A method for preparing a high-compaction lithium iron manganese phosphate cathode material

Abstract

The application discloses a method for preparing a high-compaction lithium manganese iron phosphate positive material, and belongs to the technical field of preparation of lithium manganese iron phosphate positive materials. In the preparation, first, a first manganese iron precursor is heat-treated at 300-800 DEG C under inert atmosphere for 2-10 hours to obtain a manganese iron oxide precursor; then, the manganese iron oxide precursor, a second manganese iron precursor, a lithium source, a phosphorus source and a carbon source are mixed, ground and dried according to stoichiometry, and then, natural cooling and crushing are conducted to obtain a carbon-coated lithium manganese iron phosphate positive material. The preparation process of the lithium manganese iron phosphate positive material adopts the method that part of the manganese iron precursor is heat-treated first, and then the heat-treated manganese iron precursor is mixed and sintered with the manganese iron precursor which is not heat-treated, so that in-situ particle grading can be achieved, and thus, the lithium manganese iron phosphate positive material with high-compaction density can be obtained, the lithium manganese iron phosphate positive material has excellent electrochemical performance, and the compaction density and the electrochemical performance are simultaneously improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of preparation of lithium manganese iron phosphate cathode material, and particularly relates to a method for preparing high-compaction lithium manganese iron phosphate cathode material. BACKGROUND

[0002] Lithium iron phosphate (LiFePO4) material has become an important cathode material in the fields of power batteries and energy storage batteries due to its excellent safety, cycle life and cost advantage. However, its working voltage platform is relatively low (about 3.4 V vs. Li + / Li) and the mass energy density has approached the theoretical limit, which limits its further development. Lithium manganese iron phosphate (LMFP) has a higher energy density by introducing manganese elements into lithium iron phosphate to increase the voltage platform to about 4.1 V, and is considered as a strong competitor of the next generation of phosphate-based cathode materials.

[0003] However, the intrinsic electronic conductivity and ionic conductivity of lithium manganese iron phosphate material are low, and usually need to be improved by carbon coating and nanocrystallization. Although nanocrystallization improves the rate performance, it also leads to low tap density and compaction density of the material, so that the volume energy density of the battery is limited. The volume energy density is crucial for the application scenarios of limited space such as electric vehicles and portable electronic devices.

[0004] In the prior art, in order to improve the compaction density, the commonly used method is to prepare micron-sized secondary spherical particles. However, this method may sacrifice the rate performance of the material because the ion diffusion path is long inside the large secondary particles. Another idea is to perform particle grading, that is, to optimize the combination of particles of different sizes so that small particles are filled into the gaps of large particles to improve the packing density. However, simply physically mixing LMFP powders of different particle sizes often fails to achieve a uniform and stable composite structure, and particle segregation is prone to occur during the preparation of electrode slurry.

[0005] Therefore, it is of great significance to develop a lithium manganese iron phosphate preparation method that can construct a stable particle size grading structure from the source of material synthesis, so as to simultaneously achieve high compaction density and excellent electrochemical performance. SUMMARY

[0006] The application provides a lithium manganese iron phosphate preparation method that can construct a stable particle size grading structure from the source of material synthesis, so as to simultaneously achieve high compaction density and excellent electrochemical performance.

[0007] Technical scheme: The method for preparing high-compaction lithium manganese iron phosphate cathode material comprises the following steps:

[0008] (1) heat treating the first manganese-iron precursor at 300-800 DEG C under inert atmosphere for 2-10h to obtain a manganese-iron oxide precursor;

[0009] (2) mixing, grinding and drying the manganese-iron oxide precursor, the second manganese-iron precursor, a lithium source, a phosphorus source according to stoichiometry, a carbon source and water, sintering at 600-800 DEG C under inert atmosphere for 5-20h, and then naturally cooling and crushing to obtain a carbon-coated manganese-iron lithium phosphate positive electrode material.

