Positive electrode material and preparation method therefor, positive electrode sheet, and lithium battery

Abstract

Disclosed in the present application are a positive electrode material and a preparation method therefor, a positive electrode sheet, and a lithium battery. The positive electrode material comprises a core body and a carbon coating layer, wherein the surface of the core body is at least partially coated with the carbon coating layer. The material of the core body comprises a lithium phosphate positive electrode material, and the carbon coating layer comprises one or more groups of a hydrocarbonyl, a halogen atom and a nitro. In the present invention, the surface of the lithium phosphate positive electrode material is coated with a layer of carbon material, which acts as a protective shell, and the carbon coating layer is hydrophobic and the comprised one or more groups of a hydrocarbonyl, a halogen atom and a nitro enables the prepared positive electrode material to be hydrophobic, thereby reducing the contact between the lithium phosphate positive electrode material and external water and ameliorating the water absorption thereof.

Description

Positive electrode materials and their preparation methods, positive electrode sheets and lithium batteries

[0001] This application claims priority to Chinese Patent Application No. 202411722600.9, filed with the Chinese Patent Office on November 27, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and in particular to a positive electrode material and its preparation method, a positive electrode sheet, and a lithium battery. Background Technology

[0003] Lithium-ion battery cathode materials are mainly lithium phosphate and ternary materials, with lithium manganese iron phosphate considered a significant upgrade direction for lithium iron phosphate batteries and showing broad application prospects. Due to the poor conductivity of lithium phosphate cathode materials, nano-sizing is necessary to improve their conductivity. However, the small particle size and large specific surface area of ​​nano-sized lithium phosphate cathode materials make them prone to water absorption, making it difficult to control the moisture content in the battery, affecting the stability of the lithium phosphate cathode material, and consequently impacting the battery's cycle life. Technical issues

[0004] Lithium phosphate cathode materials are prone to absorbing water. Technical solutions

[0005] In a first aspect, embodiments of this application provide a cathode material, including a core and a carbon coating layer, wherein the carbon coating layer at least partially coats the surface of the core, the core being made of lithium phosphate cathode material, and the carbon coating layer containing one or more groups selected from hydrocarbon groups, halogen atoms, and nitro groups.

[0006] Secondly, embodiments of this application provide a method for preparing a cathode material, comprising the following steps:

[0007] A core material and a carbon source are provided, and the carbon source is coated on the surface of the core to obtain a cathode material precursor. The core material includes lithium phosphate cathode material, and the carbon source contains one or more groups selected from hydrocarbon groups, halogen atoms, and nitro groups.

[0008] The cathode material precursor is subjected to a first solid-state sintering to obtain the cathode material.

[0009] Thirdly, embodiments of the present invention provide a positive electrode sheet, including a current collector and an active material layer disposed on the current collector, wherein the active material layer includes the aforementioned positive electrode material, and the contact angle θ of the surface of the active material layer with water is ≥55°.

[0010] Fourthly, embodiments of the present invention provide a lithium battery including the above-described positive electrode. Beneficial effects

[0011] The beneficial effects of the embodiments of the present invention are as follows:

[0012] In embodiments of the present invention, a carbon material is coated onto the surface of the lithium phosphate cathode material as a protective shell. This carbon coating layer is hydrophobic and contains one or more groups selected from hydrocarbon groups, halogen atoms, and nitro groups. This gives the prepared cathode material hydrophobic properties, thereby reducing the contact between the lithium phosphate cathode material and external water, alleviating its water absorption, and thus improving the cycle life of the battery cell. Simultaneously, the carbon coating layer can improve the conductivity of the lithium phosphate cathode material, thus enhancing the conductivity of the lithium phosphate cathode material itself.

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of the present invention and are not intended to limit the present invention.

[0014] The technical solution of this application is as follows:

[0015] In a first aspect, some embodiments of this application provide a cathode material, including a core and a carbon coating layer, wherein the carbon coating layer at least partially coats the surface of the core, the core material includes lithium phosphate cathode material, and the carbon coating layer contains one or more groups selected from hydrocarbon groups, halogen atoms, and nitro groups.

[0016] In this application, a carbon material is coated onto the surface of the lithium phosphate cathode material as a protective shell. This carbon coating layer is hydrophobic and contains one or more groups selected from hydrocarbon, halogen, and nitro groups, which gives the prepared cathode material hydrophobic properties. This reduces the contact between the lithium phosphate cathode material and external water, alleviates its water absorption, and thus improves the cycle life of the battery cell. At the same time, the carbon coating layer can improve the conductivity of the lithium phosphate cathode material and enhance the conductivity of the lithium phosphate cathode material itself.

