Lithium manganese phosphate positive electrode material and preparation method thereof, ferromanganese phosphate precursor and preparation method thereof, lithium ion battery

Abstract

The present invention relates to the technical field of the preparation of lithium-ion cathode materials, and discloses a lithium iron manganese phosphate cathode material, a preparation method thereof, a lithium iron manganese phosphate precursor and a preparation method thereof, and a lithium-ion battery. The cathode material has a composition shown in Formula I: Li d Mn 1‑a‑b Fe a R b PO4 / C Formula I; wherein, 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, W, La, Sm, Co, Ni, Cu, Zn, Zr and Ti; the volume resistivity of the cathode material is 10-10 4 Ω·cm. The cathode material contains specific doping elements, and the cathode material has a low volume resistivity. When it is used to prepare a lithium-ion battery, the electrochemical performance of the lithium-ion battery is effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion positive electrode material preparation, and in particular to a lithium iron manganese phosphate positive electrode material and a preparation method thereof, a manganese iron phosphate precursor and a preparation method thereof, and a lithium ion battery. 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, electric vehicles such as EV and PHEV, and energy storage systems. As a lithium-ion battery positive electrode material, lithium iron phosphate has the characteristics of good safety, good stability and low cost, which has continuously increased its market share. However, the shortcomings of lithium iron phosphate, such as poor electronic conductivity, small lithium ion diffusion coefficient and low energy density, have limited its further development and application in the field of electric vehicles. As an upgraded product of lithium iron phosphate, lithium iron manganese phosphate has the same specific capacity as lithium iron phosphate (theoretical capacity is 170mAh / g), but the introduction of manganese gives it a higher redox potential, thereby increasing the energy density of the material.

[0003] At present, the synthesis methods of lithium manganese iron phosphate mainly include high-temperature solid phase method, hydrothermal method and co-precipitation method. Among them, the high-temperature solid phase method has a simple process flow and is suitable for industrial production, but it is difficult to achieve uniform mixing of manganese and iron at the atomic level, poor consistency, and uneven particle morphology, which affects the compaction density and discharge capacity. The main advantages of the co-precipitation method are uniform particle composition, adjustable size structure, simple operation and industrial production. The preparation of manganese iron phosphate precursor is the key to synthesizing high-performance materials.

[0004] At present, people have conducted extensive research on ferromanganese phosphate precursors. CN114057177A discloses a ferromanganese phosphate and a preparation method thereof. A divalent manganese salt and a divalent iron salt are dissolved in water to obtain a mixed salt solution of manganese salt and iron salt; a phosphorus source is added to the mixed salt solution to obtain a precursor solution; an alkali co-precipitation is added to the precursor solution to obtain a ferromanganese phosphate slurry, wherein the ferromanganese phosphate slurry contains ferrous phosphate precipitation and ferromanganese phosphate precipitation; the ferromanganese phosphate slurry is washed, filtered, and dried to obtain ferromanganese phosphate. The sample prepared by this method has phase separation of ferrous phosphate and manganese phosphate, resulting in an inhomogeneous structure; due to the large deviation in the ratio of metal to phosphorus, a phosphorus source needs to be supplemented in the process of preparing the positive electrode material, and it is not easy to regulate the ratio of metal to phosphorus, which limits the performance of the positive electrode material.

[0005] CN107697899A discloses a preparation method of manganese iron phosphate. First, divalent manganese iron precipitation is carried out under alkaline conditions, then an oxidant is added to oxidize divalent manganese iron to trivalent manganese iron, and subsequently a phosphorus source is added for phosphate conversion. This preparation method has a complex process, involves too many phase transformations between substances, is prone to defects, and it is difficult to control indicators such as the particle size and morphology of the precursor. Summary of 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 manganese iron phosphate cathode material, its preparation method, a manganese iron phosphate precursor and its preparation method, and a lithium ion battery. The lithium manganese iron phosphate cathode material contains specific doping elements, has high purity, and the cathode material has a low volume resistivity. When it is used to prepare 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.

[0007] To achieve the above object, the first aspect of the present invention provides a lithium manganese iron phosphate cathode material, and the cathode material has a composition shown in Formula I:

[0008] Li d Mn 1-a-b Fe a R b PO4 / C Formula I;

[0009] Wherein, 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, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti;

[0010] The volume resistivity of the cathode material is 10-10 4 Ω·cm;

[0011] 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 satisfy the following relationship:

[0012] Δm c = |m'' - m| / m ≤ 5%.

[0013] The second aspect of the present invention provides a preparation method of a lithium manganese iron phosphate cathode material, and the preparation method includes the following steps:

[0014] S1. Mix a manganese source, an iron source, an R1 source with water to obtain a mixed salt solution;

[0015] S2, mixing a phosphorus source with water, and adding a pH adjuster to obtain a phosphorus source solution;

[0016] S3, adding the mixed salt solution, the phosphorus source solution and the oxidant into the reactor in a parallel flow form to carry out a coprecipitation reaction, and obtaining the ferromanganese phosphate precursor by filtering, washing and drying;

[0017] S4, mixing the ferromanganese phosphate precursor, lithium source, carbon source and R2 source to obtain a mixture;

[0018] S5. In the presence of a protective atmosphere, calcining the mixture to obtain the lithium manganese iron phosphate positive electrode material.

[0019] The third aspect of the present invention provides a lithium manganese iron phosphate positive electrode material prepared by the above preparation method.

[0020] A fourth aspect of the present invention provides a ferromanganese phosphate precursor material, wherein the precursor material has a composition shown in Formula II:

[0021] Mn 1-x-y Fe x R1 y P z O4·nH2O formula II,

[0022] Among them, 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, W, La, Sm, Co, Ni, Cu, Zn, Zr and Ti.

