Agglomerated multi-element cathode material, preparation method thereof, application thereof and lithium ion battery

Abstract

The present invention discloses a kind of agglomerated multi-element cathode material and its preparation method, application and lithium ion battery. a Ni x Co y Mn z M b O2; 0.9≤a≤1.1, 0.5≤x<1, 0<y<0.5, 0<z<0.5, 0≤b<0.05; M is at least one of V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, Ba, Ra, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, Sr and Ti; it is a secondary particle formed by agglomeration of primary particles; the primary particles are spherical or quasi-spherical; the average particle size of the primary particles is D S The average particle size of secondary particles is 0.9-2.4 μm; L 5‑15 μm; D L / D S The value range is 5-16. It has high energy density, excellent rate performance and cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to an agglomerated multi-element positive electrode material and a preparation method thereof, and a lithium ion battery. Background Art

[0002] In recent years, energy and environmental issues have received increasing attention. The development of new energy vehicles in the world started with hybrid power, and then gradually entered the battery-based era. Pure electric and plug-in hybrid vehicles have become the real policy support for new energy.

[0003] High safety and long driving range are the development trends of electric vehicles. To meet the increasing demands of electric vehicles, power lithium batteries must possess higher energy density and better cycle stability. Within the lithium battery industry chain, cathode materials represent the largest market share and highest output value. Their performance determines the battery's energy density, lifespan, and rate capability, making them a core, key material in lithium batteries.

[0004] Ternary materials have the characteristics of high energy density, good cycle stability and good safety. At present, the mainstream ternary materials in the market are agglomerated materials and single crystal materials. Agglomerated materials have good rate performance, but slightly poor cycle performance. Single crystal materials have good cycle performance, but small particle size, low production efficiency, and slightly poor rate performance.

[0005] In order to obtain positive electrode materials with high energy density and strong structural stability, it is necessary to rationally design the material structure while taking into account the material's energy density, rate performance and cycle stability.

[0006] Related technology discloses a micron-scale sheet-like single crystal structure agglomerate of a ternary positive electrode material and its preparation method, which first adopts an improved chemical coprecipitation method to prepare a micron-spherical precursor composed of tightly stacked nanosheets, and the D50 size of the precursor is between 6-8μm; then the above precursor is mixed with an appropriate amount of flux and lithium salt in turn; finally, two steps of high-temperature sintering are carried out in a high-temperature sintering furnace to finally obtain a ternary positive electrode material with a micron-scale sheet-like single crystal structure agglomerate. Although it can combine the advantages of both single crystal structure and agglomerate structure, the sheet The compressive strength of the single crystal structure is low, and the agglomerates formed by the sheet structure are difficult to form regular spheres. The primary particles are difficult to stack tightly and have weak bonding forces with each other. Fracture and slippage between primary particles are prone to occur during the production of battery poles, leading to structural collapse and poor cycle performance. In addition, the grain boundary gaps of the agglomerates stacked in the sheet structure are large, and the grain boundaries and surfaces are not protected by a coating with good ductility. During the battery cycle, the electrolyte can easily pass through the grain boundaries to reach the surface of the primary particles, causing the primary particles to be corroded by the electrolyte from the surface to the inside, resulting in a decrease in the cycle retention rate. Summary of the Invention

[0007] The purpose of the present invention is to overcome the problem that existing ternary cathode materials cannot take into account energy density, rate performance and cycle stability.

[0008] In order to achieve the above-mentioned object, the first aspect of the present invention provides a quasi-agglomerated multi-element positive electrode material, wherein the multi-element positive electrode material has a structure shown in Formula I:

[0009] Li a Ni x Co y Mn z M b O2 formula I;

[0010] In formula I, 0.9≤a≤1.1, 0.5≤x<1, 0<y<0.5, 0<z<0.5, 0≤b<0.05; M is at least one of V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, Ba, Ra, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, Sr and Ti;

[0011] The multi-element positive electrode material is a secondary particle formed by agglomeration of primary particles; wherein the primary particles are spherical or quasi-spherical; the average particle size D of the primary particles is S The average particle size D of the secondary particles is 0.9-2.4 μm; L 5-15μm; and D L / D S The value range is 5-16.

[0012] A second aspect of the present invention provides a method for preparing a quasi-agglomerated multi-element positive electrode material, the preparation method comprising:

[0013] (1) mixing a nickel source, a first cobalt source, a manganese source, a complexing agent, and a precipitant to perform a coprecipitation reaction to obtain a slurry; then aging, filter pressing, washing, and drying the slurry in sequence to obtain a nickel-cobalt-manganese ternary precursor;

[0014] (2) mixing the nickel-cobalt-manganese ternary precursor with a lithium source and performing a first high-temperature sintering, and then sequentially performing crushing and screening to obtain a quasi-agglomerated positive electrode material process product;

[0015] (3) The quasi-agglomerated positive electrode material process product is mixed with a second cobalt source for a second high-temperature sintering, and then crushed and sieved in sequence to obtain a quasi-agglomerated multi-element positive electrode material.

[0016] The third aspect of the present invention provides a quasi-agglomerated multi-element positive electrode material prepared by the preparation method described in the second aspect.

[0017] The fourth aspect of the present invention provides the use of the agglomerated multi-element positive electrode material described in the first aspect or the third aspect, or the preparation method described in the second aspect in a lithium-ion battery.

[0018] A fifth aspect of the present invention provides a lithium-ion battery, wherein the lithium-ion battery contains the quasi-agglomerated multi-element positive electrode material described in the first aspect or the third aspect.

