A positive electrode material, a preparation method thereof, a pole piece, a battery, and an electrical device

Abstract

The application provides a positive electrode material and a preparation method thereof, a pole piece, a battery and an electrical equipment, and relates to the technical field of lithium batteries. The positive electrode material is a core-shell composite structure in which lithium iron manganese phosphate is taken as a core and a dopant coating layer is coated on the outer surface of the lithium iron manganese phosphate; the dopant coating layer comprises an alloy material and an ester-based quaternary ammonium salt; the alloy material is Fe y Si 1‑y alloy, wherein 10>y>1. The application coats the positive electrode material with the dopant coating layer composed of the Fe y Si 1‑y alloy, so that the performance and safety of the positive electrode material under low-temperature conditions are improved, the cycle stability and electrochemical performance of the material are enhanced, and a new solution is provided for the development of lithium ion battery technology.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to a cathode material and its preparation method, an electrode sheet, a battery, and electrical equipment. Background Technology

[0002] Lithium-ion batteries, as a highly efficient and environmentally friendly energy storage system, have become an indispensable component of modern electronic devices and electric vehicles. Their core advantages lie in their high energy density, long cycle life, and excellent safety, making them stand out among numerous energy storage technologies. The working principle of lithium-ion batteries is based on the insertion and extraction of lithium ions between the positive and negative electrodes. The positive electrode material, as a key component of the battery, directly determines the overall performance of the battery, including key indicators such as energy density, cycle life, safety, and low-temperature performance.

[0003] Among existing lithium-ion battery cathode materials, lithium manganese iron phosphate (LiMnFePO4) has attracted much attention due to its unique olivine structure. This material, by introducing manganese into lithium iron phosphate, theoretically possesses higher energy density potential. However, in practical applications, LiMnFePO4 suffers from poor conductivity, a characteristic that limits its performance in batteries. Specifically, the poor conductivity leads to low charge transfer efficiency during charging and discharging, thus affecting the battery's cycle performance and causing rapid capacity decay after multiple charge-discharge cycles.

[0004] Furthermore, lithium manganese iron phosphate cathode materials also suffer from a significant chemical stability issue. Manganese ions are prone to disproportionation during battery charging and discharging, a reaction that causes the material's crystal structure to gradually collapse. This structural instability not only further exacerbates the deterioration of battery cycle performance but may also trigger internal short circuits and other safety hazards, thus threatening battery safety. These problems, to some extent, limit the widespread application of lithium manganese iron phosphate materials in high-performance lithium-ion batteries.

[0005] In summary, existing lithium manganese iron phosphate (LFP) cathode materials face numerous challenges in practical applications. Their poor conductivity leads to insufficient battery cycle performance, while the disproportionation reaction of manganese ions reduces the material's structural stability, thus affecting battery safety. These problems make LFP materials unable to meet the current market's high demands for lithium-ion batteries in terms of energy density, cycle life, and safety, necessitating technological innovation to address these issues.

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

[0007] The purpose of this invention is to provide a cathode material and its preparation method, electrode sheet, battery, and electrical equipment. The cathode material not only improves the performance and safety of lithium manganese iron phosphate under low temperature conditions, but also enhances the cycle stability and electrochemical performance of lithium manganese iron phosphate, providing a new solution for the development of lithium-ion battery technology.

[0008] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0009] In a first aspect, the present invention provides a cathode material, wherein the cathode material is a composite structure;

[0010] The cathode material is a core-shell composite structure with lithium manganese iron phosphate as the core and a dopant coating layer covering the outer surface of the lithium manganese iron phosphate.

[0011] The dopant coating layer includes alloy materials and ester-based quaternary ammonium salts;

[0012] The alloy material is Fe. y Si 1-y Alloy, where 1 > y ≥ 0.1.

[0013] In an optional embodiment, the dopant coating layer accounts for 0.1 wt% to 5 wt% of the mass fraction of the cathode material.

[0014] In an optional embodiment, the dopant coating layer further includes an organosilicon resin.

[0015] In an optional embodiment, the weight parts of each component in the dopant coating layer are:

[0016] 65 to 85 parts of alloy material;

[0017] 15 to 35 parts of silicone resin;

[0018] 10 to 30 parts of ester-based quaternary ammonium salt.

[0019] In an optional embodiment, in the alloy material, 0.3 ≥ y ≥ 0.1; and / or,

[0020] The average particle size of the alloy material is 5 nm to 30 nm; and / or,

[0021] The thickness of the dopant coating layer is 1 nm to 10 nm.

[0022] Secondly, the present invention provides a method for preparing a cathode material as described in any of the foregoing embodiments, comprising:

[0023] S1. Iron powder and silicon powder are mixed, and then subjected to ball milling, pressing and molding, and first sintering to obtain alloy material;

[0024] S2. The alloy material and lithium manganese iron phosphate are ball-milled, pressed, and sintered to obtain the core material.

[0025] S3. The ester-based quaternary ammonium salt particles are added to a solution of organosilicon resin for mixing to obtain a mixed slurry; the mixed slurry is sprayed onto the surface of the core material and then subjected to a third sintering treatment to obtain a positive electrode material.

