Lithium battery positive electrode material, preparation method thereof and lithium battery

Abstract

The application discloses a lithium battery positive electrode material, a preparation method thereof and a lithium battery, and relates to the technical field of lithium batteries. The preparation method can comprise the following steps: mixing mixed raw materials comprising at least a lithium source, an iron source and a phosphorus source with an ion-conducting sintering aid, so that the ion-conducting sintering aid is uniformly distributed in the mixed raw materials, and a mixture is obtained; and heating and sintering the mixture under an inert atmosphere or a weak reducing atmosphere, so that a self-assembled granular positive electrode material is obtained, wherein the self-assembled granular positive electrode material comprises arranged crystal nuclei and at least a functional interface layer with high lithium ion conductivity filled at the grain boundaries. The preparation method is simple in process and easy to be industrialized, and the prepared self-assembled granular positive electrode material can guarantee the integrity of the particles, so that the cycle stability and the electrochemical performance of the positive electrode material are effectively improved.

Description

Technical Field

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

[0002] For lithium-ion battery cathode materials, increasing their compaction density to achieve higher volumetric energy density is a key aspect of current technological development. Currently, obtaining high compaction density cathode materials generally requires a combination of external mechanical force and high-temperature, high-pressure sintering. After high-temperature, high-pressure sintering, the cathode material forms a hard, blocky material, necessitating energy-intensive mechanical crushing of crystalline silicon and airflow classification to obtain the desired product. This existing process for preparing lithium-ion battery cathode materials easily introduces microcracks on the particle surface, compromising particle integrity and resulting in poor cycle stability and electrochemical performance. Summary of the Invention

[0003] In view of this, embodiments of the present invention provide a lithium battery cathode material, a method for preparing the same, and a lithium battery. The method for preparing the lithium battery cathode material is simple, easy to industrialize, and the self-assembled particulate cathode material prepared can ensure the integrity of the particles, thereby effectively improving the cycle stability and electrochemical performance of the cathode material.

[0004] To achieve the above objectives, in a first aspect, according to embodiments of the present invention, a method for preparing a lithium battery cathode material is provided, comprising: Step 1: Mix a mixed raw material containing at least a lithium source, an iron source and a phosphorus source with an ion-conductive sintering aid, so that the ion-conductive sintering aid is uniformly distributed in the mixed raw material to obtain a mixture; Step 2: Under an inert or weakly reducing atmosphere, the mixture is heated and sintered to obtain a self-assembled particulate cathode material, wherein the self-assembled particulate cathode material includes arranged crystal nuclei and a functional interface layer with high lithium-ion conductivity that is at least filled at the grain boundaries.

[0005] Optionally, the mixed raw materials further include: a carbon source; The crystal nucleus includes an LFP core layer and a carbon layer formed by the carbon source that encapsulates the core layer.

[0006] Optionally, step 1 can be mixed using high-energy ball milling.

[0007] Optionally, the lithium source includes at least one of the following compounds: Li₂CO₃, LiOH H2O, LiNO3 and CH3COOLi.

[0008] Optionally, the iron source includes at least one of the following compounds: FeHPO4 2H2O, FeC2O4 2H₂O, (CH₃COO)₂Fe, FePO₄ 2H2O, FeCl3 6H2O, Fe(NO3)3 9H2O.

[0009] Optionally, the phosphorus source includes at least one of the following compounds: NH4H2PO4, FePO4 2H2O, H3PO4, Na4P2O7 and Na3PO4.

[0010] Optionally, the ion-conductive sintering aid belongs to the ion-conductive borosilicate glass system, wherein the ion-conductive sintering aid includes at least: Li, V, Si, B and O.

[0011] Optionally, the ionic conductive sintering aid accounts for 0.5 wt% to 5.0 wt% of the total mass of the mixture.

[0012] Optionally, the ion-conductive sintering aid includes at least the following oxide precursors: The molar fractions are 15%~25% Li2O, 25%~35% V2O5, 30%~40% SiO2, and 5%~15% B2O3.

[0013] Optionally, step 2 includes: heating and sintering the mixture by gradient heating to 700℃~800℃, and holding at that temperature for 2h~10h.

[0014] Optionally, the gradient heating rate in step 2 is 1℃~5℃.

