A polycrystalline ultra-high nickel ternary cathode material and its preparation method, lithium-ion battery and electrical equipment thereof

Abstract

This application provides a polycrystalline ultra-high nickel ternary cathode material and its preparation method, a lithium-ion battery, and an electrical device, relating to the field of lithium-ion batteries. The polycrystalline ultra-high nickel ternary cathode material includes a core, a first coating layer, and a second coating layer; the core has the general chemical formula LiNi. X M y M' Z O2; M includes at least two of Co, Mn, and Al, and M' includes at least two of Zr, Sr, Y, Sb, Al, W, Ta, Mg, Ca, Ti, Mo, and Nb; the first coating layer includes a lithium-M'' multi-element oxide composite, where M'' includes at least two of Sb, Al, Co, Ti, W, and P; the second coating layer includes a lithium-M''' oxide composite, where M''' includes one or more of B, Al, W, and Ti. This polycrystalline ultra-high nickel ternary cathode material exhibits excellent high-temperature storage performance and capacity.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and in particular to a polycrystalline ultra-high nickel ternary cathode material and its preparation method, lithium-ion batteries, and electrical devices. Background Technology

[0002] Layered transition metal oxide cathode materials have formed a relatively systematic and mature system based on the adjustment of their elemental and compositional ratios. Among them, nickel-cobalt-manganese or nickel-cobalt-aluminum material systems can be collectively referred to as ternary materials. When the molar amount of nickel in the layered transition metal oxide cathode material accounts for 80% of the total molar amount of the transition metal, it is called a high-nickel material. When the molar amount of nickel accounts for more than 90% of the total molar amount of the transition metal, it is generally called an ultra-high-nickel material. Ultra-high-nickel materials have advantages such as high capacity, high specific energy, relatively stable performance, and low cost. Under current technological conditions, the ultra-high-nickel ternary technology route has become the preferred choice in the field of power batteries. However, it is inevitable that people need to conduct more in-depth research and development and overcome more related technical problems to achieve more effective and widespread application of ultra-high-nickel materials. For example, the material structure stability deteriorates, and the increased gas generation during high-temperature storage leads to a decrease in cell safety.

[0003] With the widespread adoption of new structural technologies such as blade batteries, semi-solid-state batteries, and all-solid-state batteries, the sensitivity of battery systems to thermal management has significantly increased. For example, the large-size electrode design of blade batteries makes the internal gas generation pressure distribution more prone to unevenness, while tabless technology, although reducing internal resistance, also weakens heat dissipation efficiency. Against this backdrop, the high-temperature storage performance of cathode materials has evolved from a single electrochemical indicator to a core element of safety design. Currently, the industry requires high-nickel materials to maintain a capacity retention of ≥80% after 28 days of storage at 60℃, with gas generation controlled below 0.1 mL / Ah. However, existing commercial materials struggle to balance high-temperature performance and energy density. This contradiction is particularly pronounced in ultra-high-nickel systems, urgently requiring breakthroughs through intrinsic material modification.

[0004] Current efforts to improve the performance of high-nickel materials primarily focus on two dimensions: enhancing electrochemical performance and optimizing processes to reduce costs. At the material design level, developers aim to improve the specific capacity, cycle stability, and rate performance of materials by adjusting elemental composition ratios and particle size distribution, implementing elemental doping and surface coating modifications, and optimizing sintering regimes and post-processing procedures. At the manufacturing process level, the focus is on fine-tuning and optimizing equipment parameters and processes for key steps such as mixing, sintering (including temperature profile and atmosphere control), washing (e.g., pH adjustment), and pulverization, in order to achieve stable performance improvements and effective control of manufacturing costs.

[0005] With the gradual increase in nickel content, especially in ultra-high nickel polycrystalline ternary cathode materials, the cycle stability and high-temperature storage performance of ultra-high nickel materials become increasingly serious due to the increased instability of the intrinsic structure of the material, the weakening of the synergistic effect of nickel, cobalt and manganese, and the aggravation of interfacial side reactions caused by the enrichment of residual alkali on the surface.

[0006] At present, there is still no systematic research or in-depth exploration to address the key and difficult problems of cracking in ultra-high nickel cathode materials during cycling, which leads to decreased stability, and gas generation and reduced capacity retention in the prepared cells during high-temperature storage. Summary of the Invention

[0007] First, the solution provided in this application will be explained in more detail as follows:

[0008] The purpose of this application is to provide a polycrystalline ultra-high nickel ternary cathode material and its preparation method, a lithium-ion battery, and an electrical device to solve the above-mentioned problems.

[0009] To achieve the above objectives, the first aspect of this application provides a polycrystalline ultra-high nickel ternary cathode material, comprising a core and a first coating layer and a second coating layer sequentially disposed on the surface of the core;

[0010] The general chemical formula of the core is LiNi. X M y M' Z O2, wherein 0.8≤x≤0.98, 0.02≤y≤0.15, 0.001≤z≤0.06, x+y+z=1; M includes at least two of Co, Mn, and Al, and M' includes at least two of Zr, Sr, Y, Sb, Al, W, Ta, Mg, Ca, Ti, Mo, and Nb;

[0011] The first coating layer comprises a lithium-M'' multi-element oxide composite, wherein M'' comprises at least two of Sb, Al, Co, Ti, W, and P;

[0012] The second coating layer comprises a lithium-M''' oxide complex, wherein M''' comprises one or more of B, Al, W and Ti.

[0013] Optionally, the polycrystalline ultra-high nickel ternary cathode material satisfies at least one of the following conditions:

[0014] (1) M' includes Zr, Sr, Y, Sb, Al and Ta;

[0015] The core comprises, from the inside out, a bulk region, a subsurface region, and a surface region. The radius of the bulk region is 0.3-0.9 times the radius of the core. The subsurface region lies between the bulk region and the surface region. The diameter of the surface region is ≤50nm.

[0016] The doping elements in the bulk region include Y, Sb, and Al;

[0017] The doping elements in the subsurface region include Ta and Zr;

[0018] The surface region includes Sr and Zr;

[0019] (2) M'' includes Sb, Al and Co;

[0020] (3) The M''' includes B and Al.

[0021] Optionally, the polycrystalline ultra-high nickel ternary cathode material satisfies at least one of the following conditions:

[0022] (1) The general chemical formula of the kernel is:

[0023] LiNi X M y Y 0.0001-0.01 Sb 0.0001-0.01 Al 0.0001-0.01 Ta 0.0001-0.005 Sr 0.0001-0.01 Zr 0.0001-0.01 O2;

[0024] (2) The concentration of Sb in the first coating layer is 300-1200 ppm;

[0025] (3) The concentration of Co in the first coating layer is 3000-8000 ppm;

[0026] (4) The concentration of Al in the first coating layer is 100-600 ppm;

[0027] (5) The concentration of B in the second coating layer is 100-300 ppm;

[0028] (6) The concentration of Al in the second coating layer is 200-800 ppm.

[0029] Optionally, the polycrystalline ultra-high nickel ternary cathode material satisfies at least one of the following conditions:

[0030] (1) The thickness of the first coating layer is 0.5-10 nm;

[0031] (2) The thickness of the second coating layer is 0.5-6.5 nm;

[0032] (3) The aspect ratio of the primary particles of the polycrystalline ultra-high nickel ternary cathode material is ≤1.8;

[0033] (4) The primary particle roundness of the polycrystalline ultra-high nickel ternary cathode material is ≤1.0;

[0034] (5) The secondary particle porosity of the polycrystalline ultra-high nickel ternary cathode material is ≤3%;

[0035] (6) The D50 of the polycrystalline ultra-high nickel ternary cathode material is 3-18 μm.

[0036] The second aspect provides a method for preparing the aforementioned polycrystalline ultra-high nickel ternary cathode material, comprising:

[0037] Under aerobic conditions, the precursor Ni a M b (OH)2, lithium source, and M'-containing compound are first mixed to obtain a first mixture, and the first mixture is first sintered to obtain a sintered material;

[0038] The first calcined material and the M''-containing compound are mixed a second time to obtain a second mixture, and the second mixture is sintered a second time to obtain a second calcined material;

[0039] The two calcined materials are washed with water to obtain the washed material.

[0040] The washed material and the M''' compound are mixed for a third time to obtain a third mixture. The third mixture is then sintered for a third time to obtain a polycrystalline ultra-high nickel ternary cathode material.