[0019] Through the above technical solution, the present invention has the following advantages:

[0020] 1. The particle size of the primary particles of the agglomerated ternary cathode materials in the prior art is generally 0.2-0.6 μm, while the quasi-agglomerated multi-element cathode materials provided by the present invention are secondary particles formed by agglomeration of primary particles; wherein the primary particles are spherical or quasi-spherical, and are more densely packed, have strong bonding forces with each other, and have high compaction density. The secondary particles formed are also spherical or quasi-spherical. In the present invention, the morphological characteristics of the primary and secondary particles are conducive to improving the energy density and cycle performance of the battery; the average particle size D of the primary particles is 1.5-2.0 μm. S The size is 0.9-2.4 μm, which is close to the size of single-crystal ternary positive electrode materials.

[0021] Existing agglomerated ternary cathode materials are easily crushed during the electrode manufacturing process, and due to particle expansion and contraction during cycling, primary particles are easily separated, destroying the material structure and leading to a decrease in electrical performance. The agglomerated multi-element cathode material provided by the present invention can overcome the shortcomings of agglomerated materials, with stronger compressive resistance. Even if crushing occurs and primary particles separate from each other during cycling, the performance of the separated primary particles remains similar to that of single crystal materials, ensuring the stable electrical performance of the cathode material during cycling.

[0022] 2. In the agglomerated multi-element cathode material provided by the present invention, the average particle size D of the secondary particles is L The particle size is 5-15μm, which is close to that of agglomerated materials and larger than that of single crystal materials. After being made into pole pieces, the particles are more tightly bound than those of single crystal materials, resulting in better rate performance and requiring less conductive agent and binder, which is beneficial to increasing the proportion of active materials. The pole piece compaction density is also higher, which can improve the energy density of the battery.

[0023] 3. In the quasi-agglomerated multi-element positive electrode material provided by the present invention, the grain boundaries of the primary particles and the surfaces of the secondary particles are rich in Co, and the Co molar content of the center of the primary particle is defined as K1, the Co molar content of the grain boundaries of the primary particle is defined as K2, and the Co molar content of the surface of the secondary particle is defined as K3, K2-K1≥0.5%, and K3-K1≥1.5%. Since the primary particles of the multi-element positive electrode material of the present invention are relatively large, the grain boundary gaps between the primary particles are relatively large. After the quasi-agglomerated positive electrode material process product is coated with a cobalt-containing compound with strong ductility and then sintered at a high temperature, the cobalt element can not only be coated on the surface of the secondary particles, but also can enter the interior of the secondary particles along the grain boundaries of the primary particles and be enriched at the interface between the primary particles, thereby achieving the purpose of simultaneously coating the primary and secondary particles with cobalt elements. During the electrode sheet production and circulation process of the obtained multi-element positive electrode material, if the secondary particles are broken, or the electrolyte reaches the surface of the primary particles through the grain boundaries, the exposed primary particle surface is still protected by the coating layer, thereby improving the structural stability of the material, inhibiting the erosion of the electrolyte, and improving the cycle stability and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a SEM image of the agglomerated multi-element cathode material prepared in Example 1 of the present invention;

[0025] Figure 2 is a SEM image of the positive electrode material prepared in Comparative Example 1 of the present invention;

[0026] Figure 3 is a SEM image of the positive electrode material prepared in Comparative Example 2 of the present invention;

[0027] Figure 4 This is a cycle performance diagram of the positive electrode materials prepared in Example 1 of the present invention and Comparative Examples 1 and 2 at a 1C rate, wherein the test temperature is 45° C. and the voltage range is 3.0-4.3V. DETAILED DESCRIPTION

[0028] The endpoints of the ranges and any values ​​disclosed herein 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 endpoints of each range, the endpoints of each range and 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 to be specifically disclosed herein.

[0029] In the present invention, unless explicitly stated, “first” and “second” do not represent a sequence, nor do they limit the materials or operations. They are only used to distinguish between the materials or operations. For example, the “first” and “second” in “first cobalt source” and “second cobalt source” are only used to distinguish to indicate that they are not the same cobalt source; the “first” and “second” in “first high-temperature sintering” and “second high-temperature sintering” are only used to distinguish to indicate that they are not the same high-temperature sintering operation.

[0030] A first aspect of the present invention provides a quasi-agglomerated multi-element positive electrode material having a structure shown in Formula I:

[0031] Li a Ni x Co y Mn z M b O2 formula I;

[0032] In formula I, 0.9≤a≤1.1, 0.5≤x<1, 0<y<0.5, 0<z<0.5, 0≤b<0.05; M is at least one of V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, Ba, Ra, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, Sr and Ti;

[0033] The multi-element positive electrode material is a secondary particle formed by agglomeration of primary particles; wherein the primary particles are spherical or quasi-spherical; the average particle size D of the primary particles is S The average particle size D of the secondary particles is 0.9-2.4 μm; L 5-15μm; and D L / D S The value range is 5-16.

[0034] According to some embodiments of the present invention, the agglomerated multi-element cathode material is obtained by controlling the size of the primary particles and the secondary particles. L / D S The value range of makes the formed multi-element positive electrode material form a clustered type, which can combine the excellent performance of single crystal materials and clustered materials, and can take into account the high energy density, rate performance and cycle stability of the positive electrode material.

[0035] According to some embodiments of the present invention, preferably, the quasi-agglomerate multi-element cathode material has a spherical or quasi-spherical morphology. The morphology of the quasi-agglomerate multi-element cathode material is characterized using a scanning electron microscope (SEM).

[0036] According to some embodiments of the present invention, the grain boundaries of the primary particles and the surfaces of the secondary particles are rich in Co, and the Co molar content of the center of the primary particles is defined as K1, the Co molar content of the grain boundaries of the primary particles is defined as K2, and the Co molar content of the surfaces of the secondary particles is defined as K3, wherein K2-K1 ≥ 0.5%, preferably, K2-K1 ≥ 1%; and K3-K1 ≥ 1.5%, preferably, K3-K1 ≥ 3%. The "center" in the center of the primary particles does not refer to the exact center, but refers to the main body excluding the grain boundaries of the primary particles and the surfaces of the secondary particles.

