Phosphate positive electrode material precursor and preparation method and application thereof

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a phosphate positive electrode material precursor and a preparation method and application thereof. The preparation method comprises the following steps: firstly, mixing ammonia water with water to obtain a complexing agent A; dissolving iron metal salt and manganese metal salt in water to obtain a solution B; dissolving hydroxide in water to obtain a precipitant C; finally, mixing the oxide with water to obtain an oxidizing agent D; and finally, sequentially adding the solution B, the precipitant C and the oxidizing agent D into the complexing agent A, and reacting to obtain the product. The preparation method of the phosphate positive electrode material precursor is simple in technological process and low in cost, compared with other processes, the phosphate positive electrode material precursor which is high in specific surface area, high in activity, beneficial to later processing and grinding and uniform in mixing of iron and manganese elements can be obtained, high-temperature sintering is not needed, the iron and manganese elements are adjustable, and the preparation method is suitable for industrial production. The method is suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and in particular relates to a phosphate positive electrode material precursor and a preparation method and application thereof. Background Art

[0002] Lithium iron manganese phosphate is a solid solution material composed of lithium iron phosphate and lithium manganese phosphate. It has similar properties to lithium iron phosphate and lithium manganese phosphate, with excellent thermal and chemical stability. Compared to lithium iron phosphate, lithium manganese iron phosphate has a higher voltage platform and improved electrical conductivity and lithium ion conductivity.

[0003] Similar to lithium iron phosphate, lithium iron manganese phosphate precursor has a direct impact on the performance of the final product. Different preparation methods lead to great differences in the structure, morphology, specific surface area and electrochemical properties of the prepared materials. Currently, the common preparation methods of lithium iron manganese phosphate precursors include solid-phase synthesis, chemical co-precipitation, sol-gel method, hydrothermal synthesis and spray degradation method.

[0004] For example, Chinese invention patent publication number CN119490169A discloses a method for preparing a high-density iron-manganese phosphate precursor. The method comprises: mixing a complexed metal salt solution with a phosphorus source solution, adding an oxidant and an alkaline solution, and simultaneously passing oxygen through the solution. Finally, the precursor is filtered, dried, and sintered to prepare the iron-manganese phosphate precursor. The precursor has uniform iron and manganese distribution and stable properties, but the preparation process requires the introduction of oxygen and high-temperature sintering, which is costly.

[0005] Another Chinese invention patent publication number CN114212764A discloses a phosphate cathode material precursor, its preparation method and application. The preparation method of the phosphate cathode material precursor comprises: mixing a cation source and a phosphate aqueous solution to obtain a mixed solution, wherein the cation source comprises a Mn source, a Co source, a Ni source and an M source; reacting the mixed solution at 50-90°C to obtain a reaction liquid; finally, extracting the reaction liquid with an organic solvent to separate a precipitate, and washing and drying the precipitate to obtain the phosphate cathode material precursor. However, this invention uses a large amount of organic solvent, which not only increases production costs but also increases environmental costs (generation of waste liquid), which is not conducive to large-scale production.

[0006] Another Chinese invention patent publication number CN115893354A discloses a method for preparing a phosphate positive electrode material precursor and its application. The method can generate aggregated manganese phosphate by reacting manganese tetraoxide with phosphoric acid under normal pressure and heating conditions. The entire reaction process is simple to operate and environmentally friendly, avoiding the use of organic solvents and oxidants. The phosphate positive electrode material precursor can be used to prepare excellent lithium manganese iron phosphate or excellent lithium manganese phosphate phosphate positive electrode materials. However, the invention requires high-temperature calcination to obtain the phosphate positive electrode material precursor, which is costly and has a significant impact on the material's circulation, compaction and other properties.

[0007] In view of this, there is an urgent need in the art to provide a phosphate cathode material precursor with low cost, simple process flow, and uniform element mixing. Summary of the Invention

[0008] The present invention addresses the problems of the prior art and provides a phosphate cathode material precursor, its preparation method, and application. By using a complexing agent as a base liquid, adding a mixed metal salt solution of iron and manganese, then adding a precipitant and an oxidant for coprecipitation and oxidation, and finally washing and drying, a phosphate cathode material precursor containing a uniform mixture of iron and manganese elements, a high specific surface area, and small particle size is obtained. This preparation process is simple, environmentally friendly, and suitable for industrial application.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing a phosphate cathode material precursor comprises the following steps: (1) Mix ammonia water with water to obtain complexing agent A; then dissolve iron metal salt and manganese metal salt in water to obtain solution B; then dissolve hydroxide in water to obtain precipitant C; finally, mix oxide with water to obtain oxidant D; (2) Add solution B, precipitant C and oxidant D to complexing agent A in sequence and react to obtain the product.

[0010] Preferably, the iron salt in step (1) is selected from one or more of ferric sulfate, ferric nitrate and ferric chloride.

[0011] Preferably, the hydroxide in step (1) is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water.

[0012] Preferably, the concentration of the complexing agent A in step (1) is 3-10 mol / L.

[0013] More preferably, the concentration of the complexing agent A in step (1) is 5-8 mol / L.

[0014] Preferably, the manganese salt in step (1) is selected from one or more of manganese sulfate, manganese nitrate, manganese chloride and manganese citrate.

[0015] Preferably, the total metal concentration of the solution B in step (1) is 1-3 mol / L, and the molar ratio of manganese to iron in the solution B is 0.5-0.9:0.1-0.5.

[0016] Preferably, the concentration of the precipitant C in step (1) is 6-12 mol / L.

[0017] Preferably, the oxide in step (1) is selected from one or more of sodium peroxide, hydrogen peroxide and ozone, and the concentration of the oxidant D is 3-9.8 mol / L. More preferably, the oxide is hydrogen peroxide.

[0018] Preferably, during the reaction in step (2), the ratio of the molar amount of complexing ions in the complexing agent A to the total molar amount of iron ions and manganese ions in solution B is 0.5-2:1; the ratio of the molar amount of hydroxide ions in the precipitant C to the total molar amount of iron ions and manganese ions in solution B is 1.8-2.6:1; and the ratio of the molar amount of the oxidant D to the total molar amount of iron ions and manganese ions in solution B is 0.6-1.0:1.

[0019] Preferably, the time for sequentially adding solution B, precipitant C and oxidant D in step (2) is 10-120 min, and the temperature for sequentially adding solution B, precipitant C and oxidant D is 30-80°C; and the addition is carried out at a speed of 250-600 rpm.

[0020] Preferably, the reaction conditions in step (2) are: pH = 10-12, 30-80 ° C, and 3-6 h.

[0021] Preferably, after the reaction in step (2) is completed, filtration is performed, washing with water until the conductivity is ≤300 μS / cm, and finally drying is performed at 60-90° C. for 12-24 h.

[0022] The present invention also provides a phosphate positive electrode material precursor prepared by the above preparation method.

[0023] A lithium iron manganese phosphate / carbon composite material comprises the above-mentioned phosphate positive electrode material precursor.