[0023] A fifth aspect of the present invention provides a method for preparing a ferromanganese phosphate precursor, the preparation method comprising the following steps:

[0024] The ferromanganese phosphate precursor is prepared according to the following steps:

[0025] (1) mixing a manganese source, an iron source, an R1 source and water to obtain a mixed salt solution;

[0026] (2) mixing a phosphorus source with water and adding a pH adjuster to obtain a phosphorus source solution;

[0027] (3) Adding the mixed salt solution, the phosphorus source solution and the oxidant into a reactor in parallel to carry out a co-precipitation reaction, and obtaining the ferromanganese phosphate precursor through filtering, washing and drying.

[0028] A sixth aspect of the present invention provides a ferromanganese phosphate precursor prepared by the above preparation method.

[0029] A seventh aspect of the present invention provides a lithium-ion battery, which includes the above-mentioned lithium iron manganese phosphate positive electrode material or a positive electrode material made from the above-mentioned lithium iron manganese phosphate precursor.

[0030] Through the above technical scheme, the lithium iron manganese phosphate positive electrode material and its preparation method, the iron manganese phosphate precursor and its preparation method, and the lithium ion battery provided by the present invention achieve the following beneficial effects:

[0031] 1. The lithium manganese iron phosphate positive electrode material provided by the present invention contains specific doping elements, and the positive electrode material has a low volume resistivity and high purity, which effectively avoids the generation of impurities. When it is used to prepare a lithium ion battery, the electrochemical properties of the lithium ion battery are effectively improved. Specifically, the lithium ion battery has a high specific capacity, a high cycle performance and a high energy density.

[0032] Furthermore, the manganese and iron elements in the lithium manganese iron phosphate positive electrode material provided by the present invention are evenly distributed, and the primary particles are small, the carbon coating is uniform, and the compaction density is high, which can further improve the electrochemical performance of the lithium ion battery.

[0033] 2. In the preparation method of the lithium iron manganese phosphate positive electrode material provided by the present invention, a precursor with a specific composition is mixed with a lithium source, a carbon source and an R2 source and then calcined to obtain the material, wherein the precursor contains a special doping element R1, and the doping element can enter the metal site to form nanoparticles with a stable structure, thereby making the prepared lithium iron manganese phosphate positive electrode material have high purity and low volume resistivity.

[0034] Further, in the present invention, manganese source, iron source, R1 source, phosphorus source and oxidant are used as raw materials, and in particular, a mixed salt solution containing manganese source, iron source, R1 source, phosphorus source solution and oxidant are added to the reactor in a parallel flow form, so that after the metal ions react with the oxidant and oxidize, they quickly combine with phosphate to form a precipitate, which can effectively avoid the disproportionation reaction of trivalent manganese ions in the aqueous solution, and realize oxidation and precipitation; at the same time, the parallel flow into the liquid can avoid the phenomenon of metal segregation caused by the excessive ion concentration in the solution, and achieve uniform co-precipitation of manganese and iron. And the metal stoichiometric ratio in the obtained ferromanganese phosphate precursor is stable; the molar ratio of phosphorus to metal P / Me is adjustable; the primary particles are small, the secondary particles are uniform, and the morphology is adjustable; the structure is stable; the synthesis process is simple, environmentally friendly and pollution-free, and suitable for industrial production.

[0035] Furthermore, by controlling the specific relationship between the molar ratio K1 of the added amount of phosphorus source and metal (manganese source, iron source and R1 source), the pH of the phosphorus source solution and the reaction temperature T, the molar ratio K of phosphorus to metal in the ferromanganese phosphate precursor is regulated, thereby achieving the regulation of the performance of the lithium iron manganese phosphate positive electrode material, so that the prepared lithium iron manganese phosphate positive electrode material has excellent electrochemical properties.

[0036] The preparation method of the lithium iron manganese phosphate positive electrode material provided by the present invention is non-toxic and harmless, has a simple process, readily available raw materials, low equipment requirements, is easy to promote and apply, and can be widely used in the industrial production of lithium iron manganese phosphate positive electrode materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is the XRD pattern of the ferromanganese phosphate precursor prepared in Example 1 of the present invention;

[0038] Figure 2 This is a SEM image of the ferromanganese phosphate precursor prepared in Example 1 of the present invention;

[0039] Figure 3 This is the EDS distribution diagram of Mn and Fe elements in the cross section of the ferromanganese phosphate precursor prepared in Example 1 of the present invention;

[0040] Figure 4 This is the XRD diagram of the lithium manganese iron phosphate positive electrode material prepared in Example 1 of the present invention;

[0041] Figure 5 This is a SEM image of the lithium manganese iron phosphate positive electrode material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0042] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0043] The first aspect of the present invention provides a lithium iron manganese phosphate positive electrode material, wherein the positive electrode material has a composition shown in Formula I:

[0044] Li d Mn 1-a-b Fe a R b PO4 / C formula I;

[0045] Among them, 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, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti;

[0046] The volume resistivity of the positive electrode material is 10-10 4 Ω·cm;

[0047] The actual molar content ratio m'' of Mn element and Fe element at any position in the positive electrode material and the theoretical molar content ratio m of Mn element and Fe element at any position in the positive electrode material satisfy the following relationship:

[0048] Δm c =︱m'' - m︱ / m ≤ 5%.

[0049] In the present invention, the lithium iron manganese phosphate positive electrode material contains specific doping elements, and the positive electrode material has a low volume resistivity, and the positive electrode material has a high purity, and the manganese and iron elements in the lithium iron manganese phosphate positive electrode material are evenly distributed, effectively avoiding the generation of impurity phases. Specifically, the actual content ratio of metal Mn element and Fe element at any position is relatively close to the theoretical content ratio, indicating that the manganese and iron elements in the lithium iron manganese phosphate positive electrode material are evenly distributed and no segregation phenomenon occurs. When it is used to prepare 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.

[0050] In the present invention, the actual content m'' of Mn element and Fe element at any position in the positive electrode material is measured by the EDS method.

