A modified lithium cobaltate material, a preparation method and use thereof

Abstract

The application belongs to the technical field of batteries, and provides a modified lithium cobalt oxide material, a preparation method and application thereof. The modified lithium cobalt oxide material comprises a doped lithium cobalt oxide core and an amorphous fast ion conductor coating layer covering the doped lithium cobalt oxide core. The tap density of the modified lithium cobalt oxide material is greater than or equal to 2.9 g / cm 3 , the specific surface area BET is 3.2 m 2 / g~3.8 m 2 / g. The modified lithium cobalt oxide material has high tap density, which is beneficial to fully improve the volume energy density, and has good processing performance, low internal resistance and good cycle stability. In addition, the modified lithium cobalt oxide material has high specific surface area, which is beneficial to fully improve the rate fast charging performance, low temperature performance and electrolyte wettability. At the same time, the core doping and the outer amorphous fast ion conductor coating can synergistically improve the structural stability and electrolyte corrosion, thereby meeting the high-performance application under high-voltage conditions.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a modified lithium cobalt oxide material, its preparation method, and its uses. Background Technology

[0002] With the rapid development of new energy technologies, lithium-ion batteries, as efficient and environmentally friendly electrochemical energy storage devices, have always had a focus on the research and development of cathode materials. Currently, mainstream cathode materials can be classified into three main categories based on their crystal structure: layered (such as ternary materials and lithium cobalt oxide), spinel-type (such as lithium manganese oxide), and olivine-type (such as lithium iron phosphate). Among them, lithium cobalt oxide (LiCoO2) is the earliest commercialized and most widely used cathode material. Due to its mature preparation process, stable cycle performance, good thermal stability, and high theoretical density and theoretical compaction density, it can impart excellent volumetric energy density to batteries. Therefore, it has long dominated the consumer electronics field and is widely used in smartphones, laptops, and mobile terminals.

[0003] However, lithium cobalt oxide still faces several challenges in practical applications. First, its irregular particle morphology, wide particle size distribution, and high content of fine powder result in a tap density (TD) that typically only reaches 2.3 g / cm³. 3 ~2.6g / cm 3 This insufficient compaction density directly affects the battery's energy density, limiting its further optimization in high-performance applications. To meet market demands for higher energy density, increasing the operating voltage of lithium cobalt oxide has become a crucial technological approach. Currently, the operating voltage of lithium cobalt oxide has increased from the traditional 4.2V to 4.48V or even 4.6V (vs. Li). + / Li), but this brings with it the problem of high-voltage stability. Under high voltage conditions, excessive delithiation of the lithium cobalt oxide surface layer triggers an irreversible phase transition extending from the surface to the particle interior. In particular, traditional high-TD materials, due to their dense interior and difficulty in strain release, are more prone to structural degradation (such as oxygen release and phase transition) and interfacial side reactions, leading to shortened cycle life and decreased safety performance. On the other hand, the high-valence Co on the surface of lithium cobalt oxide under high voltage... 4+ It has extremely high oxidizing activity and will accelerate the oxidative decomposition of the electrolyte to generate HF, which will damage the surface structure of the material.

[0004] Furthermore, in terms of manufacturing processes, increasing the sintering temperature helps increase the primary particle size and tap density, but this reduces the specific surface area (BET), leading to blockage of lithium-ion entry and exit channels and reducing the contact area between the electrode material and the electrolyte, thus affecting rate performance. Conversely, lowering the sintering temperature to maintain a high BET may result in excessively small primary particles, affecting both tap density and compaction density. This process contradiction makes it difficult to simultaneously achieve high voltage stability, rate performance, and cost control when optimizing lithium cobalt oxide performance.

[0005] Therefore, how to significantly improve the structural and interfacial stability of lithium cobalt oxide under high voltage conditions while maintaining its high volumetric energy density advantage has become a key problem that urgently needs to be solved in the field of cathode materials. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of this invention is to provide a modified lithium cobalt oxide material, its preparation method and uses, wherein the modified lithium cobalt oxide material comprises a doped lithium cobalt oxide core and an amorphous fast ion conductor coating layer covering the doped lithium cobalt oxide core; the tap density of the modified lithium cobalt oxide material is greater than or equal to 2.9 g / cm³. 3 The specific surface area (BET) is 3.2 m². 2 / g~3.8m 2 / g. This modified lithium cobalt oxide material has a high tap density, which is beneficial for significantly improving the volumetric energy density. It also has good processing performance, low internal resistance, and good cycle stability. Furthermore, it has a high specific surface area, which is beneficial for significantly improving the fast-charging performance, low-temperature performance, and electrolyte wettability. At the same time, the core doping and the outer amorphous fast ion conductor coating can synergistically improve structural stability and electrolyte erosion, thereby meeting the requirements for high-performance applications under high voltage conditions.