[0037] The adoption of the above preferred embodiment is conducive to forming a uniform coating layer on the grain boundaries and the surface of secondary particles, improving the mobility of lithium ions, and inhibiting electrolyte corrosion, thereby improving the rate and cycle performance.

[0038] According to some embodiments of the present invention, preferably, in Formula I, 1≤a≤1.1, 0.0005≤b≤0.01.

[0039] According to some embodiments of the present invention, preferably, M is at least one of Mg, W, V, Ti, La, Nb, Si, Al and B.

[0040] According to some embodiments of the present invention, preferably, the average particle size D of the primary particles is S 1.2-1.8μm.

[0041] According to some embodiments of the present invention, preferably, the average particle size D of the secondary particles is L 7-13μm.

[0042] According to some embodiments of the present invention, preferably, D L / D S The value range is 7-12.

[0043] The above preferred embodiment is used to set D S The Ds is 1.2-1.8 μm. If Ds is greater than 1.8 μm, the primary particles are too large, which will lead to poor rate performance of the material and the product performance will tend to be single crystal material. If Ds is less than 1.2 μm, the primary particles are too small, the structural stability is poor, the cycle performance is poor, and the product performance will tend to be agglomerated material. The above preferred embodiment is used to set Ds. L is 7-13μm, if D L If the secondary particles are larger than 13 μm, the lithium ion mobility will decrease and the rate will deteriorate. L If the secondary particles are smaller than 7 μm, the compaction density will be low, which will lead to a decrease in energy density and poor cycle performance. L / D SThe value range is 7-12. If D L / D S If it is greater than 12, there will be too many primary particles in the secondary particles, which will form more grain boundaries, the compressive performance of the material will be reduced, the product performance will tend to agglomerate, and the pole piece will be easy to crack during the production process. L / D S If it is less than 7, there will be fewer primary particles in the secondary particles, fewer grain boundaries will be formed, the contact area between the electrolyte and the positive electrode material will be smaller, and the material capacity will be reduced.

[0044] According to some embodiments of the present invention, the average particle size D of the primary particles is S The average particle size D of the secondary particles L The particle size is measured by scanning electron microscopy (SEM), and can be obtained by any graphic analysis software or manual measurement, and the data statistics can be obtained by any statistical software.

[0045] According to some embodiments of the present invention, the grain boundaries of the primary particles and the surfaces of the secondary particles are rich in Co. Preferably, when the content of the Co coating in the agglomerated multi-element positive electrode material is the same, D L / D S The larger the D is, the lower the Co content of the grain boundaries of the primary particles is, and the higher the Co content of the surface of the secondary particles is; L / D S The smaller the particle size, the higher the Co content in the grain boundaries of the primary particles and the lower the Co content on the surfaces of the secondary particles.

[0046] According to some embodiments of the present invention, preferably, the BET specific surface area of ​​the agglomerated multi-element cathode material is 0.1-0.4 m 2 / g, preferably 0.2-0.3m 2 The BET specific surface area of ​​the agglomerated multi-element cathode material was measured by using a Tristar 3020 surface area analyzer from Micromeritics.

[0047] According to some embodiments of the present invention, preferably, the half-maximum width (FWHM) of the characteristic peak of the XRD test (104) of the agglomerated multi-element positive electrode material is (104) The value range of is 0.19-0.23, preferably 0.2-0.22. The half maximum width FWHM of the agglomerated multi-element positive electrode material (104) The results were obtained by using the Smart Lab 9KW X-ray diffractometer of Rigaku Corporation of Japan, where the half-peak width (FWHM) (104)Specifically, it refers to the half-peak width of the (104) crystal plane of the agglomerated multi-element positive electrode material. The above value range indicates that the performance characterized by the XRD of the agglomerated multi-element positive electrode material has the properties of a single crystal.

[0048] According to some embodiments of the present invention, preferably, the D of the agglomerated multi-element cathode material 50 The D of the agglomerated multi-element positive electrode material is 5-15 μm, preferably 7-13 μm. 50 Obtained by laser particle size analyzer test.

[0049] A second aspect of the present invention provides a method for preparing a quasi-agglomerated multi-element positive electrode material, the preparation method comprising:

[0050] (1) mixing a nickel source, a first cobalt source, a manganese source, a complexing agent, and a precipitant to perform a coprecipitation reaction to obtain a slurry; then aging, filter pressing, washing, and drying the slurry in sequence to obtain a nickel-cobalt-manganese ternary precursor;

[0051] (2) mixing the nickel-cobalt-manganese ternary precursor with a lithium source and performing a first high-temperature sintering, and then sequentially performing crushing and screening to obtain a quasi-agglomerated positive electrode material process product;

[0052] (3) The quasi-agglomerated positive electrode material process product is mixed with a second cobalt source for a second high-temperature sintering, and then crushed and sieved in sequence to obtain a quasi-agglomerated multi-element positive electrode material.

[0053] It should be noted that, in the present invention, the cobalt introduced by the first cobalt source is Co 1 Indicates that the cobalt introduced by the second cobalt source is Co 2 To indicate, to distinguish.

[0054] According to some embodiments of the present invention, in step (1), the pH value of the coprecipitation reaction is 10-13. A high pH value of the coprecipitation reaction results in fine primary fibers, a large BET value of the precursor, easy fusion during subsequent sintering, and a cathode material with larger primary particles. Conversely, a low pH value of the coprecipitation reaction results in coarse primary fibers, a small BET value of the precursor, difficulty fusion during subsequent sintering, and a cathode material with smaller primary particles.

[0055] According to some embodiments of the present invention, preferably, in step (1), the BET of the nickel-cobalt-manganese ternary precursor is 7-14m 2 / g.

[0056] According to some embodiments of the present invention, preferably, in step (1), the coprecipitation reaction conditions further include: temperature of 40-80° C., time of 5-40 h, and rotation speed of 300-900 rpm.

