A lithium ion battery positive electrode material, a positive electrode sheet and a lithium ion battery

Abstract

This application provides a lithium-ion battery cathode material, cathode sheet, and lithium-ion battery, relating to the field of lithium-ion battery technology. The cathode material comprises a first cathode material to which a second cathode material and a third cathode material are added. The first cathode material is lithium manganese iron phosphate nanoparticles; the second cathode material includes one or more combinations of lithium-rich manganese materials, spinel lithium nickel manganese oxide materials, or disordered rock salt phase cathode materials, and the second cathode material is composed of micron-sized secondary spherical particles; the third cathode material includes one or more combinations of ternary cathode materials, layered lithium nickel manganese oxide materials, or spinel lithium manganese oxide materials, and the third cathode material is composed of micron-sized single-crystal particles. The mixing of three different sizes and morphologies of particles—nano, micron-sized secondary spheres, and micron-sized single crystals—allows for a denser packing during electrode fabrication, similar to the aggregate gradation in concrete, significantly improving the compaction density and energy density of the electrode sheet.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a lithium-ion battery cathode material and its preparation method, cathode sheet, and lithium-ion battery. Background Technology

[0002] With the rapid development of electric vehicles and various energy storage systems globally, the market has placed increasingly stringent demands on lithium-ion battery cathode materials in terms of safety, cycle life, and cost control. Lithium iron phosphate (LFP) materials have gained widespread application due to their excellent thermal stability, long cycle life, and relatively low cost, resulting in sustained high-speed growth in market demand. Especially in the energy storage field, it has achieved absolute dominance. In the power battery field, with the maturity of fourth-generation material technology with higher compaction density (powder pressure > 2.6 g / cc), LFP has become the mainstream choice in the commercial vehicle market and is accelerating its penetration in the passenger vehicle market. However, the energy density of LFP materials is approaching its theoretical limit. To further improve the overall performance of battery systems, seeking upgraded alternative materials has become a clear direction for industry development.

[0003] As a natural upgrade to lithium iron phosphate, lithium manganese iron phosphate (LFP) is highly anticipated. Theoretically, it combines the high safety characteristics of LFP with a higher voltage platform, thus significantly improving battery energy density and exhibiting superior low-temperature performance. It has already begun large-scale application in niche markets such as two-wheeled vehicles. However, the inherent defects of this material severely restrict its industrialization process: on the one hand, the olivine structure results in generally low ionic and electronic conductivity, usually requiring the use of nanoparticles to improve it, but this introduces new problems; on the other hand, the dissolution of manganese during charging and discharging directly affects the material's structural stability and cycle life. Due to these limitations, typical LFP materials still lag significantly behind mature LFP materials (high-temperature cycle life >3000 cycles, supports 5C fast charging, and compaction density >2.6g / cc) in key performance indicators such as high-temperature cycle life (approximately 1000 cycles), fast charging capability (typically <3C), and compaction density (<2.4g / cc).

[0004] In existing technologies, two main methods—ion doping and surface coating—are used to improve the electrochemical activity of lithium manganese iron phosphate (LFP) materials and suppress manganese leaching. However, most of these methods only modify the exterior of the LFP material, and are either complex in process, have limited effectiveness, or are expensive. None of these methods fundamentally solve the intrinsic problems of poor conductivity and manganese leaching in LFP materials, making it difficult for them to meet the comprehensive requirements of performance, cost, and reliability for large-scale industrial applications.

[0005] Therefore, there is an urgent need to provide a lithium-ion battery cathode material, cathode sheet, or lithium-ion battery that is simpler, more efficient, and more cost-effective, thereby breaking through the technical bottleneck of lithium manganese iron phosphate materials and meeting the comprehensive requirements of performance, cost, and reliability for large-scale industrial applications. Summary of the Invention

[0006] This application provides a lithium-ion battery cathode material, cathode sheet, and lithium-ion battery, which improves the high-temperature cycle life and storage performance of the battery.

[0007] In a first aspect, this application provides a lithium-ion battery cathode material, comprising: adding a second cathode material and a third cathode material to a first cathode material; the first cathode material is lithium manganese iron phosphate nanoparticles; the second cathode material includes one or more combinations of lithium-rich manganese materials, spinel lithium nickel manganese oxide materials, or disordered rock salt phase cathode materials, and the second cathode material is micron-sized secondary spherical particles; the third cathode material includes one or more combinations of ternary cathode materials, layered lithium nickel manganese oxide materials, or spinel lithium manganese oxide materials, and the third cathode material is micron-sized single crystal particles.

