High-nickel cathode material, its manufacturing method and applications

Abstract

This application provides a high-nickel cathode material, a method for manufacturing the same, and its applications. The high-nickel cathode material according to this application is a secondary particle formed by the aggregation of primary crystal grains, with grain boundaries between adjacent primary crystal grains, where the mass ratio of cobalt and nickel elements in the grain boundaries on the surface of the secondary particle is A, the mass ratio of cobalt and nickel elements in the grain boundaries inside the secondary particle is B, and the mass ratio of cobalt and nickel elements in the primary crystal grains on the surface of the secondary particle is C, where A is greater than B and A is greater than C. The high-nickel cathode material according to this application has a cobalt-rich structure at the grain boundaries on the surface of the secondary particle, improving the structural stability of the material and suppressing the occurrence of side reactions with the electrolyte. As a result, the battery exhibits superior discharge capacity, Coulomb efficiency, and capacity retention rate.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and particularly to high-nickel cathode materials, their manufacturing methods, and applications.

Background Art

[0002] Under the promotion of China's new energy policy, China's new energy-related industries have developed rapidly and vigorously. Lithium-ion batteries are widely used because they have advantages such as high operating voltage, high energy density, and long cycle life.

[0003] The cathode material is an important component of a lithium-ion battery and is also an important factor determining the performance and cost of a lithium-ion battery. The ternary cathode material, which is a lithium metal oxide containing at least two elements of nickel and cobalt, has good ternary synergistic effects and shows advantages such as high specific capacity, good cycle performance, low cost, and low toxicity. It is a kind of cathode material with great application value. In the ternary cathode material, nickel is the main redox reaction element, and by increasing the nickel content, the specific capacity of the ternary cathode material can be effectively improved. The cobalt element can stabilize the layered structure of the material, reduce the phenomenon of cation disordered arrangement, and promote the conduction of lithium ions and electrons. With the shortage of cobalt resources, the ternary cathode material tends to be composed of high nickel and low cobalt more and more significantly. However, as the nickel content increases and the cobalt content decreases, the stability of the cathode material deteriorates, the side reaction with the electrolyte becomes more severe, and the capacity, cycle performance, and Coulomb efficiency of the lithium-ion battery deteriorate.

Summary of the Invention

Problems to be Solved by the Invention

[0004] This application provides a high-nickel cathode material having a cobalt-rich structure at the grain boundaries on the surface layer of secondary particles, which can improve the structural stability of the material and suppress the occurrence of side reactions with the electrolyte. As a result, the battery becomes excellent in discharge capacity, Coulomb efficiency, and capacity retention rate.

[0005] This invention further provides a method for manufacturing a high-nickel cathode material, the method comprising pre-sintering a mixture of a precursor of the high-nickel cathode material, a lithium source, and a cobalt source to form lithium cobalt oxide on the surface of the precursor particles, injecting the lithium cobalt oxide into the grain boundaries under the action of a lithium source as a dissolution aid, and controlling the subsequent sintering conditions to avoid the diffusion of cobalt elements into the core and interior of the grains of the secondary particles, thereby producing a high-nickel cathode material with cobalt-rich grain boundaries on the surface of the secondary particles.

[0006] The present invention further provides a positive electrode plate, which comprises the above-mentioned high-nickel positive electrode material, and thus the positive electrode plate has good stability and is less prone to side reactions with the electrolyte.

[0007] This invention further provides a lithium-ion battery, which, having the above-mentioned positive electrode plate, exhibits superior discharge capacity, Coulomb efficiency, and capacity retention rate. [Means for solving the problem]

[0008] In a first aspect, the present application provides a high-nickel cathode material, wherein the high-nickel cathode material is composed of secondary particles formed by the aggregation of primary crystal grains, and grain boundaries are included between adjacent primary crystal grains. The mass ratio of cobalt and nickel elements at the grain boundaries on the surface of the secondary particle is A, the mass ratio of cobalt and nickel elements at the grain boundaries in the core of the secondary particle is B, and the mass ratio of cobalt and nickel elements in the primary grains on the surface of the secondary particle is C, where A is greater than B and A is greater than C.

[0009] According to the above-described high-nickel cathode material, the surface layer of the secondary particles contains a first dopant element, and the first dopant element is selected from at least one metallic element whose valence can reach +5 or higher.

[0010] According to the above high-nickel cathode material, the first dopant element is selected from at least one of Ta, Nb, Mo, and W.

[0011] According to the above high-nickel cathode material, the concentration of the first dopant element at the grain boundaries of the surface layer of the secondary particles is higher than the concentration of the first dopant element in the primary grains in the surface layer.

[0012] According to the above high-nickel cathode material, the secondary particles contain a second dopant element, and the second dopant element is selected from at least one of Zr, Al, Ti, Mg, Sc, Y, La, Sr, and B.

[0013] According to the above high-nickel cathode material, the surface of the secondary particles is coated with a coating layer, and the coating layer contains at least one element of B, Al, Ce, Zr, Ti, and Si.

[0014] According to the above high-nickel cathode material, the chemical composition of the high-nickel cathode material is Li n Ni x Co y K z M a N b O2, where 0.95 < n < 1.1, 0.85 ≤ Ni < 1, 0 < y ≤ 0.15, 0 ≤ z ≤ 0.15, 0 < a ≤ 0.15, 0 < b ≤ 0.05, K is selected from Mn or Al, M is selected from at least one of Al, Zr, Y, Ti, Sr, Ce, La, Mg, B, Si, and Sc, and N is selected from at least one of Ta, Nb, Mo, W, Sb, Bi, and V.

