Positive electrode active material precursor and preparation method of precursor

Abstract

The invention relates to the technical field of lithium battery positive electrode material preparation, in particular to a lithium battery positive electrode active substance precursor and a preparation method thereof. The preparation method comprises the following steps: 1, preparing a metal salt water solution A, a metal salt water solution B, a water solution C containing a water-soluble doped metal compound, an ammonia water solution, a phosphoric acid or phosphate solution and an alkali solution, wherein the metal salt water solution A and the metal salt water solution B are obtained by mixing FeSO4 and MnSO4 in different molar ratios; 2, adding the metal salt aqueous solution A, the doped metal aqueous solution C and the mixed solution into a coprecipitation reactor in which an inert gas atmosphere is formed, and meanwhile, generating a precursor seed crystal rich in Mn metal; the method comprises the following steps: mixing a metal salt aqueous solution A and a metal salt aqueous solution B, and adding the mixture and a doped metal aqueous solution C into a coprecipitation reactor to form a core-shell structure crystal with concentration gradient; 3, adding a carbon source, washing with water, and drying to form a carbon-coated active substance precursor with a concentration gradient shell-core structure; the active substance precursor is prepared by adopting a liquid phase coprecipitation method, so that the active substance precursor can be endowed with a concentration gradient, and doped metal with specific concentration distribution can be obtained. According to the invention, the active substance precursor is endowed with the concentration gradient and the doped metal with uniform concentration, so that the cycle characteristic of the active substance is better; the process can be simplified, and the cleaning frequency and resource waste are reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery positive electrode material preparation, and in particular to a positive electrode active material precursor and a method for preparing the precursor. Background Art

[0002] In the field of lithium batteries, LiFe x Mn y During the battery cycle, the Mn element in PO4 is easily dissolved due to the Jan-Taylor effect, resulting in low cycle efficiency. x Mn y PO4, which improves its circulation efficiency, but the hydrothermal method uses excessive Li elements, which requires high resource recovery. In addition, in order to provide lithium manganese iron phosphate active materials with a concentration gradient structure, multiple hydrothermal reactions and multiple sintering methods are required, but the multiple hydrothermal method requires multiple sample washing, multiple drying and multiple heating reaction steps; in engineering, a large amount of wastewater containing transition metal resources is generated, and a large amount of energy is consumed, which poses great challenges in terms of resource utilization, environmental protection and energy consumption; on the other hand, Ti is added as an additive to Li Fe x Mn y PO4, has the effects of reducing lattice distortion, improving electrochemical performance and cycle stability, and inhibiting capacity decay caused by the Jan-Taylor effect, but Ti-containing compounds are difficult to dissolve in water and can usually only be added by solid phase method, which makes it difficult to mix evenly with the positive active material, reducing the efficacy of the additive. Therefore, the present invention develops a lithium battery positive active material precursor and a method for preparing the precursor to solve the problems existing in the prior art. Summary of the invention

[0003] The purpose of the present invention is to provide a living substance precursor and a method for preparing the precursor to solve the problems and technical problems of the prior art that the processing method is complicated and wastes resources.

[0004] The technical solution of the present invention is: a living substance precursor, including a central part, a middle part and an outer part, and its average chemical formula is: Fe x Mn y M z X w PO4;

[0005] Wherein, M is a hydrogen ion, a volatile cation, or a mixture thereof, and its average valence is a;

[0006] N is a doping ion with a valence of b;

[0007] And it satisfies: 2x+2y+az+bw=3;

[0008] The Fe and Mn elements have a continuous concentration gradient from the center to the surface.

[0009] Preferably, in the active material precursor, the average molar ratio x:y of Fe to Mn is 2:8 to 1:9;

[0010] The Fe element has a concentration gradient that gradually increases from the central portion to the outer portion;

[0011] The Mn element has a concentration gradient that gradually decreases from the central portion to the outer portion;

[0012] The X element is Ti, and the Ti element has a uniform concentration in the central portion and the outer portion.