[0041] Optionally, the preparation method of the polycrystalline ultra-high nickel ternary cathode material satisfies at least one of the following conditions:

[0042] (1) The M'-containing compound includes one or more of the following: oxides, hydroxides, and carbonates containing M';

[0043] (2) The lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium acetate, lithium fluoride, lithium nitrate and lithium oxalate and their hydrates;

[0044] (3) The M''-containing compound includes one or more of the following: oxides, hydroxides, and carbonates containing M'';

[0045] (4) The M''' compound includes one or more of the following: oxides, hydroxides and carbonates containing M''';

[0046] (5) When performing the water washing, the additives used include sodium aluminate and / or sodium metasilicate;

[0047] The concentration of the additive is 0.01-0.1 mol / L;

[0048] (6) The oxygen content under the aforementioned aerobic conditions is ≥80%;

[0049] (7) The precursor Ni a M b (OH)2, the molar ratio of Li in the lithium source to M' in the M'-containing compound is 1:1.03-1.08:0.001-0.06;

[0050] (8) The concentration of M'' in the second mixture is 3400-9800 ppm;

[0051] (9) The concentration of M''' in the third mixture is 300-1100 ppm.

[0052] Optionally, the M'''-containing compound includes one or more of aluminum oxide, aluminum hydroxide, boron nitride, boric acid, and boron oxide;

[0053] The specific surface area of ​​the alumina is 20-80 m². 2 / g.

[0054] Optionally, the preparation method of the polycrystalline ultra-high nickel ternary cathode material satisfies at least one of the following conditions:

[0055] (1) The first sintering includes a fourth sintering, a fifth sintering and a sixth sintering performed sequentially;

[0056] The heating rate of the fourth sintering is 1-2℃ / min, the final temperature is 450-550℃, and the holding time is 2-7h.

[0057] The fifth sintering process has a heating rate of 0.5-4℃ / min, an endpoint temperature of 550-670℃, and a holding time of 8-20h.

[0058] The heating rate of the sixth sintering is 5-10℃ / min, the final temperature is 670-790℃, and the holding time is 10-18h.

[0059] (2) The heating rate of the second sintering is 1-2℃ / min, the final temperature is 600-700℃, and the time is 6h-15h;

[0060] (3) The heating rate of the third sintering is 2-8℃ / min, the final temperature is 200-350℃, and the time is 5h-11h.

[0061] The third aspect provides a lithium-ion battery, including the aforementioned polycrystalline ultra-high nickel ternary cathode material.

[0062] The fourth aspect provides an electrical device including the aforementioned lithium-ion battery.

[0063] Compared with the prior art, the beneficial effects of this application include:

[0064] The polycrystalline ultra-high nickel ternary cathode material provided in this application enhances the bulk and surface structure strength of the cathode material through the metal element M', thereby improving high-temperature storage performance. A shell layer is formed on the core surface using a lithium-M'' multi-element oxide composite, improving interfacial ion transport capability and high-temperature storage performance, and further consuming soluble lithium on the cathode material surface. Finally, an outermost coating layer is formed by encapsulating the material with a lithium-M''' oxide composite. This coating layer is an ion-conducting coating layer, enhancing the Li diffusion rate and filling surface pores, further improving the high-temperature storage performance. The polycrystalline ultra-high nickel ternary cathode material provided in this application exhibits excellent high-temperature storage performance and capacity.

[0065] The method for preparing polycrystalline ultra-high nickel ternary cathode material provided in this application is simple to operate and uses readily available raw materials. The performance of the prepared ultra-high nickel ternary cathode material is significantly improved. Compared with the unmodified product, under the voltage range of 2.8-4.3V in coin cell testing at room temperature of 25℃, the specific capacity at 0.1C charging is 250.6mAh / g, the specific capacity at 0.1C discharging is 241.0mAh / g, and the initial charge-discharge efficiency is 96.2%; the capacity retention rate after 100 cycles is 98.2%; in high-temperature storage performance, the capacity recovery rate is 95.0%, and the volume change rate is 44.6%, comprehensively demonstrating ultra-high discharge specific capacity and excellent high-temperature storage performance.

[0066] The lithium-ion battery and electrical equipment provided in this application have excellent high-temperature storage performance and capacity. Attached Figure Description

[0067] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0068] Figure 1 A cross-sectional SEM image of the polycrystalline ultra-high nickel ternary cathode material provided in Example 1;

[0069] Figure 2 XPS etching pattern of Y element in the polycrystalline ultra-high nickel ternary cathode material provided in Example 1;

[0070] Figure 3 XPS etching pattern of Sb element in the polycrystalline ultra-high nickel ternary cathode material provided in Example 1;

[0071] Figure 4 XPS etching pattern of Al element in the polycrystalline ultra-high nickel ternary cathode material provided in Example 1;

[0072] Figure 5 XPS etching pattern of Ta element in the polycrystalline ultra-high nickel ternary cathode material provided in Example 1;

[0073] Figure 6 XPS etching pattern of Zr element in the polycrystalline ultra-high nickel ternary cathode material provided in Example 1;

[0074] Figure 7 XPS etching pattern of Sr element in the polycrystalline ultra-high nickel ternary cathode material provided in Example 1;

[0075] Figure 8 The image shows a front-side SEM image of the polycrystalline ultra-high nickel ternary cathode material provided in Example 1.

[0076] Figure 9 The graphs show the 0.1 C charge-discharge capacity test results of the batteries prepared in Example 1 and Comparative Example 1, respectively.

[0077] Figure 10 The graphs show the capacity retention rate of the batteries prepared in Example 1 and Comparative Example 1 after 100 cycles at 1C rate.

[0078] Figure 11 This is a schematic diagram showing the volume change of the batteries prepared in Example 1 and Comparative Example 1 after 28 days of storage at 70°C.

[0079] Figure 12 This is a schematic diagram showing the 28-day storage-capacity recovery rate of the batteries prepared in Example 1 and Comparative Example 1 at 70°C. Detailed Implementation

[0080] First, the solution provided in this application will be explained in more detail as follows:

[0081] The first aspect provides a polycrystalline ultra-high nickel ternary cathode material, comprising a core and a first coating layer and a second coating layer sequentially disposed on the surface of the core;

[0082] The general chemical formula of the core is LiNi. X M y M' Z O2, wherein 0.8≤x≤0.98, 0.02≤y≤0.15, 0.001≤z≤0.06, x+y+z=1; M includes at least two of Co, Mn, and Al, and M' includes at least two of Zr, Sr, Y, Sb, Al, W, Ta, Mg, Ca, Ti, Mo, and Nb;

[0083] Optionally, the general chemical formula of the core is LiNi. X M y M' Z In O2, x can be any value between 0.8, 0.9, 0.98, or 0.8-0.98, and z can be any value between 0.001, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, or 0.001-0.06.

[0084] Preferably, 0.85 ≤ a ≤ 0.96;

[0085] The first coating layer comprises a lithium-M'' multi-element oxide composite, wherein M'' comprises at least two of Sb, Al, Co, Ti, W, and P;

[0086] The second coating layer comprises a lithium-M''' oxide complex, wherein M''' comprises one or more of B, Al, W and Ti.

[0087] In some embodiments, the polycrystalline ultra-high nickel ternary cathode material satisfies at least one of the following conditions:

[0088] (1) M' includes Zr, Sr, Y, Sb, Al and Ta;

[0089] The core comprises, from the inside out, a bulk region, a subsurface region, and a surface region. The radius of the bulk region is 0.3-0.9 times the radius of the core. The subsurface region lies between the bulk region and the surface region. The diameter of the surface region is ≤50nm.

[0090] Optionally, the radius of the bulk region can be any value between 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 0.3-0.9 of the core radius, and the diameter of the surface region can be any value between 10nm, 20nm, 30nm, 40nm, 50nm or ≤50nm.

[0091] It is important to note that grain boundaries in the surface region refer to the interfaces between grains of the same chemical composition in polycrystalline materials, while the cladding layer is a heterogeneous material, and its interface with the matrix material is called a "phase interface." These are two different concepts. Grain boundaries exist within the matrix material and are the boundaries between primary particles in ultra-high nickel ternary materials. They are entirely located within the core matrix material, and the grains on both sides of them are predominantly NCM in chemical composition, possibly enriched with dopants (such as Zr, Sr, etc.). Function: The described effects such as grain boundary pinning and microcrack suppression occur at this interface.

