A ternary positive electrode material precursor, a preparation method and application thereof

Abstract

The application provides a ternary positive electrode material precursor, a preparation method and application thereof, and has a chemical composition of Ni a Co b Mn c O2, wherein 0.5 < a < 0.95, 0 < b < 0.2, 0 < c < 0.3, the precursor is formed by agglomeration of a plurality of microparticles, the median particle size D50 of the precursor is 6-15 microns, and the porosity of the precursor is 20-40%. The ternary positive electrode material precursor provided by the application can remove residual alkali on the surface of the sintering product of the lithium source by water washing treatment in the process of preparing a ternary single-crystal positive electrode material, thereby avoiding the occurrence of a side reaction between the active material coated on the surface of the positive electrode material and the electrolyte to generate gas, and further affecting the cycle performance and storage performance of the material. Therefore, the ternary single-crystal positive electrode material prepared from the precursor can improve the cycle performance and storage performance of the lithium ion battery when applied to the lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and particularly relates to a ternary cathode material precursor, its preparation method, and its application. Background Technology

[0002] In recent years, with the introduction of my country's new energy strategy, the demand for lithium batteries in the power battery and energy storage system market has been continuously increasing. Cathode materials are a key factor determining the performance of lithium batteries. Currently, the commonly used cathode materials in power batteries are ternary cathode materials and lithium iron phosphate materials. As electric vehicles increasingly demand higher driving ranges, ternary cathode materials with higher energy density are gradually becoming the mainstream cathode materials for power batteries. Compared to ternary polycrystalline cathode materials, ternary single-crystal cathode materials have attracted widespread attention due to their better cycle stability.

[0003] Ternary single-crystal cathode materials are mostly obtained by crushing and coating the sintering products of ≤4μm ternary precursors and lithium sources. The reason for using ≤4μm ternary precursors is to achieve the required single-crystal size for the ternary cathode material through crushing. The coating process utilizes highly active materials, such as cobalt hydroxide, to reduce the residual alkali content in the sintering products. Other methods include lithium carbonate and lithium hydroxide, to further avoid the impact of residual alkali on the cathode material's capacity and cycle performance.

[0004] However, the presence of highly reactive materials also makes the coating layer more reactive. During battery application, it often reacts with the electrolyte, reducing the battery's cycle performance and storage performance. Summary of the Invention

[0005] The main objective of this invention is to provide a ternary cathode material precursor. When the ternary single-crystal cathode material prepared from this precursor is applied to lithium-ion batteries, it can improve the cycle performance and storage performance of lithium-ion batteries.

[0006] The present invention also provides a method for preparing a ternary cathode material precursor, which can prepare the above-mentioned ternary cathode material precursor, and the process is simple and low in cost.

[0007] The present invention also provides a ternary single-crystal cathode material, which, when applied to lithium-ion batteries, can improve the cycle performance and storage performance of lithium-ion batteries.

[0008] The present invention also provides a method for preparing a ternary single-crystal cathode material, which can prepare the above-mentioned ternary single-crystal cathode material, and the process is simple and low in cost.

[0009] The present invention also provides a positive electrode sheet, which, since includes the above-mentioned ternary single crystal positive electrode material, can improve the cycle performance and storage performance of lithium-ion batteries when used in lithium-ion batteries.

[0010] The present invention also provides a lithium-ion battery, which, because it includes the above-mentioned positive electrode, has good cycle performance and storage performance.

[0011] In a first aspect, the present invention provides a ternary cathode material precursor having the chemical composition shown in Formula 1, wherein the precursor is composed of multiple microparticles aggregated together, and the median particle size D50 of the precursor is 6-15 μm.

[0012] The porosity of the precursor is 20-40%;

[0013] Ni a Co b Mn c O2, Formula 1,

[0014] Among them, 0.5 < a < 0.95, 0 < b < 0.2, and 0 < c < 0.3.

[0015] The ternary cathode material precursor described above has a specific surface area of ​​40-80 m². 2 / g.

[0016] In the ternary cathode material precursor described above, the median particle size D50 of the microparticles is 100-300 nm.

[0017] Secondly, the present invention provides a method for preparing the above-mentioned ternary cathode material precursor, comprising the following steps:

[0018] 1) The system including nickel source, cobalt source and manganese source is kept in an oxygen-containing atmosphere at a temperature of 300-600℃ for 3-10h to obtain the first particle;

[0019] 2) The first particle is subjected to a first crushing process until nanoparticles with a median particle size D50 of 100-300nm are obtained, and the nanoparticles are mixed with deionized water to form a slurry system.

[0020] 3) The slurry system is spray-dried, with the feed rate controlled at 1-3 L / h, the inlet temperature at 100-180℃, and the outlet temperature at 80-120℃, to obtain the ternary cathode material precursor.

[0021] In the preparation method of the ternary cathode material precursor described above, the mass ratio of the nanoparticles to deionized water is 1:9-4:6.

[0022] Thirdly, the present invention provides a ternary single-crystal cathode material having the chemical composition shown in Formula 2, wherein the median particle size D50 of the ternary single-crystal cathode material is 1-3 μm and the residual alkali content is 0.05-0.25%.

[0023] Li x Ni d Co e Mn f M g O2 / Q, equation 2,

[0024] Wherein, M includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti, Q includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti, 1 < x < 1.2, 0.5 < d < 0.95, 0 < e < 0.2, 0 < f < 0.3, 0 ≤ g < 0.06, and d + e + f + g = 1.

[0025] Fourthly, the present invention provides a method for preparing the above-mentioned ternary single-crystal cathode material, comprising the following steps:

[0026] 1) The raw material system including the above-mentioned ternary cathode material precursor, lithium source and dopant element M is kept at 700-900℃ for 10-15h in an oxygen-containing atmosphere to obtain the second particle.