[0013] The method for preparing the above-mentioned active substance precursor comprises:

[0014] Prepare a metal salt aqueous solution A forming the center portion, including an iron salt solution and a manganese salt solution, and the molar ratio is x1 / y1;

[0015] A metal salt solution B for forming the outer surface is prepared, comprising an iron salt solution and a manganese salt solution, and the molar ratio is x2 / y2; wherein x1 / y1<x2 / y2;

[0016] preparing a soluble titanium compound solution C containing a doping element Ti;

[0017] preparing a mixed solution including an ammonia solution, a phosphoric acid solution or a phosphate solution, and an alkaline solution;

[0018] Adding the metal salt aqueous solution A, the soluble titanium compound solution C and the mixed solution into a co-precipitation reactor formed with an inert gas atmosphere to generate seed crystals containing Fe and Mn at a molar ratio of x1 / y1 and uniform Ti concentration of a1;

[0019] The metal salt aqueous solution A is mixed with the metal salt aqueous solution B to form an aqueous solution whose concentration of Mn element decreases over time, and the aqueous solution is added to the coprecipitation reactor, and the addition speed of the soluble titanium compound solution C is adjusted to form a core-shell structure with a concentration gradient, wherein the shell layer contains crystals with a Ti concentration of a2;

[0020] A carbon source is added into the coprecipitation reactor, and the precursor formed by the reaction is separated, washed with water, and dried to form a carbon-coated active material precursor with a core-shell structure having a concentration gradient.

[0021] Preferably, when the metal salt aqueous solution A and the metal salt aqueous solution B are mixed and added to the co-precipitation reactor, the mixed solution is continuously added to the co-precipitation reactor.

[0022] Preferably, when the mixed solution is mixed with the metal salt aqueous solution A, and with the combination of the metal salt aqueous solution A and the metal salt aqueous solution B, the addition acceleration of the ammonia aqueous solution is 1 to 800 mmol / h / L, the addition acceleration of the alkali solution is 1 to 800 mmol / h / L, the addition acceleration of the phosphoric acid solution or the phosphate solution is 1 to 800 mmol / h / L, the addition acceleration of the aqueous solution C is 0.1 to 8 mmol / h / L, and the addition acceleration when forming the core part is greater than the addition acceleration when forming the shell part.

[0023] Preferably, the dosing speed of the ammonia solution is 1-100 mmol / h / L, the dosing speed of the alkali solution is 1-100 mmol / h / L, the dosing speed of the phosphoric acid or phosphate solution is 1-100 mmol / h / L, and the dosing speed of the aqueous solution C is 0.8-3.2 mmol / h / L;

[0024] The addition speeds of the phosphoric acid or phosphate solution, the ammonia solution and the alkaline solution are sequentially reduced to control the concentration of each solution.

[0025] Preferably, the metal salt aqueous solution A and the mixed solution are reacted at a temperature of 30 to 80° C. for 30 to 40 minutes;

[0026] After the metal salt aqueous solution A and the metal salt aqueous solution B are mixed, the mixed solution is added simultaneously and reacted at a temperature of 30 to 80° C. for at least 20 to 60 hours.

[0027] Preferably, the cation concentrations in the metal salt aqueous solution A and the metal salt aqueous solution B are both 0.5-2 mol / L, the iron salt solution is FeSO4 solution, and the manganese salt solution is MnSO4 solution; more preferably, the cation concentrations in the metal salt aqueous solution A and the metal salt aqueous solution B are 1.4-1.6 mol / L;

[0028] In the metal salt aqueous solution A, the molar ratio of FeSO4 to MnSO4 is 2:8 to 0.5:9.5;

[0029] In the metal salt aqueous solution B, the molar ratio of FeSO4 to MnSO4 is 3:7 to 5:5.

[0030] Preferably, the carbon source is glucose, and the carbon coating content in the active material precursor formed by treatment to form a carbon-coated core-shell structure with a concentration gradient is 0.5-3wt%; more preferably, the carbon coating content is 1.25-1.36wt%.

[0031] Based on a living material precursor, a living material is obtained, mainly the living material precursor Fe x Mn y M z X w PO4 is mixed with a lithium source and sintered in an inert gas atmosphere.

[0032] Compared with the prior art, the advantages of the present invention are:

[0033] The present invention adopts a liquid phase coprecipitation method to prepare an active material precursor. Compared with the traditional solid phase method, the particle size of the positive electrode material finally prepared can be uniform and consistent, and a concentration gradient can be given to the active material precursor, and the cycle characteristics are better; compared with the traditional hydrothermal method, the process is simple, the amount of Li element consumed is small, the number of washing times is small, and resource waste is reduced. Compared with the traditional coprecipitation method, the active material precursor can be given a uniform doping metal, and has a better capacity retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The present invention will be further described below in conjunction with the accompanying drawings and embodiments:

[0035] Figure 1 The present invention is a flow chart of a method for preparing a living substance precursor. DETAILED DESCRIPTION

[0036] The present invention is further described in detail below in conjunction with specific embodiments:

[0037] An active substance precursor, comprising a central portion, a middle portion and an outer portion, and having an average chemical formula of: Fe x Mn y M z X w PO4.