[0092] Coating-matrix interface: A heterogeneous interface existing between the core matrix and the outer coating layer. Location: Located between the outer surface of the core matrix material and the coating layer (such as a Co-Al-Sb-O composite layer). Composition: One side is the NCM matrix, and the other side is a coating layer with a completely different chemical composition (such as Co3O4, LiSbO3, Al2O3, etc.). Function: The described effects of isolating the electrolyte, reducing side reactions, and stabilizing surface oxygen mainly occur at this interface. Therefore, the concept of "grain boundary" in this application explicitly does not include the coating layer. The coating layer is one or more thin layers of different composition attached to the outermost part of the matrix particles;

[0093] The doping elements in the bulk region include Y, Sb, and Al;

[0094] The doping elements in the subsurface region include Ta and Zr;

[0095] The surface region includes Sr and Zr;

[0096] It is important to note that by precisely controlling the distribution of M' doping elements, targeted enhancement of the functions of different regions can be achieved, Y 3+ Sb 5+ And Al 3+ Y has strong ion diffusion capabilities, enabling it to penetrate into the interior of primary particles and form a "rigid framework network" in the bulk region; 3+ and Sb 5+ The high bond energy of Al stabilizes the oxygen lattice, while Al 3+ The uniform distribution of Sb provides basic structural stability. 5+ With Y 3+ The charge difference induces a local electric field effect, promoting the Li + The directional migration of these three elements, through their synergistic effect, can significantly reduce the internal stress of the material.

[0097] In addition, a Ta-Zr co-doped concentration gradient layer is constructed in the subsurface region of the primary particles. 5+ Increase the lithium layer spacing, Zr 4+ This strengthens lattice integrity, and the synergistic effect of the two can effectively improve the lithium-ion diffusion coefficient;

[0098] Sr enrichment and Zr pinning were performed in the surface region, specifically: Sr, with the largest ion diameter, was enriched in the outermost layer of the primary particles. 2+ This forms an electrostatic shielding layer. During sintering, Zr has a high diffusion activation energy, causing it to agglomerate at the surface of primary particles on the secondary particle surface, forming local pinning points. This distribution effectively inhibits abnormal grain growth and reduces the generation of microcracks caused by grain boundary stress concentration during cycling. Simultaneously, a small amount of Zr enters the bulk phase... 4+It can increase the Li interlayer spacing (c-axis direction) and promote Li + Diffusion kinetics;

[0099] In addition, under high temperature conditions (600~700℃), some Al 3+ It can diffuse into the bulk phase, replace Ni sites, and form strong Al-O bonds (bond energy of ~512kJ / mol, higher than Ni-O bond ~300kJ / mol), inhibiting lattice oxygen release and microcrack propagation;

[0100] (2) M'' includes Sb, Al and Co;

[0101] In some embodiments, when M'' includes Sb, Al, and Co, the first coating layer includes a Co3O4 spinel phase, a Sb2O4 phase, an Al2O3 phase, a Sb2O3-Al2O3 phase, a Co3O4-Sb2O4-LiSbO3 phase, and a Li c CoO2 rock salt phase, wherein 0.01≤c≤1;

[0102] It is important to note that spinel Co3O4 is a p-type semiconductor with excellent electronic conductivity, which can effectively construct an electronic conductivity network. The Sb2O3-Al2O3 phase is relatively stable and can reduce electrolyte erosion at the material interface. It also contributes to improved high-temperature storage performance, reduces high-temperature gas generation, and effectively improves capacity recovery. Furthermore, it has good electronic conductivity, reducing interfacial impedance. Additionally, under aerobic conditions, high-temperature sintering transforms Sb2O3 into the Sb2O4 phase, meaning Sb2O3 further forms a highly stable surface phase (Sb2O4), improving interfacial capabilities, enhancing room-temperature or high-temperature cycling and high-temperature storage capabilities, and providing dual conductive channels for both electronic and ionic conductivity. The specific chemical formulas are as follows:

[0103] Sb₂O₃ + O₂ → Sb₂O₄;

[0104] The Sb2O4 phase exhibits excellent high-temperature stability (structural stability without decomposition at ≤1000℃, and chemical inertness significantly higher than Sb2O3; its high stability can suppress the dissolution of the coating layer during cycling and greatly reduce surface side reactions).

[0105] In some embodiments, under suitable reaction atmosphere (sufficient oxygen), reaction temperature (600-700℃), and lithium source activity conditions (2LiOH→Li2O+H2O, high temperature atmosphere), highly active Li2O will partially react with Sb2O3 to generate Li-Sb-O compound (LiSbO3, ionic conductor), ultimately forming a dual conductive channel of Co3O4-Sb2O4-LiSbO3 → electronic conductivity + ionic conductivity;

[0106] The Al2O3 phase is relatively stable and can reduce electrolyte erosion at the material interface, effectively improve the stability of the material interface, and enhance the material's long-term cycle retention rate at room temperature / high temperature. The Al2O3 phase can inhibit lattice oxygen release and reduce interfacial side reactions.

[0107] (3) The M''' includes B and Al.

[0108] It should be noted that when M''' includes B, the formed Li d BO e Glassy coating enhances Li + Diffusion rate, B 3+ Doping reduces cation mixing and suppresses cyclic phase transitions; when M''' includes Al, it improves the high-temperature storage performance of the material.

[0109] In some embodiments, the polycrystalline ultra-high nickel ternary cathode material satisfies at least one of the following conditions:

[0110] (1) The general chemical formula of the kernel is:

[0111] LiNi X M y Y 0.0001-0.01 Sb 0.0001-0.01 Al 0.0001-0.01 Ta 0.0001-0.005 Sr 0.0001-0.01 Zr 0.0001-0.01 O2;

[0112] It is important to note that Zr acts as grain boundary pinning, widening the lithium interlayer spacing and suppressing microcracks. When the Zr content is below 0.0001 in the general formula, the grain boundary strength is insufficient, accelerating crack propagation during cycling. Above 0.01, excessive Zr enrichment blocks lithium channels, increasing impedance. Sr's main function is to lower the melting point of the material during synthesis, which is beneficial for high-temperature storage. When the Sr content is below 0.0001 in the general formula, surface oxygen release is not sufficiently suppressed, and interfacial side reactions are aggravated. Above 0.01, lattice distortion increases, leading to capacity decay. Y acts as a bulk oxygen vacancy suppressor and bond energy strengthening agent. When the Y content is below 0.0001 in the general formula, oxygen evolution is aggravated, and thermal stability decreases. Above 0.01, the ionic radius is large, and excess Y leads to distortion of the layered structure. Sb acts as a high-valence state (Sb 5+ Compensating for charge and improving electronic conductivity, when the Sb content is below 0.0001 in the general chemical formula, Ni... 2 +Increased concentrations of Al exacerbate cation mixing; above 0.01%, Al occupies lithium sites, blocking diffusion and reducing rate performance. Al stabilizes the TM layer framework, raising the exothermic peak temperature by 20-30°C. When the Al content is below 0.0001% in the general chemical formula, the risk of thermal runaway increases (<180°C); above 0.01%, it may cause capacity loss. Ta acts as a subsurface gradient doping agent, broadening the Li-Li layer. + The channel generates a pillar effect; when the Ta content is below 0.0001 in the general chemical formula, the Li layer collapse is not adequately suppressed, and the cycling capacity decays rapidly; when it is above 0.005, the high valence state overcompensates the charge, causing phase transition instability.

[0113] Preferably, the general chemical formula of the kernel is:

[0114] LiNi X M y Y 0.001 Sb 0.001 Al 0.001 Ta 0.0005 Sr 0.001 Zr 0.001 O2;

[0115] (2) The concentration of Sb in the first coating layer is 300-1200 ppm;

[0116] Optionally, the concentration of Sb in the first coating layer can be 300 ppm, 600 ppm, 900 ppm, 1200 ppm or any value between 300 and 1200 ppm;

[0117] (3) The concentration of Co in the first coating layer is 3000-8000 ppm;

[0118] Optionally, the concentration of Co in the first coating layer can be any value between 3000 ppm, 4000 ppm, 5000 ppm, 6000 ppm, 7000 ppm, 8000 ppm or 3000-8000 ppm;

[0119] (4) The concentration of Al in the first coating layer is 100-600 ppm;

[0120] Optionally, the concentration of Al in the first coating layer can be any value between 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm or 100-600 ppm;

[0121] (5) The concentration of B in the second coating layer is 100-300 ppm;

[0122] Optionally, the concentration of Al in the first coating layer can be 100 ppm, 200 ppm, 300 ppm or any value between 100 and 300 ppm;

[0123] (6) The concentration of Al in the second coating layer is 200-800 ppm.

[0124] Optionally, the concentration of Al in the second coating layer can be any value between 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm or 200-800ppm.

