Manganese phosphate precursor as well as composite material, preparation method and application thereof

Abstract

The invention provides a manganese phosphate precursor as well as a composite material, a preparation method and application thereof, and relates to the technical field of lithium ion battery materials. The preparation method of the manganese phosphate precursor comprises the following steps: mixing and stirring a carbonate solution and a manganese source solution at the reaction temperature of 50-80 DEG C, filtering, washing and pulping to obtain manganese carbonate slurry; mixing and stirring the phosphoric acid solution and the manganese carbonate slurry at the temperature of 50-80 DEG C; and heating for reaction, filtering, washing and drying to obtain the manganwentzelite type manganese phosphate precursor, the yield and content of Mn and P are high, and the impurity content is low. The manganwentzelite type manganese phosphate salt precursor is used for preparing a lithium ferric manganese phosphate / carbon composite material or a battery positive electrode material, and the electrical property is excellent.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery materials, and particularly relates to a manganese phosphate precursor and a composite material thereof, a preparation method and applications. Background Art

[0002] Lithium-ion batteries, with their advantages of long cycle life and high energy density, are widely used in portable electronics and electric vehicles. The cathode material directly impacts the energy density, rate capability, and safety of lithium-ion batteries. In recent years, with the development of new energy vehicles, lithium iron phosphate (LiFePO4) with its 3.4V voltage platform has been unable to meet market demand for batteries with higher energy density and power density. Lithium iron manganese phosphate (LiMnPO4) combines the high safety of LiFePO4 with the high platform voltage advantage of LiMnPO4, thus attracting widespread attention.

[0003] Manganese phosphate is one of the key raw materials of manganese phosphate materials. 3+ In aqueous solution, it is easy to undergo disproportionation reaction to generate Mn 2+ Because manganese phosphate contains a large amount of manganese and MnO2, it is difficult to prepare pure manganese phosphate. This typically requires the use of a nitric acid-ethanol system or the addition of a strong oxidant to oxidize it to trivalent manganese under high temperature and pressure. This method is inefficient, energy-intensive, and polluting, making it difficult to commercialize. Chinese invention patent CN112142028A provides a method for preparing manganese phosphate: concentrated phosphoric acid and potassium permanganate are mixed in a set ratio; the mixture is reacted at a set temperature; after the reaction is complete, the reaction solution is filtered, washed, and dried to obtain manganese phosphate. This method uses potassium permanganate, which introduces potassium impurities, and the reaction temperature is 150°C-180°C, which is high in temperature and energy consumption.

[0004] Chinese invention patent CN116062724A provides a method for preparing a manganous phosphate material, comprising the following steps: dissolving a soluble phosphorus source and a manganese source in deionized water to prepare a solution; adding the phosphorus source solution and continuing to stir; adding an alkaline solution and continuing to stir to adjust the pH of the reaction system to 6.5-10; heating the resulting slurry in a reactor to 40-90°C; cooling, filtering, and washing to obtain a filter cake; and drying the filter cake to obtain the manganous phosphate material. This method requires the use of a large amount of strong alkaline solution for pH adjustment, which is complex and can lead to product decomposition or exacerbated side reactions.

[0005] Zheng Dianmo et al. (A new process for the preparation of manganese phosphate and its electrochemical performance [J]. Materials Review, 2014, 28(8):83-6) used manganese sulfate as a manganese source and phosphoric acid as a precipitant. An appropriate amount of surfactant was added to a reactor containing distilled water, which was then placed in a constant temperature water bath while being stirred and heated. Then, phosphoric acid solution and manganese sulfate solution were quickly and evenly added dropwise according to a certain ratio of phosphorus to manganese substances to react, and the pH value was adjusted to an appropriate value. Ethanol was then added to obtain a suspension. The heating was stopped, the mixture was cooled to room temperature, and the filter cake after suction filtration, water washing, and alcohol washing was dried to obtain the final product. This method has the problems of difficulty in controlling the reaction conditions, instability during the precipitation process, and difficulty in accurate replication in large-scale production.

[0006] In view of the problems of the existing methods such as complicated steps, high reaction temperature, and even the need for additional pH control, it is necessary to develop a method for preparing manganese phosphate precursors that is simple, environmentally friendly, and suitable for large-scale production, and use the manganese phosphate precursors in the preparation of lithium iron manganese phosphate / carbon composite materials to improve the electrochemical performance of the positive electrode material. Summary of the Invention

[0007] In response to the problems existing in the prior art, the present invention provides a manganese phosphate precursor and its composite material, preparation method and application. The present invention first reacts a carbonate solution with a manganese source solution at a temperature of 50-80°C to obtain a manganese carbonate slurry; then the manganese carbonate slurry is beaten with water, and finally a phosphoric acid solution is added to the beaten manganese carbonate slurry to react at a certain temperature, and then filtered, washed and dried to obtain a red phosphorus manganese ore type manganese phosphate. In the preparation method of the present invention, the entire reaction process is simple to operate, environmentally friendly, avoids the use of organic solvents and oxidants, and does not require the regulation of the reaction pH. It can be carried out at normal pressure and is easy to industrialize. By mixing, grinding and sintering the manganese phosphate precursor, iron phosphate, lithium carbonate, etc., a lithium iron manganese phosphate or lithium manganese phosphate positive electrode material with excellent electrical properties can be prepared.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a manganese phosphate precursor, comprising the steps of: (1) mixing a carbonate solution and a manganese source solution at a reaction temperature of 50-80° C. to obtain a manganese carbonate slurry A; (2) filtering, washing, and beating the manganese carbonate slurry A to obtain manganese carbonate slurry B; (3) mixing and stirring the phosphoric acid solution and the manganese carbonate slurry B under the reaction temperature conditions of step (1); (4) Heating the reaction, filtering, washing, and drying to obtain a red phosphorus manganese ore type manganese phosphate salt precursor.

[0009] Preferably, in step (1), the carbonate is selected from one or more of ammonium carbonate, ammonium bicarbonate, and sodium carbonate.

[0010] Further preferably, in step (1), the carbonate is selected from at least one of ammonium carbonate and sodium carbonate.

[0011] Preferably, in step (1), the concentration of the carbonate solution is 0.5-6.0 mol / L.

[0012] Further preferably, in step (1), the concentration of the carbonate solution is 1.0-4.0 mol / L.

[0013] More preferably, in step (1), the concentration of the carbonate solution is 1.5 mol / L.

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

[0015] Further preferably, in step (1), the manganese source is manganous sulfate.

[0016] Preferably, in step (1), the concentration of the manganese source solution is 0.5-6.0 mol / L.

[0017] Further preferably, in step (1), the concentration of the manganese source solution is 1.0-4.0 mol / L.

[0018] Further preferably, in step (1), the concentration of the manganese source solution is 1.25 mol / L.

[0019] Preferably, in step (1), the molar ratio of the carbonate to the manganese source is 0.5-1.5:1.0.

[0020] Further preferably, in step (1), the molar ratio of the carbonate to the manganese source is 1.0-1.3:1.0.

[0021] More preferably, in step (1), the molar ratio of the carbonate to the manganese source is 1.2:1.0.