[0038] Where M is a hydrogen ion (H + ) or volatile cations (such as NH4 + ), or any mixture thereof in any ratio, the average valence of which is a;

[0039] X is Ti and its valence is b, usually +4; the above doping ions are added in the coprecipitation reaction.

[0040] The average chemical formula of the active material precursor obtained is Fe x Mn y M z N wPO4, and satisfies 2x+2y+az+bw=3; Fe and Mn elements have continuous concentration gradients from the center to the surface, that is: the Fe element has a concentration gradient that gradually increases from the center to the surface; the Mn element has a concentration gradient that gradually decreases from the center to the surface.

[0041] Regarding a method for preparing a precursor of a living substance, Figure 1 As shown, the main steps are as follows:

[0042] Example 1

[0043] (1) preparing a metal salt aqueous solution A for forming the center of the active material precursor, including an iron salt solution and a manganese salt solution, wherein the iron salt solution is a FeSO4 solution and the manganese salt solution is a MnSO4 solution, wherein the molar ratio of FeSO4 to MnSO4 is 0.5:9.5;

[0044] (2) preparing a metal salt aqueous solution B for forming the outer surface of the active material precursor, including a FeSO4 solution and a MnSO4 solution, wherein the molar ratio of FeSO4 to MnSO4 is 3:7;

[0045] (3) Preparing a metal-doped soluble Ti compound aqueous solution C. In this embodiment, bis(dioctyloxypyrophosphate)ethylene titanate (Kenrich Petrochemical Company, USA, KR-238S) was selected.

[0046] (4) preparing a mixed solution, including 15 wt % of an ammonia solution, 10 wt % of a phosphoric acid solution, and 25 wt % of an alkali solution; in this embodiment, the alkali solution is a NaOH solution;

[0047] (5) Prepare a coprecipitation reactor, add 4 L of distilled water into the coprecipitation reactor, and introduce nitrogen at a rate of 2 L / min to remove residual oxygen; maintain the solution temperature at 50° C. and stir at a rate of 400 rpm; then add 10 ml of the above-mentioned NaOH solution and 200 ml of the above-mentioned ammonia water to keep the solution pH at 12;

[0048] (6) adding metal salt aqueous solution A, aqueous solution C, and the mixed solution into a coprecipitation reactor formed with an inert gas atmosphere to generate seed crystals containing Fe and Mn in a molar ratio of 0.5:9.5; during the addition, the addition speed of the metal salt aqueous solution A is 60 mmol / h / L, the addition speed of the ammonia solution is 20 mmol / h / L, the addition speed of the phosphoric acid solution is 90 mmol / h / L, the addition speed of the NaOH solution is 10 mmol / h / L, and the addition speed of the aqueous solution C is 2.0 mmol / h / L, and the whole process lasts for 30 min;

[0049] (7) Mixing the metal salt aqueous solution B with the metal salt aqueous solution A at a dosing rate of 1.5 mmol / h to form an aqueous solution in which the concentration of the Mn element decreases over time, and adding the solution to the coprecipitation reactor to form a shell-core structure crystal with a concentration gradient; during this process, continuously adding the mixed solution to the coprecipitation reactor, while increasing the dosing rate of the aqueous solution C; wherein the dosing rate of the mixed metal salt aqueous solution A and the metal salt aqueous solution B is 60 mmol / h / L, the dosing rate of the ammonia solution is 20 mmol / h / L, the dosing rate of the phosphoric acid solution is 90 mmol / h / L, the dosing rate of the NaOH solution is 10 mmol / h / L, and the dosing rate of the aqueous solution C is 1.2 mmol / h / L, and the whole process lasts for 31.5 hours;

[0050] (8) Glucose is added into a coprecipitation reactor, and the precursor formed by the reaction is separated, washed with water, and dried at 120° C. to form a carbon-coated active material precursor with a core-shell structure having a concentration gradient, wherein the carbon coating content accounts for 1.3 wt %.