[0125] In some embodiments, the polycrystalline ultra-high nickel ternary cathode material satisfies at least one of the following conditions:

[0126] (1) The thickness of the first coating layer is 0.5-10 nm;

[0127] Optionally, the thickness of the first coating layer can be 0.5nm, 1nm, 5nm, 10nm or any value between 0.5-10nm;

[0128] Preferably, the thickness of the first coating layer is 1.5-4.5 nm;

[0129] (2) The thickness of the second coating layer is 0.5-6.5 nm;

[0130] Optionally, the thickness of the second coating layer can be 0.5nm, 1nm, 2nm, 4nm, 6nm, 6.5nm or any value between 0.5 and 6.5nm;

[0131] Preferably, the thickness of the second coating layer is 1-2.5 nm;

[0132] It is worth noting that the optimal combination of M' element in the core is Zr+Sr+Y+Sb+Al+Ta. Due to the synergistic regulation of grain growth anisotropy by the Zr-Sb-Sr ternary element, the aspect ratio of primary particles is ≤1.8 and the roundness of primary particles is ≤1.0. At the same time, the oxygen vacancy gradient diffusion induced by Ta makes the porosity of secondary particles ≤3%. The two synergistically improve the porosity of secondary particles. This mechanism solves the inherent contradiction in the morphology control of ultra-high nickel materials through element spatial positioning (surface / grain boundary / bulk phase) and intervention of kinetic processes (diffusion / grain boundary slip / liquid phase sintering).

[0133] (3) The aspect ratio of the primary particles of the polycrystalline ultra-high nickel ternary cathode material is ≤1.8;

[0134] Optionally, the aspect ratio of the primary particles of the polycrystalline ultra-high nickel ternary cathode material can be any value of 0.1, 0.5, 1, 1.8 or ≤1.8;

[0135] (4) The primary particle roundness of the polycrystalline ultra-high nickel ternary cathode material is ≤1.0;

[0136] Optionally, the primary particle roundness of the polycrystalline ultra-high nickel ternary cathode material can be any value of 0.1, 0.5, 1 or ≤1;

[0137] Preferably, the primary particle roundness of the polycrystalline ultra-high nickel ternary cathode material is 0.6-0.7; within this roundness range, the lithium-ion diffusion and transport distance is greatly reduced.

[0138] (5) The secondary particle porosity of the polycrystalline ultra-high nickel ternary cathode material is ≤3%;

[0139] Optionally, the secondary particle porosity of the polycrystalline ultra-high nickel ternary cathode material can be any value of 0.1, 0.5, 1, 2, 3 or ≤3;

[0140] Preferably, the secondary particle porosity of the polycrystalline ultra-high nickel ternary cathode material is 1%-2%, which is beneficial to the material's high-temperature storage performance.

[0141] (6) The D50 of the polycrystalline ultra-high nickel ternary cathode material is 3-18 μm.

[0142] Optionally, the D50 of the polycrystalline ultra-high nickel ternary cathode material can be any value between 3μm, 6μm, 9μm, 12μm, 15μm, 18μm, or 3-18μm.

[0143] Preferably, the D50 of the polycrystalline ultra-high nickel ternary cathode material is 9-11 μm.

[0144] The second aspect provides a method for preparing the aforementioned polycrystalline ultra-high nickel ternary cathode material, comprising:

[0145] Under aerobic conditions, the precursor Ni a M b (OH)2, lithium source, and M'-containing compound are first mixed to obtain a first mixture, and the first mixture is first sintered to obtain a sintered material;

[0146] The first calcined material and the M''-containing compound are mixed a second time to obtain a second mixture, and the second mixture is sintered a second time to obtain a second calcined material;

[0147] The two calcined materials are washed with water to obtain the washed material.

[0148] The washed material and the M''' compound are mixed for a third time to obtain a third mixture. The third mixture is then sintered for a third time to obtain a polycrystalline ultra-high nickel ternary cathode material.

[0149] In some embodiments, the preparation method of the polycrystalline ultra-high nickel ternary cathode material satisfies at least one of the following conditions:

[0150] (1) The M'-containing compound includes one or more of the following: oxides, hydroxides, and carbonates containing M';

[0151] (2) The lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium acetate, lithium fluoride, lithium nitrate and lithium oxalate and their hydrates;

[0152] (3) The M''-containing compound includes one or more of the following: oxides, hydroxides, and carbonates containing M'';

[0153] Optionally, when the M''-containing compound includes Co, the M''-containing compound includes cobalt hydroxyoxide;

[0154] In some embodiments, cobalt hydroxyl oxide partially decomposes at high temperatures to produce Co3O4, while also generating some oxygen. The released oxygen can be captured and utilized by Sb2O3 to participate in the Sb2O4 oxidation reaction, replenishing oxygen vacancies on the surface of the cathode material. Additionally, cobalt hydroxyl oxide decomposes residual alkali (Li2CO3, LiOH) to generate lithium-deficient cobalt oxide, consuming some LiOH. Simultaneously, the active oxygen generated during decomposition oxidizes Li2CO3. Reducing residual alkali on the cathode material surface effectively improves the overall material performance, mitigating problems such as deteriorated electrochemical performance, significantly reduced processing performance, and safety performance caused by excessive residual alkali. The partially generated lithium-deficient cobalt oxide can broaden lithium-ion channels, compensating for the low initial efficiency and poor rate performance caused by the low Co content in ultra-high nickel ternary cathode materials, providing additional Co... 3+ Active sites improve the kinetic sluggishness caused by low Co content; the role of cobalt hydroxyl oxide is to directionally consume residual base + improve rate performance + build surface electronic conductive network;

[0155] (4) The M''' compound includes one or more of the following: oxides, hydroxides and carbonates containing M''';

[0156] (5) When performing the water washing, the additives used include sodium aluminate and / or sodium metasilicate;

[0157] The concentration of the additive is 0.01-0.1 mol / L;

[0158] Optionally, the concentration of the additive can be 0.01 mol / L, 0.05 mol / L, 0.1 mol / L, or any value between 0.01 and 0.1 mol / L;

[0159] Optionally, water washing with a water-washing additive containing sodium aluminate can form an Al2O3 coating layer in situ, which can inhibit electrolyte corrosion, reduce transition metal dissolution, and prevent the re-adsorption of residual alkali on the surface. Simultaneously, it neutralizes residual alkali on the surface, significantly reduces the pH value of the material, and improves processing performance. Secondly, Al... 3+ During sintering, it can migrate to the surface lattice of the material, fill the oxygen vacancies caused by the lithium-nickel mixture in high-nickel materials, inhibit the formation of rock salt phase (NiO), and improve structural stability;

[0160] Excessive amounts of water-washing additives containing sodium aluminate can lead to an excessively thick coating layer, hindering lithium-ion diffusion and reducing the effective capacity of the material. Insufficient water-washing additives, on the other hand, cannot effectively reduce alkali and improve the material's processing performance and high-temperature storage properties.

[0161] (6) The oxygen content under the aerobic conditions is ≥80%.

[0162] Optionally, the oxygen content under aerobic conditions can be any value of 80%, 85%, 90%, 95%, 99%, or ≥80%.

[0163] Preferably, the oxygen content during the first sintering is ≥97.5%; the oxygen content during the second and third sintering is independently ≥90%.

[0164] (7) The precursor Ni a M b (OH)2, the molar ratio of Li in the lithium source to M' in the M'-containing compound is 1:1.03-1.08:0.001-0.06;

[0165] Optional, precursor Ni a M b (OH)2, the molar amounts of Li in the lithium source and M' in the M'-containing compound can be any value between 1:1.03:0.001, 1:1.05:0.001, 1:1.08:0.001, 1:1.03:0.005, 1:1.03:0.01, 1:1.03:0.03, 1:1.03:0.06, or 1:1.03-1.08:0.001-0.06;

[0166] (8) The concentration of M'' in the second mixture is 3400-9800 ppm;

[0167] Optionally, the concentration of M'' in the second mixture can be any value between 3400ppm, 4000ppm, 6000ppm, 8000ppm, 9000ppm, 9800ppm or 3400-9800ppm;

[0168] (9) The concentration of M''' in the third mixture is 300-1100 ppm.

[0169] Optionally, the concentration of M''' in the third mixture can be 300ppm, 500ppm, 700ppm, 900ppm, 1100ppm or any value between 300 and 1100ppm.

[0170] In some embodiments, the M'''-containing compound includes one or more of aluminum oxide, aluminum hydroxide, boron nitride, boric acid, and boron oxide;

[0171] The specific surface area of ​​the alumina is 20-80 m². 2 / g.

[0172] Optionally, the specific surface area of ​​alumina can be 20 m². 2 / g、30 m 2 / g、40 m 2 / g、50 m 2 / g、60 m 2 / g、70m 2 / g、80 m 2 / g or 20-80 mg 2 Any value between / g.