[0022] Preferably, in step (1), the reaction temperature is 50-80°C, and the reaction time is 2-6 hours.

[0023] Further preferably, in step (1), the reaction temperature is 60° C. and the reaction time is 3-5 h.

[0024] More preferably, in step (1), the reaction temperature is 60° C. and the reaction time is 4 h.

[0025] Preferably, in step (1), the carbonate solution is added at a rate of 5-80 mL / min.

[0026] Further preferably, in step (1), the carbonate solution is added at a rate of 10-50 mL / min.

[0027] Further preferably, in step (1), the carbonate solution is added at a rate of 10-40 mL / min.

[0028] Preferably, in step (1), the stirring speed is 300-400 rpm.

[0029] Further preferably, in step (1), the stirring speed is 350 rpm.

[0030] Preferably, in step (2), the washing is performed until the conductivity of the filtrate is less than 300 μS / cm.

[0031] Preferably, in step (2), the solid content of the manganese carbonate slurry B is 10-50%.

[0032] Further preferably, in step (2), the solid content of the manganese carbonate slurry B is 20%.

[0033] Preferably, in step (3), the mass concentration of the phosphoric acid solution is 20-40%.

[0034] Further preferably, in step (3), the mass concentration of the phosphoric acid solution is 30%.

[0035] Preferably, in step (3), during the mixing and stirring, the molar ratio of phosphoric acid to manganese source is 0.5-1.3:1.0.

[0036] Further preferably, in step (3), during the mixing and stirring, the molar ratio of phosphoric acid to manganese source is 0.7-1.2:1.0.

[0037] Further preferably, in step (3), during the mixing and stirring, the molar ratio of phosphoric acid to manganese source is 0.8:1.0.

[0038] Preferably, in step (3), the stirring speed is 300-400 rpm.

[0039] Further preferably, in step (3), the stirring speed is 350 rpm.

[0040] Preferably, in step (4), the reaction temperature is 80-100°C.

[0041] Further preferably, in step (4), the reaction temperature is 80-95°C.

[0042] Further preferably, in step (4), the reaction temperature is 85-95°C.

[0043] Preferably, in step (4), the reaction time is 2-6 hours.

[0044] Further preferably, in step (4), the reaction time is 3-6 hours.

[0045] Further preferably, in step (4), the reaction time is 4-6 hours.

[0046] In a second aspect, the present invention provides a manganese phosphate precursor prepared by the above preparation method.

[0047] In a third aspect, the present invention provides a lithium manganese iron phosphate / carbon composite material prepared from the above-mentioned manganese phosphate precursor.

[0048] In a fourth aspect, the present invention further provides a method for preparing a lithium manganese iron phosphate / carbon composite material, comprising the steps of: S1. Mixing a lithium source, anhydrous iron phosphate, the above-mentioned manganese phosphate precursor, a phosphorus source, a carbon source, and an additive in a liquid phase system to obtain a mixture, grinding, and drying to obtain a lithium iron manganese phosphate / carbon composite material precursor; S2. The lithium manganese iron phosphate / carbon composite material precursor is sintered under an inert gas protection atmosphere to finally obtain the lithium manganese iron phosphate / carbon composite material.

[0049] Preferably, in step S1, the lithium source is selected from one or more of lithium carbonate, lithium hydroxide, and lithium acetate.

[0050] Further preferably, in step S1, the lithium source is lithium carbonate.

[0051] Preferably, in step S1, the phosphorus source is selected from one or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, phosphoric acid Further preferably, in step S1, the phosphorus source is ammonium dihydrogen phosphate.

[0052] Preferably, in step S1, the carbon source is selected from one or more of glucose, crystal sugar, sucrose, fructose, polyethylene glycol, cyclodextrin, starch, and cellulose.

[0053] Further preferably, in step S1, the carbon source is selected from at least one of glucose and polyethylene glycol 20000.

[0054] Preferably, in step S1, the additive is selected from one or more of titanium dioxide, tetrabutyl titanate, magnesium acetate, magnesium oxide, magnesium hydroxide, magnesium nitrate, zirconium nitrate, zirconium dioxide, zirconium hydroxide, niobium pentoxide, nickel acetate, nickel nitrate, and nickel hydroxide.

[0055] Further preferably, in step S1, the additive is selected from one or more of magnesium oxide, magnesium hydroxide, titanium dioxide, and niobium pentoxide.

[0056] Preferably, in step S1, the amount of the additive is 0-1.0% of the final mass of lithium manganese iron phosphate.

[0057] Preferably, in step S1, the medium of the liquid phase system is selected from one or more of water, methanol and ethanol.

[0058] Further preferably, in step S1, the medium of the liquid phase system is ethanol and / or water.

[0059] Preferably, in step S1, the molar ratio of Fe / P in the anhydrous ferric phosphate is 0.940-0.990:1.

[0060] Further preferably, in step S1, the molar ratio of Fe / P in the anhydrous ferric phosphate is 0.940-0.980:1.

[0061] More preferably, in step S1, the molar ratio of Fe / P in the anhydrous ferric phosphate is 0.975:1.

[0062] Preferably, in step S1, the lithium source is fed in an amount such that the molar ratio of Li / (Fe+Mn) is 1-1.1:1.

[0063] Further preferably, in step S1, the lithium source is fed in an amount such that the molar ratio of Li / (Fe+Mn) is 1.05-1.06:1.

[0064] Preferably, in step S1, the phosphorus source is fed in an amount such that the (Fe+Mn)n / P molar ratio is 0.96-0.99:1.

[0065] Further preferably, in step S1, the phosphorus source is added at a (Fe+Mn) / P molar ratio of 0.975:1.

[0066] Preferably, in step S1, the manganese phosphate precursor is fed in an amount according to a molar ratio of 0.5≤nMn / n(Fe+Mn)≤1.

[0067] Preferably, in step S1, the grinding is specifically as follows: firstly, coarse grinding is performed using a basket grinder, the grinding time is 30min-60min, and the grinding particle size is controlled within D 50 =1-2μm; then use a fine sand mill for fine grinding, the fine grinding time is 60-180min, and the fine grinding slurry particle size is controlled at 200-500nm.

[0068] Further preferably, in step S1, the particle size of the finely ground slurry is controlled to be 350-400 nm.

[0069] Preferably, in step S1, the drying method is static drying or spray drying.

[0070] Preferably, in step S2, the sintering is specifically: the sintering temperature is 650-750° C., and the sintering time is 6-12 hours.

[0071] Further preferably, in step S2, the sintering is specifically: the sintering temperature is 700-750° C., and the sintering time is 10-11 hours.

[0072] Preferably, in step S2, the inert gas is selected from one or more of argon, helium, nitrogen and carbon dioxide.

[0073] Preferably, in step S2, the carbon content in the lithium iron manganese phosphate / carbon composite material is 1.2-2.5 wt.%.

[0074] Finally, the present invention provides the use of the above-mentioned manganese phosphate precursor or lithium manganese iron phosphate / carbon composite material in the preparation of battery positive electrode materials.

[0075] Preferably, the application is application in preparing positive electrode materials for lithium-ion batteries.