[0015] In a second aspect, the present application provides a method for manufacturing the above high-nickel cathode material, and the manufacturing method includes the following steps 1) to 3): In step 1), a mixed system containing a precursor of a high-nickel cathode material, a lithium source, and a cobalt source is pre-sintered in an oxygen-containing atmosphere to obtain a pre-sintered body. The temperature of the pre-sintering is 400 to 600 °C, and the time is 4 to 10 h. In step 2), the mixed system containing the pre-sintered body and the compound of the first dopant element is subjected to primary sintering in an oxygen-containing atmosphere to obtain the primary sintered body. The first dopant element is selected from at least one metallic element whose valence can reach +5 or higher. The temperature of the primary sintering was 650-800°C, and the time was 8-16 hours. In step 3), the first sintered product is subjected to secondary sintering in an oxygen-containing atmosphere to obtain the high-nickel cathode material.

[0016] According to the above manufacturing method, in step 2), the mixed system further includes a compound of a second dopant element, the second dopant element being selected from at least one of Zr, Al, Ti, Mg, Sc, Y, La, Sr, and B.

[0017] According to the above manufacturing method, in step 3), the secondary sintering includes sintering the mixed system of the first sintered product and the coating agent at 200 to 500°C for 8 to 16 hours. The coating agent is selected from compounds containing a coating element, and the coating element is selected from at least one of B, Al, Ce, Zr, Ti, and Si.

[0018] In a third aspect, the present invention provides a positive electrode plate comprising the above-mentioned high-nickel positive electrode material.

[0019] In a fourth aspect, the present invention provides a lithium-ion battery comprising the above-described positive electrode plate. [Effects of the Invention]

[0020] The implementation of this application offers at least the following advantages: 1) to 3).

[0021] 1) In the high-nickel cathode material according to the present invention, the secondary particles are formed by the aggregation of multiple primary crystal grains, and the cobalt-rich grain boundaries on the surface of the secondary particles are, specifically, A, which is greater than the mass ratio C of cobalt and nickel in the primary crystal grains on the surface of the secondary particles and the mass ratio B of cobalt and nickel in the grain boundaries in the core of the secondary particles. As a result, the structural stability of the material is significantly improved, the occurrence of side reactions with the electrolyte is suppressed, and the Coulomb efficiency and cycle life can be improved. At the same time, the layered structure is maintained during charging and discharging, ensuring the conduction route for lithium ions and improving magnification performance. Furthermore, the cobalt enrichment at the grain boundaries on the surface of the secondary particles effectively reduces the overall cobalt content of the secondary particles. As a result, a decrease in the capacity of the cathode material caused by an excessively high concentration of cobalt in the overall secondary particles is avoided, and the energy density of the cathode material is improved.

[0022] 2) The method for manufacturing a high-nickel cathode material provided in this application involves pre-sintering a precursor of the high-nickel cathode material and a mixed system of a lithium source and a cobalt source, ensuring that the cobalt source and lithium source are in sufficient contact and react to form lithium cobalt oxide on the surface of the precursor particles, and that the lithium cobalt oxide is injected into the grain boundaries under the action of the lithium source as a dissolution aid. During primary sintering, a high-valence metal element is added by doping the grain boundaries in the surface layer, and the stronger metal-oxygen bonding of the high-valence metal suppresses the diffusion of Co element from the grain boundaries to the primary crystal grains and the diffusion between primary crystal grains. This maintains a cobalt-rich structure at high temperatures, where the cobalt concentration at the surface grain boundaries is higher than the cobalt concentration in the primary crystal grains in the surface layer. Furthermore, the high-valence element doped into the surface of the secondary particles suppresses oxygen deposition, improves the accumulation performance of the cathode material, and reduces gas generation.

[0023] 3) The high-nickel cathode material according to the present invention has good structural stability and can suppress the occurrence of side reactions with the electrolyte. Therefore, when this high-nickel cathode material is applied to a cathode plate and then to a lithium-ion battery, the lithium-ion battery will have superior discharge capacity, Coulomb efficiency, and capacity retention rate. [Brief explanation of the drawing]

[0024] To more clearly describe the embodiments of the present application or the solutions of the prior art, the drawings that may be used in the description of the embodiments or the prior art are briefly described below. Naturally, the drawings described below are some embodiments of the present application, and those skilled in the art will be able to conceive of other drawings based on these without requiring any creative effort. [Figure 1] This is an SEM diagram of the high-nickel cathode material according to Example 1 of the present application. [Modes for carrying out the invention]

[0025] To clarify the purpose, technical solution, and advantages of this application, the technical solution will be described clearly and completely below with reference to the embodiments of this application. Naturally, the embodiments described are only a part of the embodiments of this application, not all of them. A person skilled in the art will find that all other embodiments obtained without creative work based on the embodiments of this application fall within the scope of protection of this application.

[0026] In a first aspect, the present application provides a high-nickel cathode material, which is a secondary particle formed by the aggregation of primary crystal grains, and includes grain boundaries between adjacent primary crystal grains. The mass ratio of cobalt to nickel elements at the grain boundaries on the surface of the secondary particle is A, the mass ratio of cobalt to nickel elements at the grain boundaries in the core of the secondary particle is B, and the mass ratio of cobalt to nickel elements in the primary grains on the surface of the secondary particle is C, where A is greater than B and A is greater than C.