[0173] It should be noted that alumina with a low surface area can drive discontinuous distribution. Alumina with a small specific surface area has a large particle size (30-80 nm), a low surface atomic ratio, low surface energy, and a high migration energy barrier. During sintering, it is difficult to completely cover the cathode surface through Brownian motion. Instead, it preferentially anchors at grain boundaries / defects to form island-like coatings.

[0174] In some embodiments, when the M''' compound includes boron oxide and aluminum oxide, molten B2O3 acts as a "binder" to fix the aluminum oxide particles on the positive electrode surface. However, due to its high viscosity, it cannot be completely spread into a film, thus forming a composite structure of "alumina islands + borate glass matrix". This composite structure optimizes ion conduction, and the island-like gaps retain Li + Fast track.

[0175] When the specific surface area of ​​alumina is too small, the alumina particle size is too large, resulting in uneven coverage; when the specific surface area of ​​alumina is too large, a dense and continuous film will be formed, leading to a surge in interfacial impedance.

[0176] In some embodiments, the preparation method of the polycrystalline ultra-high nickel ternary cathode material satisfies at least one of the following conditions:

[0177] (1) The first sintering includes a fourth sintering, a fifth sintering and a sixth sintering performed sequentially;

[0178] The heating rate of the fourth sintering is 1-2℃ / min, the final temperature is 450-550℃, and the holding time is 2-7h.

[0179] Optionally, the heating rate of the fourth sintering can be any value between 1℃ / min, 1.5℃ / min, 2℃ / min or 1-2℃ / min, the final temperature can be any value between 450℃, 500℃, 550℃ or 450-550℃, and the holding time can be any value between 2h, 4h, 5h, 7h or 2-7h.

[0180] The fifth sintering process has a heating rate of 0.5-4℃ / min, an endpoint temperature of 550-670℃, and a holding time of 8-20h.

[0181] Optionally, the heating rate of the fifth sintering can be any value between 0.5℃ / min, 1℃ / min, 2℃ / min, 4℃ / min or 0.5-4℃ / min, the final temperature can be any value between 550℃, 600℃, 670℃ or 550-670℃, and the time can be any value between 8h, 10h, 15h, 20h or 8-20h.

[0182] The heating rate of the sixth sintering is 5-10℃ / min, the final temperature is 670-790℃, and the holding time is 10-18h.

[0183] Optionally, the heating rate of the sixth sintering can be any value between 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min or 5-10℃ / min, the final temperature can be any value between 670℃, 700℃, 750℃, 790℃ or 670-790℃, and the holding time can be any value between 10h, 12h, 14h, 16h, 18h or 10-18h.

[0184] It is important to note that the doping sites of the doping elements are controlled by the parameters of the fourth, fifth, and sixth sintering stages. Specifically, the main function of the fourth sintering stage is to open grain boundary channels, facilitate precursor decomposition and lithium salt melt pre-diffusion, and allow the precursor to dehydrate at 500℃ to form nanoscale pores (typically 2-5 nm in diameter), which allows Zr to... 4+ (0.72Å) diffuses along the pores of secondary particles to the grain boundaries between primary particles, Sr 2+ (Radius 1.18 Å) Due to the size effect, it is retained on the surface and adsorbed on the particle surface to reduce the energy barrier, that is, the surface region (Sr enrichment + Zr pinning) is constructed;

[0185] Therefore, if the fourth sintering temperature is too low, incomplete dehydration will occur, leading to localized lithium aggregation, uneven lithium distribution, and increased cation mixing. Too low a temperature will also affect the Sr / Zr distribution at grain boundaries. Conversely, if the fourth sintering temperature is too high, the H2O vaporization rate will be too fast, causing particle breakage and affecting Ni. 2+ Premature oxidation leads to a surge in oxygen vacancies, and excessively high temperatures can cause Zr to form ZrO2 prematurely, thereby blocking the channels.

[0186] The fifth sintering process primarily involves the kinetic diffusion of bulk element doping, specifically the Y / Al / Sb element combination. During this stage, YO bonds recombine, and Al... 3+ The particles fill the tetrahedral gaps, and Sb achieves selective adsorption on crystal planes. At this stage, the roundness of the particles increases, i.e., the bulk region (Y / Sb / Al synergy) is constructed.

[0187] When the fifth sintering temperature is too low, it will lead to insufficient crystallinity (I 003 / I 104 <1.2), insufficient Y solid solubility, and insufficient Sb inhibition of crystal plane growth; excessively high temperatures can lead to abnormal grain growth, Ni 3+ Reduction leads to the formation of rock salt phase, while Sb excessively occupies Li sites;

[0188] The main mechanism of the sixth sintering process lies in the elemental gradient diffusion construction. Ta exhibits a gradient distribution in the subsurface layer at approximately 50-200 nm, while supersaturated Zr... 4+ The precipitation forms a Ta / Zr gradient transition, i.e., the construction of the subsurface region;

[0189] When the sixth sintering temperature is too high, it will cause Ta to accumulate on the surface, trigger cracks, and destroy the layered structure. When the sixth sintering temperature is too low, it will cause insufficient Ta gradient distribution, excessively thick Sr-induced surface rock salt phase, and failure of the pinning effect brought by ZrO2.

[0190] For example, when M' includes Zr, Sr, Y, Sb, Al and Ta, the doping elements and doping mechanisms of the core are shown in Table 1.

[0191] Table 1. Doping elements and doping mechanisms in the kernel

[0192]

[0193] In addition to the ionic radius of the M' dopant, the diffusion barrier of the M' dopant is also relevant during sintering; for example, Ta 5+Zr has a large atomic radius and a high diffusion energy barrier. High activation energy requires high temperature driving, so the calcination temperature is the highest. Similarly, Zr preferentially accumulates along the grain boundaries during calcination. After heating, it will precipitate along the grain boundaries (penetrating to the subsurface of the primary particles), which is low-temperature pore diffusion + high-temperature grain boundary precipitation.

[0194] (2) The heating rate of the second sintering is 1-2℃ / min, the final temperature is 600-700℃, and the time is 6h-15h;

[0195] Optionally, the heating rate of the second sintering can be any value between 1℃ / min, 1.5℃ / min, 2℃ / min or 1-2℃ / min, the final temperature can be any value between 600℃, 650℃, 700℃ or 600-700℃, and the time can be any value between 6h, 10h, 15h or 6h-15h.

[0196] It is important to note that the core function of the second sintering temperature setting is to build the coating layer gradient and interface chemical bonding. When the second sintering temperature is too low, it will lead to the residue and insufficient decomposition of M'' compounds, resulting in the interruption of electron channels and the loss of conductive network. When the second sintering temperature is too high, it will lead to the premature release of active oxygen, thereby oxidizing the core and destroying the core layered structure.

[0197] It should also be noted that, based on the first sintering, the addition of a compound containing M'' for the second sintering further reduces the residual alkali on the material surface and reduces the risk of the core directly contacting the electrolyte; the water washing process, based on the second sintering process, not only further reduces the residual alkali but also forms an in-situ coating layer on the surface, improving the material's processing performance; the use of a compound containing M''' for the third sintering further fills the pores on the material surface and improves the material's high-temperature storage performance.

[0198] (3) The heating rate of the third sintering is 2-8℃ / min, the final temperature is 200-350℃, and the time is 5h-11h.

[0199] Optionally, the heating rate of the third sintering can be any value between 2℃ / min, 4℃ / min, 6℃ / min, 8℃ / min or 2-8℃ / min, the endpoint temperature can be any value between 200℃, 250℃, 300℃, 350℃ or 200-350℃, and the time can be any value between 5h, 7h, 9h, 11h or 5h-11h.

[0200] It is important to note that if the third sintering temperature is too low, the boron-containing compounds may not be completely dehydrated, and the alumina with its small specific surface area may not be able to fully combine with boric acid. If the third sintering temperature is too high, the boron-containing compounds may over-melt, leading to a thicker coating layer and hindering the formation of Li.+ Diffusion, while surface Li + Accelerated precipitation leads to the loss of lattice oxygen, resulting in the formation of rock salt phase.

[0201] The third aspect provides a lithium-ion battery, including the aforementioned polycrystalline ultra-high nickel ternary cathode material.

[0202] The fourth aspect provides an electrical device including the aforementioned lithium-ion battery.