[0076] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses precipitation conversion to first react a carbonate solution with a manganese source solution to obtain a manganese carbonate slurry, and then add a phosphoric acid solution to the washed manganese carbonate slurry to react to obtain a red phosphorus manganese ore-type manganese phosphate precursor. The manganese phosphate precursor obtained by this preparation method has a high yield of manganese and phosphorus elements (the yield of manganese and phosphorus elements is as high as more than 96%), is simple in process, is environmentally friendly, and is suitable for industrial production.

[0077] (2) The present invention removes soluble impurities in the filter cake by washing the manganese carbonate slurry, thereby reducing the influence of impurity ions on the subsequent nucleation process of erythrodiolite-type manganese phosphate, and finally obtains an erythrodiolite-type manganese phosphate precursor with high purity and good crystallinity.

[0078] (3) The present invention utilizes the characteristics of MnCO3 such as small Ksp value and easy precipitation, and first prepares spherical manganese carbonate with uniform particle size through precipitation conversion. Relying on the special morphology of manganese carbonate, phosphoric acid is added again, and dissolved and crystallized at a certain reaction temperature to prepare red phosphorus manganese phosphate salt of low specific surface area and easy to wash.

[0079] (4) The method of the present invention avoids the use of organic solvents and oxidants in the preparation process, and does not require the use of solutions such as ammonia water to control the reaction pH. It can be carried out under normal pressure, is simple to operate, and has low cost.

[0080] (5) The manganese phosphate precursor prepared by the specific preparation method of the present invention is mixed with iron phosphate, lithium carbonate, etc., ground, and sintered to prepare lithium manganese iron phosphate or lithium manganese phosphate positive electrode materials with excellent electrical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0081] Figure 1 This is a 50,000-fold magnified SEM image of the manganese carbonate prepared in Example 1.

[0082] Figure 2 is the XRD pattern of the manganese carbonate prepared in Example 1.

[0083] Figure 3 This is a 10,000-fold SEM image of the pyrophosphate-type manganese salt precursor prepared in Example 1.

[0084] Figure 4 This is the XRD pattern of the red phosphorus manganese phosphate precursor prepared in Example 1.

[0085] Figure 5 This is the XRD pattern of the lithium manganese iron phosphate / carbon composite material prepared in Example 1.

[0086] Figure 6 1 is a discharge curve of the lithium manganese iron phosphate button battery prepared in Example 1. DETAILED DESCRIPTION

[0087] The following non-limiting examples are provided to enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way. The following are merely illustrative of the scope of the present invention, and those skilled in the art may make various changes and modifications to the present invention based on the disclosed content, which should also fall within the scope of the present invention.

[0088] When numerical ranges are given in the examples, it should be understood that, unless otherwise specified herein, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the invention belongs.

[0089] The present invention is described below by way of specific examples to facilitate understanding and grasp of the technical solutions of the present invention, but the present invention is not limited thereto. The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified; and different sources do not significantly affect product performance.

[0090] Example 1 A manganese phosphate precursor, the preparation method of which comprises the steps of: (1) Dissolve 170.73 g of manganese sulfate monohydrate (99% purity) in 800 mL of deionized water to obtain a manganese source solution; Dissolve 116.47 g of ammonium carbonate (99% purity) in 800 mL of deionized water to obtain a carbonate solution; At 60°C, the carbonate solution was added dropwise to the manganese source solution at a rate of 40 mL / min. During the entire addition process, the stirring speed was 350 rpm. When the addition was completed and the solution temperature reached 60°C, the timing was started and the reaction was continued for 4 hours, with the stirring speed maintained at 350 rpm. (2) 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 obtained filter cake is redispersed in 250 mL of pure water and beaten to obtain a manganese carbonate slurry; (3) Prepare 261.33 g of 30 wt.% phosphoric acid solution and add the solution dropwise to the manganese carbonate slurry at 60°C at a rate of 6.5 mL / min. Stir at 350 rpm throughout the addition process. (4) After the addition is completed, the temperature is raised. When the solution temperature reaches 95°C, the timer is started. The reaction is carried out at 95°C for 4 hours, and the stirring speed is maintained at 350 rpm. 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 obtained manganese phosphate precursor filter cake is placed in an 80°C forced air drying oven for 12 hours to finally obtain 142.16 g of pink red phosphorus manganese ore type manganese phosphate precursor.

[0091] After analysis, the specific surface area of ​​the red phosphorus manganese ore type manganese phosphate precursor is 0.34m 2 / g, of which the Mn content is 37.96% and the P content is 17.10%. After calculation, the molar ratio Mn / P is 1.252, the Mn yield is 98.217%, and the P yield is 98.094%.

[0092] The manganese carbonate slurry of step (2) is dried to obtain an intermediate product, manganese carbonate. The intermediate product, manganese carbonate, is observed by scanning electron microscopy. The results are as follows: Figure 1The intermediate product manganese carbonate was characterized by XRD and phase analysis, and the characterization results were as follows: Figure 2 The red phosphorus manganese phosphate precursor was observed by scanning electron microscopy, and the results are shown in Figure 3 At the same time, the obtained red phosphorus manganese ore type manganese phosphate precursor was characterized by XRD and phase analysis, and the characterization results were as follows Figure 4 shown.

[0093] from Figure 1 It can be seen that the intermediate product manganese carbonate secondary particles are uniform spherical particles with a particle size between 1-2 μm.

[0094] from Figure 2 It can be seen that the XRD pattern of the intermediate product manganese carbonate is consistent with the standard XRD pattern (PDF#44-1472 MnCO3) and has no extra peaks, indicating that the intermediate product is manganese carbonate.

[0095] from Figure 3 It can be seen that the prepared pyrophosphate-type manganese phosphate precursor is a block of prismatic secondary particles accumulated from flaky primary particles, and the thickness of the flaky layer is less than 1 μm.

[0096] from Figure 4 It can be seen that the XRD pattern of the prepared red phosphate manganese ore type manganese phosphate salt precursor is consistent with the standard XRD pattern (PDF#86-1521 Mn5(PO3(OH))2(PO4)2(H2O)4), and there are no extra impurity peaks, indicating that the prepared red phosphate manganese ore type manganese phosphate salt precursor is Mn5(PO3(OH))2(PO4)2(H2O)4.

[0097] The manganese phosphate precursor is used to prepare a lithium manganese iron phosphate / carbon composite material. The preparation method of the lithium manganese iron phosphate / carbon composite material includes the following steps: S1. The red phosphorus manganese phosphate precursor was placed in a muffle furnace at 550° C. for heating and dehydration for 4 hours to obtain a dehydrated manganese phosphate precursor (Mn content of 44.04% and P content of 19.57%).