[0024] The present invention also provides the use of the above-mentioned phosphate positive electrode material precursor in the preparation of lithium iron manganese phosphate / carbon composite material.

[0025] Preferably, the method for preparing a lithium iron manganese phosphate / carbon composite material comprises the following steps: mixing a phosphate positive electrode material precursor, a lithium salt, a phosphate salt and an additive in a liquid phase system, and calcining to obtain a lithium iron manganese phosphate precursor; then mixing the lithium iron manganese phosphate precursor with a carbon source in a liquid phase system, and sintering to obtain the composite material.

[0026] Preferably, the lithium salt is selected from one or more of lithium carbonate, lithium hydroxide, lithium phosphate and lithium dihydrogen phosphate.

[0027] Preferably, the phosphorus source is selected from one or more of ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, ammonium phosphate, lithium dihydrogen phosphate and lithium phosphate.

[0028] Preferably, the additive is selected from one or more of titanium dioxide, tetrabutyl titanate, magnesium hydroxide, magnesium oxide, magnesium acetate, magnesium nitrate, zirconium dioxide, zirconium hydroxide, niobium pentoxide, nickel acetate and nickel oxide.

[0029] Preferably, the ratio of the total molar amount of iron ions and manganese ions, the molar amount of lithium salt and the molar amount of phosphorus salt in the phosphate positive electrode material precursor is 1:1-1.1:1-1.1.

[0030] Preferably, the mass of the additive accounts for 0-5% of the mass of the phosphate positive electrode material precursor.

[0031] More preferably, the mass of the additive accounts for 1-2% of the mass of the phosphate positive electrode material precursor.

[0032] Preferably, the carbon source is selected from one or more of glucose, crystal sugar, sucrose, fructose, polyethylene glycol, cyclodextrin, starch and cellulose.

[0033] Preferably, the liquid phase system is selected from water, ethanol or methanol.

[0034] Preferably, grinding and drying are performed after the mixing is completed.

[0035] Preferably, the grinding includes coarse grinding to a particle size of D50=1-2 μm and fine grinding to a particle size of D50=300-500 nm.

[0036] Preferably, the drying is spray drying, and the inlet temperature of the spray drying is 250-270°C and the outlet temperature is 95-105°C.

[0037] Preferably, the calcination temperature is 400-700° C., the calcination time is 2-6 h, and the calcination atmosphere is nitrogen, argon or helium.

[0038] Preferably, the sintering temperature is 675-780° C., the sintering time is 4-10 h, and the sintering atmosphere is nitrogen, argon or helium.

[0039] Preferably, the carbon content in the lithium iron manganese phosphate / carbon composite material is 1.2-2%.

[0040] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention provides a method for preparing a phosphate cathode material precursor with a simple process flow and low cost. Compared with other processes, the present invention uses a chelating agent as a base liquid, first adds a mixed metal salt solution of iron and manganese, then adds a precipitant and an oxidant for co-precipitation and oxidation, and finally washes and dries to obtain a phosphate cathode material precursor with a uniform mixture of iron and manganese elements. No high-temperature sintering is required, and the iron and manganese elements are adjustable, which is suitable for industrial production.

[0041] (2) The phosphate cathode material precursor provided by the present invention has a high specific surface area and high activity, which is conducive to subsequent processing and grinding.

[0042] (3) The present invention also provides a method for preparing a lithium iron manganese phosphate / carbon composite material, which comprises mixing and grinding a homemade phosphate positive electrode material precursor with a lithium source, phosphoric acid, and an additive, sintering the mixture, and then mixing and grinding the mixture with a carbon source, and solid-phase sintering the mixture to finally prepare a lithium iron manganese phosphate / carbon composite material with excellent performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is an SEM photograph of the phosphate positive electrode material precursor prepared in Example 1.

[0044] Figure 2 This is the XRD pattern of the phosphate positive electrode material precursor prepared in Example 1.

[0045] Figure 3 This is an SEM photograph of the lithium iron manganese phosphate / carbon composite material prepared in Example 1.

[0046] Figure 4 This is a charge and discharge curve diagram of the lithium iron manganese phosphate / carbon composite material prepared in Example 1. DETAILED DESCRIPTION

[0047] It is worth noting that the raw materials used in the present invention are all common commercially available products. Among them, ammonia water, mass fraction, 25%; ferric nitrate nonahydrate, purity, 99%; manganese nitrate solution, mass concentration, 50%; sodium hydroxide, purity, 96%; potassium hydroxide, purity, 99.5%; hydrogen peroxide solution, mass concentration, 30%; lithium carbonate, purity, 99.5%; ammonium dihydrogen phosphate, purity, 99%; hydrated ferric sulfate, iron content, 22%; ferric chloride hexahydrate, purity, 99%; manganese chloride tetrahydrate, purity, 99%; ferrous sulfate heptahydrate, purity, 99%; and manganese sulfate monohydrate, purity, 99.99%.

[0048] Example 1 1. Preparation of phosphate cathode material precursor: (1) First, weigh 374.29 mL of ammonia water and mix it with 577.88 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 816.14 g of ferric nitrate nonahydrate and 1073.69 g of manganese nitrate solution, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.6:0.4). Then, weigh 437.47 g of sodium hydroxide and dissolve it in 1050.01 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 340.20 g of hydrogen peroxide solution and mix it with 680.40 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0049] (2) At 30°C, complexing agent A was added to the glass reactor as the base liquid, and then solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. Finally, the ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 1; then, precipitant C was added dropwise to the glass reactor at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. Finally, the ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2.1; finally, the temperature was raised to 40°C, and oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.6. The reaction was maintained at 40°C for 3 h, with a pH of 10.30. After completion of the reaction, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 405.50 g of a phosphate cathode material precursor.

[0050] After testing and analysis, the Na content of the phosphate cathode material precursor is 71.99 ppm and the specific surface area is 160.11m 2 / g; Fe content is 26.73%, Mn content is 39.85%, and the molar ratio Mn / Fe is calculated to be 0.602:0.398, Fe yield is 97.05%, and Mn yield is 98.04%. The phosphate cathode material precursor was observed by scanning electron microscopy ( Figure 1 ) and XRD characterization ( Figure 2 ).from Figure 1It can be seen that the primary particles of the phosphate cathode material precursor are spherical, with uniform particle size, about 50 nm, and are uniformly dense and clustered. Figure 2 It can be seen that the diffraction peaks of the phosphate cathode material precursor correspond to the Mn3O4 standard card (PDF card number #80-0382), without any extraneous peaks, indicating that the preparation method can achieve uniform co-precipitation of iron and manganese elements, thereby obtaining iron-manganese oxides with higher purity.

