independently comprise N-methylpyrrolidone; The first adhesive and the second adhesive each independently include PVDF.

[0020] According to embodiments of this application, the above method satisfies at least one of the following conditions: Based on the total mass of the positive electrode slurry, the total mass percentage of the first binder and the second binder is 0.8%-2%; Based on the total mass of the first adhesive and the second adhesive, the mass percentage of the first adhesive is 50%-100%; Based on the total mass of the positive electrode slurry, the total mass percentage of the first conductive agent and the second conductive agent is 1.5% to 3.5%.

[0021] Based on the total mass of the first conductive agent and the second conductive agent, the mass percentage of the first conductive agent is 50%-90%, specifically 70%-80%.

[0022] A fifth aspect of this application provides a positive electrode sheet, comprising a positive current collector and a positive electrode coating layer disposed on at least one surface of the positive current collector, the positive electrode coating layer comprising the positive electrode material described in the first aspect, or comprising a coating formed after drying the positive electrode slurry described in the third aspect. All the features and advantages of this positive electrode sheet comprising the positive electrode material described in the first aspect or the coating formed after drying the positive electrode slurry described in the third aspect are not elaborated herein.

[0023] A sixth aspect of this application provides a lithium-ion battery comprising the positive electrode material described in the first aspect, a coating formed after drying the positive electrode slurry described in the third aspect, or the positive electrode sheet described in the fifth aspect. This lithium-ion battery exhibits excellent rate performance, capacity density, and cycle performance.

[0024] A seventh aspect of this application provides an electrical device, characterized in that it comprises the positive electrode material described in the first aspect, the coating formed after drying the positive electrode slurry described in the third aspect, the positive electrode sheet described in the fifth aspect, or the lithium-ion battery described in the sixth aspect. All the features and advantages of this electrical device, including the positive electrode material described in the first aspect, the coating formed after drying the positive electrode slurry described in the third aspect, the positive electrode sheet described in the fifth aspect, or the lithium-ion battery described in the sixth aspect, will not be elaborated upon here. Detailed Implementation

[0025] The embodiments of this application are described in detail below and are intended to explain this application, but should not be construed as limiting this application.

[0026] Ternary materials (such as NCM and NCA) possess high energy density and excellent rate performance, but their thermal stability and safety are relatively poor, their cycle life still needs improvement, and their material cost is high. Lithium iron phosphate (LFP) has significant advantages in high safety and long cycle life, but its energy density is relatively limited due to its low voltage plateau. By introducing Mn to partially replace Fe in LFP, lithium manganese iron phosphate (LMFP) can be obtained, which raises the voltage plateau to approximately 4.1V and theoretically increases the energy density by about 20% compared to LFP. However, LMFP has low intrinsic ionic conductivity, resulting in poor rate performance and low-temperature performance, and its compaction density is relatively low.

[0027] Based on the above, a single cathode material cannot simultaneously meet the diverse requirements of high energy density, high safety, long cycle life, and low cost. Therefore, current technologies combine ternary materials with lithium iron phosphate (LFP) materials to leverage their synergistic effects. However, simple physical mixing often presents the following problems: First, poor mixing uniformity of the two materials can easily lead to inconsistent battery performance; second, improper particle size matching makes it difficult to achieve close packing, affecting electrode compaction density and the construction of ion / electron transport channels; third, unreasonable conductive agent network design, due to the significant difference in conductivity between LMFP and NCM, traditional composite materials struggle to preferentially build an efficient conductive network on the surface of low-conductivity LMFP particles during homogenization, resulting in high overall internal resistance and poor rate performance of the cathode material, failing to simultaneously meet the differentiated conductivity requirements of the two materials; fourth, the lack of systematic optimization of the mixing ratio makes it difficult to achieve a synergistic improvement of "1+1>2" in key performance indicators.

[0028] In view of this, the first aspect of this application proposes a positive electrode material, comprising: The first cathode material particle includes a lithium manganese iron phosphate (LMFP) core and a bifunctional coating layer, wherein the bifunctional coating layer coats at least a portion of the surface of the core. The second cathode material particles include nickel-cobalt-manganese ternary material (NCM) particles. The bifunctional coating layer contains a hindered amine light stabilizer with the structure R1-L-R2, wherein R1 is a hindered amine group used to capture oxygen free radicals; R2 is an anchoring group selected from at least one of carboxyl derivatives, hydroxyl derivatives, phosphate derivatives, amino derivatives, and acyl derivatives, used to coordinate with metal ions on the surface of the lithium manganese iron phosphate core; and L is a linker.

[0029] This application achieves a comprehensive improvement in battery cycle stability, rate performance, and lifespan by compounding lithium manganese iron phosphate (LMFP) material coated with hindered amine light stabilizer with nickel-cobalt-manganese ternary material particles. Specifically, LMFP material itself has inherent advantages of high safety and long cycle life. Building upon this, this application further improves upon it by coating its surface with a hindered amine light stabilizer, achieving the following improvements: The hindered amine light stabilizer has hindered amine groups and anchoring groups. The hindered amine groups face the electrolyte side, effectively capturing oxygen and free radicals generated during battery charging and discharging from the decomposition of the positive electrode and electrolyte, simultaneously interrupting the electrolyte chain reaction, thereby inhibiting electrolyte decomposition, reducing side reactions, mitigating HF corrosion of the positive electrode material, inhibiting manganese dissolution, and effectively reducing internal resistance growth during cycling, thus compensating for the poor rate performance of LMFP. Simultaneously, the anchoring groups and metal ions (such as Mn) on the surface of LMFP particles... 2+Fe 2+ This coating layer forms coordination bonds to achieve chemical anchoring, allowing hindered amine light stabilizer molecules to adhere tightly to the LMFP surface and prevent detachment. Furthermore, the anchoring group can form π-π stacking or hydrogen bonding with the conductive agent, guiding the conductive agent to preferentially coat the LMFP surface, thereby significantly improving the electronic conductivity of the LMFP and compensating for its inherent poor conductivity. In addition, the anchoring group can simultaneously coordinate with metal ions on both the LMFP and NCM surfaces, enhancing the bonding force between the two phases. This structure also guides the conductive agent to preferentially exist on the LMFP surface and accumulate at the LMFP / NCM interface, resulting in tighter particle contact and suppressing volume expansion during cycling. The introduction of this coating layer significantly improves the battery's cycle stability and lifespan. Simultaneously, the nickel-cobalt-manganese ternary material particles possess high energy density and excellent rate performance, further effectively compensating for the shortcomings of single lithium manganese iron phosphate materials in rate performance and improving the overall rate performance of the cathode material. By compounding lithium manganese iron phosphate material coated with hindered amine light stabilizer with second cathode material particles, the two work synergistically and complement each other's advantages: lithium manganese iron phosphate provides a foundation for safety and long cycle life, the hindered amine coating further enhances its interfacial stability, and the second cathode material particles contribute high energy density and rate performance. Therefore, the cathode material of this application achieves an optimal balance between energy density, safety, rate performance, and cycle performance, resulting in a comprehensive improvement in overall performance.