[0057] According to some embodiments of the present invention, preferably, in step (1), the D of the nickel-cobalt-manganese ternary precursor is 50 5-15 μm, preferably 7-13 μm.

[0058] According to some embodiments of the present invention, preferably, in step (1), the nickel source, the first cobalt source and the manganese source are each independently selected from at least one of sulfates, chlorides, nitrates and acetates. For example, the nickel source can be selected from at least one of nickel sulfate, nickel chloride, nickel nitrate and nickel acetate; the first cobalt source can be selected from at least one of cobalt sulfate, cobalt chloride, cobalt nitrate and cobalt acetate; and the manganese source can be selected from at least one of manganese sulfate, manganese chloride, manganese nitrate and manganese acetate.

[0059] According to some embodiments of the present invention, preferably, in step (1), the mixing step comprises: passing a mixed salt solution containing the nickel source, the first cobalt source, and the manganese source, the complexing agent, and the precipitant into the reactor in a parallel flow manner. More preferably, the concentration of the mixed salt solution is 2-3 mol / L. The mixed salt solution can be commercially available or prepared according to conventional methods in the art, and there is no particular limitation on this. Further preferably, the mixing is carried out under the protection of an inert gas.

[0060] According to some embodiments of the present invention, in step (1), the precipitant can be any precipitant known in the art and suitable for preparing a nickel-cobalt-manganese ternary precursor, without particular limitation, as long as the precipitant can achieve the purpose of the present invention to a certain extent. Preferably, the precipitant is selected from sodium hydroxide and / or potassium hydroxide. More preferably, the precipitant is provided in the form of an aqueous precipitant solution, wherein the concentration of the aqueous precipitant solution is 5-10 mol / L.

[0061] According to some embodiments of the present invention, in step (1), the complexing agent can be any complexing agent known in the art and suitable for preparing a nickel-cobalt-manganese ternary precursor, without particular limitation, provided that the present invention can achieve the object of the present invention to a certain extent. Preferably, the complexing agent is selected from at least one of aqueous ammonia, disodium edetate, ammonium nitrate, ammonium chloride, and ammonium sulfate. More preferably, the complexing agent is provided in the form of an aqueous solution of the complexing agent, wherein the mass fraction of the aqueous solution of the complexing agent is 20-30%.

[0062] According to some embodiments of the present invention, in step (1), there is no particular limitation on the amount of the precipitant and the complexing agent, as long as the amount of the precipitant and the complexing agent are such that the coprecipitation reaction meets the precursor growth requirements.

[0063] According to some embodiments of the present invention, in step (1), the aging, filter pressing, washing, and drying can be performed using conventional methods well known to those skilled in the art, without particular limitation.

[0064] According to some embodiments of the present invention, preferably, in step (2), the temperature of the first high-temperature sintering is defined as T, and the value range of T satisfies Formula II:

[0065]

[0066] The preferred value range of T satisfies Formula III:

[0067]

[0068] Among them, C Ni is the molar percentage of nickel in the mixture consisting of the nickel source, the first cobalt source and the manganese source; D L The definition and numerical range of can be selected with reference to the above, and will not be repeated here.

[0069] According to some embodiments of the present invention, preferably, in step (2), the temperature of the first high-temperature sintering is high, then D L / D S Too small; the temperature of the first high temperature sintering is low, then D L / D S Too big.

[0070] According to some embodiments of the present invention, preferably, in step (2), the first high-temperature sintering conditions further include: a sintering time of 10-30 hours, and a sintering atmosphere provided by an oxygen-containing gas. Preferably, the oxygen content in the oxygen-containing gas is 1-100 vol%.

[0071] According to some embodiments of the present invention, preferably, in step (2), the D of the agglomerated cathode material process product is 50 5-15 μm, preferably 7-13 μm.

[0072] According to some embodiments of the present invention, the D of the nickel-cobalt-manganese ternary precursor 50 D of the agglomerated cathode material process product 50 Obtained by laser particle size analyzer test.

[0073] According to some embodiments of the present invention, preferably, in step (2), the amount of the lithium source satisfies the following stoichiometric ratio: 0.9≤[n(Li)] / [n(Ni)+n(Co 1 )+n(Mn)]≤1.1, preferably satisfying: 1.02≤[n(Li)] / [n(Ni)+n(Co 1)+n(Mn)]≤1.06.

[0074] According to some embodiments of the present invention, in step (2), the lithium source can be any lithium source known in the art for preparing positive electrode materials, without particular limitation, as long as the lithium source can achieve the objectives of the present invention to a certain extent. Preferably, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide, lithium oxide, and lithium acetate.

[0075] According to some embodiments of the present invention, in step (2), the crushing and screening process can be carried out by conventional methods well known to those skilled in the art, and there is no particular limitation on this, as long as D 50 The agglomerated positive electrode material process product that meets the above requirements will suffice.

[0076] According to some embodiments of the present invention, preferably, in step (3), the conditions for the second high-temperature sintering include: a temperature of 200-1000°C, a time of 5-20 hours, and a sintering atmosphere provided by an oxygen-containing gas. Preferably, the oxygen content in the oxygen-containing gas is 1-100 vol%.

[0077] According to some embodiments of the present invention, preferably, in step (3), the second cobalt source is selected from at least one of cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide, cobalt fluoride, cobaltous hydroxide, cobalt trioxide, cobalt carbonate, and cobalt acetate, and is preferably at least one of cobalt oxide, cobalt hydroxide, cobaltous oxide, cobaltous hydroxide, and cobaltous hydroxide. The above preferred embodiment is advantageous for achieving uniform coating and controlling surface residual alkali.

[0078] According to some embodiments of the present invention, preferably, in step (3), according to the stoichiometric ratio, the amount of the second cobalt source satisfies: 0.005≤[n(Co 2 )] / [n(Ni)+n(Co 1 )+n(Mn)]≤0.1, preferably satisfying: 0.01≤[n(Co 2 )] / [n(Ni)+n(Co 1 )+n(Mn)]≤0.06.