[0051] 2. Preparation of lithium iron manganese phosphate / carbon composite material: (1) The raw materials of the phosphate cathode material precursor were added in a ratio of 1:1.05:1.03, based on the total molar amount of iron ions and manganese ions, the molar amount of lithium salt, and the molar amount of phosphate salt. 400.00 g of the phosphate cathode material precursor prepared above, 187.77 g of lithium carbonate, 576.41 g of ammonium dihydrogen phosphate, 3.50 g of titanium dioxide, and 1.50 g of magnesium oxide were added to 1500 mL of pure water in sequence. The mixture was placed in a basket mill and ground at 2000 r / min for 50 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the finely ground slurry particle size reached D50 = 300 nm, it was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). The product was then calcined in a box furnace under a nitrogen atmosphere at 600°C for 4 h. After the box furnace was naturally cooled to 80°C, the calcined material was crushed to obtain 721.83 g of pre-lithiated lithium manganese iron phosphate precursor.

[0052] (2) 700.00 g of pre-lithiated lithium manganese iron phosphate precursor, 56.00 g of glucose, and 50.00 g of polyethylene glycol 20000 were added to 1500 mL of pure water in sequence, and placed in a basket grinder and ground at 2000 r / min for 40 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the slurry particle size after fine grinding reached D50 = 300 nm, the slurry was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). It was then placed in a box furnace under a nitrogen atmosphere for sintering at a sintering temperature of 700 ° C and kept at a constant temperature for 6 h. After the box furnace was naturally cooled to 80 ° C, the sintered material was graded and crushed to finally obtain LiFe with a carbon content of 1.49%. 0.4 Mn 0.6 PO4 / C composite material.

[0053] The prepared LiFe 0.4 Mn 0.6 PO4 / C composite materials were observed by scanning electron microscopy ( Figure 3 ).from Figure 3 It can be seen that the primary particles of the composite material are quasi-spherical, with uniform particle size, a particle size distribution range of 1500-400 nm, and the particle size is mainly concentrated around 200 nm.

[0054] Prepared LiFe 0.4 Mn 0.6 PO4 / C composite material is used as the positive electrode material, acetylene black is used as the conductive agent, and polytetrafluoroethylene is used as the binder to make the electrode sheet. Metal lithium is used as the negative electrode to assemble into a button battery. At 2-4.3 V and 25℃, different charge and discharge current conditions are used for testing. The discharge curve results are shown in the figure. Figure 4 The initial reversible capacity at 0.1C charge and discharge is 156.3 mAh / g, and the first efficiency at 0.1C is 98.8%; the initial reversible capacity at 0.2C charge and discharge is 153.2 mAh / g, and the 0.2C, 3.3 V platform efficiency is 94.6%; the initial reversible capacity at 1C charge and discharge is 146.5 mAh / g, and the capacity retention rate after 100 cycles at 1C is 97.2%.

[0055] Example 2 1. Preparation of phosphate cathode material precursor: (1) First, weigh 374.29 mL of ammonia water and mix it with 577.88 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 1020.18 g of ferric nitrate nonahydrate and 894.74 g of manganese nitrate solution, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.5:0.5). Then, weigh 437.47 g of sodium hydroxide and dissolve it in 1050.01 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 340.20 g of hydrogen peroxide solution and mix it with 680.40 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0056] (2) At 30°C, complexing agent A was added to the glass reactor as the base liquid, and then solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. Finally, the ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 1; then, precipitant C was added dropwise to the glass reactor at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. Finally, the ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2.1; finally, the temperature was raised to 40°C, and oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.6. The reaction was maintained at 40°C for 3 h, and the pH of the reaction system reached 10.27. After the reaction was complete, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 411.25 g of a phosphate cathode material precursor.

[0057] After testing and analysis, the Na content of the phosphate cathode material precursor is 64.59 ppm and the specific surface area is 172.61m 2 / g; the Fe content is 33.15%, the Mn content is 32.56%, and the molar ratio Mn / Fe is calculated to be 0.499:0.501, the Fe yield is 97.65%, and the Mn yield is 97.49%.

[0058] 2. Preparation of lithium iron manganese phosphate / carbon composite material: (1) The raw materials of the phosphate cathode material precursor were added in a ratio of 1:1.06:1.02, based on the total molar amount of iron ions and manganese ions, the molar amount of lithium salt, and the molar amount of phosphate salt. 400.00 g of the phosphate cathode material precursor prepared above, 186.77 g of lithium carbonate, 576.41 g of ammonium dihydrogen phosphate, 3.50 g of titanium dioxide, and 3.00 g of magnesium hydroxide were added to 1500 mL of pure water in sequence. The mixture was placed in a basket mill and ground at a speed of 2000 r / min for 50 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the finely ground slurry particle size reached D50 = 300 nm, it was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). The product was then calcined in a box furnace under a nitrogen atmosphere at 650°C for 5 h. After the box furnace was naturally cooled to 80°C, the calcined material was crushed to obtain 744.52 g of pre-lithiated lithium manganese iron phosphate precursor.

[0059] (2) 700.00 g of pre-lithiated lithium manganese iron phosphate precursor, 56.00 g of crystal sugar, and 40.00 g of polyethylene glycol 20000 were added to 1500 mL of pure water in sequence, and placed in a basket grinder and ground at 2000 r / min for 40 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the slurry particle size after fine grinding reached D50 = 320 nm, the slurry was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). It was then placed in a box furnace under a nitrogen atmosphere for sintering at a sintering temperature of 690 ° C for 8 hours. After the box furnace was naturally cooled to 80 ° C, the sintered material was graded and crushed to finally obtain LiFe with a carbon content of 1.42%. 0.5 Mn 0.5 PO4 / C composite material.

[0060] Prepared LiFe 0.5 Mn 0.5 The PO4 / C composite material was used as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder to form the electrode sheet. The battery was assembled into a button-type cell with metallic lithium as the negative electrode. Testing at 2-4.3 V and 25°C using various charge and discharge current conditions revealed an initial reversible capacity of 156.7 mAh / g at 0.1C, with a first efficiency of 98.1% at 0.1C. At 0.2C, the initial reversible capacity reached 154.3 mAh / g, with a plateau efficiency of 94.3% at 0.2C and 3.3 V. At 1C, the initial reversible capacity reached 147.5 mAh / g, with a capacity retention of 96.8% after 100 cycles at 1C.

[0061] Example 3 1. Preparation of phosphate cathode material precursor: (1) First, weigh 374.29 mL of ammonia water and mix it with 577.88 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 612.11 g of ferric nitrate nonahydrate and 1252.64 g of manganese nitrate solution, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.7:0.3). Then, weigh 437.47 g of sodium hydroxide and dissolve it in 1050.01 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 340.20 g of hydrogen peroxide solution and mix it with 680.40 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0062] (2) At 30°C, complexing agent A was added to the glass reactor as the base liquid, and then solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. Finally, the ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 1; then, precipitant C was added dropwise to the glass reactor at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. Finally, the ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2.1; finally, the temperature was raised to 40°C, and oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.6. The reaction was maintained at 40°C for 3 h, and the pH of the reaction system reached 10.58. After completion of the reaction, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 407.04 g of a phosphate cathode material precursor.

[0063] After testing and analysis, the Na content of the phosphate cathode material precursor is 96.79 ppm and the specific surface area is 166.30m 2 / g; the Fe content is 20.48%, the Mn content is 46.74%, and the molar ratio Mn / Fe is calculated to be 0.698:0.302, the Fe yield is 99.52%, and the Mn yield is 98.94%.

