Lithium manganese iron phosphate cathode material, preparation method thereof, manganese iron phosphate precursor and preparation method thereof, lithium ion battery

Abstract

The present invention relates to the field of preparation technologies of lithium-ion cathode materials, and discloses a lithium manganese iron phosphate cathode material, a preparation method thereof, a manganese iron phosphate precursor and a preparation method thereof, and a lithium-ion battery. The cathode material has a structure represented by Formula I, Li d Mn 1-a-b-c Fe a R b PO4 / C Formula I where 0.1 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.08, 0.9 < d ≦ 1.2, R is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr and Ti, and the volume resistivity of the cathode material is 10~10 4 Ω·cm. The cathode material contains specific doping elements and has a low volume resistivity, which can effectively improve the electrochemical performance of the lithium-ion battery when it is used in the preparation of the lithium-ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing lithium-ion cathode materials, specifically to lithium iron manganese phosphate cathode materials and their preparation methods, lithium iron manganese phosphate precursors and their preparation methods, and lithium-ion batteries.

Background Art

[0002] As an important power system, lithium-ion batteries are widely used in 3C products such as computers, communication tools, and electronic tools, in the fields of electric vehicles such as EV and PHEV, and in energy storage systems. Lithium iron phosphate has characteristics such as good safety, good stability, and low cost as a lithium-ion battery cathode material, and its market share is increasing. However, lithium iron phosphate has disadvantages such as poor electronic conductivity, small lithium-ion diffusion coefficient, and low energy density, which limit its further development and use in the field of electric vehicles. Lithium iron manganese phosphate, as an upgraded product of lithium iron phosphate, has the same specific capacity as lithium iron phosphate (theoretical capacity of 170 mAh / g), but the introduction of manganese increases the redox potential, thereby improving the energy density of the material.

[0003] Currently, the synthesis methods of lithium iron manganese phosphate mainly include high-temperature solid-phase method, hydrothermal method, coprecipitation method, etc. Here, the process flow of the high-temperature solid-phase method is simple and suitable for industrial production, but it is difficult to achieve uniform mixing of manganese and iron at the atomic level, with poor consistency and non-uniform particle morphology, which affects the tap density and discharge capacity. The main advantages of the coprecipitation method are that the particle composition is uniform, the dimensional structure is easy to adjust and control, the operation is simple and industrial production is possible, and the preparation of lithium iron manganese phosphate precursor is the key to synthesizing high-performance materials.

[0004] At present, the research on iron manganese phosphate precursors is relatively extensive. CN114057177A discloses ferrous manganese phosphate and its preparation method, which includes the steps of dissolving divalent manganese salt and divalent iron salt in water to obtain a mixed salt solution of manganese salt and iron salt; adding a phosphorus source to the mixed salt solution to obtain a precursor solution; adding alkali coprecipitation to the precursor solution to obtain a ferrous iron manganese phosphate slurry containing ferrous iron phosphate precipitation and iron manganese phosphate precipitation; and washing, filtering, and drying the ferrous iron manganese phosphate slurry to obtain ferrous iron manganese phosphate. The sample prepared by this method shows phase separation of ferrous iron phosphate and manganese phosphate, resulting in a non-uniform structure and a variable ratio of metal to phosphorus. Therefore, it is necessary to replenish the phosphorus source during the preparation process of the cathode material, and it is difficult to control the ratio of metal to phosphorus, which limits the performance of the cathode material.

[0005] CN107697899A discloses a method for preparing iron manganese phosphate. First, precipitate divalent iron manganese under basic conditions, add an oxidizing agent to oxidize divalent iron manganese to trivalent iron manganese, and then add a phosphorus source to perform phosphate conversion. The flow of this preparation method is complex, there are many phase transitions between substances, defects are likely to occur, and it is difficult to control indicators such as the particle size and morphology of the precursor.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a lithium iron manganese phosphate cathode material and its preparation method, an iron manganese phosphate precursor and its preparation method, and a lithium ion battery. The lithium iron manganese phosphate cathode material contains specific doping elements, has high purity, and the cathode material has a low volume resistivity. When it is used in the preparation of a lithium ion battery, it can effectively improve the electrochemical performance of the lithium ion battery. Specifically, the lithium ion battery has a high specific capacity, high cycle performance, and high energy density.

Means for Solving the Problems

[0007] To achieve the above object, a first aspect of the present invention provides a lithium iron manganese phosphate cathode material, and the cathode material has a structure represented by Formula I, L id Mn 1-a-b-c Fe a R b PO4 / C Formula I where 0.1 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.08, 0.9 < d ≦ 1.2, and R is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti, the volume resistivity of the cathode material is 10~10 4 Ω·cm, the relationship between the actual molar content ratio m'' of Mn element and Fe element at any position in the cathode material and the theoretical molar content ratio m of Mn element and Fe element at any position in the cathode material is Δm c =|m'' - m| / m ≦ 5%.

[0008] A second aspect of the present invention provides a method for preparing a lithium iron manganese phosphate cathode material, and the preparation method includes step S1 of mixing a manganese source, an iron source, an R1 source, and water to obtain a mixed salt solution, step S2 of mixing a phosphorus source and water, adding a pH adjuster, and obtaining a phosphorus source solution, step S3 of adding the mixed salt solution, the phosphorus source solution, and an oxidizing agent in parallel flow to a reaction kettle, performing a coprecipitation reaction, filtering, washing, and drying to obtain the lithium iron manganese phosphate precursor, step S4 of mixing the lithium iron manganese phosphate precursor, a lithium source, a carbon source, and an R2 source to obtain a mixture, step S5 of firing the mixture in the presence of a protective atmosphere to obtain the lithium iron manganese phosphate cathode material.

[0009] A third aspect of the present invention provides a lithium iron manganese phosphate cathode material manufactured by the above preparation method.

[0010] The fourth aspect of the present invention provides a manganese iron phosphate precursor material having a structure represented by Formula II, Mn 1-x-y Fe x R1 y P z O4·nH2O Formula II, where 0.1 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.04, 0.95 ≦ z ≦ 1.10, 0.95 ≦ n ≦ 1.5, and R1 is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti.

[0011] The fifth aspect of the present invention provides a method for preparing a manganese iron phosphate precursor, and the preparation method includes: Step (1) of mixing a manganese source, an iron source, an R1 source, and water to obtain a mixed salt solution; Step (2) of mixing a phosphorus source and water, adding a pH adjuster, and obtaining a phosphorus source solution; Step (3) of adding the mixed salt solution, the phosphorus source solution, and an oxidizing agent in parallel to a reaction kettle, performing a coprecipitation reaction, filtering, washing, and drying to obtain the manganese iron phosphate precursor.

[0012] The sixth aspect of the present invention provides a manganese iron phosphate precursor produced by the above preparation method.

[0013] The seventh aspect of the present invention provides a lithium ion battery including the above lithium manganese iron phosphate cathode material or a cathode material produced by the above manganese iron phosphate precursor.

[0014] By the above technical solution, the lithium manganese iron phosphate cathode material and its preparation method, the manganese iron phosphate precursor and its preparation method, and the lithium ion battery according to the present invention achieve the following beneficial effects.

[0015] 1. The lithium manganese iron phosphate cathode material according to the present invention contains specific doping elements, and the cathode material has a low volume resistivity and high purity, so it can effectively avoid the formation of hetero phases. When it is used in the preparation of lithium-ion batteries, it can effectively improve the electrochemical performance of lithium-ion batteries. Specifically, the lithium-ion battery has a high specific capacity, high cycle performance and high energy density.

[0016] Furthermore, the distribution of manganese and iron elements in the lithium manganese iron phosphate cathode material according to the present invention is uniform, the primary particles are small, the carbon coating is uniform, the tap density is high, which further improves the electrochemical performance of the lithium-ion battery.

[0017] 2. In the preparation method of the lithium manganese iron phosphate cathode material according to the present invention, it is obtained by mixing a precursor with a specific composition with a lithium source, a carbon source and an R2 source and then firing. Here, the precursor contains a specific doping element R1, and the doping element enters the metal site to form nanoparticles with a stable structure. Furthermore, the obtained lithium manganese iron phosphate cathode material has high purity and low volume resistivity.

[0018] Furthermore, in the present invention, using a manganese source, an iron source, an R1 source, a phosphorus source and an oxidizing agent as raw materials, in particular, adding a mixed salt solution containing a manganese source, an iron source and an R1 source, a phosphorus source solution and an oxidizing agent into the reaction kettle in parallel flow. After the metal ions react with the oxidizing agent and are oxidized, they quickly combine with phosphate groups to form a precipitate, effectively avoiding the disproportionation reaction of trivalent manganese ions in the aqueous solution, and realizing precipitation while oxidizing. Also, the parallel flow transportation of the liquid avoids the phenomenon that the ion concentration in the solution is too high and manganese and iron precipitate sequentially, causing metal segregation, and realizes the uniform coprecipitation of manganese and iron. And the metal stoichiometric ratio in the obtained lithium manganese iron phosphate precursor is stable, the molar ratio P / Me of phosphorus to metal can be adjusted and controlled, the primary particles are small, the secondary particles are uniform, the morphology can be adjusted and controlled, the structure is stable, the synthesis process is simple, environmentally friendly, pollution-free, and suitable for industrial production.

[0019] Furthermore, by controlling the molar ratio K1 of the addition amounts of the phosphorus source and the metals (manganese source, iron source, and R1 source), the pH of the phosphorus source solution, and the reaction temperature T to satisfy a specific relationship, the adjustment and control of the molar ratio K of phosphorus and metals in the manganese iron phosphate precursor are realized, and further the adjustment and control of the performance of the lithium manganese iron phosphate cathode material are realized. The obtained lithium manganese iron phosphate cathode material has excellent electrochemical performance.

[0020] The method for preparing the lithium manganese iron phosphate cathode material according to the present invention is non-toxic and harmless, the process is simple, the raw materials are easy to obtain, the equipment requirements are low, the popularization and application are easy, and it can be widely applied to the industrial production of the lithium manganese iron phosphate cathode material.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0022] It should be understood that the endpoints and any values within the ranges disclosed in this specification are not limited to such exact ranges or values, but include values close to these ranges or values. In the case of numerical ranges, between the endpoint values of each range, between the endpoint values of each range and a single point value, and between single point values, one or more new numerical ranges are obtained by combining them with each other, and these numerical ranges are regarded as specifically disclosed in this specification.

[0023] The first aspect of the present invention provides a lithium iron manganese phosphate cathode material, and the cathode material has a structure represented by Formula I, Li d Mn 1-a-b-c Fe a R b PO4 / C Formula I where 0.1 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.08, 0.9 < d ≦ 1.2, and R is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti, The volume resistivity of the cathode material is 10~10 4 Ω·cm, The relationship between the actual molar content ratio m'' of Mn element and Fe element at any position in the cathode material and the theoretical molar content ratio m of Mn element and Fe element at any position in the cathode material is Δm c =|m'' - m| / m ≦ 5%, which is characterized by this.

[0024] In the present invention, the lithium iron manganese phosphate cathode material contains specific doping elements, and the cathode material has a low volume resistivity and high purity. The distribution of manganese and iron elements in the lithium iron manganese phosphate cathode material is uniform, effectively avoiding the formation of hetero phases. Specifically, the difference between the actual content ratio and the theoretical content ratio of metal Mn element and Fe element at any position is small, and the manganese and iron elements in the lithium iron manganese phosphate cathode material are uniformly distributed without segregation. When it is used in the preparation of lithium-ion batteries, the electrochemical performance of lithium-ion batteries is effectively improved. Specifically, the lithium-ion battery has a high specific capacity, high cycle performance, and high energy density.

[0025] In the present invention, the actual content of Mn element and Fe element at any position in the cathode material is m'' measured by the EDS method.

[0026] In the present invention, the molar content ratio m of Mn element to Fe element at any position in the positive electrode material is set as m = (1 - a - b - c) / a.

[0027] In the present invention, when testing the actual content m'' of Mn element and Fe element, the area of the selected position occupies 1 - 30% of the area of the selected positive electrode material particles. In the present invention, when the area of the selected position satisfies the above range when testing the actual content m'' of Mn element and Fe element, while ensuring the feasibility of the test, the averaging effect can be effectively avoided, thereby better representing the uniformity of the distribution of Mn element and Fe element.