[0015] Secondly, embodiments of the present invention provide a lithium battery cathode material, wherein the lithium battery cathode material is in the form of self-assembled particles, comprising: The arrangement of crystal nuclei and a functional interface layer with high lithium-ion conductivity, at least filling the grain boundaries.

[0016] Optionally, the functional interface layer also encloses the arranged crystal nuclei.

[0017] Optionally, the particle size of the self-assembled particulate lithium battery cathode material is 0.3 μm to 10 μm.

[0018] Optionally, the crystal nucleus comprises: an LFP core layer and a carbon layer enclosing the core layer.

[0019] Optionally, the functional interface layer includes: an ion-conductive borosilicate glass comprising at least Li, V, Si, B and O.

[0020] Optionally, the compaction density of the lithium battery cathode material is greater than 2.65 g / cm³. 3 .

[0021] Thirdly, embodiments of the present invention provide a lithium battery, comprising: the lithium battery positive electrode material provided in the above embodiments.

[0022] One embodiment of the above invention has the following advantages or beneficial effects: The method for preparing lithium battery cathode materials provided by the embodiments of the present invention involves mixing a mixed raw material containing at least a lithium source, an iron source, and a phosphorus source with an ion-conductive sintering aid, and heating the mixture under an inert or weakly reducing atmosphere. During this process, the ion-conductive sintering aid becomes a liquid phase, wetting the crystal nuclei and grain boundaries of the cathode material formed by the mixed raw material. Capillary forces pull the crystal nuclei closer and rearrange them. In this process, small crystals dissolve and re-precipitate at the necks of the larger particles, thereby self-assembling the loose nanocrystal nuclei into a more dense self-assembled granular cathode material. Compared with the existing technology combining high-pressure pressing, hot pressing sintering, and mechanical pulverization, the technical solution provided by the embodiments of the present invention has a simple process, is easy to industrialize, and the prepared self-assembled granular cathode material can ensure the integrity of the particles, effectively improving the cycle stability and electrochemical performance of the cathode material.

[0023] The further effects of the aforementioned unconventional alternative methods will be explained below in conjunction with specific implementation methods. Attached Figure Description

[0024] The accompanying drawings are provided to better understand the invention and are not intended to unduly limit the scope of the invention. Wherein: Figure 1 This is a schematic diagram of the main process of preparing lithium battery cathode material according to an embodiment of the present invention; Figure 2 This is a cross-sectional schematic diagram of self-assembled particles of lithium battery cathode material according to an embodiment of the present invention.

[0025] Explanation of reference numerals in the attached figures: 10 - Crystal nucleus; 11 - LFP core layer; 12 - Carbon layer; 20 - Functional interface layer. Detailed Implementation

[0026] Lithium iron phosphate (LFP), a commonly used cathode material for lithium-ion batteries, holds a core position in the fields of power batteries and energy storage due to its high safety and low cost. Among these advancements, increasing the high compaction density of lithium iron phosphate (LFP) is one of the key means to achieve higher volumetric energy density in lithium-ion batteries, and it is also a critical bottleneck in the current development of lithium-ion battery technology.

[0027] Currently, the main method for obtaining high-density lithium-ion polymer (LFP) cathodes is a combination of high-pressure pressing, hot-pressing sintering, and mechanical pulverization. Specifically, the required raw materials, such as lithium, iron, phosphorus, and carbon sources, are first mixed and formed into a dense precursor block using a high-pressure pressing machine. Then, this precursor block is sintered at high temperature, with a continuous pressure of several hundred megapascals applied during the sintering process to promote bonding between particles within the precursor block. After sintering, a hard, blocky material is obtained. This hard, blocky material is then mechanically pulverized using high-energy consumption, and the pulverized cathode material is further processed through airflow classification to obtain the final cathode material containing high-density nanoparticles. Current technologies for obtaining high-density, high-density nanoparticles involve complex processes and require various expensive equipment such as high-pressure pressing machines, hot-pressing furnaces, and pulverizers, resulting in high production costs and energy consumption. In addition, mechanical crushing is a destructive process that can easily introduce microcracks on the surface of nanoscale particles. This is especially true for particles with carbon coatings, where mechanical crushing can easily damage the integrity of the carbon coating, thereby impairing the cycle stability and electrochemical performance of the cathode material.