[0017] In some embodiments of this application, the lithium phosphate cathode material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

[0018] In this application, the water absorption of nano-sized lithium manganese iron phosphate material exacerbates the Jahn-Teller effect of Mn. Carbon coating of lithium manganese iron phosphate can effectively reduce its water absorption, thereby improving the stability of lithium manganese iron phosphate material.

[0019] In some embodiments of this application, the cathode material satisfies the following condition: 14.5 ≤ SSA / D50 ≤ 28.5. For example, SSA / D50 can be 14.5, 15.5, 16.5, 17.5, 18.5, 19.5, 20.5, 21.5, 22.5, 23.5, 24.5, 25.5, 26.5, 27.5, or 28.5, etc., where SSA is the specific surface area of ​​the cathode material, in m². 2 / g, where D50 is the particle size of the cathode material in μm. This allows the cathode material to possess good hydrophobicity.

[0020] In some embodiments of this application, the SSA is 15m. 2 / g-25m 2 / g, for example, can be 15m 2 / g, 16m 2 / g、17m 2 / g、18m 2 / g、19m 2 / g、20m 2 / g、21m 2 / g、22m 2 / g、23m 2 / g、24m 2 / g or 25m 2 / g, etc. This allows the cathode material to possess good performance and be less prone to water absorption. If the specific surface area is too large, the cathode material will easily absorb water; if the specific surface area is too small, the performance of the cathode material will be affected.

[0021] In some embodiments of this application, D50 is 0.5μm-1.5μm, for example, it can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, or 1.5μm. This allows the cathode material to have good rate performance and good processing performance. If D50 is too large, the rate performance of the cathode material will be affected; if D50 is too small, the processing performance of the cathode material will deteriorate.

[0022] In some embodiments of this application, the carbon coating layer is formed by carbonizing a carbon source, wherein the carbon source contains one or more groups selected from hydrocarbon groups, halogen atoms, and nitro groups. This allows the coating layer to possess hydrophobic groups, thereby providing hydrophobic groups on the surface of the cathode material and protecting the core.

[0023] In this application, the carbon source can be a surface-modified (nitrated and / or halogenated) carbon-containing material, including one or more of the following: nitrated and / or halogenated carbon nanotubes, nitrated and / or halogenated graphene, nitrated and / or halogenated carbon nanofibers, nitrated and / or halogenated polydimethylsiloxane, nitrated and / or halogenated polycarbonate, nitrated and / or halogenated polyolefin, and nitrated and / or halogenated polyacrylonitrile. The carbon source may also include polydimethylsiloxane, polycarbonate, polyolefin, or polyacrylonitrile.

[0024] Nitration involves introducing nitro (-NO2) functional groups onto the surface of carbon-containing materials (such as carbon nanotubes, graphene, carbon nanofibers, polydimethylsiloxane, polycarbonate, polyolefins, or polyacrylonitrile). This can be achieved by nitrifying the carbon-containing materials using a mixture of concentrated nitric acid and concentrated sulfuric acid. Halogenation involves introducing halogen atoms onto the surface of carbon-containing materials. This can be achieved by directly reacting the carbon material with a halogen or by reacting it with a halogen in the presence of a catalyst. In some embodiments, the thickness of the carbon coating layer is 0.1 μm-0.2 μm, for example, 0.10 μm, 0.11 μm, 0.12 μm, 0.13 μm, 0.14 μm, 0.15 μm, 0.16 μm, 0.17 μm, 0.18 μm, 0.19 μm, or 0.20 μm. This provides sufficient protection for the core while simultaneously giving the cathode material good performance. A carbon coating that is too thick will affect the performance of the cathode material, while a coating that is too thin will not provide sufficient protection for the core.

[0025] In some embodiments of this application, the carbon coating layer has a mass content of 1.5%-2.0% in the cathode material, for example, it can be 1.5%, 1.6%, 1.7%, 1.8%, 1.9% or 2.0%.

[0026] Secondly, in some embodiments of this application, a method for preparing a positive electrode material is also provided, including the following steps:

[0027] S1. Provide a core material and a carbon source, coat the carbon source onto the surface of the core to obtain a cathode material precursor. The core material includes lithium phosphate cathode material, and the carbon source contains one or more groups among hydrocarbon groups, halogen atoms, and nitro groups.