[0030] According to embodiments of this application, the lithium manganese iron phosphate material core comprises the compound shown in Formula 1: Li m Mn x Fe y M 1-x-y PO4 Formula 1 In Formula 1, 0.9≤m≤1.1, 0.3≤x≤0.9, 0≤y≤0.8, and M is selected from at least one of Zn, Al, Na, K, Mg, Nb, Mo, and W.

[0031] According to embodiments of this application, the nickel-cobalt-manganese ternary material particles comprise the compound shown in Formula 2: Li 1+n Ni a Co b Mn c Q d O2 type 2 In Equation 2, 0≤n≤0.3, 0.3≤a≤0.9, 0.1≤b≤0.3, 0.1≤c<0.3, 0≤d≤0.1, and a+b+c+d=1; Q is selected from at least one of B, Na, K, Mg, Al, Ca, Ti, Fe, Zn, Sr, Y, Zr, Nb, Mo, Sn, Ba, Ta, and W.

[0032] According to embodiments of this application, the linker L is selected from triazine rings, benzene rings, and C2-C4 rings. 12 Any type of alkylene chain. The aforementioned linker L provides rigid support for the molecular chain, ensuring that the bifunctional group maintains optimal spatial orientation within the coating layer, thus enabling the bifunctional group to exert its superior performance.

[0033] According to embodiments of this application, the anchoring group R2 is selected from at least one of methylene diphosphonate, vinyl triphosphonate, succinic acid diacyl, arylphosphonate, citrate tricarboxylate, isonicotinic acid acyl, 3-aminopropyltriethoxysilane-carboxyl hybrid group, and pentaerythritol tetrahydroxy. The anchoring group R2 can enhance the chemical anchoring strength with the LMFP surface through π-π stacking or hydrogen bonding, preferentially guiding the conductive agent to accumulate on the LMFP surface and compensating for its poor conductivity.

[0034] According to embodiments of this application, the mass ratio of the bifunctional coating layer to the lithium manganese iron phosphate core is 0.1:99.9 to 2:98, specifically 0.3:99.7 to 1.5:98.5. As a specific example, the mass ratio of the bifunctional coating layer to the lithium manganese iron phosphate core is 0.1:99.9, 0.3:99.7, 1:99, 1.5:98.5, 2:98, or any two of these ranges. Within these ranges, the bifunctional coating layer can effectively perform its function, capturing free radicals, reducing side reactions, and inhibiting Mn dissolution.

[0035] It is understandable that the particle size matching between the first and second cathode material particles is one of the key factors affecting the overall performance of the cathode material. By optimizing the particle size distribution of the two, the smaller-sized first cathode material particles can effectively fill the voids formed by the packing of larger-sized nickel-cobalt-manganese ternary material particles, thereby significantly increasing the electrode packing density, reducing interparticle porosity, and ultimately achieving higher compaction density. Furthermore, the dense particle packing helps to construct a more stable electrode structure, improves the electrical contact between particles, and optimizes the electron transport path, thereby further enhancing the electrode's cycle stability and rate performance.

[0036] According to an embodiment of this application, the D of the first positive electrode material particle 50 The diameter ranges from 0.05 µm to 10 µm, specifically from 4 µm to 8 µm. As a concrete example, the D-value of the lithium manganese iron phosphate material core... 50 It can be a range of 0.05 µm, 0.1 µm, 0.5 µm, 1 µm, 2 µm, 4 µm, 6 µm, 8 µm, 10 µm, or any two of these ranges. In the above D... 50Within this range, smaller particle size can shorten the diffusion path of lithium ions, which is beneficial to improving rate performance; at the same time, small particles have a larger specific surface area, which can provide more electrochemical reaction active sites.

[0037] In this article, D 50 This indicates that particles with diameters smaller than or larger than this value account for 50% of the total particle volume of the cathode material. (D) 50 It can be tested using a particle size analyzer.

[0038] According to an embodiment of this application, the D of the second positive electrode material particle 50 The particle size ranges from 0.05 µm to 10 µm, specifically from 4 µm to 8 µm. As a specific example, the D0.05 of the nickel-cobalt-manganese ternary material particles... 50 It can be a range of 0.05 µm, 0.1 µm, 0.5 µm, 1 µm, 2 µm, 4 µm, 6 µm, 8 µm, 10 µm, or any two of these ranges. In the above D... 50 Within its range, it can provide high energy density and good rate performance.

[0039] According to embodiments of this application, the mass ratio of the first cathode material particles to the second cathode material particles is 2 to 9:1, specifically 3 to 7:1. As a specific example, the mass ratio of the first cathode material particles to the second cathode material particles is 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, or any two of these ranges. Within this range, the high safety and cost advantages of LMFP can be leveraged, while the ternary cathode material can compensate for the shortcomings in energy density and rate performance of LMFP, achieving synergistic effects. If the proportion of the first cathode material is too high, the intrinsic conductivity of the material will be low, leading to a decrease in rate performance, and the compaction density will be difficult to increase, limiting further improvements in energy density. If the proportion of the first cathode material is too low, the improvement effect on the safety performance of the cathode material will be limited, and it will be difficult to fully utilize the advantages of the long-cycle performance of lithium manganese iron phosphate.

[0040] According to embodiments of this application, the hindered amine light stabilizer comprises at least one of the following compounds: Formula 3-1 Formula 3-2 Formula 3-3 Equation 3-4; In Equation 3-1, n is between 0 and 8.

[0041] The aforementioned hindered amine light stabilizers not only effectively capture oxygen and free radicals generated during battery charging and discharging from the decomposition of the positive electrode and electrolyte, inhibiting electrolyte decomposition and reducing side reactions, but also reduce Mn dissolution. Simultaneously, these hindered amine light stabilizers exhibit good compatibility with binders and organic solvents during subsequent positive electrode slurry preparation, helping to maintain slurry dispersion stability and the stability of the positive electrode material structure. In particular, the hindered amine light stabilizer used in this application is a bifunctional hindered amine light stabilizer, employing a carrier to link different types of functional groups (such as hindered amine groups and anchoring groups) together, enabling it to exert a synergistic effect in capturing oxygen free radicals, resulting in superior performance compared to single-functional group stabilizers.

[0042] A second aspect of this application provides a method for preparing the cathode material described in the first aspect, comprising: S10: The lithium manganese iron phosphate material and the first solvent are mixed in the first mixture and heated to the first temperature to obtain the first mixture.

[0043] In this step, lithium manganese iron phosphate material and a first solvent are mixed to form a stable and uniform dispersion system of lithium manganese iron phosphate in the solvent, thereby reducing particle agglomeration.

[0044] In this step, there are no specific restrictions on the temperature and time of the first mixing, as long as the lithium manganese iron phosphate material is evenly dispersed. Specifically, it can be flexibly selected according to actual needs.

[0045] According to embodiments of this application, the first solvent includes at least one selected from ethanol, N-methylpyrrolidone, isopropanol, butyl acetate, N,N-dimethylformamide, tetrahydrofuran, toluene, dimethyl sulfoxide, cyclohexane, acetone, and pyridine, specifically isopropanol. These solvents are relatively inexpensive and readily available.

