CN116675264A - Nickel-manganese binary precursor, preparation method and application thereof, positive electrode material and lithium ion battery - Google Patents

Abstract

The invention relates to the technical field of lithium-ion batteries, in particular to a nickel-manganese binary precursor, a preparation method and application thereof, a positive electrode material, and a lithium-ion battery. The precursor has the composition shown in formula I, Ni _x Mn _y M _z (OH) ₂ (I), 0.8≤x<1, 0<y≤0.2, 0≤z≤0.1, and x+y+z= 1. M is selected from at least one non-Co element; wherein, in the powder X-ray diffraction measurement of the precursor using CuKα rays, 2θ has a characteristic double peak of the 001 crystal plane within the range of 19±1.5°. The precursor provided by the present invention has XRD diffraction {001} double peaks, which further improves the crystallinity of the particles, so that the positive electrode material has a higher tap density under the premise of satisfying structural stability, thereby improving the capacity, rate performance and cycle performance.

Description

Nickel-manganese binary precursor and preparation method and application thereof, positive electrode material, lithium-ion battery

Technical Field

The present invention relates to the technical field of lithium ion batteries, and in particular to a nickel-manganese binary precursor and a preparation method and application thereof, a positive electrode material containing the nickel-manganese binary precursor, and a lithium ion battery containing the positive electrode material.

Background Art

While high-nickel materials have high energy density, their disadvantages are also obvious. The particles on the surface are prone to irreversible phase changes, and their structural stability and high-temperature stability are poor. In addition, the rise in cobalt prices in recent years has led to a substantial increase in the cost of nickel-cobalt-manganese ternary materials. In order to reduce costs, low-cobalt and de-cobaltization of ternary materials have become research trends. However, the main role of cobalt in ternary materials is to improve crystal conductivity and structural stability. Therefore, it is very important to optimize the performance of cobalt-free binary materials.

The indicators of the precursor have a decisive influence on the basic properties of the positive electrode material. The microsphere morphology of the high-nickel electrode material not only has a huge impact on its tap density, but also affects the contact between the positive electrode material and the electrolyte, thereby affecting its side reactions during the charge and discharge process and affecting the material performance. The particle morphology of the precursor is determined by the morphology and arrangement of the primary fiber. At present, the method for preparing the precursor is mainly co-precipitation. During the process, the protective gas or oxidizing gas is controlled, and the pH, temperature, complexing agent concentration, liquid feeding speed, stirring speed and other parameters are adjusted to effectively control the morphology and arrangement of the primary fiber, so as to achieve the purpose of controlling the morphology of the precursor. However, each parameter has a synergistic effect on the growth of the primary fiber crystal surface, and it is not easy to achieve the goal. The {001} crystal plane of the ternary precursor is a low-energy plane. During the co-precipitation process, the crystal is easy to grow along the a-axis and b-axis, resulting in the {001} closed crystal plane being too large in size, and the Li ⁺ transmission path becomes longer, which is not conducive to the output performance.

Therefore, there is an urgent need for a high-nickel, cobalt-free cathode material that has high capacity, high rate performance, and high cycle performance.

Summary of the invention

The purpose of the present invention is to overcome the above-mentioned technical problems and provide a nickel-manganese binary precursor and a preparation method thereof, a positive electrode material, and a lithium-ion battery. The precursor has an XRD diffraction {001} double peak, which improves the crystallinity of the precursor particles, thereby improving the capacity, rate performance, cycle performance and safety performance of the lithium-ion battery.

In order to achieve the above object, the first aspect of the present invention provides a nickel-manganese binary precursor having a composition as shown in Formula I, Ni _x Mn _y M _z (OH) ₂ (I), 0.8≤x＜1, 0＜y≤0.2, 0≤z≤0.1, and x+y+z＝1, and M is selected from at least one non-Co element;

Wherein, in the powder X-ray diffraction measurement of the precursor using CuKα rays, 2θ has a characteristic double peak of the 001 crystal plane in the range of 19±1.5°.

In the present invention, unless otherwise specified, the nickel-manganese binary precursor is referred to as the precursor.

Preferably, in the powder X-ray diffraction measurement of the precursor using CuKα rays, the peak intensity ratio of the characteristic peak of the 101 crystal plane to the characteristic double peak of the 001 crystal plane satisfies: I ₍₁₀₁₎ /I ₍₀₀₁₎ ≥1.5, wherein the characteristic peak 2θ of the 101 crystal plane is in the range of (37-41)°.

Preferably, the characteristic double peak of the 001 crystal plane includes a single peak A and a single peak B, and the single peak A is located on the left side of the single peak B.

Preferably, the peak intensities of the singlet A and the singlet B satisfy: 500≤I _(A) ≤2000, 600≤I _(B) ≤2000, 0.35≤I _(A)/ I _(B) ≤2.4.

Preferably, the half-widths of the single peak A and the single peak B satisfy: 0.4°≤FWHM _(A) ≤0.7°, 0.4°≤FWHM _(B) ≤0.6°, 0.7≤FWHM _(A) /FWHM _(B) ≤1.5.

Preferably, the peak areas of the single peak A and the single peak B satisfy the following conditions: 10000≤A _(A) ≤70000, 10000≤A _(B) ≤75000, 0.6≤A _(A) /A _(B) ≤2.2.

The second aspect of the present invention provides a method for preparing a nickel-manganese binary precursor, the preparation method comprising: mixing a mixed salt solution, a complexing agent and a precipitant and performing a coprecipitation reaction, adjusting the oxygen content in the reaction system to 0.5-10 volume % and the pH value to 10-11.3, and washing and drying the obtained coprecipitation reaction product in sequence to obtain a precursor;

Wherein, the mixed salt solution is selected from an aqueous solution containing a nickel salt, a manganese salt and an optional M source, and M in the M source is selected from at least one non-Co element.

The third aspect of the present invention provides an application of the precursor provided in the first aspect, or the precursor prepared by the preparation method provided in the second aspect, in a positive electrode material.

A fourth aspect of the present invention provides a positive electrode material, which is obtained by sintering the precursor provided by the first aspect, or the precursor obtained by the preparation method provided by the second aspect.

Preferably, the positive electrode material is prepared by the following method: in an oxygen-containing atmosphere, when the precursor does not contain the doping element M, the precursor, a lithium source and an M source are mixed and sintered to obtain the positive electrode material; or, when the precursor contains the doping element M, the precursor and a lithium source are mixed and sintered to obtain the positive electrode material; wherein, M in the M source is selected from at least one non-Co element.

A fifth aspect of the present invention provides a lithium ion battery, wherein the lithium ion battery contains the positive electrode material provided by the fourth aspect.