[0079] According to some embodiments of the present invention, the amounts of the first cobalt source and the second cobalt source are such that the total content of Co in the agglomerated multi-element positive electrode material satisfies: n(Ni):n(Co):n(Mn)=x:y:z, wherein n(Co)=n(Co 1 )+n(Co 2 ), the values ​​of x, y, and z can be defined and selected as above and will not be repeated here.

[0080] According to some embodiments of the present invention, preferably, in step (3), the D of the agglomerated multi-element cathode material 50 5-15 μm, preferably 7-13 μm.

[0081] According to some embodiments of the present invention, in step (3), the crushing and screening process can be carried out by conventional methods well known to those skilled in the art, and there is no particular limitation on this, as long as D 50 Any agglomerated multi-element positive electrode material that meets the above requirements will suffice.

[0082] According to some embodiments of the present invention, preferably, the mixed raw materials in step (1) further include additives.

[0083] According to some embodiments of the present invention, preferably, the mixed raw materials in step (2) further include a dopant.

[0084] According to some embodiments of the present invention, preferably, the mixed raw materials in step (3) further include a coating agent.

[0085] According to some embodiments of the present invention, the additive, the dopant and the capping agent are the same or different, and are each independently selected from a compound containing M, preferably, selected from at least one of oxides, fluorides, hydroxides, oxyhydroxides, carbonates, nitrates, sulfates and acetates containing M.

[0086] According to some embodiments of the present invention, preferably, the dopant is selected from at least one of MgO, WO3, TiO2, Nb2O5 and Al2O3.

[0087] According to some embodiments of the present invention, preferably, the coating agent is selected from at least one of V2O5, La2O3, SiO2 and B2O3.

[0088] According to some embodiments of the present invention, preferably, the amount of the additive satisfies: the molar fraction of the additive calculated as M element to the total molar amount of Ni, Co, and Mn is 0.01%-3%.

[0089] According to some embodiments of the present invention, preferably, the amount of the dopant satisfies: the molar fraction of the dopant calculated as M element to the total molar amount of Ni, Co, and Mn is 0.01%-3%.

[0090] According to some embodiments of the present invention, preferably, the coating agent is used in an amount such that the molar fraction of the coating agent calculated as M element to the total molar amount of Ni, Co, and Mn is 0.01%-3%.

[0091] According to some embodiments of the present invention, the total amount of the additive, the dopant and the coating agent is such that in the obtained multi-element positive electrode material, n(Ni):n(Co):n(Mn):n(M)=x:y:z:b, wherein the values ​​of x, y, z, and b can be defined and selected with reference to the above and will not be repeated here.

[0092] According to some embodiments of the present invention, the agglomerated multi-element cathode material prepared by the preparation method has a structure shown in Formula I:

[0093] Li a Ni x Co y Mn z M b O2 formula I;

[0094] In formula I, 0.9≤a≤1.1, 0.5≤x<1, 0<y<0.5, 0<z<0.5, 0≤b<0.05; M is at least one of V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, Ba, Ra, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, Sr and Ti;

[0095] The multi-element positive electrode material is a secondary particle formed by agglomeration of primary particles; wherein the primary particles are spherical or quasi-spherical; the average particle size D of the primary particles is S The average particle size D of the secondary particles is 0.9-2.4 μm; L 5-15μm; and D L / D S The value range is 5-16.

[0096] The third aspect of the present invention provides a quasi-agglomerated multi-element positive electrode material prepared by the preparation method described in the second aspect.

[0097] The fourth aspect of the present invention provides the application of the agglomerated multi-element positive electrode material described in the first aspect or the third aspect, or the preparation method described in the second aspect in a lithium-ion battery.

[0098] A fifth aspect of the present invention provides a lithium-ion battery, wherein the lithium-ion battery contains the quasi-agglomerated multi-element positive electrode material described in the first aspect or the third aspect.

[0099] The present invention will be described in detail below by way of examples. In the following examples and comparative examples, unless otherwise specified, all raw materials are commercially available.

[0100] Unless otherwise specified, room temperature refers to 25±2°C.

[0101] In the following examples and comparative examples, the relevant parameters were obtained by testing using the following methods:

[0102] (1) Morphology test: obtained by scanning electron microscope S-4800 of Hitachi HITACHI, Japan;

[0103] (2) BET test: obtained by using Micromeritics' Tristar 3020 surface area analyzer;

[0104] (3) XRD test: obtained by using a Smart Lab 9KW X-ray diffractometer from Rigaku Corporation of Japan;

[0105] (4)D 50 Particle size test: obtained by testing with Marvern's Hydro 2000mu laser particle size analyzer;

[0106] (5) Electrochemical performance test:

[0107] In the following examples and comparative examples, the electrochemical performance of the multi-element positive electrode materials was tested using 2025 button cells.

[0108] The preparation process of 2025 button battery is as follows:

[0109] Pole sheet preparation: The multi-element positive electrode material, acetylene black and polyvinylidene fluoride (PVDF) were mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a mass ratio of 95:3:2 to form a uniform slurry. The slurry was coated on aluminum foil and dried at 120°C for 12 hours. It was then stamped with a pressure of 100 MPa to form a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm. The loading amount of the multi-element positive electrode material was 15-16 mg / cm 2 .

[0110] Battery Assembly: In an argon-filled glove box with water and oxygen contents less than 5 ppm, the positive electrode, separator, negative electrode, and electrolyte were assembled into 2025-type button cells and allowed to rest for 6 hours. The negative electrode used a 17 mm diameter, 1 mm thick lithium metal sheet; the separator used a 25 μm thick polyethylene porous membrane (Celgard 2325); and the electrolyte was a mixture of equal parts ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1 mol / L LiPF6.