[0028] Furthermore, in Formula I, 0.15 ≤ a ≤ 0.45, 0 < b ≤ 6, 0.95 < d ≤ 1.15.

[0029] Furthermore, in Formula I, R is selected from at least one of Al, Co, Ni, Mg, Al, W, Nb, Zr, and Ti.

[0030] In a specific embodiment of the present invention, the lithium manganese iron phosphate positive electrode material contains two or more different types of elements R. Specifically, the lithium manganese iron phosphate positive electrode material has a structure represented by Formula II, Li d Mn 1-a-b-c Fe a R’ b R’’ c PO4 / C Formula II Here, 0.1 ≤ a ≤ 0.5, 0 ≤ b ≤ 0.04, 0 ≤ c ≤ 0.04, 0.9 < d ≤ 1.2, R’ is selected from at least one of Al, Cu, Zn, Zr, and Ti, and R’’ is selected from at least one of Mg, Ca, Sr, V, Cr, Co, Ni, Y, Mo, Nb, B, W, La, and Sm.

[0031] In a specific embodiment of the present invention, in Formula II, 0.15 ≤ a ≤ 0.45, 0 < b ≤ 0.03, 0 < c ≤ 0.03, 0.95 < d ≤ 1.15.

[0032] In a specific embodiment of the present invention, in Formula II, R' is selected from at least one of Al, Zr, and Ti, and R'' is selected from at least one of Co, Ni, Mg, Y, La, W, and Nb.

[0033] Furthermore, the volume resistivity of the positive electrode material is 10 to 10 3 Ω·cm.

[0034] Even further, the volume resistivity of the positive electrode material is 10 to 500 Ω·cm.

[0035] According to the present invention, based on the total weight of the lithium iron manganese phosphate positive electrode material, the carbon content is 0.5 to 5 wt%.

[0036] In the present invention, when the carbon content in the lithium iron manganese phosphate positive electrode material satisfies the above range, the positive electrode material has good electronic conductivity, and furthermore, the specific capacity, cycle performance, and rate performance of the lithium ion battery manufactured with the positive electrode material are improved.

[0037] Furthermore, based on the total weight of the lithium iron manganese phosphate positive electrode material, the carbon content is 1 to 3 wt%.

[0038] Furthermore, Δm c =|m'' - m| / m ≤ 3%.

[0039] According to the present invention, the tap density of the positive electrode material is 1.5 to 3.5 g / cm 3 , preferably 2 to 3 g / cm 3 .

[0040] According to the present invention, the specific surface area of the positive electrode material is 10 to 60 m 2 / g, preferably 10 to 25 m 2 / g.

[0041] According to the present invention, the lithium iron manganese phosphate positive electrode material has a secondary particle structure formed by primary particles.

[0042] According to the present invention, the average particle size of the positive electrode material is 1 to 50 μm, preferably 7 to 15 μm.

[0043] According to the present invention, the average particle size of the primary particles is 10 to 500 nm.

[0044] In the present invention, the positive electrode material has small primary particle diameters, shortens the diffusion path of lithium ions, improves the ionic conductivity of the positive electrode material, and effectively improves the electrochemical performance of the lithium ion battery when it is used in the lithium ion battery.

[0045] Furthermore, the average particle size of the primary particles is 10 to 200 nm.

[0046] The second aspect of the present invention provides a method for preparing a lithium iron manganese phosphate positive electrode material, and the preparation method includes: Step S1 of mixing a manganese source, an iron source, an R1 source and water to obtain a mixed salt solution; Step S2 of mixing a phosphorus source and water, adding a pH adjuster, and obtaining a phosphorus source solution; Step S3 of adding the mixed salt solution, the phosphorus source solution and an oxidizing agent in parallel to a reaction kettle to perform a coprecipitation reaction, filtering, washing and drying to obtain the lithium iron manganese phosphate precursor; Step S4 of mixing the lithium iron manganese phosphate precursor, a lithium source, a carbon source and an R2 source to obtain a mixture; Step S5 of firing the mixture in the presence of a protective atmosphere to obtain the lithium iron manganese phosphate positive electrode material.

[0047] In the present invention, R1 and R2 are for distinguishing the difference in the addition timing of the R source, and do not limit the type of element of the R source. Both the R1 source and the R2 source are for introducing the R source into the positive electrode material.

[0048] In the present invention, a precursor with a specific structure is manufactured by mixing it with a lithium source, a carbon source, and an R2 source and then firing it. Here, a specific doping element R1 is included in the precursor, and the doping element enters the metal sites to form nanoparticles having a stable structure. Furthermore, the obtained lithium manganese iron phosphate cathode material has high purity and a low volume resistivity. When the obtained lithium manganese iron phosphate cathode material is used in a lithium-ion battery, the electrochemical performance of the lithium-ion battery is effectively improved. Specifically, the lithium-ion battery has a high specific capacity, high cycle performance, and high energy density.

[0049] In the present invention, using a manganese source, an iron source, an R1 source, a phosphorus source, and an oxidizing agent as raw materials, in particular, by adding a mixed salt solution containing a manganese source, an iron source, and an R1 source, a phosphorus source solution, and an oxidizing agent into a reaction kettle in parallel flow, after the metal ions react with the oxidizing agent and are oxidized, they quickly combine with phosphate groups to form a precipitate, effectively avoiding the disproportionation reaction of trivalent manganese ions in the aqueous solution and realizing precipitation while being oxidized. Also, the parallel flow transportation of the liquid avoids the phenomenon of metal segregation caused by the ion concentration in the solution being too high and manganese and iron precipitating sequentially, and realizes uniform coprecipitation of manganese and iron. Moreover, the metal stoichiometric ratio in the obtained lithium manganese iron phosphate precursor is stable, the molar ratio P / Me of phosphorus to metal is adjustable and controllable, the primary particles are small, the secondary particles are uniform, the morphology is adjustable and controllable, the structure is stable, the synthesis process is simple, environmentally friendly, pollution-free, and suitable for industrial production.

[0050] According to the present invention, the lithium manganese iron phosphate precursor has a structure represented by Formula II, Mn 1-x-y Fe x R1 y P z O4·nH2O Formula II where 0.1 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.04, 0.95 ≦ z ≦ 1.10, 0.95 ≦ n ≦ 1.5, and R1 is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti.

[0051] Furthermore, in Formula II, 0.15 ≦ x ≦ 0.45, 0 < y ≦ 0.03, 0.95 ≦ z ≦ 1.05, 0.95 ≦ n ≦ 1.2, and R1 is selected from at least one of Al, Co, Ni, Mg, Al, W, Nb, Zr, and Ti.

[0052] According to the present invention, the lithium manganese iron phosphate cathode material has the configuration described in Formula I. Li d Mn 1-a-b-c Fe a R b PO4PO4 / C Formula I Here, 0.1 ≦ a ≦ 0.5, 0 ≦ b ≦ 0.08, 0.9 < d ≦ 1.2, and R is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti.

[0053] Furthermore, in Formula I, 0.15 ≦ a ≦ 0.45, 0 < b ≦ 0.06, 0.95 < d ≦ 1.15.

[0054] Furthermore, in Formula I, R is selected from at least one of Al, Co, Ni, Mg, Al, W, Nb, Zr, and Ti.

[0055] According to the present invention, the relationship between the actual molar content ratio m' of the Mn element and the Fe element at any position in the manganese iron phosphate precursor and the theoretical molar content ratio m0 of the Mn element and the Fe element at any position in the lithium manganese iron phosphate precursor is Δm p = |m' - m0| / m0 ≦ 5%.

[0056] In the present invention, the distribution of manganese and iron elements in the manganese iron phosphate precursor is uniform. In particular, the difference between the actual content ratio value and the theoretical content ratio value of metal Mn element and Fe element at any position is small, indicating that the manganese and iron elements in the manganese iron phosphate precursor are uniformly distributed and there is no segregation phenomenon. When the precursor is used for the preparation of the cathode material, a uniform distribution of manganese, iron and phosphorus elements in the cathode material is realized, and the segregation phenomenon of elements in the cathode material is avoided, so that the capacity performance and cycle performance of the lithium ion battery including the lithium manganese iron phosphate cathode material are significantly improved.

[0057] In the present invention, the theoretical molar content ratio m0 of Mn element and Fe element at any position in the lithium manganese iron phosphate precursor is set as m0 = (1 - x - y) / x.

[0058] In the present invention, the actual content of Mn element and Fe element at any position in the precursor is m' measured by the EDS method.

[0059] In the present invention, when testing the actual content m' of Mn element and Fe element, the area of the selected position accounts for 1 - 30% of the area of the selected precursor particles. In the present invention, when the area of the selected position meets the above range when testing the actual content m'' of Mn element and Fe element, while ensuring the feasibility of the test, the averaging effect can be effectively avoided, thereby better expressing the uniformity of the distribution of Mn element and Fe element.

[0060] Furthermore, Δm p = |m' - m0| / m0 ≦ 3%.

[0061] According to the present invention, the median diameter D of the manganese iron phosphate precursor 50 is 0.5 - 10 μm, preferably 0.5 - 5 μm.

[0062] According to the present invention, the size of the primary particles of the manganese iron phosphate precursor is 20 - 200 nm, preferably 20 - 100 nm.

[0063] According to the present invention, the tap density of the iron manganese phosphate precursor is 0.50 to 1.50 g / cm 3 , preferably 0.80 to 1.50 g / cm 3 .

[0064] According to the present invention, the specific surface area of the iron manganese phosphate precursor is 10 to 100 m 2 / g, preferably 10 to 40 m 2 / g.

[0065] In the present invention, the ratio K of the phosphorus content in the iron manganese phosphate precursor to the total molar amount of the metal is 0.95 to 1.10, which is the z value in Formula II.

[0066] According to the present invention, the method for preparing the iron manganese phosphate precursor satisfies the following relationship K = (0.033K1 + 0.5)·L -0.3 ·T 0.2 - 0.05 Formula III Here, K is the ratio of n(P) in the iron manganese phosphate precursor to [n(Mn) + n(Fe) + n(R1)], K1 is the added amount of the phosphorus source in terms of n1(P), and [n1(Mn) + n1(Fe) + n1(R1)] is the molar amount ratio of the total added amounts of the manganese source, the iron source, and the R1 source, L is the pH value of the phosphorus source solution, and T is the temperature of the coprecipitation reaction.

[0067] In the present invention, by controlling the addition molar ratio K1 of the phosphorus source and the metal (manganese source, iron source, and R1 source), the pH of the phosphorus source solution, and the reaction temperature T to satisfy a specific relationship, the adjustment and control of the molar ratio K of phosphorus and metal in the iron manganese phosphate precursor are realized, and further, the adjustment and control of the performance of the lithium iron manganese phosphate cathode material are realized. The obtained lithium iron manganese phosphate cathode material has excellent electrochemical performance.

[0068] According to the present invention, in Formula III, 0.9 ≤ K1 ≤ 2, 0 < L ≤ 3, and 30°C ≤ T ≤ 90°C.

[0069] Furthermore, in Formula III, 1 ≤ K1 ≤ 1.5, 1.5 ≤ L ≤ 2.5, and 60°C ≤ T ≤ 90°C.

[0070] According to the present invention, in step S1, the concentration of the mixed salt is 0.1 to 4 mol / L, preferably 0.2 to 2 mol / L.

[0071] In the present invention, the type of the manganese source in step S1 is not specifically limited, and conventional soluble manganese sources in this field can be used, including divalent manganese salts, but not limited thereto. Preferably, the divalent manganese salt is selected from at least one of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate.

[0072] In the present invention, the type of the iron source in step S1 is not specifically limited, and conventional soluble iron sources in this field can be used, including divalent iron salts, but not limited thereto. Preferably, the divalent iron salt is selected from at least one of ferrous sulfate, ferrous chloride, and ferrous nitrate.

[0073] In the present invention, the types of the R1 source and the R2 source are not specifically limited, and soluble R-containing compounds that can provide at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti in this field can be used, including at least one of R-containing sulfates, nitrates, acetates, and chlorides, but not limited thereto. Preferably, the R source is selected from at least one of titanyl sulfate, zirconium nitrate, and aluminum sulfate.