[0026] In an optional embodiment, the mixing process is a stirring mixing process; and / or,

[0027] The mixing process shall be carried out for no less than 1 hour; and / or,

[0028] The stirring and mixing speed is 300 r / min to 400 r / min; and / or,

[0029] The ball milling treatment time is 2 to 8 hours; and / or,

[0030] The sintering temperature of the first sintering treatment is 800℃~1200℃; and / or,

[0031] The sintering time for the first sintering treatment is 2 to 4 hours; and / or,

[0032] The sintering temperature for the second sintering treatment is 700℃~1000℃; and / or,

[0033] The sintering time for the second sintering treatment is 1 hour to 2 hours; and / or

[0034] The sintering temperature of the third sintering treatment is 50℃~120℃; and / or,

[0035] The sintering time for the third sintering treatment is 1 to 2 hours.

[0036] Thirdly, the present invention provides an electrode sheet comprising a positive electrode material as described in any of the foregoing embodiments; or a positive electrode material prepared by the method for preparing the positive electrode material as described in any of the foregoing embodiments.

[0037] Fourthly, the present invention provides a battery comprising the electrode as described in the foregoing embodiments.

[0038] Fifthly, the present invention provides an electrical device including a battery as described in the foregoing embodiments.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The beneficial effects of this application are mainly reflected in the following aspects:

[0041] Fe y Si 1-y As a material with a negative temperature coefficient, the alloy exhibits significant impedance characteristics at low temperatures. This characteristic can effectively mitigate the decline in charge-discharge performance of lithium manganese iron phosphate at low temperatures, thus maintaining the material's cycle performance while ensuring its activity at low temperatures, thereby improving the material's safety. Furthermore, Fe... y Si 1-y Doping of alloys increases the interlayer spacing, facilitating ion shuttle movement and thus improving cycle stability and rate performance. Simultaneously, due to the inherent magnetic properties of layered oxide cathode materials, Fe... y Si 1-y Doping the alloy can also weaken the material's magnetism, lower its Curie temperature, and further improve its low-temperature performance and safety.

[0042] During battery cycling, oxygen atoms may escape, Fe y Si 1-y The alloy can effectively trap these escaping oxygen atoms. This reduces the risk of thermal runaway in the battery, further improving battery safety.

[0043] This invention provides an ester-based quaternary ammonium salt on the surface of the cathode material, which has a certain degree of softness and smoothness, thereby improving the flexibility of the coating layer and reducing the rigidity of the cathode material. Moreover, the -COO- contained in the ester-based quaternary ammonium salt exhibits polyanionic properties after absorbing water, which makes the coating layer have a certain degree of adhesion, improves the peeling force of the electrode, and improves the electrochemical performance of the battery.

[0044] In summary, this application is approved by Fe y Si 1-y The doping of the alloy to form a dopant coating not only improves the performance and safety of the cathode material under low-temperature conditions, but also enhances the material's cycle stability and electrochemical performance, providing a new solution for the development of lithium-ion battery technology. Attached Figure Description

[0045] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0046] Figure 1 This is a schematic diagram of the structure of the cathode material in the embodiments of this application;

[0047] Figure 2 This is a schematic flowchart of the preparation method of the positive electrode material in the embodiments of this application.

[0048] Figure 3 This is a schematic diagram of SEM characterization of the cathode material in the embodiments of this application.

[0049] Explanation of key component symbols: 100 - cathode material; 1 - lithium manganese iron phosphate; 2 - doped coating layer. Detailed Implementation

[0050] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0051] refer to Figure 1 This application provides a cathode material with a composite structure. The cathode material is a core-shell composite structure with lithium manganese iron phosphate as the core and a dopant coating layer covering the outer surface of the lithium manganese iron phosphate. The dopant coating layer includes an alloy material and ester-based quaternary ammonium salt particles. The alloy material is Fe. y Si 1-y Alloy, where 1 > y ≥ 0.1.

[0052] The cathode material particles described above have a composite structure. The composite structure of the material includes:

[0053] (1) Lithium manganese iron phosphate core (internal core): This is the main part of the cathode material, responsible for storing and releasing lithium ions. It is the source and destination of lithium ions during the charging and discharging process of the battery.

[0054] (2) Dopant coating layer (outer layer): This is a layer of material covering the outer surface of lithium manganese iron phosphate. Its function is to improve the performance of lithium manganese iron phosphate, such as improving stability, safety and electrochemical performance.

[0055] The above-mentioned alloy materials (Fe) y Si 1-y Alloy): This is the key component in the doped coating layer, where the value of y is in the range of 1>y≥0.1, indicating that the ratio of iron (Fe) and silicon (Si) can vary within a certain range.

[0056] For example, y can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, etc. Fe y Si 1-y The alloy can be Fe 0.2 Si0.8 alloy.

[0057] In a preferred embodiment, the ester-based quaternary ammonium salt, i.e., the ester-based quaternary ammonium salt, may be selected from at least one of the following: bispalmitoylcarboxyethylhydroxyethylmethylammonium salt, bistallow ester-hydroxyethylmethyl methyl sulfate ammonium salt, bisoil ester-hydroxyethylmethyl sulfate ammonium salt, biscoco ester-hydroxyethylmethyl sulfate ammonium salt, bisaliphatic alkyl ethyl ester-hydroxyethylmethyl sulfate ammonium salt, octadecyl diester-based quaternary ammonium salt, methyl diisopropanolamine ester-based quaternary ammonium salt, triethanolamine ester-based quaternary ammonium salt, and imidazoline ester-based quaternary ammonium salt; most preferably, the ester-based quaternary ammonium salt may be octadecyl diester-based quaternary ammonium salt.

