Positive electrode material, method for producing the same, and lithium ion battery

Abstract

The present invention relates to the field of lithium-ion batteries, and discloses a positive electrode material, a manufacturing method thereof, and a lithium-ion battery. The micro residual stress measured by XRD of the positive electrode material is 0.01 - 0.15, the average diameter of the positive electrode material measured by SEM electron microscope is D, and the crystal grain diameter measured by XRD is R, where D / R is 1.4 - 2.5. Since the positive electrode material has a micro residual stress within a specific range and a ratio (D / R) of the average diameter to the crystal grain diameter within a specific range, it has significantly improved electrochemical performance and thermal stability.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries, and specifically to a positive electrode material, a method for manufacturing the same, and a lithium-ion battery.

Background Art

[0002] Power batteries are the energy source of electric vehicles, and battery performance is very important for the performance of new energy vehicles. As an important component of power batteries, the positive electrode material greatly affects the performance of the battery. During the production of the positive electrode material, the amount of residual alkali on the surface is often too large, the viscosity of the slurry increases during the homogenization process, and as a result, there is a jelly phenomenon, which is disadvantageous for the production of the battery and the exertion of its electrical performance. Compounds containing cobalt elements are one of the commonly used coating agents for positive electrode materials, and can effectively reduce the amount of residual alkali on the surface.

[0003] Compounds containing cobalt elements include many types such as lithium cobaltate, cobalt oxide, and tricobalt tetroxide. Compounds containing different types of cobalt elements may improve the electrical performance of the positive electrode material, and may also deteriorate its electrical performance.

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a positive electrode material, a method for manufacturing the same, and a lithium-ion battery, which have significantly improved electrochemical performance and thermal stability because they have a specific range of micro residual stress and a specific range of ratio (D / R) of average diameter to crystal grain diameter.

Means for Solving the Problems

[0005] To achieve the above object, a first aspect of the present invention provides a positive electrode material, wherein the micro residual stress of the positive electrode material measured by XRD is 0.01 - 0.15, The average diameter of the positive electrode material measured by an SEM electron microscope is D, and the crystal grain diameter measured by XRD is R. D / R is 1.4 - 2.5.

[0006] The second aspect of the present invention provides a method for manufacturing a positive electrode material, and the method includes: (1) mixing a positive electrode material precursor, a lithium source, and an optional G element-containing additive to obtain a mixture I; (2) sintering the mixture I for the first time in an atmosphere of air or oxygen to obtain a positive electrode material processed product II; (3) mixing the positive electrode material processed product II, the cobalt additive, and an optional M element-containing additive to obtain a mixture III; (4) sintering the mixture III for the second time in an atmosphere of air or oxygen to obtain the positive electrode material. The peak intensity ratio of the characteristic peak at 38.5° and the characteristic peak at 37.4° of the cobalt additive measured by XRD is 1:1.1 - 7.5. The constant temperature T1 of the first sintering is 1000°C or lower.

[0007] The third aspect of the present invention provides a positive electrode material manufactured by the above method.

[0008] The fourth aspect of the present invention provides a lithium-ion battery including the above positive electrode material.

Advantages of the Invention

[0009] By the above technical solution, the positive electrode material, its manufacturing method, and the lithium-ion battery according to the present invention obtain the following beneficial effects.

[0010] The positive electrode material according to the present invention has a specific range of micro residual stress and a specific range of ratio (D / R) of the average diameter to the crystal grain diameter, and thus has significantly improved electrochemical performance and thermal stability.

[0011] ​In the method for manufacturing a positive electrode material according to the present invention, by using a cobalt additive that contains cobalt oxyhydroxide and cobalt hydroxide simultaneously and has a specific XRD structure, particle size, and particle size distribution as a coating agent to manufacture the positive electrode material, lattice defects in the matrix of the positive electrode material can be compensated, and furthermore, the structural stability and electrochemical performance of the positive electrode material thus manufactured can be improved.

[0012] In addition, by using the cobalt additive of the present invention as a coating agent, it can be well coated on the particle surface of the positive electrode during the coating mixing process, and non-uniform coating and agglomeration of the coating agent do not occur.

[0013] Furthermore, compared with conventional single cobalt oxyhydroxide or cobalt hydroxide, by adopting the cobalt additive of the present invention, the electrochemical performance of the positive electrode material can be significantly improved. Therefore, the charge and discharge capacity, cycle retention rate, and safety performance of the lithium-ion battery using the positive electrode material are all improved.

[0014] In addition, the process of this method is simple and easy to mass-produce.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0016] The endpoints and any values within the scope disclosed in this specification should not be limited to such exact ranges or values, but should be understood to include values close to these ranges or values. In the case of numerical ranges, between the endpoint values of each range, between each endpoint value and a single point value, and between single point values, one or more new numerical ranges can be obtained by combining them with each other, and these numerical ranges are regarded as specifically disclosed in the specification.

[0017] The first aspect of the present invention provides a positive electrode material, and the micro residual stress of the positive electrode material measured by XRD is 0.01 - 0.15. The average diameter of the positive electrode material measured by SEM electron microscope is D, and the crystal grain diameter measured by XRD is R. It is characterized in that D / R is 1.4 - 2.5.

[0018] In the present invention, since the positive electrode material has a specific range of micro residual stress and a specific range of the ratio (D / R) of the average diameter to the crystal grain diameter, it has excellent electrochemical performance and thermal stability.

[0019] Specifically, in the present invention, when D / R in the positive electrode material satisfies the range limited in the present invention, it can keep the contact interface resistance between the positive electrode material particles and the contact area with the electrolyte and the conductive material within a reasonable range, and the crystal grains have good crystallinity and size, can keep the lithium ion diffusion channel smooth and shorten the diffusion distance, further improve the reaction rate, and finally the positive electrode material has low resistance and excellent initial charge-discharge efficiency.