[0074] In a specific embodiment of the present invention, the types of the R1 source and the R2 source are different. Specifically, the R1 source is selected from soluble R-containing compounds that can provide at least one of Al,, Cu, Zn, Zr, and Ti, and the R2 source is selected from compounds that can provide at least one element of Mg, Ca, Sr,, V, Cr, Co, Ni,, Y, Mo, Nb, B, W, La, and Sm.

[0075] According to the present invention, in step S2, the concentration of the phosphorus source solution is 0.2 to 20 mol / L, preferably 1 to 15 mol / L.

[0076] In the present invention, the type of the phosphorus source in step S2 is not specifically limited, and conventional soluble phosphorus sources in this field can be used. It can include one of phosphoric acid, sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate, but is not limited thereto. Preferably, it is selected from at least one of phosphoric acid, sodium dihydrogen phosphate, and ammonium dihydrogen phosphate.

[0077] In the present invention, in step S2, the pH value of the phosphorus source solution is 0 to 3, and preferably, the pH value of the phosphorus source solution is 1.5 to 2.5.

[0078] In the present invention, the pH adjuster in step S2 is not specifically limited, and it is only necessary to achieve the purpose of adjusting the pH value of the phosphorus source solution. For example, the pH adjuster is an acid solution or an alkaline solution. Preferably, the pH adjuster is selected from at least one of sodium hydroxide, aqueous ammonia, sulfuric acid, hydrochloric acid, and nitric acid. In the present invention, the usage amount of the pH adjuster is not particularly limited either, as long as the pH value of the phosphoric acid solution satisfies the above range.

[0079] According to the present invention, in step S3, the molar ratio of the addition amount of the phosphorus source in terms of n1(P) conversion to the total addition amount of the manganese source, the iron source, and the source in terms of [n1(Mn) + n1(Fe) + n1(R1)] conversion is 1 to 5:1.

[0080] In the present invention, when the total addition amounts of the phosphorus source, the manganese source, the iron source, and the R1 source are controlled to satisfy the above range, the adjustment and control of the P / Me molar ratio in the cathode material can be realized. Furthermore, the adjustment and control of the performance of the lithium manganese iron phosphate cathode material can be realized, and the obtained lithium manganese iron phosphate cathode material has excellent electrochemical performance.

[0081] Furthermore, in step (3), the molar ratio of the addition amount of the phosphorus source in terms of n1(P) to the total addition amount of the manganese source, the iron source, and the R1 source in terms of [n1(Mn) + n1(Fe) + n1(R1)] is 1 to 3:1.

[0082] According to the present invention, in step S3, the molar ratio of the addition amount of the oxidizing agent to the total addition amount of the manganese source, the iron source, and the R1 source in terms of [n1(Mn) + n1(Fe) + n1(R1)] is 1 to 10:1.

[0083] Furthermore, when controlling the total addition amounts of the oxidizing agent, the manganese source, the iron source, and the R1 source to satisfy the above relationship, the oxidation degree of the metal elements in the positive electrode material is controlled, and the obtained lithium manganese iron phosphate positive electrode material has a low volume resistivity and a high purity. When it is used in a lithium ion battery, the lithium ion battery has a high specific capacity, high cycle performance, and high energy density.

[0084] Furthermore, in step S3, the molar ratio of the addition amount of the oxidizing agent to the total addition amount of the manganese source, the iron source, and the R1 source in terms of [n1(Mn) + n1(Fe) + n1(R1)] is 1 to 5:1.

[0085] In the present invention, the type of the oxidizing agent in step S3 is not specifically limited, and conventional oxidizing agents in this field can be used, including ozone, potassium permanganate, sodium persulfate, ammonium persulfate, sodium hypochlorite, sodium perchlorate, etc., but not limited thereto. Preferably, the oxidizing agent is selected from at least one of ozone, potassium permanganate, sodium persulfate, and ammonium persulfate.

[0086] In the present invention, the rate at which the mixed salt solution, the phosphorus source solution, and the oxidizing agent flow in parallel into the reaction kettle during step S3 is not specifically limited, and conventional rates in this field can be used as long as uniform coprecipitation of manganese and iron is achieved.

[0087] According to the present invention, the coprecipitation reaction is carried out under stirring conditions.

[0088] According to the present invention, the rotation speed of the stirring is 200 to 800 r / min, preferably 400 to 800 r / min.

[0089] According to the present invention, an aging reaction is carried out after the coprecipitation reaction.

[0090] According to the present invention, the conditions of the aging reaction include that the aging temperature is 30 to 90 °C and the aging time is 1 to 10 h.

[0091] Furthermore, the conditions of the aging reaction include that the aging temperature is 60 to 90 °C and the aging time is 3 to 6 h.

[0092] According to the present invention, the cleaning agent for cleaning is water at 20 to 90 °C.

[0093] Furthermore, the cleaning agent for cleaning is water at 60 to 90 °C.

[0094] In the present invention, the cleaning agent for cleaning is pure water.

[0095] According to the present invention, the conditions of the drying include that the drying temperature is 50 to 200 °C and the drying time is 2 to 8 h.

[0096] Furthermore, the conditions of the drying include that the drying temperature is 80 to 150 °C and the drying time is 3 to 6 h.

[0097] According to the present invention, in step S4, in the presence of a solvent, the mixing is carried out to obtain a mixed slurry, and after removing the solvent in the mixed slurry, the mixed material is obtained.

[0098] In the present invention, preferably, in the presence of a solvent, by mixing, the manganese iron phosphate precursor, the lithium source, the carbon source and the R2 source can be sufficiently and uniformly mixed, and the obtained lithium manganese iron phosphate cathode material has high purity and low volume resistivity.

[0099] In the present invention, the type of the solvent is not particularly limited as long as the material after mixing forms a uniform slurry. For example, the solvent may be water, ethanol, etc. Preferably, the solvent is water. The amount of the solvent used is not specifically limited either, and similarly, it is based on forming a uniform slurry.

[0100] According to the present invention, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate, lithium dihydrogen phosphate, lithium oxalate, lithium nitrate, and lithium acetate. Preferably, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate, and lithium dihydrogen phosphate.

[0101] According to the present invention, the carbon source is selected from at least one of glucose, sucrose, fructose, cellulose, starch, citric acid, polyacrylic acid, polyethylene glycol, and dopamine. Preferably, the carbon source is selected from at least one of glucose, sucrose, starch, and cellulose.

[0102] In the present invention, the method for removing the solvent in the mixed slurry is not particularly limited, and conventional methods in this field can be adopted. For example, the solvent in the mixed slurry can be removed by direct evaporation. The temperature and process of evaporation can adopt conventional technologies well-known to those skilled in the art. For example, static drying or spray drying can be adopted to remove the solvent in the mixed slurry.

[0103] According to the present invention, in step S5, the firing conditions include that the firing temperature is 500 - 1000 °C and the firing time is 4 - 20 h.

[0104] Furthermore, in step S5, the firing conditions include that the firing temperature is 600 - 800 °C and the firing time is 6 - 12 h.

[0105] In the present invention, the protective atmosphere is selected from a nitrogen gas atmosphere and / or an argon gas atmosphere.

[0106] The third aspect of the present invention provides a lithium iron manganese phosphate cathode material produced by a preparation method.

[0107] The fourth aspect of the present invention provides a manganese iron phosphate precursor, and the precursor material has a structure represented by Formula II, Mn 1-x-y Fe x R1 y P z O4·nH2O Formula II Here, 0.1 ≦ x ≦ 0.5, 0 ≦ y ≦ 0.04, 0.95 ≦ z ≦ 1.10, 0.95 ≦ n ≦ 1.5, and R1 is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti.

[0108] Furthermore, in Formula II, 0.15 ≦ x ≦ 0.45, 0 < y ≦ 0.03, 0.95 ≦ z ≦ 1.05, 0.95 ≦ n ≦ 1.2, and R is selected from at least one of Al, Co, Ni, Mg, Al, W, Nb, Zr, and Ti.

[0109] In the present invention, the relationship between the actual molar content ratio m' of Mn element and Fe element at any position in the manganese iron phosphate precursor and the theoretical molar content ratio m0 of Mn element and Fe element at any position in the lithium iron manganese phosphate precursor is Δm p = |m' - m0| / m0 ≦ 5%.

[0110] Furthermore, Δm p = |m' - m0| / m0 ≦ 3%.

[0111] In the present invention, the median diameter of the manganese iron phosphate precursor is 0.5 to 10 μm, preferably 0.5 to 10 μm.

[0112] In the present invention, the primary particle size of the iron manganese phosphate precursor is 20 to 200 nm, preferably 20 to 100 nm.

[0113] In the present invention, the tap density of the iron manganese phosphate precursor is 0.5 to 1.5 g / cm 3 , preferably 0.8 to 1.5 g / cm 3 .

[0114] In the present invention, the specific surface area of the iron manganese phosphate precursor is 10 to 100 m 2 / g, preferably 10 to 40 m 2 / g.

[0115] A fifth aspect of the present invention provides a method for preparing an iron manganese phosphate precursor, the preparation method comprising: step (1) of mixing a manganese source, an iron source, an R1 source and water to obtain a mixed salt solution; step (2) of mixing a phosphorus source and water, adding a pH adjuster, and obtaining a phosphorus source solution; step (3) of adding the mixed salt solution, the phosphorus source solution and an oxidizing agent to a reaction kettle in parallel flow to perform a coprecipitation reaction, and filtering, washing and drying to obtain the iron manganese phosphate precursor.

[0116] In the present invention, the method for preparing the iron manganese phosphate precursor satisfies the following relationship: K = (0.033K1 + 0.5) · L -0.3 · T 0.2 -0.05 Equation III where K is the ratio of n1(P) to [n1(Mn) + n1(Fe) + n1(R1)] in the iron manganese phosphate precursor, K1 is the molar ratio of the addition amount of the phosphorus source in terms of n1(P) to the total addition amount of the manganese source, the iron source and the R1 source in terms of [n1(Mn) + n1(Fe) + n1(R1)], L is the pH value of the phosphorus source solution, and T is the temperature of the coprecipitation reaction.

[0117] In the present invention, in Equation III, 0.9 ≤ K1 ≤ 2, 0 < L ≤ 3, and 30°C ≤ T ≤ 90°C.

[0118] Furthermore, in Formula III, 1 ≤ K1 ≤ 1.5, 1.5 ≤ L ≤ 2.5, and 60°C ≤ T ≤ 90°C.

[0119] According to the present invention, in step (1), the concentration of the mixed salt is 0.1 to 4 mol / L, preferably 0.2 to 2 mol / L.

[0120] In the present invention, the type of the manganese source in step (1) is not specifically limited, and conventional soluble manganese sources in this field can be used, including divalent manganese salts, but not limited thereto. Preferably, the divalent manganese salt is selected from at least one of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate.

[0121] In the present invention, the type of the iron source in step (1) is not specifically limited, and conventional soluble iron sources in this field can be used, including divalent iron salts, but not limited thereto. Preferably, the divalent iron salt is selected from at least one of ferrous sulfate, ferrous chloride, and ferrous nitrate.

[0122] In the present invention, the type of the R1 source in step (1) is not specifically limited, and conventional soluble R1 sources in this field that can provide M element can be used, including at least one of sulfates, nitrates, acetates, and chlorides containing M, but not limited thereto. Preferably, the R1 source is selected from at least one of titanyl sulfate, zirconium nitrate, and aluminum sulfate.

[0123] In the present invention, in step (2), the concentration of the phosphorus source solution is 0.2 to 20 mol / L, preferably 1 to 15 mol / L.

[0124] In the present invention, the type of phosphorus source in step (2) is not specifically limited, and conventional soluble phosphorus sources in this field can be used. It can include, but is not limited to, one of phosphoric acid, sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate. Preferably, it is selected from at least one of phosphoric acid, sodium dihydrogen phosphate, and ammonium dihydrogen phosphate.

[0125] In the present invention, in step (2), the pH value of the phosphorus source solution is 0 to 3, and preferably, the pH value of the phosphorus source solution is 1.5 to 2.5.