Compared with the prior art, the present invention has the following advantages:

(1) The precursor provided by the present invention is limited to have a characteristic double peak of the XRD diffraction 001 crystal plane, thereby improving the crystallinity of the particles, especially by limiting I ₍₁₀₁₎ /I ₍₀₀₁₎ ≥1.5, further improving the crystallinity of the precursor, so that the positive electrode material obtained by sintering the precursor has a higher tap density while satisfying the structural stability;

(2) The precursor preparation method provided by the present invention adopts the technical means of co-precipitation, and controls the oxygen content in the reaction system to be 0.5-10 volume % and the pH value to be 10-11.3, so that the precursor produces an XRD diffraction double peak; at the same time, the preparation method simplifies the process flow, is relatively low in cost, and is suitable for industrial production;

(3) The precursor provided by the present invention is used in lithium-ion batteries to effectively improve the capacity, rate performance and capacity retention rate of the battery.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a SEM image of the precursor S1 prepared in Example 1, wherein FIG1a-1b are SEM images of primary particles of the precursor S1, and FIG1c-1d are SEM images of secondary particles of the precursor S1;

FIG2 is an XRD diagram of the precursor S1 obtained in Example 1;

FIG3 is a SEM image of the precursor S2 prepared in Example 2, wherein FIGS. 3a-3b are SEM images of primary particles of the precursor S2, and FIGS. 3c-3d are SEM images of secondary particles of the precursor S2;

FIG4 is an XRD diagram of the precursor S2 prepared in Example 2;

FIG5 is a SEM image of the precursor S3 prepared in Example 3, wherein FIGS. 5a-5b are SEM images of primary particles of the precursor S3, and FIGS. 5c-5d are SEM images of secondary particles of the precursor S3;

FIG6 is an XRD pattern of the precursor S3 obtained in Example 3;

FIG. 7 is a SEM image of the precursor DS1 prepared in Comparative Example 1, wherein FIGS. 7a-7b are SEM images of primary particles of the precursor DS1, and FIGS. 7c-7d are SEM images of secondary particles of the precursor DS1;

FIG8 is an XRD diagram of the precursor DS1 prepared in Comparative Example 1.

DETAILED DESCRIPTION

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 regarded as specifically disclosed in this article.

A first aspect of the present invention provides a nickel-manganese binary precursor having a composition as shown in Formula I, Ni _x Mn _y M _z (OH) ₂ (I), 0.8≤x＜1, 0＜y≤0.2, 0≤z≤0.1, and x+y+z＝1, and M is selected from at least one non-Co element;

Wherein, in the powder X-ray diffraction measurement of the precursor using CuKα rays, 2θ has a characteristic double peak of the 001 crystal plane in the range of 19±1.5°.

In the present invention, unless otherwise specified, in Formula I, M is selected from at least one non-Co element, which means that the precursor is a high-nickel cobalt-free binary material, that is, M is selected from elements other than Co.

In the present invention, unless otherwise specified, the precursor having a characteristic double peak of 001 crystal plane within the range of 2θ of 19±1.5° means that the XRD peak of the 001 crystal plane of the precursor is split into a double peak, that is, split into a single peak A located on the left and a single peak B located on the right.

In some embodiments of the present invention, in Formula I, 0.8≤x＜1, 0＜y≤0.2, 0≤z≤0.1, and x+y+z＝1, and M is selected from at least one non-Co element.

In some embodiments of the present invention, it is further preferred that in formula I, 0.85≤x≤0.99, 0.01≤y≤0.15, 0.001≤z≤0.1, and x+y+z＝1, and M is selected from at least one element of La, Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B, Y and Al.

In some embodiments of the present invention, more preferably, in formula I, 0.9≤x≤0.98, 0.02≤y≤0.1, 0.001≤z≤0.01, and x+y+z＝1, and M is selected from at least one element of La, Cr, Mo, Hf, Ti, Zn, Y, Zr, W, Nb, V, Mg, B, Y and Al.

In the present invention, by regulating the indices (x, y, z) of the metal elements and the type of the M element in formula I, the tap density of the positive electrode material containing the precursor is further regulated, thereby regulating the electrochemical performance of the lithium-ion battery.

In some embodiments of the present invention, preferably, in the powder X-ray diffraction measurement of the precursor using CuKα rays, the peak intensity ratio of the characteristic peak of the 101 crystal plane to the characteristic double peak of the 001 crystal plane satisfies: I ₍₁₀₁₎ /I ₍₀₀₁₎ ≥1.5, for example, 1.5, 1.8, 2/2.2, 2.5, 2.8, 3, and any value in the range composed of any two numerical values, preferably satisfies: 1.5≤I ₍₁₀₁₎ /I ₍₀₀₁₎ ≤3, wherein the characteristic peak 2θ of the 101 crystal plane is in the range of (37-41)°.

In the present invention, when I ₍₁₀₁₎ /I ₍₀₀₁₎ satisfies the above range, the precursor has high crystallinity, and after being sintered into a positive electrode material, excessive lithium dissolution can be suppressed, and in particular, gas generation caused by the reaction between the electrolyte and the excess lithium can be suppressed, thereby improving the structural stability during lithium extraction, thereby becoming a lithium composite oxide with less oxygen deficiency, so that the positive electrode material has a high tap density, and a lithium ion battery containing the positive electrode material can have a high initial charge and discharge capacity, initial efficiency, rate performance and high capacity retention rate.

In some embodiments of the present invention, preferably, the peak intensity I ₍₁₀₁₎ of the characteristic double peak of the 001 crystal plane is 300-4000, preferably 500-3000; the half-peak width FWHM ₍₁₀₁₎ is (0.5-2)°, preferably (0.6-1.8)°. In the present invention, the Jade analysis shows that the reason for the appearance of the 001 crystal plane split peak is that the nickel-manganese oxide impurity phase appears in the nickel-manganese hydroxide crystal, and manganese mainly plays a role in stabilizing the structure and improving the safety performance of the material.

In some embodiments of the present invention, preferably, as shown in FIG. 2 , FIG. 4 and FIG. 6 , the characteristic double peak of the 001 crystal plane includes a single peak A and a single peak B, and the single peak A is located on the left side of the single peak B.

In some embodiments of the present invention, preferably, the peak intensities of the singlet A and the singlet B satisfy: 500≤I _(A) ≤2000, 600≤I _(B) ≤2000, 0.35≤I _(A)/ I _(B) ≤2.4.

In some embodiments of the present invention, preferably, the half-widths of the single peak A and the single peak B satisfy: 0.4°≤FWHM _(A) ≤0.7°, 0.4°≤FWHM _(B) ≤0.6°, 0.7≤FWHM _(A) /FWHM _(B) ≤1.5.

In some embodiments of the present invention, preferably, the peak areas of the single peak A and the single peak B satisfy: 10000≤A _(A) ≤70000, 10000≤A _(B) ≤75000, 0.6≤A _(A) /A _(B) ≤2.2.

In the present invention, by limiting the peak intensity, half peak width and peak area of the single peak A and the single peak B to meet the above ranges, the precursor has the characteristics of larger BET and tap density, and narrow particle size distribution.

In some embodiments of the present invention, preferably, the precursor is a secondary particle composed of primary particles, and the primary particles have a wedge-shaped structure; further preferably, the precursor has a spherical structure.