[0064] 2. Preparation of lithium iron manganese phosphate / carbon composite material: (1) The raw materials of the phosphate cathode material precursor were added in a ratio of 1:1.06:1.03, based on the total molar amount of iron ions and manganese ions, the molar amount of lithium salt, and the molar amount of phosphate salt. 400.00 g of the phosphate cathode material precursor prepared above, 191.69 g of lithium carbonate, 582.88 g of ammonium dihydrogen phosphate, 1.50 g of niobium pentoxide, and 4.50 g of magnesium carbonate were added to 1500 mL of pure water in sequence. The mixture was placed in a basket mill and ground at a speed of 2000 r / min for 50 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the finely ground slurry particle size reached D50 = 300 nm, it was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). The product was then calcined in a box furnace under a nitrogen atmosphere at 500°C for 6 h. After the box furnace was naturally cooled to 80°C, the calcined material was crushed to obtain 731.22 g of pre-lithiated lithium manganese iron phosphate precursor.

[0065] (2) 700.00 g of pre-lithiated lithium manganese iron phosphate precursor, 56.00 g of fructose, and 24.00 g of glucose were added to 1500 mL of pure water in sequence, and placed in a basket grinder and ground at 2000 r / min for 40 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the slurry particle size after fine grinding reached D50 = 320 nm, the slurry was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). It was then placed in a box furnace under a nitrogen atmosphere for sintering at a sintering temperature of 690 ° C and kept at a constant temperature for 8 h. After the box furnace was naturally cooled to 80 ° C, the sintered material was graded and crushed to finally obtain LiFe with a carbon content of 1.54%. 0.3 Mn 0.7 PO4 / C composite material.

[0066] Prepared LiFe 0.3 Mn 0.7 The PO4 / C composite material was used as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder to form the electrode sheet. The battery was assembled into a button-type cell with metallic lithium as the negative electrode. Testing at 2-4.3 V and 25°C using various charge and discharge current conditions revealed an initial reversible capacity of 154.6 mAh / g at 0.1C, with a first efficiency of 97.8% at 0.1C. At 0.2C, the initial reversible capacity was 152.3 mAh / g, with a plateau efficiency of 94.9% at 0.2C and 3.3 V. At 1C, the initial reversible capacity was 145.5 mAh / g, with a capacity retention of 96.8% after 100 cycles at 1C.

[0067] Example 4 1. Preparation of phosphate cathode material precursor: (1) First, weigh 374.29 mL of ammonia water and mix it with 577.88 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 408.07 g of ferric nitrate nonahydrate and 1431.58 g of manganese nitrate solution, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.8:0.2). Then, weigh 437.47 g of sodium hydroxide and dissolve it in 1050.01 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 340.20 g of hydrogen peroxide solution and mix it with 680.40 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0068] (2) At 30°C, complexing agent A was added to the glass reactor as the base liquid, and then solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. Finally, the ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 1; then, precipitant C was added dropwise to the glass reactor at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. Finally, the ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2.1; finally, the temperature was raised to 40°C, and oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.6. The reaction was maintained at 40°C for 3 h, and the pH of the reaction system reached 10.86. After the reaction was complete, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 401.32 g of a phosphate cathode material precursor.

[0069] After testing and analysis, the Na content of the phosphate cathode material precursor is 84.17 ppm and the specific surface area is 162.72m 2 / g; the Fe content is 13.88%, the Mn content is 53.87%, and the molar ratio Mn / Fe is calculated to be 0.798:0.202, the Fe yield is 99.75%, and the Mn yield is 98.38%.

[0070] 2. Preparation of lithium iron manganese phosphate / carbon composite material: (1) The raw materials of the phosphate cathode material precursor were added in a ratio of 1:1.08:1.03, based on the total molar amount of iron ions and manganese ions, the molar amount of lithium salt, and the molar amount of phosphate salt. 390.00 g of the phosphate cathode material precursor prepared above, 192.24 g of lithium carbonate, 573.88 g of ammonium dihydrogen phosphate, 2.50 g of niobium pentoxide, and 2.50 g of magnesium oxide were added to 1500 mL of pure water in sequence. The mixture was placed in a basket mill and ground at 2000 r / min for 50 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the finely ground slurry particle size reached D50 = 300 nm, it was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). The product was then calcined in a box furnace under a nitrogen atmosphere at 550°C for 4 h. After the box furnace was naturally cooled to 80°C, the calcined material was crushed to obtain 719.22 g of pre-lithiated lithium manganese iron phosphate precursor.

[0071] (2) 700.00 g of pre-lithiated lithium manganese iron phosphate precursor, 56.00 g of glucose, and 60.00 g of polyethylene glycol 20000 were added to 1500 mL of pure water in sequence, and placed in a basket grinder and ground at 2000 r / min for 40 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the slurry particle size after fine grinding reached D50 = 320 nm, the slurry was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). It was then placed in a box furnace under a nitrogen atmosphere for sintering at a sintering temperature of 700 ° C and kept at a constant temperature for 6 h. After the box furnace was naturally cooled to 80 ° C, the sintered material was graded and crushed to finally obtain LiFe with a carbon content of 1.62%. 0.2 Mn 0.8 PO4 / C composite material.

[0072] Prepared LiFe 0.2 Mn 0.8 The PO4 / C composite material was used as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder to form the electrode sheet. The battery was assembled into a button-type cell with metallic lithium as the negative electrode. Testing at various charge and discharge currents between 2 and 4.3 V and 25°C revealed an initial reversible capacity of 154.1 mAh / g at 0.1C, with a first efficiency of 97.5% at 0.1C. At 0.2C, the initial reversible capacity reached 151.9 mAh / g, with a plateau efficiency of 95.3% at 0.2C and 3.3 V. At 1C, the initial reversible capacity reached 145.0 mAh / g, with a capacity retention of 96.2% after 100 cycles at 1C.

[0073] Example 5 1. Preparation of phosphate cathode material precursor: (1) First, weigh 561.43 mL of ammonia water and mix it with 944.55 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 507.68 g of hydrated ferric sulfate and 507.08 g of monohydrated manganese sulfate, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.6:0.4). Then, weigh 620.26 g of potassium hydroxide and dissolve it in 1100.00 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 453.60 g of hydrogen peroxide solution and mix it with 907.20 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0074] (2) At 30°C, complexing agent A was added to the glass reactor as the base liquid, and then solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. Finally, the ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 1.5; then, precipitant C was added dropwise to the glass reactor at 42.86 mL / min through a peristaltic pump. The addition time was 28 min. During the addition, the stirring speed was 350 rpm / min. Finally, the ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2; finally, the temperature was raised to 40°C, and oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 40 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.8. The reaction was maintained at 40°C for 5 h, and the pH of the reaction system reached 10.49. After the reaction was complete, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 410.16 g of a phosphate cathode material precursor.