[0010] The present application first pre-heats part of the manganese-iron precursor to obtain a manganese-iron oxide precursor, and then blends and sinter the manganese-iron oxide precursor with the remaining manganese-iron precursor to form a multi-level synergistic mechanism of "crystal phase regulation-reaction kinetics design-microstructure self-assembly", which systematically solves the problem that high density and high performance are difficult to be considered in the existing traditional method. The core mechanism is that: the stable oxide phase formed by the first manganese-iron precursor through heat treatment is used as an inert skeleton to provide mechanical support; at the same time, the second manganese-iron precursor with high active salt phase is introduced as a reaction driving force source and a structure regulator, and in the blending and sintering process, the crystal phase difference between the two creates a "gradient reaction" environment, that is, the second manganese-iron precursor with high activity is decomposed first, and the high-activity substances and fine particles produced by the decomposition serve as "material transport bridge" and "solid adhesive", which greatly promotes the neck growth and fusion between the adjacent first manganese-iron precursor skeleton particles, thereby constructing in-situ a secondary large particle with high strength, stability and internal compactness; and the active substances that are not consumed form fine particles that fill the voids, and finally form an optimized particle size grading structure. The large-size particle skeleton provides high tap density and structural stability, the small-size particle ensures a short diffusion path of lithium ions, and the small-size particle can be filled between the large-size particles to make the packing of the prepared positive electrode material more compact, the porosity is significantly reduced, thereby greatly improving the compaction density of the material, and finally improving the volume energy density of the lithium ion battery using the material while having excellent electrochemical performance.

[0011] Specifically, from the perspective of particle size: through the step-by-step heat treatment and double-precursor mixed sintering strategy, a particle size grading structure conducive to close packing is spontaneously formed during sintering. The first manganese-iron precursor after heat treatment forms rigid skeleton particles with large size and low surface energy, while the second manganese-iron precursor without treatment is a small particle with high activity and high specific surface area. During mixing, small particles are easily adsorbed on the surface of large particles to form a "satellite-core" pre-assembly structure. In the high-temperature sintering stage, small particles attached to the surface of large particles first undergo surface softening or diffusion due to their high activity, becoming a "shortcut" for material transport, significantly promoting the further growth of large particles, making their size larger than that of the product sintered alone; in addition, small particles located at the contact points or gaps between large particles play a key role as "solid binder" or "material transport bridge": not only greatly accelerating the diffusion and deposition of material to the neck region, promoting the rapid merging of adjacent large particles into larger and denser secondary particles through sintering neck, but also filling the micropores and cracks inside each composite particle through diffusion, thereby significantly improving the degree of densification and strength inside each composite particle. The remaining dispersed small particles independently nucleate and grow to form smaller secondary particles, which are tightly packed in the gaps during the formation of large particles, forming a close packing. The final product exhibits a grading effect with large-size particles as the skeleton and small-size particles filling the gaps.

[0012] From the perspective of crystal phase: the difference in crystal phase between the two precursors in this preparation method is the key design for synergistic effect, and the essence of the difference lies in the kinetic complementarity of "stable phase" and "active phase". That is, the first manganese-iron precursor after heat treatment is converted into a thermodynamically stable manganese-iron oxide phase, which has low reactivity in subsequent sintering and mainly serves as an inert structural skeleton providing mechanical strength; while the second manganese-iron precursor remains in its original high-activity carbonate or oxalate phase. During mixed sintering, this crystal phase difference creates an ideal "gradient reaction" environment: the high-activity second manganese-iron precursor decomposes first and initiates rapid reaction with lithium and phosphorus sources, generating high-activity intermediate phases that not only form small lithium manganese iron phosphate grains (constituting filler particles), but also act as efficient "atomic transport media" to wrap and promote the diffusion of lithium / phosphorus components into the stable first manganese-iron precursor skeleton, thereby guiding the epitaxial growth of lithium manganese iron phosphate phase on its surface into dense large particles. This process not only spontaneously builds an optimized particle grading structure, but also ensures a high degree of uniform distribution of manganese and iron elements in the final product lattice at the atomic scale, thereby achieving high compaction density while effectively improving the material's crystal structure integrity and cycle stability.

[0013] Further, in the preparation of the lithium manganese iron phosphate positive electrode material, the mass ratio of the manganese-iron oxide precursor to the second manganese-iron precursor is (1:9)-(9:1).

[0014] Preferably, in the preparation of the lithium manganese iron phosphate cathode material, the heat treatment temperature of the first manganese iron precursor is 400-600℃.