In some embodiments of the present invention, preferably, the BET of the precursor is 3-25 m ² /g, for example, 3 m ² /g, 5 m ² /g, 10 m ² /g, 15 m ² /g, 20 m ² /g, 25 m ² /g, and any value in a range consisting of any two values, preferably 5-20 m ² /g; the tap density is ≥ 1 g/cm ³ , for example, 1 g/cm ³ , 1.3 g/cm ³ , 1.5 g/cm ³ , 2 g/cm ³ , 2.5 g/cm ³ , and any value in a range consisting of any two values, preferably 1.3-2.5 g/cm ³ .

In some embodiments of the present invention, preferably, the particle size distribution K ₉₀ of the precursor satisfies: 0.4≤K ₉₀ ≤0.8, for example, 0.4, 0.5, 0.6, 0.7, 0.8, and any value in the range consisting of any two values, wherein K ₉₀ =(D ₉₀ -D ₁₀ )/D ₅₀ , D ₉₀ , D ₁₀ and D ₅₀ respectively refer to the particle sizes of the precursor at which the volume cumulative values in the particle size distribution are 90%, 10% and 50%, respectively, and the unit is μm.

In some embodiments of the present invention, preferably, the D ₅₀ of the precursor is 6-20 μm, preferably 8-14 μm.

The second aspect of the present invention provides a method for preparing a nickel-manganese binary precursor, the preparation method comprising: mixing a mixed salt solution, a complexing agent and a precipitant and performing a coprecipitation reaction, adjusting the oxygen content in the reaction system to 0.5-10 volume % and the pH value to 10-11.3, and washing and drying the obtained coprecipitation reaction product in sequence to obtain a precursor;

Wherein, the mixed salt solution is selected from an aqueous solution containing a nickel salt, a manganese salt and an optional M source, and M in the M source is selected from at least one non-Co element.

In the present invention, the precursor produces an XRD diffraction bifurcated double peak by controlling the oxygen content in the reaction system to be 0.5-10% by volume, for example, 0.5% by volume, 1% by volume, 2% by volume, 5% by volume, 8% by volume, 10% by volume, and any value in the range of any two values. Preferably, the oxygen content in the reaction system is regulated to be 0.5-8% by volume. When the oxygen content is low, the precursor is in a hydroxide state, and the 001 peak has no split peak phenomenon; when the oxygen content is high, most of the crystals are composed of oxides, the primary fibers are thinner, the 001 peak has no split peak phenomenon, and the half-peak width is narrower.

In some embodiments of the present invention, preferably, when the complexing agent is selected from a compound containing ammonium ions, the ammonia concentration in the reaction system is regulated to be 1-12 g/L, for example, 1 g/L, 2 g/L, 5 g/L, 8 g/L, 10 g/L, 12 g/L, and any value in the range consisting of any two values, preferably 3-8 g/L.

In some embodiments of the present invention, preferably, the conditions of the coprecipitation reaction include: temperature of 50-80° C., pH of 10-11.3, preferably 10.3-11.1; rotation speed of 250-750 rpm.

In the present invention, the particle size of the precursor is regulated by regulating the time of the coprecipitation reaction. As the coprecipitation reaction time increases, the particles of the coprecipitation reaction product gradually grow and the crystallinity is continuously improved; during the reaction process, the slurry particle size is tested with a laser particle size analyzer every 2 hours, and the pH value in the reactor is adjusted to keep the pH in the reactor within the range of (10-11.3) ± 0.1.

In some embodiments of the present invention, preferably, calculated as metal elements, the nickel salt, manganese salt and M source satisfy n(Ni):n(Mn):n(M), 0.8≤n(Ni)＜1, 0＜n(Mn)≤0.2, 0≤n(M)≤0.1; further preferably, 0.85≤n(Ni)≤0.99, 0.01≤n(Mn)≤0.15, 0.001≤n(M)≤0.1; more preferably, 0.9≤n(Ni)≤0.98, 0.02≤n(Mn)≤0.1, 0.001≤n(M)≤0.01.

In some embodiments of the present invention, preferably, M in the M source is selected from at least one element of La, Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B, Y and Al; further preferably, M in the M source is selected from at least one element of La, Cr, Mo, Hf, Ti, Zn, Y, Zr, W, Nb, V, Mg, B, Y and Al.

In some embodiments of the present invention, the nickel salt includes but is not limited to nickel sulfate, nickel nitrate, nickel chlorate, etc.; the manganese salt includes but is not limited to manganese sulfate, manganese nitrate, manganese chlorate, etc.; the M source includes but is not limited to at least one selected from oxides, sulfates, nitrates, and chlorates containing M.

In a specific embodiment of the present invention, the M source is selected from at least one of oxides, sulfates, nitrates and chlorates containing La, Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B, Y and Al, and is preferably selected from at least one of oxides, sulfates, nitrates and chlorates containing La, Cr, Mo, Hf, Ti, Zn, Y, Zr, W, Nb, V, Mg, B, Y and Al.

In some embodiments of the present invention, preferably, the concentration of the mixed salt solution is 0.1-10 mol/L in terms of metal elements, and the nickel salt, manganese salt and M source satisfy n(Ni):n(Mn):n(M), 0.8≤n(Ni)＜1, 0＜n(Mn)≤0.2, 0≤n(M)≤0.1; further preferably, 0.85≤n(Ni)≤0.99, 0.01≤n(Mn)≤0.15, 0.001≤n(M)≤0.1; more preferably, 0.9≤n(Ni)≤0.98, 0.02≤n(Mn)≤0.1, 0.001≤n(M)≤0.01.

In the present invention, the particle size range of the precursor is regulated by controlling the inlet flow rate of the mixed salt. Preferably, the inlet flow rate of the mixed metal salt is 50-300 mL/min, preferably 150-250 mL/min.

In a specific embodiment of the present invention, the precipitant includes but is not limited to sodium hydroxide and/or potassium hydroxide; the complexing agent includes but is not limited to ammonia water, etc. In the present invention, the precipitant and the complexing agent are both in the form of aqueous solution, and the concentrations of the precipitant aqueous solution and the complexing agent aqueous solution are independently 5-13.3 mol/L.

In some embodiments of the present invention, preferably, the washing process comprises: subjecting the coprecipitation reaction product to alkali washing and water washing alternately.

In a specific embodiment of the present invention, the washing process includes: alkali washing the precipitation reaction product and alkali solution to obtain an alkali washed product and washing with deionized water to obtain a washed product; repeating the above operation 1-5 times on the washed product to obtain the precursor. In the present invention, the alkali solution includes but is not limited to a sodium hydroxide solution and/or a potassium hydroxide solution with a concentration of 0.1-2 mol/L.

In some embodiments of the present invention, preferably, the drying conditions include: temperature of 80-150° C. and time of 2-6 h.

The third aspect of the present invention provides an application of the precursor provided in the first aspect, or the precursor prepared by the preparation method provided in the second aspect, in a positive electrode material.