[0027] When A, B, and C satisfy the above relationship, the high-nickel cathode material has a surface cobalt-rich structure, and in particular, the grain boundaries on the surface of the secondary particles are cobalt-rich, which significantly improves the structural stability of the material, suppresses the occurrence of side reactions with the electrolyte, and can improve Coulomb efficiency and cycle life. At the same time, it maintains a layered structure during charging and discharging, securing the conduction route for lithium ions and improving magnification performance. Furthermore, the cobalt enrichment at the grain boundaries on the surface of the secondary particles effectively reduces the overall cobalt content of the secondary particles, thereby avoiding a decrease in the capacity of the cathode material caused by an excessively high concentration of cobalt in the secondary particles and improving the energy density of the cathode material.

[0028] In one selective embodiment, the surface of the secondary particles further contains a first dopant element, the first dopant element being selected from at least one metallic element whose valence can reach +5 or higher. For example, the dopant element N may be selected from metallic elements such as Ta, Nb, Mo, W, Bi, Sb, and V. By doping the surface of the secondary particles with a high-valence metallic element, the diffusion of cobalt into the material at the secondary particle surface is avoided, the diffusion of cobalt into the primary crystal grains at the grain boundaries is avoided, the cobalt-rich structure of the grain boundaries at the surface of the secondary particles is maintained, and the stability of the high-nickel cathode material can be further improved.

[0029] Furthermore, the first dopant element is selected from at least one of Ta, Nb, Mo, and W, and doping with the above elements can further improve the structural stability of the high-nickel cathode material.

[0030] Furthermore, the concentration of the first dopant element at the grain boundaries on the surface of secondary particles is greater than the concentration of the first dopant element in the primary grains on the surface. Enrichment of the first dopant element at the surface grain boundaries can effectively prevent the diffusion of cobalt element during sintering.

[0031] In this application, the mass contents of cobalt and nickel elements at the grain boundaries in the surface layer of the secondary particles, the mass contents of cobalt and nickel elements at the grain boundaries in the core of the secondary particles, the mass contents of cobalt and nickel elements in the primary grains in the surface layer of the secondary particles, the mass content of the first dopant element at the grain boundaries in the surface layer of the secondary particles, and the mass content of the first dopant element in the primary grains in the surface layer of the secondary particles can all be measured by collecting samples of the corresponding regions using an EDS (energy dispersive X-ray analyzer).

[0032] In one alternative embodiment, the secondary particles further contain a second dopant element, the second dopant element is selected from at least one of Zr, Al, Ti, Mg, Sc, Y, La, Sr, B, and by doping the second dopant element, the specific capacity, stability, and rate performance of the cathode material can be further improved.

[0033] The high-nickel cathode material according to this application may directly consist of secondary particles, or the high-nickel cathode material may also be obtained by further coating the surface of the secondary particles with a coating layer. Here, the coating layer contains at least one element of B, Al, Ce, Zr, Ti, Si. By coating the surface of the secondary particles using the above elements, the contact between the cathode material and the electrolyte can be further avoided, and the occurrence of side reactions between the cathode active material and the electrolyte can be suppressed.

[0034] In one alternative embodiment, the chemical composition of the high-nickel cathode material is Li n Ni x Co y K z M a N b O2, where 0.95 < n < 1.1, 0.85 ≤ Ni < 1, 0 < y ≤ 0.15, 0 ≤ z ≤ 0.15, 0 < a ≤ 0.15, 0 < b ≤ 0.05, K is selected from Mn or Al, M is selected from at least one of Al, Zr, Y, Ti, Sr, Ce, La, Mg, B, Si, Sc, and N is selected from at least one of Ta, Nb, Mo, W, Sb, Bi, V.

[0035] In a second aspect, the present application provides a method for manufacturing the above-mentioned high-nickel cathode material, the manufacturing method comprising the following steps 1) to 3): 1) In this method, a mixed system containing a precursor of high-nickel cathode material, a lithium source, and a cobalt source is pre-sintered in an oxygen-containing atmosphere to obtain a pre-sintered body. The pre-sintering temperature is 400-600°C, and the time is 4-10 hours. 2) In this process, a mixed system containing a pre-sintered body and a compound of the first dopant element is subjected to primary sintering in an oxygen-containing atmosphere to obtain a primary sintered body. The first dopant element is selected from at least one metallic element whose valence can reach +5 or higher, the primary sintering temperature is 650-800°C, and the time is 8-16 hours. 3) The first sintered product is subjected to secondary sintering in an oxygen-containing atmosphere to obtain a high-nickel cathode material.

[0036] In step 1), a mixed system containing a precursor of high-nickel cathode material, a lithium source, and a cobalt source is pre-sintered at a low temperature. This allows lithium cobalt oxide to be formed on the surface of the precursor under lithium-rich conditions. Simultaneously, the lithium cobalt oxide is injected into the grain boundaries under the action of the lithium source as a dissolution aid, thereby preventing the diffusion of cobalt into the particle interior at low temperatures and maintaining a cobalt-rich structure on the secondary particle surface.

[0037] In step 2), a mixed system containing a pre-sintered body and a compound of the first dopant element is primary sintered. This allows the high-valence first dopant element to form a protective layer between the grain boundaries. The stronger metal-oxygen bonding of the high-valence metal suppresses the diffusion of cobalt from the grain boundaries into the interior of the primary grains and the core of the secondary particles. Furthermore, pre-sintering relatively shortens the time required for primary sintering. As a result, a cobalt-rich, high-nickel cathode material with grain boundaries on the surface of the secondary particles is obtained.