[0126] In the present invention, the pH adjuster in step (2) is not specifically limited, as long as the purpose of adjusting the pH value of the phosphorus source solution can be achieved. For example, the pH adjuster is an acid solution or an alkali solution. Preferably, the pH adjuster is selected from at least one of sodium hydroxide, ammonia water, sulfuric acid, hydrochloric acid, and nitric acid. In the present invention, the usage amount of the pH adjuster is not particularly limited either, as long as the pH value of the phosphoric acid solution satisfies the above range.

[0127] In the present invention, in step (3), the molar ratio of the addition amount of the phosphorus source in terms of n1(P) conversion to the total addition amount of the manganese source, the iron source, and the R1 source in terms of [n1(Mn) + n1(Fe) + n1(R1)] conversion is 1 to 5:1, preferably 1 to 3:1.

[0128] In the present invention, in step (3), the molar ratio of the addition amount of the oxidizing agent to the total addition amount of the manganese source, the iron source, and the R1 source in terms of [n1(Mn) + n1(Fe) + n1(R1)] conversion is 1 to 10:1, preferably 1 to 5:1.

[0129] In the present invention, the type of the oxidizing agent in step (3) is not specifically limited, and conventional oxidizing agents in this field can be used, including ozone, potassium permanganate, sodium persulfate, ammonium persulfate, sodium hypochlorite, and sodium periodate, but is not limited thereto. Preferably, the oxidizing agent is selected from at least one of ozone, potassium permanganate, sodium persulfate, and ammonium persulfate.

[0130] In the present invention, the rate at which the mixed salt solution, phosphorus source solution, and oxidizing agent flow in parallel into the reaction kettle in step (3) is not specifically limited, and conventional rates in this field can be used, as long as uniform coprecipitation of manganese and iron is achieved.

[0131] In the present invention, the coprecipitation reaction is carried out under stirring conditions.

[0132] In the present invention, the rotation speed of the stirring is 200 - 800 r / min, preferably 400 - 800 r / min.

[0133] In the present invention, after the coprecipitation reaction, an aging reaction is carried out.

[0134] In the present invention, the conditions of the aging reaction include an aging temperature of 30 - 90°C and an aging time of 1 - 10 h.

[0135] Furthermore, the conditions of the aging reaction include an aging temperature of 60 - 90°C and an aging time of 3 - 6 h.

[0136] In the present invention, the cleaning agent for washing is water at 20 - 90°C.

[0137] Furthermore, the cleaning agent for washing is water at 60 - 90°C.

[0138] In the present invention, the cleaning agent for washing is pure water.

[0139] In the present invention, the drying conditions include that the drying temperature is 50 to 300 °C and the drying time is 2 to 8 h.

[0140] Furthermore, the drying conditions include that the drying temperature is 80 to 200 °C and the drying time is 3 to 6 h.

[0141] The sixth aspect of the present invention provides an iron manganese phosphate precursor produced by the above preparation method.

[0142] The seventh aspect of the present invention provides a lithium-ion battery including the above lithium iron manganese phosphate cathode material or a cathode material produced by the above iron manganese phosphate precursor.

[0143] Hereinafter, the present invention will be described in detail by way of examples. In the following examples, Particle size test: Measured by testing with a Malvern laser particle size analyzer Mastersizer 2000. Morphology test: Measured by testing with a scanning electron microscope of model S-4800 of Hitachi, Japan.

[0144] m', which is the actual content of Mn element and Fe element at any position in the cathode material precursor, and m'', which is the actual content of Mn element and Fe element at any position in the cathode material, are measured by testing with an EDS of model 50mm of Oxford Power Spectrum Maker. 2 Measured by testing.

[0145] Specific surface area: Measured by testing with a specific surface area tester of model Tristar II 3020 of Micromertics, USA. Tap density: Measured by testing with a tap density tester of model BT-30 of Baxter. Consolidated density: Measured by testing with a consolidated density meter of model MCP-PD51 of Mitsubishi Chemical, Japan. Volume resistivity of the cathode material: Measured by testing with a powder consolidation resistor of model MCP-PD51 of Mitsubishi Chemical, Japan. Carbon content: The carbon content in the cathode material was measured by testing with a CS-i carbon-sulfur analyzer from Eltra, Germany. The content of each element in the cathode material and the precursor was measured by testing with a 5800 ICP-OES spectrometer from Agilent, USA.

[0146] All the raw materials used in the examples and comparative examples are commercially available products.

[0147] Example 1 (1) At a molar ratio of n(Mn):n(Fe):n(Ti) = 65:34:1, a certain mass of manganese sulfate, ferrous sulfate, and titanyl sulfate were weighed and dissolved in deionized water to prepare a 2 mol / L mixed salt solution. (2) A certain mass of sodium dihydrogen phosphate was weighed and dissolved in deionized water, and dilute sulfuric acid with a concentration of 30 wt% was added to adjust the solution pH to 2 to prepare a 2.8 mol / L phosphorus source solution. (3) Equal volumes of the mixed salt solution, the phosphorus source solution, and a sodium persulfate solution (2 mol / L) were added in parallel to a reaction kettle to carry out a coprecipitation reaction. The reaction temperature was 90 °C, the stirring speed was 500 r / min, and the liquid transportation was completed in 3 h. After the liquid transportation was completed, an aging reaction was carried out. The aging temperature was 90 °C, the stirring speed was 500 r / min, and the aging reaction time was 3 h. Here, n(oxidizing agent) / [n1(Mn)+n1(Fe)+n1(M)] = 1, K1 = n1(P) / [n1(Mn)+n1(Fe)+n1(M)] = 1.4. (4) After the reaction was completed, the reaction slurry was filtered and washed with pure water with a volume twice that of the slurry to obtain a cake. The cake was dried at 105 °C for 3 hours to obtain a manganese iron phosphate precursor P1. Here, the composition of the manganese iron phosphate precursor P1 is Mn 0.648 Fe 0.342 Ti 0.01 P 1.04 O4·H2O, the median diameter D 50 is 2.36 μm, the tap density is 0.96 g / cm 3 and the specific surface area is 26.6 m 2 / g. The ratio of manganese, iron, and titanium in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Ti)=64.8:34.2:1, and the molar ratio K of the phosphorus content to the total metal content is set to K=n(P) / [n(Mn)+n(Fe)+n(M)] = 1.04. (5) The prepared manganese iron phosphate precursor, lithium carbonate (Li2CO3), magnesium carbonate, and glucose (in terms of C) were mixed with pure water at a molar ratio of 1:0.52:0.01:0.7, and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry was dried by evaporation in a heating furnace tray, and then placed in a vacuum oven at 85°C for 4 h of drying to obtain a dried material. The dried material was calcined at 650°C for 10 h in a nitrogen gas atmosphere, and after sieving, the lithium manganese iron phosphate cathode material A1 was obtained. The composition of the lithium manganese iron phosphate cathode material A1 is Li 1.04 Mn 0.642 Fe 0.339 Ti 0.01 Mg 0.01 PO4 / C, the average particle size of its primary particles is 80 nm, the tap density is 2.15 g / cm 3 and the specific surface area is 18.6 m 2 / g, and the carbon content is 1.84 wt%.

[0148] Example 2 (1) At a molar ratio of n(Mn):n(Fe):n(Ti)=65:34:1, a certain mass of manganese sulfate, ferrous sulfate, and titanyl sulfate were weighed and dissolved in deionized water to prepare a 1 mol / L mixed salt solution. (2) A certain mass of concentrated phosphoric acid was weighed, deionized water was added for dilution, and sodium hydroxide with a concentration of 40 wt% was added to adjust the solution pH to 1.5 to prepare a 1.3 mol / L phosphorus source solution. (3) Mixing salt solution, phosphorus source solution, and ammonium persulfate solution (1.5 mol / L) with equal volume and add them in parallel flow into the reaction kettle to perform coprecipitation reaction. The reaction temperature is 60 °C, the stirring speed is 500 r / min, and the liquid transportation is completed in 3 h. After the liquid transportation is completed, aging reaction is carried out. The aging temperature is 90 °C, the stirring speed is 500 r / min, and the aging reaction time is 3 h. Let n(oxidant) / [n1(Mn)+n1(Fe)+n1(M)] = 1.5 and K1 = n1(P) / [n1(Mn)+n1(Fe)+n1(M)] = 1.3. (4) After the reaction is completed, filter the reaction slurry and wash it with pure water with a volume twice that of the slurry to obtain a cake. Dry the cake at 105 °C for 3 h to obtain manganese iron phosphate precursor P2. Here, the composition of manganese iron phosphate precursor P2 is Mn 0.652 Fe 0.338 Ti 0.01 P 1.09 O4·H2O, the median diameter D 50 is 1.65 μm, the tap density is 1.14 g / cm 3 and the specific surface area is 26.5 m 2 / g. The ratio of manganese, iron, and titanium in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Ti) = 65.2:33.8:1, and the molar ratio K = n(P) / [n(Mn)+n(Fe)+n(M)] = 1.04 of the phosphorus content to the total metal amount is measured. (5) Mix the prepared manganese iron phosphate precursor, lithium hydroxide, magnesium carbonate, and sucrose (in terms of C) with pure water at a molar ratio of 1:1.03:0.01:0.7, and mix them uniformly by mechanical stirring to obtain a slurry. (6) Dry the slurry in a heating furnace tray by evaporation, and then put it into a vacuum oven at 85 °C for 4 h of drying to obtain a dried material. Bake the dried material at 650 °C for 10 h in a nitrogen gas atmosphere, and after sieving, obtain lithium manganese iron phosphate cathode material A2. The composition of lithium manganese iron phosphate cathode material A2 is Li 1.03 Mn 0.645 Fe 0.335 Ti 0.01 Mg 0.01It is PO4 / C, the average particle size of its primary particles is 60 nm, the bulk density is 2.20 g / cm 3 and the specific surface area is 21.2 m 2 / g, and the carbon content is 2.09 wt%.

[0149] Example 3 (1) At a molar ratio of n(Mn):n(Fe):n(Ti) = 65:34:1, a certain mass of manganese chloride, ferrous sulfate, and titanyl sulfate were weighed and dissolved in deionized water to prepare a 2 mol / L mixed salt solution. (2) A certain mass of ammonium dihydrogen phosphate was weighed and dissolved in deionized water, and dilute sulfuric acid with a concentration of 30 wt% was added to adjust the solution pH to 2.2 to prepare a 3 mol / L phosphorus source solution. (3) Equal volumes of the mixed salt solution, the phosphorus source solution, and a sodium permanganate solution (2 mol / L) were added in parallel to a reaction kettle to conduct a coprecipitation reaction. The reaction temperature was 90 °C, the stirring speed was 500 r / min, and the liquid transportation was completed in 3 h. After the liquid transportation ended, an aging reaction was conducted. The aging temperature was 90 °C, the stirring speed was 500 r / min, and the aging reaction time was 3 h. Here, let n(oxidizing agent) / [n1(Mn)+n1(Fe)+n1(M)] = 1 and K1 = n1(P) / [n1(Mn)+n1(Fe)+n1(M)] = 1.5. (4) After the reaction ended, the reaction slurry was filtered and washed with pure water with a volume twice that of the slurry to obtain a cake. The cake was dried at 105 °C for 3 hours to obtain a manganese iron phosphate precursor P3. Here, the composition of the manganese iron phosphate precursor P3 is Mn 0.647 Fe 0.343 Ti 0.01 P 1.02 O4·H2O, the median diameter D 50 is 3.78 μm, the tap density is 1.02 g / cm 3 and the specific surface area is 22.1 m 2 / g. The ratio of manganese, iron, and titanium in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Ti) = 64.7:34.3:1, and the molar ratio K = n(P) / [n(Mn) + n(Fe) + n(M)] = 1.02 of the phosphorus content to the total metal amount was measured. (5) The prepared manganese iron phosphate precursor, lithium hydroxide, magnesium carbonate, and sucrose (in terms of C) were mixed with pure water at a molar ratio of 1:1.03:0.01:0.7, and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry was dried by evaporation in a heating furnace tray, further dried in a vacuum oven at 85 °C for 4 h to obtain a dried material. The dried material was calcined at 650 °C for 10 h in a nitrogen gas atmosphere, and after sieving, the lithium manganese iron phosphate cathode material A3 was obtained. The composition of the lithium manganese iron phosphate cathode material A3 is Li 1.03 Mn 0.640 Fe 0.340 Ti 0.01 Mg 0.01 PO4 / C, the average particle size of its primary particles is 80 nm, the tap density is 2.19 g / cm 3 and the specific surface area is 18.3 m 2 / g, and the carbon content is 2.08 wt%.