[0051] In the present invention, the theoretical content molar content ratio m of Mn element and Fe element at any position in the positive electrode material = (1 - a - b - c) / a.

[0052] In the present invention, when testing the actual content w'' of Mn element and Fe element, the area of the selected position accounts for 1 - 30% of the area of the selected positive electrode material particles. In the present invention, when ensuring that the area of the selected position for testing the actual content m'' of Mn element and Fe element satisfies the above range, it can not only ensure the feasibility of the test, but also effectively avoid the averaging effect, so as to better characterize the uniformity of the distribution of Mn element and Fe element.

[0053] Further, in formula I, 0.15 ≤ a ≤ 0.45, 0 < b ≤ 6, 0.95 < d ≤ 1.15.

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

[0055] In a specific embodiment of the present invention, the lithium iron manganese phosphate cathode material contains two or more different kinds of elements R. Specifically, the lithium iron manganese phosphate cathode material has the composition shown in Formula II:

[0056] Li d Mn 1-a-b-c Fe a R’ b R’’ c PO4 / C Formula II;

[0057] Wherein, 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; R’’ is selected from at least one of Mg, Ca, Sr, V, Cr, Co, Ni, Y, Mo, Nb, B, W, La, and Sm.

[0058] 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.

[0059] In a specific embodiment of the present invention, in Formula II, R’ is selected from at least one of Al, Zr, and Ti; R’’ is selected from at least one of Co, Ni, Mg, Y, La, W, and Nb.

[0060] Further, the volume resistivity of the cathode material is 10-10 3 Ω·cm.

[0061] Furthermore, the volume resistivity of the cathode material is 10-500 Ω·cm.

[0062] According to the present invention, based on the total weight of the lithium iron manganese phosphate cathode material, the carbon content is 0.5-5 wt%.

[0063] In the present invention, when the carbon content in the lithium iron manganese phosphate cathode material satisfies the above range, the cathode material can have good electronic conductivity, thereby improving the specific capacity, cycle performance, and rate performance of the lithium ion battery prepared from the cathode material.

[0064] Further, based on the total weight of the lithium iron manganese phosphate cathode material, the carbon content is 1-3 wt%.

[0065] Further, Δm c =︱m''-m︱ / m ≤ 3%.

[0066] According to the present invention, the tap density of the cathode material is 1.5-3.5 g / cm3 , preferably 2-3g / cm 3 .

[0067] According to the present invention, the specific surface area of ​​the positive electrode material is 10-60m 2 / g, preferably 10-25m 2 / g.

[0068] According to the present invention, the lithium iron manganese phosphate positive electrode material has a secondary particle structure formed by primary particles.

[0069] According to the present invention, the average particle size of the positive electrode material is 1-50 μm, preferably 7-15 μm.

[0070] According to the present invention, the average particle size of the primary particles is 10-500 nm.

[0071] In the present invention, the positive electrode material has a small primary particle size, which shortens the lithium ion diffusion path and improves the ion conductivity of the positive electrode material. When used in a lithium ion battery, it can effectively improve the electrochemical performance of the lithium ion battery.

[0072] Furthermore, the average particle size of the primary particles is 10-200 nm.

[0073] A second aspect of the present invention provides a method for preparing a lithium manganese iron phosphate positive electrode material, the preparation method comprising the following steps:

[0074] S1, mixing a manganese source, an iron source, an R1 source and water to obtain a mixed salt solution;

[0075] S2, mixing a phosphorus source with water, and adding a pH adjuster to obtain a phosphorus source solution;

[0076] S3, adding the mixed salt solution, the phosphorus source solution and the oxidant into the reactor in a parallel flow form to carry out a coprecipitation reaction, and obtaining the ferromanganese phosphate precursor by filtering, washing and drying;

[0077] S4, mixing the ferromanganese phosphate precursor, lithium source, carbon source and R2 source to obtain a mixture;

[0078] S5. In the presence of a protective atmosphere, calcining the mixture to obtain the lithium manganese iron phosphate positive electrode material.

[0079] In the present invention, R1 and R2 are only used to distinguish the different timings of adding the R source, and do not limit the element type of the R source. Both the R1 source and the R2 source are used to introduce the R source into the positive electrode material.

[0080] In the present invention, a precursor with a specific composition is mixed with a lithium source, a carbon source and an R2 source and then calcined to obtain a material. The precursor contains a special doping element R1, which can enter the metal site to form nanoparticles with a stable structure, thereby making the prepared lithium iron manganese phosphate positive electrode material have high purity and low volume resistivity. When the prepared lithium iron manganese phosphate positive electrode material is used in a lithium ion battery, the electrochemical properties of the lithium ion battery can be effectively improved, specifically, the lithium ion battery has a high specific capacity, a high cycle performance and a high energy density.

[0081] In the present invention, manganese source, iron source, R1 source, phosphorus source and oxidant are used as raw materials. In particular, a mixed salt solution containing manganese source, iron source and R1 source, a phosphorus source solution and an oxidant are added to a reactor in a parallel flow form, so that after the metal ions react and oxidize with the oxidant, they quickly combine with phosphate to form a precipitate, which can effectively avoid the disproportionation reaction of trivalent manganese ions in an aqueous solution, and achieve oxidation and precipitation; at the same time, the parallel flow into the liquid can avoid the phenomenon of metal segregation caused by the excessively high ion concentration in the solution, and achieve uniform coprecipitation of manganese and iron. And the metal stoichiometric ratio in the obtained ferromanganese phosphate precursor is stable; the molar ratio P / Me of phosphorus to metal is adjustable; the primary particles are small, the secondary particles are uniform, and the morphology is adjustable; the structure is stable; the synthesis process is simple, environmentally friendly and pollution-free, and suitable for industrial production.