[0027] 2) Wash the second particle with deionized water for 2-10 min, controlling the rotation speed at 100-200 r / min, and then centrifuge and dry to obtain the dried product;

[0028] 3) The dried product is subjected to a second crushing process until a crushed product with a median particle size D50 of 1-3 μm is obtained;

[0029] 4) The system including the crushed product and the coating material Q is kept at an oxygen-containing atmosphere and a temperature of 250-700℃ for 10-15 hours to obtain a ternary single crystal cathode material.

[0030] In the preparation method of the ternary single-crystal cathode material described above, the mass ratio of the second particle to deionized water is 0.6-1.2:1.

[0031] Fifthly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the above-mentioned ternary single crystal positive electrode material or a ternary single crystal positive electrode material prepared by the above-mentioned preparation method.

[0032] In a sixth aspect, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the above-described positive electrode sheet.

[0033] This invention provides a ternary cathode material precursor. The precursor's chemical composition is a nickel-cobalt-manganese oxide, composed of multiple microparticles with a specific D50 and porosity. During the preparation of the ternary single-crystal cathode material, residual alkali on the surface of the sintered product with the lithium source can be removed by water washing. This avoids side reactions between the active material coated on the cathode material surface and the electrolyte, preventing the generation of gas and thus affecting the material's cycle performance and storage performance. Therefore, the ternary single-crystal cathode material prepared from this precursor, when applied to lithium-ion batteries, can improve the cycle performance and storage performance of lithium-ion batteries. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a SEM image of the ternary cathode material precursor prepared in Example 1 of the present invention;

[0036] Figure 2 This is a cross-sectional SEM image of the ternary cathode material precursor prepared in Example 1 of the present invention;

[0037] Figure 3 This is a SEM image of the second particle prepared in Example 1 of the present invention;

[0038] Figure 4 This is a SEM image of the ternary single-crystal cathode material prepared in Example 1 of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0040] This invention provides a ternary cathode material precursor having the chemical composition shown in Formula 1. The precursor is composed of multiple microparticles aggregated together, and the median particle size D50 of the precursor is 6-15 μm.

[0041] The porosity of the precursor is 20-40%;

[0042] Nia Co b Mn c O2, Formula 1,

[0043] Among them, 0.5 < a < 0.95, 0 < b < 0.2, and 0 < c < 0.3.

[0044] It is understood that in this invention, D50 refers to the particle size of the precursor when the cumulative volume percentage reaches 50%, calculated from the minimum particle size, and is usually called the median particle size; porosity refers to the percentage of pore volume in the precursor to the total volume of the precursor.

[0045] The ternary cathode material precursor of the present invention is a secondary particle composed of multiple microparticles aggregated together. The median particle size D50 of the precursor is 6-15 μm; the porosity is 20-40%, and the chemical composition of the precursor is: Ni a Co b Mn c O2, where 0.5 < a < 0.95, 0 < b < 0.2, 0 < c < 0.3.

[0046] In existing technologies, small-particle-size (≤4μm) ternary precursors are used to prepare ternary single-crystal cathode materials. Because the precursor particle size is small, the sintering product of the precursor and lithium source also has a small particle size. When the sintering product is washed with water to remove residual alkali, lithium deficiency occurs due to over-washing. Furthermore, material loss, low efficiency, and low production capacity occur during centrifugation and drying processes. Therefore, existing technologies typically use the method of coating the surface of the ternary single-crystal cathode material with active material to remove residual alkali. However, the active material is prone to side reactions with the electrolyte, generating gas, which affects the battery's cycle performance and storage performance. This invention controls the D50 of the ternary material precursor to be 6-15μm, which is larger than the particle size of precursors conventionally used in preparing ternary single-crystal cathode materials. Because the ternary cathode material precursor of this invention has a large D50 and a large specific surface area, the product after sintering the precursor with the lithium source can still maintain agglomerates with a large D50. Furthermore, due to the large specific surface area and relatively loose internal pore structure of the precursor, Li can more easily diffuse into the precursor for reaction during the sintering of the material and Li salt. Additionally, since the precursor of this invention is composed of nanoparticles, it has high reactivity, which is beneficial for single crystal growth, making it easier for primary particles to reach the particle size required for single crystals. On the one hand, when using water washing to remove residual alkali from the sintered product, over-washing can be avoided, allowing lithium loss during the washing process to be controlled, retaining more active lithium for the cathode material, and ensuring the energy density and cycle performance of the battery. On the other hand, replacing the coating of the ternary cathode material with active material through water washing reduces the impact of residual alkali and avoids the phenomenon of side reactions between the active material and the electrolyte producing gas, further improving the storage performance and cycle performance of the ternary cathode material.

[0047] It is worth noting that this invention not only controls the D50 of the ternary material precursor to be 6-15 μm, but also controls its porosity. On the one hand, controlling the D50 to 6-15 μm ensures processing performance during the washing process, guarantees material yield, and avoids over-washing. On the other hand, controlling the precursor porosity to 20-40% ensures that Li can enter the precursor interior through larger pores during the reaction, resulting in a more complete internal reaction, allowing grains to grow sufficiently even with D50 > 4 μm. Traditional precursors have a lower specific surface area, making Li diffusion from the outside in difficult. When D50 > 4 μm, internal particles do not easily grow sufficiently to reach single-crystal particle size. Therefore, traditional single-crystal sintering uses precursors with D50 ≤ 4 μm. In summary, when the current driving material has a D50 of 6-15μm and a porosity of 20-40%, it can ensure high yield and high processing efficiency of the material during the washing process and solve the problem of overwashing. Furthermore, it can obtain ternary single-crystal cathode materials that meet the single-crystal size requirements through subsequent crushing treatment.

[0048] Therefore, by controlling the particle size and porosity of the ternary cathode material precursor within a suitable range, the ternary single-crystal cathode material that meets the single-crystal size requirements can be obtained by washing and crushing the sintering product after sintering the precursor with the lithium source. Moreover, the residual alkali content on the surface of the ternary single-crystal cathode material is extremely low. When applied to lithium-ion batteries, it can improve the cycle performance and storage performance of lithium-ion batteries.