[0098] The raw materials were fed at a molar ratio of Li / (Fe+Mn)=1.06:1, (Fe+Mn) / P=0.975:1; 100 g of dehydrated manganese phosphate precursor, 82.56 g of anhydrous ferric phosphate (molar ratio Fe / P=0.975:1), 22.04 g of ammonium dihydrogen phosphate (99.4 wt.%), 52.59 g of lithium carbonate (99.5 wt.%), 16.37 g of glucose, 6.14 g of polyethylene glycol 20000, 0.82 g of magnesium oxide, and 0.82 g of titanium dioxide were added to 1600 mL of anhydrous ethanol, and the mixture was placed in a basket mill and ground at a speed of 1500 r / min for 60 min. After grinding, the slurry was introduced into a sand mill for grinding. After the slurry particle size reached 400 nm, the slurry was spray-dried; S2. After drying, the dried and crushed material was placed in a tube furnace under a nitrogen atmosphere for sintering at a temperature of 700°C for 10 hours. After the tube furnace was naturally cooled to 80°C, the sintered material was graded and crushed to obtain a powder with a carbon content of 1.68% and a compacted density of 2.34 g / cm 3 LiFe 0.4 Mn 0.6 PO4 / C composite material.

[0099] The obtained LiFe 0.4 Mn 0.6 The PO4 / C composite material was characterized by XRD and phase analysis, and the characterization results are as follows Figure 5 As shown. Figure 5 It can be seen that LiFe 0.4 Mn 0.6 The XRD patterns of PO4 / C composite materials are compared with the standard XRD patterns (PDF#89-7115Li(Fe 0.77 Mn 0.23 )PO4) and there are no extra impurity peaks, indicating that the prepared material is lithium manganese iron phosphate and C exists in the form of an amorphous carbon layer.

[0100] 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, with a mass ratio of 90:5:5 to form an electrode sheet; metallic lithium was used as the negative electrode to assemble a simulated lithium iron manganese phosphate button battery. At 2-4.3V and 25°C, under different charge and discharge current conditions, the initial reversible capacity at 0.1C charge and discharge was 156.4mAh / g, the initial reversible capacity at 0.2C charge and discharge was 153.1mAh / g, and the initial reversible capacity at 1C charge and discharge was 146.2mAh / g. Figure 6 This is the discharge curve of the prepared lithium manganese iron phosphate button battery.

[0101] Example 2 A manganese phosphate precursor, the preparation method of which comprises the steps of: (1) Dissolve 170.73 g of manganese sulfate monohydrate (99% purity) in 800 mL of deionized water to obtain a manganese source solution; Dissolve 111.51 g of sodium carbonate (99.8% purity) in 700 mL of deionized water to obtain a carbonate solution; At 60°C, the carbonate solution was added dropwise to the manganese source solution at a rate of 35 mL / min. During the entire addition process, the stirring speed was 350 rpm. The timer was started when the addition was completed and the solution temperature reached 60°C. The reaction was continued for 4 hours, with the stirring speed maintained at 350 rpm. (2) 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 obtained filter cake is redispersed in 200 mL of pure water and beaten to obtain a manganese carbonate slurry; (3) Prepare 261.33 g of 30 wt.% phosphoric acid solution and add the solution dropwise to the manganese carbonate slurry at 60°C at a rate of 8 mL / min. Stir at 350 rpm throughout the addition process. (4) After the addition is completed, the temperature is raised, and the timing is started when the solution temperature reaches 95°C. The reaction is carried out at this temperature for 4 hours, and the stirring speed is maintained at 350 rpm. 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 obtained manganese phosphate precursor filter cake is placed in a forced air drying oven at 80°C for 12 hours, and finally 142.79 g of pink red phosphorus manganese ore type manganese phosphate precursor is obtained.

[0102] After analysis, the specific surface area of ​​the red phosphorus manganese ore type manganese phosphate precursor is 0.48m 2 / g, of which the Mn content is 37.51% and the P content is 16.86%. After calculation, the molar ratio Mn / P is 1.254, the Mn yield is 97.495%, and the P yield is 97.170%.

[0103] The manganese phosphate precursor is used to prepare a lithium manganese iron phosphate / carbon composite material. The preparation method of the lithium manganese iron phosphate / carbon composite material includes the following steps: S1. The red phosphorus manganese phosphate precursor was placed in a muffle furnace at 550° C. for heating and dehydration for 4 hours to obtain a dehydrated manganese phosphate precursor (Mn content of 44.26% and P content of 19.41%).

[0104] The raw materials were fed at a molar ratio of Li / (Fe+Mn)=1.05:1, (Fe+Mn) / P=0.97:1; 100 g of dehydrated manganese phosphate precursor, 53.34 g of anhydrous ferric phosphate (Fe / P=0.975), 23.82 g of ammonium dihydrogen phosphate (99.4 wt.%), 44.87 g of lithium carbonate (99.5 wt.%), 14.17 g of glucose, 5.31 g of polyethylene glycol 20000, 0.62 g of magnesium oxide, and 0.80 g of titanium dioxide were added to 1400 mL of pure water, and the mixture was ground in a basket mill at a speed of 1500 r / min for 60 min. After grinding, the slurry was introduced into a sand mill for grinding. After the slurry particle size reached 400 nm, the slurry was spray dried. S2. After drying, the dried and crushed material was placed in a tube furnace under a nitrogen atmosphere for sintering at a temperature of 700°C for 10 hours. After the tube furnace was naturally cooled to 80°C, the sintered material was graded and crushed to obtain a powder with a carbon content of 1.52% and a compacted density of 2.35g / cm 3 LiFe 0.3 Mn 0.7 PO4 / C composite material.

[0105] Prepared LiFe 0.3 Mn 0.7 The electrode sheet was fabricated using a PO4 / C composite material as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder, with a mass ratio of 90:5:5. A simulated lithium iron manganese phosphate button cell was assembled using metallic lithium as the negative electrode. Testing at 2-4.3V and 25°C using various charge and discharge currents revealed an initial reversible capacity of 155.8mAh / g at 0.1C, 152.3mAh / g at 0.2C, and 144.3mAh / g at 1C.

[0106] Example 3 A manganese phosphate precursor, the preparation method of which comprises the steps of: (1) Dissolve 357.85 g of manganese nitrate solution (50% by mass) in 800 mL of deionized water to obtain a manganese source solution; Dissolve 116.47 g of ammonium carbonate (99% purity) in 800 mL of deionized water to obtain a carbonate solution; At 60°C, the carbonate solution was added dropwise to the manganese source solution at a rate of 40 mL / min. During the entire addition process, the stirring speed was 350 rpm. When the addition was completed and the solution temperature reached 60°C, the timing was started and the reaction was continued for 4 hours, with the stirring speed maintained at 350 rpm. (2) 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 obtained filter cake is redispersed in 250 mL of pure water and beaten to obtain a manganese carbonate slurry; (3) Prepare 261.33 g of 30 wt.% phosphoric acid solution and add the solution dropwise to the manganese carbonate slurry at 60°C at a rate of 10 mL / min. Stir at a rate of 350 rpm throughout the addition process. (4) After the addition is completed, the temperature is raised. When the solution temperature reaches 90°C, the timer is started. The reaction is carried out at this temperature for 6 hours, and the stirring speed is maintained at 350 rpm. 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 obtained manganese phosphate precursor filter cake is placed in a forced air drying oven at 80°C for 12 hours to finally obtain 141.26 g of pink red phosphorus manganese ore type manganese phosphate precursor.