[0082] According to the present invention, the ferromanganese phosphate precursor has a composition shown in Formula II:

[0083] Mn 1-x-y Fe x R1 y P z O4·nH2O Formula II,

[0084] Among them, 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, W, La, Sm, Co, Ni, Cu, Zn, Zr and Ti.

[0085] 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, W, Nb, Zr and Ti.

[0086] According to the present invention, the lithium manganese iron phosphate positive electrode material has a composition as described in Formula I:

[0087] Li d Mn 1-a-b Fea R b PO4 / C of formula I;

[0088] 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, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti.

[0089] Further, in formula I, 0.15 ≤ a ≤ 0.45, 0 < b ≤ 0.06, 0.95 < d ≤ 1.15.

[0090] Further, in formula I, R is selected from at least one of Al, Co, Ni, Mg, W, Nb, Zr, and Ti.

[0091] According to the present invention, the following relationship is satisfied 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 manganese iron phosphate precursor:

[0092] Δm p = |m' - m0| / m0 ≤ 5%.

[0093] 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 and the theoretical content ratio 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 evenly distributed and no segregation phenomenon occurs. When this precursor is used to prepare the cathode material, it can make the manganese, iron, and phosphorus elements in the cathode material achieve uniform distribution, avoid the segregation of elements in the cathode material, and significantly improve the capacity performance and cycle performance of the lithium ion battery containing this lithium manganese iron phosphate cathode material.

[0094] 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 = (1 - x - y) / x.

[0095] In the present invention, the actual content m' of Mn element and Fe element at any position in the precursor is measured by the EDS method.

[0096] 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 ensuring that the area of the selected position for testing the actual content m' of Mn element and Fe element satisfies the above range, it can not only ensure the feasibility of the test, but also effectively avoid the averaging effect, so as to better characterize the uniformity of the distribution of Mn element and Fe element.

[0097] Furthermore, Δm p =︱m'-m0︱ / m0≤3%.

[0098] According to the present invention, the median particle size D of the ferromanganese phosphate precursor is 50 It is 0.5-10 μm, preferably 0.5-5 μm.

[0099] According to the present invention, the primary particle size of the ferromanganese phosphate precursor is 20-200 nm, preferably 20-100 nm.

[0100] According to the present invention, the tap density of the ferromanganese phosphate precursor is 0.50-1.50 g / cm 3 , preferably 0.80-1.50g / cm 3 .

[0101] According to the present invention, the specific surface area of ​​the ferromanganese phosphate precursor is 10-100m 2 / g, preferably 10-40m 2 / g.

[0102] In the present invention, the ratio of phosphorus content to total metal molar amount in the ferromanganese phosphate precursor is K=0.95-1.10, which is the z value in Formula II.

[0103] According to the present invention, the method for preparing the ferromanganese phosphate precursor satisfies the following relationship:

[0104] K = (0.033K1 + 0.5) L -0.3 ·T 0.2 -0.05 Formula III;

[0105] Wherein, K is the ratio of n(P) to [n(Mn)+n(Fe)+n(R1)] in the manganese ferrophosphate precursor; K1 is the molar ratio of the added amount of the phosphorus source measured in n1(P) to the total added amount of the manganese source, the iron source and the R1 source measured in [n1(Mn)+n1(Fe)+n1(R1)]; L is the pH value of the phosphorus source solution; T is the temperature of the coprecipitation reaction.

[0106] In the present invention, by controlling the molar ratio K1 of the added amount of phosphorus source and 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 molar ratio K of phosphorus to metal in the ferromanganese phosphate precursor is regulated, and then the performance of the lithium iron manganese phosphate positive electrode material is regulated, so that the prepared lithium iron manganese phosphate positive electrode material has excellent electrochemical properties.

[0107] According to the present invention, in formula III, 0.9≤K1≤2, 0<L≤3, 30℃≤T≤90℃.

[0108] Furthermore, in Formula III, 1≤K1≤1.5, 1.5≤L≤2.5, 60°C≤T≤90°C.

[0109] According to the present invention, in step S1, the concentration of the mixed salt is 0.1-4 mol / L, preferably 0.2-2 mol / L.

[0110] In the present invention, there is no specific limitation on the type of manganese source in step S1, and conventional soluble manganese sources in the art may be used, including but not limited to divalent manganese salts. Preferably, the divalent manganese salt is selected from at least one of manganese sulfate, manganese chloride, manganese nitrate and manganese acetate.

[0111] In the present invention, the type of the iron source in step S1 is not specifically limited, and conventional soluble iron sources in the art can be used, including but not limited to ferrous iron salts. Preferably, the ferrous iron salt is selected from at least one of ferrous sulfate, ferrous chloride and ferrous nitrate.

[0112] In the present invention, there is no specific limitation on the types of R1 source and R2 source. Conventional soluble R-containing compounds in the art 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 can be used, including but not limited to at least one of R-containing sulfates, nitrates, acetates and chlorides. Preferably, the R source is selected from at least one of titanyl sulfate, zirconium nitrate and aluminum sulfate.

[0113] In a specific embodiment of the present invention, the types of R1 source and R2 source are different. Specifically, the R1 source is selected from a soluble R-containing compound that can provide at least one of Al, Cu, Zn, Zr and Ti; the R2 source is selected from a compound that can provide at least one element among Mg, Ca, Sr, V, Cr, Co, Ni, Y, Mo, Nb, B, W, La and Sm.

[0114] According to the present invention, in step S2, the concentration of the phosphorus source solution is 0.2-20 mol / L, preferably 1-15 mol / L.

[0115] In the present invention, the type of phosphorus source in step S2 is not specifically limited, and a conventional soluble phosphorus source in the art can be used, including but not limited to one of phosphoric acid, sodium phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate and ammonium monohydrogen phosphate, preferably at least one selected from phosphoric acid, sodium dihydrogen phosphate and ammonium dihydrogen phosphate.