[0049] The present invention does not limit the test method for the D50 of the above-mentioned precursor; for example, a laser particle size analyzer can be used for measurement.

[0050] The present invention does not limit the test method for the porosity of the above-mentioned precursor; for example, the water displacement method can be used for measurement.

[0051] In this embodiment, the ternary cathode material precursor is a nickel-cobalt-manganese oxide composed of multiple microparticles with a unique D50 and porosity. During the preparation of the ternary single-crystal cathode material, this precursor can be washed with water to remove residual alkali from the surface of the sintered product with the lithium source, thus avoiding the impact of residual alkali on the cycle performance of the cathode material. It also prevents over-washing of the sintered product due to excessively small precursor particle size. Furthermore, it avoids side reactions between the active material coated on the cathode material surface and the electrolyte, preventing the generation of gas that could affect the material's cycle and storage performance. This ternary cathode material precursor can be used to prepare ternary single-crystal cathode materials that meet the single-crystal size requirements. Therefore, the ternary single-crystal cathode material prepared from this precursor, when applied to lithium-ion batteries, can improve the cycle and storage performance of lithium-ion batteries.

[0052] In some embodiments of the present invention, the specific surface area of ​​the precursor is 40-80 m². 2 / g.

[0053] As we understand it, specific surface area is the total surface area of ​​particles per unit volume or unit mass. The specific surface area of ​​the precursor directly affects the specific surface area of ​​the cathode material, which in turn affects the capacity utilization of the active material in the cathode material, and consequently affects the rate performance and cycle performance of the battery.

[0054] In one embodiment, the precursor has a D50 of 6-15 μm and a porosity of 20-40%, and the specific surface area of ​​the precursor is controlled to be 40 m². 2 / g-80m 2 / g, within a suitable range, therefore, the specific surface area of ​​the cathode material prepared using this precursor is more suitable, the cathode material has more active sites on its surface, the interfacial impedance of the material is reduced, which is more conducive to the insertion of active ions (such as lithium ions), reduces the electrochemical polarization of the cathode material, and its capacity is high, thus improving the rate performance and cycle performance of the battery.

[0055] The precursor prepared by this invention has a specific surface area of ​​40-80 m². 2 / g, while having a large internal porosity and composed of nano-sized primary particles, it has higher activity and more sufficient contact with lithium salt during sintering, which makes lithium diffusion easier and grain growth easier. Therefore, it can achieve the target single crystal size requirement while maintaining an agglomerated state.

[0056] The present invention does not limit the method for testing the specific surface area of ​​the above-mentioned precursor; for example, the adsorption method can be used for measurement.

[0057] In this embodiment, the specific surface area of ​​the precursor is controlled to be 60m². 2 / g-80m 2 / g, within a suitable range, so that the specific surface area of ​​the prepared ternary cathode material is more suitable, thereby improving the electrochemical activity such as cycle performance and rate performance of lithium-ion batteries.

[0058] In some embodiments of the present invention, the median particle size D50 of the microparticles is 100-300 nm.

[0059] The median particle size D50 of the microparticles in the ternary cathode material precursor directly affects the D50 of the cathode material. In this embodiment, the median particle size D50 of the microparticles is controlled to be 100-300nm.

[0060] It is understandable that microparticles are a component of the precursor of ternary cathode materials. During the preparation of ternary cathode materials from precursors, microparticles undergo a series of changes and ultimately become a component of the ternary cathode material. Therefore, the properties of microparticles affect the properties of ternary cathode materials to a certain extent. The median particle size D50 of the microparticles provided in this embodiment is within a suitable range, which makes the D50 of the prepared ternary cathode material more suitable. When the particle size of the ternary cathode material is too large, the processing performance is good, but its capacity utilization is low, resulting in poor rate performance and cycle performance of the battery. When the particle size of the ternary cathode material is too small, its electrochemical performance is good and its activity is high, but the material is prone to agglomeration and difficult to disperse, leading to difficulties in electrode processing. Specifically, this can be reflected in the easy agglomeration during the preparation of cathode slurry, uneven coating, and easy foil detachment during slurry mixing.

[0061] In this embodiment, the microparticle D50 is 100-300nm. The smaller the microparticle D50, the larger the contact area with the lithium salt, and the easier it is for the lithium salt to diffuse. This promotes the reaction between the microparticles and the lithium salt, as well as grain growth, and enables the primary particle size of the single-crystal cathode material to reach 1-3μm.

[0062] The present invention does not limit the test method for the D50 of the above-mentioned microparticles; for example, a laser particle size analyzer can be used for measurement.

[0063] In this embodiment, the median particle size D50 of the microparticles in the precursor is controlled to be 100-300 nm, which is within a suitable range. This makes the D50 of the prepared ternary cathode material more suitable, and the cathode material is less likely to agglomerate during use. It also enables the lithium-ion battery to have good cycle stability and rate performance, as well as other electrochemical activities.

[0064] Secondly, the present invention provides a method for preparing the above-mentioned ternary cathode material precursor, comprising the following steps:

[0065] 1) The system including nickel source, cobalt source and manganese source is kept in an oxygen-containing atmosphere at a temperature of 300-600℃ for 3-10h to obtain the first particle;

[0066] 2) The first particle is subjected to a first crushing process until nanoparticles with a median particle size D50 of 100-300nm are obtained, and the nanoparticles are mixed with deionized water to form a slurry system.

[0067] 3) The slurry system is spray-dried, with the feed rate controlled at 1-3 L / h, the inlet temperature at 100-180℃, and the outlet temperature at 80-120℃, to obtain the ternary cathode material precursor.

[0068] In this embodiment, by controlling the mixing order of the raw materials and the conditions of each process, the above-mentioned ternary cathode material precursor is finally prepared.