[0046] According to embodiments of this application, the mass ratio of the lithium manganese iron phosphate material to the first solvent is 1:3-5, specifically 1:3, 1:3.5, 1:4, 1:4.5, 1:5, or any range between two of these. Within the above range, it helps to uniformly disperse the lithium manganese iron phosphate material in the first solvent.

[0047] According to an embodiment of this application, the first temperature is 25℃-100℃, specifically 75℃-85℃. As a specific example, the first temperature can be 25℃, 30℃, 40℃, 50℃, 60℃, 70℃, 80℃, 85℃, 90℃, 100℃, or any range between two of these. Within the above range, it helps the lithium manganese iron phosphate material to be uniformly dispersed in the first solvent.

[0048] S20: The hindered amine light stabilizer and the second solvent are mixed for the second time to obtain a second mixture.

[0049] In this step, the hindered amine light stabilizer is mixed with the second solvent to form a stable and uniform dispersion system of the hindered amine light stabilizer in the solvent, thereby reducing the agglomeration of the hindered amine light stabilizer.

[0050] According to embodiments of this application, the mass ratio of the hindered amine light stabilizer to the second solvent is 1:40-60, specifically 1:40, 1:50, 1:60, or any combination thereof. Within this mass ratio range, it is beneficial for the hindered amine light stabilizer to be uniformly dispersed in the second solvent.

[0051] According to an embodiment of this application, the temperature of the second mixing is 50℃-100℃, specifically 89℃~91℃. As a specific example, the temperature of the second mixing can be 50℃, 60℃, 70℃, 80℃, 85℃, 89℃, 90℃, 91℃, 95℃, 100℃, or any range between two of these. Within the above range, damage to the hindered amine light stabilizer structure is reduced or avoided, while allowing the hindered amine light stabilizer to be more uniformly dispersed.

[0052] According to embodiments of this application, the second mixing time is 20 min to 50 min, specifically 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, or any combination thereof. Within this range, the hindered amine light stabilizer is more fully dispersed in the second solvent while reducing wasted time.

[0053] S30: Mix and coat the first mixture and the second mixture to obtain the first cathode material particles.

[0054] In this step, the first and second mixtures are combined to coat the hindered amine light stabilizer onto the surface of the lithium manganese iron phosphate material. After drying, a coating layer is formed, resulting in the first cathode material particles. Using a mixed solution for direct wet coating simplifies the process, reduces equipment requirements, and offers a shorter operating cycle and controllable costs.

[0055] According to an embodiment of this application, the mixing and coating process includes: mixing the first mixture and the second mixture at a rotation speed of 200 rpm to 4000 rpm and a temperature of 40 ℃ to 100 ℃, and then drying them until the solvent evaporates to form the bifunctional coating layer. As a specific example, a stirrer is used to stir while heating, with the heating temperature controlled at 80 ℃ and the rotation speed controlled at 1000 rpm.

[0056] According to the embodiments of this application, there are no specific limitations on the drying temperature, time, or drying method, as long as the first solvent and the second solvent can be sufficiently removed. Specifically, they can be flexibly selected according to the actual situation.

[0057] S40: Mix the first cathode material particles and the second cathode material particles to obtain the cathode material.

[0058] In this step, the first cathode material particles and the second cathode material particles are mixed evenly to obtain the cathode material. There are no specific limitations on the mixing method and time; the mixing method can be flexibly selected according to the actual situation.

[0059] A third aspect of this application provides a positive electrode slurry, comprising: Organic solvents; Adhesive; Conductive agents, including zero-dimensional conductive agents and one-dimensional / two-dimensional conductive agents; And the positive electrode material described in the first aspect, wherein, based on the total mass of the conductive agent, 60%-80% of the zero-dimensional conductive agent is distributed on the surface of the first positive electrode material particles in the positive electrode material.

[0060] In the aforementioned cathode slurry, by limiting the proportion of zero-dimensional conductive agent distributed on the surface of LMFP particles in the cathode material, the guiding effect of the anchoring groups of the hindered amine light stabilizer on the conductive agent can be fully utilized. This allows the zero-dimensional conductive agent to preferentially coat the less conductive LMFP surface, forming a dense point-contact conductive layer, while the one-dimensional / two-dimensional conductive agent constructs a long-range conductive network. The synergistic effect of both significantly improves the electronic conductivity of LMFP, reduces the interparticle contact internal resistance, and thus improves the rate performance of the battery. In addition, a uniform and robust conductive layer helps maintain the integrity of the electrode structure, suppresses conductive failure caused by volume expansion during cycling, extends cycle life, and improves the dispersion stability and coating consistency of the slurry.

[0061] According to embodiments of this application, the first conductive agent is a zero-dimensional conductive agent selected from at least one of Super P, acetylene black, and Ketjen black; the second conductive agent is a one-dimensional / two-dimensional conductive agent selected from at least one of carbon nanotubes, graphene, and carbon fibers; the aforementioned conductive agents are distributed between and on the surface of the cathode material particles, providing channels for the rapid migration of electrons during charging and discharging, thereby improving the rate performance and cycle stability of the cathode material. The one-dimensional conductive agent (such as carbon nanotubes or carbon fibers) or the two-dimensional conductive agent (such as graphene) is used to construct a long-range conductive network, while the zero-dimensional conductive agent is responsible for achieving point-to-point connections between particles; the two work synergistically to efficiently improve the conductivity of both the first cathode material particles and the nickel-cobalt-manganese ternary material simultaneously.

[0062] According to embodiments of this application, based on the total mass of the conductive agent, the mass ratio of the zero-dimensional conductive agent to the one-dimensional / two-dimensional conductive agent is 0.5 to 5:1, specifically 1 to 2:1. As a specific example, the mass ratio of the zero-dimensional conductive agent to the one-dimensional / two-dimensional conductive agent is 0.5:1, 1:1, 2:1, 3:1, 4:1, 5:1, or any two of these ratios. Within the above range, the zero-dimensional conductive agent and the one-dimensional / two-dimensional conductive agent can fully exert their synergistic effect. Specifically, the zero-dimensional conductive agent uniformly fills the tiny gaps between the positive electrode material particles in a dotted pattern, forming dense local conductive contacts to ensure sufficient contact on the particle surface; the one-dimensional / two-dimensional conductive agent utilizes its high aspect ratio to build a long-range conductive network between the particles. Together, they construct a multi-level conductive structure combining points and lines.

[0063] According to an embodiment of this application, the binder comprises polyvinylidene fluoride (PVDF). The binder exhibits good compatibility with the hindered amine light stabilizer on the surface of the first cathode material particles, which helps maintain the integrity of the coating layer and the dispersion stability of the particles during homogenization.

[0064] According to embodiments of this application, the organic solvent includes N-methylpyrrolidone. This organic solvent can fully dissolve or disperse the binder and conductive agent, allowing the components to be uniformly distributed in the positive electrode slurry, forming a homogeneous slurry with good flowability, thereby ensuring the smooth progress of subsequent coating processes.

[0065] A fourth aspect of this application provides a method for preparing the positive electrode slurry described in the third aspect, comprising: The first positive electrode material particles, the first binder, the first conductive agent and the first organic solvent are mixed to obtain the first slurry; The first slurry, the second positive electrode material particles, the second binder, the second conductive agent, and the second organic solvent are mixed to obtain the positive electrode slurry.