[0020] Furthermore, in the present invention, the positive electrode material is manufactured into a finished product by coating sintering. Cobalt as a coating agent can supplement the lattice defects inside the positive electrode material, does not cause valence changes of nickel and manganese elements in the positive electrode material, can improve the stability of the material, and finally the positive electrode material has low micro residual stress, indicating that the positive electrode material has excellent structural stability and is not easy to crack during the manufacturing process.

[0021] In the present invention, the crystal grain diameter R of the positive electrode material is the crystal grain diameter calculated by the Rietveld analysis method from the powder X-ray diffraction pattern obtained by powder X-ray diffraction measurement using CuKα rays. The software for Rietveld analysis includes, but is not limited to, TOPAS, Rietan, JANA, JADE, etc.

[0022] In the present invention, the average particle diameter D of the positive electrode material is the average diameter of 300 typical particles in a scanning electron microscope photograph.

[0023] In the present invention, the micro residual stress of the positive electrode material is obtained by X-ray diffraction method test and finishing. The XRD test scanning range is 10° ≤ 2θ ≤ 90°, the scanning speed is 5° / min, and Topas finishing software and Pawley full spectrum fitting method are adopted.

[0024] Furthermore, the micro residual stress of the positive electrode material measured by XRD is 0.01 - 0.15.

[0025] Furthermore, D / R is 1.4 - 2.

[0026] According to the present invention, the average diameter D of the positive electrode material is 1 - 3 μm.

[0027] The inventor of the present invention found through research that the smaller the average diameter D of the positive electrode material, the smaller the single crystal particles of the positive electrode material, and the larger the D, the larger the single crystal particles of the positive electrode material. If the D value is too small, the degree of single crystallization decreases, the adhesion of single crystal particles increases, and as a result, single crystallization becomes difficult and approaches a polycrystalline structure, causing the positive electrode material to crack and powder during the cycle process, resulting in a sharp drop in the capacity cycle curve. If the D value is too high, the path for lithium ions to transport inside the particles increases, the lithium ion transport ability decreases, the impedance of its transport increases, the internal resistance of the battery increases, and the capacity decreases. In the present invention, when the average diameter of the positive electrode material satisfies the above range, it is ensured that the positive electrode material is prevented from cracking and powdering, and the positive electrode material has low impedance and high charge-discharge capacity.

[0028] Furthermore, the average diameter D of the positive electrode material is 1.5 - 2 μm.

[0029] According to the present invention, the crystal grain diameter R of the positive electrode material is 700 - 1200 nm.

[0030] In the present invention, when the crystal grain diameter R of the positive electrode material satisfies the above range, the purity and crystallinity of the crystal grains of the positive electrode material are high, and an appropriate diffusion channel can be provided for lithium ion diffusion, further reducing the resistance inside the single crystal particles. If the crystal grain diameter R is too large, the diffusion channel of lithium ions during charging and discharging becomes long, and the internal resistance of the single crystal particles tends to be high. If R is too small, the crystallinity and crystal purity of the positive electrode material particles are low, including an inactive crystal phase and an impurity phase without crystallinity, and the release and occlusion of lithium ions do not proceed smoothly, and the resistance tends to be high.

[0031] Furthermore, the crystal grain diameter R of the positive electrode material is 900 - 1000 nm.

[0032] In the present invention, when the micro residual stress and crystal grain size of the positive electrode material simultaneously satisfy the range defined in the present invention, it can be ensured that the positive electrode material has a high charge-discharge capacity and excellent cycle performance at the same time.

[0033] According to the present invention, the median diameter D50 of the positive electrode material is 3 - 4.5 μm.

[0034] According to the present invention, the mixed arrangement nickel content of the positive electrode material is 0 - 4 wt%.

[0035] In the present invention, the mixed arrangement nickel content refers to the proportion of Ni in which lithium-nickel mixing occurs 2+ occupying the total Ni, and can be measured by XRD finishing.

[0036] In the present invention, since the positive electrode material has a low mixed-array nickel content, it has high structural stability, and particularly at high voltages, it can effectively suppress the dissolution and structural destruction of the positive electrode active material particles, improving the chemical stability of the material and resulting in the effect of extending the battery cycle life.

[0037] Furthermore, the mixed-array nickel content of the positive electrode material is 0 - 3 wt%.

[0038] In a specific embodiment of the present invention, the positive electrode material is a cobalt-coated positive electrode material.

[0039] According to the present invention, the positive electrode material includes a matrix and a coating layer coated on the matrix. The matrix has a composition shown in Formula I. Li 1+a Ni x Mn y Co z G b O2 Formula I Here, -0.05 ≦ a ≦ 0.1, 0 ≦ b ≦ 0.05, 0.5 ≦ x < 1, 0 < y < 0.5, 0 ≦ z < 0.5, and G is selected from at least one of W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, Mg, and Y. The coating layer includes a lithium oxygen compound containing a cobalt element and / or an oxide containing a cobalt element. Optionally, the coating layer further includes a lithium oxygen compound containing an M element and / or an oxide containing an M element, and M is selected from at least one of B, Al, Nb, Mn, Mo, W, Si, Mg, Ti, and Zr.

[0040] Furthermore, in Formula I, 0.01 ≦ a ≦ 0.1, 0 ≦ b ≦ 0.005, 0.5 ≦ x < 1, 0 < y < 0.2, 0 ≦ z < 0.3, and G is selected from at least one of W, V, Ta, Zr, Sr, Si, and Y. M is selected from at least one of B, Al, W, Mg, Ti, and Zr.