[0069] Specifically, in step 1), the nickel source, cobalt source, and manganese source are first mixed in a certain proportion to obtain a mixture. Then, the mixture is kept at a temperature of 300-600℃, preferably 400-500℃, in an oxygen-containing atmosphere for 3-10 hours, preferably 5-7 hours, to obtain the first particles. Exemplarily, the nickel source can be one or more of nickel oxide, nickel carbonate, nickel acetate, nickel oxalate, nickel sulfate, and nickel hydroxide; the cobalt source can be one or more of cobalt oxide, cobalt carbonate, cobalt acetate, cobalt oxalate, cobalt sulfate, and cobalt hydroxide; and the manganese source can be one or more of manganese oxide, manganese carbonate, manganese acetate, manganese oxalate, manganese sulfate, and manganese hydroxide. The nickel, cobalt, and manganese sources can be added in the proportions provided by the chemical composition of the ternary cathode material precursor. After uniform mixing, a mixture is obtained and heated to 300-600℃ at a heating rate of 2-5℃ / min. The mixture is then held at this temperature for 3-10 hours in an oxygen-containing atmosphere, i.e., sintering. Because the sintering is carried out in an oxygen-containing atmosphere, the first particles obtained after sintering are oxides. The purpose of this sintering is to transform the powdered material into a dense body. After sintering, the first particles can be cooled, for example, to below 80℃.

[0070] This invention does not limit the method of mixing the nickel, cobalt, and manganese sources, as long as the nickel, cobalt, and manganese sources can be mixed uniformly. For example, the nickel, cobalt, and manganese sources can be mixed by ball milling or mechanical mixing.

[0071] This invention does not limit the oxygen content in the oxygen-containing atmosphere, as long as it allows the material to form oxides after sintering. For example, the oxygen content in the oxygen-containing atmosphere can be greater than or equal to 25%.

[0072] In step 2), the first particle obtained above is subjected to a crushing process to obtain nanoparticles with a median particle size D50 of 100-300 nm. The nanoparticles are then mixed with deionized water to form a slurry system. Specifically, the cooled first particle is first subjected to a crushing process, which can be carried out by ball milling or sand milling, in order to disperse the particles that are stuck together to obtain nanoparticles with a particle size of 100-300 nm. The nanoparticles are then mixed with deionized water to form a slurry system.

[0073] In step 3), the slurry system formed above is subjected to spray drying, with the feed rate controlled at 1-3 L / h, the inlet temperature at 100-180℃, and the outlet temperature at 80-120℃, finally obtaining the above-mentioned ternary cathode material precursor. The spray drying can be carried out using spray drying equipment. Through spray drying, multiple microparticles can agglomerate into large secondary spherical precursor particles during the drying process of the slurry system.

[0074] Nanoparticles with a D50 of 100-300 nm are formed into a slurry system, and then the slurry system is spray-dried. The feed rate during the spray drying process is controlled at 1-3 L / h, and the inlet and outlet temperatures are controlled. Finally, a ternary cathode material precursor with a D50 of 6-15 μm and a porosity of 20-40% can be prepared.

[0075] Since the first particle is an oxide, it is crushed to obtain nanoparticles. After the nanoparticles are formed into a slurry system and then spray-dried, the resulting ternary cathode material precursor is also an oxide.

[0076] The preparation method of this embodiment can prepare ternary cathode material precursors with the above-mentioned particle size and porosity. Compared with the traditional co-precipitation method, this preparation method has low cost, high efficiency, high production capacity, and can also reduce wastewater discharge.

[0077] In some embodiments of the present invention, the mass ratio of the nanoparticles to deionized water is 1:9-4:6.

[0078] In one embodiment, the mass ratio of nanoparticles to deionized water can be controlled to be 1:9-4:6 to better slurry the nanoparticles.

[0079] Optionally, the mass ratio of nanoparticles to deionized water can be any value between 1:9, 2:8, 3:7, or 1:9-4:6.

[0080] By controlling the mass ratio of nanoparticles to deionized water within a suitable range and then controlling the conditions of spray drying, the ternary cathode material precursor obtained after spray drying can meet the above-mentioned particle size and porosity.

[0081] In this embodiment, the mass ratio of nanoparticles to deionized water is controlled to be 1:9-4:6, which allows the nanoparticles to be better slurried, thereby obtaining the above-mentioned ternary cathode material precursor after spray drying of the slurry system.

[0082] Thirdly, the present invention provides a ternary single-crystal cathode material, which is prepared from the ternary cathode material precursor of the first aspect or the ternary cathode material precursor obtained by the preparation method of the second aspect.

[0083] The above-mentioned ternary single-crystal cathode material has the chemical composition shown in Formula 2, wherein the median particle size D50 of the ternary single-crystal cathode material is 1-3 μm, and the residual alkali content is 0.05-0.25%;

[0084] Li x Ni d Co e Mn f M g O2 / Q, equation 2,

[0085] Wherein, M includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti, Q includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti, 1 < x < 1.2, 0.5 < d < 0.95, 0 < e < 0.2, 0 < f < 0.3, 0 ≤ g < 0.06, and d + e + f + g = 1.

[0086] The chemical composition of the ternary single-crystal cathode material in this embodiment is: Li x Ni d Co e Mn f M g O2 / Q, wherein M includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti, Q includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti, 1 < x < 1.2, 0.5 < d < 0.95, 0 < e < 0.2, 0 < f < 0.3, 0 ≤ g < 0.06, and d + e + f + g = 1.

[0087] In one embodiment, the median particle size D50 of the ternary single-crystal cathode material is 1-3 μm, the residual alkali content is 0.05-0.25%, and its chemical composition is: Li x Ni d Co e Mn f M g O2 / Q, wherein M includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti, Q includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti, 1 < x < 1.2, 0.5 < d < 0.95, 0 < e < 0.2, 0 < f < 0.3, 0 ≤ g < 0.06, and d + e + f + g = 1.

