Polycrystalline high-nickel ternary positive electrode material, preparation method thereof and battery
By combining multilayer coating technology and dopants, the cycle stability problem of high-nickel ternary cathode materials was solved, and the preparation of polycrystalline high-nickel ternary cathode materials with low residual alkali content, few internal cracks and high cycle stability was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- ZHEJIANG HUAYOU COBALT CO LTD
- Filing Date
- 2023-04-28
- Publication Date
- 2026-05-22
AI Technical Summary
High-nickel ternary cathode materials have poor cycle stability, mainly due to oxidation reactions caused by high Ni content, high residual alkali content, and large anisotropic changes in crystal volume. Existing coating methods have problems such as unevenness or high cost.
A multi-layer coating technology is adopted, in which a dopant is mixed with a high-nickel ternary precursor and a lithium source for a first sintering, followed by a second coating and a third coating agent for a second sintering, forming a coating layer without dead corners. The third coating agent, which melts at low temperature, is combined to improve the cycling stability of the material.
The material's residual alkali content was reduced, internal cracks were decreased, cycle stability and electrochemical performance were improved, and the structural stability of the material during charge and discharge processes was ensured.
Smart Images
Figure CN116454242B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery technology, and more specifically, to a polycrystalline high-nickel ternary cathode material, its preparation method, and a battery thereof. Background Technology
[0002] High-nickel ternary cathode materials with polycrystalline structures are the main development direction for cathode materials used in lithium-ion batteries due to their ultra-high discharge specific capacity, suitable rate performance, high operating voltage, and low cobalt content. However, high-nickel ternary cathode materials have poor cycle stability. Generally, the higher the Ni content, the worse the cycle stability and the faster the capacity decay.
[0003] The reason may be as follows:
[0004] ① The higher the Ni content, the more Ni will be released when fully charged. 2+ and Ni 3+ It is oxidized into Ni, which has extremely strong oxidizing properties. 4+ Moreover, Ni 4+ The -O bond is also relatively weak, making it very easy to react with the electrolyte to form inactive rock salt structure NiO crystals and release oxygen or other gases.
[0005] ② Because Ni is alkaline, the higher the Ni content and the lower the sintering temperature, the higher the residual alkali content on the surface. The main components of residual alkali are a mixture of lithium hydroxide and lithium carbonate, which is highly hygroscopic. Moisture is the biggest enemy of lithium-ion batteries, not only causing manufacturing difficulties but also resulting in poor cell cycle stability and easy gas expansion. This is because high moisture content causes the electrolyte to produce a large amount of highly corrosive HF acid, which will continuously damage the surface and even the internal structure of the ternary cathode material.
[0006] ③ As the Ni content increases, the difference between the lattice constants a(b) and c during charging becomes greater, leading to a greater change in crystal volume anisotropy. This generates enormous internal stress, causing through-cracks to form in the cathode material. Ultra-high nickel ternary cathode materials exhibit numerous through-cracks even in the first fully charged state. Electrolyte is injected through these cracks and undergoes continuous side reactions with the interior, forming NiO with an electrochemically inactive rock-salt crystal structure, resulting in rapid material failure.
[0007] Currently, in order to obtain high-nickel ternary cathode materials with better cycle stability, it is usually necessary to modify them, such as by coating.
[0008] Existing coating methods are mainly divided into solid-state sintering coating, aqueous solution coating, and organic solvent coating.
[0009] Among them, solid-phase sintering coating mainly uses a one-time sintering method, coating one or more coating reagents. The coating layer is prone to cracking and uneven coating.
[0010] Although the aqueous solution coating method results in a more uniform coating, the ternary cathode material cannot be in contact with the aqueous solution for a long time, otherwise the structure will be damaged.
[0011] Organic solvent coating methods are costly, dangerous, and environmentally unfriendly, hindering their commercialization.
[0012] In view of this, the present invention is proposed. Summary of the Invention
[0013] One of the objectives of this invention is to provide a polycrystalline high-nickel ternary cathode material with low residual alkali content and strong cycle stability.
[0014] The second objective of this invention is to provide a method for preparing the above-mentioned polycrystalline high-nickel ternary cathode material.
[0015] The third objective of this invention is to provide a battery in which the cathode material is the aforementioned polycrystalline high-nickel ternary cathode material.
[0016] This application can be implemented as follows:
[0017] In a first aspect, this application provides a polycrystalline high-nickel ternary cathode material, which includes secondary particles formed by the stacking of single-crystal primary particles, wherein the single-crystal primary particles are in contact with each other and form grain boundaries.
[0018] The lattice of the single-crystal primary particle is doped with a dopant, and the surface of the secondary particle and the grain boundary of the single-crystal primary particle are both covered with a first coating layer formed by a first coating agent; and the surface of the first coating layer is covered with a second coating layer formed by a third coating agent without dead corners, and the second coating layer corresponding to the surface of the secondary particle is covered with a framework formed by the second coating agent.
[0019] The second coating agent is a material that does not melt during the secondary sintering process, while the third coating agent is a material that melts during the secondary sintering process.
[0020] In an optional embodiment, the polycrystalline high-nickel ternary cathode material has at least one of the following characteristics:
[0021] Feature 1: The chemical formula of the high-nickel ternary precursor is Ni x Co y Mn z (OH)2, x+y+z=1, 0.8≤x<1, 0<y+z≤0.2;
[0022] Feature 2: The lithium source includes lithium hydroxide monohydrate;
[0023] Feature 3: The doping element of the dopant includes at least one of Al, Mg and Ti;
[0024] Feature 4: The first coating agent includes at least one of ZrO2, SeO2, Sb2O5, Sb2O3, Nb2O5, MoO3, TiO2, WO3, Ta2O5 and MgO.
[0025] In an optional embodiment, the dopant includes an aluminum compound; more preferably, the dopant includes at least one of Al2O3 and Al(OH)3.
[0026] In an optional embodiment, the polycrystalline high-nickel ternary cathode material also has at least one of the following characteristics:
[0027] Feature 5: The molar ratio of high-nickel ternary precursor to lithium source is 1:1 to 1:1.1;
[0028] Feature 6: The molar ratio of dopant to ternary precursor is 0.001:0.999-0.01:0.99;
[0029] Feature 7: The molar ratio of the first coating agent to the high-nickel ternary precursor is 0.0005:1-0.01:1.