[0116] In the present invention, in step S2, the pH value of the phosphorus source solution is 0-3, preferably, the pH value of the phosphorus source solution is 1.5-2.5.

[0117] In the present invention, the type of pH adjuster in step S2 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 alkaline 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 amount of the pH adjuster is not particularly limited, as long as the pH value of the phosphoric acid solution can meet the above range.

[0118] According to the present invention, in step S3, the molar ratio of the added amount of the phosphorus source measured in n1(P) to the total added amount of the manganese source, the iron source and the sources measured in [n1(Mn)+n1(Fe)+n1(R1)] is 1-5:1.

[0119] In the present invention, by controlling the total addition amount of the phosphorus source, the manganese source, the iron source and the R1 source to meet the above range, the molar ratio of P / Me in the positive electrode material can be controlled, thereby achieving the regulation of the performance of the lithium iron manganese phosphate positive electrode material, so that the prepared lithium iron manganese phosphate positive electrode material has excellent electrochemical properties.

[0120] Furthermore, in step (3), the molar ratio of the added amount of the phosphorus source, measured as n1(P), to the total added amount of the manganese source, the iron source and the R1 source, measured as [n1(Mn)+n1(Fe)+n1(R1)], is 1-3:1.

[0121] According to the present invention, in step S3, the ratio of the amount of the oxidant added to the molar amount of the total amount of the manganese source, the iron source and the R1 source added calculated as [n1(Mn)+n1(Fe)+n1(R1)] is 1-10:1.

[0122] Furthermore, when the total amount of the oxidant added and the manganese source, the iron source and the R1 source is controlled to satisfy the above relationship, the degree of oxidation of the metal elements in the positive electrode material can be controlled, so that the prepared lithium manganese iron phosphate positive electrode material has a low volume resistivity and high purity. When it is used in lithium-ion batteries, the lithium-ion batteries can have high specific capacity, high cycle performance and high energy density.

[0123] Furthermore, in step S3, the molar ratio of the added amount of the oxidant to the total added amount of the manganese source, the iron source and the R1 source calculated as [n1(Mn)+n1(Fe)+n1(R1)] is 1-5:1.

[0124] In the present invention, the type of the oxidant in step S3 is not specifically limited, and conventional oxidants in the art can be used, including but not limited to ozone, potassium permanganate, sodium persulfate, ammonium persulfate, sodium hypochlorite, and sodium ferrate. Preferably, the oxidant is selected from at least one of ozone, potassium permanganate, sodium persulfate, and ammonium persulfate.

[0125] In the present invention, the speed at which the mixed salt solution, phosphorus source solution and oxidant flow into the reactor in step S3 is not specifically limited, and the conventional speed in the art can be used as long as ferromanganese can be uniformly co-precipitated.

[0126] According to the present invention, the coprecipitation reaction is carried out under stirring conditions.

[0127] According to the present invention, the stirring speed is 200-800 r / min, preferably 400-800 r / min.

[0128] According to the present invention, an aging reaction is performed after the coprecipitation reaction.

[0129] According to 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.

[0130] Furthermore, the conditions of the aging reaction include: an aging temperature of 60-90° C. and an aging time of 3-6 h.

[0131] According to the present invention, the washing detergent is water at 20-90°C.

[0132] Furthermore, the washing detergent is water at 60-90°C.

[0133] In the present invention, the detergent used for washing is pure water.

[0134] According to the present invention, the drying conditions include: a drying temperature of 50-200° C. and a drying time of 2-8 hours.

[0135] Furthermore, the drying conditions include: drying temperature of 80-150° C. and drying time of 3-6 hours.

[0136] According to the present invention, in step S4, the mixing is performed in the presence of a solvent to obtain a mixed slurry, and the mixed material is obtained after removing the solvent from the mixed slurry.

[0137] In the present invention, preferably, mixing is carried out in the presence of a solvent so that the manganese iron phosphate precursor, lithium source, carbon source and R2 source are fully and evenly mixed, so that the prepared manganese iron phosphate lithium positive electrode material has a higher purity and a low volume resistivity.

[0138] In the present invention, there is no particular limitation on the type of solvent, as long as the mixed materials can form a uniform slurry. For example, the solvent can be water, ethanol, etc. Preferably, the solvent is water. There is no specific limitation on the amount of the solvent, which is also based on the ability to form a uniform slurry.

[0139] 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.

[0140] 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.

[0141] In the present invention, there is no particular limitation on the method for removing the solvent from the mixed slurry, and conventional methods in the art may be used. For example, the solvent in the mixed slurry may be removed by direct evaporation, and the evaporation temperature and process may adopt existing technologies known to those skilled in the art. For example, static drying or spray drying may be used to remove the solvent from the mixed slurry.

[0142] According to the present invention, in step S5, the calcination conditions include: a calcination temperature of 500-1000° C. and a calcination time of 4-20 hours.

[0143] Furthermore, in step S5, the calcination conditions include: a calcination temperature of 600-800° C. and a calcination time of 6-12 hours.

[0144] In the present invention, the protective atmosphere is selected from nitrogen atmosphere and / or argon atmosphere.

[0145] A third aspect of the present invention provides a lithium manganese iron phosphate positive electrode material obtained by the preparation method.

[0146] A fourth aspect of the present invention provides a ferromanganese phosphate precursor, wherein the precursor material has a composition shown in Formula II:

[0147] Mn 1-x-y Fe x R1 y P z O4·nH2O formula II,

[0148] Among them, 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.

[0149] 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.

[0150] In the present invention, 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 manganese iron phosphate lithium precursor satisfy the following relationship:

[0151] Δm p =︱m'-m0︱ / m0≤5%.

[0152] Furthermore, Δm p =︱m'-m0︱ / m0≤3%.

[0153] In the present invention, the median particle size of the ferromanganese phosphate precursor is 0.5-10 μm, preferably 0.5-10 μm.