[0088] The particle size of ternary single-crystal cathode materials, used as cathode materials for lithium-ion batteries, has a certain impact on the performance of the prepared lithium-ion batteries. Smaller particle sizes result in larger specific surface areas, which is beneficial for lithium-ion insertion and extraction, reduces the diffusion path of lithium ions within the battery, and improves the electrochemical reactivity of the electrode, thereby enhancing the battery's rate performance. Simultaneously, smaller particle sizes in ternary single-crystal cathode materials facilitate lithium-ion diffusion within the electrode, further improving the battery's electrochemical performance. However, if the particle size of the ternary single-crystal cathode material is too small, the particles are prone to agglomeration; if the particle size is too large, the diffusion path of lithium ions within the battery increases, leading to a decrease in the electrochemical reactivity of the lithium-ion battery. Therefore, in this embodiment, the median particle size D50 of the ternary single-crystal cathode material is controlled at 1-3 μm, within a suitable range. In addition, the residual alkali content of the ternary single crystal cathode material in this embodiment is 0.05-0.25%, which is extremely low. This avoids the impact of residual alkali on the capacity and cycle performance of the cathode material, and can meet the requirements of lithium-ion battery use. There is no need to remove residual alkali by washing or surface coating, thereby improving the storage performance of the cathode material.

[0089] In addition, by coating at least part of the outer surface of the core, the coating layer can protect the cathode material from interference from the external environment, thereby improving the safety performance of the battery. At the same time, the metal oxide coating on the surface has good conductivity, which can further improve the conductivity of the cathode material, thereby improving the charge and discharge performance of the battery.

[0090] The present invention does not limit the test method for the median particle size D50 of the above-mentioned ternary single crystal cathode material. For example, it can be measured by scanning electron microscopy (SEM).

[0091] The present invention does not limit the test method for the residual alkali content of the above-mentioned ternary single crystal cathode material; for example, titration can be used for testing.

[0092] The ternary single-crystal cathode material provided in this embodiment has a small particle size, low residual alkali content, and an outer surface coating. When used in lithium-ion batteries, it can improve the battery's energy density, rate performance, storage performance, and cycle performance.

[0093] Fourthly, the present invention provides a method for preparing the above-mentioned ternary single-crystal cathode material, comprising the following steps:

[0094] 1) The raw material system including the above-mentioned ternary cathode material precursor, lithium source and dopant element M is kept at 700-900℃ in an oxygen-containing atmosphere for 10-15 hours to obtain the second particle;

[0095] 2) Wash the second particle with deionized water for 2-10 min, controlling the rotation speed at 100-200 r / min, and then centrifuge and dry to obtain the dried product;

[0096] 3) The dried product is subjected to a second crushing process until a crushed product with a median particle size D50 of 1-3 μm is obtained;

[0097] 4) The system including the crushed product and the coating material Q is kept at an oxygen-containing atmosphere and a temperature of 250-700℃ for 10-15 hours to obtain a ternary single crystal cathode material.

[0098] In this embodiment, by controlling the mixing order of the raw materials and the conditions of each process, the above-mentioned ternary single-crystal cathode material is finally prepared.

[0099] Specifically, in step 1), the raw material system comprising the aforementioned ternary cathode material precursor, lithium source, and dopant element M is heated at 700-900℃ in an oxygen-containing atmosphere for 10-15 hours to obtain the second particle. This heating process is essentially a sintering treatment. The purpose of this sintering treatment is to allow lithium and dopant element M to penetrate into the aforementioned ternary cathode material precursor, promoting reaction kinetics and further improving the electrochemical performance of the cathode material, thereby enhancing the cycle performance and specific capacity of the lithium-ion battery. The lithium source is one or more of lithium hydroxide and lithium carbonate; the dopant element M includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti. The sintering temperature is maintained at 700-900℃, preferably 800-900℃. Too low a sintering temperature is not conducive to the uniform distribution of the lithium source and dopant element M in the precursor, while too high a temperature will damage the precursor structure and easily cause oxygen defects. The molar ratio of the lithium source to the total transition metal elements in the precursor, namely nickel, cobalt, and manganese, is 1.02-1.2:1. This reduces the mixing of lithium and nickel elements in the material, resulting in second particles with better structural integrity. Because the lithium source is added in excess, some residual alkali will remain on the surface of the second particles. Too low a lithium source will affect the specific capacity of the cathode material, while too high a lithium source will increase the amount of residual alkali on the material surface. Furthermore, doping the crystal lattice with other elements can stabilize the crystal structure of the material.

[0100] In step 2), the second particles are washed with deionized water for 2-10 minutes, with the rotation speed controlled at 100-200 r / min during the washing process. After washing, they are centrifuged and dried to obtain the dried product. The purpose of washing the second particles is to remove residual alkali from their surface. Because the ternary cathode material precursor has a large particle size, the second particles formed after sintering with the lithium source and dopant element M also have a large particle size and a small specific surface area. Therefore, during the washing process to remove residual alkali, less surface area is exposed to the aqueous solution, which can avoid over-washing due to excessively small particle size, thus preventing lithium deficiency. Controlling the washing time to 2-10 minutes, preferably 4-8 minutes, and controlling the rotation speed at 100-200 r / min during the washing process can achieve better removal of residual alkali, resulting in extremely low residual alkali content on the material surface. The washed second particles are then centrifuged and dried again, and the resulting dried product has a particle size of 1.5-4.0 μm and is in a secondary spherical agglomeration state. During centrifugation and drying, the loss of a large amount of material, low efficiency, and low production capacity caused by excessively small particle size can be avoided.

[0101] In step 3), the dried product is subjected to a second crushing process until a crushed product with a median particle size D50 of 1-3 μm is obtained. For example, the second crushing process can be carried out using an air jet mill, and after pulverizing the larger-sized dried product using an air jet mill, a crushed product with a D50 of 1-3 μm can be obtained.