[0107] After analysis, the specific surface area of ​​the red phosphorus manganese ore type manganese phosphate precursor is 0.51m 2 / g, of which the Mn content is 37.65% and the P content is 16.95%. After calculation, the molar ratio Mn / P is 1.252, the Mn yield is 96.810%, and the P yield is 96.642%.

[0108] The manganese phosphate precursor is used to prepare a lithium manganese iron phosphate / carbon composite material. The preparation method of the lithium manganese iron phosphate / carbon composite material includes the following steps: S1. The red phosphorus manganese phosphate precursor was placed in a muffle furnace at 600° C. for heating and dehydration for 4 hours to obtain a dehydrated manganese phosphate precursor (Mn content of 44.15% and P content of 19.52%).

[0109] The raw materials were fed at a molar ratio of Li / (Fe+Mn)=1.07:1, (Fe+Mn) / P=0.975:1; 100 g of dehydrated manganese phosphate precursor, 124.15 g of anhydrous ferric phosphate (Fe / P=0.975), 22.47 g of ammonium dihydrogen phosphate (99.4 wt.%), 63.86 g of lithium carbonate (99.5 wt.%), 19.73 g of glucose, 7.40 g of polyethylene glycol 20000, and 1.97 g of magnesium hydroxide were added to 2000 mL of anhydrous ethanol, and the mixture was ground in a basket mill at a speed of 1500 r / min for 60 min. After grinding, the slurry was introduced into a sand mill for grinding. After the slurry particle size reached 400 nm, the slurry was spray dried; S2. After drying, the dried and crushed material was placed in a tube furnace under a nitrogen atmosphere for sintering at a temperature of 700°C for 10 hours. After the tube furnace was naturally cooled to 80°C, the sintered material was graded and crushed to obtain a powder with a carbon content of 1.59% and a compacted density of 2.34 g / cm 3 LiFe 0.5 Mn0.5 PO4 / C composite material.

[0110] Prepared LiFe 0.5 Mn 0.5 The electrode sheet was fabricated using a PO4 / C composite material as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder, with a mass ratio of 90:5:5. A simulated lithium iron manganese phosphate button cell was assembled using metallic lithium as the negative electrode. Testing at 2-4.3V and 25°C using various charge and discharge current conditions revealed an initial reversible capacity of 156.1mAh / g at 0.1C, 153.7mAh / g at 0.2C, and 146.0mAh / g at 1C.

[0111] Example 4 A manganese phosphate precursor, the preparation method of which comprises the steps of: (1) Dissolve 170.73 g of manganese sulfate monohydrate (99% purity) in 400 mL of deionized water to obtain a manganese source solution; Dissolve 126.18 g of ammonium carbonate (99% purity) in 400 mL of deionized water to obtain a carbonate solution; At 50°C, the carbonate solution was added dropwise to the manganese source solution at a rate of 20 mL / min. During the entire addition process, the stirring speed was 350 rpm. The timer was started when the addition was completed and the solution temperature reached 50°C. The reaction was continued for 4 hours, with the stirring speed maintained at 350 rpm. (2) 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 obtained filter cake is redispersed in 300 mL of pure water and beaten to obtain a manganese carbonate slurry; (3) Prepare 280 g of 35 wt.% phosphoric acid solution and add the solution dropwise to the manganese carbonate slurry at 50°C at a rate of 20 mL / min. Stir at a rate of 350 rpm throughout the addition process. (4) After the addition is completed, the temperature is raised. When the solution temperature reaches 95°C, the timer is started. The reaction is carried out at this temperature for 4 hours, and the stirring speed is maintained at 350 rpm. 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 obtained manganese phosphate precursor filter cake is placed in a forced air drying oven at 80°C for 12 hours to finally obtain 142.65 g of pink red phosphorus manganese ore type manganese phosphate precursor.

[0112] After analysis, the specific surface area of ​​the red phosphorus manganese ore type manganese phosphate precursor is 0.68m 2 / g, of which the Mn content is 37.46% and the P content is 16.77%. After calculation, the molar ratio Mn / P is 1.259, the Mn yield is 97.264%, and the P yield is 77.241%.

[0113] The manganese phosphate precursor is used to prepare a lithium manganese iron phosphate / carbon composite material. The preparation method of the lithium manganese iron phosphate / carbon composite material includes the following steps: S1. The red phosphorus manganese phosphate precursor was placed in a muffle furnace at 600° C. for heating and dehydration for 4 hours to obtain a dehydrated manganese phosphate precursor (Mn content of 44.09% and P content of 19.46%).

[0114] The raw materials were added according to the molar ratio of Li / Mn=1.06:1 and Mn / P=0.975:1; 100 g of dehydrated manganese phosphate precursor, 22.55 g of ammonium dihydrogen phosphate (99.4 wt.%), 31.59 g of lithium carbonate (99.5 wt.%), 9.80 g of glucose, 3.68 g of polyethylene glycol 20000, and 0.98 g of magnesium hydroxide were added to 1000 mL of anhydrous ethanol, and the mixture was ground in a basket mill at 1500 r / min for 60 min. After grinding, the slurry was introduced into a sand mill for grinding. After the slurry particle size reached 350 nm, the slurry was spray-dried; S2. After drying, the dried and crushed material was placed in a tube furnace under a nitrogen atmosphere for sintering at a temperature of 700°C for 10 hours. After the tube furnace was naturally cooled to 80°C, the sintered material was graded and crushed to obtain a powder with a carbon content of 1.60% and a compacted density of 2.32 g / cm 3 LiMnPO4 / C composite materials.

[0115] The prepared LiMnPO4 / C composite material was used as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder, with a mass ratio of 90:5:5 to form an electrode sheet. Metallic lithium was used as the negative electrode, and the resulting simulated button-type battery was assembled. Testing at 2-4.3V and 25°C using various charge and discharge current conditions revealed an initial reversible capacity of 153.8mAh / g at 0.1C, 150.5mAh / g at 0.2C, and 142.3mAh / g at 1C.

[0116] Example 5 A manganese phosphate precursor, the preparation method of which comprises the steps of: (1) Dissolve 170.73 g of manganese sulfate monohydrate (99% purity) in 600 mL of deionized water to obtain a manganese source solution; Dissolve 116.83 g of sodium carbonate (99.8% purity) in 500 mL of deionized water to obtain a carbonate solution; At 60°C, the carbonate solution was added dropwise to the manganese source solution at a rate of 10 mL / min. During the entire addition process, the stirring speed was 350 rpm. When the addition was completed and the solution temperature reached 60°C, the timing was started and the reaction was continued for 4 hours, with the stirring speed maintained at 350 rpm. (2) 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 obtained filter cake is redispersed in 200 mL of pure water and beaten to obtain a manganese carbonate slurry; (3) Prepare 220.50 g of 40 wt.% phosphoric acid solution and add the solution dropwise to the manganese carbonate slurry at 60°C at a rate of 5 mL / min. Stir at 350 rpm throughout the addition process. (4) After the addition is completed, the temperature is raised. When the solution temperature reaches 95°C, the timer is started. The reaction is carried out at this temperature for 4 hours, and the stirring speed is maintained at 350 rpm. 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 obtained manganese phosphate precursor filter cake is placed in a forced air drying oven at 80°C for 12 hours to finally obtain 141.58 g of pink red phosphorus manganese ore type manganese phosphate precursor.