[0038] The first dopant element includes, but is not limited to, metallic elements whose valence can reach +5 or higher, such as Ta, Nb, Mo, W, Bi, Sb, and V. The compound of the first dopant element refers to a compound containing the first dopant element, and includes, but is not limited to, oxides, hydroxides, chlorides, sulfates, nitrates, acetates, carbonates, etc., of the first dopant element.

[0039] In the above manufacturing method, the precursor of the high-nickel cathode material may be in the form of a hydroxide, oxide, or carbonate. For example, if the high-nickel cathode material is a nickel-cobalt-manganese ternary material, its precursor may be a nickel-cobalt-manganese hydroxide, oxide, or carbonate. This application does not limit the source of the precursor of the high-nickel cathode material; it may be obtained by purchasing a commercially available product or manufactured using conventional methods in the art.

[0040] Furthermore, in step 1), the lithium source is selected from LiOH, and the melting effect of lithium hydroxide contributes to a smooth and uniform coating of lithium cobalt oxide on the surface of the secondary particles, thereby improving the structural stability of the material.

[0041] This application does not particularly limit the type of cobalt source, but it can be selected from cobalt sources commonly used in the art, and includes, but is not limited to, at least one of CoO, Co2O3, Co3O4, Co(OH)2, CoOOH, CoCO3, CoSO4, Co(NO3)2, and cobalt acetate.

[0042] In step 1), the oxygen-containing atmosphere refers to an atmosphere containing oxygen, which may be a pure oxygen atmosphere or an air atmosphere, but a pure oxygen atmosphere is preferred.

[0043] Step 2) includes a cleaning and drying step after the primary sintered body has been obtained. The cleaning removes residual alkali from the surface of the primary sintered body, and the drying removes moisture. The present invention does not particularly limit the cleaning and drying conditions, but conditions that have been conventionally used in this field can be used.

[0044] In step 3), the primary sintered body is subjected to secondary sintering. This removes bound water and internal moisture that have formed by bonding with the material surface, thus preventing swelling during battery use. Secondary sintering is completed by sintering at 200-500°C for 8-16 hours.

[0045] In one selective embodiment, if the high-nickel cathode material further contains a second dopant element, the doping of the second dopant element can be completed by adding a compound of the second dopant element to the mixture in step 2) and performing primary sintering again. The second dopant element can be selected from one or more of Zr, Al, Ti, Mg, Sc, Y, La, Sr, and B, and the compound containing the second dopant element can be selected from oxides, hydroxides, chlorides, sulfates, nitrates, acetates, carbonates, etc. of the second dopant element.

[0046] In one selective embodiment, the secondary particle surface of the high-nickel cathode material is further coated with a coating layer, and in step 3), the coating of the secondary particle surface can be completed by adding more coating agent to the mixture and performing secondary sintering. The coating agent is a compound containing a coating element, the coating element being selected from at least one of B, Al, Ce, Zr, Ti, and Si, and the compound containing the coating element may be selected from oxides, hydroxides, chlorides, sulfates, nitrates, acetates, carbonates, etc. of the coating element.

[0047] In a third aspect, the present invention provides a positive electrode plate comprising the above-mentioned high-nickel positive electrode material. The positive electrode plate comprises a positive electrode current collector and a positive electrode active layer installed on at least one functional surface of the positive electrode current collector, the positive electrode active layer comprising the above-mentioned high-nickel positive electrode material.

[0048] This invention does not particularly limit the positive electrode current collector, but current collectors that have been conventionally used in this field, such as aluminum foil which can be purchased commercially, can be used.

[0049] The positive electrode active layer relating to this application contains the above-mentioned high-nickel positive electrode material, which in the positive electrode active layer is used as the positive electrode active material. In addition to the positive electrode active material, the positive electrode active layer may also contain components such as a conductive agent and an adhesive. Since the conductive agent and adhesive can be those conventionally used in this field, a detailed explanation is omitted here.

[0050] In a fourth aspect, the present invention provides a lithium-ion battery comprising the above-described positive electrode plate. The positive electrode plate comprises the high-nickel positive electrode material provided in the present invention, and the positive electrode material has the advantages of good stability and is less prone to side reactions with the electrolyte, and therefore the battery has excellent discharge capacity, Coulomb efficiency and capacity retention rate.

[0051] The lithium-ion battery according to this application further comprises a separator, a negative electrode plate, and an electrolyte, in addition to a positive electrode plate. The configuration of the negative electrode plate can be found in reference to conventional negative electrode plates in the art, and will not be described here. As the separator, separators that have been conventionally used in the art, such as PP films and PE films, can be used.

[0052] The lithium-ion battery according to this application can be manufactured using conventional methods in the art. For example, a lithium-ion battery can be obtained by sequentially stacking and installing a positive electrode plate, a separator, and a negative electrode plate, then obtaining a battery cell through a stacking or winding process, and subsequently performing processes such as roasting, liquid injection, chemical conversion, and sealing.

[0053] The high-nickel cathode material and manufacturing method provided in this application will be described in more detail below using specific examples.

[0054] The reagents, materials, and equipment used in the following examples are all commonly used reagents, materials, and equipment in this field, and can be obtained by purchasing them commercially. The relevant reagents can also be synthesized using conventional methods in this field.