[0051] In the active material precursor prepared by the above method, the average molar ratio of Mn:Fe is 9:1, and the corresponding average chemical formula of the active material precursor is: (Fe 0.1 Mn 0.9 ) 0.99 T i 0.01 NH4PO4.

[0052] After the active material precursor is prepared, the active material precursor (Fe 0.1 Mn 0.9 ) 0.99 T i 0.01 NH4PO4 is mixed with lithium source LiOH, and then sintered at 700℃ for 5h in nitrogen atmosphere to form an average chemical formula of Li(Fe 0.1 Mn 0.9 ) 0.99 T i 0.01 PO4 active substances.

[0053] The lithium-ion battery prepared by using the active material of this embodiment as the positive electrode material has a tap density of 1.73g / ml, a compaction density of 2.52g / ml, a specific capacity of 149mAh / g, an initial coulombic efficiency of 94%; and a capacity retention rate of 99.3% that can be achieved after 100 cycles.

[0054] Example 2

[0055] (1) preparing a metal salt aqueous solution A, including a FeSO4 solution and a MnSO4 solution, wherein the molar ratio of FeSO4 to MnSO4 is 1:9;

[0056] (2) preparing a metal salt aqueous solution B, including a FeSO4 solution and a MnSO4 solution, wherein the molar ratio of FeSO4 to MnSO4 is 3:7;

[0057] (3) Preparing a metal-doped soluble Ti compound aqueous solution C. In this embodiment, bis(dioctyloxypyrophosphate)ethylene titanate (Kenrich Petrochemical Company, USA, KR-238S) was selected.

[0058] (4) preparing a mixed solution comprising 15 wt % of an ammonia solution, 10 wt % of a phosphoric acid solution, and 25 wt % of a NaOH solution;

[0059] (5) Prepare a coprecipitation reactor, add 4 L of distilled water into the coprecipitation reactor, and introduce nitrogen at a rate of 2 L / min to remove residual oxygen; maintain the solution temperature at 50° C. and stir at a rate of 400 rpm; then add 10 ml of the above-mentioned NaOH solution and 200 ml of the above-mentioned ammonia water to keep the solution pH at 12;

[0060] (6) adding the metal salt aqueous solution A and the mixed solution into a coprecipitation reactor formed with an inert gas atmosphere to generate seed crystals containing Fe and Mn in a molar ratio of 1:9; during the addition, the addition speed of the metal salt aqueous solution A is 60 mmol / h / L, the addition speed of the ammonia solution is 20 mmol / h / L, the addition speed of the phosphoric acid solution is 90 mmol / h / L, the addition speed of the NaOH solution is 10 mmol / h / L, and the addition speed of the solution C is 2.0 mmol / h / L, and the whole process lasts for 30 min;

[0061] (7) Mixing the metal salt aqueous solution B with the metal salt aqueous solution A at a dosing rate of 1.5 mmol 1 / h to form an aqueous solution in which the concentration of the Mn element decreases over time, and adding the solution to the coprecipitation reactor to form crystals of a core-shell structure having a concentration gradient; during this process, continuously adding the mixed solution to the coprecipitation reactor; wherein the dosing rate of the mixed metal salt aqueous solution A and the metal salt aqueous solution B is 60 mmol / h / L, the dosing rate of the ammonia solution is 20 mmol / h / L, the dosing rate of the phosphoric acid solution is 90 mmol / h / L, the dosing rate of the NaOH solution is 10 mmol / h / L, and the dosing rate of the aqueous solution C is 1.2 mmol / h / L, and the whole process lasts for 31.5 h;

[0062] (8) Glucose is added into a coprecipitation reactor, and the precursor formed by the reaction is separated, washed with water, and dried at 120° C. to form a carbon-coated active material precursor with a core-shell structure having a concentration gradient, wherein the carbon coating content accounts for 1.3 wt %.

[0063] The difference between Example 2 and Example 1 is that the molar ratio of FeSO4 to MnSO4 in the prepared metal salt aqueous solution A is different; in the active material precursor prepared based on the above method, the average molar ratio of Mn:Fe is 8:1, and the corresponding average chemical formula of the active material precursor is: (Fe 1 / 9 Mn 8 / 9 ) 0.99 T i 0.01 NH4PO4.

[0064] After the active material precursor is prepared, the active material precursor (Fe 1 / 9 Mn 8 / 9 ) 0.99 T i 0.01 NH4PO4 and lithium source LiOH, with W as doping ion, were mixed and sintered at 700℃ for 5h in nitrogen atmosphere to form an average chemical formula of Li(Fe 1 / 9 Mn 8 / 9 ) 0.99 T i 0.01 PO4 active substances.