[0028] To address the aforementioned problems in the existing technology, embodiments of the present invention provide a method for preparing lithium battery cathode materials. This method directly prepares high-density, high-ionic-conductivity, and high-performance LFP-containing cathode materials from raw materials in a milder, more efficient, and more economical manner.

[0029] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of the present invention, including various details to aid understanding. These details should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope and spirit of the invention. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0030] It should be noted that, unless otherwise specified, the embodiments of the present invention and the technical features thereof can be combined with each other.

[0031] Figure 1 This diagram illustrates the main process flow of a method for preparing a lithium-ion battery cathode material according to an embodiment of the present invention. Specifically, as shown... Figure 1 As shown, the preparation method of this lithium battery cathode material may include the following steps: Step S101: Mix the mixed raw materials containing at least lithium source, iron source and phosphorus source with an ion-conductive sintering aid, so that the ion-conductive sintering aid is uniformly distributed in the mixed raw materials to obtain a mixture.

[0032] Among them, a mixture of raw materials containing at least lithium, iron and phosphorus sources is the basic raw material for the preparation of LFP.

[0033] Specifically, the lithium source includes at least one of the following compounds: lithium carbonate (Li₂CO₃), lithium hydroxide monohydrate (LiOH). H2O, lithium nitrate (LiNO3), and lithium acetate (CH3COOLi).

[0034] The iron source includes at least one of the following compounds: iron hydrogen phosphate dihydrate (FeHPO4). 2H2O), ferrous oxalate crystals (FeC2O4) 2H2O), ferrous acetate ((CH3COO)2Fe), ferric hydrogen phosphate dihydrate (FePO4) 2H2O), ferric chloride hexahydrate (FeCl3) 6H2O) and ferric nitrate nonahydrate (Fe(NO3)3) It is worth noting that the needle contains an iron source for ferric ions, which can be reduced to ferrous ions by adding reducing agents such as ascorbic acid or glucose.

[0035] The phosphorus source includes at least one of the following compounds: ammonium dihydrogen phosphate (NH4H2PO4), iron hydrogen phosphate dihydrate (FeHPO4). 2H2O), phosphoric acid (H3PO4), sodium pyrophosphate Na4P2O7 and sodium phosphate (Na3PO4).

[0036] The mixed raw materials may also include other materials that enhance the cathode material of lithium batteries, such as carbon nanotubes and carbon sources.

[0037] Preferably, the mixed raw materials further include a carbon source. The presence of this carbon source allows for the coating of the LFP with a carbon layer, which optimizes the conductivity of the LFP, enhances structural stability, and effectively suppresses interfacial side reactions. The carbon source may include at least one of the following materials: glucose, sucrose, starch, citric acid, tartaric acid, ascorbic acid, polymers (such as polyethylene glycol PEG, polyvinyl alcohol PVA, polyvinylpyrrolidone PVP, etc.), resins (such as phenolic resin, epoxy resin, etc.), acetylene black, conductive carbon black, graphene, carbon nanotubes, etc.

[0038] It is worth noting that in step S101, the raw materials required for preparing LFP, such as lithium source, iron source and phosphorus source, can be mixed evenly first, and then the ion-conductive sintering aid can be mixed into the mixed raw materials. Alternatively, the raw materials such as lithium source, iron source and phosphorus source can be mixed evenly together with the ion-conductive sintering aid.

[0039] In addition, all the above-mentioned raw materials, such as lithium source, iron source, phosphorus source and ion-conductive sintering aid, are solid, therefore, the mixture in step S101 is also solid.

[0040] More specifically, in order to ensure the uniform distribution of the ion-conductive sintering aid, a specific implementation of step S101 may include mixing using high-energy ball milling. High-energy ball milling enables the ion-conductive sintering aid to be uniformly mixed with the raw materials required for forming LFP at the atomic or molecular level. The parameters required for high-energy ball milling, such as milling rate and time, can be adjusted according to actual needs.

[0041] The mass ratio of the mixed raw materials, including lithium source, iron source, phosphorus source and carbon source, can be selected from the mass ratio used in the existing LFP preparation process, and is not limited here.