[0041] In the present invention, in the case of a lithium oxygen compound containing an M element and a lithium oxygen compound containing a cobalt element, it contains at least one of Ni, Mn, and G in addition to the metal element M and Li, or Co and Li.

[0042] According to the present invention, between the molar amount n'(Co) of cobalt element in the coating layer, the molar amount n(M) of M element in the coating layer, and the total molar amount [n(Ni) + n(Co) + n(Mn) + n(G)] of metal elements other than Li in the matrix, 0.001 ≤ n'(Co):[n(Ni) + n(Co) + n(Mn) + n(G)] ≤ 0.05, 0 ≤ n(M):[n(Ni) + n(Co) + n(Mn) + n(G)] ≤ 0.05 is satisfied.

[0043] In the present invention, when the contents of the coating layer containing cobalt element and the coating layer containing M element in the positive electrode material satisfy the above range, the movement speed and transport efficiency of Li + can be improved, and furthermore, the electrical conductivity of the positive electrode material can be increased. The manufactured positive electrode material has higher reaction activity and utilization rate.

[0044] Furthermore, between the molar amount n'(Co) of cobalt element in the coating layer, the molar amount n(M) of M element in the coating layer, and the total molar amount [n(Ni) + n(Co) + n(Mn) + n(G)] of metal elements other than Li in the matrix, 0.01 ≤ n'(Co):[n(Ni) + n(Co) + n(Mn) + n(G)] ≤ 0.03, 0 ≤ n(M):[n(Ni) + n(Co) + n(Mn) + n(G)] ≤ 0.01 is satisfied.

[0045] According to the present invention, the residual alkali content of the positive electrode material is 1000 - 10000 ppm.

[0046] In the present invention, since the surface of the positive electrode material has a low residual alkali content and adopts a cobalt coating method, the positive electrode material has small volume change and thermal change during the reaction process. The thermal stability of the lithium ion battery containing the positive electrode material is improved, and the safety is enhanced.

[0047] Furthermore, the residual alkali content of the positive electrode material is 1000 - 6000 ppm.

[0048] In a specific embodiment of the present invention, when 0.5 ≦ x < 0.8, the residual alkali content of the positive electrode material is 1000 - 3000 ppm, preferably 2000 - 3000 ppm.

[0049] In a specific embodiment of the present invention, when 0.8 ≦ x < 1, the residual alkali content of the positive electrode material is 4000 - 6000 ppm, preferably 4000 - 5000 ppm.

[0050] In the present invention, as long as the positive electrode material has the characteristics described in the first aspect of the present invention, the lithium-ion battery containing the positive electrode material can have excellent electrochemical performance. Regarding the manufacturing method of the positive electrode material, as long as the positive electrode material described in the first aspect of the present invention can be manufactured, all belong to the protection scope of the present invention.

[0051] In the present invention, in order to further reduce the micro stress of the positive electrode material and the content of mixed array nickel and improve the thermal stability, etc., preferably, the second aspect of the present invention provides a method for manufacturing a positive electrode material, and the method includes: (1) mixing a positive electrode material precursor, a lithium source, and an optional G element-containing additive to obtain a mixture I; (2) sintering the mixture I for the first time in an atmosphere of air or oxygen to obtain a positive electrode material processed product II; (3) mixing the positive electrode material processed product II, the cobalt additive, and an optional M element-containing additive to obtain a mixture III; (4) sintering the mixture III for the second time in an atmosphere of air or oxygen to obtain the positive electrode material. The peak intensity ratio of the characteristic peak at 38.5° and the characteristic peak at 37.4° of the cobalt additive measured by XRD is 1:1.1 - 7.5. Here, the constant temperature T1 of the first sintering is 1000 °C or lower.

[0052] In the method for manufacturing a positive electrode material according to the present invention, a cobalt additive containing cobalt oxyhydroxide and cobalt hydroxide is used as a coating agent, and cobalt oxyhydroxide and cobalt hydroxide can be converted into each other. According to the change of potential and pH value, Co 2+ and Co 3+ achieve the dynamic equilibrium of ions and stabilize the performance of the coating layer under different environments. The cobalt additive has a specific XRD structure, particle size and particle size distribution, and can supplement the lattice defects in the positive electrode material matrix, thereby improving the structural stability and electrochemical performance of the finally obtained positive electrode material.

[0053] Specifically, the cobalt additive and the positive electrode material process product II are combined by a high-temperature solid-phase method to obtain a positive electrode material coated with a cobalt additive. At high temperature, cobalt hydroxide can reduce the residual alkali content on the surface of the positive electrode material, improve the homogenization efficiency, and at the same time, can improve the conductivity of the positive electrode material. The valence of cobalt in cobalt oxyhydroxide is +3, which is the same as the average valence of nickel cobalt manganese in the positive electrode material, can penetrate well into the material to supplement the lattice defects, does not cause valence changes of nickel and manganese elements in the material, plays a role in stabilizing the material, and reduces the micro residual stress of the positive electrode material.

[0054] In the present invention, by adjusting the content ratio of cobalt oxyhydroxide and cobalt hydroxide, the control of the peak intensity ratio of the peak at the 38.5° position and the peak at the 37.4° position in the XRD of the cobalt additive is realized. When the peak intensity ratio is within a specific range, by adding the cobalt additive as a coating agent to the positive electrode material, the electrochemical performance and thermal stability of the positive electrode material can be effectively improved.

[0055] In addition, when the cobalt additive of the present invention is used as a coating agent, it can wrap the surface of the positive electrode particles during the coating mixing process, and there is no coating non-uniformity or agglomeration phenomenon of the coating agent.