[0015] Further, in the preparation of the lithium manganese iron phosphate cathode material, the first manganese iron precursor is selected from one or more of manganese iron carbonate, manganese iron hydroxide, manganese iron oxalate or manganese iron citrate complex, and the molar ratio of manganese to iron in the first manganese iron precursor is (4:6)-(8:2). The second manganese iron precursor is selected from one or more of manganese iron carbonate, manganese iron hydroxide, manganese iron oxalate or manganese iron citrate complex, and the molar ratio of manganese to iron in the second manganese iron precursor is (4:6)-(8:2).

[0016] Further, in the preparation of the lithium manganese iron phosphate cathode material, the molar ratio of manganese, iron in both the manganese iron oxide precursor and the second manganese iron precursor, phosphorus in the phosphorus source and lithium in the lithium source is x:(1-x):y:z, 0.4≤x<1, 1≤y≤1.05, 1.01≤z≤1.10. Preferably, the phosphorus source is selected from at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate or phosphoric acid; and the lithium source is selected from at least one of lithium carbonate, lithium hydroxide or lithium acetate.

[0017] Further, in the preparation of the lithium manganese iron phosphate cathode material, the amount of the carbon source added is 5-15% of the theoretical mass of the lithium manganese iron phosphate generated, and the carbon source is selected from at least one of glucose, sucrose, citric acid, polyethylene glycol or pitch.

[0018] Beneficial effects: Compared with the prior art, the preparation process of the lithium manganese iron phosphate can achieve in-situ particle size grading to obtain a lithium manganese iron phosphate cathode material with high compaction density, while having excellent electrochemical performance, realizing the simultaneous improvement of compaction density and electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The electron microscope image of the second precursor manganese iron carbonate without heat treatment in Example 1 of the present application;

[0020] Figure 2 The electron microscope image of the manganese iron oxide precursor in Example 1 of the present application;

[0021] Figure 3 The XRD pattern of the second precursor manganese iron carbonate without heat treatment and the manganese iron oxide precursor in Example 1 of the present application;

[0022] Figure 4 The electron microscope image of the lithium manganese iron phosphate cathode material prepared in Example 1 of the present application;

[0023] Figure 5 The electron microscope image of the lithium manganese iron phosphate cathode material prepared in Comparative Example 1 of the present application;

[0024] Figure 6 The electron microscope image of the lithium manganese iron phosphate positive electrode material prepared in the present application comparative example 2;

[0025] Figure 7 The electron microscope image of the lithium manganese iron phosphate positive electrode material prepared in the present application example 2;

[0026] Figure 8 The electron microscope image of the lithium manganese iron phosphate positive electrode material prepared in the present application example 3;

[0027] Figure 9 The electron microscope image of the lithium manganese iron phosphate positive electrode material prepared in the present application example 4;

[0028] Figure 10 The electron microscope image of the lithium manganese iron phosphate positive electrode material prepared in the present application comparative example 3;

[0029] Figure 11 The electron microscope image of the lithium manganese iron phosphate positive electrode material prepared in the present application comparative example 4. DETAILED DESCRIPTION

[0030] The technical solutions of the present application will be further described in detail below in combination with the examples and the drawings.

[0031] It should be noted that the raw materials used in the present application can be purchased from the market. The lithium source used is lithium carbonate, the phosphorus source is ammonium dihydrogen phosphate, and the carbon source is glucose. The addition amount of the carbon source is 10% of the theoretical mass of the generated lithium manganese iron phosphate. The inert atmosphere used in the following examples and comparative examples of the present application can be nitrogen or argon. The manganese iron precursor used is manganese iron carbonate or manganese iron oxalate, and the molar ratio of manganese to iron is 7:3, which is purchased from Guizhou Dalonghucheng New Material Co., Ltd.

[0032] In addition, the purpose of crushing in the following examples of the present application is to break up the agglomerates, and the particle size range is not specifically limited.

[0033] Example 1

[0034] The preparation method of the lithium manganese iron phosphate positive electrode material of this example 1 comprises the following steps:

[0035] (1) The manganese iron carbonate is used as the first manganese iron precursor, and is heat treated at 500°C for 5h under a nitrogen atmosphere to obtain a manganese iron oxide precursor.