[0030] In an optional embodiment, the polycrystalline high-nickel ternary cathode material also has at least one of the following characteristics:
[0031] Feature 8: The second coating agent includes at least one of Al2O3, ZrO2, Nb2O5, and TiO2;
[0032] Feature 9: The third coating agent includes at least one of H3BO3, Sb2O3, SeO2 and NH4H2PO4.
[0033] In an optional embodiment, the total molar amount of the second and third coating agents is in the molar ratio of the ternary cathode material to the ternary cathode material of 0.0005:1-0.01:1.
[0034] In an optional embodiment, the molar ratio of the second coating agent to the third coating agent is 1:2 to 2:1.
[0035] Secondly, this application provides a method for preparing a polycrystalline high-nickel ternary cathode material as described in any of the foregoing embodiments, comprising the following steps: sintering a mixture of a high-nickel ternary precursor, a lithium source, a dopant, and a first coating agent in a first sintering, followed by secondary coating and secondary sintering with a second coating agent and a third coating agent.
[0036] In an optional implementation, the sintered material is further crushed after each sintering.
[0037] In an optional embodiment, the sintering temperature is 680-820°C.
[0038] In an optional embodiment, the sintering process for a single sintering includes: first heating to 300-600℃ and holding for 0.1-3 hours, then heating to 680-820℃ and holding for 10-20 hours.
[0039] In an optional implementation, the heating rate corresponding to one sintering is 1-3℃ / min.
[0040] In an alternative implementation, the first sintering is carried out in an oxygen atmosphere.
[0041] In an optional implementation, the oxygen purity is ≥92%.
[0042] In an optional embodiment, the secondary coating includes mixing a sintered material obtained from a primary sintering process with a second coating agent and a third coating agent.
[0043] In an optional embodiment, the secondary sintering temperature is 250-600°C, and / or the secondary sintering time is 0.5-16 h.
[0044] In an optional implementation, the heating rate corresponding to the secondary sintering is 1-5℃ / min.
[0045] In an alternative embodiment, the secondary sintering is carried out in an oxygen atmosphere.
[0046] In an optional implementation, the oxygen purity is ≥92%.
[0047] Thirdly, this application provides a battery whose positive electrode material includes the polycrystalline high-nickel ternary positive electrode material of any of the aforementioned embodiments.
[0048] The beneficial effects of this application include:
[0049] This application creatively employs special configurations for doping and coating during the sintering process. For example, by simultaneously mixing the first coating agent and the dopant with the high-nickel ternary precursor and the lithium source, a synergistic effect of coating with the first coating agent and doping with the dopant is achieved. The dopant stabilizes the crystal structure, preventing the formation of penetrating cracks in the cathode material and reducing the likelihood of NiO formation. Through multi-layer coating, the innermost coating layer is reinforced, improving electrochemical performance. Furthermore, the third coating agent used in the secondary coating process can melt at low temperatures, achieving a coating effect without dead zones. Correspondingly, the second coating agent acts as a framework, which is beneficial for improving the cycle stability of the material.
[0050] The resulting polycrystalline high-nickel ternary cathode material has low residual alkali, high cycle stability, and few internal cracks during charging, with virtually no through cracks from the surface to the interior. Attached Figure Description
[0051] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0052] Figure 1 SEM image of the ternary cathode material prepared in Example 1;
[0053] Figure 2 The graph shows the performance test results of the button cell provided in Example 1;
[0054] Figure 3 This is an internal structure diagram of the corresponding cathode material after performance testing in Example 1;
[0055] Figure 4 SEM image of the ternary cathode material prepared in Example 2;
[0056] Figure 5 This is a graph showing the performance test results of the button cell provided in Example 2;
[0057] Figure 6 This is an internal structure diagram of the corresponding cathode material after performance testing in Example 2;
[0058] Figure 7 SEM image of the ternary cathode material prepared in Example 3;
[0059] Figure 8 The graph shows the performance test results of the button cell provided in Example 3;
[0060] Figure 9 Scanning electron microscope image of a section of the ternary cathode material prepared in Example 4 after 50 cycles;
[0061] Figure 10 The graph shows the performance test results of the button cell provided in Example 4;
[0062] Figure 11 The graph shows the performance test results of the button cell provided in Example 5;
[0063] Figure 12 The graph shows the performance test results of the button cell provided in Example 6;
[0064] Figure 13 This is a graph showing the performance test results of the button cell provided in Example 7;
[0065] Figure 14 SEM image of the ternary cathode material prepared in Example 8;
[0066] Figure 15 SEM image of the ternary cathode material prepared in Example 9;
[0067] Figure 16 SEM image of the ternary cathode material prepared in Comparative Example 1;
[0068] Figure 17 The graph shows the performance test results of the button cell provided for Comparative Example 1.
[0069] Figure 18 This is an internal structure diagram of the corresponding cathode material after performance testing in Comparative Example 1;
[0070] Figure 19 The graph shows the performance test results of the button cell provided for Comparative Example 2.
[0071] Figure 20 The graph shows the performance test results of the button cell provided for Comparative Example 3.
[0072] Figure 21 The graph shows the performance test results of the button cell provided for Comparative Example 4.
[0073] Figure 22 The graph shows the performance test results of the button cell provided for Comparative Example 5.
[0074] Figure 23 The graph shows the performance test results of the button cell provided for Comparative Example 6.
[0075] Figure 24 The graph shows the performance test results of the button cell provided for Comparative Example 7.
[0076] Figure 25 The graph shows the performance test results of the button cell provided for Comparative Example 8. Detailed Implementation
[0077] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.
[0078] The following provides a detailed description of the polycrystalline high-nickel ternary cathode material, its preparation method, and the battery provided in this application.
[0079] This application proposes a polycrystalline high-nickel ternary cathode material, which is obtained by first sintering a mixture of high-nickel ternary precursor, lithium source, dopant and first coating agent, and then mixing it with second coating agent and third coating agent for secondary coating and secondary sintering.