A fourth aspect of the present invention provides a positive electrode material, which is obtained by sintering the precursor provided by the first aspect, or the precursor obtained by the preparation method provided by the second aspect.

In the present invention, the above-mentioned precursor is used for the positive electrode material, which can inhibit the excessive dissolution of lithium, especially the gas generation caused by the reaction between the electrolyte and the excess lithium, and improve the structural stability during lithium insertion and extraction, thereby becoming a lithium composite oxide with less oxygen deficiency, and the positive electrode material has a high tap density.

In some embodiments of the present invention, preferably, the positive electrode material is prepared by the following method: in an oxygen-containing atmosphere, when the precursor does not contain the doping element M, the precursor, a lithium source and an M source are mixed and sintered to obtain the positive electrode material; or, when the precursor contains the doping element M, the precursor and a lithium source are mixed and sintered to obtain the positive electrode material; wherein, M in the M source is selected from at least one non-Co element.

In the present invention, the doping element M can be added in the preparation of the precursor or in the preparation of the positive electrode material. Preferably, when the doping element M is added in the preparation of the precursor, the source of M is selected from soluble compounds; when the doping element M is added in the preparation of the positive electrode material, the source of M is selected from oxides.

In a specific embodiment of the present invention, the lithium source includes but is not limited to lithium oxide, lithium hydroxide and the like.

In some embodiments of the present invention, preferably, the usage ratio of the lithium source satisfies: 0.9≤[n(Li)]/[n(Ni)+n(Mn)+n(M)]≤1.2, for example, 0.9, 1, 1.01, 1.02, 1.05, 1.06, 1.1, 1.15, 1.2, and any value in the range consisting of any two numerical values, further preferably satisfies: 1≤[n(Li)]/[n(Ni)+n(Mn)+n(M)]≤1.1, and more preferably satisfies: 1.01≤[n(Li)]/[n(Ni)+n(Mn)+n(M)]≤1.06.

In the present invention, unless otherwise specified, the M source is in accordance with the above definition, and the present invention will not elaborate on it here.

In some embodiments of the present invention, preferably, the amount of the M source satisfies: 0≤[n(M)]/[n(Ni)+n(Mn)+n(M)]≤0.1, for example, 0, 0.001, 0.002, 0.005, 0.008, 0.01, 0.05, 0.1, and any value in the range consisting of any two numerical values, further preferably satisfies: 0.001≤[n(M)]/[n(Ni)+n(Mn)+n(M)]≤0.1, more preferably satisfies: 0.001≤[n(M)]/[n(Ni)+n(Mn)+n(M)]≤0.01.

In some embodiments of the present invention, preferably, M in the M source is selected from at least one element of Al, Fe, Mg, B, Ca, Sr, Ba, Zr, Ti, Ce, Y, W, La, Nb, Ta, Zn, Co and Mo, and is preferably selected from at least one element of La, Cr, Mo, Hf, Ti, Zn, Y, Zr, W, Nb, V, Mg, B, Y and Al.

In some embodiments of the present invention, preferably, the oxygen content in the oxygen-containing atmosphere is ≥ 80 volume %, preferably ≥ 95 volume %.

In some embodiments of the present invention, preferably, the sintering conditions include: temperature of 600-900°C, preferably 700-800°C; time of 0.1-20h, preferably 0.1-15h; heating rate of 1-20°C/min, preferably 1-5°C/min.

In some embodiments of the present invention, preferably, the cathode material has a composition shown in Formula II, Li _{1+ a} Ni _α Mn _β M _γ O ₂ (II);

Among them, -0.1≤a≤0.2, 0.8≤α＜1, 0＜β≤0.2, 0≤γ≤0.1, and α+β+γ＝1; M is at least one non-Co element.

In some embodiments of the present invention, it is further preferred that in formula II, 0≤a≤0.1, 0.85≤α≤0.99, 0.01≤β≤0.15, 0.001≤γ≤0.1, and α+β+γ＝1; M is selected from at least one element of La, Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B, Y and Al.

In some embodiments of the present invention, more preferably, in formula II, 0.01≤a≤0.06, 0.9≤α≤0.98, 0.02≤β≤0.1, 0.001≤γ≤0.01, and α+β+γ＝1; M is selected from at least one element of La, Cr, Mo, Hf, Ti, Zn, Y, Zr, W, Nb, V, Mg, B, Y and Al.

In some embodiments of the present invention, preferably, the tap density of the cathode material is ≥2.5 g/cm ³ , for example, 2.5 g/cm ³ , 2.6 g/cm ³ , 2.7 g/cm ³ , 2.8 g/cm ³ , 2.9 g/cm ³ , 3 g/cm ³ , and any value in a range consisting of any two values, preferably 2.5-3 g/cm ³ .

In some embodiments of the present invention, preferably, the positive electrode material has a layered structure.

A fifth aspect of the present invention provides a lithium ion battery, wherein the lithium ion battery contains the positive electrode material provided by the fourth aspect.

The present invention will be described in detail below through examples.

The process parameters for preparing the precursors and positive electrode materials in the examples and comparative examples are listed in Table 1, and the physical property parameters of the precursors and positive electrode materials prepared in the examples and comparative examples are listed in Table 2.

Example 1

(1) Based on the metal elements, NiSO ₄ ·6H ₂ O and MnSO ₄ ·H ₂ O were dissolved in water at a molar ratio of 95:5 to prepare a 2 mol/L mixed salt solution; 8 mol/L sodium hydroxide solution was prepared as a precipitant, and 10 mol/L ammonia water was prepared as a complexing agent;

(2) Deionized water was added to a 5L reactor to cover the upper stirring blade, the reactor temperature was controlled at 65°C, and the stirring speed was set to 770 rpm; the above-mentioned ammonia water and sodium hydroxide solution were added to the reactor to adjust the bottom liquid so that the ammonia concentration in the reactor was adjusted to 3 g/L, the pH value was adjusted to 11, nitrogen was introduced into the reactor, the nitrogen flow rate was 20 L/h, and the oxygen content in the reactor was 5 volume %;

(3) adding the mixed salt solution, sodium hydroxide aqueous solution and ammonia water into the reactor by a metering pump, setting the inlet flow rate of the mixed salt solution to 190 mL/h, and automatically adjusting the inlet flow rates of the sodium hydroxide solution and ammonia water according to the pH value and ammonia concentration to carry out a coprecipitation reaction. During the reaction, the particle size of the slurry is tested every 2 hours by a laser particle size analyzer, and the pH value in the reactor is adjusted to maintain the pH value in the reactor within the range of 11±0.1;

(4) When the particle size _D50 grows to 14 μm, the liquid feeding is stopped, and the coprecipitation reaction product is washed alternately with 0.2 mol/L sodium hydroxide solution at 75°C and water, and then dried at 120°C _for 3 h to obtain a precursor S1 with the general formula _Ni0.95Mn0.05 (OH) ₂ ;

(5) In an oxygen-containing atmosphere (oxygen content of 95 volume %), the above-mentioned precursor S1, lithium source (lithium hydroxide) and M source (TiO ₂ ) were mixed, and the temperature was increased to 800° C. at 3° C./min for 12 h, and then cooled to room temperature to obtain a positive electrode material P1 with a general formula of Li _1.02 Ni _0.945 Mn _0.05 Ti _0.005 O ₂ ;

The amount ratio of the lithium source satisfies: [n(Li)]/[n(Ni)+n(Mn)+n(M)]=1.02; the amount of the M source satisfies: [n(M)]/[n(Ni)+n(Mn)+n(M)]=0.005;

The SEM image of the precursor S1 is shown in FIG1 . As can be seen from FIG1 , the precursor S1 is a secondary particle composed of primary particles, the primary particles are elongated wedge-shaped structures, and the secondary particles have a spherical structure.