[0036] (2) The manganese iron oxide precursor obtained in step (1), manganese iron carbonate (second manganese iron precursor), lithium carbonate (lithium source), ammonium dihydrogen phosphate (phosphorus source) were weighed according to the molar ratio of Li:(Mn+Fe):P = 1.03:1:1, mixed with glucose (carbon source), and deionized water was added to make a slurry, which was mixed, dispersed and ground for 4 h, and then dried at 120°C; the mass ratio of the manganese iron oxide precursor to the second manganese iron precursor was 1:1.

[0037] (3) The dried mixture was sintered at 700°C for 12 h under the protection of a nitrogen atmosphere, naturally cooled in the furnace, and crushed to obtain a carbon-coated lithium manganese iron phosphate material.

[0038] Comparative Example 1

[0039] Comparative Example 1 was basically the same as Example 1, except that the manganese iron precursor was not pre-treated. Specifically, the following steps were included:

[0040] (1) Manganese iron carbonate (manganese iron precursor), lithium carbonate (lithium source), ammonium dihydrogen phosphate (phosphorus source) were weighed according to the molar ratio of Li:(Mn+Fe):P = 1.03:1:1, mixed with glucose (carbon source), and deionized water was added to make a slurry, which was mixed, dispersed and ground for 4 h, and then dried at 120°C.

[0041] (2) The dried mixture was sintered at 700°C for 12 h under the protection of a nitrogen atmosphere, naturally cooled in the furnace, and crushed to obtain a carbon-coated lithium manganese iron phosphate material.

[0042] Comparative Example 2

[0043] Comparative Example 2 was basically the same as Example 1, except that only the manganese iron oxide precursor obtained after heat treatment was used. Specifically, the following steps were included:

[0044] (1) The manganese iron carbonate was heat-treated at 500°C for 5 h under a nitrogen atmosphere to obtain a manganese iron oxide precursor.

[0045] (2) The manganese iron oxide precursor, lithium carbonate (lithium source), ammonium dihydrogen phosphate (phosphorus source) were weighed according to the molar ratio of Li:(Mn+Fe):P = 1.03:1:1, mixed with glucose (carbon source), and deionized water was added to make a slurry, which was mixed, dispersed and ground for 4 h, and then dried at 120°C.

[0046] (3) The dried mixture was sintered at 700°C for 12 h under the protection of a nitrogen atmosphere, naturally cooled in the furnace, and crushed to obtain a carbon-coated lithium manganese iron phosphate material.

[0047] Example 2

[0048] The basic steps are the same as those of Example 1, except that the mass ratio of the manganese-iron oxide precursor to the second manganese-iron precursor is 7:3.

[0049] Example 3

[0050] The basic steps are the same as those of Example 1, except that the mass ratio of the manganese-iron oxide precursor to the second manganese-iron precursor is 3:7.

[0051] Example 4

[0052] The basic steps are the same as those of Example 1, except that the first manganese-iron precursor is replaced by manganese iron oxalate, and the heat treatment temperature is 450℃, and the time is 8h. The specific steps are as follows:

[0053] (1) The manganese iron oxalate is used as the first manganese-iron precursor, and is heat treated at 450℃ for 8h under a nitrogen atmosphere to obtain a manganese-iron oxide precursor.

[0054] (2) The manganese-iron oxide precursor obtained in step (1), manganese iron carbonate (second manganese-iron precursor), lithium carbonate (lithium source), ammonium dihydrogen phosphate (phosphorus source) are weighed according to the molar ratio of Li:(Mn+Fe):P = 1.03:1:1, mixed with glucose (carbon source), and deionized water is added to make a slurry, which is mixed, dispersed and ground for 4h, and then dried at 120℃; wherein the mass ratio of the manganese-iron oxide precursor to the second manganese-iron precursor is 1:1.

[0055] (3) The dried mixture is sintered at 700℃ for 12h under the protection of a nitrogen atmosphere, and is naturally cooled in the furnace and crushed to obtain a carbon-coated manganese iron lithium phosphate material.

[0056] Comparative Example 3

[0057] This comparative example 3 is basically the same as Example 4, except that the manganese-iron precursor is not pre-heat treated.

[0058] Comparative Example 4

[0059] This comparative example 4 is basically the same as Example 4, except that only the heat-treated manganese-iron oxide precursor is used.