[0042] Step S102: Under an inert atmosphere or a weakly reducing atmosphere, the mixture is heated and sintered to obtain a self-assembled particulate cathode material, wherein the self-assembled particulate cathode material includes arranged crystal nuclei and a functional interface layer with high lithium-ion conductivity that is at least filled at the grain boundaries.

[0043] Inert atmosphere generally refers to a gas that does not react with the mixture obtained in step S101, such as N2 or Ar. A weakly reducing atmosphere may be an inert gas mixed with a small amount of H2. It is worth noting that the oxygen content in an inert atmosphere or a weakly reducing atmosphere is generally less than 50 ppm.

[0044] The crystal nucleus can be an LFP-formed nucleus independently, or it can be a combination of an LFP core layer and a carbon layer encapsulating the core layer. For example, Figure 2 A schematic diagram of the cross-sectional shape of a self-assembled granular cathode material is shown. Figure 2 As shown, a functional interface layer 20 is filled between the crystal nuclei 10 formed by the combination of the LFP core layer 11 formed by LFP and the carbon layer 12 that wraps the LFP core layer 11, and the functional interface layer 20 also wraps around the self-assembled crystal nuclei 10.

[0045] The functional interface layer 20 is formed by an ion-conductive sintering aid. In addition to its ion conductivity, it can also reduce the interfacial distance between adjacent crystal nuclei, thereby increasing the density of the crystal nuclei and achieving the purpose of improving the compactness of the self-assembled particulate cathode material.

[0046] Specifically, in step S102, during the heating and sintering process, on the one hand, the above-mentioned mixed raw materials react to generate lithium iron phosphate (LFP) crystal nuclei. It can be understood that, in the case where the mixed raw materials contain a carbon source, the crystal nuclei generated by the reaction of the mixed raw materials are an LFP core layer and a carbon layer that surrounds the LFP core layer. On the other hand, during the heating and sintering process, after the heating temperature reaches a certain temperature, the ion-conductive sintering aid melts and becomes liquid. Since the ion-conductive sintering aid and the mixed raw materials are uniformly mixed at the atomic or molecular level in step S101, the liquid ion-conductive sintering aid is uniformly distributed and can wet the crystal nuclei. Through the strong capillary force of the liquid ion-conductive sintering aid, these crystal nuclei are pulled closer and rearranged. Through the dissolution-reprecipitation mechanism, small crystals dissolve and preferentially reprecipitate at the particle neck, thereby reorganizing the loose crystal nuclei into a dense accumulation of crystal nuclei. During the cooling process, the liquid ion-conductive sintering aid is re-solidified, "welding" and "shaping" the rearranged and stacked crystal nuclei into dense, highly spherical micron-sized secondary particles, i.e., self-assembled particulate cathode materials. In this embodiment of the invention, by introducing an ionicly conductive sintering aid, an interaction can be achieved with the crystal nucleus, which greatly reduces the grain boundary spacing between adjacent crystal nuclei. In other words, the ionicly conductive sintering aid can provide a driving force that minimizes the surface energy for the stacking of crystal nuclei, enabling in-situ self-assembly of crystal nuclei and directly obtaining self-assembled granular cathode materials of the required size without subsequent mechanical crushing.

[0047] In addition, by controlling the heating and sintering, the size of the self-assembled granular cathode material can be effectively controlled, and the size of the self-assembled granular cathode material can be relatively uniform, thus ensuring process stability.

[0048] The above step S102 can be carried out in a conventional atmosphere-protected kiln (such as a roller kiln to ensure excellent temperature uniformity).

[0049] In summary, the method for preparing lithium-ion battery cathode materials provided by this invention involves mixing a mixture of raw materials containing at least lithium, iron, and phosphorus sources with an ion-conductive sintering aid. During the heating process in an inert or weakly reducing atmosphere, the ion-conductive sintering aid becomes a liquid phase, wetting the crystal nuclei and grain boundaries of the cathode material formed by the mixed raw materials. Capillary forces pull the crystal nuclei closer together and rearrange them. In this process, small crystals dissolve and re-precipitate at the necks of larger particles, thereby self-assembling the loose nanocrystals into denser, self-assembled granular cathode materials. Compared to existing technologies combining high-pressure pressing, hot-pressing sintering, and mechanical pulverization, the technical solution provided by this invention is simpler, easier to industrialize, and the prepared self-assembled granular cathode material ensures particle integrity, effectively improving the cycle stability and electrochemical performance of the cathode material.