[0055] Example 1 The high-nickel cathode material in this embodiment has a chemical composition of Li 1.01 Ni 0.915 Co 0.056 Mn 0.029 Mo 0.002 Zr 0.002 Sr 0.001 Y 0.001 B 0.01 Al 0.004 Ti 0.002 It is O2, and its manufacturing method includes the following steps 1) to 4), 1) In this method, the hydroxide precursor of NCM9253, LiOH, and Co2O3 were mixed at a molar ratio of 1:1.05:0.004 at 800 rpm for 30 minutes. Then, the mixture was heated to 550°C at a rate of 2°C / min in an oxygen atmosphere and held for 8 hours to obtain a pre-sintered body. In step 2), the pre-sintered body was mixed with ammonium molybdate, ZrO2, SrO, and Y2O3 in a molar ratio of 1:0.002:0.002:0.001:0.0005 at 800 rpm. The mixture was then heated to 750°C at a rate of 5°C / min in an oxygen atmosphere and held for 12 hours to obtain the primary sintered body. In step 3), the primary sintered body was washed with deionized water and then vacuum-dried at 120°C to obtain a washed and dried body. In step 4), the washed and dried material was mixed with the coating agents H3BO3, Al2O3, and TiO2 in a molar ratio of 1:0.01:0.002:0.002 at 800 rpm for 30 minutes. The mixture was then heated to 300°C at a rate of 2°C / min in an oxygen atmosphere and held for 10 hours to obtain a high-nickel cathode material.

[0056] Example 2 The high-nickel cathode material in this embodiment has a chemical composition of Li 1.015 Ni 0.933 Co 0.048 Mn 0.019 W 0.001 Zr 0.002 Al 0.005 Mg0.002 Y 0.001 B 0.02 Ti 0.001 It is O2, and its manufacturing method includes the following steps 1) to 4), 1) In this step, the hydroxide precursor of NCM9442, LiOH, and Co(OH)2 were mixed at a molar ratio of 1:1.05:0.01 at 800 rpm for 30 minutes. Then, the mixture was heated to 500°C at a rate of 2°C / min in an oxygen atmosphere and held for 8 hours to obtain a pre-sintered body. In step 2), the pre-sintered body was mixed with WO3, ZrO2, Al(OH)3, MgCO3, and Y2O3 at a molar ratio of 1:0.001:0.002:0.003:0.002:0.0005 at 800 rpm. The mixture was then heated to 750°C at a rate of 5°C / min in an oxygen atmosphere and held for 12 hours to obtain the primary sintered body. In step 3), the primary sintered body was washed with deionized water and then vacuum-dried at 120°C to obtain a washed and dried body. In (4), the washed and dried material was mixed with coating agents B2O3, Al2O3, and TiO2 in a molar ratio of 1:0.01:0.0015:0.001 at 800 rpm for 30 minutes, and the mixture was heated to 400°C at a rate of 2°C / min in an oxygen atmosphere and held for 12 hours to obtain a high-nickel cathode material.

[0057] Example 3 The high-nickel cathode material in this embodiment has a chemical composition of Li 1.01 Ni 0.923 Co 0.048 Mn 0.029 Ta 0.002 Zr 0.002 Ti 0.001 Mg 0.001 Y 0.001 B 0.01 Al 0.004 It is O2, and its manufacturing method includes the following steps 1) to 4), 1) In this method, the hydroxide precursor of NCM9343, LiOH, and cobalt acetate were mixed at 800 rpm for 30 minutes in a molar ratio of 1:1.05:0.01. The mixture was then heated to 450°C at a rate of 2°C / min in an oxygen atmosphere and held for 8 hours to obtain a pre-sintered body. In step 2), the pre-sintered body was mixed with Ta2O5, ZrO2, TiO2, MgO, and Y2O3 at a molar ratio of 1:0.001:0.002:0.001:0.001:0.0005 at 800 rpm. The mixture was then heated to 740°C at a rate of 5°C / min in an oxygen atmosphere and held for 12 hours to obtain the primary sintered body. In step 3), the primary sintered body was washed with deionized water and then vacuum-dried at 120°C to obtain a washed and dried body. In step 4), the washed and dried material was mixed with the coating agents H3BO3 and Al2O3 in a molar ratio of 1:0.01:0.002 at 800 rpm for 30 minutes, and the mixture was heated to 350°C at a rate of 2°C / min in an oxygen atmosphere and held for 8 hours to obtain a high-nickel cathode material.

[0058] Example 4 The high-nickel cathode material in this embodiment has a chemical composition of Li 1.015 Ni 0.905 Co 0.046 Mn 0.019 Mo 0.001 Nb 0.001 Zr 0.002 Al 0.005 Mg 0.002 Y 0.001 B 0.02 Ti 0.001 It is O2, and its manufacturing method includes the following steps 1) to 4), 1) In this process, NCM9145 precursor, LiOH, CoSO4, and CoCO3 were mixed at 800 rpm for 30 minutes in a molar ratio of 1:1.05:0.004:0.004. The mixture was then heated to 500°C at a rate of 2°C / min in an oxygen atmosphere and held for 8 hours to obtain a pre-sintered body. In step 2), the pre-sintered body was mixed with MoO3, Nb2O5, and ZrO2 in a molar ratio of 1:0.0005:0.0005:0.002 at 800 rpm. The mixture was then heated to 750°C at a rate of 5°C / min in an oxygen atmosphere and held for 12 hours to obtain the primary sintered body. In step 3), the primary sintered body was washed with deionized water and then vacuum-dried at 120°C to obtain a washed and dried body. In step 4), the washed and dried material was mixed with B2O3, Al2O3, and TiO2 in a molar ratio of 1:0.01:0.0015:0.001 at 800 rpm for 30 minutes. The mixture was then heated to 400°C at a rate of 2°C / min in an oxygen atmosphere and held for 12 hours to obtain a high-nickel cathode material.