[0080] The second coating agent is a material that does not melt during the secondary sintering process, while the third coating agent is a material that melts during the secondary sintering process.
[0081] It should be noted that the inventors pointed out that the coating agent used in solid-state sintering coating is usually an oxide that does not melt, which makes it difficult to achieve a complete coverage and also makes it difficult to penetrate into the internal grain boundaries of the polycrystalline ternary cathode material, making it difficult to control precisely.
[0082] This application creatively employs a special configuration for doping and coating during the sintering process. For example, by simultaneously mixing the first coating agent and the dopant with the high-nickel ternary precursor and the lithium source, a synergistic effect of coating with the first coating agent and doping with the dopant is achieved. On one hand, the Al in the dopant... 3+ Mg 2+ Ti 4+ It can penetrate the TM layer (transition metal layer), which plays a role in stabilizing the crystal structure, avoiding the formation of penetrating cracks in the cathode material, and reducing the possibility of NiO formation. On the other hand, the solid-state sintering method can reduce surface residual alkali. Furthermore, through multi-layer coating, the innermost coating layer can be reinforced, improving electrochemical performance. In addition, the third coating agent used in the secondary coating process can melt at low temperature, achieving a coating effect without dead corners. Correspondingly, the second coating agent can act as a skeleton, which is beneficial to improving the cycle stability of the material.
[0083] The polycrystalline high-nickel ternary cathode material obtained above includes secondary particles formed by the stacking of single-crystal primary particles, with the single-crystal primary particles contacting each other and forming grain boundaries.
[0084] The lattice of the single-crystal primary particle is doped with a dopant, and the surface of the secondary particle and the grain boundary of the single-crystal primary particle are both covered with a first coating layer formed by a first coating agent; and the surface of the first coating layer is covered with a second coating layer formed by a third coating agent without dead corners, and the second coating layer corresponding to the surface of the secondary particle is covered with a framework formed by the second coating agent.
[0085] In this application, the chemical formula of the high-nickel ternary precursor is Ni x Co y Mn z (OH)2, x+y+z=1, 0.8≤x<1, 0<y+z≤0.2.
[0086] In some specific embodiments, the aforementioned high-nickel ternary precursor is mainly a 9-series ternary precursor, for example, the chemical formula of the high-nickel ternary precursor can be Ni. 0.90 Co 0.06 Mn 0.04 (OH)2.
[0087] In other specific embodiments, x in the above-mentioned high-nickel ternary precursor chemical formula can take the value of 0.8, 0.85, 0.9, 0.92, 0.94, 0.96, 0.98, or any other value in the range of 0.8-1.
[0088] Similarly, the values of y and z can be any values as long as their sum is in the range of 0-0.2. The specific values of y and z will not be listed here.
[0089] In this application, the lithium source is lithium hydroxide monohydrate.
[0090] The dopant element includes at least one of Al, Mg, and Ti. When aluminum is included as the dopant element, it can be provided, for example, in the form of an aluminum compound, which may specifically include at least one of Al₂O₃ and Al(OH)₃. The same applies to other elements.
[0091] It should be noted that the ionic radius of the dopant element in its trivalent state used in this application is similar to that of Ni. 3+ The ionic radii of the two molecules are not significantly different (e.g., Al). 3+ The ionic radius is 0.0535 nm, Ni 3+ With an ionic radius of 0.056 nm, the aforementioned dopants can penetrate the TM layer relatively well; while commonly used dopants such as Zr and / or Ta have ionic radii in their normal valence states similar to those of Ni. 3+ The ionic radii differ significantly, making it difficult to dope into the TM layer.
[0092] In this application, the first coating agent may include at least one of ZrO2, SeO2, Sb2O5, Sb2O3, Nb2O5, MoO3, TiO2, WO3, Ta2O5 and MgO to improve the cycling stability of the material.
[0093] For reference, the molar ratio of the high-nickel ternary precursor to the lithium source can be 1:1 to 1:1.1, such as 1:1, 1:1.02, 1:1.05, 1:1.08 or 1:1.1, or any other value in the range of 1:1 to 1:1.1.
[0094] The molar ratio of dopant to ternary precursor can be 0.001:0.999-0.01:0.99, 0.001:0.999, 0.002:0.998, 0.005:0.995, 0.008:0.992, or 0.01:0.99, or any other value within the range of 0.001:0.999-0.01:0.99.
[0095] It should be noted that if the amount of dopant is too small, it will not be conducive to reducing the Li / Ni mixing degree and enhancing the TM-O bond, suppressing oxygen evolution under long cycles and high temperatures, and thus the effect of improving cycle stability will be extremely limited; if the amount of dopant is too large, the discharge capacity will be reduced due to the excessive content of inactive substances.
[0096] The molar ratio of the first coating agent to the high-nickel ternary precursor can be 0.0005:1-0.01:1, such as 0.0005:1, 0.0008:1, 0.001:1, 0.002:1, 0.005:1, 0.008:1 or 0.01:1, or any other value within the range of 0.0005:1-0.01:1.
[0097] It should be noted that if the amount of the first coating agent is too small, it cannot effectively prevent the electrolyte from contacting the internal active material, and the coating layer has low mechanical strength and is prone to peeling off. If the amount of the first coating agent is too large, the high content of inactive material will reduce the discharge capacity, and the excessively thick coating layer will lead to excessively high internal resistance, seriously affecting the Li-E ratio of the material. + The shuttle movement reduces the material's performance.
[0098] In this application, the coating adopts a multi-layer coating method. Specifically, the number of coating layers can be 2, 3 or more, and can be set accordingly as needed.
[0099] In some embodiments, the number of coating layers is two, and the coating agent used for the secondary coating includes a second coating agent and a third coating agent. The second coating agent may include, for example, at least one of Al2O3, ZrO2, Nb2O5, and TiO2, and the third coating agent may include, for example, at least one of H3BO3, Sb2O3, SeO2, and NH4H2PO4.
[0100] The second coating agent does not melt during the secondary sintering process, thus serving as a framework; the third coating agent melts during the secondary sintering process, thus achieving coating without dead angles and further improving the coating effect.