[0075] After testing and analysis, the S content of the phosphate cathode material precursor is 287.25 ppm, the K content is 105.73 ppm, and the specific surface area is 168.04 m 2 / g; the Fe content is 26.42%, the Mn content is 39.59%, and the molar ratio Mn / Fe is calculated to be 0.603:0.397, the Fe yield is 97.02%, and the Mn yield is 98.52%.

[0076] 2. Preparation of lithium iron manganese phosphate / carbon composite material: (1) The raw materials of the phosphate cathode material precursor were added in a ratio of 1:1.06:1.03, based on the total molar amount of iron ions and manganese ions, the molar amount of lithium salt, and the molar amount of phosphate salt. 400.00 g of the phosphate cathode material precursor prepared above, 187.94 g of lithium carbonate, 571.49 g of ammonium dihydrogen phosphate, 3.50 g of titanium dioxide, and 3.00 g of magnesium hydroxide were added to 1500 mL of pure water in sequence. The mixture was placed in a basket mill and ground at a speed of 2000 r / min for 50 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the finely ground slurry particle size reached D50 = 300 nm, it was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). The product was then calcined in a box furnace under a nitrogen atmosphere at 700°C for 3 h. After the box furnace was naturally cooled to 80°C, the calcined material was crushed to obtain 725.25 g of pre-lithiated lithium manganese iron phosphate precursor.

[0077] (2) 700.00 g of pre-lithiated lithium manganese iron phosphate precursor, 30.00 g of glucose, and 30.00 g of cyclodextrin were added to 1500 mL of pure water in sequence, and placed in a basket grinder and ground at 2000 r / min for 40 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the slurry particle size after fine grinding reached D50 = 320 nm, the slurry was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). It was then placed in a box furnace under a nitrogen atmosphere for sintering at a sintering temperature of 720 ° C and kept at a constant temperature for 4 h. After the box furnace was naturally cooled to 80 ° C, the sintered material was graded and crushed to finally obtain LiFe with a carbon content of 1.38%. 0.4 Mn 0.6 PO4 / C composite material.

[0078] Prepared LiFe 0.4 Mn 0.6 The PO4 / C composite material was used as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder to form the electrode sheet. The battery was assembled into a button-type cell with metallic lithium as the negative electrode. Testing at 2-4.3 V and 25°C using various charge and discharge current conditions revealed an initial reversible capacity of 156.3 mAh / g at 0.1C, with a first efficiency of 98.2% at 0.1C. At 0.2C, the initial reversible capacity was 153.9 mAh / g, with a plateau efficiency of 94.6% at 0.2C and 3.3 V. At 1C, the initial reversible capacity was 146.5 mAh / g, with a capacity retention of 97.2% after 100 cycles at 1C.

[0079] Example 6 1. Preparation of phosphate cathode material precursor: (1) First, weigh 374.29 mL of ammonia water and mix it with 577.88 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 546.05 g of ferric chloride hexahydrate and 599.70 g of manganese chloride tetrahydrate, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.6:0.4). Then, weigh 479.13 g of sodium hydroxide and dissolve it in 1150.00 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 340.20 g of hydrogen peroxide solution and mix it with 680.40 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0080] (2) At 30°C, complexing agent A was added to the glass reactor as the base liquid, and then solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. Finally, the ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 1; then, precipitant C was added dropwise to the glass reactor at 36.67 mL / min through a peristaltic pump. The addition time was 33 min. During the addition, the stirring speed was 350 rpm / min. Finally, the ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2.3; finally, the temperature was raised to 40°C, and oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.6. The reaction was maintained at 60°C for 3 h, and the pH of the reaction system reached 11.36. After completion of the reaction, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 411.73 g of a phosphate cathode material precursor.

[0081] After testing and analysis, the Na content of the phosphate cathode material precursor is 113.08 ppm and the specific surface area is 166.75 m 2 / g; the Fe content is 26.63%, the Mn content is 39.54%, and the molar ratio Mn / Fe is calculated to be 0.601:0.399, the Fe yield is 98.17%, and the Mn yield is 98.78%.

[0082] 2. Preparation of lithium iron manganese phosphate / carbon composite material: (1) The raw materials of the phosphate cathode material precursor were added in a ratio of 1:1.05:1.03, based on the total molar amount of iron ions and manganese ions, the molar amount of lithium salt, and the molar amount of phosphate salt. 400.00 g of the phosphate cathode material precursor prepared above, 186.61 g of lithium carbonate, 572.85 g of ammonium dihydrogen phosphate, 1.50 g of zirconium dioxide, and 3.50 g of magnesium oxide were added to 1500 mL of pure water in sequence. The mixture was placed in a basket mill and ground at a speed of 2000 r / min for 50 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the finely ground slurry particle size reached D50 = 300 nm, it was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). The product was then calcined in a box furnace under a nitrogen atmosphere at 650°C for 4 h. After the box furnace was naturally cooled to 80°C, the calcined material was crushed to obtain 730.88 g of pre-lithiated lithium manganese iron phosphate precursor.

[0083] (2) 700.00 g of pre-lithiated lithium manganese iron phosphate precursor, 60.00 g of glucose, and 30.00 g of polyethylene glycol 8000 were added to 1500 mL of pure water in sequence, and placed in a basket grinder and ground at 2000 r / min for 40 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the slurry particle size after fine grinding reached D50 = 320 nm, the slurry was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). It was then placed in a box furnace under a nitrogen atmosphere for sintering at a sintering temperature of 700 ° C and kept at a constant temperature for 6 h. After the box furnace was naturally cooled to 80 ° C, the sintered material was graded and crushed to finally obtain LiFe with a carbon content of 1.52%. 0.4 Mn 0.6 PO4 / C composite material.

[0084] Prepared LiFe 0.4 Mn 0.6 The PO4 / C composite material was used as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder to form the electrode sheet. The battery was assembled into a button-type cell with metallic lithium as the negative electrode. Under different charge and discharge current conditions tested at 2-4.3 V and 25°C, the initial reversible capacity at 0.1C was 156.1 mAh / g, with a first efficiency of 98.6% at 0.1C. At 0.2C, the initial reversible capacity was 154.2 mAh / g, with a plateau efficiency of 94.1% at 0.2C and 3.3 V. At 1C, the initial reversible capacity was 146.7 mAh / g, with a capacity retention of 96.5% after 100 cycles at 1C.

[0085] Comparative Example 1 Compared with Example 1, the only difference is that the ratio of the molar amount of hydroxide ions in the precipitant C to the total molar amount of iron ions and manganese ions in the solution B is 2.75.

[0086] 1. Preparation of phosphate cathode material precursor: (1) First, weigh 374.29 mL of ammonia water and mix it with 577.88 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 816.14 g of ferric nitrate nonahydrate and 1073.69 g of manganese nitrate solution, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.6:0.4). Then, weigh 572.88 g of sodium hydroxide and dissolve it in 1375.02 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 340.20 g of hydrogen peroxide solution and mix it with 680.40 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0087] (2) At 30°C, complexing agent A was added to the glass reactor as the base liquid, and then solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. Finally, the ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 1; then, precipitant C was added dropwise to the glass reactor at 36.67 mL / min through a peristaltic pump. The addition time was 39 min. During the addition, the stirring speed was 350 rpm / min. Finally, the ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2.75; finally, the temperature was raised to 40°C, and oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.6. The reaction was maintained at 40°C for 3 h, and the pH of the reaction system reached 13.72. After the reaction was complete, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 427.60 g of a phosphate cathode material precursor.