[0007] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a modified lithium cobalt oxide material, comprising a doped lithium cobalt oxide core, wherein the doping element in the doped lithium cobalt oxide core includes at least one selected from aluminum, magnesium, or zirconium; and further comprising an amorphous fast-ion conductor coating layer covering the doped lithium cobalt oxide core; the tap density of the modified lithium cobalt oxide material is greater than or equal to 2.9 g / cm³. 3 The specific surface area (BET) is 3.2 m². 2 / g~3.8m 2 / g.

[0008] The modified lithium cobalt oxide material provided by this invention has high tap density, which is beneficial for significantly improving volumetric energy density. It also exhibits good processing performance, low internal resistance, and good cycle stability. Furthermore, it has a high specific surface area, which is beneficial for significantly improving fast-charging performance, low-temperature performance, and electrolyte wettability. Simultaneously, doping the core with aluminum and other materials can improve structural stability, cycle life, thermal stability and safety, inhibit cobalt dissolution, and reduce costs. The outer coating of a fast-ion conductor provides ion transport channels, improving the battery's charge transfer kinetics and significantly reducing Li-O2 emissions. + The migration energy barrier promotes Li + Rapid migration of [the substance] improves the electrochemical kinetics performance of the battery. On the other hand, the dense shell coating on the surface effectively hinders the interaction between the electrolyte and Co. 4+This reduces contact with the electrode material, thereby decreasing the oxidative decomposition of the electrolyte and the chemical corrosion of the electrode material surface under high voltage. It effectively mitigates material peeling and cracking caused by volume changes during charging and discharging.

[0009] The tap density of the modified lithium cobalt oxide material described in this invention is greater than or equal to 2.9 g / cm³. 3 For example, it could be 2.9 g / cm³ 3 3.0g / cm 3 3.1g / cm 3 3.3g / cm 3 Specific surface area (BET) is 3.2 m². 2 / g~3.8m 2 / g, for example, could be 3.2m 2 / g, 3.3m 2 / g, 3.4m 2 / g, 3.5m 2 / g, 3.6m 2 / g, 3.7m 2 / g or 3.8m 2 / g etc.

[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0011] As a preferred embodiment of the present invention, the secondary particles of the modified lithium cobalt oxide material are spherical.

[0012] Preferably, the doping amount of the dopant element in the doped lithium cobalt oxide core is 1000ppm to 10000ppm, for example, it can be 1000ppm, 2000ppm, 3000ppm, 4000ppm, 5000ppm, 8000ppm, 9000ppm, or 10000ppm. The doping amount can be obtained by elemental analysis of the core using ICP (inductively coupled plasma) testing.

[0013] Preferably, the amorphous fast ion conductor includes a layer comprising at least one of lithium phosphate (Li3PO4), lithium zirconate (Li2ZrO3), or niobium oxalate.

[0014] In a second aspect, the present invention provides a method for preparing the modified lithium cobalt oxide material provided in the first aspect, the method comprising: Solution A was prepared by mixing cobalt salt with doped element salt; solution B was prepared by mixing precipitant; and solution C was prepared by mixing fast ion conductor salt. Solution A and solution B are mixed in parallel flow to carry out a first reaction and generate a first reactant. Stop feeding solution A, and simultaneously feed solution B and solution C in a co-current flow to carry out a second reaction, generating a second reactant and obtaining a slurry; The slurry was subjected to solid-liquid separation, pulping and washing, and drying in sequence, followed by a first calcination to obtain the precursor. The precursor is mixed with a lithium source and subjected to a second calcination to obtain a modified lithium cobalt oxide material.

[0015] The preparation method provided by this invention maintains the structure and performance of the cathode material by uniformly doping elements during the co-precipitation process. In the first reaction, a high flow rate can be used to suppress nucleation and promote epitaxial growth, preparing a spherical precursor with large primary particles and uniform stacking density, thereby obtaining a higher shrinkage rate and a denser final product in subsequent sintering. Furthermore, the rapid growth results in a porous product surface, and the primary particles melt and separate into a dendritic structure after calcination, which is beneficial for achieving a high specific surface area. In the second reaction, i.e., during the preparation of the coating layer, the feed of solution A is stopped, making the coating layer a pure-phase fast-ion shell. Since this shell has high density and a reduced ion transport rate, it is preferred to control it to be a relatively thin shell. Moreover, the fast-ion conductor will migrate and diffuse into the inner layer during subsequent calcination, leading to the expansion of the cross-sectional shell-like structure.