[0066] During the preparation of the positive electrode slurry, under the action of the first binder, the first positive electrode material particles and the first conductive agent are uniformly mixed, allowing the first conductive agent to adhere to the surface of the first positive electrode material particles as much as possible, thereby forming a point-to-surface contact conductive network on the surface of the first positive electrode material particles. This conductive network can improve the conductivity of the first positive electrode material particles, thereby improving the conductivity of the positive electrode material. Subsequently, the second binder binds the second positive electrode material particles, the second conductive agent, and the components in the first slurry into a whole. At the same time, the second conductive agent is dispersed in the gaps between the particles, working synergistically with the first slurry to form a surface conductive network and construct a complete electron transport path.

[0067] According to the embodiments of this application, the specific parameters for mixing in the above two steps are not specifically limited, as long as the first slurry and the positive electrode slurry are mixed evenly. The specific parameters can be flexibly selected according to the actual situation. For example, the first positive electrode material particles, the first binder, the first conductive agent, and the first organic solvent are mixed at a rotation speed of 35 rpm-50 rpm for 1 h-2 h to obtain the first slurry. For example, the first slurry, the second positive electrode material particles, the second binder, the second conductive agent, and the second organic solvent are mixed and dispersed at a linear velocity of 12 m / s-20 m / s for 1 h-2 h to obtain the positive electrode slurry.

[0068] According to embodiments of this application, the mass ratio of the first conductive agent to the second conductive agent is not less than 1:1. This allows the first conductive agent to adhere as much as possible to the surface of the first cathode material particles, thereby forming a point-to-surface contact conductive network on the surface of the first cathode material particles, thus improving the conductivity of the LMFP particles. Simultaneously, it also increases the amount of conductive agent between the NCM and LMFP, improving the overall rate performance of the cathode material, enhancing the bonding force between the two phase particles, suppressing volume expansion during cycling, and improving cycle life.

[0069] In the preparation of the first slurry, the first binder is added in the form of a liquid adhesive. Specifically, PVDF solid and the first organic solvent (accounting for 2%-10% of the total mass of the organic solvent) are mixed.

[0070] According to an embodiment of this application, based on the total mass of the positive electrode slurry, the total mass percentage of the first binder and the second binder is 0.8%-2%, specifically such as 0.8%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, or any two of these ranges. Within the above range, the binder can achieve uniform dispersion of the conductive agent and the positive electrode material particles, and form a continuous and uniform bonded network structure within the positive electrode slurry.

[0071] According to embodiments of this application, based on the total mass of the first binder and the second binder, the mass percentage of the first binder is 50%-100%, specifically 50%, 60%, 70%, 80%, 90%, 100%, or any two of these ranges. Within this range, the first binder can fully exert its adhesive and dispersing effects during mixing, promoting the uniform distribution of the first conductive agent on or around the surface of the first positive electrode material particles, forming a stable point-to-surface contact conductive network, laying the foundation for the subsequent construction of an efficient electron transport path.

[0072] According to embodiments of this application, based on the total mass of the positive electrode slurry, the total mass percentage of the first conductive agent and the second conductive agent is 1.5% to 3.5%, specifically 1.5%, 2%, 2.5%, 3%, 3.5%, or any two of these ranges. Within the above range, the conductive agent can form a uniform and complete conductive network in the positive electrode material, effectively improving electron conduction and thus improving the rate performance of the battery.

[0073] According to embodiments of this application, based on the total mass of the first conductive agent and the second conductive agent, the mass percentage content of the first conductive agent is 50%-90%, specifically 70%-80%. As a specific example, based on the total mass of the first conductive agent and the second conductive agent, the mass percentage content of the first conductive agent is 50%, 60%, 70%, 72%, 74%, 76%, 78%, 80%, 90%, or any two of these ranges. Within the above range, a uniform and dense point-to-surface conductive network can be formed on the surface of the first positive electrode material particles, effectively improving its electronic conductivity.

[0074] According to embodiments of this application, the second adhesive and the first adhesive constitute the entire adhesive system, and the first conductive agent and the second conductive agent constitute the entire conductive agent system. Specifically, the mass percentage content of the second adhesive and the second conductive agent can be adjusted accordingly based on the mass percentage content of the first adhesive and the first conductive agent.

[0075] According to embodiments of this application, the first organic solvent and the second organic solvent each independently comprise N-methylpyrrolidone. The aforementioned organic solvents and the hindered amine light stabilizer on the surface of the first cathode material particles have good compatibility, maintaining particle dispersibility while ensuring the coating layer structure is not damaged.

[0076] According to embodiments of this application, the first organic solvent and the second organic solvent constitute all the organic solvents in the positive electrode slurry. Based on the total mass of the positive electrode slurry, the total mass percentage of the organic solvents is 50%-80%. Within the above range, the organic solvents can fully dissolve or disperse the binder and conductive agent, so that the first positive electrode material particles, the second positive electrode material particles, and each component are uniformly distributed in the positive electrode slurry, forming a homogeneous slurry with good flowability, thereby ensuring the smooth progress of subsequent coating processes.

[0077] According to embodiments of this application, taking the total mass of the positive electrode slurry as 100%, the mass percentage excluding the mass percentages of binder, conductive agent, and organic solvent is the content of the positive electrode material. A fifth aspect of this application provides a positive electrode sheet comprising a positive electrode current collector and a positive electrode coating layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode coating layer comprises the positive electrode material described in the first aspect, or a coating formed after drying the positive electrode slurry described in the third aspect. All the features and advantages of this positive electrode sheet, including the positive electrode material described in the first aspect, will not be elaborated further here.

[0078] According to an embodiment of this application, the positive current collector includes a metal foil; as a specific example, this application uses aluminum foil.

[0079] According to embodiments of this application, a positive electrode slurry is coated onto at least a portion of the surface of the positive electrode current collector and dried at 70°C-120°C for 2-10 minutes to form a coating, which is the positive electrode dressing layer. Within the above range, the organic solvent can evaporate at an appropriate rate, thereby ensuring a uniform structure of the positive electrode dressing layer and complete curing of the positive electrode dressing layer, while also taking into account production efficiency.

[0080] A sixth aspect of this application provides a lithium-ion battery comprising the positive electrode material described in the first aspect or the positive electrode sheet described in the fifth aspect. This lithium-ion battery exhibits excellent rate performance, capacity density, and cycle performance.

[0081] It is understandable that there are no particular restrictions on the specific types and structures of the lithium-ion batteries mentioned above, as long as a positive electrode material is required. For example, according to performance classification, batteries can include, but are not limited to, primary batteries, secondary batteries, etc. According to shape classification, batteries can include, but are not limited to, prismatic batteries, cylindrical batteries, etc.; according to outer packaging classification, batteries can include, but are not limited to, pouch batteries, hard-shell batteries, etc.

[0082] Typically, a lithium-ion battery can include the positive electrode, negative electrode, electrolyte, and separator mentioned above.

[0083] According to the embodiments of this application, in the above-mentioned lithium-ion battery, the electrolyte can be a liquid electrolyte (i.e., an electrolyte solution) or a solid electrolyte.