[0056] Furthermore, compared with the conventional single cobalt oxyhydroxide or cobalt hydroxide, the adoption of the cobalt additive of the present invention can greatly improve the electrochemical performance of the positive electrode material, and the charge and discharge capacity, cycle retention rate and safety performance of the lithium-ion battery including the positive electrode material are all improved.

[0057] In the present invention, when the constant temperature T1 of the first sintering is controlled to satisfy the above range, the growth of the crystal grains of the positive electrode material and the arrangement of the crystal grains of the positive electrode material can be promoted, grain boundaries and voids can be reduced, the spatial transport of electrons / ions can be smoothed, and the electrochemical performance can be improved. At the same time, the crystal structure of the material can be changed and optimized, and the material stability can be improved. It should be noted that the method has a simple process and is easy to mass-produce.

[0058] Furthermore, the peak intensity ratio of the characteristic peak at 38.5° and the characteristic peak at 37.4° of the cobalt additive measured by XRD is 1:2 - 4.5.

[0059] Furthermore, the constant temperature T1 of the first sintering is 700 - 1000 °C.

[0060] According to the present invention, the median diameter D (Co)50 of the cobalt additive is 0.5 - 5 μm, and the particle size distribution K (Co)90 =(D (Co)90 -D (Co)10 ) / D (Co)50 satisfies 0.8 ≤ K 90 ≤ 2.

[0061] In the present invention, the median diameter D (Co)50 and the particle size distribution K (Co)90By controlling to meet the scope defined in the present invention, the obtained cathode material has excellent electrochemical performance, while reducing production costs and realizing mass production. Specifically, if the powder particles of the cobalt additive are too large, the uniformity of the coating on the cathode material process product II will deteriorate, and as a result, it will be partially concentrated on the surface of the cathode material, and the cathode material will be partially exposed, further affecting the electrochemical performance of the product. If the powder particles are too small, more precise production equipment is required, and during production, the damage to the equipment will increase rapidly, the production cost will increase, and it will be disadvantageous for industrial mass production.

[0062] Furthermore, the median diameter D of the cobalt additive (Co)50 is 0.5 - 3 μm, and the particle size distribution K of the cobalt additive (Co)90 =(D (Co)90 -D (Co)10 ) / D (Co)50 satisfies 1 ≦ K (Co)90 ≦ 1.8.

[0063] In the present invention, the manufacturing method of the cobalt additive is not particularly limited, and it can be manufactured by conventional methods in this field. The obtained cobalt additive only needs to have a specific XRD structure defined in the present invention. Preferably, in the present invention, cobalt oxyhydroxide and cobalt hydroxide are mixed and pulverized to obtain a cobalt additive.

[0064] In the present invention, a mixture of cobalt oxyhydroxide and cobalt hydroxide can be pulverized by a conventional method in this field, such as a jet mill.

[0065] In the present invention, the respective usage amounts of cobalt oxyhydroxide and cobalt hydroxide and the pulverization conditions are not particularly limited, and the cobalt additive only needs to have the peak intensity ratio of the characteristic peak at 38.5° and the characteristic peak at 37.4°, the median diameter D 50 and the particle size distribution K 90 defined in the present invention.

[0066] According to the present invention, based on the total weight of the cobalt additive, the content of Co element is 55-75 wt%.

[0067] According to the present invention, the isothermal time t1 of the first sintering is 15 h or less, preferably 6-12 h.

[0068] In the present invention, the isothermal temperature T2 of the second sintering is not particularly limited, and it is only necessary to ensure 1000 °C ≥ T1 > T2 ≥ 300 °C. Specifically, the isothermal temperature T2 is 300-800 °C, preferably 300-700 °C.

[0069] In the present invention, the isothermal time t2 of the second sintering is not particularly limited, and it is only necessary to ensure 15 h ≥ t1 > t2 ≥ 5 h. Specifically, the isothermal time t2 is 6-12 h, preferably 6-10 h.

[0070] According to the present invention, the usage amounts of the total molar amount [n(Ni) + n(Mn) + n(Co)] of metal elements in the precursor of the positive electrode material, the molar amount n(Li) of Li element in the lithium source, and the molar amount n(G) of G element in the G element-containing additive satisfy 0.95 ≤ n(Li) / [n(Ni) + n(Mn) + n(Co)] ≤ 1.1, 0 ≤ n(G) / [n(Ni) + n(Mn) + n(Co)] ≤ 0.05.

[0071] Furthermore, the usage amounts of the total molar amount [n(Ni) + n(Mn) + n(Co)] of metal elements in the precursor of the positive electrode material, the molar amount n(Li) of Li element in the lithium source, and the molar amount n(G) of G element in the G element-containing additive satisfy 1 ≤ n(Li) / [n(Ni) + n(Mn) + n(Co)] ≤ 1.1, 0.0005 ≤ n(G) / [n(Ni) + n(Mn) + n(Co)] ≤ 0.03.

[0072] In the present invention, the precursor of the positive electrode material is selected from nickel cobalt manganese oxide and / or nickel cobalt manganese hydroxide.

[0073] In the present invention, the type of lithium source is not particularly limited, and it may be a conventional lithium source in this field, such as lithium carbonate and / or lithium hydroxide.

[0074] In the present invention, the type of G element-containing additive is not particularly limited, and it may be a compound capable of providing a conventional G element in this field, such as a G-containing oxide, a G-containing hydroxide, or a G-containing carbonate.

[0075] In the present invention, G is selected from at least one of W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, Mg, and Y.