[0016] As a preferred embodiment of the present invention, the concentration of cobalt in solution A is 100 g / L to 150 g / L, for example, it can be 100 g / L, 110 g / L, 120 g / L, 130 g / L, 140 g / L or 150 g / L; the concentration of dopant is 1 g / L to 2 g / L, for example, it can be 1 g / L, 1.1 g / L, 1.3 g / L, 1.5 g / L, 1.8 g / L or 2 g / L.

[0017] Preferably, the dopant salt includes at least one of the chloride, sulfate, or nitrate salts of the dopant element; the dopant element includes at least one of aluminum, magnesium, or zirconium. The present invention preferably employs multi-element doping, which can better improve the structure and performance of the cathode material.

[0018] Preferably, the concentration of the precipitant in solution B is 200 g / L to 300 g / L, for example, it can be 200 g / L, 210 g / L, 220 g / L, 250 g / L, 280 g / L or 300 g / L, etc.

[0019] Preferably, the precipitant comprises ammonium bicarbonate.

[0020] Preferably, the concentration of the fast ion conductor salt in solution C is 0.1 mol / L to 2 mol / L, for example, it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.3 mol / L, 1.5 mol / L, 1.8 mol / L or 2 mol / L, etc.

[0021] Preferably, the fast ion conductor salt includes at least one of lithium phosphate, lithium zirconate, or niobium oxalate.

[0022] As a preferred embodiment of the present invention, the preparation method includes: preparing the precipitant into a base solution, wherein the concentration of the precipitant in the base solution is 10 g / L to 30 g / L, for example, it can be 10 g / L, 13 g / L, 15 g / L, 20 g / L, 22 g / L, 25 g / L, 28 g / L, or 30 g / L; and mixing the solution A and the solution B in parallel flow into the base solution. Preferably, the volumetric flow rate of solution A is 70 L / h to 100 L / h, for example, it can be 70 L / h, 73 L / h, 75 L / h, 78 L / h, 80 L / h, 83 L / h, 85 L / h, 88 L / h, 90 L / h, 95 L / h, or 100 L / h. The growth rate of the first reactant is 0.15 μm / h to 0.20 μm / h, for example, it can be 0.15 μm / h, 0.16 μm / h, 0.17 μm / h, 0.18 μm / h, 0.19 μm / h, or 0.20 μm / h. The volumetric flow rate of the present invention is relative to 1 m 3 Calculation of the volume of the reaction vessel.

[0023] Preferably, the volumetric flow rate ratio of solution A to solution B is 1:(1~4), for example, it can be 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4, etc., preferably 1:(1~2).

[0024] In this invention, by controlling a high feed rate, the primary particles do not have enough time to align and agglomerate before settling onto the seed nucleus, forming a relatively loose, uniform, amorphous structure. This allows for significant shrinkage during subsequent calcination, increasing the tap density. In other words, a high feed rate helps suppress nucleation and promotes epitaxial growth, resulting in a spherical precursor with large, uniformly stacked primary particles. This spherical precursor can achieve a higher shrinkage rate and a denser final product during subsequent sintering. Alternatively, this invention employs an extremely high feed flow rate, maintaining a high and stable apparent supersaturation level within the reactor per unit time. This facilitates rapid polymerization into large primary particles, increasing the growth rate of the first reactant and shortening the reaction process.

[0025] Preferably, the pH value of the first reaction is 7.0~8.0, for example, it can be 7.0, 7.1, 7.3, 7.5, 7.8 or 8.0, preferably 7.0~7.5; the temperature is 25℃~35℃, for example, it can be 25℃, 28℃, 30℃, 32℃ or 35℃, preferably 28℃~32℃; the stirring speed is 80rpm~200rpm.

[0026] In this invention, the first reaction is carried out at a low temperature, which enhances the thermodynamic driving force of the crystallization reaction (high supersaturation), but the kinetics (diffusion and surface reaction rate) are relatively slow. This is beneficial to further suppress the instantaneous generation of a large number of fine crystal nuclei, and forces the reactants to undergo epitaxial growth on the surface of existing crystal nuclei / particles to form large primary grains.

[0027] As a preferred technical solution of the present invention, the preparation method further includes: after the average particle size of the first reactant is reduced to 10μm~19μm, for example, it can be 10μm, 11μm, 13μm, 15μm, 16μm, 18μm or 19μm, etc., the temperature is then increased to the temperature required for the second reaction, and the solution C is then mixed in parallel flow. Preferably, the heating rate is 1℃ / min to 3℃ / min, for example, it can be 1℃ / min, 2℃ / min or 3℃ / min, etc.