[0102] In step 4), the system comprising the crushed products and the coating material Q is heated in an oxygen-containing atmosphere at a temperature of 250-700℃ for 10-15 hours to obtain a ternary single-crystal cathode material. This step involves coating the surface of the ternary single-crystal cathode material with a layer of metal oxide to protect it. The purpose of the sintering treatment is to coat the outer surface of the ternary single-crystal cathode material with the coating material Q in the form of metal oxide, thereby protecting the cathode material and improving its structural stability. The coating material Q includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti. Limiting the sintering temperature to 250-700℃ ensures that the coating material Q coats the outer surface of the ternary single-crystal cathode material in the form of oxide, without penetrating the core and damaging its crystal structure.

[0103] This invention does not limit the oxygen content in the oxygen-containing atmosphere, as long as it allows the material to form oxides after sintering. For example, the oxygen content in the oxygen-containing atmosphere can be greater than or equal to 25%.

[0104] The preparation method of this embodiment can prepare ternary single crystal cathode materials with the above-mentioned particle size and residual alkali content. The residual alkali is removed by water washing during the preparation process, so there is no need to remove residual alkali from the prepared cathode material. The preparation method is simple and low in cost.

[0105] In some embodiments of the present invention, the mass ratio of the second particle to deionized water is 0.6-1.2:1.

[0106] In one embodiment, the mass ratio of the second particle to deionized water can be controlled to be 0.6-1.2:1, preferably 0.8-1:1, so as to better slurry the second particle.

[0107] Optionally, the mass ratio of the second particle to deionized water can be 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1 or any value between 0.6 and 1.2:1.

[0108] When washing the second particle, controlling the mass ratio of the second particle to deionized water within a suitable range can achieve a better cleaning effect on the second particle.

[0109] In this embodiment, the mass ratio of the second particle to deionized water is controlled at 0.6-1.2:1, which can improve the cleaning effect of the second particle and result in a low residual alkali content in the final ternary single crystal cathode material, which can meet the requirements of lithium-ion batteries.

[0110] Fifthly, the present invention provides a positive electrode sheet, the positive electrode sheet comprising the above-mentioned ternary single crystal positive electrode material or a ternary single crystal positive electrode material prepared by the above-mentioned preparation method.

[0111] The positive electrode sheet of the present invention can be prepared using conventional techniques in the art. Specifically, the above-mentioned positive electrode material, conductive agent, and binder can be uniformly dispersed in a solvent to obtain a positive electrode active layer slurry. Then, the positive electrode active layer slurry is coated on at least one functional surface of the positive electrode current collector, and after drying, the positive electrode sheet of the present invention can be obtained.

[0112] This invention does not specifically limit the types of conductive agents and adhesives. The conductive agents, adhesives and other components can all be conventional substances in the field. For example, the conductive agent can be selected from one or more of conductive carbon black, carbon nanotubes, conductive graphite and graphene, and the adhesive can be selected from one or more of polyvinylidene fluoride (PVDF), acrylic modified PVDF, polyacrylate polymers, polyimide, styrene-butadiene rubber and styrene-acrylic rubber.

[0113] The present invention does not specifically limit the coating method, and any coating method such as gravure coating, extrusion coating, spraying, screen printing, etc. can be used to achieve the coating of the positive electrode active layer slurry.

[0114] In a sixth aspect, the present invention provides a lithium-ion battery, the lithium-ion battery comprising the above-described positive electrode sheet.

[0115] The lithium-ion battery of the present invention includes, in addition to the positive electrode, a separator, a negative electrode, and an electrolyte. The composition of the negative electrode can refer to conventional negative electrode sheets in the art, and the separator can also be a separator commonly used in the art, such as a PP film or a PE film.

[0116] The lithium-ion battery of the present invention can be prepared using conventional methods in the art. Specifically, the positive electrode, separator and negative electrode can be stacked in sequence, and the cell can be obtained by stacking or winding process. Then, the lithium-ion battery can be obtained by baking, liquid injection, formation and packaging.

[0117] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0118] Example 1

[0119] The preparation method of the ternary single-crystal cathode material in this embodiment includes the following steps:

[0120] 1) Mix nickel oxide, cobalt oxide and manganese oxide in a molar ratio of 0.83:0.12:0.05 to obtain a mixture. Then, heat the mixture to 450℃ at a heating rate of 2-5℃ / min under an oxygen atmosphere. Record this temperature as temperature 1. Hold the mixture at this temperature for 6 hours. Record this time as time 1. The first particle is obtained.

[0121] 2) The first particle was milled to obtain nanoparticles with a D50 of 220 nm. The nanoparticles were then mixed with deionized water at a mass ratio of 2:8 to form a slurry system.

[0122] 3) Spray drying is performed on the slurry system, with the feed rate controlled at 3L / min, the inlet temperature at 150℃, and the outlet temperature at 100℃, to obtain a ternary cathode material precursor composed of multiple microparticles.

[0123] 4) The ternary cathode material precursor, lithium hydroxide and dopant element M (Al in this case) are mixed. The molar ratio of lithium to the total molar ratio of nickel, cobalt and manganese elements in the precursor and the molar ratio of Al is 1.02:1:0.005. The system is heated to 800℃ at a heating rate of 2-5℃ / min in an oxygen atmosphere, which is recorded as temperature 2. The temperature is held for 12h, which is recorded as time 2, to obtain the second particle.

[0124] 5) Add deionized water to the second particle, wherein the mass ratio of the second particle to deionized water is 0.9:1, wash for 6 min, control the rotation speed at 150 r / min, centrifuge and dry to obtain the dried product;

[0125] 6) The dried product was pulverized by air jet milling to obtain a ternary single-crystal cathode material with a D50 of 2.1 μm;

[0126] 7) The ternary single-crystal cathode material and the coating material Q (Mo) are mixed, wherein the molar ratio of the coating material Q to the dopant element M is 1:1. The mixture is sintered at 500°C in an oxygen atmosphere to obtain a ternary single-crystal cathode material with a coating layer.