[0008] Through the above scheme, the first cathode material is nanoparticle lithium manganese iron phosphate, serving as a low-cost host and filling medium. The secondary spherical morphology of the second cathode material is beneficial for improving the electrode compaction density, and its low-voltage lithium-rich characteristics can provide an additional lithium source to compensate for cycle lithium loss, directly addressing the cycle life shortcomings of LMFP and lithium manganese oxide. The third cathode material has good structural stability and excellent kinetics of micron-sized single-crystal particles, responsible for improving rate performance and specific capacity, compensating for the intrinsic low conductivity of LMFP. The mixing of three different sizes and morphologies of particles—nano-sized, micron-sized secondary spheres, and micron-sized single crystals—allows for a denser packing during electrode fabrication, similar to the aggregate gradation in concrete, significantly improving the compaction density and energy density of the electrode sheet.

[0009] In one possible design, the voltage of the first positive electrode material is 2.0V-4.3V; the voltage of the second positive electrode material is 2.5V-4.4V; and the voltage of the third positive electrode material is 2.0V-4.6V.

[0010] With the above scheme, since the voltage windows (2.0V-4.3V, 2.5-4.4V, 2.0-4.6V) of the first, second, and third cathode materials partially overlap, it is ensured that they can work together in the same battery. Furthermore, the potential crossover may trigger ion / electron interaction, resulting in a synergistic effect of 1+1+1>3, which makes the performance surpass that of any single material.

[0011] In one possible design, the mass percentages x of the first cathode material, y of the second cathode material, and z of the third cathode material satisfy the following ratio: (0.4-0.9):(0.1-0.5):(0.1-0.5).

[0012] The above scheme ensures that when x ≥ 0.4, a sufficient number of nanoparticles can fill the micron-level gaps, achieving densification. When x ≤ 0.9, it avoids the decrease in packing density caused by an excessive number of nanoparticles (pure nanoparticles have low packing density).

[0013] If x > 0.9, excessive first cathode material may lead to a decrease in compaction density and insignificant improvement in cycle life and rate performance. If x < 0.4, the low-cost advantage is lost, and insufficient nanofilling may result in a decrease in compaction density. When y ≥ 0.1 and z ≥ 0.1, a sufficient micron-scale framework can form a continuous support network, preventing excessive agglomeration of nanoparticles. When y ≤ 0.5 and z ≤ 0.5, excessive micron particles can prevent insufficient nanofilling and the formation of excessively large pores. The formulation range of this scheme falls precisely within the optimal range of "nanofilling micron gaps," achieving the densest packing in particle size distribution theory, thereby significantly improving compaction density.

[0014] In one possible design, the D50 particle sizes of the first, second, and third cathode materials satisfy the following relationship: D50yB = 20.625 - 62.5 × D50xA, and D50zC = 6.625 - 22.5 × D50xA; where D50xA is the D50 particle size of the first cathode material in μm; D50yB is the D50 particle size of the second cathode material in μm; D50zC is the D50 particle size of the third cathode material in μm; and the value of D50xA ranges from 0.05 μm to 0.3 μm.

[0015] Through the above scheme, the D50 particle size of the first cathode material, the second cathode material and the third cathode material have a synergistic relationship, D50yB=20.625-62.5×D50xA, which means that when the D50 particle size of the first cathode material that dominates the filling is determined, the D50 particle size of the second cathode material and the third cathode material are matched accordingly, which can achieve better packing density and ion transport network, thereby realizing high compaction and low impedance electrode sheet.

[0016] In one possible design, when the doping percentages of the second and third cathode materials are the same, the linear relationship between D50 and the mixing percentage of the first, second, and third cathode materials is as follows: D50xA = 0.5x - 0.15; D50yB = 5 + 62.5(y - 0.1); D50zC = 1 + 22.5(x - 0.1). With the above scheme, under the premise y=z, the D50 and mixing percentage of the first, second, and third cathode materials can be directly calculated. This allows the required procurement or synthesis specifications (i.e., D50yB, D50zC) of the second and third cathode materials to be directly calculated based on the expected material cost (determining the ratios y and z) and the performance of the main material (determining D50xA). This makes the performance of the composite cathode material highly predictable and designable, reducing the barriers to research and development and mass production.

[0017] In one possible design, the primary particles of the second cathode material have a particle size of 0.05 μm-1 μm, and the secondary particles have a particle size of 5 μm-30 μm; the chemical formula of the third cathode material is abbreviated as NCM, NM, or LMO; and the D50zC is 1 μm-10 μm. Through the above scheme, the primary particle size of the second cathode material, ranging from 0.05 μm to 1 μm, ensures sufficient reactive surface area, while the secondary particle size, ranging from 5 μm to 30 μm, ensures that the micron-sized secondary spherical structure of the second cathode material provides a robust framework. The D50zC of NCM, NM, or LMO consists of single-crystal particles ranging from 1 μm to 10 μm, enabling the third cathode material to maintain good kinetics while possessing high mechanical strength, effectively buffering cyclic stress, and collectively contributing to long cycle life and high rate performance.

[0018] Secondly, this application provides a lithium-ion battery positive electrode sheet comprising any one of the lithium-ion battery positive electrode materials in the first aspect.