[0154] In the present invention, the primary particle size of the ferromanganese phosphate precursor is 20-200 nm, preferably 20-100 nm.

[0155] In the present invention, the tap density of the ferromanganese phosphate precursor is 0.5-1.5 g / cm 3 , preferably 0.8-1.5g / cm 3 .

[0156] In the present invention, the specific surface area of ​​the ferromanganese phosphate precursor is 10-100m 2 / g, preferably 10-40m 2 / g.

[0157] A fifth aspect of the present invention provides a method for preparing a ferromanganese phosphate precursor, the preparation method comprising the following steps:

[0158] The ferromanganese phosphate precursor is prepared according to the following steps:

[0159] (1) mixing a manganese source, an iron source, an R1 source and water to obtain a mixed salt solution;

[0160] (2) mixing a phosphorus source with water and adding a pH adjuster to obtain a phosphorus source solution;

[0161] (3) Adding the mixed salt solution, the phosphorus source solution and the oxidant into a reactor in parallel to carry out a co-precipitation reaction, and obtaining the ferromanganese phosphate precursor through filtering, washing and drying.

[0162] In the present invention, the method for preparing the ferromanganese phosphate precursor satisfies the following relationship:

[0163] K = (0.033K1 + 0.5) L -0.3 ·T 0.2 -0.05 Formula III;

[0164] Wherein, K is the ratio of n1(P) to [n1(Mn)+n1(Fe)+n1(R1)] in the manganese ferrophosphate precursor; K1 is the molar ratio of the amount of the phosphorus source added in terms of n1(P) to the total amount of the manganese source, the iron source and the R1 source added 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.

[0165] In the present invention, in formula III, 0.9≤K1≤2, 0<L≤3, 30℃≤T≤90℃.

[0166] Furthermore, in Formula III, 1≤K1≤1.5, 1.5≤L≤2.5, 60°C≤T≤90°C.

[0167] According to the present invention, in step (1), the concentration of the mixed salt is 0.1-4 mol / L, preferably 0.2-2 mol / L.

[0168] In the present invention, the type of manganese source in step (1) is not specifically limited, and conventional soluble manganese sources in the art can be used, including but not limited to divalent manganese salts. Preferably, the divalent manganese salt is selected from at least one of manganese sulfate, manganese chloride, manganese nitrate and manganese acetate.

[0169] In the present invention, the type of the iron source in step (1) is not specifically limited, and conventional soluble iron sources in the art can be used, including but not limited to ferrous iron salts. Preferably, the ferrous iron salt is selected from at least one of ferrous sulfate, ferrous chloride and ferrous nitrate.

[0170] In the present invention, there is no specific limitation on the type of the R1 source in step (1). A conventional soluble R1 source capable of providing the M element in the art can be used, including but not limited to at least one of sulfates, nitrates, acetates and chlorides containing M. Preferably, the R1 source is selected from at least one of titanyl sulfate, zirconium nitrate and aluminum sulfate.

[0171] In the present invention, in step (2), the concentration of the phosphorus source solution is 0.2-20 mol / L, preferably 1-15 mol / L.

[0172] In the present invention, the type of phosphorus source in step (2) is not specifically limited, and conventional soluble phosphorus sources in the art can be used, including but not limited to one of phosphoric acid, sodium phosphate, sodium dihydrogen phosphate, sodium monohydrogen phosphate, ammonium dihydrogen phosphate and ammonium monohydrogen phosphate, preferably at least one of phosphoric acid, sodium dihydrogen phosphate and ammonium dihydrogen phosphate.

[0173] In the present invention, in step (2), the pH value of the phosphorus source solution is 0-3, preferably, the pH value of the phosphorus source solution is 1.5-2.5.

[0174] In the present invention, the type of 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 alkaline 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 amount of the pH adjuster is not particularly limited, as long as the pH value of the phosphoric acid solution can meet the above range.

[0175] In the present invention, in step (3), the molar ratio of the added amount of the phosphorus source, measured as n1(P), to the total added amount of the manganese source, the iron source and the R1 source, measured as [n1(Mn)+n1(Fe)+n1(R1)], is 1-5:1, preferably 1-3:1.

[0176] In the present invention, in step (3), the ratio of the amount of the oxidant added to the total amount of the manganese source, the iron source and the R1 source added in terms of molar amount [n1(Mn)+n1(Fe)+n1(R1)] is 1-10:1, preferably 1-5:1.

[0177] In the present invention, the type of the oxidant in step (3) is not specifically limited, and conventional oxidants in the art may be used, including but not limited to ozone, potassium permanganate, sodium persulfate, ammonium persulfate, sodium hypochlorite, and sodium ferrate. Preferably, the oxidant is selected from at least one of ozone, potassium permanganate, sodium persulfate, and ammonium persulfate.

[0178] In the present invention, the speed at which the mixed salt solution, phosphorus source solution and oxidant flow into the reactor in step (3) is not specifically limited, and a conventional speed in the art can be used as long as ferromanganese can be uniformly co-precipitated.

[0179] In the present invention, the coprecipitation reaction is carried out under stirring conditions.

[0180] In the present invention, the stirring speed is 200-800 r / min, preferably 400-800 r / min.

[0181] In the present invention, an aging reaction is performed after the coprecipitation reaction.

[0182] 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.

[0183] Furthermore, the conditions of the aging reaction include: an aging temperature of 60-90° C. and an aging time of 3-6 h.

[0184] In the present invention, the washing detergent is water at 20-90°C.

[0185] Furthermore, the washing detergent is water at 60-90°C.

[0186] In the present invention, the detergent used for washing is pure water.

[0187] In the present invention, the drying conditions include: drying temperature of 50-300° C., and drying time of 2-8 hours.

[0188] Furthermore, the drying conditions include: a drying temperature of 80-200° C. and a drying time of 3-6 hours.

[0189] A sixth aspect of the present invention provides a ferromanganese phosphate precursor prepared by the above preparation method.