[0058] In the core-shell composite structure, lithium manganese iron phosphate serves as the core, and the dopant coating layer serves as the shell, forming a core-shell structure that helps improve the overall performance of the material.

[0059] It should be noted that Fe y Si 1-y The alloy is a negative temperature coefficient material, exhibiting high impedance at low temperatures. This can alleviate and compensate for the decline in charge-discharge performance of lithium manganese iron phosphate at low temperatures, thus ensuring the material's activity at low temperatures while maintaining its cycle performance and improving its safety. On the other hand, Fe... y Si 1-y Doping of alloys can increase the interlayer spacing, facilitating ion shuttle movement and improving cycle and rate performance. Furthermore, layered oxide cathode materials possess a certain degree of magnetism, but Fe... y Si 1-y Doping of alloys can weaken the magnetism of materials, lower the Curie temperature, and improve low-temperature performance and safety.

[0060] Furthermore, oxygen atoms are released during battery cycling. The positive electrode material provided in this embodiment, Fe... y Si 1-y Alloys can capture escaping oxygen atoms, reducing the risk of thermal runaway in batteries and further improving battery safety.

[0061] It should be noted that ester-based quaternary ammonium salts have a certain degree of softness and smoothness, which can improve the flexibility of the coating layer and reduce the rigidity of the alloy material coating. Moreover, the -COO- contained in ester-based quaternary ammonium salts exhibits polyanionic properties after absorbing water, which makes the coating layer have a certain degree of viscosity, improves the tightness of the cathode material coating, and improves the electrochemical performance of the battery.

[0062] In summary, through this structure and processing method, the cathode material provided in this application embodiment can effectively improve the performance of lithium-ion battery cathode materials, especially the performance under low temperature conditions, while enhancing the cycle stability and safety of the material, thereby extending the battery's service life and improving its applicability in various environments.

[0063] In some embodiments, the dopant coating layer accounts for 0.1 wt% to 5 wt% of the mass fraction of the cathode material. For example, it can be 0.1 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, etc.

[0064] Furthermore, the dopant coating layer also includes organosilicon resin.

[0065] In the doped coating layer, Fe y Si 1-y Alloy particles and ester-based quaternary ammonium salt particles are attached to the network structure of organosilicon resin.

[0066] It should be noted that silicone resins possess excellent thermal stability, good waterproofing, good film-forming properties, and adhesion, enabling them to form uniform, hard, and tough films on the surface of lithium manganese iron phosphate. Furthermore, the combined use of ester-based quaternary ammonium salts and silicone resins allows for physical interactions through intermolecular forces. Ester-based quaternary ammonium salts contain ester groups and quaternary ammonium groups, while silicone resins contain silicon-oxygen bonds and organic groups. The polar groups (quaternary ammonium ion portion) of the ester-based quaternary ammonium salt can exhibit weak electrostatic interactions with some polar portions of the silicone resin (such as the oxygen atoms in the silicon-oxygen bonds); simultaneously, van der Waals forces also exist between the long carbon chain portion of the ester-based quaternary ammonium salt and the organic groups of the silicone resin.

[0067] As mentioned above, organosilicon resin is a polymer compound that mainly consists of a silicon-oxygen bond (Si-O) skeleton and also contains organic groups (such as methyl, phenyl, etc.).

[0068] Organosilicon resins possess excellent electrical insulation and chemical stability. By incorporating organosilicon resins into the dopant coating layer, side reactions between the cathode material and the electrolyte can be reduced, thereby improving the electrochemical performance of the battery. During high-temperature or long-term cycling, organosilicon resins can form a stable coating layer, protecting the cathode material's structure from damage and enhancing its thermal and mechanical stability. Furthermore, organosilicon resins exhibit good thermal stability at high temperatures, reducing safety risks caused by thermal runaway and improving battery safety.

[0069] During solid-state sintering, the silicone resin softens upon heating, allowing it to uniformly coat the surface of the active material particles, forming a smooth coating layer. The silicone resin can fill any voids that may be created by the alloy coating layer, further stabilizing the electrolyte interface and reducing interfacial side reactions. During battery cycling, the silicone resin helps capture oxygen atoms escaping from the cathode material, reducing the risk of thermal runaway.

[0070] Ester-based quaternary ammonium salts and organosilicon resins can interact physically through intermolecular forces. Ester-based quaternary ammonium salts contain ester groups and quaternary ammonium groups, while organosilicon resins contain silicon-oxygen bonds and organic groups. The polar groups (quaternary ammonium ion moiety) of the ester-based quaternary ammonium salt can have weak electrostatic interactions with some polar parts of the organosilicon resin (such as the oxygen atoms in the silicon-oxygen bonds); simultaneously, van der Waals forces also exist between the long carbon chain moiety of the ester-based quaternary ammonium salt and the organic groups of the organosilicon resin.