[0111] Electrochemical performance test:

[0112] In the following examples and comparative examples, the electrochemical performance of 2025 button batteries was tested using a Shenzhen Xinweier battery testing system, and the charge and discharge current density at 0.1C was 200 mA / g.

[0113] The charge and discharge voltage range was controlled at 3.0-4.3V. At room temperature, the button battery was charged and discharged at 0.1C to evaluate the initial charge and discharge specific capacity and initial charge and discharge efficiency of the multi-electrode positive electrode material.

[0114] Cycling performance test: Control the charge and discharge voltage range to 3.0-4.3V. At a constant temperature of 45°C, charge and discharge the button battery twice at 0.1C, and then charge and discharge 80 times at 1C to evaluate the high-temperature capacity retention rate of the multi-element positive electrode material.

[0115] Rate performance test: Control the charge and discharge voltage range to 3.0-4.3V. At room temperature, the button cell was cycled twice at 0.1C, and then once at 0.2C, 0.33C, 0.5C, and 1C. The rate performance of the multi-element cathode material was evaluated by the ratio of the 0.1C initial discharge capacity to the 1C discharge capacity. The 0.1C initial discharge capacity refers to the discharge capacity of the button cell after the first cycle, and the 1C discharge capacity refers to the discharge capacity of the button cell after the sixth cycle.

[0116] Example 1

[0117] (1) A nickel source, a first cobalt source, a manganese source, a complexing agent, and a precipitant are mixed to perform a coprecipitation reaction to obtain a slurry; the slurry is then aged, filtered, washed, and dried in sequence to obtain a nickel-cobalt-manganese ternary precursor; wherein:

[0118] The nickel source is nickel sulfate; the first cobalt source is cobalt sulfate; the manganese source is manganese sulfate; the complexing agent is provided in the form of a complexing agent aqueous solution, which is 25% by mass of ammonia water; the precipitant is provided in the form of a precipitant aqueous solution, which is 8 mol / L NaOH aqueous solution;

[0119] The mixing step is specifically as follows: under the protection of nitrogen, the aqueous solution containing the nickel source, the first cobalt source, the manganese source, the complexing agent aqueous solution and the precipitant aqueous solution are introduced into the reactor in a parallel flow manner, wherein Ni:Co 1 : The molar ratio of Mn is shown in Table 1;

[0120] The coprecipitation reaction conditions include: temperature 60°C, time 20 h, and rotation speed 800 rpm; the pH value of the coprecipitation reaction is shown in Table 1;

[0121] The chemical formula composition, BET and D 50 See Table 2.

[0122] (2) mixing the nickel-cobalt-manganese ternary precursor with a lithium source and a dopant, performing a first high-temperature sintering, and then sequentially performing crushing and screening to obtain a quasi-agglomerated positive electrode material process product; wherein:

[0123] The lithium source is lithium hydroxide; the types of dopants and the molar ratios of the raw materials are shown in Table 1;

[0124] The conditions for the first high-temperature sintering include: a sintering time of 18 hours, an oxygen atmosphere; the temperature of the first high-temperature sintering is shown in Table 1; the product of the first high-temperature sintering is naturally cooled to room temperature before crushing and screening;

[0125] The chemical formula composition and D 50 See Table 2.

[0126] (3) mixing the quasi-agglomerated positive electrode material in-process with a second cobalt source and performing a second high-temperature sintering, and then sequentially performing crushing and screening to obtain a quasi-agglomerated multi-element positive electrode material; wherein:

[0127] The type of the second cobalt source and the molar ratio of each raw material are shown in Table 1;

[0128] The conditions for the second high-temperature sintering include: a temperature of 720° C., a time of 10 hours, and an oxygen atmosphere; and the product of the second high-temperature sintering is naturally cooled to room temperature before being crushed and screened.

[0129] The chemical formula composition and D 50 See Table 2.

[0130] Examples 2-5

[0131] The method of Example 1 was followed, except that different raw materials and process parameters were used, as shown in Table 1. The remaining parameters were the same as in Example 1, and a quasi-agglomerated multi-element cathode material was prepared. The chemical formula composition and characteristic parameter test data of each product are shown in Table 2.

[0132] Comparative Example 1

[0133] A positive electrode material was prepared according to the method of Example 1, except that in step (1), the pH value of the coprecipitation reaction was 11.2; in step (2), the temperature of the first high-temperature sintering was 790°C; and all other procedures were the same as in Example 1. The chemical formula composition and characteristic parameter test data of each product are shown in Table 2.

[0134] Comparative Example 2

[0135] A positive electrode material was prepared according to the method of Example 1, except that in step (1), the pH value of the coprecipitation reaction was 13.2; in step (2), the temperature of the first high-temperature sintering was 970°C; and all other procedures were the same as in Example 1. The chemical formula composition and characteristic parameter test data of each product are shown in Table 2.

[0136] Comparative Example 3

[0137] The method of Example 1 was followed, except that step (3) was omitted. The remaining steps were the same as in Example 1, and the quasi-agglomerated cathode material product was directly used as the cathode material. The chemical formula composition and characteristic parameter test data of each product are shown in Table 2.

[0138] Table 1

[0139]

[0140]

[0141] Note: The ratio of each element is calculated in molar ratio

[0142] Test Case

[0143] (1) Morphology test

[0144] The present invention tested the scanning electron microscope (SEM) images of the positive electrode materials prepared in the above embodiments and comparative examples, wherein: Figure 1 This is a SEM image of the agglomerated multi-element cathode material prepared in Example 1 of the present invention; Figure 2 is a SEM image of the positive electrode material prepared in Comparative Example 1 of the present invention; Figure 3 This is an SEM image of the positive electrode material obtained in Comparative Example 2 of the present invention. It can be seen from the figure that the primary particles in the positive electrode material obtained in Example 1 are larger than those in the agglomerated type in Comparative Example 1 and smaller than those in the single crystal type in Comparative Example 2. The gaps between the primary particles in the positive electrode material obtained in Example 1 are larger, and the secondary particles are rounded and spherical.