[0190] A seventh aspect of the present invention provides a lithium-ion battery, which includes the above-mentioned lithium iron manganese phosphate positive electrode material or a positive electrode material made from the above-mentioned lithium iron manganese phosphate precursor.

Claims

1. A lithium manganese iron phosphate positive electrode material, characterized in that: The positive electrode material has a composition shown in Formula I: Li d Mn 1-a-b Fe a R b PO4 / C of 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, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti; The volume resistivity of the positive electrode material is 10-10 4 Ω·cm; The actual molar content ratio m'' of Mn element and Fe element at any position in the positive electrode material satisfies the following relationship with the theoretical molar content ratio m of Mn element and Fe element at any position in the positive electrode material: Δm c =︱m''-m︱ / m≤5%。 2. The lithium iron manganese phosphate positive electrode material according to claim 1, wherein 0.15 ≤ a ≤ 0.45, 0 < b ≤ 0.06, 0.95 < d ≤ 1.15; and / or, R is selected from at least one of Al, Co, Ni, Mg, W, Nb, Zr, and Ti; And / or, the volume resistivity of the positive electrode material is 10-10 3 Ω·cm; and / or, based on the total weight of the lithium iron manganese phosphate positive electrode material, the carbon content is 0.5 - 5 wt%; 3. The lithium iron manganese phosphate positive electrode material according to claim 1, wherein The volume resistivity of the positive electrode material is 10 - 500 Ω·cm; and / or, based on the total weight of the lithium iron manganese phosphate positive electrode material, the carbon content is 1 - 3 wt%; 4. The lithium iron manganese phosphate positive electrode material according to any one of claims 1 to 3, wherein: Δm c =︱m''-m︱ / m≤3%。 5. The lithium iron manganese phosphate positive electrode material according to any one of claims 1 to 3, wherein: The compaction density of the positive electrode material is 1.5-3.5 g / cm 3 ; And / or, the specific surface area of ​​the positive electrode material is 10-60m 2 / g.

6. The lithium iron manganese phosphate positive electrode material according to any one of claims 1 to 3, wherein: The compaction density of the positive electrode material is 2-3 g / cm 3 ; And / or, the specific surface area of ​​the positive electrode material is 10-25m 2 / g.

7. The lithium iron manganese phosphate positive electrode material according to any one of claims 1 to 3, wherein: The lithium iron manganese phosphate positive electrode material has a secondary particle structure formed by primary particles; and / or, the average particle size of the positive electrode material is 1 - 50 μm; and / or, the average particle size of the primary particles is 10 - 500 nm.

8. The lithium iron manganese phosphate positive electrode material according to claim 7, wherein: The average particle size of the positive electrode material is 7 - 15 μm; and / or, the average particle size of the primary particles is 10 - 200 nm.

9. A method for preparing a lithium manganese iron phosphate positive electrode material, characterized in that: The preparation method includes the following steps: S1. Mix a manganese source, an iron source, an R1 source with water to obtain a mixed salt solution; S2. Mix a phosphorus source with water, add a pH regulator to obtain a phosphorus source solution; S3. Add the mixed salt solution, the phosphorus source solution, and an oxidant into a reaction kettle in a co - current manner to carry out a coprecipitation reaction, and obtain a lithium iron manganese phosphate precursor through filtration, washing, and drying; S4. Mix the lithium iron manganese phosphate precursor, a lithium source, a carbon source, and an R2 source to obtain a mixture; S5. Calcinate the mixture in the presence of a protective atmosphere to obtain the lithium iron manganese phosphate positive electrode material; wherein, the lithium iron manganese phosphate precursor has a composition shown in Formula II: Mn 1-x-y Fe x R1 y P z O4·nH2O formula II, wherein 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, W, La, Sm, Co, Ni, Cu, Zn, Zr and Ti; The preparation method of the lithium iron manganese phosphate precursor satisfies the following relationship: K = (0.033K1 + 0.5) L -0.3 ·T 0.2 -0.05 Formula III; where K is the ratio of n(P) to [n(Mn)+n(Fe)+n(R1)] in the lithium 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; T is the temperature of the coprecipitation reaction; The R1 source and the R2 source are each independently selected from compounds capable of providing at least one element of Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti.

10. The preparation method according to claim 9, wherein: The lithium iron manganese phosphate positive electrode material has a composition shown in Formula I: Li d Mn 1-a-b Fe a R b PO4 / C of formula I; Among them, 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, W, La, Sm, Co, Ni, Cu, Zn, Zr, and Ti.

11. The preparation method according to claim 9 or 10, wherein: The actual molar content ratio m' of Mn element and Fe element at any position in the manganese iron phosphate precursor satisfies the following relationship with the theoretical molar content ratio m0 of Mn element and Fe element at any position in the manganese iron phosphate precursor: Δm p =︱m'-m0︱ / m0≤5%; and / or, the median particle size of the manganese iron phosphate precursor is 0.5 - 10 μm; and / or, the primary particle size of the manganese iron phosphate precursor is 20 - 200 nm; And / or, the tap density of the ferromanganese phosphate precursor is 0.50-1.50 g / cm 3 ; And / or, the specific surface area of ​​the ferromanganese phosphate precursor is 10-100m 2 / g.

12. The preparation method according to claim 9 or 10, wherein: The actual molar content ratio m' of Mn element and Fe element at any position in the manganese iron phosphate precursor satisfies the following relationship with the theoretical molar content ratio m0 of Mn element and Fe element at any position in the manganese iron phosphate precursor: Δm p =︱m'-m0︱ / m0≤3%; and / or, the median particle size of the manganese iron phosphate precursor is 0.5 - 5 μm; and / or, the primary particle size of the manganese iron phosphate precursor is 20 - 100 nm; And / or, the tap density of the ferromanganese phosphate precursor is 0.80-1.50 g / cm 3 ; And / or, the specific surface area of ​​the ferromanganese phosphate precursor is 10-40m 2 / g.