[0101] Preferably, the molar ratio of the total molar amount of the second and third coating agents to the ternary cathode material can be 0.0005:1 to 0.01:1, such as 0.0005:1, 0.0008:1, 0.001:1, 0.002:1, 0.005:1, 0.008:1 or 0.01:1, or any other value within the range of 0.0005:1 to 0.01:1.
[0102] For reference, the molar ratio of the second coating agent to the third coating agent can be 1:2 to 2:1, such as 1:2, 1.5:1.5, or 2:1, or any other value within the range of 1:2 to 2:1. By using the second and third coating agents in the above proportions during the secondary sintering process, the third coating agent can melt under the low-temperature conditions of the secondary sintering provided in this application to form a seamless coating on the surface of all the first coating layers, while the second coating agent cannot melt under the low-temperature conditions of the secondary sintering provided in this application and does not have time to diffuse to the corresponding positions of the grain boundaries. It can only exist as a skeleton in the second coating layer corresponding to the surface of the secondary particles.
[0103] If the amount of the second coating agent used in the secondary coating process is too small, it cannot effectively support the overall mechanical properties of the coating layer, cannot effectively enhance the strength of the composite coating layer and hinder electrolyte penetration, and cannot effectively fill the dead corners of the first coating layer. If there is a third coating layer, it cannot effectively act as a bridge to connect the first and third coating layers. If the amount of the second coating agent is too large, the high content of inactive substances will reduce the discharge capacity, and if the coating layer is too thick, it will lead to excessively high internal resistance, seriously affecting the Li- of the material. + The movement of materials can affect their performance.
[0104] In some preferred embodiments, the molar ratio of the second coating agent to the third coating agent is 0.8:1 to 1.5:1. Coating with this dosage method yields better coating results.
[0105] As mentioned above, the polycrystalline high-nickel ternary cathode material provided in this application has fewer internal cracks, basically no through cracks from the surface to the interior, low residual alkali, and high cycle stability.
[0106] Accordingly, this application also provides a method for preparing the above-mentioned polycrystalline high-nickel ternary cathode material, which may include the following steps: sintering a mixture of high-nickel ternary precursor, lithium source, dopant and first coating agent in one step, followed by secondary coating and secondary sintering with second and third coating agents.
[0107] For reference, the high-nickel ternary precursor, lithium source, dopant, and first coating agent can be mixed by high-speed mixing, ball milling, or 360° rotary mixing. Similarly, the first sintered material can also be mixed with the second and third coating agents by high-speed mixing, ball milling, or 360° rotary mixing.
[0108] In this application, the sintering temperature can be 680-820℃, such as 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 810℃ or 820℃, or any other value within the range of 680-820℃.
[0109] If the primary sintering temperature is below 680℃, it is not conducive to the lithiation of the ternary precursor and the development of the layered crystal structure. The crystal structure contains many defects, and the primary particles are also very small, resulting in low capacity, high side reactions with the electrolyte, and poor cycle stability. If the temperature is above 820℃, it is easy to cause Ni 2+ The formation of large amounts of Li / Ni mixtures or the formation of inactive NiO not only reduces capacity but also increases internal resistance, reduces initial efficiency, and affects the cycle stability of subsequent cells.
[0110] For reference, the sintering regime for a single sintering process may include: first heating to 400-600℃ (e.g., 400℃, 420℃, 450℃, 470℃, 490℃, 500℃, 510℃, 520℃, 530℃, 540℃, 550℃, 560℃, 570℃, 580℃, 590℃, or 600℃, etc.) and holding at that temperature for 0.1-3 hours (e.g., 0.1 hours, 0.5 hours, 0.8 hours, 1 hour, 1 minute). 0.5h, 2h, 2.5h or 3h, etc.), then raise the temperature to 680-820℃ (such as 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 810℃ or 820℃, etc.) and keep it at that temperature for 10-20h (such as 10h, 12h, 15h, 18h or 20h, etc.).
[0111] In the above sintering process, the temperature is first raised to 400-600℃ and held for 0.1-3 hours, which can play a role in pre-lithiation and removal of water of crystallization.
[0112] The heating rate corresponding to the first sintering can be 1-3℃ / min, such as 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min or 3℃ / min, or any other value within the range of 1-3℃ / min.
[0113] If the heating rate is too slow, production efficiency will be greatly reduced; if the heating rate is too fast, the reaction will be too violent, and the polycrystalline ternary cathode will easily crack.
[0114] The aforementioned sintering can be carried out in an oxygen atmosphere, for example, the oxygen purity can be ≥92%.
[0115] The above-mentioned primary sintering can be carried out in a tube furnace, box furnace or roller kiln, and the secondary sintering described below is similar.
[0116] In this application, secondary coating may include: mixing a sintered material obtained from a primary sintering process with a second coating agent and a third coating agent.
[0117] Furthermore, the secondary sintering temperature can be 250-600℃, such as 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃ or 600℃, or any other value within the range of 250-600℃.
[0118] The secondary sintering time can be 0.5-16h, such as 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 5h, 8h, 10h, 12h, 15h or 16h, or any other value within the range of 0.5-16h.
[0119] If the secondary sintering temperature is below 250℃ or the time is less than 0.5h, the coating layer will not bond tightly with the interior, or no chemical reaction will occur at all; if the secondary sintering temperature is above 600℃ or the time is longer than 16h, there will be adverse factors such as the coating material volatilizing, the reaction being too violent, and the cost being too high.
[0120] The heating rate corresponding to the above-mentioned secondary sintering can be 1-5℃ / min, such as 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min or 5℃ / min, or any other value within the range of 1-5℃ / min.
[0121] Similarly, the above-mentioned secondary sintering can be carried out in an oxygen atmosphere, with the oxygen purity being ≥92% for example.
[0122] Preferably, after each sintering, the sintered material is crushed, and the refined sintered material can be further sieved.
[0123] As mentioned above, this application uses a solid-state melting method to achieve multi-layer uniform coating, which also incorporates elemental doping. It does not involve water washing, which not only reduces the residual alkali content of polycrystalline high-nickel ternary cathode materials, but also significantly improves their cycle stability.
[0124] Accordingly, this application also provides a battery whose positive electrode material includes the above-mentioned polycrystalline high-nickel ternary positive electrode material.