[0050] It is worth noting that the above steps S101 and S102 are generally completed in an environment of normal or near-normal pressure without applying any external mechanical pressure. Therefore, there is no need to add pressurizing equipment for steps S101 and S102, which reduces energy consumption, improves the safety of the lithium battery cathode material preparation process, and reduces technical difficulty.

[0051] As can be seen from the above, in the method for preparing lithium battery cathode material provided in the embodiments of the present invention, ion-conductive sintering aid and heating sintering are the core of obtaining self-assembled particulate cathode material.

[0052] In order to ensure the ionic conductivity and "bonding of crystal nuclei" of ionic conductive sintering aids, the ionic conductive sintering aids selected in this embodiment of the invention belong to the ionic conductive borosilicate glass system, wherein the ionic conductive sintering aids include at least: Li, V, Si, B and O.

[0053] Preferably, the ion-conductive sintering aid comprises at least the following oxide precursors: 15%–25% Li₂O, 25%–35% V₂O₅, 30%–40% SiO₂, and 5%–15% B₂O₃. By selecting these oxide precursors and controlling their molar fractions, it is ensured that the ion-conductive sintering aid can form a low-viscosity, highly wettable liquid state within the sintering temperature window, and can rapidly form a glassy phase and stably accumulate crystal nuclei during cooling. Furthermore, this ion-conductive sintering aid has a higher lattice matching degree with LFP and can form an ion-conducting phase at grain boundaries.

[0054] In addition, by selecting an ion-conductive borosilicate glass system that includes at least Li, V, Si, B and O to form a functional interface layer, not only is the mechanical strength of the secondary particles (i.e., the self-assembled particulate cathode material formed by the combination of stacked crystal nuclei and the functional interface layer) enhanced, but a "highway" is also provided for the rapid shuttle of lithium ions between crystal nuclei, thereby significantly reducing the interface impedance and improving the rate performance of the material.

[0055] For example, the molar fraction of Li2O can be 15%, 18%, 20% or 25%, etc.; the molar fraction of V2O5 can be 25%, 28%, 30%, 32% or 35%, etc.; the molar fraction of SiO2 can be 30%, 32%, 35%, 38% or 40%, etc.; and the molar fraction of B2O3 can be 5%, 8%, 10% or 15%, etc.

[0056] In addition, the ion-conductive sintering aid accounts for 0.5 wt% to 5.0 wt% of the total mass of the mixture (i.e., the mass fraction of the ion-conductive sintering aid is 0.5 wt% to 5.0 wt%), to ensure that the ion-conductive sintering aid is uniformly dispersed between crystal nuclei while controlling the size of the formed self-assembled particulate cathode material. For example, the mass fraction of the ion-conductive sintering aid can be 0.5 wt%, 1.0 wt%, 1.5 wt%, 2.0 wt%, 3.0 wt%, 4.0 wt%, or 5.0 wt%, etc.

[0057] More specifically, for step S102, the specific implementation of the heating sintering may include: heating and sintering the mixture using a gradient temperature increase to 700℃~800℃, and holding at that temperature for 2h~10h. For example, the sintering temperature may be 700℃, 750℃, or 800℃, etc., and the holding time may be 2h, 4h, 5h, 7h, or 10h, etc., to ensure the formation of crystal nuclei and their rearrangement, and to effectively control the particle size of the self-assembled particulate cathode material.

[0058] Preferably, the gradient heating rate in step S102 is generally 1°C to 5°C. For example, the gradient heating rate can be 1°C, 3°C, or 5°C, etc. By controlling the gradient heating rate, it can be ensured that the liquid ion-conductive sintering aid fully wets the crystal nuclei and fills the grain boundaries, thereby reducing the interfacial impedance between the crystal nuclei.

[0059] It is worth noting that during the isothermal stage of the above-mentioned heating and sintering, the process of synthesizing LFP crystal nuclei from mixed raw materials is carried out in synergy with the process of autonomous assembly of LFP crystal nuclei driven by liquid ion-conductive sintering aids.

[0060] In addition, after step S102 above, cooling yields micron-sized self-assembled granular cathode material with high dispersibility and high sphericity. Its particle size distribution is concentrated, and no crushing, grinding or grading process is required.