13. The preparation method according to claim 9 or 10, wherein: 0.9 ≤ K1 ≤ 2, 0 < L ≤ 3, 30°C ≤ T ≤ 90°C.

14. The preparation method according to claim 13, wherein: 1 ≤ K1 ≤ 1.5, 1.5 ≤ L ≤ 2.5, 60°C ≤ T ≤ 90°C.

15. The preparation method according to claim 9 or 10, wherein: The lithium source is selected from at least one of lithium hydroxide, lithium carbonate, lithium dihydrogen phosphate, lithium oxalate, lithium nitrate, and lithium acetate; and / or, the carbon source is selected from at least one of glucose, sucrose, fructose, cellulose, starch, citric acid, polyacrylic acid, polyethylene glycol, and dopamine.

16. The preparation method according to claim 9 or 10, wherein: In step S1, the concentration of the mixed salt is 0.1 - 4 mol / L; and / or, in step S2, the concentration of the phosphorus source solution is 0.2 - 20 mol / L; and / or, 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 - 5:1; and / or, in step S3, the molar ratio of the addition amount of the oxidant 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 - 10:

1.

17. The preparation method according to claim 9 or 10, wherein: In step S1, the concentration of the mixed salt is 0.2 - 2 mol / L; and / or, in step S2, the concentration of the phosphorus source solution is 1 - 15 mol / L; and / or, 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 - 3:1; and / or, in step S3, the molar ratio of the addition amount of the oxidant 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 - 5:

1.

18. The preparation method according to claim 9 or 10, wherein: Under stirring conditions, the coprecipitation reaction is carried out.

19. The preparation method according to claim 18, wherein: The rotation speed of the stirring is 200 - 800 r / min.

20. The preparation method according to claim 19, wherein: The stirring speed is 400-800r / min.

21. The preparation method according to claim 9 or 10, wherein: After the coprecipitation reaction, an aging reaction is performed.

22. The preparation method according to claim 21, wherein The conditions of the aging reaction include: an aging temperature of 30-90° C. and an aging time of 1-10 h.

23. The preparation method according to claim 9 or 10, wherein: The washing detergent is water at 20-90°C; And / or, the drying conditions include: drying temperature of 50-200° C., drying time of 2-8 h; And / or, in step S4, the mixing is performed in the presence of a solvent to obtain a mixed slurry, and the solvent in the mixed slurry is removed to obtain the mixed material; And / or, in step S5, the calcination conditions include: a calcination temperature of 500-1000° C. and a calcination time of 4-20 h.

24. Lithium manganese iron phosphate positive electrode material prepared by the preparation method according to any one of claims 9 to 23.

25. A ferromanganese phosphate precursor, characterized in that: The precursor material has a composition shown in Formula II: Mn 1-x-y Fe x R1 y P z O4·nH2O formula II, wherein 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, W, La, Sm, Co, Ni, Cu, Zn, Zr and Ti; The actual molar content ratio m' of the Mn element and the Fe element at any position in the ferromanganese phosphate precursor and the theoretical molar content ratio m0 of the Mn element and the Fe element at any position in the ferromanganese phosphate precursor satisfy the following relationship: Δm p =︱m'-m0︱ / m0≤5%。 26. The ferromanganese phosphate precursor according to claim 25, wherein The median particle size of the ferromanganese phosphate precursor is 0.5-10 μm; and / or, the primary particle size of the ferromanganese phosphate precursor is 20-200 nm; And / or, the tap density of the ferromanganese phosphate precursor is 0.50-1.50 g / cm 3 ; And / or, the specific surface area of ​​the ferromanganese phosphate precursor is 10-100m 2 / g.

27. The ferromanganese phosphate precursor according to claim 25, wherein The median particle size of the ferromanganese phosphate precursor is 0.5-5 μm; and / or, the primary particle size of the ferromanganese phosphate precursor is 20-100 nm; And / or, the tap density of the ferromanganese phosphate precursor is 0.80-1.50 g / cm 3 ; And / or, the specific surface area of ​​the ferromanganese phosphate precursor is 10-40m 2 / g.

28. A method for preparing a ferromanganese phosphate precursor, characterized in that: The preparation method comprises the following steps: The ferromanganese phosphate precursor is prepared according to the following steps: (1) mixing a manganese source, an iron source, an R1 source and water to obtain a mixed salt solution; (2) mixing a phosphorus source with water and adding a pH adjuster to obtain a phosphorus source solution; (3) adding the mixed salt solution, the phosphorus source solution and the oxidant into a reactor in parallel to carry out a coprecipitation reaction, and obtaining the ferromanganese phosphate precursor by filtering, washing and drying; The preparation method of the ferromanganese phosphate precursor satisfies the following relationship: K = (0.033K1 + 0.5) L -0.3 ·T 0.2 -0.05 Formula III; Wherein, K is the ratio of n(P) to [n(Mn)+n(Fe)+n(R1)] in the manganese ferrophosphate precursor; K1 is the molar ratio of the amount of the phosphorus source added in terms of n1(P) to the total amount of the manganese source, the iron source and the R1 source added 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; The R1 source is selected from compounds that can provide at least one element among Al, Mg, Ca, Sr, V, Cr, Y, Mo, Nb, B, W, La, Sm, Co, Ni, Cu, Zn, Zr and Ti.

29. The preparation method according to claim 28, wherein 0.9≤K1≤2, 0<L≤3, 30℃≤T≤90℃.

30. A ferromanganese phosphate precursor prepared by the preparation method according to claim 28 or 29.

31. A lithium ion battery, characterized in that: The lithium-ion battery comprises the lithium iron manganese phosphate positive electrode material described in any one of claims 1-8 and 24 or the positive electrode material made from the iron manganese phosphate precursor described in any one of claims 25-27 and 30.

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