[0028] S2. Perform a first solid-state sintering on the cathode material precursor to obtain the cathode material.

[0029] In some embodiments of this application, the first solid-phase sintering is carried out in an inert gas atmosphere.

[0030] In some embodiments of this application, the sintering temperature of the first solid phase is 300℃-1200℃, for example, it can be 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃, or 1200℃, etc., and the sintering time of the first solid phase is 6h-12h, for example, it can be 6h, 7h, 8h, 9h, 10h, 11h, or 12h, etc. In this way, the carbon source and the core can be fully combined, thereby improving the performance of the cathode material.

[0031] In some embodiments of this application, coating the carbon source onto the surface of the core material includes:

[0032] The carbon source is dispersed in an organic solvent to obtain a dispersion, and then the dispersion is coated onto the surface of the core material by spray drying.

[0033] In this application, the state of the coating layer can be controlled by adjusting the concentration of the dispersion and the drying temperature of the spray dryer, thereby controlling the specific surface area of ​​the cathode material. The dispersion can be a suspension.

[0034] In some embodiments of this application, the carbon source includes one or more of carbon nanotubes, graphene, carbon nanofibers, polydimethylsiloxane, polycarbonate, polyolefins, and polyacrylonitrile.

[0035] In some embodiments of this application, the mass concentration of the carbon source in the dispersion is 10%-20%, for example, it can be 10%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19% or 20%, etc.

[0036] In some embodiments of this application, the drying temperature of spray drying is 60℃-80℃, for example, it can be 60℃, 62℃, 64℃, 66℃, 68℃, 70℃, 72℃, 74℃, 76℃, 78℃ or 80℃, etc.

[0037] In some embodiments of this application, the organic solvent includes one or more of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), toluene, and carbon tetrachloride.

[0038] In some embodiments of this application, the preparation method of lithium phosphate cathode material includes the following steps:

[0039] S11. Provide a manganese source, an iron source, a phosphorus source and a lithium source, or provide an iron source, a phosphorus source and a lithium source, mix them, and grind them together with water to obtain a mixture.

[0040] S12. The mixture is subjected to a second solid-phase sintering to obtain lithium phosphate cathode material.

[0041] In this application, the particle size of the cathode material can be adjusted by controlling the grinding time and the temperature of the second solid-phase sintering.

[0042] In some embodiments of this application, the grinding time is 2h-6h, for example, it can be 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h.

[0043] In some embodiments of this application, the sintering temperature of the second solid phase is 300℃-1200℃, for example, it can be 300℃, 400℃, 500℃, 600℃, 700℃, 800℃, 900℃, 1000℃, 1100℃ or 1200℃, etc., and the sintering time of the second solid phase is 6h-12h, for example, it can be 6h, 7h, 8h, 9h, 10h, 11h or 12h, etc.

[0044] In some embodiments of this application, the manganese source includes one or more of manganese tetroxide, manganese trioxide, manganese sulfate, manganese carbonate, manganese oxalate, and manganese hydroxide.

[0045] In some embodiments of this application, the iron source includes one or more of the following: iron(II,III) oxide, ferric oxide, ferric hydroxide, ferrous sulfate, ferric sulfate, and ferric oxalate.

[0046] In some embodiments of this application, the phosphorus source includes one or more of phosphoric acid, phosphate ester, lithium dihydrogen phosphate, iron phosphate, lithium phosphate, ammonium phosphate, and sodium phosphate.

[0047] In some embodiments of this application, the lithium source is one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium oxalate, lithium dihydrogen phosphate, and lithium sulfate.

[0048] Thirdly, in some embodiments of this application, a positive electrode slurry is also provided, comprising the aforementioned positive electrode material.

[0049] In some embodiments of this application, the positive electrode slurry further includes a conductive agent, a binder, and a dispersant.

[0050] In some embodiments of this application, the mass percentage ratio of the positive electrode material, conductive agent, binder, and dispersant in the positive electrode slurry is (93.5%-98%):(0.1%-3%):(0.1%-3%):(0.1%-0.5%), for example, 93.5%:3%:3%:0.5%, 94.5%:2%:3%:0.5%, 94.5%:3%:2%:0.5%, 94.5%:2.2%: 3%:0.3%, 95.5%:2%:2%:0.5%, 95.5%:2.3%:2%:0.2%, 96.5%:2%:1%:0.5%, 96.5%:1%:2%:0.5%, 96.5%:2.4%:1%:0.1%, 96.5%:2%:1.1%:0.4%, 97.5%:1%:1%:0.5% or 97.5%:1.2%:1.2%:0.1%, etc.