The XRD pattern of the precursor S1 is shown in FIG. 2 . As can be seen from FIG. 2 , the precursor S1 has a characteristic double peak of the 001 crystal plane within the range of 2θ=18.7±1.5°.

Example 2

(1) Based on metal elements, NiSO ₄ ·6H ₂ O and MnSO ₄ ·H ₂ O were dissolved in water at a molar ratio of 90:10 to prepare a 1.5 mol/L mixed salt solution; 4 mol/L sodium hydroxide solution was prepared as a precipitant, and 10 mol/L ammonia water was prepared as a complexing agent;

(2) Deionized water was added to a 5L reactor to cover the upper stirring blade, the reactor temperature was controlled at 55°C, and the stirring speed was set to 500 rpm; the above-mentioned ammonia water and sodium hydroxide solution were added to the reactor to adjust the bottom liquid so that the ammonia concentration in the reactor was adjusted to 7 g/L and the pH value was adjusted to 10.8. Nitrogen was introduced into the reactor at a nitrogen flow rate of 100 L/h, and the oxygen content in the reactor was 0.5 volume %;

(3) adding the mixed salt solution, sodium hydroxide aqueous solution and ammonia water into the reactor through a metering pump, setting the inlet flow rate of the mixed salt solution to 100 mL/h, and automatically adjusting the inlet flow rates of the sodium hydroxide solution and ammonia water according to the pH value and ammonia concentration to carry out a coprecipitation reaction. During the reaction, the particle size of the slurry is tested every 2 hours with a laser particle size analyzer, and the pH value in the reactor is adjusted to maintain the pH in the reactor within the range of 10.8±0.1;

(4) When the particle size _D50 grows to 10 μm, the liquid feeding is stopped, and the coprecipitation reaction product is washed alternately with 0.2 mol/L sodium hydroxide solution at 75°C and water, and then dried at 120°C _{for 3 h to obtain a precursor S2 with the general formula Ni0.9Mn0.1 (} OH) ₂ ;

(5) In an oxygen-containing atmosphere (oxygen content of 95 volume %), the above-mentioned precursor S2, lithium source (lithium hydroxide) and M source (TiO ₂ ) were mixed, and the temperature was increased to 800° C. at 3° C./min for 12 h, and then cooled to room temperature to obtain a positive electrode material P1 with a general formula of Li _1.02 Ni _0.896 Mn _0.099 Ti _0.005 O ₂ ;

The usage ratio of the lithium source satisfies: [n(Li)]/[n(Ni)+n(Mn)+n(M)]=1.02; the usage ratio of the M source satisfies: [n(M)]/[n(Ni)+n(Mn)+n(M)]=0.005.

The SEM image of the precursor S2 is shown in FIG3 . As can be seen from FIG3 , the precursor S2 is a secondary particle composed of primary particles, the primary particles are elongated wedge-shaped structures, and the secondary particles have a spherical structure.

The XRD pattern of the precursor S2 is shown in FIG. 4 . As can be seen from FIG. 4 , the precursor S2 has a characteristic double peak of the 001 crystal plane in the range of 2θ=19.5±1°.

Example 3

(1) Based on the metal elements, NiSO ₄ ·6H ₂ O and MnSO ₄ ·H ₂ O were dissolved in water at a molar ratio of 98:2 to prepare a 1.5 mol/L mixed salt solution; 8 mol/L sodium hydroxide solution was prepared as a precipitant, and 5 mol/L ammonia water was prepared as a complexing agent;

(2) Deionized water was added to a 5L reactor to cover the upper stirring blade, the reactor temperature was controlled at 75°C, and the stirring speed was set to 700 rpm; the above-mentioned ammonia water and sodium hydroxide solution were added to the reactor to adjust the bottom liquid, so that the ammonia concentration in the reactor was adjusted to 11 g/L, the pH value was adjusted to 10.3, nitrogen was introduced into the reactor, the nitrogen flow rate was 10 L/h, and the oxygen content in the reactor was 8 volume %;

(3) adding the mixed salt solution, sodium hydroxide aqueous solution and ammonia water into the reactor through a metering pump, the inlet flow rate of the mixed salt solution is set to 240 mL/h, the inlet flow rates of the sodium hydroxide solution and ammonia water are automatically adjusted according to the pH value and ammonia concentration, and a coprecipitation reaction is carried out. During the reaction, the slurry particle size is tested every 2 hours with a laser particle size analyzer, and the pH value in the reactor is adjusted to keep the pH in the reactor within the range of 10.3±0.1;

(4) When the particle size _D50 grows to 12 μm, the liquid feeding is stopped, and the coprecipitation reaction product is washed alternately with 0.2 mol/L sodium hydroxide solution at 75°C and water, and then dried at 120°C _for 3 h to obtain a precursor S3 with a general formula of _Ni0.98Mn0.02 (OH) ₂ ;

(5) In an oxygen-containing atmosphere (oxygen content of 95 volume %), the above-mentioned precursor S3, lithium source (lithium hydroxide) and M source (TiO ₂ ) were mixed, and the temperature was increased to 800° C. at 3° C./min for 12 h, and then cooled to room temperature to obtain a positive electrode material P3 with a general formula of Li _1.02 Ni _0.975 Mn _0.02 Ti _0.005 O ₂ ;

The usage ratio of the lithium source satisfies: [n(Li)]/[n(Ni)+n(Mn)+n(M)]=1.02; the usage ratio of the M source satisfies: [n(M)]/[n(Ni)+n(Mn)+n(M)]=0.005.

The SEM image of the precursor S3 is shown in FIG5 . As can be seen from FIG5 , the precursor S3 is a secondary particle composed of primary particles, the primary particles are elongated wedge-shaped structures, and the secondary particles have a spherical structure.

The XRD pattern of the precursor S3 is shown in FIG. 6 . As can be seen from FIG. 6 , the precursor S3 has a characteristic double peak of the 001 crystal plane in the range of 2θ=19.4±1°.