[0059] Example 5 The high-nickel cathode material in this embodiment has a chemical composition of Li 1.01 Ni 0.906 Co 0.0477 Al 0.038 Mo 0.002 Zr 0.002 Sr 0.001 Y 0.001 B 0.01 Ti 0.002 It is O2, and its manufacturing method includes the following steps 1) to 4), 1) In this method, the hydroxide precursor of NC9505, Al(OH)3, LiOH, and Co2O3 were mixed at 800 rpm for 30 minutes in a molar ratio of 1:0.04:1.05:0.004. The mixture was then heated to 550°C at a rate of 2°C / min in an oxygen atmosphere and held for 8 hours to obtain a pre-sintered body. In step 2), the pre-sintered body was mixed with ammonium molybdate, ZrO2, SrO, and Y2O3 in a molar ratio of 1:0.002:0.002:0.001:0.0005 at 800 rpm. The mixture was then heated to 750°C at a rate of 5°C / min in an oxygen atmosphere and held for 12 hours to obtain the primary sintered body. In step 3), the primary sintered body was washed with deionized water and then vacuum-dried at 120°C to obtain a washed and dried body. In step 4), the washed and dried material was mixed with the coating agents H3BO3 and TiO2 in a molar ratio of 1:0.01:0.002 at 800 rpm for 30 minutes, and the mixture was heated to 300°C at a rate of 2°C / min in an oxygen atmosphere and held for 10 hours to obtain a high-nickel cathode material.

[0060] Example 6 The high-nickel cathode material in this embodiment has a chemical composition of Li 1.01 Ni 0.915 Co 0.056 Mn 0.029 S 0.002 Zr 0.002 Sr 0.001 Y0.001 B 0.01 Al 0.004 Ti 0.002 It is O2, and its manufacturing method includes the following steps 1) to 4), 1) In this method, the hydroxide precursor of NCM9253, LiOH, and Co2O3 were mixed at a molar ratio of 1:1.05:0.004 at 800 rpm for 30 minutes. Then, the mixture was heated to 550°C at a rate of 2°C / min in an oxygen atmosphere and held for 8 hours to obtain a pre-sintered body. In step 2), the pre-sintered body was mixed with Sb2O5, ZrO2, SrO, and Y2O3 in a molar ratio of 1:0.001:0.002:0.001:0.0005 at 800 rpm. The mixture was then heated to 750°C at a rate of 5°C / min in an oxygen atmosphere and held for 12 hours to obtain the primary sintered body. In step 3), the primary sintered body was washed with deionized water and then vacuum-dried at 120°C to obtain a washed and dried body. In step 4), the washed and dried material was mixed with the coating agents H3BO3, Al2O3, and TiO2 in a molar ratio of 1:0.01:0.002:0.002 at 800 rpm for 30 minutes. The mixture was then heated to 300°C at a rate of 2°C / min in an oxygen atmosphere and held for 10 hours to obtain a high-nickel cathode material.

[0061] Comparative Example 1 The high-nickel cathode material in this comparative example has the same chemical composition as Example 1, and its manufacturing method includes the following steps 1) to 3). 1) In this process, NCM9253 precursor, LiOH, Co2O3, ammonium molybdate, ZrO2, SrO, and Y2O3 were mixed at 800 rpm in a molar ratio of 1:1.05:0.004:0.002:0.002:0.001:0.0005. The mixture was then heated to 750°C at a rate of 5°C / min in an oxygen atmosphere and held for 12 hours to obtain a primary sintered body. In step 2), the primary sintered body was washed with deionized water and then vacuum-dried at 120°C to obtain a washed and dried body. In step 3), the washed and dried material was mixed with the coating agents H3BO3, Al2O3, and TiO2 in a molar ratio of 1:0.01:0.002:0.002 at 800 rpm for 30 minutes. The mixture was then heated to 300°C at a rate of 2°C / min in an oxygen atmosphere and held for 10 hours to obtain a high-nickel cathode material.

[0062] Comparative Example 2 The high-nickel cathode material in this comparative example has a chemical composition of Li 1.01 Ni 0.915 Co 0.056 Mn 0.029 Zr 0.002 Sr 0.001 Y 0.001 B 0.01 Al 0.004 Ti 0.002 It is O2, and its manufacturing method includes the following steps 1) to 4), 1) In this method, the hydroxide precursor of NCM9253, LiOH, and Co2O3 were mixed at a molar ratio of 1:1.05:0.004 at 800 rpm for 30 minutes. Then, the mixture was heated to 550°C at a rate of 2°C / min in an oxygen atmosphere and held for 8 hours to obtain a pre-sintered body. In step 2), the pre-sintered body was mixed with ZrO2, SrO, and Y2O3 in a molar ratio of 1:0.002:0.001:0.0005 at 800 rpm. The mixture was then heated to 750°C at a rate of 5°C / min in an oxygen atmosphere and held for 12 hours to obtain the primary sintered body. In step 3), the primary sintered body was washed with deionized water and then vacuum-dried at 120°C to obtain a washed and dried body. In (4), the washed and dried material was mixed with coating agents H3BO3, Al2O3, and TiO2 in a molar ratio of 1:0.01:0.002:0.002 at 800 rpm for 30 minutes, and the mixture was heated to 300°C at a rate of 2°C / min in an oxygen atmosphere and held for 10 hours to obtain a high-nickel cathode material.