[0076] According to the present invention, the usage amounts of the total molar amount of metal elements [n(Ni) + n(Co) + n(Mn) + n(G)] in the positive electrode material processed product II, the molar amount n'(Co) of cobalt element in the cobalt additive, and the molar amount n(M) of M element in the M element-containing additive satisfy 0.001 ≤ n'(Co) / [n(Ni) + n(Co) + n(Mn) + n(G)] ≤ 0.05, 0 ≤ n(M) / [n(Ni) + n(Co) + n(Mn) + n(G)] ≤ 0.05.

[0077] Furthermore, the usage amounts of the total molar amount of metal elements [n(Ni) + n(Co) + n(Mn) + n(G)] in the positive electrode material processed product II, the molar amount n'(Co) of cobalt element in the cobalt additive, and the molar amount n(M) of M element in the M element-containing additive satisfy 0.001 ≤ n'(Co) / [n(Ni) + n(Co) + n(Mn) + n(G)] ≤ 0.03, 0 ≤ n(M) / [n(Ni) + n(Co) + n(Mn) + n(G)] ≤ 0.03.

[0078] In the present invention, the type of M element-containing additive is not particularly limited, and it may be a compound capable of providing a conventional M element in this field, such as an M-containing oxide, an M-containing hydroxide, or an M-containing carbonate.

[0079] In the present invention, M is selected from at least one of B, Al, Nb, Mn, Mo, W, Si, Mg, Ti, and Zr.

[0080] The third aspect of the present invention provides a positive electrode material manufactured by the above method.

[0081] The fourth aspect of the present invention provides a lithium-ion battery including the above positive electrode material.

[0082] Hereinafter, the present invention will be described in detail by way of examples. In the following examples, (1) Morphology test: Obtained from a test using a scanning electron microscope of model S-4800 manufactured by Hitachi, Japan. The average particle diameter D of the positive electrode material is obtained by calculating for 300 particles in the electron micrograph. (2) Particle sizes D50, D10, D90: Obtained from a test using a laser particle size analyzer of model Hydro 3000mu manufactured by Marvern. (3) XRD test: Directly tested using a Rigaku turning target diffractometer Smartlab 9KW, or / and obtained by finishing. The crystal grain diameter R, micro residual stress of the positive electrode material, and the peak intensity ratio of the characteristic peak at 38.5° and the characteristic value peak at 37.4° in the cobalt additive are obtained, and the lithium nickel mixed arrangement value is obtained by finishing calculation. (4) The residual alkali content of the positive electrode material is obtained by testing using a Metrohm Orbis potentiometric titrator of Switzerland. (5) The mass of Co element in the total compound: Measured by inductively coupled plasma (ICP) atomic emission spectrometry. (6) Electrochemical performance test: In the above examples and comparative examples, the electrochemical performance of the positive electrode material is tested using a CR2025 button-type battery.

[0083] The manufacturing process of the CR2025 button-type battery is specifically as follows.

[0084] Sheet manufacturing: An appropriate amount of N-methylpyrrolidone (NMP) was thoroughly mixed with the cathode material, conductive carbon black, and polyvinylidene fluoride (PVDF) 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 h, and then pressed and formed under a pressure of 100 MPa to produce a cathode sheet with a diameter of 12 mm and a thickness of 3.2 mm. The loading amount of the cathode material was 15.5 mg / cm 2 is.

[0085] Battery assembly: Inside a gas glove box filled with argon gas with both the water content and oxygen content less than 5 ppm, the cathode sheet, separator, anode sheet, and electrolyte were assembled into a CR2025 button-type battery and then left standing for 6 h. The anode sheet used was a lithium metal sheet with a diameter of 15.8 mm and a thickness of 1 mm. The separator used was a microporous film made of polypropylene with a thickness of 25 μm (Celgard 2325). The electrolyte used was an equal mixture of 1 mol / L LiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC).

[0086] Electrochemical performance test: In the following examples and comparative examples, the electrochemical performance test was carried out on the CR2025 button-type battery using a Shenzhen Neware battery test system. The charge-discharge voltage range was controlled to 2.8 - 4.5 V. Under a constant temperature of 60 °C, the button-type battery was charged and discharged at 0.1C for 2 cycles, and then charged and discharged at 1C for 80 cycles to evaluate the high-temperature cycle capacity retention rate of the cathode material.

[0087] Thermal stability test: The thermal stability of the material was tested with a Mettler DSC3+, and the steps are as follows. The above battery was charged and discharged twice at 0.2C CC-CV with a voltage range of 3 - 4.4 V, charged to 4.4 V at 0.2C CC-CV. After the completion of charging, the battery was disassembled, the cathode material was scraped out from the electrode sheet, 1 g of the cathode material scraped off from the electrode sheet was weighed and subjected to a DSC test to evaluate the thermal stability performance of the cathode material.

[0088] All raw materials used in the examples and comparative examples are commercially available products.

[0089] Example 1 S1. Cobalt oxyhydroxide and cobalt hydroxide are mixed, and the grinding intensity of the jet mill is adjusted to obtain a cobalt additive with D 50 being 0.96 μm. The peak intensity ratio of 38.5° and 37.4° in the XRD of the cobalt additive is 1:2. The specific parameters of the cobalt additive are shown in Table 1, S2. Ni 0.6 Co 0.2 Mn 0.2 (OH)2, lithium carbonate and ZrO2 are coated and mixed at a molar ratio of [n(Ni) + n(Co) + n(Mn)]:n(Li):n(Zr) = 1:1.03:0.0002 to obtain Mixture I, S3. In the atmosphere of air in a muffle furnace, Mixture I is sintered for the first time. The constant temperature T1 is 950 °C and the constant temperature time t1 is 8 h. After grinding with a jet mill and sieving, a positive electrode material process product II is obtained, S4. The positive electrode material process product II, the cobalt additive produced in step (1) and Al2O3 are coated and mixed at a molar ratio of [n(Ni) + n(Co) + n(Mn) + n(Zr)]:n(Co):n(Al) = 1:0.02:0.0001 to obtain a uniform Mixture III, S5. In the atmosphere of air or oxygen, Mixture III is sintered for the second time. The constant temperature T2 is 700 °C and the constant temperature time t2 is 10 h. After directly sieving, a positive electrode material A1 is obtained. Some process conditions and the composition of the positive electrode material A1 are shown in Table 2.