[0060] Performance Test 1 - Compaction Degree

[0061] The lithium manganese iron phosphate positive electrode materials prepared in the above Examples 1-4 and Comparative Examples 1-4 are tested for compaction density using a PRCD1100 type powder compaction test device according to GBT30835-2014, and the results obtained are shown in Table 1.

[0062] Performance Test 2 - Electrochemical Performance

[0063] The lithium manganese iron phosphate positive electrode materials obtained in the above Examples 1-4 and Comparative Examples 1-4 were prepared into button cells using the following method and subjected to electrochemical performance evaluation. Specifically:

[0064] The lithium manganese iron phosphate positive electrode material, Super P (conductive carbon black) and PVDF were uniformly mixed in an NMP solution at a ratio of 95:5:5 to obtain a mixed slurry, the slurry was coated on a bright aluminum foil by hand coating, then dried at 100°C, after the NMP was completely volatilized, the electrode sheet was punched into a diameter of 13mm, then the electrode sheet was placed in a vacuum oven at 105°C overnight, after weighing the electrode sheet, it was quickly transferred to a glove box, with lithium metal as the counter electrode, Celgard 2400 as the separator, and the electrolyte being 1 mol / L LiPF6 dissolved in EC / DMC / EMC (volume ratio 1:1:1) mixed solvent, the assembled battery; the electrochemical performance test was carried out by using a new Wei test system, and the test method of constant current-constant voltage charging (CC-CV) and constant current discharging (DC) was used to test and analyze the charge-discharge behavior of the button cell, and the test voltage range was 2.0-4.35 V. The results obtained are shown in Table 1 below.

[0065] Table 1 is the test data of the positive electrode materials of Examples 1 to 4 and Comparative Examples 1 to 4.

[0066] Example Compaction (g / cm 3 ) 0.1 C discharge capacity (mAh / g) 1 C discharge capacity (mAh / g) Example 1 2.45 153 143 Comparative Example 1 2.30 156 148 Comparative Example 2 2.40 150 138 Example 2 2.47 151 141 Example 3 2.43 155 145 Example 4 2.44 153 143 Comparative Example 3 2.32 155 146 Comparative Example 4 2.38 151 139

[0067] Performance detection 3-structure characterization

[0068] The second precursor manganese iron carbonate, manganese iron oxide precursor of Example 1 of the application was subjected to structure characterization and XRD detection, and the results obtained are shown in Figures 1 to 3 . Figure 1 The micro-morphology of the second precursor manganese iron carbonate in Example 1 is characterized by flocculent amorphous, and the manganese iron oxide obtained after high-temperature treatment at 500°C for 5h is composed of multiple small particles, as shown in Figure 2 . At the same time, the XRD patterns of the manganese iron carbonate and the manganese iron oxide precursor are compared, that is, Figure 3 , which verifies that the high-temperature treatment brings the following changes to the manganese iron carbonate: (1) the crystallinity is improved, and the particles are fused and grown; (2) the crystal type is changed from carbonate to oxide.

[0069] According to the compaction density in Table 1, the compaction density of Example 1 is obviously improved compared with Comparative Examples 1 and 2. At the same time, the SEM images of the lithium manganese iron phosphate positive electrode material prepared in Example 1, Figure 4 the SEM images of the lithium manganese iron phosphate positive electrode material prepared in Comparative Example 1, and Figure 5 the SEM images of the lithium manganese iron phosphate positive electrode material prepared in Comparative Example 2 are compared. Figure 6The electron microscope image of the lithium manganese iron phosphate positive electrode material prepared in Comparative Example 2 shows that Comparative Example 1 (i.e. Figure 5 ) synthesized from single untreated manganese iron carbonate is a large number of small particles, and Comparative Example 2 (i.e. Figure 6 ) synthesized from single manganese iron oxide is medium particles. However, the material of Example 1 obviously presents a size particle grading morphology (i.e. Figure 4 ), and the small particles are uniformly filled in the gaps of the large particles. And in the high-temperature sintering process, the "fusion and connection" effect of the small particles leads to further growth of the large particles, which are larger than those of Comparative Example 2; at the same time, due to the same reason, the material transfer of the small particles leads to the growth of the small particles themselves, which are smaller than the single (Comparative Example 1). Finally, as shown in Table 1, the excellent electrical performance of Example 1 is achieved, and the synchronous improvement of the compaction density and the electrochemical performance is achieved.