[0084] According to embodiments of this application, the electrolyte is a liquid electrolyte. In this case, the positive electrode, negative electrode, and separator can be fabricated into a battery cell using a winding or stacking process. The battery cell and electrolyte can be housed in an outer packaging. During battery charging and discharging, active ions repeatedly insert and extract between the positive and negative electrode plates. The electrolyte acts as a conductor of ions between the positive and negative electrode plates. The separator is positioned between the positive and negative electrode plates, primarily serving to prevent short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0085] According to an embodiment of this application, the electrolyte is a solid electrolyte. In this case, the positive electrode, negative electrode, electrolyte, and battery separator can be manufactured into a battery cell through a winding or stacking process, and the battery cell can be housed in an outer package. The positive and negative electrode sheets are alternately stacked, and the electrolyte and battery separator are disposed between adjacent positive and negative electrode sheets.

[0086] According to an embodiment of this application, the lithium-ion battery further includes a negative electrode sheet, the negative electrode sheet including a negative electrode current collector and a negative electrode coating layer disposed on at least one side surface of the negative electrode current collector, the negative electrode coating layer including a negative electrode active material.

[0087] According to embodiments of this application, the negative electrode active material includes silicon-based materials and carbon materials.

[0088] According to embodiments of this application, the negative electrode sheet further includes at least one of a negative electrode binder, a negative electrode conductive agent, and a thickener.

[0089] According to embodiments of this application, the negative electrode binder includes at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), and polyacrylamide (PAM).

[0090] According to embodiments of this application, the negative electrode conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, and graphene.

[0091] According to embodiments of this application, the thickener includes carboxymethyl cellulose (CMC).

[0092] According to embodiments of this application, the diaphragm can be made of various porous structures with good stability, such as polyethylene diaphragms, polypropylene diaphragms, PE ceramic-coated diaphragms, etc.

[0093] A seventh aspect of this application provides an electrical device comprising the positive electrode material described in the first aspect, the positive electrode slurry described in the third aspect, the positive electrode sheet described in the fifth aspect, or the lithium-ion battery described in the sixth aspect. All the features and advantages of the positive electrode material described in the first aspect, the coating formed after drying the positive electrode slurry described in the third aspect, the positive electrode sheet described in the fifth aspect, or the lithium-ion battery described in the sixth aspect are not elaborated upon here.

[0094] It is understood that there are no particular restrictions on the specific type of electrical device; it can be any device that uses a lithium-ion battery as a power source or energy storage unit. For example, electrical devices include, but are not limited to, electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), mobile terminals (such as mobile phones, laptops, game consoles, wearable devices, etc.), drones, aerospace equipment, satellites, ships, energy storage systems, and so on.

[0095] It is understandable that, in addition to the lithium-ion battery mentioned above, the electrical device also includes necessary structures and components, all of which can be made with reference to conventional technologies. For example, an electric vehicle may include a body, chassis, tires, navigation system, radar system, steering system, braking system, lubrication system, cooling system, driving system, etc., which will not be described in detail here.

[0096] The embodiments of this application are described in detail below.

[0097] The hindered amine light stabilizer preparation method used in the embodiments of this application is as follows: Synthesis of Compound 3-1: In a strictly anhydrous reactor, 1.0 mol equivalent of hindered phenolic carboxylic acid (3,5-di-tert-butyl-4-hydroxybenzoic acid) was dissolved in 3–5 volumes of dry toluene or dichloromethane, and 0.05–0.1 mol equivalent of N,N-dimethylformamide (DMF) was added as a catalyst. The temperature was raised to 40–50 °C, and 1.2–1.5 mol equivalents of thionyl chloride (SOCl2) were slowly added dropwise over 1–2 h. After the addition was complete, the temperature was raised to 60–65 °C, and the reaction was continued for 4–6 h. Thin-layer chromatography or gas chromatography was used to monitor the complete conversion of the starting material. After the reaction was completed, excess thionyl chloride and solvent were removed by vacuum distillation (80–90 °C / 20 mmHg–30 mmHg) to obtain a pale yellow oily or solid hindered phenolic chloride intermediate. Add cyanuric chloride (1.0 eq) and 4–6 times the volume of toluene to a reaction flask, cool to 0℃–5℃, and add dropwise a mixture of 1.0 eq–1.05 eq of tert-octylamine and an appropriate amount of toluene while stirring, keeping the temperature below 10℃ for about 2h–3h. After the addition is complete, maintain the reaction temperature for 1h–2h, then raise the temperature to 20℃–30℃ and slowly add a 10% sodium hydroxide aqueous solution (adjusting the pH to 8–9), continuing the reaction for 2h–3h. Allow the mixture to stand and separate the layers to obtain a toluene solution containing monosubstituted triazine. Transfer this solution to a high-pressure reactor, add 1.0 eq–1.1 eq of N,N'-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine (i.e., "hexamethylenediamine piperidine"), and purge with nitrogen three times. The temperature was raised to 70℃–80℃, and a pre-prepared 10% sodium hydroxide solution was slowly added dropwise. The vessel was then closed, and the temperature was raised to 150℃–170℃, and the pressure increased to 1.5 MPa–2.0 MPa. The reaction was maintained at this temperature and pressure for 8–12 hours. After the reaction, the temperature was lowered to room temperature, and the mixture was neutralized with dilute hydrochloric acid. The organic layer was separated, and toluene was recovered by vacuum distillation to obtain a viscous hindered amine intermediate. The obtained hindered amine intermediate was dissolved in 2–3 volumes of dry dichloromethane or tetrahydrofuran, and 1.5–2.0 molar equivalents of dry triethylamine were added as an acid-binding agent. The temperature was lowered to 0℃–5℃ under nitrogen protection. A mixture of hindered phenolic chloride (1.0 eq–1.2 eq) prepared in the first stage and an equal volume of dry solvent was slowly added dropwise. The internal temperature was controlled not to exceed 10℃ during the dropwise addition process, and the addition time was approximately 1–2 hours. After the addition is complete, allow the mixture to rise naturally to room temperature (20℃–25℃), and continue stirring for 24h–48h, during which time TLC can be used to monitor until the acyl chloride has essentially disappeared. After the reaction is complete, filter to remove the generated triethylamine hydrochloride. Wash the filtrate 2–3 times each with 5% sodium bicarbonate aqueous solution and saturated sodium chloride aqueous solution, separate the organic phase, and dry it with anhydrous sodium sulfate. After removing the solvent under reduced pressure, recrystallize the crude product with a mixed solvent (e.g., ethanol / water = 4:1) or purify it by column chromatography (eluent: petroleum ether / ethyl acetate = 6:1).Finally, the compound was dried under vacuum at 50℃–60℃ for 12 hours to obtain compound 3-1.