[0090] The physicochemical parameters of the positive electrode material A1 are tested, and the results are shown in Table 3.

[0091] The positive electrode material A1 is assembled into a CR2025 button-type battery, and the electrochemical performance and thermal stability of the battery are tested. The results are shown in Table 4.

[0092] Example 2 In step S1, a positive electrode material A2 was produced in the same manner as in Example 1, except that the ratio of cobalt oxyhydroxide to cobalt hydroxide was adjusted so that the peak intensity ratio of 38.5° to 37.4° in the XRD of the cobalt additive was 1:4.

[0093] Example 3 In step S2, a positive electrode material A3 was produced in the same manner as in Example 1, except that Ni 0.6 Co 0.2 Mn 0.2 (OH)2 was replaced with Ni 0.8 Co 0.1 Mn 0.1 (OH)2.

[0094] Example 4 In step S1, a positive electrode material A4 was produced in the same manner as in Example 1, except that the ratio of cobalt oxyhydroxide to cobalt hydroxide was adjusted so that the peak intensity ratio of 38.5° to 37.4° in the XRD of the cobalt additive was 1:7.

[0095] Example 5 In step S4, a positive electrode material A5 was produced in the same manner as in Example 1, except that no Al2O3 was added and only the cobalt additive was added, and [n(Ni)+n(Co)+n(Mn)+n(Zr)]:n(Co)=1:0.02.

[0096] Example 6 In step S2, a positive electrode material A6 was produced in the same manner as in Example 1, except that Ni 0.6 Co 0.2 Mn 0.2 (OH)2, lithium carbonate, Al2O3, and SrCO3 were used in a molar ratio of [n(Ni)+n(Co)+n(Mn)]:n(Li):n(Al):n(Sr)=1:1.03:0.00015:0.00005.

[0097] Example 7 In step S1, the positive electrode material A7 was produced in the same manner as in Example 1, except that the ratio of cobalt oxyhydroxide to cobalt hydroxide was adjusted so that the peak intensity ratio at 38.5° and 37.4° in the XRD of the cobalt additive was 1:1.4.

[0098] Example 8 In step S4, the positive electrode material A8 was produced in the same manner as in Example 1, except that the positive electrode material process product II, the cobalt additive produced in step S1, and Al2O3 were coated and mixed at a molar ratio of [n(Ni)+n(Co)+n(Mn)+n(Zr)]:n(Co):n(Al)=1:0.01:0.0001.

[0099] Example 9 In step S4, the positive electrode material A9 was produced in the same manner as in Example 1, except that the positive electrode material process product II, the cobalt additive produced in step S1, and Al2O3 were coated and mixed at a molar ratio of [n(Ni)+n(Co)+n(Mn)+n(Zr)]:n(Co):n(Al)=1:0.04:0.0001.

[0100] Example 10 In step S3, the positive electrode material A10 was produced in the same manner as in Example 1, except that the mixture I was sintered for the first time, and the constant temperature T1 was changed to 930°C and the constant temperature time t1 was changed to 9.5 h.

[0101] Example 11 In step S3, the positive electrode material A11 was produced in the same manner as in Example 1, except that the mixture I was sintered for the first time, and the constant temperature T1 was changed to 980°C and the constant temperature time t1 was changed to 7 h.

[0102] Example 12 In step S1, the positive electrode material D3 was produced in the same manner as in Example 1, except that the pulverization intensity of the air jet mill was adjusted so that D of the cobalt additive 50 was 7.90 μm.

[0103] Example 13 In step S1, the pulverization intensity of the air jet mill was adjusted so that D of the cobalt additive50 to 1.2 μm, K 90 A positive electrode material A13 was produced in the same manner as in Example 1, except that was made 2.2.

[0104] Comparative Example 1 In Step S1, a positive electrode material D1 was produced in the same manner as in Example 1, except that the ratio of cobalt oxyhydroxide to cobalt hydroxide was adjusted so that the peak intensity ratio of 38.5° to 37.4° in the XRD of the cobalt additive was 1:8.

[0105] Comparative Example 2 In Step S1, a positive electrode material D2 was produced in the same manner as in Example 1, except that the ratio of cobalt oxyhydroxide to cobalt hydroxide was adjusted so that the peak intensity ratio of 38.5° to 37.4° in the XRD of the cobalt additive was 1:0.2.

[0106] Comparative Example 3 In Step S1, a positive electrode material D3 was produced in the same manner as in Example 1, except that only cobalt oxyhydroxide was used.

[0107] Comparative Example 4 In Step S1, a positive electrode material D4 was produced in the same manner as in Example 1, except that only cobalt hydroxide was used.

[0108] Comparative Example 5 In Step S3, a positive electrode material D5 was produced in the same manner as in Example 1, except that the constant temperature T1 of the first sintering was set to 1020°C.