[0150] Example 4 (1) At a molar ratio of n(Mn):n(Fe):n(Ti) = 75:24:1, a certain mass of manganese chloride, iron chloride, and titanyl sulfate were weighed and dissolved in deionized water to prepare a 1.8 mol / L mixed salt solution. (2) A certain mass of sodium dihydrogen phosphate was weighed and dissolved in deionized water, and dilute sulfuric acid with a concentration of 30 wt% was added to adjust the solution pH to 1.8 to prepare a 1.8 mol / L phosphorus source solution. (3) Add the mixed salt solution, phosphorus source solution, and sodium persulfate solution (2.7 mol / L) into the reaction kettle in parallel flow to carry out the coprecipitation reaction. The reaction temperature is 70 °C, the stirring speed is 500 r / min, and the liquid transportation is completed in 3 h. After the liquid transportation is completed, carry out the aging reaction. The aging temperature is 90 °C, the stirring speed is 500 r / min, and the aging reaction time is 3 h. Let n(oxidant) / [n1(Mn) + n1(Fe) + n1(M)] = 1.5 and K1 = n1(P) / [n1(Mn) + n1(Fe) + n1(M)] = 1. (4) After the reaction is completed, filter the reaction slurry and wash it with pure water with a volume twice that of the slurry to obtain a cake. Dry the cake at 105 °C for 3 h to obtain the manganese iron phosphate precursor P4. Here, the composition of the manganese iron phosphate precursor P4 is Mn 0.748 Fe 0.242 Ti 0.01 P 0.99 O4·H2O, the median diameter D 50 is 2.12 μm, the tap density is 0.98 g / cm 3 and the specific surface area is 23.6 m 2 / g. The ratio of manganese, iron, and titanium in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Ti) = 74.8:24.2:1, and the molar ratio K = n(P) / [n(Mn) + n(Fe) + n(M)] = 0.99 of the phosphorus content to the total metal amount was measured. (5) Mix the prepared manganese iron phosphate precursor, lithium hydroxide, magnesium carbonate, and sucrose (in terms of C) with pure water in a molar ratio of 1:1.03:0.01:0.6, and mix them uniformly by mechanical stirring to obtain a slurry. (6) Dry the slurry in a heating furnace tray by evaporation, and then put it into a vacuum oven at 85 °C for 4 h of drying to obtain a dried material. Bake the dried material at 650 °C for 10 h in a nitrogen gas atmosphere, and after sieving, obtain the lithium manganese iron phosphate cathode material A4. The composition of the lithium manganese iron phosphate cathode material A4 is Li 1.03 Mn 0.740 Fe 0.240 Ti 0.01 Mg 0.01It is PO4 / C, the average particle size of its primary particles is 80 nm, the bulk density is 2.26 g / cm 3 and the specific surface area is 18.4 m 2 / g, and the carbon content is 1.94 wt%.

[0151] Example 5 (1) At a molar ratio of n(Mn):n(Fe):n(Al) = 70:29:1, a certain mass of manganese chloride, ferrous sulfate, and aluminum sulfate were weighed and dissolved in deionized water to prepare a 2 mol / L mixed salt solution. (2) A certain mass of sodium hydrogen phosphate was weighed and dissolved in deionized water, and 50 wt% dilute nitric acid was added to make the solution pH 2, preparing a 2 mol / L phosphorus source solution. (3) The mixed salt solution, the phosphorus source solution, and the sodium persulfate solution (1.5 mol / L) were added in parallel to the reaction kettle to carry out a coprecipitation reaction. The reaction temperature was 80 °C, the stirring speed was 500 r / min, and the liquid transportation was completed in 3 h. After the liquid transportation was completed, an aging reaction was carried out. The aging temperature was 90 °C, the stirring speed was 500 r / min, and the aging reaction time was 3 h. Let n(oxidizing agent) / [n1(Mn)+n1(Fe)+n1(M)] = 0.75 and K1 = n1(P) / [n1(Mn)+n1(Fe)+n1(M)] = 1. (4) After the reaction was completed, the reaction slurry was filtered and washed with 2 volumes of pure water of the slurry to obtain a cake. The cake was dried at 105 °C for 3 hours to obtain a manganese iron phosphate precursor P5. Here, the composition of the manganese iron phosphate precursor P5 is Mn 0.703 Fe 0.287 Al 0.01 P 0.99 O4·H2O, the median diameter D 50 is 2.34 μm, the tap density is 1.26 g / cm 3 and the specific surface area is 18.8 m 2 / g. The ratio of manganese, iron, and aluminum in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Al) = 70.3:28.7:1, and the molar ratio of the phosphorus content to the total metal amount K = n(P) / [n(Mn)+n(Fe)+n(M)] = 0.99 was measured. (5) The prepared iron manganese phosphate precursor, lithium hydroxide, niobium pentoxide and cellulose were mixed with pure water in a molar ratio of 1:1.03:0.005:0.7, and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry was dried by evaporation in a heating furnace tray, and then placed in a vacuum oven at 85 °C for 4 h of drying to obtain a dried material. The dried material was calcined at 650 °C for 10 h in a nitrogen gas atmosphere. After sieving, the lithium iron manganese phosphate cathode material A5 was obtained. The composition of the lithium iron manganese phosphate cathode material A5 is Li 1.03 Mn 0.696 Fe 0.284 Al 0.01 Nb 0.01 PO4 / C, the average particle size of its primary particles is 90 nm, the tap density is 2.15 g / cm 3 and the specific surface area is 18.3 m 2 / g, and the carbon content is 1.92 wt%.

[0152] Example 6 (1) In a molar ratio of n(Mn):n(Fe):n(Zr)=70:29:1, a certain mass of manganese chloride, ferrous sulfate, and zirconium nitrate were weighed and dissolved in deionized water to prepare a 2 mol / L mixed salt solution. (2) A certain mass of sodium hydrogen phosphate was weighed and dissolved in deionized water, and dilute nitric acid with a concentration of 50 wt% was added. The solution pH was 1.8, and a 2.2 mol / L phosphorus source solution was prepared. (3) The mixed salt solution, the phosphorus source solution, and the ammonium persulfate solution (1.5 mol / L) were added in parallel to a reaction kettle to carry out a coprecipitation reaction. The reaction temperature was 75 °C, the stirring speed was 500 r / min, and the liquid transportation was completed in 3 h. After the liquid transportation was completed, an aging reaction was carried out. The aging temperature was 90 °C, the stirring speed was 500 r / min, and the aging reaction time was 3 h. Let n(oxidizing agent) / [n1(Mn)+n1(Fe)+n1(M)] = 0.75, K1 = n1(P) / [n1(Mn)+n1(Fe)+n1(M)] = 1.1. (4) After the reaction was completed, the reaction slurry was filtered and washed with pure water having a volume twice that of the slurry to obtain a cake. The cake was dried at 105 °C for 3 hours to obtain a manganese iron phosphate precursor P6. The composition of the manganese iron phosphate precursor P6 is Mn 0.698 Fe 0.292 Zr 0.01 P 1.02 O4·H2O, the median diameter D 50 is 3.08 μm, the tap density is 1.18 g / cm 3 and the specific surface area is 20.6 m 2 / g. The ratio of manganese, iron and aluminum in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Zr)=69.8:29.2:1, and the molar ratio K=n(P) / [n(Mn)+n(Fe)+n(M)]=1.02 of the phosphorus content to the total metal amount was measured. (5) The prepared manganese iron phosphate precursor, lithium hydroxide, tungsten oxide and sucrose (in terms of C) were mixed with pure water at a molar ratio of 1:1.03:0.01:0.7 and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry was evaporated to dryness in a heating furnace tray, and then placed in a vacuum oven at 85 °C and dried for 4 h to obtain a dried material. The dried material was calcined at 650 °C for 10 h in a nitrogen gas atmosphere, and after sieving, a lithium manganese iron phosphate cathode material A7 was obtained. The chemical formula of the lithium manganese iron phosphate cathode material A7 is Li 1.03 Mn 0.691 Fe 0.289 Zr 0.01 W 0.01 PO4 / C, the average particle size of its primary particles is 120 nm, the tap density is 2.23 g / cm 3 and the specific surface area is 15.8 m 2 / g, and the carbon content is 2.10 wt%.

[0153] Example 7 (1) At a molar ratio of n(Mn):n(Fe):n(Ti)=65:34:1, a certain mass of manganese sulfate, ferrous sulfate and titanyl sulfate were weighed and dissolved in deionized water to prepare a 2 mol / L mixed salt solution. (2) Weighed a certain mass of sodium dihydrogen phosphate, dissolved it in deionized water, added dilute sulfuric acid with a concentration of 30 wt% to adjust the solution pH to 2, and prepared a phosphorus source solution with a concentration of 2.5 mol / L. (3) Equal volumes of the mixed salt solution, phosphorus source solution, and sodium persulfate solution (2 mol / L) were added to the reaction kettle in parallel flow to carry out a coprecipitation reaction. The reaction temperature was 90 °C, the stirring speed was 500 r / min, and the liquid transportation was completed in 3 h. After the liquid transportation was completed, an aging reaction was carried out. The aging temperature was 90 °C, the stirring speed was 500 r / min, and the aging reaction time was 3 h. Here, let n(oxidizing agent) / [n1(Mn) + n1(Fe) + n1(M)] = 1 and K1 = n1(P) / [n1(Mn) + n1(Fe) + n1(M)] = 1.25. (4) After the reaction was completed, the reaction slurry was filtered and washed with pure water with a volume twice that of the slurry to obtain a cake. The cake was dried at 105 °C for 3 h to obtain a manganese iron phosphate precursor P7. Here, the composition of the manganese iron phosphate precursor P7 is Mn 0.649 Fe 0.341 Ti 0.01 P 1.03 O4·H2O, the median diameter D 50 is 2.15 μm, the tap density is 0.93 g / cm 3 , and the specific surface area is 28.9 m 2 / g. The ratio of manganese, iron, and titanium in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Ti) = 64.9:34.1:1, and the molar ratio K = n(P) / [n(Mn) + n(Fe) + n(M)] = 1.03 of the phosphorus content to the total metal amount was measured. (5) The manganese iron phosphate precursor prepared above, lithium carbonate (Li2CO3), aluminum oxide, and glucose (in terms of C) were mixed with pure water in a molar ratio of 1:0.52:0.005:0.7, and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry was evaporated to dryness on a heating furnace tray, and then placed in a vacuum oven at 85 °C for 4 h of drying to obtain a dried material. The dried material was calcined at 650 °C for 10 h in a nitrogen gas atmosphere, and after sieving, a lithium manganese iron phosphate cathode material A7 was obtained. The composition of the lithium iron manganese phosphate cathode material A7 is Li 1.04 Mn 0.642 Fe 0.338 Ti 0.01 Al 0.01 PO4 / C. The average particle size of its primary particles is 85 nm, and the tap density is 2.10 g / cm 3 and the specific surface area is 19.7 m 2 / g, and the carbon content is 1.86 wt%.