[0203] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0204] Example 1

[0205] This embodiment provides a polycrystalline ultra-high nickel ternary cathode material, comprising a core and a first coating layer and a second coating layer disposed on the surface of the core, wherein the chemical formula of the core is:

[0206] LiNi 0.9385 Co 0.029 Mn 0.027 Zr 0.001 Sr 0.001 Sb 0.001 Y 0.001 Al 0.001 Ta 0.0005 O2, wherein the core consists of a bulk region, a subsurface region, and a surface and grain boundary region from the inside out. The radius of the bulk region is 0.5 times the radius of the core. The subsurface region is located between the bulk region and the surface region. The diameter of the surface region is ≤50nm.

[0207] Cross-sectional SEM image of polycrystalline ultra-high nickel ternary cathode material Figure 1 As shown;

[0208] XPS etching pattern of Y element in polycrystalline ultra-high nickel ternary cathode material as shown in Figure Figure 2 As shown, Y element is uniformly doped from the surface to the bulk phase;

[0209] XPS etching pattern of Sb element in polycrystalline ultra-high nickel ternary cathode material as shown in Figure Figure 3 As shown, Sb is uniformly doped from the surface to the bulk phase.

[0210] XPS etching pattern of Al element in polycrystalline ultra-high nickel ternary cathode material as shown in Figure Figure 4 As shown, Al is uniformly doped from the surface to the bulk phase;

[0211] XPS etching pattern of Ta element in polycrystalline ultra-high nickel ternary cathode material as shown in Figure Figure 5 As shown, Ta is gradient-doped from the surface to the subsurface, and the peak intensity gradually decreases.

[0212] XPS etching pattern of Zr element in polycrystalline ultra-high nickel ternary cathode material as shown in Figure Figure 6 As shown, the Zr element content can be considered to gradually decrease from the material surface to the bulk phase.

[0213] XPS etching pattern of Sr element in polycrystalline ultra-high nickel ternary cathode material as shown in Figure Figure 7 As shown, Sr elements are mainly distributed on the surface of the material, and as the etching depth increases, the distribution of Sr elements inside is almost invisible.

[0214] Frontal SEM image of polycrystalline ultra-high nickel ternary cathode material Figure 8 As shown.

[0215] The first coating layer is a lithium-M'' multi-element oxide composite, wherein the M'' element is Sb, Al, and Co, and the thickness is 3 nm;

[0216] The second coating layer comprises a lithium-M''' oxide composite, wherein M''' is composed of B and Al, and has a thickness of 2 nm.

[0217] The second aspect of this embodiment provides a method for preparing a polycrystalline ultra-high nickel ternary cathode material, including:

[0218] S1: In a sintering environment with an oxygen concentration of 97.5%, the precursor Ni is... 0.944 Co 0.029 Mn 0.027 (OH)2, lithium hydroxide monohydrate, zirconium oxide, strontium oxide, antimony oxide, yttrium oxide, aluminum oxide, and tantalum oxide were dry-mixed uniformly in a molar ratio of 1:1.05:0.001:0.001:0.001:0.001:0.001:0.0005. After uniform mixing, the mixture was sintered once. The temperature was first increased to 500℃ at a rate of 1.5℃ / min and held for 4 hours. Then, the temperature was increased to 620℃ at a rate of 3℃ / min and held for 8 hours. Finally, the temperature was increased to 740℃ at a rate of 8℃ / min and held for 12 hours. After cooling, the mixture was sieved to obtain the first-sintered product.

[0219] S2: In a sintering environment with an oxygen concentration of 90.0%, the first-burned material is mixed with cobalt hydroxyoxide, alumina, and antimony oxide. The cobalt concentration in the cobalt hydroxyoxide is 6000 ppm, the aluminum concentration in the alumina is 260 ppm, and the antimony concentration in the antimony oxide is 835 ppm. The mixture is then subjected to a second sintering, specifically: the temperature is increased to 680℃ at a rate of 1.5℃ / min, held for 9 hours, cooled, and sieved to obtain the second-burned product.

[0220] S3: Wash the dicalcined product obtained in step S2 with low-temperature pure water containing additives, wherein the additive is NaAlO2 (concentration in water is 0.01mol / L), the mass ratio of low-temperature pure water containing additives to dicalcined product is 0.6:1, the temperature of low-temperature pure water is 5℃, the water washing stirring time is 2min, the centrifugation dehydration time is 30min, and then the material is dried under vacuum at 120℃ for 4h to obtain the washed material.

[0221] S4: In a sintering environment with an oxygen concentration of 90.0%, the water-washed material obtained in step S3 is mixed with boric acid and alumina (specific surface area of ​​40m²). 2 The mixture was prepared by dry homogenization, with boron concentration of 175 ppm in boric acid and aluminum concentration of 520 ppm in alumina. The mixture was heated to 295 °C at a rate of 5 °C / min, held for 8 hours, cooled, and sieved to obtain a polycrystalline ultra-high nickel ternary cathode material. The SEM images of this polycrystalline ultra-high nickel ternary cathode material are shown below. Figure 3 As shown.

[0222] Example 2

[0223] The difference from Example 1 is that in step S1, the precursor Ni is... 0.944 Co 0.029 Mn 0.027 (OH)2, lithium hydroxide monohydrate, zirconium oxide, strontium oxide, antimony oxide, magnesium oxide, calcium oxide, and titanium oxide are dry-mixed uniformly in a molar ratio of 1:1.05:0.001:0.001:0.001:0.001:0.001:0.001:0.0005.

[0224] The chemical formula of the kernel in this embodiment is:

[0225] LiNi 0.9385 Co 0.029 Mn 0.027 Zr 0.001 Sr 0.001 Sb 0.001 Mg 0.001 Ca 0.001 Ti 0.0005 O2.

[0226] Example 3

[0227] The difference from Example 1 is that in step S1, the precursor Ni is... 0.944 Co 0.029 Mn 0.027 (OH)2, lithium hydroxide monohydrate, tungsten oxide, molybdenum oxide, niobium oxide, magnesium oxide, calcium oxide, and titanium oxide are dry-mixed uniformly in a molar ratio of 1:1.05:0.001:0.001:0.001:0.001:0.001:0.001:0.0005.

[0228] The chemical formula of the kernel in this embodiment is:

[0229] LiNi 0.9385 Co 0.029 Mn 0.027 W 0.001 Mo 0.001 Nb 0.001 Mg 0.001 Ca 0.001 Ti 0.0005 O2.

[0230] Example 4

[0231] The difference from Example 1 is that the core is not doped with Sb.

[0232] Example 5

[0233] The difference from Example 1 is that the core is not doped with Al.

[0234] Example 6

[0235] The difference from Example 1 is that the core is not doped with Y.

[0236] Example 7

[0237] The difference from Example 1 is that the core is not doped with Ta.

[0238] Example 8

[0239] The difference from Example 1 is that the core is not doped with Zr.

[0240] Example 9

[0241] The difference from Example 1 is that the kernel is not doped with Sr.

[0242] Example 10

[0243] The difference from Example 1 is that the M'' element in the first coating layer does not have Al, but only Sb and Co.

[0244] Example 11

[0245] The difference from Example 1 is that the M'' element in the first coating layer does not have Sb, but only Al and Co.

[0246] Example 12

[0247] The difference from Example 1 is that the M'' element in the first coating layer does not contain Co, but only Al and Sb.

[0248] Example 13

[0249] The difference from Example 1 is that the M'' element in the second coating layer does not have B, but only A1.

[0250] Example 14

[0251] The difference from Example 1 is that the M'' element in the second coating layer does not have Al, but only B.

[0252] Example 15

[0253] The difference from Example 1 is that the M'' element in the first coating layer is Sb, Al, Co, Ti, W and P, and the thickness is 3nm;

[0254] The M''' element in the second coating layer is B, Al, W, and Ti.

[0255] In step S2 of the corresponding preparation method, a calcined material is mixed with cobalt hydroxyoxide, aluminum oxide, antimony oxide, titanium oxide, tungsten oxide, and lithium phosphate. The resulting mixture has a cobalt concentration of 5900 ppm in cobalt hydroxyoxide, an aluminum concentration of 250 ppm in aluminum oxide, an antimony concentration of 830 ppm in antimony oxide, a titanium concentration of 300 ppm in titanium oxide, a tungsten concentration of 396 ppm in tungsten oxide, and a phosphorus concentration of 134 ppm in lithium phosphate.

[0256] In step S4, the water-washed material obtained in step S3 is mixed with boric acid, alumina, lithium tungstate, and lithium titanate. The boron concentration in the boric acid is 171 ppm, the aluminum concentration in the alumina is 501 ppm, the tungsten concentration in the lithium tungstate is 702 ppm, and the titanium concentration in the lithium titanate is 520 ppm.