[0145] (2) Physical property testing

[0146] The present invention tested the D of the positive electrode materials prepared in the above examples and comparative examples. 50 , BET, XRD (full width at half maximum FWHM (104) ), average particle size D of primary particles S and the average particle size D of the secondary particles L The specific test results are shown in Table 2.

[0147] Table 2

[0148]

[0149] Note: Precursor* is nickel-cobalt-manganese ternary precursor; process product** is agglomerated cathode material process product; cathode material*** is

[0150] Note: Precursor* is nickel-cobalt-manganese ternary precursor; process product** is quasi-agglomerated positive electrode material process product; positive electrode material*** is the quasi-agglomerated multi-element positive electrode material prepared in the example or the positive electrode material prepared in the comparative example.

[0151] Table 2 (continued)

[0152]

[0153]

[0154] Note: Precursor* refers to nickel-cobalt-manganese ternary precursor; process product** refers to quasi-agglomerated cathode material process product; cathode material*** refers to quasi-agglomerated multi-element cathode material.

[0155] From the results in Table 1 and Table 2, it can be seen that in the preparation process of agglomerated multi-element cathode materials, the FWHM of the cathode materials increases with the increase of the sintering temperature. (104) As the temperature rises, the average size of the primary particles increases. When the primary particles grow to a certain size, they separate from each other and become independent particles.

[0156] D of the positive electrode material of Comparative Example 1 L / D S Large, for the agglomerated material, comparative example 2 is a single crystal material, the FWHM of the agglomerated multi-element positive electrode material of the present invention is (104) Between single crystal material and agglomerated material, it is close to single crystal material.

[0157] (3) Composition test

[0158] The present invention tested the Ni, Co, and Mn compositions at the center of the primary particles, the grain boundaries of the primary particles, and the surfaces of the secondary particles of the positive electrode materials prepared in the above examples and comparative examples to obtain the differences in Co content. The specific test results are shown in Table 3. The Ni, Co, and Mn compositions are the average results of multiple point tests.

[0159] Table 3 (Total content of Ni, Co, and Mn is 100 mol%)

[0160]

[0161]

[0162] It can be seen from Table 3 that if the primary particles in the positive electrode material are large, the grain boundaries between the primary particles will be larger, and more Co will enter the grain boundaries. If the primary particles are small, Co will not easily enter the grain boundaries, and most of it will be coated on the surface of the secondary particles of the material.

[0163] (4) Electrochemical performance test

[0164] The present invention tested the electrochemical properties of the positive electrode materials prepared in the above embodiments and comparative examples, including 0.1C first discharge specific capacity, 1C discharge specific capacity, rate performance and cycle performance. The specific test results are shown in Table 4; wherein, the test temperature of the discharge specific capacity at a 1C rate is 25°C.

[0165] Table 4

[0166] project First discharge specific capacity Discharge specific capacity Rate performance Capacity retention rate unit 0.1C / mAh / g 1.0C / mAh / g 1.0C / 0.1C 45℃ cycle 80 times / % Example 1 202.1 187.3 0.927 95.4 Example 2 202.5 187.2 0.924 94.3 Example 3 201.5 185.7 0.922 96.1 Example 4 203.2 186.2 0.916 93.6 Example 5 218.5 201.8 0.924 91.1 Comparative Example 1 201.1 184.3 0.916 89.2 Comparative Example 2 196.8 179.5 0.912 94.6 Comparative Example 3 200.2 181.4 0.906 89.1

[0167] As can be seen from Table 4, the sintering temperature of Example 2 is lower than that of Example 1, the primary particles are smaller, the grain boundary Co is less than that of Example 1, the external Co is more, and the material circulation is poor;

[0168] The sintering temperature of Example 3 is higher than that of Example 1, the primary particles are larger, the grain boundary Co is more than that of Example 1, the external Co is less, and the material capacity ratio is slightly worse;

[0169] Example 4 has less Co coating than Example 1, less Co at the grain boundary and surface, poor material rate and poor cycle performance;

[0170] Comparative Example 1 is an agglomerated material with small primary particles and a compact structure. Co cannot enter the secondary particles along the grain boundaries. There is very little Co at the grain boundaries, resulting in poor material capacity and poor cycling.

[0171] Comparative Example 2 is a single crystal material, the primary particles are large, the primary particles are separated and independent from each other, Co is enriched on the surface of the material, and the material capacity ratio is poor;

[0172] Comparative Example 3 is not coated with Co, and the material rate and cycle performance are poor.

[0173] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A quasi-agglomerated multi-element positive electrode material, characterized in that: The multi-element positive electrode material has a structure shown in Formula I: Li a Ni x Co y Mn z M b O2 of formula I; In formula I, 0.9≤ a ≤1.1,0.5≤ x <1,0< y <0.5,0< z <0.5, 0≤ b <0.05; M is at least one of V, Ta, Cr, La, Al, Ce, Er, Ho, Y, Mg, Sr, Ba, Ra, Zr, Fe, Ca, Zn, B, W, Nb, Cd, Pb, Si, Mo, Cu, Sr and Ti; The multi-element positive electrode material is a secondary particle formed by agglomeration of primary particles; wherein the primary particles are spherical or quasi-spherical; the average particle size D of the primary particles is S The average particle size D of the secondary particles is 1.2-1.8 μm; L 7-13 μm; and D L / D S The value range is 7-12; the average particle size D L Measured by scanning electron microscopy; The grain boundaries of the primary particles and the surfaces of the secondary particles are rich in Co, and the Co molar content of the center of the primary particles is defined as K1, the Co molar content of the grain boundaries of the primary particles is defined as K2, and the Co molar content of the surface of the secondary particles is defined as K3, wherein K2-K1≥0.5% and K3-K1≥1.5%; The half-maximum width (FWHM) of the characteristic peak of the (104) XRD test of the agglomerated multi-element positive electrode material is (104) The value range is 0.202-0.