[0109] [Table 1]

[0110] [Table 2-1]

[0111] [Table 2-2]

[0112]

Table 2-3

[0113]

Table 2-4

[0114]

Table 2-5

[0115]

Table 2-6

[0116]

Table 3

[0117]

Table 4

[0118] Figure 1 is the XRD spectrum diagram of the cobalt additives in Example 2 and Comparative Example 1. As can be seen from Table 1 and Table 4, since the peak intensity ratios of the XRD in the cobalt additive at 38.5° and 37.4° are different, when the produced cathode material is used in a lithium-ion battery, the electrical performance of the lithium-ion battery is also very different. When the peak intensity ratios of the XRD in the cobalt additive at 38.5° and 37.4° are within the range defined by the present invention, when the produced cathode material is used in a lithium-ion battery, the battery exhibits high capacity and excellent cycle retention rate.

[0119] As can be seen from Examples 1, 2, 7 and Comparative Examples 1 and 2, when the peak intensity ratio of the cobalt additive XRD in Examples 1 and 2 is within the range defined in the present invention, compared with Examples 1 and 2, the peak intensity ratio of cobalt addition in Example 7 is not within the preferred range of the present invention, and both the capacity and cycle retention rate of the lithium-ion battery manufactured with the cathode material decrease, but are much higher than those in Comparative Examples 1 and 2. The peak intensity of the cobalt additive XRD in Comparative Examples 1 and 2 is not within the range defined in the present invention. The capacity of the lithium-ion battery containing the cathode material manufactured in Comparative Examples 1 and 2 decreases, and both the rate and cycle retention rate at high temperature decrease.

[0120] As can be seen from Examples 1, 5, 6, 8 - 11, whether the cathode material contains the coating element M, the change in the type of doping element G, the change in the usage amount of the cobalt additive, and the change in the first sintering conditions do not affect the XRD structural characteristics of the cathode material. As long as the cathode material contains a coating layer formed by the cobalt additive defined in the present invention, a cathode material having the specific XRD structural characteristics described in the present invention can be manufactured. When the cathode material is used in a lithium-ion battery, the electrical performance of the battery is significantly improved compared with the prior art.

[0121] Figure 2 is the SEM of the cathode material of Example 1, and Figure 3 is the SEM diagram of the cathode material of Example 12. As can be seen from Figures 2 and 3, compared with Example 1, the coating state on the surface of the cathode material in Example 12 is significantly deteriorated. A large number of cobalt agglomerated particles (especially small particles concentrated in the middle part) appear in the SEM photograph, and there are exposed parts on the surface of some cathode materials even after coating, indicating that the additive in Comparative Example 3 is difficult to be uniformly mixed. This is because the D 50 of the cobalt additive in Example 12 is large and there is a lot of particle adhesion. As can be seen from Examples 1, 12 and 13, the K 90 of the cobalt additive is large, the particle size distribution is wide, and it is more difficult to achieve uniform mixing under the same conditions. Therefore, such a large D 50 and / or K 90When manufacturing a product using a cobalt additive that is too large, the electrical performance of the finished positive electrode material will be significantly reduced due to non-uniform mixing.

[0122] The cobalt additives in Comparative Examples 3 and 4 are single cobalt oxyhydroxide or cobalt hydroxide, and their D 50 is within the range limited by the present invention, and the performance of the finished products of the positive electrode materials manufactured thereby is all worse than the material performance of Example 1. Figure 4 is a DSC spectrum diagram of the cobalt positive electrode materials of Example 1, Comparative Example 3, and Comparative Example 4. As can be seen from the DSC data in Figure 4, the thermal stability of the positive electrode material manufactured in Example 1 is optimal. The valence of cobalt in cobalt oxyhydroxide is +3, which is the same as the average valence of nickel cobalt manganese in the positive electrode material. Therefore, it can enter the interior of the material to supplement lattice defects, does not cause valence changes of nickel and manganese elements, and can play a role in stabilizing the material. For this reason, the DSC peak values of Example 1 and Comparative Example 3 are higher than the peak value of Comparative Example 4. The higher the temperature corresponding to the peak value, the higher the temperature required for combustion and thus explosion to occur, that is, the higher the peak value, the better the stability. Compared with single cobalt oxyhydroxide, the cobalt additive manufactured by this method further increases the DSC peak value, improves the thermal stability, and is further beneficial to the improvement of the stability of the battery manufactured with this positive electrode material.

[0123] If the sintering temperature in Comparative Example 5 is too high, the value of D / R will increase, so the crystal structure of the positive electrode material will increase, the lithium ion transport ability inside the material will weaken, and at the same time, the lithium nickel mixed arrangement inside the material will also deteriorate, and finally the capacity and cycle performance of the material will deteriorate.

[0124] As can be seen from the XRD finishing data in Table 3, Ni in the positive electrode material according to the present invention 2+There is less of it, the degree of its mixed array is low, indicating that the lithium nickel layer is relatively stable. At the same time, the micro residual stress values in the examples are all lower than those in the comparative examples. The greater the stress value, the greater the degree of defects existing inside the material, indicating that the risk of pulverization of the material during the cycle process increases. Since the cathode material according to the present invention has low micro stress, mixed array nickel content and specific XRD structural characteristics, the cathode material can have excellent stability.

[0125] 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 scope of the present invention, multiple simple modifications are possible to the technical solution means of the present invention, including combining each technical feature in any other appropriate manner. These simple modifications and combinations are similarly regarded as the content disclosed in the present invention and all belong to the protection scope of the present invention. Cross-reference of related applications

[0126] This application claims the benefit of Chinese Patent Application No. 202310575361.8, filed on May 19, 2023, the content of which is incorporated herein by reference.

Claims

1. A positive electrode material, wherein the micro residual stress of the positive electrode material measured by XRD is 0.01 - 0.15, the average diameter of the positive electrode material measured by SEM electron microscope is D, and the crystal grain diameter measured by XRD is R, where D / R is 1.4 - 2.5, a positive electrode material characterized by this.