[0071] In summary, the addition of silicone resin to the dopant coating layer in this embodiment brings several advantages: First, it effectively improves the battery's cycle life by reducing side reactions; second, the uniform coating layer reduces direct contact between the electrolyte and lithium manganese iron phosphate, lowering irreversible electrolyte decomposition and thus improving the battery's charge-discharge efficiency; furthermore, the addition of silicone resin enhances the thermal stability of the cathode material under high-temperature conditions, reducing the risk of thermal runaway; finally, by capturing escaped oxygen atoms, silicone resin helps prevent the increase of internal pressure in the battery, significantly improving battery safety. These improvements not only enhance the electrochemical performance and cycle stability of the cathode material but also play a crucial role in improving the overall performance and reliability of lithium-ion batteries.

[0072] In some embodiments, the weight parts of each component in the dopant coating layer include:

[0073] The alloy material is 65 to 85 parts by weight; for example, the weight of the silicone resin can be 65, 70, 75, 80, 85, etc.

[0074] The amount of the silicone resin is 15 to 35 parts. For example, the weight parts of the silicone resin can be 15, 20, 25, 30, 35, etc.

[0075] The ester-based quaternary ammonium salt is present in quantities of 10 to 30 parts. For example, the weight percentage of the ester-based quaternary ammonium salt can be 10, 20, 25, 30, etc.

[0076] Furthermore, in the alloy material, 0.3 ≥ y ≥ 0.1.

[0077] Furthermore, the alloy material is in granular form; and the average particle size of the alloy material particles is 5nm to 30nm. For example, the average particle size of the alloy material particles can be 5nm, 8nm, 10nm, 15nm, 20nm, 25nm, 30nm, etc.

[0078] Furthermore, the thickness of the dopant coating layer is 1 nm to 10 nm. For example, the thickness of the dopant coating layer can be 1 nm, 2 nm, 3 nm, 5 nm, 7 nm, 8 nm, 9 nm, 10 nm, etc.

[0079] refer to Figure 2 This application provides a method for preparing a cathode material as described in any of the foregoing embodiments, comprising:

[0080] Step S1: Mix iron powder and silicon powder, and then process them through ball milling, pressing and molding, and first sintering to obtain alloy material.

[0081] The above steps involve mixing iron powder and silicon powder, and then using ball milling to achieve uniform mixing and refinement of the powder.

[0082] Ball milling is a mechanical alloying technique that promotes the uniform distribution of alloying elements. Next, the mixed powder is pressed into a shape suitable for sintering. Finally, through a first sintering process, the alloy material is solidified, resulting in an alloy material whose composition and structure meet design requirements.

[0083] Ball milling ensures a uniform distribution of alloying elements, improving the alloy's homogeneity and stability. Pressing and sintering help form alloy materials with specific shapes and sizes, facilitating subsequent processing.

[0084] Specifically, ball milling can be used for ball milling, with the milling time and speed controlled to achieve optimal results. Pressing and molding can be performed using a hydraulic press or pressure press. The first sintering process can be carried out in a furnace, with the sintering temperature and time controlled to obtain the desired alloy properties.

[0085] Step S2: The alloy material and lithium manganese iron phosphate are ball-milled, pressed, and sintered to obtain the core material; Step S3: The ester-based quaternary ammonium salt particles are added to a solution of organosilicon resin for mixing to obtain a mixed slurry; and the mixed slurry is sprayed onto the surface of the core material and then sintered to obtain the cathode material.

[0086] As mentioned above, the uniformly dispersed ester-based quaternary ammonium salt ensures the consistent performance of the final cathode material. Furthermore, the addition of silicone resin helps improve the electrochemical performance and safety of the cathode material.

[0087] The aforementioned silicone resin solution can be a silicone resin solution prepared with an organic solvent; wherein the organic solvent can be ethanol and / or acetone.

[0088] Specifically, a mixer or homogenizer can be used for mixing to ensure a uniform mixture of the ester-based quaternary ammonium salt and the silicone resin. The mixing time and stirring speed can be adjusted to achieve the best dispersion effect.

[0089] The above steps involve spraying a mixed slurry onto the surface of lithium manganese iron phosphate particles to form a uniform dopant coating layer. This layer is then cured through a third sintering process to obtain a cathode material with a core-shell structure, where lithium manganese iron phosphate forms the core and the dopant coating layer forms the shell.

[0090] Among these, spraying technology ensures the uniformity and consistency of the coating layer. The third sintering process helps to solidify the coating layer and improve the structural stability of the cathode material.

[0091] The gas-liquid ratio of the above-mentioned spraying treatment can be 0.2 to 0.5, for example, it can be 0.2, 0.3, 0.4, 0.5, etc., or any other value in the range of 0.2 to 0.5.

[0092] The temperature for the above-mentioned spraying treatment is 70℃~150℃. For example, it can be 70℃, 80℃, 90℃, 130℃, 140℃ or 150℃, or any other value within the range of 70℃~150℃.

[0093] It may also include some necessary steps for preparing cathode materials, such as cooling, grinding, sieving, and iron removal, in order to obtain lithium manganese iron phosphate cathode materials.

[0094] The mixed slurry was sprayed onto the surface of the sintered material by spray drying (100℃, gas-liquid ratio 0.3) and then subjected to low-temperature heat treatment (100℃, 1.5h). Subsequently, the material was cooled, ground, sieved and iron removed to obtain the cathode material.

[0095] Specifically, the mixed slurry can be evenly sprayed onto the surface of lithium manganese iron phosphate particles using spraying equipment (such as a spray gun). The third sintering process can be carried out in a controlled atmosphere furnace to prevent material oxidation or contamination.