[0063] Comparative Example 3 The high-nickel cathode material in this comparative example has the same chemical composition as Example 1, and its manufacturing method includes the following steps 1) to 3). 1) In this method, the hydroxide precursor of NCM9253, LiOH, and Co2O3 were mixed at a molar ratio of 1:1.05:0.004 at 800 rpm for 30 minutes. Then, the mixture was heated to 750°C at a rate of 2°C / min in an oxygen atmosphere and held for 8 hours to obtain a pre-sintered body. In step 2), the pre-sintered body was mixed with ammonium molybdate, ZrO2, SrO, and Y2O3 in a molar ratio of 1:0.002:0.002:0.001:0.0005 at 800 rpm. The mixture was then heated to 750°C at a rate of 5°C / min in an oxygen atmosphere and held for 12 hours to obtain the primary sintered body. In (3), the washed and dried material was mixed with coating agents H3BO3, Al2O3, and TiO2 in a molar ratio of 1:0.01:0.002:0.002 at 800 rpm for 30 minutes, and the mixture was heated to 300°C at a rate of 2°C / min in an oxygen atmosphere and held for 10 hours to obtain a high-nickel cathode material.

[0064] Experimental example

[0065] 1. The SEM characteristics of the high-nickel cathode material according to Example 1 were evaluated. Figure 1 is an SEM diagram of the high-nickel cathode material according to Example 1 of the present application. From Figure 1, it can be confirmed that the high-nickel cathode material according to Example 1 consists of secondary spherical particles formed by the aggregation of primary crystal grains.

[0066] 2. The following parameters were measured for the high-nickel cathode materials obtained in the above examples and comparative examples.

[0067] 1) The mass ratio A of cobalt and nickel elements at the grain boundaries on the surface of secondary particles and the content of the first dopant element. The measurement method involved observing the morphology of the sample surface using a scanning electron microscope (SEM), then selecting grain boundaries and performing EDS analysis to obtain the content of cobalt, nickel, and the first dopant element, and calculating the cobalt / nickel mass ratio A.

[0068] 2) The mass ratio C of cobalt and nickel elements in the primary crystal grains on the surface of the secondary particles and the content of the first dopant element. The measurement method involved observing the morphology of the sample surface using a scanning electron microscope (SEM), then selecting the center of the primary crystal grains and performing EDS analysis to obtain the content of cobalt, nickel, and the first dopant element, and calculating the cobalt / nickel mass ratio C.

[0069] 3) Mass ratio B of cobalt to nickel at grain boundaries in the core of secondary particles The measurement method involved ion milling the sample using an argon ion beam to obtain sliced ​​cathode particles. The sample cross-section was observed using a scanning electron microscope (SEM), and EDS analysis was performed on selected grain boundaries in the core of the secondary particles to obtain the content of cobalt, nickel, and the first dopant element. The cobalt / nickel mass ratio B was then calculated.

[0070] The measurement results for the above parameters are listed in Table 1.

[0071] 3. High-nickel cathode material, conductive agent Super-P, and adhesive PVDF are mixed in NMP solvent in a mass ratio of 96.5:1.5:2 and uniformly mixed to obtain a cathode slurry with a solid content of 30-40%. The cathode slurry has a surface density of approximately 20 mg / cm³. 2 The positive electrode current collector aluminum foil was coated with this material, and after drying, punching, and roller rolling, a positive electrode plate was obtained. The positive electrode plate, PP separator, and metallic lithium sheet described above were sequentially stacked and arranged, and 1.0 M of LiPF6 electrolyte was added to assemble an LR2430 type button battery. The following characteristics of the resulting button battery were then measured.

[0072] 1) Discharge capacity Measurement method: At room temperature, a button cell battery was charged to 4.25V with a constant current of 0.2C, then charged at a constant voltage of 4.25V until the cutoff current equaled 0.05C. After letting it stand for 5 minutes, it was discharged to 2.5V with a constant current of 0.2C, and the discharge capacity of the battery was recorded. Here, 1C = 200mA / g.

[0073] 2) Initial Coulomb efficiency Measurement method: At room temperature, a button cell was charged to 4.25V with a constant current of 0.2C, then charged at a constant voltage of 4.25V until the cutoff current equaled 0.05C, and the battery's charge capacity was recorded. After letting it stand for 5 minutes, it was discharged to 2.5V with a constant current of 0.2C, and the battery's discharge capacity was recorded. The initial Coulomb efficiency was calculated as discharge capacity / charge capacity × 100%. Here, 1C = 200mA / g.

[0074] The positive electrode plate, PP separator, and graphite negative electrode plate described above were sequentially stacked and arranged, and after winding, a battery cell was obtained. The battery cell was sealed in an aluminum plastic film, 1.0 M of LiPF6 electrolyte was injected, and after sealing and standing, chemical formation was carried out to obtain a complete battery. The following characteristics were measured for all the obtained batteries.

[0075] 3) Capacity retention rate after 300 cycles Measurement method: All batteries were placed in a constant temperature bath at 45°C. First, they were charged to 4.25V with a constant current of 0.2C. Then, they were charged at a constant voltage of 4.25V until the cutoff current reached 0.05C. After leaving them for 5 minutes, they were discharged to 2.8V with a constant current of 0.2C. The initial capacity a1 of the battery was recorded. After this, the charge-discharge cycle of charging at 0.2C and discharging at 0.2C was repeated 300 times. After this, the battery capacity was recorded as a2, and the capacity retention rate was recorded as a2 / a1 × 100%. Here, 1C = 200mA / g.

[0076] The measurement results for the above characteristics are listed in Table 1.