[0019] The beneficial effects of the lithium-ion battery positive electrode provided in the second aspect and the various possible designs of the second aspect can be found in the first aspect and the various possible embodiments of the first aspect, and will not be repeated here. Thirdly, this application provides a lithium-ion battery, including the lithium-ion battery positive electrode sheet of the third aspect.

[0020] The beneficial effects of the lithium-ion battery provided in the third aspect and the various possible designs of the third aspect can be found in the first aspect and the various possible implementations of the first aspect, and will not be repeated here.

[0021] The above description is merely an overview of the technical solutions of the embodiments of this application. In order to better understand the technical means of the embodiments of this application and to implement them in accordance with the contents of the specification, and to make the above and other objects, features and advantages of the embodiments of this application more obvious and understandable, specific implementation methods of this application are described below. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0023] Figure 1 This is a schematic diagram of the structure of the lithium-ion battery cathode material after mixing, as provided in one embodiment of this application.

[0024] Figure 2 This is a comparison diagram of the electrode compaction window of the lithium-ion battery cathode material provided in one embodiment of this application and the lithium-ion battery cathode material in the prior art.

[0025] Figure 3 This is a comparison chart of the rate-specific capacity of the lithium-ion battery cathode material provided in one embodiment of this application and the lithium-ion battery cathode material in the prior art.

[0026] Figure 4 This is a comparison diagram of the discharge voltage plateau of the lithium-ion battery cathode material provided in one embodiment of this application and the lithium-ion battery cathode material in the prior art.

[0027] Figure 5 This is a comparison diagram of the material resistance of a lithium-ion battery cathode material provided in one embodiment of this application and a lithium-ion battery cathode material in the prior art.

[0028] Figure 6 This is a comparison chart of the 45°C cycle performance of the lithium-ion battery cathode material provided in one embodiment of this application and the lithium-ion battery cathode material in the prior art.

[0029] Figure 7 This is a comparison chart of the storage performance of a lithium-ion battery cathode material provided in one embodiment of this application and a lithium-ion battery cathode material in the prior art at 55°C.

[0030] Figure 8 This is a comparison diagram of the electrode compaction window of the lithium-ion battery cathode material provided in this application and the lithium-ion battery cathode material in the prior art.

[0031] Figure 9 This is a comparison chart of the rate-specific capacity of the lithium-ion battery cathode material provided in this application and the lithium-ion battery cathode material in the prior art.

[0032] Figure 10 This is a comparison diagram of the discharge voltage plateau of the lithium-ion battery cathode material provided in this application and the lithium-ion battery cathode material in the prior art.

[0033] Figure 11 This is a comparison diagram of the material resistance of the lithium-ion battery cathode material provided in this application and the lithium-ion battery cathode material in the prior art.

[0034] Figure 12 This is a comparison chart of the 45°C cycle performance of the lithium-ion battery cathode material provided in this application and the lithium-ion battery cathode material in the prior art.

[0035] Figure 13 This is a comparison chart of the storage performance of the lithium-ion battery cathode material provided in this application and the lithium-ion battery cathode material in the prior art at 55°C.

[0036] Explanation of reference numerals in the attached figures: 100, First cathode material; 200, Second cathode material; 300, Third cathode material. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein in the specification of the application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims and drawings of this application are intended to cover non-exclusive inclusion.

[0039] The term "embodiment" as used herein means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of the phrase "embodiment" in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0040] In this article, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists, A and B exist simultaneously, or B exists. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0041] The directional terms appearing in the following description refer to the directions shown in the figures and are not intended to limit the specific structure of this application. For example, in the description of this application, the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the figures. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0042] Furthermore, the terms "first," "second," etc., in the specification and claims of this application or in the aforementioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.

[0043] In the description of this application, unless otherwise stated, "multiple" means two or more (including two), and similarly, "multiple groups" means two or more (including two groups).

[0044] The electrochemical performance of current lithium manganese iron phosphate materials needs to be improved. Furthermore, existing technologies such as ion doping or surface coating cannot fundamentally solve the intrinsic problems of poor conductivity and manganese leaching in lithium manganese iron phosphate materials, making it difficult for them to meet the comprehensive requirements of performance, cost, and reliability for large-scale industrial applications.

[0045] Analysis revealed that poor conductivity, including low electronic conductivity and slow ion diffusion rate, directly impairs battery power and efficiency. Specifically, this manifests as poor rate performance, weak fast charging capability (actual charging speed far below theoretical value), insufficient capacity utilization, reduced energy density (resulting in a significantly lower usable specific capacity than theoretical capacity and reduced battery life), severe polarization, and increased heat generation, which not only reduces energy efficiency but also causes battery temperature rise, accelerates side reactions, and creates safety hazards. Low-temperature performance deteriorates drastically; ion diffusion is already difficult at low temperatures, and materials with poor conductivity exacerbate this, leading to a significant reduction in battery capacity and power at low temperatures. Manganese leaching is a slow and irreversible process that primarily damages battery health and lifespan. Furthermore, poor conductivity and manganese leaching problems are mutually reinforcing. Poor conductivity leads to localized polarization and overheating, which exacerbates manganese leaching. In turn, manganese leaching increases interfacial impedance and structural damage, further worsening conductivity.