[0061] In summary, compared with the existing process of "high pressure tableting - hot pressing and sintering - mechanical crushing", the technical solution provided by the present invention is reduced to two key steps: "mixing - heating and sintering". This not only greatly shortens the production cycle, but also saves investment in expensive equipment such as tablet presses, hot press furnaces, and air jet mills, thereby reducing production costs and unit energy consumption by at least 30% to 50%.

[0062] In addition, since the technical solution provided by the embodiments of the present invention completely eliminates all mechanical crushing processes, it fundamentally avoids damage to the carbon layer and crystal structure, ensuring the structural integrity of the self-assembled granular lithium battery cathode material, thereby helping to achieve higher initial coulombic efficiency and longer cycle life.

[0063] In particular, the preparation method provided in this embodiment of the invention can form crystal nuclei with carbon layers during the heating and sintering process. At the same time, the crystal nuclei rearrange and can be wrapped by a functional interface layer formed by an ion-conductive sintering aid. This not only ensures the compactness of the self-assembled particulate cathode material, but also constructs a transport channel between crystal nuclei through the functional interface layer, giving the cathode material excellent rate performance.

[0064] Furthermore, embodiments of the present invention also provide a lithium battery cathode material, which is a self-assembled granular material. Specifically, as shown in the example... Figure 2 As shown, the lithium battery cathode material may include: arranged crystal nuclei 10 and a functional interface layer 20 with high lithium-ion conductivity, which is at least filled at the grain boundaries.

[0065] The self-assembled granular material has high crystal density 10 and the functional interface layer 20 can provide a fast channel for lithium ions, thereby enabling the lithium battery cathode material to transport lithium ions quickly, reducing interface impedance and improving the rate performance of the material.

[0066] Among them, the crystal nucleus can be an LFP crystal nucleus formed independently, or it can be a crystal nucleus such as... Figure 2 As shown, the crystal nucleus includes: an LFP core layer 11 and a carbon layer 12 enclosing the core layer.

[0067] The aforementioned lithium battery cathode material can be prepared by any of the lithium battery cathode material preparation methods provided in the above embodiments.

[0068] Furthermore, the functional interface layer 20 also encapsulates the arranged crystal nuclei 10 so that, when the lithium battery cathode material is used in the cathode of a lithium battery, the self-assembled particles are connected through the functional interface layer 20, thereby reducing the interface impedance of the lithium battery cathode.

[0069] In embodiments of the present invention, such as Figure 2 As shown, the particle size D of the self-assembled granular lithium battery cathode material is generally 0.3 μm to 10 μm. For example, the particle size D of the self-assembled granular lithium battery cathode material can be 0.3 μm, 0.5 μm, 1 μm, 4 μm, 5 μm, 8 μm, or 10 μm, etc.

[0070] More specifically, the functional interface layer includes an ion-conducting borosilicate glass comprising at least Li, V, Si, B, and O. Preferably, the functional interface layer is composed of an ion-conducting borosilicate glass comprising at least Li, V, Si, B, and O.

[0071] The compaction density of the lithium battery cathode material provided in this embodiment of the invention is greater than 2.65 g / cm³. 3 By controlling the compaction density of the lithium battery cathode material to be greater than 2.65 g / cm³ 3This can effectively improve the volumetric energy density of lithium battery cathode materials.

[0072] Furthermore, embodiments of the present invention provide a lithium battery, which may include the lithium battery cathode material provided in any of the above embodiments.

[0073] Specifically, the lithium battery positive electrode material can be coated onto the current collector to form a conductive coating. The current collector and the conductive coating together constitute the positive electrode of the lithium battery.

[0074] The preparation method of the above-mentioned lithium battery cathode material is described in detail below with several specific embodiments.

[0075] Example 1

[0076] Step A: Lithium carbonate, ferric hydrogen phosphate dihydrate, NH4H2PO4 and glucose are mixed to obtain a mixed raw material. An ionic conductive sintering aid containing 15% Li2O, 35% V2O5, 40% SiO2 and 10% B2O3 is added to the mixed raw material and uniformly distributed by high-energy ball milling to obtain a mixture.