[0098] Synthesis of Compound Formula 3-2: The preparation methods of the two precursors are as follows: Precursor A: Bromobenzotriazole phenol, synthesized through diazotization, coupling, and reduction ring-closure reactions. o-Nitroaniline is used as the starting material, reacting with sodium nitrite at 0–5℃ to generate a diazonium salt, which is then coupled with a substituted phenol to generate an azo dye intermediate. Subsequently, reduction ring closure is achieved under the action of reducing agents such as glucose / zinc powder to generate a benzotriazole skeleton. Then, side-chain bromination is introduced via NBS under AIBN initiation to introduce a linking site, yielding bromobenzotriazole phenol. Precursor B: N-methyl-2,2,6,6-tetramethyl-4-piperidinol is commercially available, CAS number 2403-89-6. After the precursor preparation was completed, the first step was to connect the first molecule of N-methyl hindered amino alcohol (precursor B) to the triazine ring under 0–5℃ conditions with acetone as solvent and potassium carbonate as acid-binding agent, to obtain a chlorinated monosubstituted intermediate. The second step was to raise the temperature to 40–60℃ and add bromobenzotriazole phenol (precursor A), using toluene as solvent and strong acid-binding agents such as sodium hydride to activate the phenolic hydroxyl group, causing the benzotriazole fragment to undergo nucleophilic substitution with the second chlorine, generating a disubstituted triazine intermediate. The third step was to further raise the temperature to 90–110℃ under reflux conditions and add N-methyl hindered amino alcohol (precursor B) again to complete the substitution of the third chlorine. Thus, the three functional fragments were sequentially connected to the triazine skeleton. Each step required strict anhydrous and oxygen-free operation under inert gas protection. After the reaction was completed, the compound was obtained by post-treatment such as filtration, washing, and drying.

[0099] Synthesis of compound formula 3-3: stepwise polycondensation of cyanuric chloride, with block oligomers of molecular weight 2600~3400 as the target product, the overall molar ratio of the feed is cyanuric chloride: di-n-butylamine: N-butyl-4-piperidinamine: N,N′-di(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine = 2:1:1:1.5, specifically achieved through the following five steps: (1) Synthesis of intermediate I: 1.0 eq cyanuric chloride is dissolved in a mixed solvent of acetone / water (volume ratio 2:1), and 2.0 eq di-n-butylamine is slowly added dropwise at a low temperature of 0~5℃, while maintaining pH=7~8 with 10% NaOH solution. After reacting for 2~3 hours, the mixture is filtered, washed with water, and dried to obtain white crystalline intermediate I, namely 2,4-di(di-n-butylamino)-6-chloro-1,3,5-triazine; (2) Synthesis of Intermediate II: 1.0 eq cyanuric chloride was dissolved in xylene, and 1.0 eq N-butyl-2,2,6,6-tetramethyl-4-piperidinamine (CAS: 36177-92-1) in xylene was added dropwise at a temperature below 5°C. The reaction was maintained at this temperature for 3 hours to obtain Intermediate II, namely a xylene solution of 2-(N-butyl-2,2,6,6-tetramethyl-4-piperidinamine)-4,6-dichloro-1,3,5-triazine, which was used directly in the next step without separation. (3) Synthesis of intermediate III: 1.5 eq N,N′-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine was added to the xylene solution of intermediate II and reacted at 80°C for 2 hours. After filtration, washing and drying, intermediate III (N,N″-1,6-hexanediol di[N-butyl-6-chloro-N,N″-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,3,5-triazine-2,4-diamine]) was obtained. (4) Polymerization reaction: Intermediate III and 1.5 eq N,N′-bis(2,2,6,6-tetramethyl-4-piperidinyl)-1,6-hexanediamine were added to a high-pressure reactor and reacted at 160~180°C for 5 hours to obtain block oligomers. (5) End-capping reaction: Add 0.5 eq intermediate I to the oligomer in the autoclave and continue the reaction at 160~180℃ for 3 hours. After cooling, filtering, and vacuum distillation to remove the solvent and unreacted monomers, granulate or pulverize to obtain compound formula 3-3.

[0100] Synthesis of Compound 3-4: Compound 1 (6.08 g, 20 mmol), 1,2,2,6,6-pentamethylpiperidinol (16.43 g, 96 mmol), and 100 mL of n-octane were added to a 500 mL four-necked flask equipped with a nitrogen-protected azeotropic dehydration apparatus. The mixture was heated to reflux to remove water. 0.12 g of tetraisopropylphthalate was added to the reaction solution, and methanol produced during the reaction was continuously distilled off. The reaction was monitored by TLC (dichloromethane / methanol / ammonia water volume ratio 9.5:1:1). After the reaction was complete, the temperature was lowered to 60 °C, 2 mL of deionized water was added, and the reaction was allowed to proceed for 20 min. The added deionized water was removed by reflux, and the resulting titanium hydroxide precipitate was filtered off while hot. The filtrate was washed with deionized water at 90 °C and concentrated under reduced pressure to obtain compound 3-4.

[0101] The chemical formulas of the coatings used in Comparative Examples 5-8 are as follows: Compound A Compound B Compound C (CAS: 70624-18-9) Compound D (CAS: 52829-07-9).

[0102] Compound A can be synthesized via the following route: UV-3853 (5 g, 10 mmol), tert-butanol (30 mL), and MoO3 (0.08 g) were added to a four-necked flask and stirred to form a homogeneous system. The mixture was heated to reflux, and then an 80% (w / w) aqueous solution of tert-butyl peroxide was slowly added dropwise. The mixture was stirred under reflux for 25 h. During this period, tert-butyl peroxide was added to the reaction system to maintain an excess. The reaction solution was cooled to room temperature and filtered to remove the catalyst. A 30% (w / w) aqueous solution of Na2SO3 was prepared and added to the filtrate. The mixture was stirred at 60 °C for 0.5 h to remove excess t-BuOOH. The liquid was separated, and the organic phase was collected and the solvent was removed by rotary evaporation to obtain compound A. Compound B can be synthesized via the following route: To a dry 500 mL single-necked flask, add chloroacetyl chloride (56.46 g, 0.5 mol) and 160 mL of dichloromethane. Under ice-water bath conditions, slowly add a mixed solution of 2,4-dihydroxybenzophenone (68.54 g, 0.32 mol), triethylamine (56.5 g, 0.5 mol), and 160 mL of dichloromethane while continuously stirring. After the addition is complete, raise the temperature to room temperature and allow the reaction to proceed. After approximately 8 hours, stop the reaction, wash with water, separate the layers, and concentrate the organic phase to 50 mL by rotary evaporation at 50 °C. Then, add 50 mL of methanol, and again concentrate the organic phase to 50 mL by rotary evaporation at 50 °C. After cooling and standing, a large amount of crystals precipitate. Filter the crystals and dissolve the filter cake in 50 mL of dichloromethane. Then, while stirring vigorously, pour in 500 mL of petroleum ether, precipitating a flocculent solid. Filter and dry the solid to obtain the intermediate. An intermediate (68.54 g, 0.32 mol), triethylamine (68.54 g, 0.32 mol), and dichloromethane (250 mL) were added to a dry 500 mL single-necked flask. 2,2,6,6-Tetramethylpiperidinamine (52 g, 0.32 mol) was then slowly added dropwise under ice-water bath conditions with constant stirring. After the addition was complete, the mixture was brought to room temperature. The reaction was stopped after approximately 2 hours. The mixture was washed with water, separated, and the organic phase was removed by rotary evaporation at 50 °C to obtain compound B.