[0051] In this application, the positive electrode slurry can be prepared by directly dissolving the positive electrode material, conductive agent, binder and dispersant in a solvent.

[0052] Fourthly, in some embodiments of this application, a positive electrode sheet is also provided, including a current collector and an active material layer disposed on the current collector, the active material layer including the above-mentioned positive electrode material, and the contact angle θ of the surface of the active material layer with water is ≥55°.

[0053] In some embodiments of this application, the contact angle θ of the surface of the active material layer with water is ≥55°, for example, it can be 55°, 56°, 57°, 58°, 59°, 60°, 61°, 62°, 63°, 64°, 65°, 66°, 67°, 68°, 69° or 70°, etc.

[0054] In this application, the positive electrode sheet can be prepared by directly coating the positive electrode slurry onto the current collector and then drying it.

[0055] Fifthly, in some embodiments of this application, a lithium battery is also provided, including the above-described positive electrode. Example

[0056] A cathode material and its preparation method, comprising the following steps:

[0057] (1) Add manganese tetroxide, iron phosphate, phosphoric acid and lithium carbonate in a molar ratio of 1:3:8:3 into a grinding jar, add water and perform physical grinding. After grinding for 2 hours, sinter the mixture at 300°C for 8 hours to obtain a primary precursor.

[0058] (2) Nitrogen graphene (NGO) was dispersed in NMP (the mass concentration of nitrated graphene was 10%) and uniformly coated onto the primary precursor by spray drying at a temperature of 60°C to obtain the secondary precursor.

[0059] (3) The secondary precursor was solid-state sintered at 800°C in N2 atmosphere for 6 hours to obtain the cathode material (the thickness of the carbon coating layer is 0.1 μm and the mass content of the carbon coating layer in the cathode material is 1.8%).

[0060] A positive electrode slurry and its preparation method, comprising the following steps:

[0061] The obtained positive electrode material was mixed with conductive carbon black (SP), polyvinylidene fluoride (PVDF), and polyisobutylene diimide (PI) in an N-methylpyrrolidone (NMP) solvent at a mass ratio of 97.2%:0.9%:1.7%:0.2%, and stirred evenly to obtain the positive electrode slurry.

[0062] A positive electrode sheet and its preparation method, comprising the following steps:

[0063] The obtained positive electrode slurry was uniformly coated onto a 12μm thick aluminum foil, and after drying, a positive electrode sheet was obtained. Example

[0064] This embodiment is basically the same as Embodiment 1, except that the grinding time in this embodiment is 4 hours. Example

[0065] This embodiment is basically the same as Embodiment 1, except that the grinding time in this embodiment is 6 hours. Example

[0066] This embodiment is basically the same as embodiment 1, except that the sintering temperature in step (1) of this embodiment is 800℃. Example

[0067] This embodiment is basically the same as embodiment 2, except that the sintering temperature in step (1) of this embodiment is 800℃. Example

[0068] This embodiment is basically the same as embodiment 3, except that the sintering temperature in step (1) of this embodiment is 800℃. Example

[0069] This embodiment is basically the same as embodiment 1, except that the sintering temperature in step (1) of this embodiment is 1200℃. Example

[0070] This embodiment is basically the same as embodiment 2, except that the sintering temperature in step (1) of this embodiment is 1200℃. Example

[0071] This embodiment is basically the same as embodiment 3, except that the sintering temperature in step (1) of this embodiment is 1200℃. Example

[0072] This embodiment is basically the same as Embodiment 1, except that the mass concentration of nitrated graphene in this embodiment is 15%. Example

[0073] This embodiment is basically the same as Embodiment 1, except that the mass concentration of nitrated graphene in this embodiment is 20%. Example

[0074] This embodiment is basically the same as Embodiment 1, except that the spray drying temperature in this embodiment is 70°C. Example

[0075] This embodiment is basically the same as Embodiment 1, except that the spray drying temperature in this embodiment is 80°C. Example

[0076] This embodiment is basically the same as embodiment 11, except that the spray drying temperature in this embodiment is 80°C. Example

[0077] This embodiment is basically the same as Embodiment 1, except that in this embodiment, manganese tetroxide, iron phosphate, phosphoric acid, and lithium carbonate are replaced with iron phosphate and lithium carbonate in a molar ratio of 1:1. Example

[0078] This embodiment is basically the same as embodiment 1, except that the sintering temperature in step (1) of this embodiment is 1500℃. Example

[0079] This embodiment is basically the same as Embodiment 1, except that the grinding time in this embodiment is 10 hours. Example

[0080] This embodiment is basically the same as Embodiment 1, except that the mass concentration of nitrated graphene in this embodiment is 30%. Example

[0081] This embodiment is basically the same as Embodiment 1, except that the spray drying temperature in this embodiment is 100°C.