[0046] In view of this, embodiments of this application provide a lithium-ion battery cathode material, a cathode sheet, and a lithium-ion battery. The lithium-ion battery cathode material includes: a first cathode material, a second cathode material, and a third cathode material; the first cathode material is lithium manganese iron phosphate nanoparticles, wherein the voltage of the lithium manganese iron phosphate is 2.0V-4.3V; the second cathode material includes one or more combinations of lithium-rich manganese materials, spinel lithium-nickel-manganese oxide materials, or disordered rock salt phase cathode materials, wherein the voltage of the second cathode material is 2.5V-4.4V, and the second cathode material is micro-... The first cathode material consists of micron-sized secondary spherical particles. The third cathode material comprises one or more combinations of ternary cathode materials, layered lithium nickel manganese oxide, or spinel lithium manganese oxide materials. The voltage of the third cathode material is 2V-4.6V, and the third cathode material is a micron-sized single-crystal particle. The first, second, and third cathode materials are physically mixed, with the mass percentages x, y, and z of the first, second, and third cathode materials being (0.4-0.9), y, and z, respectively. Since the first cathode material is nanoparticle lithium manganese iron phosphate, it serves as a low-cost host and filling medium. The secondary spherical morphology of the second cathode material is beneficial for increasing electrode compaction density, and its low-voltage lithium-rich characteristics provide an additional lithium source to compensate for cycle lithium loss, directly addressing the cycle life limitations of LMFP and lithium manganese oxide. The micron-sized single-crystal particles of the third cathode material exhibit good structural stability and excellent kinetics, responsible for improving rate performance and specific capacity, compensating for the intrinsic low conductivity of LMFP. The mixing of particles of three different sizes and morphologies—nano-sized, micron-sized secondary spheres, and micron-sized single crystals—enables a denser packing during electrode fabrication, similar to the gradation of sand and gravel in concrete, significantly improving the compaction density and energy density of the electrode sheet.

[0047] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings.

[0048] Figure 1 This is a schematic diagram of the structure of the lithium-ion battery cathode material after mixing, as provided in this embodiment. Please refer to... Figure 1 This application provides a lithium-ion battery cathode material, including: a first cathode material 100, a second cathode material 200 and a third cathode material 300.

[0049] The first cathode material 100 is lithium manganese iron phosphate nanoparticles, wherein the voltage of lithium manganese iron phosphate is 2.0V-4.3V.

[0050] Lithium manganese iron phosphate (LMFP), with the chemical formula LiMn a Fe 1-a PO4, where 0 <a≤1。

[0051] For example, when a=0.6, lithium manganese iron phosphate (LiMn) 0.6 Fe 0.4 PO4.

[0052] For example, when a=0.5, lithium manganese iron phosphate (LiMn) 0.5 Fe 0.5 PO4.

[0053] The D50 particle size of lithium manganese iron phosphate is 50nm-300nm.

[0054] The second cathode material 200 includes one or more combinations of lithium-rich manganese materials, spinel lithium-nickel-manganese-oxygen materials, or disordered rock salt phase cathode materials, wherein the voltage of the second cathode material 200 is 2.5V-4.4V, and the second cathode material 200 is micron-sized secondary spherical particles.

[0055] Lithium-rich manganese materials are low-voltage lithium-rich manganese, abbreviated as LRMO. Low-voltage lithium-rich manganese specifically refers to lithium-rich manganese materials that have been exempted from high-voltage (>4.5V) activation steps in advance or in actual cycling through technologies such as pre-lithiation, surface modification, and doping with specific elements.

[0056] Spinel lithium nickel manganese oxide (LiMn2O4), abbreviated as LNMO, is a spinel-structured LiMn2O4 with a three-dimensional tunnel structure, allowing lithium ions to diffuse in multiple directions.

[0057] Disordered rock salt phase materials, abbreviated as DRX, are a class of high-capacity oxide cathode materials rich in lithium and transition metals, characterized by a rock salt crystal structure with disordered cation arrangement. In disordered rock salt phase materials, Li... + and transition metal ions (such as Mn³) + / 4+ Ni² + (e.g., ions) are randomly distributed on cation sites, exhibiting a high degree of chemical disorder. This disorder creates entirely new and richer lithium-ion transport pathways.