[0127] The residual alkali content of ternary single-crystal cathode materials was tested by titration.

[0128] Example 2-16

[0129] The preparation methods of the ternary single-crystal cathode materials in Examples 2-16 are basically the same as those in Example 1, except that one or more of the preparation conditions in steps 1)-3) are changed. The specific parameters are shown in Table 1.

[0130] Examples 17-26

[0131] The preparation methods of the ternary single-crystal cathode materials in Examples 17-26 are basically the same as those in Example 1, except that one or more of the preparation conditions in steps 4)-6) are changed. The specific parameters are shown in Table 2.

[0132] Comparative Example 1

[0133] The preparation method of the ternary single-crystal cathode material in this comparative example includes the following steps:

[0134] 1) Prepare a 1.5 mol / L solution A by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 0.83:0.12:0.05; prepare a 5 mol / L solution B by mixing NaOH as a precipitant; and prepare a 2 mol / L solution C by mixing ammonia.

[0135] 2) Simultaneously introduce solutions A, B, and C into the reaction vessel, control the pH at 10-11, the reaction temperature at 60℃, the stirring speed at 250rpm, and the ammonia value at 7g / L. Stop when the D50 reaches 3.5μm.

[0136] 3) After the reaction, the material is washed with alkali and water to remove Na / S impurities, and then dried at 100℃ to obtain precursor particles.

[0137] 4) The obtained precursor particles are mixed with lithium hydroxide and dopant M (Al in this case) in a molar ratio of 1:1.02:0.005 and then sintered once at 800℃ in an oxygen-containing atmosphere. The sintered material is then subjected to air jet milling to obtain ternary single crystal cathode material D with a particle size of 2.1μm.

[0138] 5) Mix the ternary single crystal cathode material D and deionized water in a 1:1 ratio, stir at 150 rpm for 5 minutes, and then centrifuge and dry to obtain product E.

[0139] 6) Mix E and coating agent Q (Mo in this case), wherein the molar ratio of coating agent Q to dopant element M is 1:1, and sinter at 500°C in an oxygen-containing atmosphere to obtain the final product.

[0140] Comparative Examples 2-4

[0141] The preparation methods of the ternary single-crystal cathode materials in Comparative Examples 2-4 and Comparative Example 1 are basically the same. The amounts of nickel source, cobalt source and manganese source added are the same as those added in Examples 2-4. The specific parameters are shown in Table 3.

[0142] Comparative Example 5

[0143] The preparation method of the ternary single-crystal cathode material in this comparative example includes the following steps:

[0144] 1) Prepare a 1.5 mol / L solution A by mixing nickel sulfate, cobalt sulfate, and manganese sulfate in a molar ratio of 0.83:0.12:0.05; prepare a 5 mol / L solution B by mixing NaOH as a precipitant; and prepare a 2 mol / L solution C by mixing ammonia.

[0145] 2) Simultaneously introduce solutions A, B, and C into the reaction vessel, control the pH at 10-11, the reaction temperature at 60℃, the stirring speed at 250rpm, and the ammonia value at 7g / L. Stop when the D50 reaches 3.7μm.

[0146] 3) After the reaction, the material is washed with alkali and water to remove Na / S impurities, and then dried at 100℃ to obtain precursor particles.

[0147] 4) The obtained precursor particles are mixed with lithium hydroxide and dopant M (Al in this case) in a molar ratio of 1:1.02:0.005 and then sintered once at 800℃ in an oxygen-containing atmosphere. The sintered material is then subjected to air jet milling to obtain ternary single crystal cathode material D with a particle size of 2.3μm.

[0148] 5) The ternary single-crystal cathode material D and the active material cobalt hydroxide are mixed, wherein the molar ratio of the active material cobalt hydroxide to the dopant element M is 0.029:0.0049, and sintered at 650℃ in an oxygen-containing atmosphere to obtain product E.

[0149] 6) Mix E and coating agent Q (Mo in this case), wherein the molar ratio of coating agent Q to dopant element M is 1:1, and sinter at 500°C in an oxygen-containing atmosphere to obtain the final product.

[0150] Comparative Examples 6-8

[0151] The preparation methods of the ternary single-crystal cathode materials in Comparative Examples 6-8 and Comparative Example 5 are basically the same. The amounts of nickel source, cobalt source and manganese source added are the same as those added in Examples 2-4. The specific parameters are shown in Table 3.

[0152] Test method:

[0153] Discharge specific capacity: At 25℃ and normal pressure (0.1MPa), the ternary single-crystal cathode material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) of each embodiment and comparative example were thoroughly mixed in N-methylpyrrolidone solvent at a mass percentage ratio of 95:3:2 to obtain a cathode slurry. The cathode slurry was coated on aluminum foil, dried, and cold-pressed to obtain a cathode electrode sheet containing a cathode active layer with a thickness of 100μm. The cathode electrode sheet, lithium sheet, separator, and electrolyte were assembled into a coin cell in a coin cell box. The battery was charged at a constant current rate of 0.2C to a voltage of 4.5V, and then charged at a constant voltage of 4.5V to a current of 0.05C. The charging capacity at this time was recorded as the first charge capacity. After resting for 5 minutes, the battery was discharged at a constant current rate of 0.2C to a voltage of 2.5V. The discharge capacity at this time was recorded as the first discharge specific capacity of the battery.

[0154] Full-cycle testing: The positive electrode material was coated into a positive electrode sheet according to the method in the coin capacity test, and the negative electrode was graphite. Together with the separator polyethylene and the electrolyte (LiPF6 electrolyte, EC / DMC solvent), a full cell was formed. Under the charge and discharge rate of 1C, the cell was cycled, and the DCR of each cycle was compared with that of the first cycle to confirm the DCR growth rate. Under the condition of 45℃, the DCR growth rate was calculated after 300 cycles.