[0065] The lithium-ion battery prepared by using the active material of this embodiment as the positive electrode material has a tap density of 1.71g / ml, a compaction density of 2.52g / ml, a specific capacity of 147mAh / g, an initial coulombic efficiency of 93%; and a capacity retention rate of 99.5% that can be achieved after 100 cycles.

[0066] Comparative Example 1

[0067] In this comparative example, the difference from Example 1 or Example 2 is that:

[0068] Prepare a metal salt aqueous solution A, including a FeSO4 solution and a MnSO4 solution, wherein the molar ratio of FeSO4 to MnSO4 is 1:9;

[0069] A metal salt aqueous solution B is prepared, including a FeSO4 solution and a MnSO4 solution, and the molar ratio of FeSO4 to MnSO4 is also 1:9.

[0070] In the prepared active material precursor, the average molar ratio of Mn:Fe is 9:1, and the corresponding average chemical formula of the active material precursor is: (Fe 0.1 Mn 0.9 ) 0.99 T i0.01 NH4PO4.

[0071] After the active material precursor is prepared, the active material precursor (Fe 0.1 Mn 0.9 ) 0.99 T i 0.01 NH4PO4 was mixed with lithium source LiOH and sintered at 700℃ for 5h in nitrogen atmosphere to form an average chemical formula of Li(Fe 0.1 Mn 0.9 ) 0.99 T i 0.01 PO4 active substances.

[0072] The lithium-ion battery prepared by using the active material of this comparative example as the positive electrode material has a tap density of 1.62g / ml, a compaction density of 2.41g / ml, a specific capacity of 149mAh / g, an initial coulombic efficiency of 89.2%; the capacity retention rate that can be achieved after 100 cycles is 82.1%.

[0073] Comparing this comparative example with Examples 1 and 2, when there is no concentration gradient between Fe and Mn elements during the preparation of the active material precursor, the capacity retention rate of the lithium battery decreases significantly.

[0074] Comparative Example 2

[0075] In this comparative example, the difference from Example 1 or Example 2 is that:

[0076] Prepare a metal salt aqueous solution A, including a FeSO4 solution and a MnSO4 solution, wherein the molar ratio of FeSO4 to MnSO4 is 1:8;

[0077] A metal salt aqueous solution B is prepared, including a FeSO4 solution and a MnSO4 solution, and the molar ratio of FeSO4 to MnSO4 is also 1:8.

[0078] In the active material precursor prepared by the above method, the average molar ratio of Mn:Fe is 8:1, and the corresponding average chemical formula of the active material precursor is: Fe 0.1 Mn 0.9 NH4PO4.

[0079] After the active material precursor is prepared, the active material precursor Fe 0.1 Mn 0.9 NH4PO4, LiOH and TiO2 were mixed in a molar ratio of 99:1 and sintered at 700℃ for 5h in a nitrogen atmosphere to form a product with an average chemical formula of (Fe 0.1 Mn 0.9 ) 0.99 T i0.01 The active substance of NH4PO4.

[0080] The lithium-ion battery prepared by using the active material of this embodiment as the positive electrode material has a tap density of 1.68g / ml, a compaction density of 2.34g / ml, a specific capacity of 146mAh / g, an initial coulombic efficiency of 89%; and a capacity retention rate of 93.2% that can be achieved after 100 cycles.

[0081] This comparative example further proves that when the Ti element in the active material precursor is not evenly distributed, the capacity retention rate of the lithium battery will decrease significantly.

[0082] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the scope of protection of the present invention. For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, no matter from which point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is limited by the attached claims rather than the above description, and it is intended to include all changes within the meaning and scope of the equivalent elements of the claims in the present invention.

Claims

1. A living substance precursor, characterized in that: Including the center, middle and outer parts, its average chemical formula is: Fe x Mn y M z X w PO4; Wherein, M is a hydrogen ion, a volatile cation, or a mixture thereof, and its average valence is a; X is a doping ion with a valence of b; And it satisfies: 2x+2y+az+bw=3; The Fe and Mn elements have a continuous concentration gradient from the center to the outer surface, and the doping element X has a uniform concentration in the center and the outer surface.