[0088] After testing and analysis, the Na content of the phosphate cathode material precursor is 3743.78 ppm and the specific surface area is 159.53 m 2 / g; the Fe content is 25.43%, the Mn content is 37.54%. After calculation, the molar ratio of Mn / Fe=0.600:0.400, the Fe yield is 97.36%, and the Mn yield is 97.40%.

[0089] 2. Preparation of lithium iron manganese phosphate / carbon composite material: (1) The raw materials of the phosphate cathode material precursor were added in a ratio of 1:1.05:1.03, based on the total molar amount of iron ions and manganese ions, the molar amount of lithium salt, and the molar amount of phosphate salt. 400.00 g of the phosphate cathode material precursor prepared above, 177.59 g of lithium carbonate, 545.14 g of ammonium dihydrogen phosphate, 3.50 g of titanium dioxide, and 1.50 g of magnesium oxide were added to 1500 mL of pure water in sequence. The mixture was placed in a basket mill and ground at 2000 r / min for 50 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the finely ground slurry particle size reached D50 = 300 nm, it was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). The product was then calcined in a box furnace under a nitrogen atmosphere at 600°C for 4 h. After the box furnace was naturally cooled to 80°C, the calcined material was crushed to obtain 710.11 g of pre-lithiated lithium manganese iron phosphate precursor.

[0090] (2) 700.00 g of pre-lithiated lithium manganese iron phosphate precursor, 56.00 g of glucose, and 50.00 g of polyethylene glycol 20000 were added to 1500 mL of pure water in sequence, and placed in a basket grinder and ground at 2000 r / min for 40 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the slurry particle size after fine grinding reached D50 = 300 nm, the slurry was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). It was then placed in a box furnace under a nitrogen atmosphere for sintering at a sintering temperature of 700 ° C and kept at a constant temperature for 6 h. After the box furnace was naturally cooled to 80 ° C, the sintered material was graded and crushed to finally obtain LiFe with a carbon content of 1.45%. 0.4 Mn 0.6 PO4 / C composite material.

[0091] Prepared LiFe 0.4 Mn 0.6The PO4 / C composite material was used as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder to form the electrode sheet. The battery was assembled into a button-type cell with metallic lithium as the negative electrode. Testing at 2-4.3 V and 25°C using various charge and discharge current conditions revealed an initial reversible capacity of 152.3 mAh / g at 0.1C, with a first efficiency of 95.8% at 0.1C. At 0.2C, the initial reversible capacity was 148.7 mAh / g, with a plateau efficiency of 93.2% at 0.2C and 3.3 V. At 1C, the initial reversible capacity was 139.8 mAh / g, with a capacity retention of 93.2% after 100 cycles at 1C.

[0092] Comparative Example 2 The same as Example 1, the only difference is that ferric nitrate nonahydrate is replaced by ferrous sulfate heptahydrate.

[0093] 1. Preparation of phosphate cathode material precursor: (1) First, weigh 374.29 mL of ammonia water and mix it with 577.88 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 561.64 g of ferrous sulfate heptahydrate and 1073.69 g of manganese nitrate solution, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.6:0.4). Then, weigh 437.47 g of sodium hydroxide and dissolve it in 1050.01 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 340.20 g of hydrogen peroxide solution and mix it with 680.40 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0094] (2) At 30°C, complexing agent A was added to the glass reactor as the base liquid, and then solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. Finally, the ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 1; then, precipitant C was added dropwise to the glass reactor at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. Finally, the ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2.1; finally, the temperature was raised to 40°C, and oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.6. The reaction was maintained at 40°C for 3 h, and the pH of the reaction system was 13.62. After the reaction was complete, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 428.80 g of a phosphate cathode material precursor.

[0095] After testing and analysis, the S content of the phosphate cathode material precursor is 308.46 ppm, the Na content is 3451.91 ppm, and the specific surface area is 96.72 m 2 / g; the Fe content is 25.49%, the Mn content is 37.68%, and after calculation, the molar ratio Mn / Fe=0.600:0.400, the Fe yield is 97.87%, and the Mn yield is 98.03%.

[0096] 2. Preparation of lithium iron manganese phosphate / carbon composite material: (1) The raw materials of the phosphate cathode material precursor were added in a ratio of 1:1.05:1.03, based on the total molar amount of iron ions and manganese ions, the molar amount of lithium salt, and the molar amount of phosphate salt. 400.00 g of the phosphate cathode material precursor prepared above, 177.58 g of lithium carbonate, 545.13 g of ammonium dihydrogen phosphate, 3.50 g of titanium dioxide, and 1.50 g of magnesium oxide were added to 1500 mL of pure water in sequence. The mixture was placed in a basket mill and ground at 2000 r / min for 50 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the finely ground slurry particle size reached D50 = 300 nm, it was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). The product was then calcined in a box furnace under a nitrogen atmosphere at 600°C for 4 h. After the box furnace was naturally cooled to 80°C, the calcined material was crushed to obtain 706.23 g of pre-lithiated lithium manganese iron phosphate precursor.

[0097] (2) 700.00 g of pre-lithiated lithium manganese iron phosphate precursor, 56.00 g of glucose, and 50.00 g of polyethylene glycol 20000 were added to 1500 mL of pure water in sequence, and placed in a basket grinder and ground at 2000 r / min for 40 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the slurry particle size after fine grinding reached D50 = 300 nm, the slurry was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). It was then placed in a box furnace under a nitrogen atmosphere for sintering at a sintering temperature of 700 ° C and kept constant for 6 h. After the box furnace was naturally cooled to 80 ° C, the sintered material was graded and crushed to finally obtain LiFe with a carbon content of 1.41%. 0.4 Mn 0.6 PO4 / C composite material.

[0098] Prepared LiFe 0.4 Mn 0.6 The PO4 / C composite material was used as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder to form the electrode sheet. The battery was assembled into a button-type cell with metallic lithium as the negative electrode. Testing at 2-4.3 V and 25°C using various charge and discharge current conditions revealed an initial reversible capacity of 152.0 mAh / g at 0.1C, with a first efficiency of 95.2% at 0.1C. At 0.2C, the initial reversible capacity reached 148.1 mAh / g, with a plateau efficiency of 91.8% at 0.2C and 3.3 V. At 1C, the initial reversible capacity reached 139.7 mAh / g, with a capacity retention of 90.3% after 100 cycles at 1C.

[0099] Comparative Example 3 The same as Example 1, except that the oxidant D is not added.

[0100] 1. Preparation of phosphate cathode material precursor: (1) First, weigh 374.29 mL of ammonia water and mix it in 577.88 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 816.14 g of ferric nitrate nonahydrate and 1073.69 g of manganese nitrate solution, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.6:0.4). Then, weigh 437.47 g of sodium hydroxide and dissolve it in 1050.01 mL of pure water to prepare a 10 mol / L precipitant C.