23.

2. The agglomerated multi-element cathode material according to claim 1, wherein K2-K1≥1%, K3-K1≥3%.

3. The agglomerated multi-element cathode material according to claim 1 or 2, wherein: In formula I, 1≤ a ≤1.1,0.0005≤ b ≤0.01; And / or, M is at least one of Mg, W, V, Ti, La, Nb, Si, Al and B.

4. The agglomerated multi-element cathode material according to claim 1 or 2, wherein: The BET specific surface area of ​​the agglomerated multi-element positive electrode material is 0.1-0.4 m 2 / g; And / or, D of the agglomerated multi-element cathode material 50 5-15μm.

5. The agglomerated multi-element cathode material according to claim 4, wherein: The BET specific surface area of ​​the agglomerated multi-element positive electrode material is 0.2-0.3 m 2 / g; And / or, D of the agglomerated multi-element cathode material 50 7-13μm.

6. A method for preparing the quasi-agglomerated multi-element positive electrode material according to any one of claims 1 to 5, characterized in that: The preparation method comprises: (1) mixing a nickel source, a first cobalt source, a manganese source, a complexing agent, and a precipitant to perform a coprecipitation reaction to obtain a slurry; then aging, filter pressing, washing, and drying the slurry in sequence to obtain a nickel-cobalt-manganese ternary precursor; (2) mixing the nickel-cobalt-manganese ternary precursor with a lithium source and performing a first high-temperature sintering, and then sequentially performing crushing and screening processes to obtain a quasi-agglomerated positive electrode material process product; The temperature of the first high-temperature sintering is defined as T, and the value range of T satisfies Formula II: Formula II; in, is the molar percentage of nickel in the mixture consisting of the nickel source, the first cobalt source and the manganese source; the average particle size D L Measured by scanning electron microscopy; (3) mixing the quasi-agglomerated positive electrode material in-process product with a second cobalt source and performing a second high-temperature sintering, and then sequentially crushing and screening to obtain a quasi-agglomerated multi-element positive electrode material; According to the stoichiometric ratio, the amount of the second cobalt source satisfies: 0.005≤[n(Co 2 )] / [n(Ni)+n(Co 1 )+n(Mn)]≤0.

1.

7. The preparation method according to claim 6, wherein In step (1), the pH value of the coprecipitation reaction is 11.8-13; And / or, the coprecipitation reaction temperature is 40-80°C, the time is 5-40h, and the rotation speed is 300-900rpm; And / or, the BET specific surface area of ​​the nickel-cobalt-manganese ternary precursor is 7-14 m 2 / g; And / or, the D of the nickel-cobalt-manganese ternary precursor 50 5-15μm.

8. The preparation method according to claim 7, wherein In step (1), the nickel-cobalt-manganese ternary precursor D 50 7-13μm.

9. The preparation method according to claim 6, wherein In step (2), the value range of T satisfies formula III: Formula III; And / or, the first high-temperature sintering time is 10-30 hours, and the sintering atmosphere is provided by an oxygen-containing gas; And / or, the D of the agglomerated cathode material process product 50 5-15μm; And / or, according to the stoichiometric ratio, the amount of the lithium source satisfies: 0.9≤[n(Li)] / [n(Ni)+n(Co 1 )+n(Mn)]≤1.

1.

10. The preparation method according to claim 9, wherein In step (2), the D of the agglomerated cathode material process product 50 7-13μm; And / or, according to the stoichiometric ratio, the amount of the lithium source satisfies: 1.02≤[n(Li)] / [n(Ni)+n(Co 1 )+n(Mn)]≤1.

06.

11. The preparation method according to any one of claims 6 to 10, wherein: In step (3), the conditions for the second high-temperature sintering include: a temperature of 200-1000°C, a time of 5-20 hours, and a sintering atmosphere provided by an oxygen-containing gas; and / or, the second cobalt source is selected from at least one of cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide, cobalt fluoride, cobaltous hydroxide, cobalt carbonate and cobalt acetate; And / or, according to the stoichiometric ratio, the amount of the second cobalt source satisfies: 0.01≤[n(Co 2 )] / [n(Ni)+n(Co 1 )+n(Mn)]≤0.

06.

12. The preparation method according to claim 11, wherein In step (3), the second cobalt source is selected from at least one of cobalt oxide, cobalt hydroxide, cobalt oxyhydroxide and cobaltous hydroxide.

13. The preparation method according to claim 11, wherein The second cobalt source is tricobalt tetroxide.

14. The preparation method according to any one of claims 6 to 10, wherein: The mixed raw materials in step (1) further include additives; and / or, the mixed raw materials in step (2) further include dopants; and / or, the mixed raw materials in step (3) further include coating agents; The additive, the dopant and the capping agent are the same or different and are independently selected from compounds containing M.

15. The preparation method according to claim 14, wherein The additive, the dopant and the coating agent are the same or different and are independently selected from at least one of oxides, fluorides, hydroxides, oxyhydroxides, carbonates, nitrates, sulfates and acetates containing M.

16. The preparation method according to claim 14, wherein The dopant is selected from at least one of MgO, WO3, TiO2, Nb2O5 and Al2O3; And / or, the coating agent is selected from at least one of V2O5, La2O3, SiO2 and B2O3.

17. An agglomerated multi-element positive electrode material prepared by the preparation method according to any one of claims 6 to 16.

18. Use of the quasi-agglomerated multi-element positive electrode material according to any one of claims 1 to 5 or 17 in a lithium-ion battery.

19. Use of the preparation method according to any one of claims 6 to 16 in lithium-ion batteries.

20. A lithium ion battery, characterized in that: The lithium-ion battery contains the agglomerated multi-element positive electrode material according to any one of claims 1 to 5 or 17.

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