[0058] The second cathode material 200 comprises lithium-rich manganese materials, spinel lithium-nickel-manganese-oxygen materials, or disordered rock salt phase uniform micron-sized secondary spheres, with primary particles having a diameter of 0.05 μm-1 μm and secondary particles having a diameter of 5 μm-30 μm. This second cathode material 200 can achieve reversible lithium-ion insertion / extraction far exceeding that of traditional layered materials, which is beneficial for improving cycle life. Furthermore, the voltage of the second cathode material 200 is 2.5V-4.4V, which overlaps well with that of LMFP, ternary materials, etc., facilitating the activation of electrochemical synergistic effects in the hybrid system and achieving ion / electron interoperability.

[0059] The third cathode material 300 includes one or more combinations of ternary cathode materials, layered lithium nickel manganese oxide or spinel lithium manganese oxide materials, wherein the voltage of the third cathode material 300 is 2V-4.6V, and the third cathode material 300 is a micron single crystal particle.

[0060] The abbreviation for ternary cathode material is NCM or NMC. Its crystal structure is an α-NaFeO2 type layered structure. Nickel, cobalt and manganese, three transition metal elements, coexist in the same layered lattice. By adjusting the ratio (such as NCM523, NCM622, NCM811), the energy density, lifetime and cost are balanced.

[0061] Layered lithium nickel manganese oxide materials refer to a class of NCM series materials that contain no cobalt or have extremely low cobalt content, and can be abbreviated as NM. Their crystal structure is an α-NaFeO2 type layered structure.

[0062] Lithium spinel manganese oxide (LMO) has a spinel crystal structure and contains only manganese, without nickel or cobalt. It possesses a three-dimensional lithium-ion diffusion channel.

[0063] The third cathode material 300 consists of micron-sized single-crystal particles with a D50zC size of 1-10 μm. These single-crystal particles themselves have high conductivity and form a framework within the electrode, improving overall electron / ion transport. The high specific capacity of the micron-sized single-crystal particle third cathode material 300 can compensate for the capacity-limited limitations of LMFPs, jointly improving energy density.

[0064] The first cathode material 100, the second cathode material 200, and the third cathode material 300 are physically mixed. The mass percentages x of the first cathode material 100, y of the second cathode material 200, and z of the third cathode material 300 are (0.4-0.9): (0.1-0.5): (0.1-0.5). That is, the mass percentage x of the first cathode material 100 is 0.4-0.9, the mass percentage y of the second cathode material 200 is 0.1-0.5, and the mass percentage of the third cathode material 300 is 0.1-0.5.

[0065] In this embodiment, the D50 particle sizes of the first cathode material 100, the second cathode material 200, and the third cathode material 300 satisfy the following relationship: D50yB = 20.625 - 62.5 × D50xA, and D50zC = 6.625 - 22.5 × D50xA; where D50xA is the D50 particle size of the first cathode material 100 in μm; D50yB is the D50 particle size of the second cathode material 200 in μm; D50zC is the D50 particle size of the third cathode material 300 in μm; and the value range of D50xA is 0.05 μm - 0.3 μm.

[0066] In other words, the D50 particle size of the three types of materials (first cathode material 100, second cathode material 200, and third cathode material 300) can have a synergistic relationship, with D50yB = 20.625 - 62.5 × D50xA and D50zC = 6.625 - 22.5 × D50xA. This means that once the D50 particle size of the first cathode material 100, which dominates the filling, is determined, the D50 particle sizes of the second cathode material 200 and the third cathode material 300 will be matched accordingly, achieving better packing density and ion transport network, thereby realizing a high-compact, low-impedance electrode sheet.

[0067] For example, when D50xA is 0.05μm, D50yB = 20.625 - 62.5 × 0.05μm = 17.5μm, and D50zC = 6.625 - 22.5 × 0.05μm = 5.5μm. That is to say, when the D50 particle size of the first cathode material 100 is 0.05μm, the D50 particle size of the second cathode material 200 can be 17.5μm, and the D50 particle size of the third cathode material 300 can be 5.5μm, which can enable the obtained mixed cathode material to achieve better packing density and ion transport network.

[0068] For example, when D50xA is 0.1 μm, the D50 particle size D50yB of the second cathode material 200 can be obtained as 14.375 and the D50 particle size D50zC of the third cathode material 300 as 4.375 using the above formula.

[0069] In some other embodiments, D50xA can also be 0.15μm, 0.2μm, 0.25μm, etc., thereby determining D50yB and D50zC.

[0070] In some embodiments, when the doping percentages of the second cathode material 200 and the third cathode material 300 are the same, the linear relationship between D50 and the mixing percentage of the first cathode material 100, the second cathode material 200 and the third cathode material 300 is as follows: D50xA = 0.5x - 0.15; D50yB = 5 + 62.5(y - 0.1); D50zC = 1 + 22.5(x - 0.1).