[0096] It should be noted that the composite structure of the cathode material is obtained by mixing the active material, alloy material, ester-based quaternary ammonium salt particles, and organosilicon resin and then sintering them. During the solid-phase sintering process, the organosilicon resin softens due to heat, allowing it to uniformly coat the surface of the lithium manganese iron phosphate particles, forming a smooth dopant coating layer, and capable of filling Fe... y Si 1-yThe voids created by the alloy coating can further stabilize the electrolyte interface, effectively reduce interfacial side reactions, and improve the electrochemical performance of the battery.

[0097] Furthermore, the mixing process is a stirring and mixing process.

[0098] Furthermore, the mixing process takes at least 1 hour.

[0099] Furthermore, the stirring and mixing speed is 300 r / min to 400 r / min. For example, the speed can be 300 r / min, 320 r / min, 350 r / min, 380 r / min, 400 r / min, etc.

[0100] Furthermore, the ball milling process takes 2 to 8 hours. For example, the ball milling process can take 2 hours, 4 hours, 6 hours, 8 hours, etc.

[0101] Furthermore, the sintering temperature of the first sintering treatment is 800℃~1200℃. For example, the sintering temperature of the first sintering treatment can be 800℃, 900℃, 1000℃, 1100℃, 1200℃, etc.

[0102] Furthermore, the sintering time for the first sintering treatment is 2 to 4 hours. For example, the sintering time for the first sintering treatment can be 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, etc.

[0103] Furthermore, the sintering temperature of the second sintering treatment is 700℃~1000℃. For example, the sintering temperature of the second sintering treatment can be 700℃, 800℃, 900℃, 1000℃, etc.

[0104] Furthermore, the sintering time for the second sintering treatment is 1 to 2 hours. For example, the sintering time for the second sintering treatment can be 1 hour, 1.5 hours, 2 hours, etc.

[0105] Furthermore, the sintering temperature of the third sintering treatment is 50℃~120℃, such as 50℃, 60℃, 70℃, 80℃, 90℃ or 120℃, or any other value within the range of 50-120℃.

[0106] The sintering time for the third sintering treatment is 1 to 2 hours, such as 1 hour, 1.5 hours, or 2 hours, or any other value within the range of 1 to 2 hours.

[0107] This application provides an electrode sheet comprising a positive electrode material as described in any of the foregoing embodiments; or a positive electrode material prepared by the method described in any of the foregoing embodiments.

[0108] As described above, the electrode is a key component of the battery, composed of multiple key elements to optimize its electrochemical performance and mechanical stability. The current collector, as the basic part of the electrode, typically uses copper foil as the current collector for the negative electrode, which is responsible for collecting and transmitting current. The lithium manganese iron phosphate layer is the core of the electrode, containing the positive lithium manganese iron phosphate. These materials are mixed with conductive agents and binders to form the positive electrode active layer. The positive electrode material is the composite structure positive electrode material in this embodiment, specifically a core-shell structure, with lithium manganese iron phosphate as the core and the outer surface covered with Fe... y Si 1-y The electrode is coated with dopants such as alloys, ester-based quaternary ammonium salts, and organosilicon resins. Conductive agents such as carbon black, graphene, and carbon nanotubes are added to the lithium manganese iron phosphate layer to improve the electrode's conductivity. Binders, such as polyvinylidene fluoride (PVDF), are used to bond the lithium manganese iron phosphate, conductive agents, and current collectors together, ensuring the structural stability of the electrode. In some cases, an additional coating may be applied to the electrode surface to improve its performance, such as reducing side reactions or enhancing electrochemical stability. The current collection region is located at the edge or a specific area of ​​the electrode and is used to connect to external electrodes of the battery, enabling current input and output. The tabs, as extensions of the electrode, are used to connect the electrode to external circuitry of the battery, facilitating current collection and transmission. In some designs, the electrode may contain an insulating layer to prevent internal short circuits. Additionally, auxiliary materials may be included, such as additives to improve electrode performance or temporary materials used in the electrode manufacturing process. These components together constitute the composite structure of the electrode, enabling it to function effectively in the battery.

[0109] This application provides an electrical device, including a battery as described in the foregoing embodiments.

[0110] The term "electrical equipment" as used above can refer to any device that includes a battery as an energy source or component. These devices utilize batteries to power their functions. Examples include, but are not limited to, mobile phones (smartphones), laptops, electric vehicles (EVs), electric bicycles and motorcycles, portable electronic devices, medical devices, home appliances, industrial equipment, wearable devices, energy storage systems, aerospace equipment, emergency lighting, and security systems. These devices demonstrate the diverse and crucial role of batteries in modern life, and the importance of high-performance batteries in improving the performance and safety of these devices.

[0111] The present invention will be further illustrated below with specific embodiments. However, it should be understood that these embodiments are merely for the purpose of more detailed illustration and should not be construed as limiting the present invention in any way.

[0112] Example 1

[0113] The cathode material prepared in this embodiment has a core-shell composite structure.