2. A living substance precursor according to claim 1, characterized in that: In the active material precursor, the average molar ratio x:y of Fe to Mn is 2:8 to 1:9; The Fe element has a concentration gradient that gradually increases from the central portion to the outer portion; The Mn element has a concentration gradient that gradually decreases from the central portion to the outer portion.

3. A living substance precursor according to claim 1 or 2, characterized in that: In the active material precursor, X is Ti, and the Ti element has a uniform concentration in the central part and the outer part; The concentration of the Ti element in the central portion is greater than that in the outer portion.

4. A method for preparing a living substance precursor according to claim 3, characterized in that: include: Prepare a metal salt aqueous solution A forming the center portion, including an iron salt solution and a manganese salt solution, and the molar ratio is x1 / y1; A metal salt aqueous solution B for forming the outer surface is prepared, comprising an iron salt solution and a manganese salt solution, and the molar ratio is x2 / y2; wherein x1 / y1<x2 / y2; An aqueous solution C containing a water-soluble metal compound of Ti is prepared, including a water-soluble titanium compound solution. preparing a mixed solution including an ammonia solution, a phosphoric acid solution or a phosphate solution, and an alkali solution; Adding the metal salt aqueous solution A, aqueous solution C, and the mixed solution into a co-precipitation reactor formed with an inert gas atmosphere to generate seed crystals containing Fe and Mn at a molar ratio of x1 / y1 and containing doping elements; The metal salt aqueous solution A is mixed with the metal salt aqueous solution B to form an aqueous solution whose concentration of Mn element decreases over time, and the aqueous solution is added to the coprecipitation reactor, while adjusting the speed of adding the aqueous solution C to form a core-shell structure crystal with a Mn and Fe concentration gradient and different doping element contents; A carbon source is added into the coprecipitation reactor, and the precursor formed by the reaction is separated, washed with water, and dried to form a carbon-coated active material precursor with a core-shell structure having a concentration gradient.

5. The active substance precursor and the preparation method thereof according to claim 4, characterized in that: When the metal salt aqueous solution A and the metal salt aqueous solution B are mixed and added into the co-precipitation reactor, the mixed solution is continuously added into the co-precipitation reactor.

6. The active substance precursor and the preparation method thereof according to claim 5, characterized in that: When the mixed solution is mixed with the metal salt aqueous solution A, and with the combination of the metal salt aqueous solution A and the metal salt aqueous solution B, the addition acceleration of the ammonia aqueous solution is 1 to 800 mmol / h / L, the addition acceleration of the alkaline solution is 1 to 800 mmol / h / L, the addition acceleration of the phosphoric acid solution or the phosphate solution is 1 to 800 mmol / h / L, and the addition acceleration of the aqueous solution C is 0.1 to 8 mmol / h / L.

7. The active substance precursor and the preparation method thereof according to claim 6, characterized in that: The dosing speed of the ammonia solution is 1-100 mmol / h / L, the dosing speed of the alkali solution is 1-100 mmol / h / L, the dosing speed of the phosphoric acid or phosphate solution is 1-100 mmol / h / L, and the dosing speed of the aqueous solution C is 0.8-3.2 mmol / h / L; The addition speeds of the phosphoric acid or phosphate solution, the ammonia solution and the alkaline solution are sequentially reduced to control the concentration of each solution.

8. The active substance precursor and the preparation method thereof according to claim 4, characterized in that: The metal salt aqueous solution A and the mixed solution are reacted at a temperature of 30 to 80° C. for 30 to 40 minutes; After the metal salt aqueous solution A and the metal salt aqueous solution B are mixed, the mixed solution is added simultaneously and reacted at a temperature of 30 to 80° C. for at least 20 to 60 hours.

9. The active substance precursor and the preparation method thereof according to claim 3, characterized in that: In the metal salt aqueous solution A and the metal salt aqueous solution B, the cation concentration is 0.5-2 mol / L, the iron salt solution is FeSO4 solution, and the manganese salt solution is MnSO4 solution; In the metal salt aqueous solution A, the molar ratio of FeSO4 to MnSO4 is 2:8 to 0.5:9.5; In the metal salt aqueous solution B, the molar ratio of FeSO4 to MnSO4 is 3:7 to 5:

5.

10. The active substance precursor and the preparation method thereof according to claim 3, characterized in that: The carbon source is glucose, which is processed to form a carbon-coated active material precursor with a core-shell structure having a concentration gradient, and the carbon coating content in the active material precursor is 0.5-3wt%.

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