[0071] Understandably, given the premise y=z, the D50 and mixing percentage of the first cathode material 100, the second cathode material 200, and the third cathode material 300 can be directly calculated. This allows the required procurement or synthesis specifications (i.e., D50yB, D50zC) of the second cathode material 200 and the third cathode material 300 to be directly calculated based on the expected material cost (determining the ratios y and z) and the performance of the main material (determining D50xA). This makes the performance of the composite cathode material highly predictable and designable, lowering the barriers to research and development and mass production.

[0072] For example, when x is 0.4, we know that y=z=0.3, which corresponds to D50xA being 0.3μm, D50yB being 17.5, and D50zC being 5.5.

[0073] For example, when x is 0.5, we know that y=z=0.25, which corresponds to D50xA being 0.1μm, D50yB being 14.375, and D50zC being 4.375.

[0074] In other embodiments, x can also be 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, etc., and y=z, so the values ​​of y, z, D50xA, D50yB and D50zC can be obtained accordingly.

[0075] Based on the above embodiments, this embodiment also provides a lithium-ion battery cathode material comprising a first cathode material and a second cathode material. The first cathode material is lithium manganese iron phosphate nanoparticles, wherein the voltage of the lithium manganese iron phosphate is 2.0V-4.3V; the second cathode material comprises one or more combinations of lithium-rich manganese materials, spinel lithium nickel manganese oxide materials, or disordered rock salt phase cathode materials, wherein the voltage of the second cathode material is 2.5V-4.4V, and the second cathode material is micron-sized secondary spherical particles; wherein the first cathode material and the second cathode material are physically mixed, and the mass percentage x of the first cathode material : the mass percentage y of the second cathode material is (0.5-0.9):(0.1-0.5).

[0076] The voltage windows (2.0V-4.3V, 2.5-4.4V) of the first and second cathode materials partially overlap, ensuring their synergistic operation within the same battery. The potential overlap may trigger ion / electron interactions, generating a synergistic effect greater than the sum of its parts (1+1>2), resulting in performance exceeding that of any single material. Furthermore, the first cathode material is nanoparticle lithium manganese iron phosphate, serving as a low-cost host and filling medium. The secondary spherical morphology of the second cathode material is beneficial for increasing electrode compaction density, and its low-voltage lithium-rich characteristics provide an additional lithium source to compensate for cycle lithium loss, directly addressing the cycle life limitations of LMFP and lithium manganese oxide. The mixture of nano- and micron-sized secondary spheres with different morphologies, particularly the micron-sized secondary spheres, can compensate for the low compaction density and rapid cycle decay of LMFP. The mixing ratio of (0.5-0.9):(0.1-0.5) enhances the physical framework of the cathode material, improves the cycle life through chemical lithium supplementation, and achieves a better balance between cost and performance with a simpler process. This makes it suitable for applications where rate capability requirements are not extreme but lifespan and cost are important.

[0077] In some embodiments, the D50 particle size D50xA of the first cathode material ranges from 0.05 μm to 0.3 μm; the primary particle size of the second cathode material is 0.05 μm to 1 μm, and the secondary particle size is 5 μm to 30 μm. Through the above scheme, the effective particle size distribution of the second cathode material and the first cathode material can stably achieve the expected compaction density improvement effect.

[0078] Based on the above embodiments, this embodiment also provides a lithium-ion battery cathode material including a first cathode material and a third cathode material.

[0079] The first cathode material is lithium manganese iron phosphate nanoparticles, wherein the voltage of lithium manganese iron phosphate is 2.0V-4.3V; the third cathode material includes one or more combinations of ternary cathode materials, layered lithium nickel manganese oxide or spinel lithium manganese oxide materials, wherein the voltage of the third cathode material is 2V-4.6V, and the third cathode material is micron single crystal particles; wherein the first cathode material and the third cathode material are physically mixed, and the mass percentage x of the first cathode material : the mass percentage z of the third cathode material is (0.5-0.9):(0.1-0.5).

[0080] Through the above embodiments, since the voltage windows (2.0V-4.3V, 2.0-4.6V) of the first and third cathode materials partially overlap, they can work synergistically in the same battery. Furthermore, the potential crossover can trigger ion / electron interactions, resulting in a synergistic effect greater than the sum of its parts (1+1>2), thus surpassing the performance of any single material. The first cathode material is lithium manganese iron phosphate nanoparticles, serving as a low-cost host and filling medium, while the third cathode material is a micron-sized single-crystal high-conductivity material. The physical mixing of (0.5-0.9):(0.1-0.5) directly compensates for the kinetic shortcomings of the first cathode material, significantly improving the battery's fast-charging capability and specific capacity. Simultaneously, the mixing of micron-sized single crystals and nanoparticles also improves compaction to some extent. This solution is suitable for power battery scenarios with high requirements for fast charging and long range.

[0081] In this embodiment, the D50 particle size D50xA of the first cathode material ranges from 0.05μm to 0.3μm; the chemical formula of the third cathode material is abbreviated as NCM, NM, or LMO; and the D50zC ranges from 1μm to 10μm. Through the above scheme, the effective particle size distribution of the third cathode material and the first cathode material can stably achieve the expected fast charging and battery life performance.