[0114] The cathode material is a core-shell composite structure with lithium manganese iron phosphate as the core and a dopant coating layer covering the outer surface of the lithium manganese iron phosphate; the dopant coating layer includes Fe. 0.1 Si 0.9 (Alloy material), Octadecyl diester quaternary ammonium salt (octadecyl diester ammonium chloride, model YH-866);

[0115] Experimental methods:

[0116] Step S1: Iron powder and silicon powder are mixed at a molar ratio of 1:9, ball-milled for 2 hours, pressed into shape (8t), sintered at 800℃ for 4 hours, crushed, and screened to obtain 20nm Fe. 0.1 Si 0.9 alloy;

[0117] Step S2, Fe 0.1 Si 0.9 The alloy was mixed with spherical lithium manganese iron phosphate with an average particle size of 5 μm, and ball-milled (2 h) and sintered at a temperature of 700 °C for 1 h to obtain the sintered material.

[0118] Step S3, preparing the mixed slurry: The mixed slurry is prepared by dispersing ester-based quaternary ammonium salt particles in acetone;

[0119] Step S4: A mixed slurry is sprayed onto the surface of the sintered material using a spray drying method (100℃, gas-liquid ratio 0.3), followed by low-temperature heat treatment (70℃, 3h), and then sequentially cooled, ground, and sieved to obtain the cathode material. The coating thickness is 5nm (SEM characterization of the cathode material is referenced). Figure 3 ).

[0120] The dopant coating layer accounts for 1 wt% of the mass fraction of the cathode material. Fe 0.1 Si 0.9 The alloy comprises 70 parts, and the octadecyl diester quaternary ammonium salt comprises 30 parts.

[0121] Example 2

[0122] The cathode material prepared in this embodiment has a core-shell composite structure.

[0123] Experimental methods:

[0124] The preparation method in this embodiment is basically the same as that in Example 1, except that the dopant coating layer accounts for 2% of the mass fraction of the cathode material.

[0125] Example 3

[0126] The cathode material prepared in this embodiment has a core-shell composite structure.

[0127] Experimental methods:

[0128] The preparation method in this embodiment is basically the same as that in Example 1, except that the dopant coating layer accounts for 5% of the mass fraction of the cathode material.

[0129] Example 4

[0130] The cathode material prepared in this embodiment has a core-shell composite structure.

[0131] Experimental methods:

[0132] The preparation method in this embodiment is basically the same as that in Example 1, except that the alloy material is Fe. 0.3 Si 0.7 alloy.

[0133] Example 5

[0134] The cathode material prepared in this embodiment has a core-shell composite structure.

[0135] Experimental methods:

[0136] The preparation method in this embodiment is basically the same as that in Example 1, except that the alloy material is Fe. 0.5 Si 0.5 alloy.

[0137] Example 6

[0138] The cathode material prepared in this embodiment has a core-shell composite structure.

[0139] The cathode material is a core-shell composite structure with lithium manganese iron phosphate as the core and a dopant coating layer covering the outer surface of the lithium manganese iron phosphate; the dopant coating layer includes Fe. 0.1 Si 0.9 Octadecyl diester quaternary ammonium salt (octadecyl diester ammonium chloride, model YH-866), organosilicon resin;

[0140] Experimental methods:

[0141] Step S1: Iron powder and silicon powder are mixed at a molar ratio of 1:9, ball-milled for 2 hours, pressed into shape (8t), sintered at 800℃ for 4 hours, crushed, and screened to obtain 20nm Fe. 0.1 Si 0.9 alloy;

[0142] Step S2, Fe 0.1 Si 0.9The alloy was mixed with spherical lithium manganese iron phosphate with an average particle size of 5 μm, and ball-milled (2 h) and sintered at a temperature of 500 °C for 3 h to obtain the sintered material.

[0143] Step S3: The octadecyl diester quaternary ammonium salt and organosilicon resin are mixed and dispersed in acetone to obtain a mixed slurry;

[0144] In step S4, the mixed slurry is sprayed onto the surface of the sintering material by spray drying (100°C, gas-liquid ratio 0.3) and then subjected to low-temperature heat treatment (70°C, 3h). Subsequently, it is cooled, ground, and sieved to obtain the positive electrode material.

[0145] Among them, Fe 0.1 Si 0.9 The total mass of the alloy, octadecyl diester quaternary ammonium salt and organosilicon resin accounts for 1% of the mass of the cathode material, and the thickness of the coating layer is 5 nm.

[0146] Fe 0.1 Si 0.9 The alloy comprises 70 parts, the octadecyl diester quaternary ammonium salt comprises 30 parts, and the silicone resin comprises 30 parts.

[0147] Example 7

[0148] The cathode material prepared in this embodiment has a core-shell composite structure.

[0149] Experimental methods:

[0150] The preparation method in this embodiment is basically the same as that in Example 6, except that the dopant coating layer accounts for 2% of the mass fraction of the cathode material.

[0151] Example 8

[0152] The cathode material prepared in this embodiment has a core-shell composite structure.

[0153] Experimental methods:

[0154] The preparation method in this embodiment is basically the same as that in Example 6, except that the dopant coating layer accounts for 5% of the mass fraction of the cathode material.

[0155] Example 9

[0156] The cathode material prepared in this embodiment has a core-shell composite structure.

[0157] Experimental methods:

[0158] The preparation method in this embodiment is basically the same as that in Example 6, except that the alloy material is Fe. 0.3 Si 0.7 alloy.

[0159] Example 10

[0160] The cathode material prepared in this embodiment has a core-shell composite structure.