[0154] Example 8 (1) Weigh a certain mass of manganese sulfate, ferrous sulfate, and titanyl sulfate in a molar ratio of n(Mn):n(Fe):n(Ti)=65:34:1 and dissolve them in deionized water to prepare a 2 mol / L mixed salt solution. (2) Weigh a certain mass of sodium dihydrogen phosphate, dissolve it in deionized water, add dilute sulfuric acid with a concentration of 30 wt% to adjust the solution pH to 2, and prepare a 2.8 mol / L phosphorus source solution. (3) Add equal volumes of the mixed salt solution, the phosphorus source solution, and a sodium persulfate solution (2 mol / L) to the reaction kettle in parallel flow to carry out a coprecipitation reaction. The reaction temperature is 80 °C, the stirring speed is 500 r / min, and the liquid transportation is completed in 3 h. After the liquid transportation is completed, an aging reaction is carried out. The aging temperature is 90 °C, the stirring speed is 500 r / min, and the aging reaction time is 3 h. Here, let n(oxidizing agent) / [n1(Mn)+n1(Fe)+n1(M)] = 1 and K1 = n1(P) / [n1(Mn)+n1(Fe)+n1(M)] = 1.4. (4) After the reaction is completed, filter the reaction slurry and wash it with pure water with a volume twice that of the slurry to obtain a cake. Dry the cake at 105 °C for 3 hours to obtain the lithium iron manganese phosphate precursor P8. Here, the composition of the lithium iron manganese phosphate precursor P8 is Mn 0.651 Fe 0.339 Ti 0.01 P 1.02 O4·H2O, the median diameter D 50 is 2.87 μm, the tap density is 0.99 g / cm 3 and the specific surface area is 22.6 m 2It is / g. The ratio of manganese, iron, and titanium in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Ti)=65.1:33.9:1, and the molar ratio K=n(P) / [n(Mn)+n(Fe)+n(M)] = 1.02 of the phosphorus content to the total metal amount was measured. (5) The prepared manganese iron phosphate precursor, lithium carbonate (Li2CO3), zirconia, and glucose (in terms of C) were mixed with pure water in a molar ratio of 1:0.52:0.01:0.7, and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry was dried by steaming in a heating furnace tray, and further dried in a vacuum oven at 85 °C for 4 h to obtain a dried material. The dried material was calcined at 650 °C for 10 h in a nitrogen gas atmosphere, and after sieving, the lithium manganese iron phosphate cathode material A8 was obtained. The composition of the lithium manganese iron phosphate cathode material A8 is Li 1.04 Mn 0.644 Fe 0.336 Ti 0.01 Zr 0.01 PO4 / C, the average particle size of its primary particles is 70 nm, the tap density is 2.21 g / cm 3 and the specific surface area is 16.8 m 2 / g, and the carbon content is 1.80 wt%.

[0155] Example 9 (1) In a molar ratio of n(Mn):n(Fe):n(Ti)=65:34:1, a certain mass of manganese sulfate and ferrous sulfate were weighed and dissolved in deionized water to prepare a 2 mol / L mixed salt solution. (2) A certain mass of sodium dihydrogen phosphate was weighed and dissolved in deionized water, and dilute sulfuric acid with a concentration of 30 wt% was added to adjust the solution pH to 2 to prepare a 2.8 mol / L phosphorus source solution. (3) A mixed salt solution, a phosphorus source solution, and a sodium persulfate solution (2 mol / L) of equal volume are added to the reaction kettle in parallel flow to carry out a coprecipitation reaction. The reaction temperature is 90 °C, the stirring speed is 500 r / min, and the reaction time is 1 h. Then, an aging reaction is carried out. The aging temperature is 90 °C, the stirring speed is 500 r / min, and the aging reaction time is 3 h. Let n(oxidizing agent) / [n1(Mn)+n1(Fe)+n1(M)] = 1 and K1 = n1(P) / [n1(Mn)+n1(Fe)+n1(M)] = 1.4. (4) After the reaction is completed, the reaction slurry is filtered and washed with pure water of twice the volume of the slurry to obtain a cake. The cake is dried at 105 °C for 3 hours to obtain the manganese iron phosphate precursor P9. Here, the composition of the manganese iron phosphate precursor P9 is Mn 0.647 Fe 0.343 Ti 0.01 P 1.04 O4·H2O, the median diameter D 50 is 2.48 μm, the tap density is 0.97 g / cm 3 , and the specific surface area is 26.2 m 2 / g. The ratio of manganese to iron in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Ti) = 64.7:34.3:1, and the molar ratio K = n(P) / [n(Mn)+n(Fe)+n(M)] = 1.04 of the phosphorus content to the total metal amount was measured. (5) The prepared manganese iron phosphate precursor, lithium carbonate, and glucose (in terms of C) are mixed with pure water at a molar ratio of 1:0.52:0.7 and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry is dried by evaporation in a heating furnace tray, and then placed in a vacuum oven at 85 °C for 4 h of drying to obtain a dried material. The dried material is calcined at 650 °C for 10 h in a nitrogen gas atmosphere, and after sieving, the lithium manganese iron phosphate cathode material A9 is obtained. The composition of the lithium manganese iron phosphate cathode material A9 is Li 1.04 Mn 0.647 Fe 0.343 Ti 0.01 PO4 / C, the average particle size of its primary particles is 90 nm, and the tap density is 2.08 g / cm 3and the specific surface area is 18.8 m 2 / g, and the carbon content is 1.78 wt%.

[0156] Example 10 (1) At a molar ratio of n(Mn):n(Fe) = 65:35, a certain mass of manganese sulfate and ferrous sulfate were weighed and dissolved in deionized water to prepare a 2 mol / L mixed salt solution. (2) A certain mass of sodium dihydrogen phosphate was weighed and dissolved in deionized water, and dilute sulfuric acid with a concentration of 30 wt% was added to adjust the solution pH to 2 to prepare a 2.8 mol / L phosphorus source solution. (3) The mixed salt solution, the phosphorus source solution, and the sodium persulfate solution (2 mol / L) were added in parallel to the reaction kettle to carry out a coprecipitation reaction. The reaction temperature was 90 °C, the stirring speed was 500 r / min, and the liquid transportation was completed in 3 h. After the liquid transportation was completed, an aging reaction was carried out. The aging temperature was 90 °C, the stirring speed was 500 r / min, and the aging reaction time was 3 h. Here, n(oxidizing agent) / [n1(Mn)+n1(Fe)] = 1, K1 = n1(P) / [n1(Mn)+n1(Fe)] = 1.4. (4) After the reaction was completed, the reaction slurry was filtered and washed with pure water with a volume twice that of the slurry to obtain a cake. The cake was dried at 105 °C for 3 hours to obtain the manganese iron phosphate precursor P10. Here, the composition of the manganese iron phosphate precursor P10 is Mn 0.650 Fe 0.348 P 1.04 O4·H2O, the median diameter D 50 is 4.88 μm, the tap density is 0.86 g / cm 3 and the specific surface area is 23.2 m 2 / g. The ratio of manganese to iron in the manganese iron phosphate precursor is n(Mn):n(Fe) = 65.2:34.8, and the molar ratio K = n(P) / [n(Mn)+n(Fe)] = 1.04 of the phosphorus content to the total metal amount was measured. (5) The prepared manganese iron phosphate precursor, lithium carbonate, magnesium carbonate, and glucose (in terms of C) were mixed with pure water at a molar ratio of 1:0.52:0.01:0.7 and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry was dried to dryness on a heating furnace tray, and then placed in a vacuum oven at 85 °C and dried for 4 h to obtain a dried material. The dried material was calcined at 650 °C for 10 h in a nitrogen gas atmosphere. After sieving, lithium iron manganese phosphate cathode material A10 was obtained. The composition of lithium iron manganese phosphate cathode material A10 is Li 1.04 Mn 0.645 Fe 0.345 Mg 0.01 PO4 / C, the average particle size of its primary particles is 250 nm, the tap density is 2.05 g / cm 3 , and the specific surface area is 24.8 m 2 / g, and the carbon content is 1.86 wt%.

[0157] Comparative Example 1 (1) With a molar ratio of n(Mn):n(Fe):n(Ti) = 65:34:1, a certain mass of manganese sulfate, ferrous sulfate, and titanyl sulfate were weighed and dissolved in deionized water to prepare a 2 mol / L mixed salt solution. (2) A certain mass of sodium dihydrogen phosphate was weighed and dissolved in deionized water to prepare a 2.8 mol / L phosphorus source solution. (3) Equal volumes of the mixed salt solution, the phosphorus source solution, and a sodium persulfate solution (2 mol / L) were mixed, and dilute sulfuric acid with a concentration of 30 wt% was added to adjust the solution pH to 2. The mixed solution was directly added to a reaction kettle for a coprecipitation reaction. The reaction temperature was 90 °C, the stirring speed was 500 r / min, and the reaction time was 1 h. Then, an aging reaction was carried out. The aging temperature was 90 °C, the stirring speed was 500 r / min, and the aging reaction time was 3 h. Let n(oxidizing agent) / [n1(Mn)+n1(Fe)+n1(M)] = 1 and K1 = n1(P) / [n1(Mn)+n1(Fe)+n1(M)] = 1.4. (4) After the reaction was completed, the reaction slurry was filtered and washed with pure water with a volume twice that of the slurry to obtain a cake. The cake was dried at 105 °C for 3 h to obtain manganese iron phosphate precursor DP1. The composition of manganese iron phosphate precursor DP1 is Mn 0.602 Fe 0.388 Ti 0.01 P 0.95It is O4·H2O, and the median diameter D 50 is 3.85 μm, the tap density is 0.88 g / cm 3 and the specific surface area is 61.5 m 2 / g. The ratio of manganese, iron, and titanium in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Ti)=60.2:38.8:1, and the molar ratio K=n(P) / [n(Mn)+n(Fe)+n(M)]=0.95 of the phosphorus content to the total metal amount was measured. (5) The prepared manganese iron phosphate precursor, lithium carbonate, magnesium carbonate, and glucose (in terms of C) were mixed with pure water at a molar ratio of 1:0.52:0.01:0.7, and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry was dried by evaporation in a heating furnace tray, and further dried in a vacuum oven at 85 °C for 4 h to obtain a dried material. The dried material was calcined at 650 °C for 10 h in a nitrogen gas atmosphere, and after sieving, a lithium manganese iron phosphate cathode material D1 was obtained. The composition of the lithium manganese iron phosphate cathode material D1 is Li 1.04 Mn 0.596 Fe 0.384 Ti 0.01 Mg 0.01 PO4 / C, the average particle size of its primary particles is 1000 nm, the tap density is 1.85 g / cm 3 and the specific surface area is 36.5 m 2 / g, and the carbon content is 1.75 wt%.

[0158] Comparative Example 2 (1) At a molar ratio of n(Mn):n(Fe):n(Ti)=65:34:1, a certain mass of manganese sulfate, ferrous sulfate, and titanyl sulfate were weighed and dissolved in deionized water to prepare a 2 mol / L mixed salt solution. (2) A certain mass of sodium dihydrogen phosphate was weighed and dissolved in deionized water, and dilute sulfuric acid with a concentration of 30 wt% was added to adjust the solution pH to 2 to prepare a 2.8 mol / L phosphorus source solution. (3) Mix the mixed salt solution and the phosphorus source solution with equal volume, directly add the mixed solution to the reaction kettle, heat and stir the mixed solution. The reaction temperature is 90 °C, the stirring speed is 500 r / min. Add the same volume of sodium persulfate solution (2 mol / L) to the mixed solution, and complete the liquid transportation in 3 h. After the liquid transportation is completed, carry out the aging reaction. The aging temperature is 90 °C, the stirring speed is 500 r / min, and the aging reaction time is 3 h. Here, let n(oxidant) / [n1(Mn)+n1(Fe)+n1(M)] = 1 and K1 = n1(P) / [n1(Mn)+n1(Fe)+n1(M)] = 1.4. (4) After the reaction is completed, filter the reaction slurry, wash it with pure water with a volume twice that of the slurry to obtain a cake. Dry the cake at 105 °C for 3 h to obtain the manganese iron phosphate precursor DP2. The composition of the manganese iron phosphate precursor DP2 is Mn 0.613 Fe 0.377 Ti 0.01 P 0.92 O4·H2O, the median diameter D 50 is 3.65 μm, the tap density is 0.68 g / cm 3 and the specific surface area is 52.5 m 2 / g. The ratio of manganese, iron and titanium in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Ti) = 61.3:37.7:1. The molar ratio K of the phosphorus content to the total metal amount, K = n(P) / [n(Mn)+n(Fe)+n(M)] = 0.92, was measured. (5) Mix the prepared manganese iron phosphate precursor, lithium carbonate, magnesium carbonate and glucose (in terms of C) with pure water in a molar ratio of 1:0.52:0.01:0.7, and mix them uniformly by mechanical stirring to obtain a slurry. (6) Dry the slurry by steaming in a heating furnace tray, and then put it into a vacuum oven at 85 °C for 4 h of drying to obtain a dried material. Bake the dried material at 650 °C for 10 h in a nitrogen gas atmosphere, and after sieving, obtain the lithium manganese iron phosphate cathode material D2. The chemical formula of the lithium manganese iron phosphate cathode material is Li 1.04 Mn 0.607 Fe 0.373 Ti 0.01 Mg0.01 It is PO4 / C, the average particle size of its primary particles is 600 nm, and the consolidated density is 1.77 g / cm 3 and the specific surface area is 32.5 m 2 / g, and the carbon content is 1.18 wt%.