[0101] (2) At 30°C, complexing agent A was added to the glass reactor as the base solution, and solution B was then added dropwise to the glass reactor at a rate of 93.33 mL / min via a peristaltic pump for 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. The final ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 1. The precipitant C was then added dropwise to the glass reactor at a rate of 36.67 mL / min via a peristaltic pump for 30 min. During the addition, the stirring speed was 350 rpm / min. The final ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2.1. The reaction was kept at 40°C for 3 h, and the pH of the reaction system was 10.57. After the reaction is completed, the product is filtered, washed and filtered until the conductivity of the filtrate is less than 300 μS / cm; the filter cake is placed in an 80°C forced air drying oven and dried for 12 h, finally obtaining 414.80 g of phosphate cathode material precursor.

[0102] After testing and analysis, the Na content of the phosphate cathode material precursor is 1971.42 ppm and the specific surface area is 123.62 m 2 / g; the Fe content is 26.41%, the Mn content is 37.61%. After calculation, the molar ratio Mn / Fe=0.591:0.409, the Fe yield is 98.07%, the Mn yield is 94.66%, and the manganese content yield is low.

[0103] 2. Preparation of lithium iron manganese phosphate / carbon composite material: (1) The raw materials of the phosphate cathode material precursor were added in a ratio of 1:1.05:1.03, based on the total molar amount of iron ions and manganese ions, the molar amount of lithium salt, and the molar amount of phosphate salt. 400.00 g of the phosphate cathode material precursor prepared above, 180.52 g of lithium carbonate, 545.15 g of ammonium dihydrogen phosphate, 3.50 g of titanium dioxide, and 1.50 g of magnesium oxide were added to 1500 mL of pure water in sequence. The mixture was placed in a basket mill and ground at 2000 r / min for 50 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the finely ground slurry particle size reached D50 = 300 nm, it was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). The product was then calcined in a box furnace under a nitrogen atmosphere at 600°C for 4 h. After the box furnace was naturally cooled to 80°C, the calcined material was crushed to obtain 712.53 g of pre-lithiated lithium manganese iron phosphate precursor.

[0104] (2) 700.00 g of pre-lithiated lithium manganese iron phosphate precursor, 56.00 g of glucose, and 50.00 g of polyethylene glycol 20000 were added to 1500 mL of pure water in sequence, and placed in a basket grinder and ground at 2000 r / min for 40 min. After the slurry particle size reached D50 = 1-2 μm, the slurry was introduced into a sand mill for fine grinding. After the slurry particle size after fine grinding reached D50 = 300 nm, the slurry was spray dried (inlet temperature was 260 ° C, outlet temperature was 100 ° C). It was then placed in a box furnace under a nitrogen atmosphere for sintering at a sintering temperature of 700 ° C and kept at a constant temperature for 6 h. After the box furnace was naturally cooled to 80 ° C, the sintered material was graded and crushed to finally obtain LiFe with a carbon content of 1.43%. 0.41 Mn 0.59 PO4 / C composite material.

[0105] Prepared LiFe 0.41 Mn 0.59 The PO4 / C composite material was used as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder to form the electrode sheet. The battery was assembled into a button-type cell with metallic lithium as the negative electrode. Testing at 2-4.3 V and 25°C using various charge and discharge current conditions revealed an initial reversible capacity of 150.1 mAh / g at 0.1C, with a first efficiency of 95.5% at 0.1C. At 0.2C, the initial reversible capacity was 148.3 mAh / g, with a plateau efficiency of 91.8% at 0.2C and 3.3 V. At 1C, the initial reversible capacity was 136.6 mAh / g, with a capacity retention of 91.3% after 100 cycles at 1C.

[0106] Comparative Example 4 The same as Example 1, except that the ratio of the molar amount of hydroxide ions in the precipitant C to the total molar amount of iron ions and manganese ions in the solution B is 1.5.

[0107] 1. Preparation of phosphate cathode material precursor: (1) First, weigh 374.29 mL of ammonia water and mix it with 577.88 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 816.14 g of ferric nitrate nonahydrate and 1073.69 g of manganese nitrate solution, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.6:0.4). Then, weigh 312.48 g of sodium hydroxide and dissolve it in 750.01 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 340.20 g of hydrogen peroxide solution and mix it with 680.40 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0108] (2) At 30°C, the complexing agent A was added to the glass reactor as the base liquid, and then the solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, the stirring was continued for 10 min. Finally, the ratio of the molar amount of complexing ions in the complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 1; then the precipitant C was added dropwise to the glass reactor at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. Finally, the ratio of the molar amount of hydroxide ions in the precipitant C to the total molar amount of iron ions and manganese ions in solution B was 1.5; finally, the temperature was raised to 40°C, and the oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.6. The reaction was maintained at 40°C for 3 h, with a pH of 8.30. After completion of the reaction, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 382.92 g of a phosphate cathode material precursor.

[0109] After testing and analysis, the Na content of the phosphate cathode material precursor is 65.86 ppm and the specific surface area is 192.48m 2 / g; the Fe content is 23.68%, the Mn content is 30.67%. After calculation, the molar ratio Mn / Fe=0.568:0.432, the Fe yield is 81.18%, and the Mn yield is 71.26%. The low usage of sodium hydroxide makes the yield of iron and manganese elements low, and the ratio of iron to manganese elements deviates too much from the theoretical value (4:6).

[0110] Comparative Example 5 The same as Example 1, the only difference is that the ratio of the molar amount of complexing ions in the complexing agent A to the total molar amount of iron ions and manganese ions in the solution B is 2.5.

[0111] 1. Preparation of phosphate cathode material precursor: (1) First, weigh 935.71 mL of ammonia water and mix it with 1827.88 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 816.14 g of ferric nitrate nonahydrate and 1073.69 g of manganese nitrate solution, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.6:0.4). Then, weigh 437.47 g of sodium hydroxide and dissolve it in 1050.01 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 340.20 g of hydrogen peroxide solution and mix it with 680.40 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0112] (2) At 30°C, complexing agent A was added to the glass reactor as the base liquid, and then solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. Finally, the ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 2.5; then, precipitant C was added dropwise to the glass reactor at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. Finally, the ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2.1; finally, the temperature was raised to 40°C, and oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.6. The reaction was maintained at 40°C for 3 h, with a pH of 10.30. After completion of the reaction, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 399.24 g of a phosphate cathode material precursor.

[0113] After testing and analysis, the Na content of the phosphate cathode material precursor is 97.23 ppm and the specific surface area is 177.76m 2 / g; the Fe content was 25.57%, and the Mn content was 29.17%. The calculated molar ratio of Mn / Fe was 0.537:0.463, resulting in an Fe yield of 91.40% and a Mn yield of 70.66%. The high amount of ammonia used resulted in low iron and manganese yields, and the iron:manganese ratio deviated significantly from the theoretical value (4:6).