2. The micro residual stress of the positive electrode material measured by XRD is 0.03 - 0.15, Preferably, D / R is 1.4 - 2, the positive electrode material according to Claim 1.

3. The average diameter D of the positive electrode material is 1 - 3 μm, preferably 1.5 - 2 μm, Preferably, the crystal grain diameter R of the positive electrode material is 700 - 1200 nm, preferably 900 - 1000 nm, Preferably, the median diameter D50 of the positive electrode material is 3 - 4.5 μm, Preferably, the mixed array nickel content of the positive electrode material is 0 - 4 wt%, preferably 0 - 3 wt%, the positive electrode material according to Claim 1 or 2.

4. The positive electrode material includes a matrix and a coating layer coated on the matrix, the matrix has a composition shown in Formula I, Li １＋ａ Ni ｘ Mn ｙ Co ｚ G ｂ O ２ Formula I where -0.05 ≤ a ≤ 0.1, 0 ≤ b ≤ 0.05, 0.5 ≤ x < 1, 0 < y < 0.5, 0 ≤ z < 0.5, and G is selected from at least one of W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, Mg, and Y, the coating layer includes a lithium oxygen compound containing cobalt element and / or an oxide containing cobalt element, Optionally, the coating layer further includes a lithium oxygen compound containing M element and / or an oxide containing M element, and M is selected from at least one of B, Al, Nb, Mn, Mo, W, Si, Mg, Ti, and Zr, Preferably, between the molar amount n'(Co) of cobalt element in the coating layer, the molar amount n(M) of M element in the coating layer, and the total molar amount [n(Ni) + n(Co) + n(Mn) + n(G)] of metal elements other than Li in the matrix, 0.001 ≤ n'(Co):[n(Ni) + n(Co) + n(Mn) + n(G)] ≤ 0.05, 0 ≤ n(M):[n(Ni) + n(Co) + n(Mn) + n(G)] ≤ 0.05 is satisfied, the positive electrode material according to any one of Claims 1 - 3.

5. The residual alkali content of the positive electrode material is 1000 - 10000 ppm, preferably 1000 - 6000 ppm, Preferably, when 0.5 ≦ x < 0.8, the residual alkali content of the positive electrode material is 1000 - 3000 ppm, or when 0.8 ≦ x < 1, the residual alkali content of the positive electrode material is 4000 - 6000 ppm. The positive electrode material according to any one of claims 1 - 4.

6. A method for manufacturing a positive electrode material, wherein the method for manufacturing the positive electrode material comprises: (1) mixing a positive electrode material precursor, a lithium source, and an optional G - element - containing additive to obtain a mixture I; (2) sintering the mixture I for the first time in an atmosphere of air or oxygen to obtain a positive electrode material intermediate product II; (3) mixing the positive electrode material intermediate product II, the cobalt additive, and an optional M - element - containing additive to obtain a mixture III; (4) sintering the mixture III for the second time in an atmosphere of air or oxygen to obtain the positive electrode material. The method includes that the peak intensity ratio between the characteristic peak at 38.5° and the characteristic peak at 37.4° of the cobalt additive measured by XRD is 1:1.1 - 7.5; The constant temperature T of the first sintering １ is 1000 °C or lower, and a method for producing a positive electrode material, characterized by this.

7. The peak intensity ratio between the characteristic peak at 38.5° and the characteristic peak at 37.4° of the cobalt additive measured by XRD is 1:2 - 4.5; Preferably, the median diameter D of the cobalt additive （Ｃｏ）５０ is 0.5 - 5 μm, preferably 0.5 - 3 μm, and the particle size distribution K of the cobalt additive （Ｃｏ）９０ = (D ９０ - D １０ ) / D （Ｃｏ）５０ satisfies 0.8 ≤ K （Ｃｏ）９０ ≤ 2, preferably, 1 ≤ K （Ｃｏ）９０ ≤ 1.8 is satisfied, Preferably, the constant temperature T of the first sintering １ is 700 - 1000°C, and the method according to claim 6.

8. Based on the total weight of the cobalt additive, the content of Co element is 55 - 75 wt%; Preferably, the holding time t of the first sintering １ is 15 h or less, preferably 6 - 12 h, Preferably, the constant temperature of the second sintering is T ２ where T １ > T ２ and Preferably, the holding time of the second sintering is t １ where t １ > t ２ The method according to claim 6 or 7, wherein.

9. The usage amounts of the total molar amount of metal elements [n(Ni)+n(Mn)+n(Co)] in the positive electrode material precursor, the molar amount n(Li) of Li element in the lithium source, and the molar amount n(G) of G element in the G - element - containing additive satisfy 0.95 ≦ n(Li) / [n(Ni)+n(Mn)+n(Co)] ≦ 1.1, 0 ≦ n(G) / [n(Ni)+n(Mn)+n(Co)] ≦ 0.

05. Preferably, the usage amounts of the total molar amount of metal elements [n(Ni)+n(Co)+n(Mn)+n(G)] in the positive electrode material intermediate product II, the molar amount n'(Co) of cobalt element in the cobalt additive, and the molar amount n(M) of M element in the M - element - containing additive satisfy 0.001 ≦ n'(Co) / [n(Ni)+n(Co)+n(Mn)+n(G)] ≦ 0.05, 0 ≦ n(M) / [n(Ni)+n(Co)+n(Mn)+n(G)] ≦ 0.

05. The method according to any one of claims 6 - 8.

10. A positive electrode material manufactured by the method according to any one of claims 6 - 9.

11. A lithium-ion battery comprising the positive electrode material according to any one of claims 1 to 5 and 10.

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