[0159] Comparative Example 3 (1) At a molar ratio of n(Mn):n(Fe):n(Ti) = 65:34:1, a certain mass of manganese sulfate, ferrous sulfate, and titanyl sulfate were weighed and dissolved in deionized water to prepare a 2 mol / L mixed salt solution. (2) A certain mass of sodium dihydrogen phosphate was weighed and dissolved in deionized water, and dilute sulfuric acid with a concentration of 30% was added to adjust the solution pH to 2 to prepare a 2.8 mol / L phosphorus source solution. (3) Equal volumes of the mixed salt solution and the phosphorus source solution were added in parallel flow to the reaction kettle. The reaction temperature was 90 °C, the stirring speed was 500 r / min, and an alkali was added to adjust the pH value. The liquid transportation was completed in 3 h. After the liquid transportation was completed, an aging reaction was carried out. The aging temperature was 90 °C, the stirring speed was 500 r / min, and the aging reaction time was 3 h. Here, let K1 = n1(P) / [n1(Mn)+n1(Fe)+n1(M)] = 1.4. (4) After the reaction was completed, the reaction slurry was filtered and washed with pure water with a volume twice that of the slurry to obtain a cake. The cake was dried at 105 °C for 3 hours to obtain a manganese iron phosphate precursor DP3. The composition of the manganese iron phosphate precursor DP3 is (Mn 0.621 Fe 0.369 Ti 0.01 )3(PO4)2·H2O, the median diameter D 50 is 16.85 μm, the tap density is 0.34 g / cm 3 and the specific surface area is 23.5 m 2 / g. The ratio of manganese, iron, and titanium in the manganese iron phosphate precursor is n(Mn):n(Fe):n(Ti) = 62.1:36.9:1, and the molar ratio of the phosphorus content to the total metal amount K = n(P) / [n(Mn)+n(Fe)+n(M)] = 0.67 was measured. (5) The above-prepared ferrous manganous phosphate precursor, lithium carbonate, lithium dihydrogen phosphate, magnesium carbonate and glucose were mixed with pure water in a molar ratio of 1:0.02:1:0.01:0.7, and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry was dried by steaming in a heating furnace tray, and further dried in a vacuum oven at 85 °C for 4 h to obtain a dried material. The dried material was calcined at 650 °C for 10 h in a nitrogen gas atmosphere. After sieving, the lithium iron manganese phosphate cathode material D3 was obtained. The composition of the lithium iron manganese phosphate cathode material D3 is Li 1.04 Mn 0.615 Fe 0.365 Ti 0.01 Mg 0.01 PO4 / C, the average particle size of its primary particles is 1.2 μm, the tap density is 1.36 g / cm 3 and the specific surface area is 12.8 m 2 / g, and the carbon content is 1.32 wt%.

[0160] Comparative Example 4 (1) Weighed a certain mass of ferrous sulfate and dissolved it in deionized water to prepare a 2 mol / L mixed salt solution. (2) Weighed a certain mass of sodium dihydrogen phosphate and dissolved it in deionized water, added dilute sulfuric acid with a concentration of 30% to adjust the solution pH to 2, and prepared a 2.8 mol / L phosphorus source solution. (3) 1 L of the mixed salt solution, 1 L of the phosphorus source solution and 1 L of the sodium persulfate solution (2 mol / L) were added in parallel to a 5 L reaction kettle for coprecipitation reaction. The reaction temperature was 90 °C, the stirring speed was 500 r / min, and the liquid feeding time was 1 h. After the liquid transportation was completed, an aging reaction was carried out. The aging temperature was 90 °C, the stirring speed was 500 r / min, and the aging reaction time was 3 h. Here, n(oxidizing agent) / n1(Fe)=1, K1=n1(P) / n1(Fe)=1.4. (4) After the reaction was completed, the reaction slurry was filtered and washed with pure water with a volume twice that of the slurry to obtain a cake. The cake was dried at 105 °C for 3 h to obtain the iron phosphate precursor DP4. Here, the composition of the iron phosphate precursor DP4 is FePO4·2H2O, and the median diameter D 50 is 3.78 μm, the tap density is 0.78 g / cm 3 , and the specific surface area is 42.3 m 2 / g. The molar ratio K = n(P) / n(Fe) = 1 of the phosphorus content to the total metal content was measured. (5) The prepared iron phosphate precursor, manganese tetroxide, lithium carbonate, titanium dioxide, and glucose (in terms of C) were mixed with pure water in a molar ratio of 1:0.62:0.52:0.01:0.7, and uniformly mixed by mechanical stirring to obtain a slurry. (6) The slurry was dried by evaporation in a heating furnace tray, and further dried in a vacuum oven at 85 °C for 4 h to obtain a dried material. The dried material was calcined at 650 °C for 10 h in a nitrogen gas atmosphere, and after sieving, the lithium iron manganese phosphate cathode material D4 was obtained. The composition of the lithium iron manganese phosphate cathode material D4 is Li 1.04 Mn 0.643 Fe 0.347 Ti 0.01 PO4 / C, the average particle size of its primary particles is 600 nm, the tap density is 1.65 g / cm 3 , the specific surface area is 32.8 m 2 / g, and the carbon content is 2.46 wt%.

[0161] Any two positions of the prepared lithium iron manganese phosphate precursor were randomly selected, and the actual molar content ratio m' of metals Mn and Fe at each position was tested by EDS, and the measured values are shown in Table 1. The ratio of the theoretical molar content of metals Mn and Fe in the lithium iron manganese phosphate precursor is m.

[0162]

Table 1

[0163] In Comparative Examples 1 to 2, the differences between the molar ratios of Mn and Fe at different positions of the precursors and the theoretical values are large, and the differences in the ratios at different positions are also large. This is because, compared with the preparation process of the precursor in Example 1, in the precursor preparation process of Comparative Example 1, after mixing the mixed salt solution, the phosphorus source solution and the oxidant, the pH is adjusted. Such a one-step raw material addition method makes the reaction non-uniform and prone to the phenomenon of manganese and iron segregation. In Comparative Example 2, after mixing and reacting the mixed salt solution and the phosphorus source solution, the oxidant is added, and some metals and phosphorus have already reacted to form a precipitate, thereby failing to achieve complete oxidation. At the same time, it affects the uniform distribution of manganese and iron. In Comparative Example 3, no oxidant is added at all, and iron manganous phosphate is formed, where the deviation of the contents of metal and phosphorus is large.

[0164] Median diameter D of the iron manganous phosphate precursor prepared in the examples and comparative examples 50 The tap density and specific surface area were tested, and the results are shown in Table 2.

[0165]

Table 2

[0166] The compositions of the iron manganous phosphate precursor and the lithium iron manganous phosphate cathode material prepared in the examples and comparative examples are shown in Table 3.

[0167]

Table 3

[0168] Any two positions of the above-prepared lithium iron manganous phosphate cathode material were randomly selected, and the ratio m'' of the actual molar contents of metals Mn and Fe at each position was tested by EDS. The measured values are shown in Table 4. The ratio of the theoretical molar contents of metals Mn and Fe in the lithium iron manganous phosphate cathode material is m.

[0169]

Table 4

[0170] The average particle size, tap density, specific surface area, carbon content, and volume resistivity of the primary particles in the lithium iron manganese phosphate cathode materials prepared in the examples and comparative examples were tested, and the results are shown in Table 5.

[0171]

Table 5

[0172] As can be seen from Tables 1 to 5, compared with Comparative Examples 1 to 4, in Examples 1 to 10, the difference between the molar ratio of Mn and Fe at different positions in the cathode material and its precursor and the theoretical value is small, the distribution of iron and manganese in the cathode material and its precursor is uniform, there is no segregation phenomenon, and the cathode material prepared thereby has a low volume resistivity and small primary particles. When it is used in a lithium-ion battery, the electrochemical performance of the lithium-ion battery can be significantly improved.

[0173] Specifically, since the difference between the molar ratio of Mn and Fe at different positions in the cathode material precursors of Comparative Examples 1 to 2 and the theoretical value is large, the difference between the molar ratio of Mn and Fe at different positions in the cathode materials of Comparative Examples 1 to 2 and the theoretical value becomes large, and the difference in the ratio of different positions is also large. At the same time, the segregation distribution of the precursor manganese iron in Comparative Example 1 is non-uniform, and the oxidation reaction of the precursor in Comparative Example 2 is incomplete, so there are hetero-phases. In the cathode materials of Comparative Examples 1 to 2, the primary particles are large and the volume resistivity is large. In Comparative Example 3, it is necessary to supplement the phosphorus source in the stage of preparing the cathode material, and the distribution of the ratio of its metal to phosphorus is non-uniform and difficult to control, and its volume resistivity becomes large. In Comparative Example 4, by mixing iron phosphate and manganese trioxide, atomic-level mixing of elements cannot be achieved, and there is also a large deviation in the molar ratio of Mn and Fe.

[0174] Test Example

[0175] This test example is used to explain the electrode material, electrode, lithium-ion battery, and its preparation method. (1) Preparation of the positive electrode sheet: The lithium iron manganese phosphate positive electrode material, the conductive agent carbon nanotube, and the NMP solution of the binder PVDF prepared in the above examples and comparative examples are mixed at a mass ratio of 90:5:5. The specific method is as follows. The dried positive electrode material and the conductive agent are ground in a mortar for 15 minutes. After uniform grinding, the PVDF solution (mass fraction 5%) is added at a ratio, and stirred with a magnetic stirrer for 6 hours. The obtained paste-like slurry is uniformly coated on the current collector aluminum foil. Then, after drying in a vacuum drying oven at 60 °C for 20 hours, it is punched into a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm under a pressure of 100 MPa, and the positive electrode sheet is placed in a vacuum drying oven at 120 °C and dried for 12 h. (2) Assembly of the battery: Using a metallic lithium sheet with a diameter of 17 mm and a thickness of 1 mm as the negative electrode, a polyethylene porous film with a thickness of 25 μm coated with an alumina ceramic layer on the surface as the separator, and an equal-volume mixture of 1 mol / L LiPF6, ethylene carbonate (EC) and diethyl carbonate (DEC) as the electrolyte, the positive electrode sheet, the separator, the negative electrode sheet and the electrolyte are assembled into a 2025-type buckle battery in an Ar gas glove box with both the water content and the oxygen content less than 5 ppm. (3) Electrochemical performance test: The battery is subjected to a charge-discharge test using a Blue Power LAND CT2001A charge-discharge tester from Wuhan Lanbo Electronics Co., Ltd. The voltage range of charge-discharge is 2.5~4.4V. The specific capacity test is carried out on the lithium-ion batteries assembled at the rates of 0.1C and 1C respectively, and the cycle performance test is carried out at a rate of 1C. The test results are shown in Table 6.

[0176]

Table 6

[0177] From Table 6, it is recognized that the positive electrode material prepared in the present invention has good capacity performance, rate performance, and cycle stability. This is because the distribution of the precursor manganese iron prepared in the present invention is uniform, the ratio of metal to phosphorus can be adjusted and controlled, and the uniformity of the doping element is improved by precursor doping. The positive electrode material prepared using the precursor of the present invention as a raw material has characteristics such as small primary particles, uniform carbon coating, and low volume resistivity, which are advantageous for the insertion and extraction of lithium ions. As a result, the discharge specific capacity at 0.1C is greater than 150 mAh / g, the discharge specific capacity at 1C is greater than 140 mAh / g, and the double doping of the precursor and the positive electrode material ensures that its 80-cycle retention rate is greater than 95%.

[0178] Figure 1 is an XRD diagram of the manganese iron phosphate precursor prepared in Example 1. As can be seen from Figure 1, the XRD of the manganese iron phosphate precursor prepared in the present invention completely corresponds to the MnPO4·H2O standard card, indicating that no phase separation or generation of other impurities has occurred.