[0028] Preferably, the temperature of the second reaction is 45℃~60℃, for example, 45℃, 48℃, 50℃, 55℃ or 60℃, preferably 46℃~50℃; the stirring rate is 20rpm~100rpm, for example, 20rpm, 30rpm, 50rpm, 80rpm or 100rpm. In the second reaction, appropriately increasing the temperature is beneficial to increasing the elemental crystallinity of the corresponding part of the coating layer, thereby further improving the density.

[0029] Preferably, the volumetric flow rate of solution C is 1 / 6 to 1 / 10 of the volumetric flow rate of solution A in the first reaction, for example, it can be 1 / 6, 1 / 7, 1 / 8, 1 / 9 or 1 / 10, etc.

[0030] Preferably, the second reaction time is 4h to 10h, for example, it can be 2h, 3h, 5h, 8h or 10h.

[0031] As a preferred technical solution of the present invention, the drying temperature is 60℃~90℃, for example, it can be 60℃, 65℃, 70℃, 80℃, 85℃ or 90℃, etc.

[0032] Preferably, the temperature of the first calcination is 650℃~700℃, for example, it can be 650℃, 660℃, 670℃, 680℃, 690℃ or 700℃, etc.; the heating rate is 5℃ / min~8℃ / min, for example, it can be 5℃ / min, 6℃ / min, 7℃ / min or 8℃ / min, etc.

[0033] As a preferred embodiment of the present invention, the lithium source includes lithium hydroxide.

[0034] Preferably, the molar ratio of the precursor to the lithium source is 1:(1.0~1.1), for example, it can be 1:1.00, 1:1.03, 1:1.05, 1:1.08 or 1:1.10, etc.

[0035] Preferably, the second calcination temperature is 700℃~900℃, for example, 700℃, 750℃, 800℃, 850℃ or 900℃; the heating rate is 1℃ / min~3℃ / min, for example, 1℃ / min, 2℃ / min or 3℃ / min; and the time is 8h~14h, for example, 8h, 9h, 10h, 11h, 12h, 13h or 14h.

[0036] Thirdly, the present invention provides a positive electrode sheet containing the modified lithium cobalt oxide material described in the first aspect, or containing the modified lithium cobalt oxide material obtained by the preparation method described in the second aspect.

[0037] Fourthly, the present invention provides a battery comprising the positive electrode sheet described in the third aspect.

[0038] It should be noted that, due to space limitations and to avoid redundancy, this invention does not exhaustively list all point values ​​within the above numerical range, but it is not limited to the listed values ​​either; other unlisted values ​​within the above numerical range are also applicable.

[0039] Compared with existing technical solutions, the present invention has at least the following beneficial effects: The modified lithium cobalt oxide material provided by this invention possesses high tap density, which is beneficial for significantly improving volumetric energy density. It also exhibits good processing performance, low internal resistance, and good cycle stability. Furthermore, it has a high specific surface area, which is beneficial for significantly improving fast-charging performance, low-temperature performance, and electrolyte wettability. Simultaneously, doping the core with aluminum and other materials can improve structural stability, cycle life, thermal stability and safety, suppress cobalt dissolution, and reduce costs. The outer coating of fast-ion conductors can suppress side reactions between the lithium cobalt oxide surface and the electrolyte, improve battery charge transfer kinetics, and significantly reduce Li-O2 levels. + The migration energy barrier promotes Li + Rapid migration improves the electrochemical kinetics performance of the battery. Attached Figure Description

[0040] Figure 1 This is a SEM image of the cobalt oxide precursor obtained in Example 1.

[0041] Figure 2 This is a magnified SEM image of the cobalt oxide precursor obtained in Example 1.