[0103] Example 1 (1) Preparation of the first cathode material particles: LiMn was mixed at a mass ratio of 1:4 0.6 Fe 0.4 PO4 (LMFP) cathode material (D 50 =0.5μm) and isopropanol were mixed, and LMFP was immersed in isopropanol. The mixture was then heated to 75 °C and dispersed by stirring at 2000 rpm to obtain a first mixture. The hindered amine light stabilizer compound (n=1) and compound (mass ratio 1:1) of formula 3-1 and formula 3-2 were weighed according to a mass ratio of 0.8:99.2. The hindered amine light stabilizer was added to isopropanol (mass ratio of hindered amine light stabilizer to isopropanol 1:50) and stirred until completely dissolved to obtain a homogeneous second mixture. The second mixture was slowly added dropwise to the first mixture, and stirring was continued to ensure uniform mixing. The temperature was maintained at 75 °C, and stirring continued until the solvent slowly evaporated. The resulting solid product was collected, yielding the first cathode material particles (D 50 = 7μm); (2) Preparation of positive electrode slurry: according to LMFP: nickel-cobalt-manganese ternary material (LiNi 0.6 Co 0.2 Mn 0.2O2): Super P: CNTs: PVDF = 66.85%: 28.65%: 1.3%: 1%: 2.2% (wherein, the mass ratio of the first cathode material particles to NCM particles is 7:3, and the D of NCM is...) 50 LMFP, NCM, Super P, CNTs, and PVDF were weighed out in proportions of 7 μm. Super P was then used as the first conductive agent, and 60% PVDF (PVDF and NMP were mixed and added in a gel form, with a solid content of 6%) was added. This mixture was then stirred with the first cathode material particles in a dual planetary stirrer at 40 rpm for 1 h to obtain the first slurry. NCM, CNTs, the remaining PVDF, and NMP were then added to the first slurry, resulting in a solid content of 58%. The dispersion was then performed using a dispersion disc at a linear velocity of 15 m / s for 1.5 h to obtain the cathode slurry. (3) Preparation of positive electrode sheet: The above positive electrode slurry is coated on one side of aluminum foil, and then dried on a conveyor belt in an oven at 95 ℃ for 5 min to obtain the positive electrode sheet; (4) Preparation of negative electrode sheet: Graphite, conductive agent Super P, CMC and SBR are mixed in a mass ratio of 96.5:0.5:1.2:1.8 using a double planetary stirrer to form a negative electrode slurry with a solid content of 51%. The negative electrode slurry is coated on a copper foil with a thickness of 6µm, and after drying and rolling, a negative electrode sheet is obtained.

[0104] (5) Diaphragm: A 16µm polyethylene diaphragm is used.

[0105] (6) Electrolyte: The electrolyte is 1 mol / L LiPF6 + 0.2 mol / L LiFSI, 0.5 wt% LiODFB additive, and the solvent is a mixture of ethylene carbonate (EC): ethyl methyl carbonate (EMC): diethyl carbonate (DEC) (volume ratio of 1:1:1).

[0106] (7) Preparation of lithium-ion batteries: The positive electrode, negative electrode and separator are stacked by Z-shaped stacking machine. After stacking, the batteries are hot-pressed, put into the shell, baked, injected with liquid, and formed to obtain soft pack batteries.

[0107] The specific parameters for Examples 2-24 and Comparative Examples 1-8 are detailed in Tables 1 and 2.

[0108] Electrical performance parameters were tested using the Shenzhen Xinwei CT-3008 battery testing system. The charge / discharge voltage range was controlled at 2.5V-4.3V, with constant current and constant voltage, and a cutoff rate of 0.05C. At room temperature (25℃), the pouch cells were charged and discharged at 0.2C / 0.2C and 1.0C to evaluate the charge / discharge specific capacity of the cathode material and the capacity retention rate after 300 cycles at 1C / 1C@room temperature (25℃).

[0109] First cathode material particles D 50 D of the second cathode material particles 50 The particle size distribution can be determined by a particle size analyzer. The test should be performed according to the standard GB / T 19077-2016 "Particle Size Distribution - Laser Diffraction Method" using a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0110] Table 1

[0111] Table 2

[0112] Conclusion: Comparing Examples 1, 4, 12-14, and Comparative Example 1, Comparative Example 1 did not use the hindered amine light stabilizer coating agent of this application to coat the lithium manganese iron phosphate material. Although the specific capacity of the 1C first cycle was basically the same, the lithium manganese iron phosphate material coated with the hindered amine light stabilizer coating agent of this application was used to guide the conductive agent to preferentially adhere to the surface of the lithium manganese iron phosphate material. The 300-cycle retention rate and rate performance of the cathode material were improved. This is due to the hindered amine light stabilizer molecules of this application.

[0113] In Examples 1, 5, and 10-11, the mass ratio of zero-dimensional conductive agent (Super P) to one-dimensional / two-dimensional conductive agent is within the range of this application, resulting in improved 1C first-cycle specific capacity, 300-cycle retention rate, and rate performance. However, in Example 9, the mass ratio of Super P to CNTS exceeds the range of this application, leading to decreased 1C first-cycle specific capacity and 300-cycle retention rate, although the rate performance remains high. This is because Super P has better conductivity, and a higher Super P content results in a more significant initial rate performance ratio for the cathode material, but also more side reactions, increased Li loss, and poorer cycle performance in the later stages. In Example 8, due to the lower content of zero-dimensional conductive agent, both the 300-cycle retention rate and rate performance of the cathode material decreased.

[0114] Comparing Examples 1-24 and Comparative Examples 2-3, the absence of lithium manganese iron phosphate material or nickel-cobalt-manganese ternary material particles did not improve the overall performance of the cathode material. This indicates that compounding lithium manganese iron phosphate material coated with hindered amine light stabilizer with the second cathode material particles can achieve a synergistic effect and jointly improve the overall performance of the cathode material.

[0115] In addition, in Comparative Example 4, the conductive agent was added in the conventional order of feeding when preparing the positive electrode slurry. That is, the first positive electrode particles and the second positive electrode particles were added at the same time, and then all the conductive agent and binder were added. This caused the conductive agent particles to be unable to preferentially adhere to the surface of the lithium manganese iron phosphate material, which resulted in a decrease in the 1C specific capacity, 300-cycle retention rate and rate performance of the positive electrode material.

[0116] Finally, in Comparative Examples 5-8, lithium manganese iron phosphate materials were coated with compounds A, B, C, and D, respectively. The 1C specific capacity, 300-cycle retention rate, and rate performance of the prepared cathode materials all decreased. This indicates that the hindered amine light stabilizer of this application, which has both hindered amine groups and anchoring groups, can significantly improve the electrochemical stability of the cathode material and effectively improve its specific capacity, cycle life, and rate performance.

[0117] In summary, this application combines lithium manganese iron phosphate material coated with hindered amine light stabilizer with nickel-cobalt-manganese ternary material particles, achieving an optimal balance between energy density, safety, rate performance, and cycle performance in the cathode material, resulting in a comprehensive improvement in overall performance.