[0179] Figure 2 is an SEM diagram of the manganese iron phosphate precursor prepared in Example 1. As can be seen from Figure 2, the primary particles of the manganese iron phosphate precursor prepared in the present invention are small, which is advantageous for the uniform mixing of the lithium source and the carbon source when it is used for the preparation of the lithium manganese iron phosphate positive electrode material, and the carbon source can uniformly coat the surface of the positive electrode material.

[0180] Figure 3 is an EDS distribution diagram of Mn and Fe in the cross-section of the manganese iron phosphate precursor prepared in Example 1. As can be seen from Figure 3, the distribution of manganese and iron in the manganese iron phosphate precursor prepared in the present invention is uniform.

[0181] Figure 4 is an XRD diagram of the lithium manganese iron phosphate positive electrode material prepared in Example 1. As can be seen from Figure 4, the XRD of the lithium manganese iron phosphate positive electrode material prepared in the present invention completely corresponds to the standard card, no phase separation is formed in manganese and iron, and no generation of other impurities has occurred.

[0182] Figure 5 is an SEM image of the lithium iron manganese phosphate cathode material prepared in Example 1. As can be seen from Figure 5, the primary particles of the lithium iron manganese phosphate cathode material are small and uniform, and there is no carbon aggregation on the surface, indicating that the surface of the cathode material is uniformly coated with carbon.

Claims

1. A lithium manganese iron phosphate cathode material, wherein the lithium manganese iron phosphate cathode material has a structure represented by Formula I, Li ｄ Mn １－ａ－ｂ－ｃ Fe ａ R ｂ PO ４ / C formula I where 0.1 ≤ a ≤ 0.5, 0 ≤ b ≤ 0.08, 0.9 < d ≤ 1.2, and R is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti, The volume resistivity of the positive electrode material is 10 to 10 ４ Ω·cm, and The relationship between the actual molar content ratio m'' of Mn element and Fe element at any position in the cathode material and the theoretical molar content ratio m of Mn element and Fe element at any position in the cathode material is Δm ｃ The lithium iron manganese phosphate cathode material is characterized in that Δm = |m'' - m| / m ≤ 5%.

2. 0.15 ≤ a ≤ 0.45, 0 < b ≤ 0.06, 0.95 < d ≤ 1.15, Preferably, R is selected from at least one of Al, Co, Ni, Mg, Al, W, Nb, Zr, and Ti, Preferably, the volume resistivity of the positive electrode material is 10 to 10 ３ Ω·cm, and more preferably, the volume resistivity of the positive electrode material is 10 to 500 Ω·cm, Preferably, based on the total weight of the lithium manganese iron phosphate cathode material, the carbon content is 0.5 to 5 wt%, preferably 1 to 3 wt%. The lithium manganese iron phosphate cathode material according to Claim 1.

3. Δm ｃ The lithium iron manganese phosphate cathode material according to claim 1 or 2, wherein Δm ｃ = |m'' - m| / m ≤ 3%.

4. The tap density of the positive electrode material is 1.5 to 3.5 g / cm ３ and preferably 2 to 3 g / cm ３ and Preferably, the specific surface area of the positive electrode material is 10 to 60 m ２ / g, preferably 10 to 25 m ２ / g, and Preferably, the lithium manganese iron phosphate cathode material has a secondary particle structure formed by primary particles, Preferably, the average particle size of the cathode material is 1 to 50 μm, preferably 7 to 15 μm, Preferably, the average particle size of the primary particles is 10 to 500 nm, preferably 10 to 200 nm. The lithium manganese iron phosphate cathode material according to any one of Claims 1 to 3.

5. A method for preparing a lithium manganese iron phosphate cathode material, the preparation method comprising: S1, mixing a manganese source, an iron source, an R1 source, and water to obtain a mixed salt solution; S2, mixing a phosphorus source and water, adding a pH adjuster, and obtaining a phosphorus source solution; S3, adding the mixed salt solution, the phosphorus source solution, and an oxidizing agent in parallel to a reaction kettle to perform a coprecipitation reaction, filtering, washing, and drying to obtain the lithium manganese iron phosphate precursor; S4, mixing the lithium manganese iron phosphate precursor, a lithium source, a carbon source, and an R2 source to obtain a mixture; S5, firing the mixture in the presence of a protective atmosphere to obtain the lithium manganese iron phosphate cathode material. Preferably, the lithium manganese iron phosphate precursor has a structure represented by Formula II. Mn １－ｘ－ｙ Fe ｘ R1 ｙ P ｚ O ４ ·nH ２ O Formula II Here, 0.1 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.04, 0.95 ≤ z ≤ 1.10, 0.95 ≤ n ≤ 1.5, R1 is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti, Preferably, the lithium iron manganese phosphate cathode material has the configuration described in Formula I, Li ｄ Mn １－ａ－ｂ－ｃ Fe ａ R ｂ PO ４ PO ４ / C type I Here, 0.1 ≤ a ≤ 0.5, 0 ≤ b ≤ 0.08, 0.9 < d ≤ 1.2, R is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti, and a method for preparing a lithium iron manganese phosphate cathode material is characterized by this.

6. The actual molar content ratio m' of Mn element and Fe element at any position in the manganese iron phosphate precursor and the theoretical molar content ratio m of Mn element and Fe element at any position in the lithium manganese iron phosphate precursor ０ The relationship with is Δm ｐ = |m' - m ０ | / m ０ ≦ 5% is satisfied, preferably, Δm ｐ = |m' - m ０ | / m ０ ≦ 3% is satisfied, Preferably, the median diameter of the iron manganese phosphate precursor is 0.5 to 10 μm, preferably 0.5 to 5 μm, Preferably, the primary particle size of the iron manganese phosphate precursor is 20 to 200 nm, preferably 20 to 100 nm, Preferably, the tap density of the iron manganese phosphate precursor is 0.50 to 1.50 g / cm ３ , preferably 0.80 to 1.50 g / cm ３ and Preferably, the specific surface area of the iron manganese phosphate precursor is 10 to 100 m ２ / g, preferably 10 to 40 m ２ / g. The preparation method according to claim 5.

7. The method for preparing the iron manganese phosphate precursor satisfies the following relationship, K = (0.033K １ + 0.5) · L －０．３ · T ０．２ - 0.05 Formula III Here, K is the ratio of n(P) to [n(Mn) + n(Fe) + n(M)] in the manganese iron phosphate precursor, and K １ is the molar amount ratio of the addition amount of the phosphorus source in terms of n1(P) to the total addition amount of the manganese source, the iron source, and the R1 source in terms of [n1(Mn) + n1(Fe) + n1(M)], L is the pH value of the phosphorus source solution, T is the temperature of the coprecipitation reaction, Preferably, 0.9 ≤ K １ ≤ 2, 0 < L ≤ 3, 30°C ≤ T ≤ 90°C, and Preferably, 1 ≦ K １ ≦ 1.5, 1.5 ≦ L ≦ 2.5, 60°C ≦ T ≦ 90°C, the preparation method according to claim 5 or 6.

8. The R1 source and the R2 source are each independently selected from compounds that can provide at least one element of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti, Preferably, the lithium source is selected from at least one of lithium hydroxide, lithium carbonate, lithium dihydrogen phosphate, lithium oxalate, lithium nitrate, and lithium acetate, Preferably, the carbon source is selected from at least one of glucose, sucrose, fructose, cellulose, starch, citric acid, polyacrylic acid, polyethylene glycol, and dopamine, and the preparation method according to any one of Claims 5 to 7.

9. In step S1, the concentration of the mixed salt is 0.1 to 4 mol / L, preferably 0.2 to 2 mol / L, Preferably, in step S2, the concentration of the phosphorus source solution is 0.2 to 20 mol / L, preferably 1 to 15 mol / L, Preferably, in step S3, the molar ratio of the addition amount of the phosphorus source in terms of n1(P) to the total addition amount of the manganese source, the iron source, and the R1 source in terms of [n1(Mn) + n1(Fe) + n1(R1)] is 1 to 5:1, preferably 1 to 3:1, Preferably, in step S3, the molar ratio of the addition amount of the oxidizing agent to the total addition amount of the manganese source, the iron source, and the R1 source in terms of [n1(Mn) + n1(Fe) + n1(R1)] is 1 to 10:1, preferably 1 to 5:

1. The preparation method according to any one of claims 5 to 8.

10. Perform the coprecipitation reaction under stirring conditions, Preferably, the rotation speed of the stirring is 200 to 800 r / min, preferably 400 to 800 r / min, Preferably, after the coprecipitation reaction, an aging reaction is performed, Preferably, the conditions of the aging reaction include an aging temperature of 30 to 90 °C and an aging time of 1 to 10 h, Preferably, the cleaning agent for cleaning is water at 20 to 90 °C, Preferably, the conditions of the drying include a drying temperature of 50 to 200 °C and a drying time of 2 to 8 h, Preferably, in step S4, the mixing is performed in the presence of a solvent to obtain a mixed slurry, and after removing the solvent in the mixed slurry, the mixed material is obtained, Preferably, in step S5, the conditions of the firing include a firing temperature of 500 to 1000 °C and a firing time of 4 to 20 h. The preparation method according to any one of claims 5 to 9.

11. A lithium manganese iron phosphate cathode material prepared by the preparation method according to any one of claims 5 to 10.

12. A manganese iron phosphate precursor, wherein the precursor material has a structure represented by formula II, Mn １－ｘ－ｙ Fe ｘ R1 ｙ P ｚ O ４ ·nH ２ O of formula II, where 0.1 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.04, 0.95 ≤ z ≤ 1.10, 0.95 ≤ n ≤ 1.5, and R1 is selected from at least one of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, Al, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti. Preferably, the actual molar content ratio m' of the Mn element and the Fe element at any position in the iron manganese phosphate precursor and the theoretical molar content ratio m of the Mn element and the Fe element at any position in the lithium iron manganese phosphate precursor ０ The relationship with is Δm ｐ = |m' - m ０ | / m ０ ≤ 5% is satisfied, Preferably, the median diameter of the manganese iron phosphate precursor is 0.5 to 10 μm, preferably 0.5 to 5 μm, Preferably, the primary particle size of the manganese iron phosphate precursor is 20 to 200 nm, preferably 20 to 100 nm, Preferably, the tap density of the iron manganese phosphate precursor is 0.50 to 1.50 g / cm ３ , preferably 0.80 to 1.50 g / cm ３ and Preferably, the specific surface area of the iron manganese phosphate precursor is 10 to 100 m ２ / g, preferably 10 to 40 m ２ / g, and the iron manganese phosphate precursor is characterized by this.

13. A method for preparing a manganese iron phosphate precursor, wherein the preparation method includes: Step (1) of mixing a manganese source, an iron source, an R1 source, and water to obtain a mixed salt solution; Step (2) of mixing a phosphorus source and water, adding a pH adjuster, and obtaining a phosphorus source solution; Step (3) of adding the mixed salt solution, the phosphorus source solution, and an oxidizing agent to a reaction kettle in parallel flow to perform a coprecipitation reaction, followed by filtration, washing, and drying to obtain the manganese iron phosphate precursor. Preferably, the method for preparing the manganese iron phosphate precursor satisfies the following relationship, K = (0.033K １ + 0.5) · L －０．３ · T ０．２ - 0.05 Formula III Here, K is the ratio of n(P) to [n(Mn) + n(Fe) + n(R1)] in the manganese iron phosphate precursor, and K １ is the molar amount ratio of the addition amount of the phosphorus source in terms of n1(P) to the total addition amount of the manganese source, the iron source, and the R1 source in terms of [n1(Mn) + n1(Fe) + n1(R1)], L is the pH value of the phosphorus source solution, T is the temperature of the coprecipitation reaction, Preferably, 0.9 ≦ K １ ≦ 2, 0 < L ≦ 3, 30°C ≦ T ≦ 90°C, and a method for preparing a manganese iron phosphate precursor, characterized in that.

14. A manganese iron phosphate precursor prepared by the preparation method according to claim 13.

15. A lithium-ion battery comprising a lithium iron manganese phosphate cathode material according to any one of claims 1 to 4 and 11, or a cathode material prepared from a lithium iron manganese phosphate precursor according to claim 12 or 14.

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