[0082] Comparative Example 1

[0083] This comparative example is basically the same as Example 1, except that the cathode material in this comparative example is not coated.

[0084] Lithium batteries were fabricated using the positive electrode sheets obtained in the examples and comparative examples. The separator was a 7+2+2 mixed-coating separator (the base film was a 7μm thick PE material, with 2μm thick coatings on both the top and bottom surfaces of the base film; the coating material was a mixture of ceramic particles and PVDF adhesive particles). The electrolyte composition was 30wt% ethylene carbonate (EC), 5wt% propylene carbonate (PC), 25wt% ethyl methyl carbonate (EMC), and 40wt% dimethyl carbonate (DMC). The lithium salt concentration (50% LiFSI + 50% LiPF6) in the electrolyte was 1mol / L. The negative electrode sheet was prepared by the following steps: graphite, conductive carbon black (Super P), carboxymethyl cellulose (CMC), and styrene-butadiene rubber (SBR) were mixed with deionized water in a mass ratio of 8:1:0.5:0.5 to form an electrode slurry, which was then uniformly coated onto a 5μm thick copper foil and dried to obtain the negative electrode sheet. The assembly method was stacking. The manufacturing process includes: electrode cutting, stacking, shelling, vacuum baking, liquid injection, settling, formation, and applying insulating film.

[0085] Test example:

[0086] Cycle capacity retention test: The obtained lithium batteries were subjected to full charge-discharge cycles at 25℃, and the cycle capacity retention rate was recorded. Full charge: At 25℃, the batteries were charged at a constant current of 0.33C to the cutoff voltage (LFP 3.65V, LMFP 4.2V), then switched to constant voltage charging with a cutoff current of 0.05C. Full discharge: At 25℃, the batteries were discharged at 1C to 2.5V.

[0087] Contact angle test: After the positive electrode is assembled into a lithium battery, the positive electrode obtained from the disassembly of the lithium battery is cleaned and dried. Water droplets are dropped directly onto the surface of the positive electrode. The droplet image is captured by an optical contact angle measuring instrument, and then the contact angle θ is automatically measured by software. The test results are shown in Table 1.

[0088] Table 1

[0089] As shown in Table 1:

[0090] Compared with Examples 16-19, the cathode material of Example 1 has a larger contact angle and a higher battery capacity retention rate. It can be seen that by controlling the grinding time, sintering temperature, concentration of carbon source dispersion, and spray drying temperature, the SSA / D50 of the cathode material can be adjusted, thereby controlling the contact angle of the cathode material and thus controlling the battery capacity retention rate.

[0091] Compared with Comparative Example 1, the cathode materials of Examples 1-19 have a larger contact angle and a higher battery capacity retention rate. It can be seen that by coating the surface of the lithium phosphate cathode material with a carbon coating layer, the contact angle of the cathode material can be increased, thereby improving the battery capacity retention rate.

[0092] The embodiments of the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A cathode material, characterized in that: It includes a core and a carbon coating layer, wherein the carbon coating layer at least partially covers the surface of the core, the core is made of lithium phosphate cathode material, and the carbon coating layer contains one or more groups selected from hydrocarbon groups, halogen atoms, and nitro groups.

2. The cathode material as described in claim 1, characterized in that: The lithium phosphate cathode material includes at least one of lithium iron phosphate and lithium manganese iron phosphate; and / or The carbon coating layer is formed by carbonizing a carbon source, wherein the carbon source contains one or more groups selected from hydrocarbon groups, halogen atoms, and nitro groups.

3. The cathode material as described in claim 1, characterized in that: The cathode material satisfies the following condition: 14.5 ≤ SSA / D50 ≤ 28.5, where SSA is the specific surface area of ​​the cathode material, in m². 2 / g, where D50 is the particle size of the cathode material in μm.