[0155] DSC test: The ternary single crystal cathode materials prepared in each embodiment and comparative example were placed in a differential scanning calorimeter and heated in a programmed manner to test the temperature at which the cathode material exhibited an exothermic peak.

[0156] High-temperature storage performance: The positive electrode material was coated into a positive electrode sheet according to the method in the coin cell capacity test to prepare a positive soft-pack battery. The soft-pack battery before storage was placed in water and the initial volume V0 of the soft-pack battery was tested by the water displacement method. The temperature was controlled at 70℃. After storage for 14 days, the volume V1 of the soft-pack battery was tested again by the water displacement method. The volume change (V1-V0) / V0 was calculated to obtain the gas generation situation during high-temperature storage.

[0157] Figure 1 This is a SEM image of the ternary cathode material precursor prepared in Example 1 of the present invention;

[0158] from Figure 1 It can be seen that the ternary cathode material precursor prepared in Example 1 of the present invention has a relatively large particle size.

[0159] Figure 2 This is a cross-sectional SEM image of the ternary cathode material precursor prepared in Example 1 of the present invention;

[0160] from Figure 2 It can be seen that the ternary cathode material precursor prepared in Example 1 of the present invention has a large porosity.

[0161] Figure 3 This is a SEM image of the second particle prepared in Example 1 of the present invention;

[0162] from Figure 3 It can be seen that the second particle prepared in Example 1 of the present invention is a large secondary sphere and can maintain an aggregated state.

[0163] Figure 4 This is a SEM image of the ternary single-crystal cathode material prepared in Example 1 of the present invention.

[0164] from Figure 4 It can be seen that the ternary single-crystal cathode material prepared in Example 1 of the present invention consists of single-crystal particles with good dispersion, which meets the requirements for single-crystal size.

[0165] Table 1

[0166]

[0167]

[0168] Table 2

[0169]

[0170] Table 3

[0171]

[0172] As can be seen from Tables 1, 2 and 3, compared with the comparative example, the ternary single-crystal cathode material prepared from the ternary cathode material precursor provided by the present invention can improve the cycle performance and storage performance of lithium-ion batteries.

[0173] The ternary single-crystal cathode materials prepared in Examples 1-4 were not coated with active materials, such as cobalt oxide or cobalt hydroxide. A comparison of Examples 1-4 with Comparative Examples 1-8 shows that the ternary single-crystal cathode materials prepared by this invention can improve the cycle performance and storage performance of lithium-ion batteries.

[0174] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A ternary cathode material precursor, characterized in that, Having the chemical composition shown in Formula 1, the precursor is composed of multiple microparticles aggregated together, and the median particle size D50 of the precursor is 6-15 μm. The porosity of the precursor is 20-40%; Ni a Co b Mn c O2, Equation 1, Wherein, 0.5 < a < 0.95, 0 < b < 0.2, 0 < c < 0.3; The specific surface area of ​​the precursor is 40-80 m². 2 / g; The median particle size D50 of the microparticles is 100-300 nm.

2. A method for preparing a ternary cathode material precursor as described in claim 1, characterized in that, Includes the following steps: 1) The system including nickel source, cobalt source and manganese source is kept in an oxygen-containing atmosphere at a temperature of 300-600℃ for 3-10 hours to obtain the first particle; 2) The first particle is subjected to a first crushing process until nanoparticles with a median particle size D50 of 100-300nm are obtained, and the nanoparticles are mixed with deionized water to form a slurry system. 3) The slurry system is spray-dried, with the feed rate controlled at 1-3 L / h, the inlet temperature at 100-180℃, and the outlet temperature at 80-120℃, to obtain the ternary cathode material precursor.

3. The method for preparing the ternary cathode material precursor according to claim 2, characterized in that, The mass ratio of the nanoparticles to deionized water is 1:9-4:

6.

4. A ternary single-crystal cathode material, characterized in that, The ternary single-crystal cathode material is prepared from the ternary cathode material precursor described in claim 1 as raw material, and has the chemical composition shown in Formula 2. The median particle size D50 of the ternary single-crystal cathode material is 1-3 μm, and the residual alkali content is 0.05-0.25%. Li x Ni d Co e Mn f M g O2 / Q, Formula 2, Wherein, M includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti, Q includes one or more of Zr, Al, Mo, Ca, Mg, Ba, B, Y, Sr, and Ti, 1 < x < 1.2, 0.5 < d < 0.95, 0 < e < 0.2, 0 < f < 0.3, 0 ≤ g < 0.06, and d + e + f + g = 1.

5. A method for preparing the ternary single-crystal cathode material according to claim 4, characterized in that, Includes the following steps: 1) The raw material system comprising the ternary cathode material precursor, lithium source and dopant element M as described in claim 1 is subjected to an oxygen-containing atmosphere at a temperature of 700-900℃ for 10-15 hours to obtain the second particle; 2) Wash the second particle with deionized water for 2-10 min, controlling the rotation speed at 100-200 r / min, and then centrifuge and dry to obtain the dried product; 3) The dried product is subjected to a second crushing process until a crushed product with a median particle size D50 of 1-3 μm is obtained; 4) The system including the crushed product and the coating material Q is kept at 250-700℃ in an oxygen-containing atmosphere for 10-15 hours to obtain a ternary single crystal cathode material.

6. The method for preparing the ternary single-crystal cathode material according to claim 5, characterized in that, The mass ratio of the second particle to deionized water is 0.6-1.2:

1.

7. A positive electrode plate, characterized in that, The positive electrode sheet includes the ternary single-crystal positive electrode material as described in claim 4 or the ternary single-crystal positive electrode material prepared by the preparation method described in claim 5 or 6.

8. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode sheet as described in claim 7.

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