Example 4

(1) Based on the metal elements, NiSO ₄ ·6H ₂ O and MnSO ₄ ·H ₂ O were dissolved in water at a molar ratio of 95:5 to prepare a 1.5 mol/L mixed salt solution; 8 mol/L sodium hydroxide solution was prepared as a precipitant, and 5 mol/L ammonia water was prepared as a complexing agent;

(2) Deionized water was added to a 5L reactor to cover the upper stirring blade, the reactor temperature was controlled at 75°C, and the stirring speed was set to 700 rpm; the above-mentioned ammonia water and sodium hydroxide solution were added to the reactor to adjust the bottom liquid so that the ammonia concentration in the reactor was adjusted to 11 g/L and the pH value was adjusted to 10.5. Nitrogen was introduced into the reactor at a nitrogen flow rate of 50 L/h, and the oxygen content in the reactor was 2.5% by volume;

(3) adding the mixed salt solution, sodium hydroxide aqueous solution and ammonia water into the reactor by a metering pump, setting the inlet flow rate of the mixed salt solution to 240 mL/h, and automatically adjusting the inlet flow rates of the sodium hydroxide solution and ammonia water according to the pH value and ammonia concentration to carry out a coprecipitation reaction. During the reaction, the particle size of the slurry is tested by a laser particle size analyzer every 2 hours, and the pH value in the reactor is adjusted to keep the pH value in the reactor within the range of 10.5±0.1;

(4) When the particle size _D50 grows to 8 μm, the liquid feeding is stopped, and the coprecipitation reaction product is washed alternately with 0.2 mol/L sodium hydroxide solution at 75°C and water, and then dried at 120°C _{for 3 h to obtain a precursor S4 with the general formula Ni0.95Mn0.5 (} OH) ₂ ;

The precursor S4 is a secondary particle composed of primary particles, the primary particles are elongated wedge-shaped structures, and the secondary particles have spherical structures; the precursor S4 has a characteristic double peak of the 001 crystal plane in the range of 2θ of 18.7±1°;

(5) In an oxygen-containing atmosphere (oxygen content of 95 volume %), the above-mentioned precursor S4, lithium source (lithium hydroxide) and M source (TiO ₂ ) were mixed, and the temperature was increased to 800° C. at 3° C./min for 12 h, and then cooled to room temperature to obtain a positive electrode material P4 with a general formula of Li _1.02 Ni _0.945 Mn _0.05 Ti _0.005 O ₂ ;

The usage ratio of the lithium source satisfies: [n(Li)]/[n(Ni)+n(Mn)+n(M)]=1.02; the usage ratio of the M source satisfies: [n(M)]/[n(Ni)+n(Mn)+n(M)]=0.005.

Example 5

(1) Based on the metal elements, NiSO ₄ ·6H ₂ O, MnSO ₄ ·H ₂ O, and TiOSO ₄ were dissolved in water at a molar ratio of 90:9.5:0.5 to prepare a 1.7 mol/L mixed salt solution; 8 mol/L sodium hydroxide solution was prepared as a precipitant, and 5 mol/L ammonia water was prepared as a complexing agent;

(2) Deionized water was added to a 5L reactor to cover the upper stirring blade, the reactor temperature was controlled at 75°C, and the stirring speed was set to 700 rpm; the above-mentioned ammonia water and sodium hydroxide solution were added to the reactor to adjust the bottom liquid so that the ammonia concentration in the reactor was adjusted to 5 g/L, the pH value was adjusted to 10.8, nitrogen was introduced into the reactor, the nitrogen flow rate was 50 L/h, and the oxygen content in the reactor was 2.5% by volume;

(3) adding the mixed salt solution, sodium hydroxide aqueous solution and ammonia water into the reactor through a metering pump, setting the inlet flow rate of the mixed salt solution to 240 mL/h, and automatically adjusting the inlet flow rates of the sodium hydroxide solution and ammonia water according to the pH value and ammonia concentration to carry out a coprecipitation reaction. During the reaction, the particle size of the slurry is tested every 2 hours with a laser particle size analyzer, and the pH value in the reactor is adjusted to maintain the pH in the reactor within the range of 10.8±0.1;

(4) When the particle size _D50 grows to 10 μm, the liquid feeding is stopped, and the coprecipitation reaction product is washed alternately with 0.2 mol/L sodium hydroxide solution at 75°C and water, and then dried at 120°C _for 3 h to obtain a precursor S5 with _a general formula of _{Ni0.9Mn0.095Ti0.005} (OH) ₂ ;

The precursor S5 is a secondary particle composed of primary particles, the primary particles are elongated wedge-shaped structures, and the secondary particles have spherical structures; the precursor S5 has a characteristic double peak of the 001 crystal plane in the range of 2θ of 18.7±1°;

(5) In an oxygen-containing atmosphere (oxygen content of 95 volume %), the precursor S5 and a lithium source (lithium hydroxide) are mixed, and the temperature is increased to 800° C. at a rate of 3° C./min, sintered for 12 h, and cooled to room temperature to obtain a positive electrode material P5 having a general formula of Li _1.02 Ni _0.9 Mn _0.095 Ti _0.005 O ₂ ;

The usage ratio of the lithium source satisfies: [n(Li)]/[n(Ni)+n(Mn)+n(M)]=1.02.

Example 6

According to the method of Example 1, the difference is that

In step (1), M source is added, and the molar ratio of NiSO ₄ ·6H ₂ O, MnSO ₄ ·H ₂ O, and TiOSO ₄ is replaced to 94.5:5:0.5 in terms of metal elements. The pH value is controlled within the range of 11±0.1, and the other conditions are the same to obtain precursor S6 and positive electrode material P6.

Example 7

According to the method of Example 1, the difference is that

In step (1), M source is added, and the molar ratio of NiSO ₄ ·6H ₂ O, MnSO ₄ ·H ₂ O, and Y ₂ O ₃ is replaced to 94.5:5:0.5 in terms of metal elements, and the pH value is controlled within the range of 11±0.1. The other conditions are the same to obtain precursor S7 and positive electrode material P7.

Comparative Example 1

According to the method of Example 1, the difference is that

In step (2), the nitrogen flow rate is regulated to 100 L/h so that the oxygen content in the reactor is 0.5% by volume, and the pH is controlled in the range of 11.6±0.1. The other conditions are the same, and a precursor DS1 with a general formula of Ni _0.95 Mn _0.5 (OH) ₂ and a positive electrode material DP1 with a general formula of Li _1.02 Ni _0.945 Mn _0.05 Ti _0.005 O ₂ are obtained.

The SEM image of the precursor DS1 is shown in FIG7 . As can be seen from FIG7 , the precursor DS1 is a secondary particle composed of primary particles, the primary particles are elongated wedge-shaped structures, and the secondary particles have a spherical structure.

Among them, the XRD pattern of the above-mentioned precursor DS1 is shown in Figure 8. It can be seen from Figure 8 that the diffraction peak of the precursor DS1 on the 001 crystal plane is a single peak.

Comparative Example 2

According to the method of Example 1, the difference is that

In step (2), compressed air is introduced to control the oxygen content in the reactor to 16 volume %, and the other conditions are the same, to obtain a precursor DS2 with a general formula of Ni _0.95 Mn _0.5 (OH) ₂ and a positive electrode material DP2 with a general formula of Li _1.02 Ni _0.945 Mn _0.05 Ti _0.005 O ₂ .