[0082] It is understandable that the first, second, and third cathode materials mentioned above can be combined according to actual needs during the actual mixing process.

[0083] Based on the above embodiments, this embodiment also provides a lithium-ion battery positive electrode sheet, which includes the lithium-ion battery positive electrode material in any of the above embodiments.

[0084] Since the structure and beneficial effects of the lithium-ion battery cathode material have been described in detail in the previous embodiments, they will not be repeated here.

[0085] Based on the above embodiments, this embodiment also provides a lithium-ion battery, comprising the lithium-ion battery positive electrode sheet described above. Since the structure and beneficial effects of this lithium-ion battery positive electrode material have been described in detail in the preceding embodiments, they will not be repeated here.

[0086] Example 1 This embodiment provides a lithium-ion battery cathode material, including a first cathode material, a second cathode material, and a third cathode material; wherein the first cathode material is lithium manganese iron phosphate (LMFP), the second cathode material is low-voltage lithium-rich manganese (LRMO), and the third cathode material is a ternary cathode material (NCM), wherein the ratio of lithium manganese iron phosphate material: low-voltage lithium-rich manganese material: ternary cathode material is 0.54:0.23:0.23.

[0087] Comparative Example 1 Comparative Example 1 provides a lithium-ion battery cathode material, including a first cathode material, which is lithium manganese iron phosphate material, and the lithium manganese iron phosphate material accounts for 100% of the cathode material.

[0088] Figure 2 This is a comparison diagram of the compaction density and compaction window of the lithium-ion battery cathode material provided in Example 1 and the lithium-ion battery cathode material in the prior art. Figure 3 This is a comparison chart of the rate-specific capacity of the lithium-ion battery cathode material provided in Example 1 and the lithium-ion battery cathode material in the prior art. Figure 4 This is a comparison chart of the discharge voltage plateau of the lithium-ion battery cathode material provided in Example 1 and the lithium-ion battery cathode material in the prior art. Figure 5 This is a comparison diagram of the material resistance of the lithium-ion battery cathode material provided in Example 1 and the lithium-ion battery cathode material in the prior art. Figure 6 This is a comparison chart of the 45°C cycle performance of the lithium-ion battery cathode material provided in Example 1 and the lithium-ion battery cathode material in the prior art. Figure 7 This is a comparison chart of the 55°C storage performance of the lithium-ion battery cathode material provided in Example 1 and existing lithium-ion battery cathode materials. Please refer to... Figures 2 to 7 , Figures 2 to 7In the figure, A+B+C refers to the performance of each indicator in Example 1, and A refers to the performance of each indicator in Comparative Example 1. It can be seen that the discharge voltage, material resistance, 45℃ cycle performance, and 55℃ storage performance of the lithium-ion battery cathode material in Example 1 are significantly better than those of the lithium-ion battery cathode material in Comparative Example 1.

[0089] Comparative Example 2 This embodiment provides a lithium-ion battery cathode material comprising a first cathode material and a third cathode material, wherein the first cathode material is lithium manganese iron phosphate cathode material (LMFP), the third cathode material is ternary cathode material (NCM), and the ratio of lithium manganese iron phosphate cathode material to the third cathode material is 7:3.

[0090] Figure 8 This is a comparison chart of the compaction density and compaction window of the lithium-ion battery cathode material provided in Comparative Example 2 and the lithium-ion battery cathode material in the prior art. Figure 9 This is a comparison chart of the rate capacity of the lithium-ion battery cathode material provided in Comparative Example 2 and the lithium-ion battery cathode material in the prior art. Figure 10 This is a comparison chart of the discharge voltage plateau of the lithium-ion battery cathode material provided in Comparative Example 2 and the lithium-ion battery cathode material in the prior art. Figure 11 This is a comparison chart of the material resistance of the lithium-ion battery cathode material provided in Comparative Example 2 and the lithium-ion battery cathode material in the prior art. Figure 12 This is a comparison chart of the 45°C cycle performance of the lithium-ion battery cathode material provided in Comparative Example 2 and the lithium-ion battery cathode material in the prior art. Figure 13 This is a comparison chart showing the 55°C storage performance of the lithium-ion battery cathode material provided in Comparative Example 2 and existing lithium-ion battery cathode materials. Please refer to the chart. Figures 8 to 13 , Figures 8 to 13 In the figure, D refers to the performance of each indicator in Comparative Example 1, and D+E1 refers to the performance of each indicator in Comparative Example 2. It can be seen that the discharge voltage, material resistance, 45℃ cycle performance, and 55℃ storage performance of the lithium-ion battery cathode material in Comparative Example 2 are better than those of the lithium-ion battery cathode material in Comparative Example 1.