[0257] Comparative Example 1

[0258] The difference from Example 1 is that in step S1, the first sintering does not involve three-stage heating, but directly heats to 740°C at a rate of 8°C / min, holds for 12 hours, and then sieves after cooling.

[0259] The core doping element distribution of the polycrystalline ultra-high nickel ternary cathode material obtained in this comparative example is as follows:

[0260] Zr, Sr, Y, Sb, Al, and Ta are basically distributed at the interface and do not exhibit concentration gradient distribution.

[0261] Comparative Example 2

[0262] The difference from Example 1 is that in step S1, the precursor Ni is... 0.944 Co 0.029 Mn 0.027 (OH)2, lithium hydroxide monohydrate, zirconium oxide, strontium oxide, antimony oxide, yttrium oxide, aluminum oxide, and tantalum oxide are dry-mixed uniformly in a molar ratio of 1:1.05:0.025:0.001:0.001:0.001:0.001:0.005.

[0263] Comparative Example 3

[0264] The difference from Example 1 is that in step S2, a calcined material is mixed with cobalt hydroxyoxide, aluminum oxide, and antimony oxide, wherein the cobalt concentration in the cobalt hydroxyoxide in the resulting mixture is 12000 ppm, the aluminum concentration in the aluminum oxide is 2000 ppm, and the antimony concentration in the antimony oxide is 2000 ppm.

[0265] Comparative Example 4

[0266] The difference from Example 1 is that in step S4, the washed material is mixed with boric acid and alumina. In the resulting mixture, the boron concentration in the boric acid is 600 ppm and the aluminum concentration in the alumina is 2000 ppm.

[0267] Comparative Example 5

[0268] The difference from Example 1 is that in step S3, no additives are added during the water washing process, and only pure water is used for the water washing.

[0269] Comparative Example 6

[0270] The difference from Example 1 is that no first covering layer is provided.

[0271] Comparative Example 7

[0272] The difference from Example 1 is that no second covering layer is provided.

[0273] Comparative Example 8

[0274] The difference from Example 1 is that the order in which the first coating layer and the second coating layer are set is changed.

[0275] The core molecular formulas of the ternary cathode materials prepared in the above embodiments and comparative examples are shown in Table 2.

[0276] Table 2. Core molecular formula of cathode material

[0277]

[0278] The relevant parameters of the ternary cathode materials and coating layers prepared in the above embodiments and comparative examples are shown in Table 3.

[0279] Table 3. Relevant parameters of ternary cathode materials and coating layers.

[0280]

[0281] The ternary cathode materials prepared in the above embodiments and comparative examples were used to assemble electrode sheets and lithium-ion batteries, respectively. Specifically, the ternary cathode materials prepared in the above embodiments and comparative examples, the conductive agent SuperP, the binder polyvinylidene fluoride (PVDF), and N-methylpyrrolidone (NMP) were mixed and stirred evenly at a mass ratio of 90:5:5 to form a cathode slurry. This slurry was then coated onto a current collector aluminum foil, dried at 85°C, and rolled at room temperature until the areal density reached 3.4-3.6 g / cm³. 3 Then, the cells are punched and cut into φ14mm round pieces to form the positive electrode. Next, the coin cells are assembled in a glove box in the following order: negative electrode shell - nickel foam - lithium sheet - electrolyte - separator - electrolyte - positive electrode sheet - positive electrode shell. The electrolyte consists of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC), containing 1.0M LiPF6. The lithium sheet diameter is 18mm, the separator diameter is 22mm, and the positive and negative electrode shells are 24mm in size. The assembled coin cells are placed in the mold cavity of a hydraulic sealing machine and pressure >350kg / cm² is applied. 2 After sealing, remove the battery and let it stand (temperature: 23-27℃, time ≥3H) to obtain a sealed button cell battery.

[0282] The coin cells prepared in the above examples and comparative examples were subjected to electrochemical performance tests, including initial coulombic efficiency and cycle capacity retention tests. The specific test results are shown in Table 4.

[0283] The button cell charge-discharge cycle test was conducted at 25°C using a Blue Electric test cabinet to examine its charge-discharge cycle characteristics. First, the test was performed at a charge-discharge rate of 0.1C within a voltage range of 2.8V-4.3V. Specifically, the battery was charged at a constant current of 0.1C to 4.3V, then charged at a constant voltage of 4.3V to a cutoff current of 30uA. After a 5-minute rest, the battery was discharged at 0.1C to 0.8V, and the initial charge-discharge capacity was recorded. Then, the cycle test was performed at a charge-discharge rate of 1C. Specifically, the battery was charged at a constant current of 1C to 4.3V, then charged at a constant voltage of 4.3V to a cutoff current of 30uA. After a 5-minute rest, the battery was discharged at 1C to 2.8V, and rested for another 5 minutes. This cycle was repeated 100 times, and the charge-discharge capacity of the 100th cycle was recorded. The initial coulombic efficiency and the 100-cycle capacity retention rate were calculated using the following formulas:

[0284] Cycle capacity retention (%) = (100th cycle discharge capacity under 1C charge / discharge conditions / 1st cycle discharge capacity) × 100%.

[0285] In addition, the 0.1 C charge-discharge capacity tests of the batteries prepared in Example 1 and Comparative Example 1 are as follows: Figure 9 As shown, in Example 1, gradient elemental doping was achieved through gradient sintering, combined with double-layer coating modification and water washing process optimization, which realized the synergistic optimization of structure and interface, resulting in the material with the best electrochemical performance.

[0286] The capacity retention rate of the batteries prepared in Example 1 and Comparative Example 1 after 100 cycles at 1 C rate was tested as follows: Figure 10 As shown.

[0287] The schematic diagram of the 28-day storage-volume change of the batteries prepared in Example 1 and Comparative Example 1 at 70°C is shown below. Figure 11 As shown.

[0288] The schematic diagrams of the 28-day storage-capacity recovery rates of the batteries prepared in Example 1 and Comparative Example 1 at 70°C are shown below. Figure 12 As shown.

[0289] Table 4 Electrochemical Performance

[0290]

[0291] The specific analysis is as follows:

[0292] Compared to Example 1, Example 2 involved a substitution of the doping element; in Example 2, Mg... 2+ and Ca 2+ It can partially suppress cation mixing, Ti 4+ Enhanced lithium-ion diffusion, but the ionic radius of Mg / Ca is similar to that of Li. +The difference is small, but the stabilization effect is not as good as Y. 3+ And Al 3+ In addition, Mg 2+ and Ca 2+ The introduction of [a substance], while able to suppress cation mixing to some extent, [is related to] its interaction with Li. + radius mismatch (especially Ca) 2+ This leads to more significant lattice distortion, reducing the number of available lithium sites in the lithium layer or hindering lithium-ion migration pathways. Furthermore, Mg / Ca lacks electrochemical activity and cannot provide capacity, causing additional capacity loss. Therefore, its capacity and efficiency are lower than those of Example 1. However, since the Mg-O and Ca-O bond energies still contribute to overall structural stability, its performance (especially cycling and volume stability) is still significantly better than that of Comparative Example 1, which suffers from a porous structure due to sintering defects.

[0293] W in Example 3 6+ Mo 4+ High-valence elements can reduce oxygen vacancies, but multi-element doping may lead to uneven element distribution and poorer synergy than the original design. All performance parameters deteriorate slightly, which is reflected in capacity retention and high-temperature storage performance.

[0294] Example 4 (without Sb): Sb doping helps form Sb-O bonds, enhancing bulk stability; its absence exacerbates surface Li... + / Ni 2+ Mixed storage reduces initial efficiency and cycle stability, and also affects high-temperature storage performance.

[0295] Example 5 (without Al): Al 3+ It is a key dopant that can significantly reduce the risk of cation mixing and thermal runaway. Its absence leads to a comprehensive decline in capacity, efficiency, cycling and volume stability, and a significant increase in volume change rate.

[0296] Example 6 (without Y): Y 3+ Used to stabilize lattice oxygen, its absence slightly reduces the stability of the bulk structure, affecting capacity retention and also impacting high-temperature storage performance.

[0297] Example 7 (without Ta) and Example 8 (without Zr): Ta 5+ and Zr 4+ All are subsurface doped, which suppresses surface phase transitions (such as layered → rock salt phase) through strong bond energy. After the doping is removed, surface reconstruction is intensified, capacity retention and recovery rate decrease, and volume expansion increases.

[0298] Example 9 (without Sr): Sr 2+ Focusing on grain boundary strengthening, it inhibits microcrack propagation. Its absence leads to particle breakage during cycling, significantly increasing the rate of volume change and decreasing capacity retention.