[0125] For reference, a battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode includes the aforementioned polycrystalline high-nickel ternary positive electrode material. For information on the negative electrode, separator, and electrolyte, please refer to relevant conventional technologies; further details will not be provided here.
[0126] The features and performance of the present invention will be further described in detail below with reference to embodiments.
[0127] Example 1
[0128] This embodiment provides a polycrystalline high-nickel ternary cathode material, which is prepared by the following method:
[0129] S1: Weigh out a certain amount of Ni 0.90 Co 0.06 Mn 0.04 The high-nickel ternary precursor (OH)2, lithium source (lithium hydroxide monohydrate fine powder), dopant Al(OH)3, and first coating agent ZrO2 are mixed evenly using a high-speed rotary mixer.
[0130] The molar ratio of the high-nickel ternary precursor to lithium hydroxide monohydrate is 1:1.01, the molar ratio of the high-nickel ternary precursor to Al(OH)3 is 0.997:0.003, and the molar ratio of the high-nickel ternary precursor to the first coating agent ZrO2 is 0.997:0.001.
[0131] S2: The mixture obtained in S1 is placed in an atmosphere tube furnace for primary sintering.
[0132] Specifically, the temperature is first increased to 500℃ at a rate of 2℃ / min and held for 30 minutes; then increased to 740℃ at the same rate and held for 1 hour; then decreased to 735℃ and held for 5 hours; then decreased to 730℃ and held for 5 hours.
[0133] During the sintering process, the oxygen flow rate is maintained at 300 sccm, and the oxygen purity is ≥92%.
[0134] S3: After the sample cools naturally, it is crushed and sieved to obtain a burnt material.
[0135] S4: Add a certain amount of the second coating agent nano Al2O3 powder and the third coating agent H3BO3 to the above-mentioned calcined material, and mix them evenly with a high-speed rotating mixer.
[0136] The molar ratio of H3BO3 to the cathode material is 0.002:1, and the molar ratio of nano-Al2O3 powder to the cathode material is 0.001:1.
[0137] S5: The mixed material obtained in S4 is placed in an atmosphere tube furnace for secondary sintering. The secondary sintering temperature is 500℃, the holding time is 240min, and the heating rate is 2℃ / min.
[0138] During the sintering process, the oxygen flow rate is maintained at 300 sccm, and the oxygen purity is ≥92%.
[0139] S6: After the sample is naturally cooled, it is crushed and sieved to obtain a polycrystalline high-nickel ternary cathode material with a particle size of 13μm.
[0140] Figure 1 This is a scanning electron microscope (SEM) image of the ternary cathode material prepared in Example 1. As can be seen from the image, the surface of the obtained ternary cathode material has obvious coatings.
[0141] Figure 2 The coin cell assembled with the ternary cathode material prepared in Example 1 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It was charged with a constant current and constant voltage of 0.5C, and the charging cut-off current was 0.005C. It was discharged with a constant current of 0.5C, and the highest discharge specific capacity reached 218.1mAh / g. After 50 cycles, the capacity retention rate was 96.5%.
[0142] Figure 3 for Figure 2 After 50 cycles of the coin cell, the cell was first returned to a discharged state, then the coin cell was disassembled, the positive electrode was removed, and the electrolyte residue was removed by rinsing with propylene carbonate solvent. The electrode surface was then ion-polished using a focused ion beam mill to obtain the internal structure of the positive electrode material. Scanning electron microscopy revealed few internal cracks in the positive electrode material, with virtually no through-cracks from the surface to the interior. The pH value of the residual alkali in the tested material was 11.8 (25℃).
[0143] The pH test method is as follows: Weigh 5.0 grams of test material powder, disperse it in 50 grams of deionized water, keep the water temperature at 25℃, stir for 10 minutes to obtain a clear liquid, test the clear liquid with a pH meter and read the pH value, the same below.
[0144] Example 2
[0145] This embodiment provides a polycrystalline high-nickel ternary cathode material, which is prepared by the following method:
[0146] S1: Weigh out a certain amount of Ni 0.90 Co 0.06 Mn0.04 The high-nickel ternary precursor (OH)2, lithium source (lithium hydroxide monohydrate fine powder), dopant Al(OH)3, and first coating agent ZrO2 are mixed evenly using a high-speed rotary mixer.
[0147] The molar ratio of the high-nickel ternary precursor to lithium hydroxide monohydrate is 1:1.01, the molar ratio of the high-nickel ternary precursor to Al(OH)3 is 0.998:0.002, and the molar ratio of the high-nickel ternary precursor to the first coating agent ZrO2 is 0.998:0.001.
[0148] S2: The mixture obtained in S1 is placed in an atmosphere tube furnace for primary sintering.
[0149] Specifically, the temperature is first increased to 500℃ at a rate of 2℃ / min and held for 30 minutes; then increased to 740℃ at the same rate and held for 1 hour; then decreased to 735℃ and held for 5 hours; then decreased to 730℃ and held for 5 hours.
[0150] During the sintering process, the oxygen flow rate is maintained at 300 sccm, and the oxygen purity is ≥92%.
[0151] S3: After the sample cools naturally, it is crushed and sieved to obtain a burnt material.
[0152] S4: Add a certain amount of the second coating agent nano Nb2O5 powder and the third coating agent SeO2 to the above-mentioned calcined material, and mix them evenly with a high-speed rotating mixer.
[0153] The molar ratio of SeO2 to the cathode material is 0.001:1, and the molar ratio of nano-Nb2O5 powder to the cathode material is 0.002:1.
[0154] S5: The mixed material obtained in S4 is placed in an atmosphere tube furnace for secondary sintering. The secondary sintering temperature is 600℃, the holding time is 240min, and the heating rate is 2℃ / min.
[0155] During the sintering process, the oxygen flow rate is maintained at 300 sccm, and the oxygen purity is ≥92%.
[0156] S6: After the sample is naturally cooled, it is crushed and sieved to obtain a polycrystalline high-nickel ternary cathode material with a particle size of 13μm.
[0157] Figure 4 This is a scanning electron microscope (SEM) image of the ternary cathode material prepared in Example 2. As can be seen from the image, the surface of the obtained ternary cathode material has obvious coatings.