[0117] After analysis, the specific surface area of ​​the red phosphorus manganese ore type manganese phosphate precursor is 0.41m 2 / g, of which the Mn content is 37.84% and the P content is 16.97%. After calculation, the molar ratio Mn / P is 1.257, the Mn yield is 97.518%, and the P yield is 86.199%.

[0118] The manganese phosphate precursor is used to prepare a lithium manganese iron phosphate / carbon composite material. The preparation method of the lithium manganese iron phosphate / carbon composite material includes the following steps: S1. The red phosphorus manganese phosphate precursor was placed in a muffle furnace at 550° C. for heating and dehydration for 6 hours to obtain a dehydrated manganese phosphate precursor (Mn content of 44.13% and P content of 19.52%).

[0119] The raw materials were fed at a molar ratio of Li / (Fe+Mn)=1.08:1 and (Fe+Mn) / P=0.98:1; 100 g of dehydrated manganese phosphate precursor, 30.81 g of anhydrous ferric phosphate (Fe / P=0.98), 21.93 g of ammonium dihydrogen phosphate (99.4 wt.%), 40.27 g of lithium carbonate (99.5 wt.%), 12.22 g of glucose, 4.58 g of polyethylene glycol 20000, 0.61 g of niobium pentoxide, and 0.61 g of magnesium oxide were added to 1400 mL of anhydrous ethanol and ground in a basket mill at 1500 r / min for 60 min. After grinding, the slurry was introduced into a sand mill for grinding. After the slurry particle size reached 400 nm, the slurry was spray-dried; S2. After drying, the dried and crushed material was placed in a tube furnace under a nitrogen atmosphere for sintering at a temperature of 700°C for 10 hours. After the tube furnace was naturally cooled to 80°C, the sintered material was graded and crushed to obtain a powder with a carbon content of 1.63% and a compacted density of 2.30 g / cm 3 LiFe 0.2 Mn 0.8 PO4 / C composite material.

[0120] Prepared LiFe 0.2 Mn 0.8 The electrode sheet was fabricated using a PO4 / C composite material as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder, with a mass ratio of 90:5:5. A simulated button cell was assembled using metallic lithium as the negative electrode. Testing at 2-4.3V and 25°C using various charge and discharge currents revealed an initial reversible capacity of 154.4mAh / g at 0.1C, 151.9mAh / g at 0.2C, and 143.2mAh / g at 1C.

[0121] Example 6 A manganese phosphate precursor, the preparation method of which comprises the steps of: (1) Dissolve 170.73 g of manganese sulfate monohydrate (99% purity) in 800 mL of deionized water to obtain a manganese source solution; Dissolve 116.47 g of ammonium carbonate (99% purity) in 800 mL of deionized water to obtain a carbonate solution; The carbonate solution was added dropwise to the manganese source solution at 70°C at a rate of 20 mL / min. During the entire addition process, the stirring speed was 350 rpm. The reaction timer was started when the addition was completed and the solution temperature reached 70°C. The reaction was continued for 4 hours, with the stirring speed maintained at 350 rpm. (2) 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 obtained filter cake is redispersed in 250 mL of pure water and beaten to obtain a manganese carbonate slurry; (3) Prepare 392.00 g of 20 wt.% phosphoric acid solution and add the solution dropwise to the manganese carbonate slurry at 70°C at a rate of 20 mL / min. Stir at a rate of 350 rpm throughout the addition process. (4) After the addition is completed, the temperature is raised. When the solution temperature reaches 85°C, the timer is started. The reaction is carried out at this temperature for 6 hours, and the stirring speed is maintained at 350 rpm. 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 obtained manganese phosphate precursor filter cake is placed in a forced air drying oven at 80°C for 12 hours to finally obtain 140.85 g of pink red phosphorus manganese ore type manganese phosphate precursor.

[0122] After analysis, the specific surface area of ​​the red phosphorus manganese ore type manganese phosphate precursor is 0.45m 2 / g, of which the Mn content is 37.91% and the P content is 17.02%. After calculation, the molar ratio Mn / P is 1.256, the Mn yield is 97.192%, and the P yield is 96.756%.

[0123] The manganese phosphate precursor is used to prepare a lithium manganese iron phosphate / carbon composite material. The preparation method of the lithium manganese iron phosphate / carbon composite material includes the following steps: S1. The red phosphorus manganese phosphate precursor was placed in a muffle furnace at 500° C. for heating and dehydration for 6 hours to obtain a dehydrated manganese phosphate precursor (Mn content of 44.27% and P content of 19.59%).

[0124] The raw materials were fed at a molar ratio of Li / (Fe+Mn)=1.07:1, (Fe+Mn) / P=0.985:1; 100 g of dehydrated manganese phosphate precursor, 82.99 g of anhydrous ferric phosphate (Fe / P=0.94), 18.80 g of ammonium dihydrogen phosphate (99.4 wt.%), 53.36 g of lithium carbonate (99.5 wt.%), 16.14 g of glucose, 6.05 g of polyethylene glycol 20000, and 1.61 g of magnesium hydroxide were added to 1600 mL of anhydrous ethanol, and the mixture was ground in a basket mill at a speed of 1500 r / min for 60 min. After grinding, the slurry was introduced into a sand mill for grinding. After the slurry particle size reached 400 nm, the slurry was spray-dried; S2. After drying, the dried and crushed material was placed in a tube furnace under a nitrogen atmosphere for sintering at a temperature of 750°C for 11 hours. After the tube furnace was naturally cooled to 80°C, the sintered material was graded and crushed to obtain a powder with a carbon content of 1.61% and a compacted density of 2.34 g / cm 3 LiFe 0.4 Mn0.6 PO4 / C composite material.

[0125] Prepared LiFe 0.4 Mn 0.6 The electrode sheet was fabricated using a PO4 / C composite material as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder, with a mass ratio of 90:5:5. A simulated button cell was assembled using metallic lithium as the negative electrode. Testing at 2-4.3V and 25°C using various charge and discharge currents revealed an initial reversible capacity of 155.3mAh / g at 0.1C, 153.1mAh / g at 0.2C, and 144.1mAh / g at 1C.

[0126] Comparative Example 1 Different from Example 1, in step (2) of preparing the manganese phosphate precursor, no washing is performed.

[0127] (1) Dissolve 170.73 g of manganese sulfate monohydrate (99% purity) in 800 mL of deionized water to obtain a manganese source solution; Dissolve 116.47 g of ammonium carbonate (99% purity) in 800 mL of deionized water to obtain a carbonate solution; The carbonate solution was added dropwise to the manganese source solution at 60°C at a rate of 40 mL / min. During the entire addition process, the stirring speed was 350 rpm. When the addition was completed and the solution temperature reached 60°C, the timing was started, and the reaction was continued for 4 hours while maintaining the stirring speed at 350 rpm to obtain a manganese carbonate slurry. (2) Prepare 261.33 g of 30 wt.% phosphoric acid solution and add the solution dropwise to the manganese carbonate slurry at 60°C at a rate of 6.5 mL / min. Stir at 350 rpm throughout the addition process. (3) After the addition is completed, the temperature is raised. When the solution temperature reaches 95°C, the timer is started. The reaction is carried out at this temperature for 4 hours, and the stirring speed is maintained at 350 rpm. 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 obtained manganese phosphate precursor filter cake is placed in an 80°C forced air drying oven for 12 hours to finally obtain 172.25 g of light pink manganese phosphate precursor.