[0118] In the description of this specification, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0119] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0120] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A positive electrode material, characterized in that, include: The first cathode material particle includes a lithium manganese iron phosphate core and a bifunctional coating layer, wherein the bifunctional coating layer coats at least a portion of the surface of the core. The second cathode material particles include nickel-cobalt-manganese ternary material particles. The bifunctional coating layer contains a hindered amine light stabilizer with the structure R1-L-R2, wherein R1 is a hindered amine group; R2 is an anchoring group that is connected to the metal ions on the surface of the lithium manganese iron phosphate core via a coordinate bond, and the anchoring group is selected from at least one of carboxyl derivatives, hydroxyl derivatives, phosphate ester derivatives, amino derivatives, and acyl derivatives; L is a linker.

2. The cathode material according to claim 1, characterized in that, The core of the lithium manganese iron phosphate material includes the compound shown in Formula 1: Li m Mn x Fe y M 1-x-y PO4 formula 1 In Formula 1, 0.9≤m≤1.1, 0.3≤x≤0.9, 0.1≤y≤0.8, and M is selected from at least one of Zn, Al, Na, K, Mg, Nb, Mo, and W; The nickel-cobalt-manganese ternary material particles include the compound shown in Formula 2: Li 1+n Ni a Co b Mn c Q d O2 formula 2 In Equation 2, 0≤n≤0.3, 0.3≤a≤0.9, 0.1≤b≤0.3, 0.1≤c<0.3, 0≤d≤0.1, and a+b+c+d=1; Q is selected from at least one of B, Na, K, Mg, Al, Ca, Ti, Fe, Zn, Sr, Y, Zr, Nb, Mo, Sn, Ba, Ta, and W.

3. The cathode material according to claim 1, characterized in that, At least one of the following conditions must be met: The linker L is selected from triazine rings, benzene rings, and C2-C4 rings. 12 Any one of the alkylene chains; The anchoring group R2 is selected from at least one of methylene diphosphonic acid, vinyl triphosphonic acid, succinic acid diacyl, arylphosphonic acid, citrate tricarboxylic acid, isonicotinic acid acyl, 3-aminopropyltriethoxysilane-carboxyl hybrid group, and pentaerythritol tetrahydroxy. The mass ratio of the bifunctional coating layer to the lithium manganese iron phosphate core is 0.1:99.9~2:98, preferably 0.3:99.7~1.5:98.5; The mass ratio of the first positive electrode material particle to the second positive electrode material particle is 2~9:1, preferably 3~7:

1.

4. The cathode material according to any one of claims 1 to 3, characterized in that, At least one of the following conditions must be met: The hindered amine light stabilizer includes at least one of the following compounds: Formula 3-1 Equation 3-2 Formula 3-3 Equation 3-4; In Equation 3-1, n is 0-8; D of the first cathode material particles 50 The value is 0.05 µm to 10 µm, preferably 4 µm to 8 µm; D of the second cathode material particles 50 The value is 0.05 µm to 10 µm, preferably 4 µm to 8 µm.

5. A method for preparing the cathode material according to any one of claims 1 to 4, characterized in that, include: The lithium manganese iron phosphate material and the first solvent are mixed in the first mixture and heated to the first temperature to obtain the first mixture. The hindered amine light stabilizer and the second solvent are mixed a second time to obtain a second mixture; The first mixture and the second mixture are mixed and coated to obtain first cathode material particles; The first cathode material particles and the second cathode material particles are mixed to obtain the cathode material.

6. The method according to claim 5, characterized in that, The mixed coating includes: mixing the first mixture and the second mixture at a rotation speed of 200 rpm to 4000 rpm and a temperature of 40 ℃ to 100 ℃ and drying them until the solvent evaporates to form the bifunctional coating layer.

7. The method according to claim 5, characterized in that, At least one of the following conditions must be met: The first solvent and the second solvent each independently include at least one of ethanol, N-methylpyrrolidone, isopropanol, butyl acetate, N,N-dimethylformamide, tetrahydrofuran, toluene, dimethyl sulfoxide, cyclohexane, acetone and pyridine, preferably isopropanol; The mass ratio of the lithium manganese iron phosphate material to the first solvent is 1:3~5; The mass ratio of the hindered amine light stabilizer to the second solvent is 1:40~60; The first temperature is 25 ℃~100 ℃, preferably 75 ℃~85 ℃; The temperature of the second mixing is 50 ℃ to 100 ℃, preferably 89 ℃ to 91 ℃; The second mixing time is 20 min to 50 min.

8. A positive electrode slurry, characterized in that, include: Organic solvents; Adhesive; Conductive agents, including zero-dimensional conductive agents and one-dimensional / two-dimensional conductive agents; And the positive electrode material as described in any one of claims 1 to 7, wherein, based on the total mass of the conductive agent, 60% to 80% of the zero-dimensional conductive agent is distributed on the surface of the first positive electrode material particles in the positive electrode material.

9. The positive electrode slurry according to claim 8, characterized in that, At least one of the following conditions must be met: The adhesive includes PVDF; The conductive agent includes at least one of Super P, acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon fiber, preferably at least one of a mixture of Super P and carbon nanotubes or a mixture of Super P and graphene. The organic solvent includes N-methylpyrrolidone.

10. A method for preparing the positive electrode slurry according to claim 8 or 9, characterized in that, include: The first positive electrode material particles, the first binder, the first conductive agent and the first organic solvent are mixed to obtain the first slurry; The first slurry, the second positive electrode material particles, the second binder, the second conductive agent, and the second organic solvent are mixed to obtain the positive electrode slurry; The mass ratio of the first conductive agent to the second conductive agent is not less than 1:

1.

11. The method according to claim 10, characterized in that, At least one of the following conditions must be met: The first conductive agent is a zero-dimensional conductive agent, selected from at least one of Super P, acetylene black, and Ketjen black; The second conductive agent is a one-dimensional / two-dimensional conductive agent, selected from at least one of carbon nanotubes, graphene, and carbon fibers; The first organic solvent and the second organic solvent each independently comprise N-methylpyrrolidone; The first adhesive and the second adhesive each independently include PVDF; Based on the total mass of the positive electrode slurry, the total mass percentage of the first binder and the second binder is 0.8% to 2%. Based on the total mass of the first adhesive and the second adhesive, the mass percentage of the first adhesive is 50% to 100%; Based on the total mass of the positive electrode slurry, the total mass percentage of the first conductive agent and the second conductive agent is 1.5% to 3.5%. Based on the total mass of the first conductive agent and the second conductive agent, the mass percentage of the first conductive agent is 50% to 90%, preferably 70% to 80%.

12. A positive electrode plate, characterized in that, It includes a positive current collector and a positive electrode dressing layer disposed on at least one side surface of the positive current collector, the positive electrode dressing layer comprising the positive electrode material according to any one of claims 1 to 4, or comprising a coating formed after drying the positive electrode slurry according to any one of claims 6 to 9.

13. A lithium-ion battery, characterized in that, It includes the positive electrode material according to any one of claims 1 to 4, the coating formed after drying the positive electrode slurry according to any one of claims 6 to 9, or the positive electrode sheet according to claim 12.

14. An electrical appliance, characterized in that, The cathode material includes any one of claims 1 to 4, the coating formed after drying the cathode slurry according to any one of claims 6 to 9, the cathode sheet according to claim 12, or the lithium-ion battery according to claim 13.

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