[0158] Figure 5The coin cell assembled with the ternary cathode material prepared in Example 2 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It was charged with a constant current and constant voltage of 0.5C, and the charging cut-off current was 0.005C. It was discharged with a constant current of 0.5C, and the highest discharge specific capacity reached 221.2mAh / g. After 50 cycles, the capacity retention rate was 97.4%.
[0159] Figure 6 for Figure 5 After 50 cycles of the coin cell, the cell was first returned to a discharged state, then the coin cell was disassembled, the positive electrode was removed, and the electrolyte residue was removed by rinsing with propylene carbonate solvent. The electrode surface was then subjected to ion polishing using a focused ion beam apparatus to obtain the internal structure of the positive electrode material. Scanning electron microscopy revealed that the positive electrode material had few internal cracks and virtually no through-cracks from the surface to the interior. The pH value of the residual alkali in the tested material was 11.9 (25℃).
[0160] Example 3
[0161] This embodiment provides a polycrystalline high-nickel ternary cathode material, which is prepared by the following method:
[0162] S1: Weigh out a certain amount of Ni 0.90 Co 0.06 Mn 0.04 The high-nickel ternary precursor (OH)2, lithium source (fine lithium hydroxide monohydrate), dopant Al2O3, and first coating agent (Nb2O5 and MgO in a 1:1 ratio) are mixed uniformly using a high-speed rotary mixer.
[0163] The molar ratio of the high-nickel ternary precursor to lithium hydroxide monohydrate is 1:1.005, the molar ratio of the high-nickel ternary precursor to Al2O3 is 0.997:0.0015, and the molar ratio of the high-nickel ternary precursor to the first coating agent (Nb2O5 and MgO) is 0.997:0.001.
[0164] S2: The mixture obtained in S1 is placed in an atmosphere tube furnace for primary sintering.
[0165] Specifically, the temperature is first increased to 500℃ at a rate of 2℃ / min and held for 30 minutes; then increased to 740℃ at the same rate and held for 1 hour; then decreased to 735℃ and held for 5 hours; then decreased to 730℃ and held for 5 hours.
[0166] During the sintering process, the oxygen flow rate is maintained at 300 sccm, and the oxygen purity is ≥92%.
[0167] S3: After the sample cools naturally, it is crushed and sieved to obtain a burnt material.
[0168] S4: Add a certain amount of the second coating agent nano ZrO2 powder and the third coating agent NH4H2PO4 to the above-mentioned calcined material, and mix them evenly with a high-speed rotating mixer.
[0169] The molar ratio of NH4H2PO4 to the cathode material is 0.001:1, and the molar ratio of nano ZrO2 powder to the cathode material is 0.002:1.
[0170] S5: The mixed material obtained in S4 is placed in an atmosphere tube furnace for secondary sintering. The secondary sintering temperature is 500℃, the holding time is 240min, and the heating rate is 2℃ / min.
[0171] During the sintering process, the oxygen flow rate is maintained at 300 sccm, and the oxygen purity is ≥92%.
[0172] S6: After the sample is naturally cooled, it is crushed and sieved to obtain polycrystalline high-nickel ternary cathode material.
[0173] Figure 7 This is a scanning electron microscope (SEM) image of the ternary cathode material prepared in Example 3. As can be seen from the image, the surface of the obtained ternary cathode material has obvious coatings.
[0174] Figure 8 The coin cell assembled from the ternary cathode material prepared in Example 3 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current and constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity reached 218.2 mAh / g, and the capacity retention rate after 50 cycles was 97.5%. The pH value of the residual alkali in the tested material was 11.8 (25°C).
[0175] Example 4
[0176] The difference between this embodiment and Embodiment 1 is that:
[0177] In S1, the dopant is Al2O3, the molar ratio of high-nickel ternary precursor to lithium hydroxide monohydrate is 1:1.005, and the molar ratio of high-nickel ternary precursor to Al2O3 is 0.997:0.0015.
[0178] In S4, the second coating agent is nano ZrO2 powder, the third coating agent is NH4H2PO4, the molar ratio of NH4H2PO4 to the cathode material is 0.001:1, and the molar ratio of nano ZrO2 powder to the cathode material is 0.002:1.
[0179] Figure 9This is a scanning electron microscope (SEM) image of a slice of the ternary cathode material prepared in Example 4 after 50 cycles. As can be seen from the image, there are fewer cracks after long cycling, and no through cracks. Figure 10 The coin cell assembled from the ternary cathode material prepared in Example 4 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current / constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity reached 224.7 mAh / g, with a capacity retention rate of 97.3% after 50 cycles and 95.7% after 60 cycles. The pH value of the residual alkali in the tested material was 11.8 (25°C).
[0180] Example 5
[0181] The difference between this embodiment and Embodiment 3 is that the second coating agent is nano-TiO2 powder, and the third coating agent is Sb2O3.
[0182] Figure 11 The coin cell assembled from the ternary cathode material prepared in Example 5 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current / constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity reached 220.3 mAh / g, with a capacity retention rate of 98.9% after 50 cycles and 97.7% after 60 cycles, demonstrating good cycle retention. The pH value of the residual alkali in the tested material was 11.9 (25°C).
[0183] Example 6
[0184] The difference between this embodiment and embodiment 3 is that in S2, the first sintering process is as follows: first, the temperature is raised to 500°C at a heating rate of 2°C / min and held for 30 minutes; then, the temperature is raised to 750°C at the same heating rate and held for 11 hours.
[0185] Figure 12 The coin cell assembled from the ternary cathode material prepared in Example 6 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current / constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity reached 222.2 mAh / g, with a capacity retention of 95.9% after 50 cycles and 95.1% after 60 cycles. The pH value of the residual alkali in the tested material was 11.7 (25°C).
[0186] Example 7
[0187] The difference between this embodiment and embodiment 3 is that in S5, the temperature of the secondary sintering is 300℃ and the holding time is 480min.
[0188] Figure 13 The coin cell assembled with the ternary cathode material prepared in Example 7 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It was charged at 0.5C constant current and constant voltage with a charging cutoff current of 0.005C and discharged at 0.5C constant current. The highest discharge specific capacity reached 221.8mAh / g. The capacity retention rate was 98.0% after 50 cycles and 96.3% after 60 cycles. The pH value of the residual alkali in the test material was 11.8 (25°C).