Comparative Example 3

According to the method of Example 1, the difference is that

In step (5), the type of M source is replaced with CoSO ₄ , and the other conditions are the same, to obtain the positive electrode material DS3.

Table 1

Note: 1- Inlet flow rate of mixed salt solution, mL/h.

Table 1

Table 2

Note: *-2θ has a characteristic double peak of 001 crystal plane in the range of 19±1.5°.

Table 2

Table 2

Note: 2-K ₉₀ = (D ₉₀ -D ₁₀ )/D ₅₀ , D ₉₀ , D ₁₀ and D ₅₀ refer to the particle sizes of the precursor at which the cumulative volume values in the particle size distribution are 90%, 10% and 50% respectively, and the unit is μm.

Table 2

It can be seen from the data in Table 1-2 that compared with Comparative Examples 1-3, by adjusting the oxygen content in the reaction system to 0.5-10 volume % and the pH value to 10-11.3, the precursors S1-S7 obtained in Examples 1-7 all have XRD diffraction 001 double peaks and satisfy 1.5≤I ₍₁₀₁₎ /I ₍₀₀₁₎ ≤3, thereby improving the crystallinity of the particles and thus improving the crystallinity of the precursor, so that the positive electrode material obtained by sintering the above precursor has a higher tap density while satisfying the structural stability.

At the same time, the precursors prepared in Examples 1-7 further define the characteristic double peaks of the 001 crystal plane, including single peak A and single peak B, and define the half-peak width, peak intensity and peak area parameters of single peak A and single peak B, so that the precursors have larger BET and tap density, as well as a narrow particle size distribution.

Test Case

The positive electrode materials prepared in the examples and comparative examples were subjected to electrochemical performance tests.

Assembling batteries: The above-mentioned positive electrode materials, conductive carbon black and polyvinylidene fluoride (PVDF) were weighed and mixed according to a mass ratio of 95:2.5:2.5, NMP was added and stirred to form a uniform slurry, coated on aluminum foil, scraped flat, and rolled flat after drying. Positive electrode sheets with a diameter of 12 mm and a thickness of 120 μm were punched out at a pressure of 100 MPa, and then placed in a vacuum oven at 120°C for 12 hours to obtain positive electrode sheets.

The button cell assembly process was carried out in an Ar gas-protected glove box, where the water content and oxygen content were both less than 5ppm; the positive electrode used the pole piece obtained above, the negative electrode used a Li metal sheet with a diameter of 17mm and a thickness of 1mm; the diaphragm used a polyethylene porous membrane with a thickness of 25μm, the electrolyte used an equal amount of ethylene carbonate (EC) and diethylene carbonate (DEC) dissolved with 1mol/L LiPF6, and the battery shell used a button cell shell of model 2025. After the assembly was completed, an unactivated battery was obtained.

The performance of the assembled lithium-ion battery was tested, and the test results are shown in Table 3. The charging capacity of the lithium-ion battery was measured by taking a button cell that was left to stand for 2 hours after assembly, charging it at 0.1C (1C = 200mA/g) at room temperature to a cut-off voltage of 4.3V, and then charging it at a constant voltage for 30 minutes;

The discharge capacity is measured by discharging the button cell at room temperature at a constant current of 0.1C to 3.0V.

The first efficiency is measured by dividing the above 0.1C discharge capacity by the 0.1C charge capacity;

The 1C/0.1C rate performance is measured by dividing the 1C discharge capacity by the 0.1C discharge capacity at room temperature, with a voltage window of 4.3-3.0V, by subjecting the button cell that has completed a 0.1C charge and discharge to constant currents of 0.2C, 0.33C, 0.5C, and 1C. The rate performance is measured by dividing the 1C discharge capacity by the 0.1C discharge capacity.

The 80-week cycle retention rate is measured by taking the button cell that has completed one 0.1C charge and discharge cycle as described above, charging and discharging at 1C constant current for 80 cycles at room temperature, with a voltage window of 4.3-3.0V, and dividing the discharge capacity at the 80th week by the discharge capacity at the first week.

Table 3

It can be seen from the data in Table 3 that, compared with Comparative Examples 1-3, the lithium-ion batteries assembled with the positive electrode materials prepared in Examples 1-7 have higher capacity performance, rate performance and cycle performance.

The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims (16)