[0070] Examples 2 and 3 adjust the ratio of the two precursors compared to Example 1, and the adjustment within the appropriate range does not change the grading effect, as shown in Figure 7 and Figure 8 , small particles can also be observed in the gaps of large particles in Figure 7 and Figure 8 . Further combined with Table 1, Example 2 increases the proportion of manganese iron oxide from 5 to 7, and the increase of large particles results in the increase of compaction; and Example 3 is opposite, and the proportion of the second manganese iron precursor manganese iron carbonate is increased, and more small particles fill in to optimize the electrical performance.

[0071] Example 4, Comparative Example 3 and Comparative Example 4 also present similar effects as carbonates by using manganese iron oxalate as a precursor to synthesize lithium manganese iron phosphate, which further verifies that the design of the double precursor realizes a stable and uniform particle grading structure, greatly improves the compaction density of lithium manganese iron phosphate, and still has good electrical performance.

[0072] In addition to the above examples, it should be noted that the technical idea of the present application can achieve the technical effects claimed in the present application. For the parameters in the specific preparation process, the range defined in the present application can achieve the above effects, and therefore no further experimental evidence is required.

[0073] For example, the first manganese iron precursor can be heat treated at a temperature of 300-800 °C, preferably 400-600 °C. The heat treatment time can be 2-10 h. The mass ratio of the manganese iron oxide precursor to the second manganese iron precursor can be (1 :9) - (9: 1). Preferably, it can be (3:7) - (7:3). The manganese iron molar ratio in the first manganese iron precursor and the second manganese iron precursor can both be (4:6) - (8:2). The first manganese iron precursor can also be selected from one or more of manganese iron hydroxide, manganese iron oxalate, or manganese iron citrate complex; the second manganese iron precursor can also be selected from one or more of manganese iron hydroxide, manganese iron oxalate, or manganese iron citrate complex; both can be the same or different substances.

Claims

1. A method for preparing high-pressure lithium manganese iron phosphate cathode material, characterized in that, Includes the following steps: (1) The first manganese-iron precursor was heat-treated at 300-800℃ under an inert atmosphere for 2-10h to obtain manganese-iron oxide precursor; (2) The manganese iron oxide precursor, the second manganese iron precursor, the lithium source, the phosphorus source, the carbon source, and water are mixed, ground, and dried according to stoichiometry. Then, the mixture is sintered in an inert atmosphere at 600-800℃ for 5-20 hours and then naturally cooled and crushed to obtain carbon-coated manganese iron lithium cathode material. The mass ratio of the manganese iron oxide precursor to the second manganese iron precursor is (1:9)-(9:1); the molar ratio of manganese iron in both the first and second manganese iron precursors is (4:6)-(8:2). The molar ratio of manganese and iron in the manganese iron oxide precursor and the second manganese iron precursor, and phosphorus and lithium in the phosphorus source and lithium source is x:(1-x):y:z, 0.4≤x<1, 1≤y≤1.05, 1.01≤z≤1.

10.

2. The method for preparing high-pressure lithium manganese iron phosphate cathode material according to claim 1, characterized in that, The heat treatment temperature of the first manganese-iron precursor is 400-600℃.

3. The method for preparing high-pressure lithium manganese iron phosphate cathode material according to claim 1, characterized in that, The first ferromanganese precursor is selected from one or more of ferromanganese carbonate, ferromanganese oxyhydroxide, ferromanganese oxalate, or ferromanganese citrate complexes.

4. The method for preparing high-pressure lithium manganese iron phosphate cathode material according to claim 1, characterized in that, The second ferromanganese precursor is selected from one or more of ferromanganese carbonate, ferromanganese oxyhydroxide, ferromanganese oxalate, or ferromanganese citrate complexes.

5. The method for preparing high-pressure lithium manganese iron phosphate cathode material according to claim 1, characterized in that, The phosphorus source is selected from at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, or phosphoric acid; the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, or lithium acetate.

6. The method for preparing high-pressure lithium manganese iron phosphate cathode material according to claim 1, characterized in that, The amount of carbon source added is 5-15% of the theoretical mass of lithium manganese iron phosphate, and it is selected from at least one of glucose, sucrose, citric acid, polyethylene glycol or asphalt.

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