[0299] Example 10 (First coating layer without Al): Al enhances the adhesion between the coating layer and the substrate. Without Al, the coating layer is prone to detachment, side reactions increase, and efficiency and high-temperature recovery rate decrease.

[0300] Example 11 (First coating layer without Sb): Sb helps form conductive Sb oxide, promoting electron migration. Its absence increases interfacial impedance, resulting in reduced capacity and efficiency.

[0301] Example 12 (first coating layer without Co): The role of Co is to directionally consume residual alkali, improve rate performance, and build a surface electronic conductive network. Without Co, the electrochemical performance and high-temperature storage performance of the material will decrease.

[0302] Example 13 (second coating layer without B) and Example 14 (without Al): B 3+ It helps form borate glasses and promotes Li + Conduction, Al 3+ The absence of island-like coatings reduces the material's high-temperature storage performance. When a single element is missing, another element can provide partial protection, thus the overall performance will decrease.

[0303] Example 15 (First coating layer increased with Ti, W, P; second coating layer increased with Ti, W): Due to the increase in the content of the inactive coating layer, the capacity decreased slightly. However, the multiple coating layers formed a more robust and stable composite structure on the material surface. Ti-based compounds (TiO2, Li4Ti5O) 12 It provides excellent mechanical stability, effectively suppresses the volume expansion and contraction of cathode particles during cycling, reduces the generation of microcracks, and the W-based compounds (WO3, Li2WO4) and Li3PO4 enhance the interfacial chemical stability, effectively prevent the electrolyte from corroding the cathode material, and significantly reduce the dissolution of transition metal ions and the loss of surface lattice oxygen. Therefore, the material performs better than Example 1 in terms of capacity retention and high-temperature storage performance.

[0304] Comparative Example 2 (Increased Zr Doping): Excessive Zr blocks lithium-ion channels, increases impedance, reduces capacity and efficiency, and increases volume change rate due to excessive rigidity.

[0305] Comparative Example 3 (first coating layer concentration too high) and Comparative Example 4 (second coating layer concentration too high): Excessive coating layer hinders lithium-ion diffusion and reduces capacity. The effect of Comparative Example 3 is more significant because the first coating layer is in direct contact with the substrate.

[0306] Comparative Example 5 (water washing without additives): Pure water cannot effectively remove surface residual alkali (Li2CO3 / LiOH), side reactions are aggravated, the initial efficiency, capacity retention rate and recovery rate decrease significantly, and the volume change rate increases significantly due to gas generation and particle expansion.

[0307] Comparative Example 6 (without the first coating layer) and Comparative Example 7 (without the second coating layer): The absence of the first coating layer leads to direct surface exposure, severe dissolution of transition metals and decomposition of electrolyte, resulting in overall performance degradation; the absence of the second coating layer weakens the outer layer protection, and the volume change rate and recovery rate decrease significantly.

[0308] Comparative Example 8 (Covering Layer Order Reversal): The original order (first coating layer is Sb-Co-Al, second is B-Al) optimized the interfacial energy barrier. After reversal, the inner B-Al layer has poor matching with the matrix, increasing impedance and decreasing cycle and volume stability.

[0309] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 therein. Such 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 this application.

[0310] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A polycrystalline ultra-high nickel ternary cathode material, characterized in that, The core and a first coating layer and a second coating layer arranged in sequence on the surface of the core; The chemical formula of the core is LiNi X M y M' Z O2, wherein 0.8≤x≤0.98, 0.02≤y≤0.15, 0.001≤z≤0.06, x+y+z=1; M includes at least two of Co, Mn, Al, M' includes Zr, Sr, Y, Sb, Al and Ta. The core comprises, in sequence from the inside out, a bulk region, a subsurface region and a surface region, the radius of the bulk region is 0.3-0.9 of the radius of the core, the subsurface region is between the bulk region and the surface region, and the diameter of the surface region is ≤50nm; The doping elements of the bulk region include Y, Sb and Al; The doping elements of the subsurface region include Ta and Zr; The surface region includes Sr and Zr; The first coating layer includes a lithium-M'' multi-element oxide compound, and M'' includes Sb, Al and Co; The second coating layer includes a lithium-M''' oxide compound, and M''' includes B and Al.

2. The polycrystalline ultra-high nickel ternary cathode material of claim 1, wherein, At least one of the following conditions is met: (1) the chemical formula of the core is: LiNi X M y Y 0.0001-0.01 Sb 0.0001-0.01 Al 0.0001-0.01 Ta 0.0001-0.005 Sr 0.0001-0.01 Zr 0.0001-0.01 O2; (2) the concentration of Sb in the first coating layer is 300-1200ppm; (3) the concentration of Co in the first coating layer is 3000-8000ppm; (4) the concentration of Al in the first coating layer is 100-600ppm; (5) the concentration of B in the second coating layer is 100-300ppm; (6) the concentration of Al in the second coating layer is 200-800ppm. 3.The polycrystalline ultra-high nickel ternary cathode material of claim 1, wherein, At least one of the following conditions is met: (1) the thickness of the first coating layer is 0.5-10nm; (2) the thickness of the second coating layer is 0.5-6.5nm; (3) the aspect ratio of the primary particles of the polycrystalline ultra-high nickel ternary positive electrode material is ≤1.8; (4) the roundness of the primary particles of the polycrystalline ultra-high nickel ternary positive electrode material is ≤1.0; (5) the porosity of the secondary particles of the polycrystalline ultra-high nickel ternary positive electrode material is ≤3%; (6) the D50 of the polycrystalline ultra-high nickel ternary positive electrode material is 3-18μm.

4. A method for preparing the polycrystalline ultra-high nickel ternary cathode material according to any one of claims 1-3, characterized in that, It comprises: The precursor Ni a M b (OH)2, a lithium source, and a compound containing M' are mixed to obtain a first mixture. The first mixture is sintered under an oxygen-containing condition to obtain a first sintered material. The second mixture is obtained by second mixing the first sintered material and a M''-containing compound, and the polycrystalline ultra-high nickel ternary positive electrode material is obtained by second sintering the second mixture; The water-washed material is obtained by water washing the second sintered material; The third mixture is obtained by third mixing the water-washed material and a M'''-containing compound, and the polycrystalline ultra-high nickel ternary positive electrode material is obtained by third sintering the third mixture.

5. The method of claim 4, wherein the method further comprises the step of: At least one of the following conditions is met: ​ (1) the M'-containing compound includes one or more of oxides, hydroxides and carbonates containing M'; (2) the lithium source includes one or more of lithium hydroxide, lithium carbonate, lithium acetate, lithium fluoride, lithium nitrate and lithium oxalate and hydrates thereof; (3) the M''-containing compound includes one or more of oxides, hydroxides and carbonates containing M''; (4) the M'''-containing compound includes boric acid and aluminum oxide; (5) when the water washing is performed, the additive used includes sodium metaaluminate and / or sodium metasilicate; The concentration of the additive is 0.01-0.1mol / L; (6) the oxygen content under the aerobic condition is ≥80%; (7) the precursor Ni a M b the molar amounts of the (OH)2, Li in the lithium source, and M' in the M'-containing compound are 1 : 1.03-1.08：0.001-0.06； (8) the concentration of M'' in the second mixture is 3400-9800ppm; (9) the concentration of M''' in the third mixture is 300-1100 ppm.

6. The method of claim 5, wherein the method further comprises the step of: The specific surface area of the alumina is 20-80 m 2 / g. ​ 7. The method of claim 4, wherein the method further comprises the step of: At least one of the following conditions is met: ​ (1) the first sintering comprises fourth sintering, fifth sintering and sixth sintering performed in sequence; the fourth sintering has a temperature rising rate of 1-2 ℃ / min, an end point temperature of 450-550 ℃, and a holding time of 2-7 h; the fifth sintering has a temperature rising rate of 0.5-4 ℃ / min, an end point temperature of 550-670 ℃, and a holding time of 8-20 h; the sixth sintering has a temperature rising rate of 5-10 ℃ / min, an end point temperature of 670-790 ℃, and a holding time of 10-18 h; (2) the second sintering has a temperature rising rate of 1-2 ℃ / min, an end point temperature of 600-700 ℃, and a time of 6 h-15 h; (3) the third sintering has a temperature rising rate of 2-8 ℃ / min, an end point temperature of 200-350 ℃, and a time of 5 h-11 h.

8. A lithium-ion battery, characterized by, The polycrystalline ultra-high nickel ternary positive electrode material according to any one of claims 1-3.

9. An electric device, characterized by The lithium ion battery according to claim 8.

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