[0161] Experimental methods:

[0162] The preparation method in this embodiment is basically the same as that in Example 6, except that the alloy material is Fe. 0.5 Si 0.5 alloy.

[0163] Comparative Example 1

[0164] The cathode material prepared in this embodiment.

[0165] Experimental methods:

[0166] The preparation method in this embodiment is basically the same as that in Example 1, except that: octadecyl diester quaternary ammonium salt is not added in step S3, no mixed slurry is prepared, and the spraying treatment in step S4 is not performed.

[0167] Comparative Example 2

[0168] The cathode material prepared in this embodiment.

[0169] Experimental methods:

[0170] The preparation method in this embodiment is basically the same as that in Example 1, except that: the alloy material preparation in step S1 is not performed, and the spherical lithium manganese iron phosphate with an average particle size of 5 μm is directly ball-milled (2 h) in step S2 and sintered at a temperature of 700 °C for 1 h to obtain sintered material.

[0171] Horizontal comparison test:

[0172] The positive electrode sheets prepared in the above examples and comparative examples were used to make batteries, and the electrochemical performance of the batteries was tested.

[0173] Test method:

[0174] Battery assembly:

[0175] A. Add PVDF binder to NMP at a mass ratio of 1:8 and stir to obtain a slurry. Then, mix the positive electrode material (prepared from the examples and comparative examples), the conductive agent acetylene black, and the slurry at a mass ratio of 97:1:2 and stir under vacuum until the system is homogeneous to obtain the positive electrode slurry.

[0176] B. The positive electrode slurry is evenly coated onto the positive electrode current collector, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing, it is cut into positive electrode sheets according to the required specifications. The negative electrode active material graphite, conductive agent acetylene black, thickener CMC, and binder SBR are mixed in a mass ratio of 96.2:0.8:1.2:1.8. Then, deionized water is added to the resulting mixture, and the mixture is stirred under vacuum until the system is homogeneous to obtain the negative electrode slurry.

[0177] C. The negative electrode slurry is evenly coated onto the negative electrode current collector, dried at room temperature, and then transferred to an oven for further drying. After cold pressing, it is cut into negative electrode sheets according to the required specifications.

[0178] D. Stack the positive electrode, separator, and negative electrode in sequence to obtain a battery cell after assembly. Place the battery cell assembly into the inner cavity of the battery casing, dry it, and then inject electrolyte into the inner cavity of the battery casing. The electrolyte solvent is ethylene carbonate, and the solute is lithium hexafluorophosphate (1 mol / L). After sealing, settling, formation, and capacity testing, a square lithium-ion battery is obtained.

[0179] The square battery has a capacity of 20Ah, a thickness of 15mm, a width of 119mm, and a height of 208mm.

[0180] The lithium-ion batteries prepared in Examples 1-10 and Comparative Examples 1-2 were subjected to formation and subsequent capacity testing experiments, respectively.

[0181] (1) Test Experiment 1 - Cyclic Test:

[0182] Experimental method: Cyclic life test conditions were 25℃, 1C / 1C 100% DOD cycle.

[0183] (2) Test Experiment 2 - Adhesion Test:

[0184] Experimental Method: Adhesion strength testing is conducted using a universal testing machine, generally requiring at least three parallel samples. Disassemble the electrode assembly, and at the fixed position (ensuring consistency), simultaneously cut 2cm wide pieces of the separator and electrode sheet (two layers of separator and one layer of electrode sheet). Peel off one layer of separator. Apply double-sided tape (2cm wide) to a steel plate, and adhere the electrode sheet to the tape. Roll with a 2kg weight three times. Tear off 5mm of the other layer of separator, apply double-sided tape to the torn separator, and then attach white paper to the tape. Install the steel plate into the lower clamp, and connect the end of the white paper to the upper clamp. Use the equipment software to operate and read the adhesion strength value.

[0185] (3) Test Experiment 3 - Electrode Moisture Test:

[0186] Experimental method: Take about 1g of the electrode and put it into a vial. Use a moisture analyzer to test the moisture content using the Karl Fischer volumetric method. The test temperature is 170℃.

[0187] Table 1. Summary of Test Results

[0188] project Cycle life / times Adhesion strength (N / mm) Moisture content (ppm) of the positive electrode sheet Example 1 2684 8.13 449 Example 2 2713 7.45 435 Example 3 2746 8.33 439 Example 4 2661 7.74 453 Example 5 2681 8.16 438 Example 6 2893 8.71 425 Example 7 2845 8.65 421 Example 8 2943 8.44 411 Example 9 2881 8.52 413 Example 10 2846 8.61 407 Comparative Example 1 2465 6.17 567 Comparative Example 2 2256 7.86 458

[0189] Results analysis:

[0190] (1) As can be seen from the data in Table 1,

[0191] In Examples 1-5, Fe was used in the cathode material. 0.1 Si 0.9 Alloy, Fe 0.5 Si 0.5 Alloy, Fe 0.3 Si 0.7 The combination of alloy materials and octadecyl diester quaternary ammonium salts (ester-based quaternary ammonium salts) exhibits superior cycle performance, adhesion, and low moisture content. This is attributed to the following: doping the alloy material increases the interlayer spacing, facilitating ion shuttle transport and improving the electrochemical performance. Furthermore, lithium manganese iron phosphate cathode materials readily absorb water during preparation, and octadecyl diester quaternary ammonium salts possess the ability to absorb moisture and exhibit polyanionic properties after water absorption, resulting in a certain degree of viscosity in the coating layer. This increases the adhesion between cathode materials, thereby reducing the internal resistance of the battery. Additionally, the combination of the alloy material and octadecyl diester quaternary ammonium salts utilizes the soft and smooth properties of the octadecyl diester quaternary ammonium salts to neutralize Fe. 0.1 Si 0.9 The rigidity of the alloy coating improves the stability of the structure, thereby enhancing the electrochemical performance of the battery.