[0077] [Table 1]

[0078] From the data in Table 1, 1) The A values ​​of the high-nickel cathode materials in Examples 1 to 6 are all greater than the B and C values, the concentration of the first dopant element at the grain boundaries is relatively high, and all of the materials involved can improve the discharge capacity, initial Coulomb efficiency, and capacity retention rate of the battery. 2) As is clear from comparing Example 1 with Comparative Examples 1 and 3, although the chemical composition of the high-nickel cathode material is the same, when the pre-sintering process is not performed or the pre-sintering temperature is too high, the distribution of cobalt and nickel elements in the surface layer and core of the secondary particles, and in the grain boundaries and primary grains is similar, and the batteries obtained using the high-nickel cathode materials of Comparative Examples 1 and 3 have poor discharge capacity, initial Coulomb efficiency, and capacity retention rate. 3) As is clear from comparing Example 1 with Comparative Example 2, when high-valence metal elements with a valence higher than +5 are not added to the primary sintering for doping purposes, the concentration distribution of cobalt and nickel elements in the surface layer and core of the secondary particles, as well as in the grain boundaries and primary grains, is similar. It can be confirmed that the battery obtained using the high-nickel cathode material according to Comparative Example 2 has significantly worse discharge capacity, initial Coulomb efficiency, and capacity retention rate compared to the battery obtained using the high-nickel cathode material according to Example 1.

[0079] Finally, it should be noted that the above embodiments are intended to illustrate, and not limit, the technical solutions of the present application. However, the present application will be described in detail with reference to the above embodiments. Those skilled in the art will still be able to modify the technical solutions described in the above embodiments or make equivalent substitutions to some or all of their technical features, and these modifications or substitutions should be understood not to deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present application.

[0080] This application claims priority to a Chinese patent application filed with the China National Intellectual Property Administration on December 29, 2023, with application number 202311870331.6, titled "High Nickel Cathode Material, Method for Manufacturing the Same, and Applications," the entirety of which is incorporated into this application by reference.

Claims

1. A high-nickel cathode material, wherein the high-nickel cathode material is composed of secondary particles formed by the aggregation of primary crystal grains, and grain boundaries are included between adjacent primary crystal grains. A high-nickel cathode material in which the mass ratio of cobalt to nickel elements at the grain boundaries on the surface of the secondary particles is A, the mass ratio of cobalt to nickel elements at the grain boundaries on the core of the secondary particles is B, and the mass ratio of cobalt to nickel elements at the primary grains on the surface of the secondary particles is C, and A is greater than B, and A is greater than C.

2. The high-nickel cathode material according to claim 1, wherein the surface layer of the secondary particles contains a first dopant element, and the first dopant element is selected from at least one metallic element whose valence can reach +5 or higher.

3. The high-nickel cathode material according to claim 2, wherein the first dopant element is selected from at least one of Ta, Nb, Mo, and W.

4. The high-nickel cathode material according to claim 2 or 3, wherein the concentration of the first dopant element at the grain boundaries on the surface of the secondary particles is greater than the concentration of the first dopant element in the primary crystal grains on the surface.

5. The high-nickel cathode material according to any one of claims 1 to 4, wherein the secondary particles contain a second dopant element, and the second dopant element is selected from at least one of Zr, Al, Ti, Mg, Sc, Y, La, Sr, and B.

6. The surface of the secondary particles is covered with a coating layer, and the coating layer contains at least one element from among B, Al, Ce, Zr, Ti, and Si, according to any one of claims 1 to 5, a high nickel cathode material.

7. The chemical composition of the aforementioned high-nickel cathode material is Li ｎ Ni ｘ Co ｙ K ｚ M ａ N ｂ O ２ The high nickel cathode material according to any one of claims 1 to 6, wherein 0.95 < n < 1.1, 0.85 ≤ Ni < 1, 0 < y ≤ 0.15, 0 ≤ z ≤ 0.15, 0 < a ≤ 0.05, and 0 < b ≤ 0.05, K is selected from Mn or Al, M is selected from at least one of Al, Zr, Y, Ti, Sr, Ce, La, Mg, B, Si, Sc, and N is selected from at least one of Ta, Nb, Mo, W, Sb, Bi, V.

8. A method for manufacturing a high-nickel cathode material according to any one of claims 1 to 7, wherein the manufacturing method comprises the following steps 1) to 3): In step 1), a mixed system containing a precursor of high-nickel cathode material, a lithium source, and a cobalt source is pre-sintered in an oxygen-containing atmosphere to obtain a pre-sintered body. The pre-sintering temperature is 400 to 600°C, and the time is 4 to 10 hours. In step 2), the mixed system containing the pre-sintered body and the compound of the first dopant element is subjected to primary sintering in an oxygen-containing atmosphere to obtain a primary sintered body. The first dopant element is selected from at least one metallic element whose valence can reach +5 or higher. The temperature of the primary sintering was 650 to 800°C, and the time was 8 to 16 hours. Step 3) is a manufacturing method in which the first sintered product is second-sintered in an oxygen-containing atmosphere to obtain the high-nickel cathode material.

9. The manufacturing method according to claim 8, wherein in step 2), the mixed system further comprises a compound of a second dopant element, and the second dopant element is selected from at least one of Zr, Al, Ti, Mg, Sc, Y, La, Sr, and B.

10. Step 3) The secondary sintering includes sintering the mixed system of the first sintered product and the coating agent at 200 to 500°C for 8 to 16 hours. The manufacturing method according to claim 8 or 9, wherein the coating agent is selected from compounds containing a coating element, and the coating element is selected from at least one of B, Al, Ce, Zr, Ti, and Si.

11. A positive electrode plate comprising the high-nickel positive electrode material according to any one of claims 1 to 7.

12. A lithium-ion battery comprising the positive electrode plate described in claim 11.

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