[0114] Comparative Example 6 The same as Example 1, except that the ratio of the molar amount of complexing ions in the complexing agent A to the total molar amount of iron ions and manganese ions in the solution B is 0.35.

[0115] 1. Preparation of phosphate cathode material precursor: (1) First, weigh 131.00 mL of ammonia water and mix it with 36.22 mL of pure water to prepare a 6 mol / L complexing agent A. Then, weigh 816.14 g of ferric nitrate nonahydrate and 1073.69 g of manganese nitrate solution, add 1666.7 mL of pure water, and prepare a 3 mol / L solution B (the molar ratio of manganese to iron is 0.6:0.4). Then, weigh 437.47 g of sodium hydroxide and dissolve it in 1050.01 mL of pure water to prepare a 10 mol / L precipitant C. Finally, weigh 340.20 g of hydrogen peroxide solution and mix it with 680.40 mL of pure water to prepare a 4.41 mol / L oxidant D.

[0116] (2) At 30°C, complexing agent A was added to the glass reactor as the base liquid, and then solution B was added dropwise to the glass reactor at 93.33 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. After the addition was completed, stirring was continued for 10 min. The final ratio of the molar amount of complexing ions in complexing agent A to the total molar amount of iron ions and manganese ions in solution B was 0.35; then precipitant C was added dropwise to the glass reactor at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 350 rpm / min. The final ratio of the molar amount of hydroxide ions in precipitant C to the total molar amount of iron ions and manganese ions in solution B was 2.1; finally, the temperature was raised to 40°C, and oxidant D was added dropwise to the reaction solution at 36.67 mL / min through a peristaltic pump. The addition time was 30 min. During the addition, the stirring speed was 400 rpm / min. After the addition was complete, the final molar ratio of oxidant D to the total molar amount of iron and manganese ions in solution B was 0.6. The reaction was maintained at 40°C for 3 h, with a pH of 9.35. After completion of the reaction, the product was filtered, washed, and vacuum-filtered until the filtrate conductivity was <300 μS / cm. The filter cake was dried in a forced-air drying oven at 80°C for 12 h, yielding 401.76 g of a phosphate cathode material precursor.

[0117] After testing and analysis, the Na content of the phosphate cathode material precursor is 53.76 ppm and the specific surface area is 401.76m 2 / g; the Fe content was 24.54%, and the Mn content was 32.02%. The calculated molar ratio of Mn / Fe was 0.570:0.430, resulting in an Fe yield of 88.27% and a Mn yield of 78.05%. The low amount of ammonia used resulted in low iron and manganese yields, and the iron:manganese ratio deviated significantly from the theoretical value (4:6).

[0118] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a phosphate cathode material precursor, characterized in that: The steps include: (1) Mix ammonia water with water to obtain complexing agent A; then dissolve iron metal salt and manganese metal salt in water to obtain solution B; then dissolve hydroxide in water to obtain precipitant C; finally, mix oxide with water to obtain oxidant D; (2) Add solution B, precipitant C and oxidant D to complexing agent A in sequence and react to obtain: In step (1), the iron salt is selected from one or more of ferric sulfate, ferric nitrate and ferric chloride; and the hydroxide is selected from one or more of sodium hydroxide, potassium hydroxide and ammonia water.

2. The preparation method according to claim 1, characterized in that In step (1), the concentration of the complexing agent A is 3-10 mol / L; the manganese salt is selected from one or more of manganese sulfate, manganese nitrate, manganese chloride and manganese citrate; the total metal concentration of the solution B is 1-3 mol / L; and the molar ratio of manganese element to iron element in the solution B is 0.5-0.9:0.1-0.

5.

3. The preparation method according to claim 1, characterized in that In step (1), the concentration of the precipitant C is 6-12 mol / L; the oxide is selected from one or more of sodium peroxide, hydrogen peroxide and ozone; and the concentration of the oxidant D is 3-9.8 mol / L.

4. The preparation method according to any one of claims 1 to 3, characterized in that During the reaction in step (2), the ratio of the molar amount of complexing ions in the complexing agent A to the total molar amount of iron ions and manganese ions in the solution B is 0.5-2:1; the ratio of the molar amount of hydroxide ions in the precipitant C to the total molar amount of iron ions and manganese ions in the solution B is 1.8-2.6:1; and the ratio of the molar amount of the oxidant D to the total molar amount of iron ions and manganese ions in the solution B is 0.6-1.0:

1.

5. The preparation method according to claim 4, characterized in that In step (2), the time for sequentially adding solution B, precipitant C and oxidant D is 10-120 min, and the temperature for sequentially adding solution B, precipitant C and oxidant D is 30-80°C; the addition is carried out at a rotation speed of 250-600 rpm; the reaction conditions are: pH = 10-12, reaction at 30-80°C for 3-6 h; after the reaction is completed, the mixture is filtered, washed with water until the conductivity is ≤300 μS / cm, and finally dried at 60-90°C for 12-24 h.

6. A phosphate cathode material precursor prepared by the preparation method according to any one of claims 1 to 5.

7. Use of the phosphate cathode material precursor according to claim 6 in the preparation of lithium iron manganese phosphate / carbon composite material.

8. The use according to claim 7, characterized in that The method for preparing the lithium iron manganese phosphate / carbon composite material comprises the following steps: mixing a phosphate positive electrode material precursor, a lithium salt, a phosphorus salt and an additive in a liquid phase system, and calcining to obtain a lithium iron manganese phosphate precursor; and then mixing the lithium iron manganese phosphate precursor with a carbon source in a liquid phase system, and sintering to obtain the composite material.

9. The use according to claim 8, characterized in that The lithium salt is selected from one or more of lithium carbonate, lithium hydroxide, lithium phosphate and lithium dihydrogen phosphate; the phosphorus source is selected from one or more of ammonium dihydrogen phosphate, ammonium monohydrogen phosphate, ammonium phosphate, lithium dihydrogen phosphate and lithium phosphate; the additive is selected from one or more of titanium dioxide, tetrabutyl titanate, magnesium hydroxide, magnesium oxide, magnesium acetate, magnesium nitrate, zirconium dioxide, zirconium hydroxide, niobium pentoxide, nickel acetate and nickel oxide; the ratio of the total molar amount of iron ions and manganese ions, the molar amount of lithium salt and the molar amount of phosphorus salt in the phosphate positive electrode material precursor is 1:1-1.1:1-1.1; the mass of the additive accounts for 0-5% of the mass of the phosphate positive electrode material precursor; the carbon source is selected from one or more of glucose, crystal sugar, sucrose, fructose, polyethylene glycol, cyclodextrin, starch and cellulose.

10. The use according to claim 8, characterized in that The liquid phase system is selected from water, ethanol or methanol; after the mixing is completed, grinding and drying are performed; the calcination temperature is 400-700°C, the calcination time is 2-6 hours, and the calcination atmosphere is nitrogen, argon or helium; the sintering temperature is 675-780°C, the sintering time is 4-10 hours, and the sintering atmosphere is nitrogen, argon or helium; the carbon content in the lithium iron manganese phosphate / carbon composite material is 1.2-2%.

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