[0192] (2) In Examples 6-10, Fe was added to the cathode material. 0.1 Si 0.9 Alloy, Fe 0.5 Si 0.5 Alloy, Fe 0.3 Si 0.7 The combined use of alloy (alloy material), octadecyl diester quaternary ammonium salt, and silicone resin improves the battery's cycle performance, adhesion performance, and moisture resistance of the positive electrode. This is likely because silicone resin has excellent thermal stability, good waterproof effect, good film-forming properties, and adhesion, enabling it to form a uniform, hard, and tough film on the surface of lithium manganese iron phosphate. At the same time, the combined use of ester-based quaternary ammonium salt and silicone resin can enhance the connection between positive electrode materials through physical interactions via intermolecular forces, thereby reducing internal resistance and improving the overall performance of the battery.

[0193] (3) Comparing Comparative Example 1 and Examples 1-10, without the octadecyl diester quaternary ammonium salt, the bonding strength and moisture properties of the positive electrode sheet changed significantly, indicating that the octadecyl diester quaternary ammonium salt has a significant impact on the bonding strength and moisture properties of the electrode sheet.

[0194] (4) Compare the proportions and Examples 1-10, without setting Fe. 0.1 Si 0.9 If the battery cycle life decreases significantly due to the alloy, it indicates that Fe... 0.1 Si 0.9 Alloys have a significant impact on the cycle performance of batteries.

[0195] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode material, characterized in that, The cathode material has a composite structure; The cathode material is a core-shell composite structure with lithium manganese iron phosphate as the core and a dopant coating layer covering the outer surface of the lithium manganese iron phosphate. The dopant coating layer includes alloy materials and ester-based quaternary ammonium salts; The alloy material is Fe. y Si 1-y Alloy particles, where 1 > y ≥ 0.1; The cathode material is prepared by the following method: S1. Iron powder and silicon powder are mixed, and then subjected to ball milling, pressing and molding, and first sintering to obtain alloy material; S2. The alloy material and lithium manganese iron phosphate are ball-milled, pressed, and then sintered to obtain the core material; the sintering temperature of the second sintering treatment is 700℃~1000℃. S3. The ester-based quaternary ammonium salt particles are added to a solution of organosilicon resin for mixing to obtain a mixed slurry; and the mixed slurry is sprayed onto the surface of the core material and subjected to a third sintering treatment to obtain a positive electrode material.

2. The cathode material as described in claim 1, characterized in that, The dopant coating layer accounts for 0.1 wt% to 5 wt% of the mass fraction of the cathode material.

3. The positive electrode material as described in claim 1, characterized in that, The weight proportions of each component in the doped coating layer are as follows: 65 to 85 parts alloy material; 15 to 35 parts of silicone resin; 10 to 30 parts of ester-based quaternary ammonium salt.

4. The positive electrode material as described in claim 1, characterized in that, In the alloy material, 0.3 ≥ y ≥ 0.1; and / or, The average particle size of the alloy material is 5 nm to 30 nm; and / or, The thickness of the dopant coating layer is 1 nm to 10 nm.

5. A method for preparing the cathode material according to any one of claims 1 to 4, characterized in that, include: S1. Iron powder and silicon powder are mixed, and then subjected to ball milling, pressing and molding, and first sintering to obtain alloy material; S2. The alloy material and lithium manganese iron phosphate are ball-milled, pressed, and sintered to obtain the core material. S3. The ester-based quaternary ammonium salt particles are added to a solution of organosilicon resin for mixing to obtain a mixed slurry; and the mixed slurry is sprayed onto the surface of the core material and subjected to a third sintering treatment to obtain a positive electrode material.

6. The method for preparing the cathode material as described in claim 5, characterized in that, The mixing process is a stirring mixing process; and / or, The mixing process shall be carried out for no less than 1 hour; and / or, The stirring and mixing speed is 300 r / min to 400 r / min; and / or, The ball milling treatment time is 2 hours to 8 hours; and / or, The sintering temperature of the first sintering treatment is 800℃~1200℃; and / or, The sintering time for the first sintering treatment is 2 hours to 4 hours; and / or, The sintering time for the second sintering treatment is 1 hour to 2 hours; and / or The sintering temperature of the third sintering treatment is 50℃~120℃; and / or, The sintering time for the third sintering treatment is 1 to 2 hours.

7. An electrode sheet, characterized in that, Includes the cathode material as described in any one of claims 1-4; or, the cathode material prepared by the method for preparing the cathode material as described in any one of claims 5-6.

8. A battery, characterized in that, Includes the electrode as described in claim 7.

9. An electrical-related device, characterized in that, Includes the battery as described in claim 8.

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