[0128] After analysis, the specific surface area of ​​the manganese phosphate precursor is 7.16m 2 / g, of which the Mn content was 31.58% and the P content was 14.34%. The calculated molar ratio Mn / P was 1.242, the Mn yield was 99.014%, and the P yield was 99.696%. XRD characterization and phase analysis also revealed the presence of manganous ammonium phosphate phase.

[0129] The manganese phosphate precursor is used to prepare a lithium manganese iron phosphate / carbon composite material. The preparation method of the lithium manganese iron phosphate / carbon composite material includes the following steps: S1. The red phosphorus manganese phosphate precursor was placed in a muffle furnace at 550° C. for heating and dehydration for 4 hours to obtain a dehydrated manganese phosphate precursor (Mn content of 42.23% and P content of 19.21%).

[0130] The raw materials were fed at a molar ratio of Li / (Fe+Mn)=1.06:1, (Fe+Mn) / P=0.975:1; 100 g of dehydrated manganese phosphate precursor, 79.16 g of anhydrous ferric phosphate (molar ratio Fe / P=0.975), 19.51 g of ammonium dihydrogen phosphate (99.4 wt.%), 50.43 g of lithium carbonate (99.5 wt.%), 16.37 g of glucose, 6.14 g of polyethylene glycol 20000, 0.82 g of magnesium oxide, and 0.82 g of titanium dioxide were added to 1600 mL of anhydrous ethanol, and the mixture was ground in a basket mill at a speed of 1500 r / min for 60 min. After grinding, the slurry was introduced into a sand mill for grinding. After the slurry particle size reached 400 nm, the slurry was spray-dried; S2. After drying, the dried and crushed material was placed in a tube furnace under a nitrogen atmosphere for sintering at a temperature of 700°C for 10 hours. After the tube furnace was naturally cooled to 80°C, the sintered material was graded and crushed to obtain a powder with a carbon content of 1.85% and a compacted density of 2.15g / cm 3 LiFe 0.4 Mn 0.6 PO4 / C composite material.

[0131] Prepared LiFe 0.4 Mn 0.6 The electrode sheet was fabricated using a PO4 / C composite material as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder, with a mass ratio of 90:5:5. A simulated lithium iron manganese phosphate button cell was assembled using metallic lithium as the negative electrode. Testing at 2-4.3V and 25°C using various charge and discharge current conditions revealed an initial reversible capacity of 149.2mAh / g at 0.1C, 145.3mAh / g at 0.2C, and 137.1mAh / g at 1C.

[0132] Comparative Example 2 The difference from Example 1 is that the reaction temperature during the preparation of the manganese phosphate precursor is 30°C.

[0133] A manganese phosphate precursor, the preparation method of which comprises the steps of: (1) Dissolve 170.73 g of manganese sulfate monohydrate (99% purity) in 800 mL of deionized water to obtain a manganese source solution; Dissolve 116.47 g of ammonium carbonate (99% purity) in 800 mL of deionized water to obtain a carbonate solution; At 30°C, the carbonate solution was added dropwise to the manganese source solution at a rate of 40 mL / min. During the entire addition process, the stirring speed was 350 rpm. After the addition was completed, the timer was started at 30°C, and the reaction was continued for 4 hours, with the stirring speed maintained at 350 rpm. (2) 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 obtained filter cake is redispersed in 250 mL of pure water and beaten to obtain a manganese carbonate slurry; (3) Prepare 261.33 g of 30 wt.% phosphoric acid solution and add the solution dropwise to the manganese carbonate slurry at 30°C at a rate of 6.5 mL / min. Stir at 350 rpm throughout the addition process. (4) After the addition is completed, the reaction is carried out at 30°C for 4 hours, and the stirring speed is maintained at 350 rpm. 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 obtained manganese phosphate precursor filter cake is placed in a forced air drying oven at 80°C for 12 hours to finally obtain 109.75 g of pink red phosphorus manganese ore type manganese phosphate precursor.

[0134] After analysis, the specific surface area of ​​the manganese phosphate precursor is 13.51m 2 / g, with a Mn content of 37.53% and a P content of 16.74%. The calculated molar ratio Mn / P was 1.264, with a Mn yield of 74.976% and a P yield of 74.155%. XRD characterization and phase analysis confirmed the precursor to a pyrophosphate-type manganese phosphate. However, the reaction temperature was too low, which affected the crystal nucleation rate and grain growth rate, resulting in fine product grains and a low elemental yield.

[0135] The manganese phosphate precursor is used to prepare a lithium manganese iron phosphate / carbon composite material. The preparation method of the lithium manganese iron phosphate / carbon composite material includes the following steps: S1. Place the red phosphorus manganese phosphate precursor in a muffle furnace at 550°C for 4 hours to heat and dehydrate to obtain a dehydrated manganese phosphate precursor (Mn content is 43.07%, P content is 18.85%); add raw materials according to the molar ratio of Li / (Fe+Mn)=1.06:1, (Fe+Mn) / P=0.975:1; 100g of the dehydrated manganese phosphate precursor, 80.74g of anhydrous iron phosphate (molar ratio Fe / P=0.975:1), 22 0.64 g of ammonium dihydrogen phosphate (99.4 wt.%), 51.43 g of lithium carbonate (99.5 wt.%), 16.37 g of glucose, 6.14 g of polyethylene glycol 20000, 0.82 g of magnesium oxide, and 0.82 g of titanium dioxide were added to 1600 mL of anhydrous ethanol and ground in a basket mill at 1500 r / min for 60 min. After grinding, the slurry was introduced into a sand mill for grinding. After the slurry particle size reached 400 nm, the slurry was spray-dried; S2. After drying, the dried and crushed material was placed in a tube furnace under nitrogen atmosphere for sintering at 700℃ for 10 hours. After the tube furnace was cooled to 80℃, the sintered material was graded and crushed to obtain a powder with a carbon content of 1.58% and a powder pressure of 2.25g / cm 3 LiFe 0.4 Mn 0.6 PO4 / C composite materials; Prepared LiFe 0.4 Mn 0.6 The electrode sheet was made of a PO4 / C composite material as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder in a mass ratio of 90:5:5. Metallic lithium was used as the negative electrode and assembled into a simulated button cell. Testing at 2-4.3V and 25°C using different charge and discharge current conditions revealed an initial reversible capacity of 150.8mAh / g at 0.1C, 147.6mAh / g at 0.2C, and 138.5mAh / g at 1C.

[0136] Comparative Example 3 The difference from Example 1 is that an excess amount of phosphoric acid is added when preparing the manganese phosphate precursor.