[0189] Example 8
[0190] The difference between this embodiment and Embodiment 1 is that the dopant is MgO.
[0191] Figure 14 The coin cell assembled with the ternary cathode material prepared in Example 8 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It was charged with a constant current and constant voltage at 0.5C, and the charging cut-off current was 0.005C. It was discharged with a constant current at 0.5C, and the highest discharge specific capacity reached 223.5mAh / g. After 50 cycles, the capacity retention rate was 95.0%, and the pH value of the residual alkali in the test material was 11.8 (25°C).
[0192] Example 9
[0193] The difference between this embodiment and Embodiment 1 is that the dopant is TiO2.
[0194] Figure 15 The coin cell assembled with the ternary cathode material prepared in Example 9 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It was charged at 0.5C constant current and constant voltage with a charging cutoff current of 0.005C and discharged at 0.5C constant current. The highest discharge specific capacity reached 220.5mAh / g, and the capacity retention rate was 98.4% after 50 cycles. The pH value of the residual alkali in the tested material was 11.8 (25°C).
[0195] Comparative Example 1
[0196] The difference between this comparative example and Example 1 is that steps S4 to S6 were not performed after S3. That is, the ternary cathode material in this comparative example is the same as the sintered material obtained in S3 of Example 1.
[0197] Figure 16 The image shows a scanning electron microscope (SEM) image of the material prepared for Comparative Example 1. No obvious coating is visible in the image.
[0198] Figure 17The coin cell assembled from the material prepared for Comparative Example 1 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It was charged at 0.5C constant current and constant voltage with a charging cutoff current of 0.005C and discharged at 0.5C constant current. The highest discharge specific capacity reached 223.2mAh / g, but the capacity retention rate after 50 cycles was only 89.6%, indicating poor performance.
[0199] Figure 18 for Figure 17 After 50 cycles of the coin cell, the cell was first returned to a discharged state, then the coin cell was disassembled, the positive electrode was removed, and the electrolyte residue was removed by rinsing with propylene carbonate solvent. The electrode surface was then subjected to ion polishing using a focused ion beam apparatus to obtain the internal structure of the positive electrode material. Scanning electron microscopy revealed numerous internal cracks, including a large number of through-cracks extending from the surface to the interior. The pH value of the residual alkali in the material was 12.2 (25℃).
[0200] Comparative Example 2
[0201] The difference between this comparative example and Example 1 is that the first coating agent was not used in S1. That is, the ternary cathode material in this comparative example has only a single coating layer.
[0202] Figure 19 The coin cell assembled from the ternary cathode material prepared for Comparative Example 2 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current / constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity reached 222.0 mAh / g, and the capacity retention rate after 50 cycles was 93.0%. The pH value of the residual alkali in the tested material was 12.0 (25°C).
[0203] Comparative Example 3
[0204] The difference between this comparative example and Example 3 is that the dopant in S1 is ZrO2.
[0205] Figure 20 The coin cell assembled from the ternary cathode material prepared for Comparative Example 3 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current / constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity was 222.5 mAh / g, and the capacity retention rate after 50 cycles was 89.1%. The pH value of the residual alkali in the tested material was 11.9 (25°C).
[0206] Comparative Example 4
[0207] The difference between this comparative example and Example 3 is that the dopant Al2O3 used in S1 is replaced with an equal amount of Ta2O5.
[0208] Figure 21 The coin cell assembled from the ternary cathode material prepared for Comparative Example 4 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current / constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity was 222.4 mAh / g, and the capacity retention rate after 50 cycles was 89.1%. The pH value of the residual alkali in the tested material was 11.9 (25°C).
[0209] Comparative Example 5
[0210] The difference between this comparative example and Example 3 is that the second coating agent ZrO2 was not used in S4, and the amount of the second coating agent was made up by the third coating agent NH4H2PO4.
[0211] Figure 22 The coin cell assembled from the ternary cathode material prepared for Comparative Example 5 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current / constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity was 222.2 mAh / g, and the capacity retention rate after 50 cycles was 92.1%. The pH value of the residual alkali in the tested material was 11.9 (25°C).
[0212] Comparative Example 6
[0213] The difference between this comparative example and Example 3 is that the third coating agent NH4H2PO4 was not used in S4, and the amount of the third coating agent was made up by the second coating agent ZrO2.
[0214] Figure 23 The coin cell assembled from the ternary cathode material prepared for Comparative Example 6 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current / constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity was 221.7 mAh / g, and the capacity retention rate after 50 cycles was 92.2%. The pH value of the residual alkali in the tested material was 12.0 (25°C).
[0215] Comparative Example 7
[0216] The difference between this comparative example and Example 3 is that the first coating agent was not used in S1, and the amount of the first coating agent was made up by the dopant Al2O3.
[0217] Figure 24The coin cell assembled from the ternary cathode material prepared for Comparative Example 7 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current / constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity was 225.8 mAh / g, and the capacity retention rate after 50 cycles was 91.3%. The pH value of the residual alkali in the tested material was 11.9 (25°C).
[0218] Comparative Example 8
[0219] The difference between this comparative example and Example 3 is that no dopant Al2O3 was used in S1, and this part of the dopant was made up by the first coating agent.
[0220] Figure 25 The coin cell assembled from the ternary cathode material prepared for Comparative Example 8 was operated at 45°C with a charge / discharge voltage range of 2.7-4.25V. It underwent constant current / constant voltage charging at 0.5C with a charging cutoff current of 0.005C and constant current discharging at 0.5C. The highest discharge specific capacity was 224.9 mAh / g, and the capacity retention rate after 50 cycles was 89.4%. The pH value of the residual alkali in the tested material was 11.8 (25°C).
[0221] For ease of comparison, the relevant test results of Examples 1-10 and Comparative Examples 1-8 are summarized in Table 1.