4. The cathode material as described in claim 3, characterized in that: The SSA is 15m 2 / g-25m 2 / g; and / or The D50 is 0.5μm-1.5μm.

5. The cathode material as described in claim 4, characterized in that: The thickness of the carbon coating layer is 0.1 μm-0.2 μm; and / or The carbon coating layer has a mass content of 1.5%-2.0% in the cathode material.

6. A method for preparing a positive electrode material, characterized in that, Includes the following steps: S1. Provide a core material and a carbon source, and coat the carbon source onto the surface of the core to obtain a cathode material precursor. The core material includes lithium phosphate cathode material, and the carbon source contains one or more groups selected from hydrocarbon groups, halogen atoms, and nitro groups. S2. Perform a first solid-state sintering on the cathode material precursor to obtain the cathode material.

7. The method for preparing the cathode material as described in claim 6, characterized in that: The step of coating the carbon source onto the surface of the core material includes: The carbon source is dispersed in an organic solvent to obtain a dispersion, and then the dispersion is coated onto the surface of the core material by spray drying.

8. The method for preparing the cathode material as described in claim 7, characterized in that: The carbon source contains one or more groups selected from hydrocarbon groups, halogen atoms, and nitro groups; and / or The carbon source has a mass concentration of 10%-20% in the dispersion; and / or The drying temperature of the spray drying is 60℃-80℃.

9. The method for preparing the cathode material as described in claim 7, characterized in that: The carbon source includes one or more of carbon nanotubes, graphene, carbon nanofibers, polydimethylsiloxane, polycarbonate, polyolefin, and polyacrylonitrile; and / or the organic solvent includes one or more of N-methylpyrrolidone, N,N-dimethylformamide, toluene, and carbon tetrachloride.

10. The method for preparing the cathode material as described in claim 6, characterized in that: The preparation method of the lithium phosphate cathode material includes the following steps: S11. Provide a manganese source, an iron source, a phosphorus source and a lithium source, or provide an iron source, a phosphorus source and a lithium source, mix them, and grind them together with water to obtain a mixture. S12. The mixture is subjected to a second solid-phase sintering to obtain lithium phosphate cathode material.

11. The method for preparing the cathode material as described in claim 10, characterized in that: The manganese source includes one or more of manganese tetroxide, manganese trioxide, manganese sulfate, manganese carbonate, manganese oxalate, and manganese hydroxide.

12. The method for preparing the cathode material as described in claim 10, characterized in that: The iron source includes one or more of the following: iron(II,III) oxide, ferric oxide, ferric hydroxide, ferrous sulfate, ferric sulfate, and ferric oxalate.

13. The method for preparing the cathode material as described in claim 10, characterized in that: The phosphorus source includes one or more of phosphoric acid, phosphate ester, lithium dihydrogen phosphate, iron phosphate, lithium phosphate, ammonium phosphate, and sodium phosphate.

14. The method for preparing the cathode material as described in claim 11, characterized in that: The lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium phosphate, lithium oxalate, lithium dihydrogen phosphate, and lithium sulfate.

15. The method for preparing the cathode material as described in claim 10, characterized in that: The grinding time is 2 hours to 6 hours; and / or The second solid phase is sintered at a temperature of 300℃-1200℃ for 6h-12h.

16. The method for preparing the cathode material as described in claim 6, characterized in that: The first solid-state sintering is carried out in an inert gas atmosphere; and / or The sintering temperature of the first solid phase is 300℃-1200℃, and the sintering time of the first solid phase is 6h-12h.

17. A positive electrode slurry, comprising a positive electrode material, characterized in that: The cathode material is a cathode material prepared by any one of claims 1-5 or any one of claims 6-16.

18. The positive electrode slurry as described in claim 17, characterized in that: The positive electrode slurry further includes a conductive agent, a binder, and a dispersant; and / or the mass percentage of the positive electrode material, the conductive agent, the binder, and the dispersant in the positive electrode slurry is (93.5%-98%):(0.1%-3%):(0.1%-3%):(0.1%-0.5%).

19. A positive electrode plate, characterized in that: The device includes a current collector and an active material layer disposed on the current collector. The active material layer includes a positive electrode material as described in any one of claims 1-5 or a positive electrode material prepared by any one of claims 6-16. The contact angle θ of the surface of the active material layer with water is ≥55°.

20. A lithium battery, characterized in that: Including the positive electrode sheet as described in claim 19.

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