[0091] Comparative Example 3 This embodiment provides a lithium-ion battery cathode material including a first cathode material and a second cathode material, wherein the first cathode material is lithium manganese iron phosphate cathode material (LMFP), and the second cathode material is low-voltage lithium-rich manganese (LRMO), and the ratio of LMFP to LRMO is 7:3.

[0092] Please refer to Figures 8 to 13 , Figures 8 to 13In the figure, D refers to the performance of each indicator in Comparative Example 1, and D+E2 refers to the performance of each indicator in Comparative Example 3. It can be seen that the discharge voltage, material resistance, 45℃ cycle performance, and 55℃ storage performance of the lithium-ion battery cathode material in Comparative Example 3 are better than those of the lithium-ion battery cathode material in Comparative Example 1.

[0093] Through the embodiments of this application, the overall performance of the system obtained by combining the first cathode material with any second and / or third cathode material is generally superior to that of a single component, especially in terms of compaction density window, high-temperature cycle life, and storage performance. The nanoscale D material mainly acts as a filling medium; the micron-sized single-crystal E1 material is used to improve capacity and rate performance; while the micron-sized secondary spherical E2 material helps to widen the compaction density window and improve cycle stability. The difference in particle size between any two materials forms a "secondary gradation" structure, effectively improving the electrode's compaction density, with the composite effect with low-voltage lithium-rich manganese material being the most prominent. On the other hand, due to the differences in kinetic properties among the three materials, after mixing any two, during charge and discharge, the high-conductivity material can respond to the current first and alleviate polarization, subsequently achieving charge rebalancing through ion migration between different materials. This composite strategy effectively integrates the advantages of different cathode materials in terms of structure and electrochemical performance, producing a synergistic enhancement effect of "1+1>2" on cycle life and storage performance. However, the rate performance and low-temperature performance of LFMP decreased after being combined with low-voltage lithium-rich manganese materials. This is related to the intrinsic characteristics of lithium-rich manganese materials, and may also be due to the fact that lithium-rich manganese materials are more likely to form a high-resistivity interface film on the electrode surface during charging, limiting the overall kinetic performance. In addition, the gas production of LMFP increased significantly after being combined with ternary materials, which may be related to the high activity of ternary materials (especially high-nickel ones).

[0094] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A lithium-ion battery cathode material, characterized in that, include: First cathode material, second cathode material, and third cathode material; The first cathode material is lithium manganese iron phosphate nanoparticles; The second cathode material includes one or more of lithium-rich manganese materials, spinel lithium-nickel-manganese-oxygen materials, or disordered rock salt phase cathode materials, and the second cathode material is micron-sized secondary spherical particles. The third cathode material includes one or more combinations of ternary cathode materials, layered lithium nickel manganese oxide or spinel lithium manganese oxide materials, and the third cathode material is a micron single crystal particle.

2. The lithium-ion battery cathode material according to claim 1, characterized in that, The voltage of the first positive electrode material is 2.0V-4.3V; the voltage of the second positive electrode material is 2.5V-4.4V; and the voltage of the third positive electrode material is 2.0V-4.6V.

3. The lithium-ion battery cathode material according to claim 1, characterized in that, The mass percentages x of the first cathode material, y of the second cathode material, and z of the third cathode material satisfy the following ratio: (0.4-0.9):(0.1-0.5):(0.1-0.5).

4. The lithium-ion battery cathode material according to claim 1, characterized in that, The D50 particle sizes of the first, second, and third cathode materials satisfy the following relationship: D50yB = 20.625 - 62.5 × D50xA, and D50zC = 6.625 - 22.5 × D50xA; Wherein, D50xA is the D50 particle size of the first cathode material, in μm; D50yB is the D50 particle size of the second cathode material, in μm; and D50zC is the D50 particle size of the third cathode material, in μm. Furthermore, the value of D50xA ranges from 0.05μm to 0.3μm.

5. The lithium-ion battery cathode material according to claim 4, characterized in that, When the doping percentages of the second cathode material and the third cathode material are the same, the linear relationship between the D50 of the first cathode material, the second cathode material, and the third cathode material and the mixing percentage is as follows: D50xA = 0.5x - 0.15; D50yB=5+62.5(y-0.1) D50zC = 1 + 22.5(x - 0.1).

6. The lithium-ion battery cathode material according to claim 3, characterized in that, The chemical formula of the second cathode material is abbreviated as LRMO, LNMO or DRX; the particle size of the primary particles is 0.05μm-1μm, and the particle size of the secondary particles is 5μm-30μm. The chemical formula of the third cathode material is abbreviated as NCM, NM, or LMO; D50zC is 1μm-10μm.

7. A positive electrode sheet for a lithium-ion battery, characterized in that, The lithium-ion battery cathode material comprises any one of claims 1 to 6.

8. A lithium-ion battery, characterized in that, It includes the lithium-ion battery positive electrode sheet as described in claim 7.

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