1. A nickel-manganese binary precursor, characterized in that the precursor has a composition shown in formula I, Ni _x Mn _y M _z (OH) ₂ (I), 0.8≤x＜1, 0＜y≤ 0.2, 0≤z≤0.1, and x+y+z=1, M is selected from at least one non-Co element; Wherein, in the powder X-ray diffraction measurement of the precursor using CuKα rays, 2θ has a characteristic double peak of the 001 crystal plane within the range of 19±1.5°. 2. The precursor according to claim 1, wherein, in formula I, 0.85≤x≤0.99, 0.01≤y≤0.15, 0.001≤z≤0.1, and x+y+z=1, M is selected from La, At least one element of Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B, Y and Al; And/or, in formula I, 0.9≤x≤0.98, 0.02≤y≤0.1, 0.001≤z≤0.01, and x+y+z=1, M is selected from La, Cr, Mo, Hf, Ti, Zn, At least one element of Y, Zr, W, Nb, V, Mg, B, Y and Al. 3. The precursor according to claim 1 or 2, wherein, in the powder X-ray diffraction measurement of the precursor using CuKα rays, the peak intensity ratio of the characteristic peak of the 101 crystal plane and the characteristic double peak of the 001 crystal plane satisfies : I ₍₁₀₁₎ /I ₍₀₀₁₎ ≥ 1.5, the characteristic peak 2θ of the 101 crystal plane is in the range of (37-41)°; Preferably, it satisfies: 1.5≤I ₍₁₀₁₎ /I ₍₀₀₁₎ ≤3. 4. the precursor according to any one of claims 1-3, wherein, the peak intensity I ₍₁₀₁₎ of the characteristic doublet of the 001 crystal plane is 300-4000, and the half-maximum width FWHM ₍₁₀₁₎ is ( 0.5-2)°; And/or, the peak intensity I ₍₁₀₁₎ of the characteristic doublet of the 001 crystal plane is 500-3000, and the half-maximum width FWHM ₍₁₀₁₎ is (0.6-1.8)°. 5. The precursor according to any one of claims 1-4, wherein the characteristic bimodal of the 001 crystal plane includes unimodal A and unimodal B, and the unimodal A is located in the unimodal B the left side of Preferably, the peak intensity of the unimodal A and unimodal B satisfies: 500≤I _(A) ≤2000, _{600≤I (B)} ≤2000, 0.35≤I _(A)/ I _(B) ≤2.4; Preferably, the half-height widths of the unimodal A and unimodal B satisfy: 0.4°≤FWHM _(A) ≤0.7°, 0.4°≤FWHM _(B) ≤0.6°, 0.7≤FWHM _(A) /FWHM _{(B )} ≤ 1.5; Preferably, the peak areas of the unimodal A and unimodal B satisfy: 10000≤A _(A) ≤70000, _{10000≤A (B)} ≤75000, 0.6≤A _(A) /A _(B) ≤2.2. 6. The precursor according to any one of claims 1-5, wherein the precursor is a secondary particle composed of a primary particle, and the primary particle has a wedge-shaped structure; And/or, the precursor has a spherical structure; And/or, the BET of the precursor is 3-25m ² /g, preferably 5-20m ² /g; tap density ≥ 1g/cm ³ , preferably 1.3-2.5g/cm ³ ; And/or, the particle size distribution K ₉₀ of the precursor satisfies: 0.4≤K ₉₀ ≤0.8, wherein, K ₉₀ =(D ₉₀ -D ₁₀ )/D ₅₀ , D ₉₀ , D ₁₀ and D ₅₀ respectively refer to the The volume accumulation values of the precursors in the particle size distribution are respectively 90%, 10% and 50% of the particle size, and the unit is μm; And/or, the D ₅₀ of the precursor is 6-20 μm, preferably 8-14 μm. 7. A preparation method of a nickel-manganese binary precursor, characterized in that the preparation method comprises: mixing a mixed salt solution, a complexing agent and a precipitating agent and carrying out a co-precipitation reaction, and controlling the oxygen content in the reaction system to be 0.5 -10% by volume and a pH value of 10-11.3, the obtained co-precipitation reaction product is washed and dried in sequence to obtain a precursor; Wherein, the mixed salt solution is selected from an aqueous solution containing nickel salt, manganese salt and an optional M source, and in the M source, M is selected from at least one non-Co element. 8. The preparation method according to claim 7, wherein, regulating and controlling the oxygen content in the reaction system is 0.5-8% by volume; And/or, when the complexing agent is selected from compounds containing ammonium ions, the ammonia concentration in the reaction system is adjusted to be 1-12g/L, preferably 3-8g/L; And/or, the conditions of the co-precipitation reaction include: the temperature is 50-80°C, the pH value is 10-11.3, preferably 10.3-11.1; the rotation speed is 250-750rpm; And/or, in terms of metal elements, the nickel salt, manganese salt and M source satisfy n(Ni):n(Mn):n(M), 0.8≤n(Ni)<1, 0<n(Mn) ≤0.2, 0≤n(M)≤0.1; further preferably, 0.85≤n(Ni)≤0.99, 0.01≤n(Mn)≤0.15, 0.001≤n(M)≤0.1; more preferably, 0.9≤n (Ni)≤0.98, 0.02≤n(Mn)≤0.1, 0.001≤n(M)≤0.01; And/or, M in the M source is selected from La, Cr, Mo, Ca, Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B, Y and Al At least one element, preferably at least one element selected from La, Cr, Mo, Hf, Ti, Zn, Y, Zr, W, Nb, V, Mg, B, Y and Al; And/or, the feed flow rate of the mixed metal salt is 50-300mL/min, preferably 150-250mL/min; And/or, the washing process includes: alternately performing alkali washing and water washing on the co-precipitation reaction product; And/or, the drying conditions include: the temperature is 80-150° C., and the time is 2-6 hours. 9. The application of the precursor according to any one of claims 1-6, or the precursor prepared by the preparation method according to claim 7 or 8, in positive electrode materials. 10. A positive electrode material, characterized in that the positive electrode material is made of the precursor according to any one of claims 1-6, or the precursor prepared by the preparation method according to claim 7 or 8, after Made by sintering. 11. The positive electrode material according to claim 10, wherein the positive electrode material is prepared by the following method: in an oxygen-containing atmosphere, when the precursor does not contain the doping element M, the precursor, lithium source and M source are mixed and sintered to obtain the positive electrode material; or, When the precursor contains a doping element M, mixing the precursor and a lithium source and performing the sintering to obtain the positive electrode material; Wherein, M in the M source is selected from at least one non-Co element. 12. The positive electrode material according to claim 11, wherein the dosage ratio of the lithium source satisfies 0.9≤[n(Li)]/[n(Ni)+n(Mn)+n(M)]≤1.2; Preferably satisfy 1≤[n(Li)]/[n(Ni)+n(Mn)+n(M)]≤1.1; More preferably satisfy 1.01≤[n(Li)]/[n(Ni)+n(Mn)+n(M)]≤1.06; And/or, the amount of the M source satisfies: 0≤[n(M)]/[n(Ni)+n(Mn)+n(M)]≤0.1, and further preferably satisfies: 0.001≤[n(M) )]/[n(Ni)+n(Mn)+n(M)]≤0.1, more preferably satisfying: 0.001≤[n(M)]/[n(Ni)+n(Mn)+n(M) ]≤0.01; And/or, at least one of the M sources selected from Al, Fe, Mg, B, Ca, Sr, Ba, Zr, Ti, Ce, Y, W, La, Nb, Ta, Zn, Co and Mo elements, preferably at least one element selected from La, Cr, Mo, Hf, Ti, Zn, Y, Zr, W, Nb, V, Mg, B, Y and Al. 13. The cathode material according to claim 11 or 12, wherein the oxygen content in the oxygen-containing atmosphere is ≥80% by volume, preferably ≥95% by volume; And/or, the sintering conditions include: the temperature is 600-900°C, preferably 700-800°C; the time is 0.1-20h, preferably 0.1-15h; the heating rate is 1-20°C/min, preferably 1 -5°C/min. 14. The positive electrode material according to any one of claims 10-13, wherein the positive electrode material has a composition shown in formula II, Li _1+a Ni _α Mn _β M _γ O ₂ (II); Wherein, -0.1≤a≤0.2, 0.8≤α<1, 0<β≤0.2, 0≤γ≤0.1, and α+β+γ=1; M is selected from at least one non-Co element; Preferably, in formula II, 0≤a≤0.1, 0.85≤α≤0.99, 0.01≤β≤0.15, 0.001≤γ≤0.1, and α+β+γ=1; M is selected from La, Cr, Mo, Ca , Fe, Hf, Ti, Zn, Y, Zr, Si, W, Nb, Sm, V, Mg, B, Y and Al at least one element; Further preferably, in formula II, 0.01≤a≤0.06, 0.9≤α≤0.98, 0.02≤β≤0.1, 0.001≤γ≤0.01, and α+β+γ=1; M is selected from La, Cr, Mo, At least one element of Hf, Ti, Zn, Y, Zr, W, Nb, V, Mg, B, Y, and Al. 15. The positive electrode material according to any one of claims 10-14, wherein the tap density of the positive electrode material is ≥ 2.5 g/cm ³ , preferably 2.5-3 g/cm ³ ; And/or, the positive electrode material has a layered structure. 16. A lithium ion battery, characterized in that the lithium ion battery contains the positive electrode material according to any one of claims 10-15.