[0077] Step B: Place the mixture in a kiln and heat it to 750°C at a heating rate of 5°C under a N2 atmosphere. Maintain the temperature for 5 hours and sinter to obtain a self-assembled particulate cathode material. The self-assembled particulate cathode material includes arranged crystal nuclei and a functional interface layer with high lithium-ion conductivity that is at least filled at the grain boundaries.

[0078] Example 2

[0079] The difference from Example 1 is that glucose was omitted from the mixed raw materials.

[0080] Example 3

[0081] The difference from Example 1 is that the lithium source used is CH3COOLi, and the iron source is FePO4. 2H2O, with Na3PO4 as the phosphorus source and ascorbic acid as the carbon source.

[0082] Example 4

[0083] The difference from Example 1 is that the ionic conductive sintering aid contains 20% Li2O, 30% V2O5, 35% SiO2, and 15% B2O3.

[0084] Example 5

[0085] The difference from Example 1 is that the ionic conductive sintering aid contains 22% Li2O, 34% V2O5, 32% SiO2, and 12% B2O3.

[0086] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can occur depending on design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a lithium battery cathode material, characterized in that, include: Step 1: Mix a mixed raw material containing at least a lithium source, an iron source and a phosphorus source with an ion-conductive sintering aid, so that the ion-conductive sintering aid is uniformly distributed in the mixed raw material to obtain a mixture; Step 2: Under an inert or weakly reducing atmosphere, the mixture is heated and sintered to obtain a self-assembled particulate cathode material, wherein the self-assembled particulate cathode material includes arranged crystal nuclei and a functional interface layer with high lithium-ion conductivity that is at least filled at the grain boundaries.

2. The preparation method according to claim 1, characterized in that, The mixed raw materials also include: a carbon source; The crystal nucleus includes an LFP core layer and a carbon layer formed by the carbon source that encapsulates the core layer; And / or, Step 1 involves mixing using high-energy ball milling.

3. The preparation method according to claim 1, characterized in that, The lithium source includes at least one of the following compounds: Li₂CO₃, LiOH H2O, LiNO3 and CH3COOLi; And / or, The iron source includes at least one of the following compounds: FeHPO4 2H2O, FeC2O4 2H₂O, (CH₃COO)₂Fe, FePO₄ 2H2O, FeCl3 6H2O and Fe(NO3)3 9H2O; And / or, The phosphorus source includes at least one of the following compounds: NH4H2PO4, FePO4 2H2O, H3PO4, Na4P2O7 and Na3PO4.

4. The preparation method according to claim 1, characterized in that, The ion-conductive sintering aid belongs to the ion-conductive borosilicate glass system, wherein the ion-conductive sintering aid includes at least: Li, V, Si, B and O; And / or, The ionic conductive sintering aid accounts for 0.5 wt% to 5.0 wt% of the total mass of the mixture.

5. The preparation method according to any one of claims 1 to 3, characterized in that, The ionicly conductive sintering aid includes at least the following oxide precursors: The molar fractions are 15%~25% Li2O, 25%~35% V2O5, 30%~40% SiO2, and 5%~15% B2O3.

6. The preparation method according to any one of claims 1 to 3, characterized in that, Step 2 includes: heating and sintering the mixture by gradient heating to 700℃~800℃, and holding at that temperature for 2h~10h; Preferably, the gradient heating rate in step 2 is 1℃~5℃.

7. A lithium battery cathode material, characterized in that, The lithium battery cathode material is a self-assembled granular material, comprising: The arrangement of crystal nuclei and a functional interface layer with high lithium-ion conductivity, at least filling the grain boundaries.

8. The lithium battery cathode material according to claim 7, characterized in that, The functional interface layer also encloses the arranged crystal nuclei; And / or, The particle size of the self-assembled granular lithium battery cathode material is 0.3μm~10μm; And / or, The crystal nucleus comprises: an LFP core layer and a carbon layer enclosing the core layer.

9. The lithium battery cathode material according to claim 7 or 8, characterized in that, The functional interface layer includes: an ion-conductive borosilicate glass comprising at least Li, V, Si, B and O; And / or, The compaction density of the lithium battery cathode material is greater than 2.65 g / cm³. 3 .

10. A lithium battery, characterized in that, include: The lithium battery cathode material according to any one of claims 7 to 9.

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