[0222] Table 1 Comparison results of the examples and comparative examples
[0223] sample pH Discharge capacity (mAh / g) Volume retention rate after 50 laps Comparative Example 1 12.2 223.2 89.6％ Comparative Example 2 12.0 222.0 93.0％ Comparative Example 3 11.9 222.5 89.1％ Comparative Example 4 11.9 222.4 89.1％ Comparative Example 5 11.9 222.2 92.1％ Comparative Example 6 12.0 221.7 92.2％ Comparative Example 7 11.9 225.8 91.3％ Comparative Example 8 11.8 224.9 89.4％ Example 1 11.8 218.1 96.5％ Example 2 11.9 221.2 97.4％ Example 3 11.8 218.2 97.5％ Example 4 11.8 224.7 97.3％ Example 5 11.9 220.3 98.9％ Example 6 11.7 222.2 95.9％ Example 7 11.8 221.8 98.0％ Example 8 11.8 223.5 95.0％ Example 9 11.8 220.5 98.4％
[0224] As can be seen from the above, the ternary cathode material provided in this application embodiment has better cycle stability and a similar or lower residual alkali content than the comparative example; and after 50 cycles, there are fewer internal cracks.
[0225] In summary, the dopants used in this application can stabilize the crystal structure. Through multi-layer coating, the innermost coating layer is reinforced, improving electrochemical performance. Furthermore, the third coating agent can melt at low temperatures, achieving a seamless coating effect. The second coating agent acts as a framework, enhancing the material's cycle stability. The preparation method is simple, yielding polycrystalline high-nickel ternary cathode materials with low residual alkali content and high cycle stability.
[0226] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A polycrystalline high-nickel ternary cathode material, characterized in that, The polycrystalline high-nickel ternary cathode material includes secondary particles formed by the stacking of single-crystal primary particles, with the single-crystal primary particles contacting each other and forming grain boundaries. The lattice of the single-crystal primary particle is doped with a dopant, and the surface of the secondary particle and the grain boundary of the single-crystal primary particle are both covered with a first coating layer formed by a first coating agent; and the surface of the first coating layer is covered with a second coating layer formed by a third coating agent without dead corners, and the second coating layer corresponding to the surface of the secondary particle is covered with a framework formed by the second coating agent. The doping element of the dopant includes at least one of Al, Mg and Ti; the second coating agent is a material that does not melt during the secondary sintering process, and the third coating agent is a material that melts during the secondary sintering process; the temperature of the secondary sintering is 250-600℃.
2. The polycrystalline high-nickel ternary cathode material according to claim 1, characterized in that, The polycrystalline high-nickel ternary cathode material has at least one of the following characteristics: Feature 1: The chemical formula of the precursor of the polycrystalline high-nickel ternary cathode material is Ni x Co y Mn z (OH)2, x+y+z=1, 0.8≤x<1, 0<y+z≤0.2; Feature 2: The lithium source of the polycrystalline high-nickel ternary cathode material includes lithium hydroxide monohydrate; Feature 3: The first coating agent includes at least one of ZrO2, SeO2, Sb2O5, Sb2O3, Nb2O5, MoO3, TiO2, WO3, Ta2O5 and MgO.
3. The polycrystalline high-nickel ternary cathode material according to claim 2, characterized in that, The dopant includes aluminum compounds.
4. The polycrystalline high-nickel ternary cathode material according to claim 3, characterized in that, The dopant includes at least one of Al2O3 and Al(OH)3.
5. The polycrystalline high-nickel ternary cathode material according to any one of claims 2 to 4, characterized in that, The polycrystalline high-nickel ternary cathode material also has at least one of the following characteristics: Feature 4: The molar ratio of the precursor to the lithium source in the polycrystalline high-nickel ternary cathode material is 1:1 to 1:1.1; Feature 5: The molar ratio of the dopant to the precursor of the polycrystalline high-nickel ternary cathode material is 0.001:0.999-0.01:0.99; Feature 6: The molar ratio of the first coating agent to the precursor of the polycrystalline high-nickel ternary cathode material is 0.0005:1-0.01:
1.
6. The polycrystalline high-nickel ternary cathode material according to claim 4, characterized in that, The polycrystalline high-nickel ternary cathode material also has at least one of the following characteristics: Feature 8: The second coating agent includes at least one of Al2O3, ZrO2, Nb2O5, and TiO2; feature Nine: The third coating agent includes at least one of H3BO3, SeO2 and NH4H2PO4.
7. The polycrystalline high-nickel ternary cathode material according to claim 1, characterized in that, The total molar ratio of the second coating agent and the third coating agent to the ternary cathode material is 0.0005:1-0.01:
1.
8. The polycrystalline high-nickel ternary cathode material according to claim 6, characterized in that, The molar ratio of the second coating agent to the third coating agent is 1:2-2:
1.
9. The method for preparing the polycrystalline high-nickel ternary cathode material according to any one of claims 1-8, characterized in that, The process includes the following steps: sintering a mixture of a high-nickel ternary precursor, a lithium source, the dopant, and the first coating agent in a first sintering, followed by a second coating and a second sintering with the second and third coating agents.
10. The preparation method according to claim 9, characterized in that, After each sintering process, the sintered material is also crushed.
11. The preparation method according to claim 9 or 10, characterized in that, The temperature for the first sintering is 680-820℃.
12. The preparation method according to claim 11, characterized in that, The sintering process for a single sintering includes: first heating to 400-600℃ and holding for 0.1-3 hours, then heating to 680-820℃ and holding for 10-20 hours.
13. The preparation method according to claim 12, characterized in that, The heating rate corresponding to one sintering is 1-3℃ / min.
14. The preparation method according to claim 11, characterized in that, The first sintering is carried out in an oxygen atmosphere.
15. The preparation method according to claim 14, characterized in that, Oxygen purity ≥ 92%.
16. The preparation method according to claim 9, characterized in that, The secondary sintering time is 0.5-16 h.
17. The preparation method according to claim 9, characterized in that, The heating rate corresponding to the secondary sintering is 1-5℃ / min.
18. The preparation method according to claim 9, characterized in that, The secondary sintering is carried out in an oxygen atmosphere.
19. The preparation method according to claim 18, characterized in that, Oxygen purity ≥ 92%.
20. A battery, characterized in that, The positive electrode material of the battery includes the polycrystalline high-nickel ternary positive electrode material as described in any one of claims 1-8.