[0137] A manganese phosphate precursor, the preparation method of which comprises the steps of: (1) Dissolve 170.73 g of manganese sulfate monohydrate (99% purity) in 800 mL of deionized water to obtain a manganese source solution; Dissolve 116.47 g of ammonium carbonate (99% purity) in 800 mL of deionized water to obtain a carbonate solution; At 60°C, the carbonate solution was added dropwise to the manganese source solution at a rate of 40 mL / min. During the entire addition process, the stirring speed was 350 rpm. When the addition was completed and the solution temperature reached 60°C, the timing was started and the reaction was continued for 4 hours, with the stirring speed maintained at 350 rpm. (2) 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 obtained filter cake is redispersed in 250 mL of pure water and beaten to obtain a manganese carbonate slurry; (3) Prepare 490.00 g of 30 wt.% phosphoric acid solution and add the solution dropwise to the manganese carbonate slurry at 60°C at a rate of 12.2 mL / min. Stir at a rate of 350 rpm throughout the addition process. (4) After the addition is completed, the temperature is raised. When the solution temperature reaches 95°C, the timer is started. The reaction is carried out at this temperature for 4 hours, and the stirring speed is maintained at 350 rpm. 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 obtained manganese phosphate precursor filter cake is placed in a forced air drying oven at 80°C for 12 hours to finally obtain 109.53 g of pink red phosphorus manganese ore type manganese phosphate precursor.

[0138] After analysis, the specific surface area of ​​the red phosphorus manganese ore type manganese phosphate precursor is 1.19m 2 / g, of which the Mn content was 36.68% and the P content was 16.59%. The calculated molar ratio Mn / P was 1.247, the Mn yield was 73.129%, and the P yield was 39.115%. Excessive phosphoric acid caused the solution pH to be too low, resulting in incomplete precipitation of the red phosphorus manganese phosphate.

[0139] The manganese phosphate precursor is used to prepare a lithium manganese iron phosphate / carbon composite material. The preparation method of the lithium manganese iron phosphate / carbon composite material includes the following steps: S1. Place the red phosphorus manganese phosphate precursor in a muffle furnace at 550°C for 4 hours to heat and dehydrate to obtain a dehydrated manganese phosphate precursor (Mn content is 42.58%, P content is 19.28%); add raw materials according to the molar ratio of Li / (Fe+Mn)=1.06:1, (Fe+Mn) / P=0.975:1; 100g of the dehydrated manganese phosphate precursor, 79.82g of anhydrous iron phosphate (Fe / P=0.975), 19.9 7 g of ammonium dihydrogen phosphate (99.4 wt.%), 50.84 g of lithium carbonate (99.5 wt.%), 16.37 g of glucose, 6.14 g of polyethylene glycol 20000, 0.82 g of magnesium oxide, and 0.82 g of titanium dioxide were added to 1600 mL of anhydrous ethanol and ground in a basket grinder at a speed of 1500 r / min for 60 min. After grinding, the slurry was introduced into a sand mill for grinding. After the slurry particle size reached 400 nm, the slurry was spray dried.

[0140] S2. After drying, the dried and crushed material was placed in a tube furnace under nitrogen atmosphere for sintering at 700°C for 10 hours. After the tube furnace was cooled to 80°C, the sintered material was graded and crushed to obtain a powder with a carbon content of 1.61% and a compacted density of 2.29g / cm 3 LiFe 0.4 Mn 0.6 PO4 / C composite material.

[0141] Prepared LiFe 0.4 Mn 0.6 The electrode sheet was made of a PO4 / C composite material as the positive electrode material, acetylene black as the conductive agent, and polytetrafluoroethylene as the binder, with a mass ratio of 90:5:5. Metallic lithium was used as the negative electrode, and the resulting simulated button cell was assembled. Testing at 2-4.3V and 25°C using different charge and discharge current conditions revealed an initial reversible capacity of 150.3mAh / g at 0.1C, 146.5mAh / g at 0.2C, and 139.2mAh / g at 1C.

[0142] It can be seen from the above technical effects that the washed manganese phosphate salt precursor of the embodiment of the present invention has a high Mn and P content and yield; the button battery with the prepared lithium iron manganese phosphate / carbon composite material as the positive electrode material has a high discharge reversible capacity.

[0143] 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 manganese phosphate precursor, characterized in that: Including steps: (1) mixing a carbonate solution and a manganese source solution at a reaction temperature of 50-80° C. to obtain a manganese carbonate slurry A; (2) filtering, washing, and beating the manganese carbonate slurry A to obtain manganese carbonate slurry B; (3) mixing and stirring the phosphoric acid solution and the manganese carbonate slurry B under the reaction temperature conditions of step (1); (4) Heating the reaction, filtering, washing, and drying to obtain a red phosphorus manganese ore type manganese phosphate salt precursor.

2. The preparation method according to claim 1, characterized in that In step (1), the carbonate is selected from one or more of ammonium carbonate, ammonium bicarbonate, and sodium carbonate; the manganese source is selected from one or more of manganous sulfate, manganous nitrate, manganous chloride, and manganous citrate; In step (1), the concentration of the carbonate solution is 0.5-6.0 mol / L, and the concentration of the manganese source solution is 0.5-6.0 mol / L.

3. The preparation method according to claim 1, characterized in that In step (1), the molar ratio of the carbonate to the manganese source is 0.5-1.5:1.0; in step (1), the reaction temperature is 50-80° C., and the reaction time is 2-6 hours.

4. The preparation method according to claim 1, characterized in that In step (2), the washing is performed until the conductivity of the filtrate is less than 300 μS / cm; In step (2), the solid content of the manganese carbonate slurry B is 10-50%.

5. The preparation method according to claim 1, characterized in that In step (3), the mass concentration of the phosphoric acid solution is 20-40%; in step (3), during the mixing and stirring, the molar ratio of phosphoric acid to manganese source is 0.5-1.3:1.

0.

6. The preparation method according to claim 1, characterized in that In step (4), the reaction temperature is 80-100° C., and the reaction time is 2-6 hours.

7. The manganese phosphate precursor prepared by the preparation method according to any one of claims 1 to 6.

8. A lithium iron manganese phosphate / carbon composite material, characterized in that: It is prepared by the manganese phosphate precursor prepared by the preparation method according to any one of claims 1 to 6 or the manganese phosphate precursor according to claim 7.

9. The method for preparing the lithium manganese iron phosphate / carbon composite material according to claim 8, characterized in that: Including steps: S1. Mixing a lithium source, anhydrous iron phosphate, a manganese phosphate precursor, a phosphorus source, a carbon source, and an additive in a liquid phase system to obtain a mixture, grinding, and drying to obtain a lithium iron manganese phosphate / carbon composite material precursor; S2. The lithium manganese iron phosphate / carbon composite material precursor is sintered under an inert gas protection atmosphere to finally obtain the lithium manganese iron phosphate / carbon composite material.

10. Use of the manganese phosphate precursor according to claim 7 or the lithium manganese iron phosphate / carbon composite material according to claim 8 in the preparation of a battery positive electrode material.

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