[0042] Figure 3 This is a cross-sectional SEM image of the cobalt oxide precursor obtained in Example 1. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0044] The scope of this invention can be defined by lower and upper limits. The selected lower and upper limits define the boundaries of a specific range. The range defined in this way can be defined by the inclusion or exclusion of endpoints. Any endpoint can be independently selected for inclusion or exclusion, and all lower and upper limits can be arbitrarily combined to form new ranges. That is, any lower limit can be combined with any upper limit to form an effective range. For example, if the ranges of 60~120 and 80~110 are listed for specific parameters, it should be understood that the ranges of 60~110 and 80~120 also fall within the scope of this invention. In addition, if the minimum range values ​​1 and 2 are listed, and the maximum range values ​​3, 4 and 5 are also listed, then all ranges of 1~3, 1~4, 1~5, 2~3, 2~4 and 2~5 fall within the scope of this invention. In this invention, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between 0 and 5 have been fully listed in this document, and "0~5" is only a shortened representation of this set of numerical combinations. When a parameter is expressed as an integer ≥2, it is equivalent to listing positive integers that meet the requirements, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, etc. When a parameter is expressed as an integer selected from "2~10", it is equivalent to listing any integer among 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0045] In this invention, "a combination of at least two" refers to a quantity greater than or equal to 2 unless otherwise specified. For example, "any one or a combination of at least two" means that any one of the listed items can be selected, or a combination of at least two of the listed items formed in a manner that does not conflict and enables the implementation of this invention. In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" cover any one of two or more related listed items, as well as any and all combinations of the related listed items. The arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" means a set consisting of A, B, and combinations of A and B, where "containing A and / or B" can be understood, depending on the context of the statement, as containing A, containing B, or simultaneously containing both A and B. In this invention, "optional" means that the corresponding feature, component, step or solution is not necessary, that is, it is selected from either "with" or "without". If there are multiple "optional" limitations in a technical solution, unless otherwise specified and there is no technical conflict or mutual constraint, each "optional" limitation is independent and does not affect the others.

[0046] In this invention, technical features or solutions described using open-ended terms such as "comprising" or "including" do not exclude additional non-conflicting elements beyond the listed elements unless otherwise specified. They are considered to disclose both closed-ended features or solutions consisting solely of the listed elements and open-ended features or solutions that may include additional non-conflicting elements beyond the listed elements. For example, if A includes a1, a2, and a3, unless otherwise specified, this means that A can consist only of a1, a2, and a3, or it can include other non-conflicting elements based on a1, a2, and a3. This corresponds to the disclosure of technical solutions such as "A consists of a1, a2, and a3," "A is selected from a1, a2, and a3," and "A not only includes a1, a2, and a3, but may also include other non-conflicting elements." All embodiments and optional embodiments of this invention, unless otherwise specified and without technical conflict, can be combined to form new technical solutions, and such combinations fall within the scope of this invention. The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various locations throughout the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this invention can be combined with other embodiments that do not conflict with the technology. The ordinal numbers "first," "second," "third," and "fourth," etc., used in the expressions "first aspect," "second aspect," "third aspect," and "fourth aspect" in this invention are for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly specifying the importance or quantity of the indicated technical features. They serve only as a non-exhaustive enumeration and do not constitute a closed limitation on quantity.

[0047] In this invention, the order in which the steps are written in the methods described in the various embodiments does not imply a strict execution order. The actual execution order of each step should be determined based on its function and possible internal logic. Unless otherwise specified, all steps of this invention can be executed in the order they are written, or in any order without technical conflict. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) executed sequentially, or it may include steps (b) and (a) executed sequentially. If the method also includes step (c), then step (c) can be added to the method in any conflict-free order, including but not limited to the execution order of steps (a), (b), and (c), steps (a), (c), and (b), steps (c), (a), and (b), etc.

[0048] Example 1 This embodiment provides a modified lithium cobalt oxide material, comprising a doped lithium cobalt oxide core, wherein the doping element in the doped lithium cobalt oxide core includes at least one of aluminum, magnesium, or zirconium; and further comprising an amorphous fast ion conductor coating layer covering the doped lithium cobalt oxide core; the preparation method is as follows: S1. Prepare solution A containing 100 g / L cobalt sulfate and 1 g / L aluminum sulfate; prepare solution B containing 200 g / L ammonium bicarbonate; prepare solution C containing 1 mol / L niobium oxalate, a fast ion conductor. S2, First, in the reaction vessel (volume 1m³) 3 Ammonium bicarbonate and water were added to prepare a base solution with a concentration of 12 g / L. Then, solutions A and B were introduced at a volume flow rate ratio of 1:2, with a volume flow rate of 80 L / h for solution A and a stirring speed of 180 rpm to carry out the first reaction. The pH value of the reaction system was controlled at 7.3 and the temperature at 30℃ to generate the first reactant, and the growth rate of the first reactant was controlled at 0.15 μm / h. S3. In step S2, when the first reactant reacts to an average particle size of 19 μm, the volumetric flow rates of solutions A and B remain unchanged. The temperature is gradually increased to 48°C at a rate of 2°C / min. After reaching the desired temperature, solution C is added to generate the second reactant. The volumetric flow rate of solution C is controlled to be 1 / 8 of the volumetric flow rate of solution A in the first reaction. The growth rate of the second reactant is controlled to be 0.01 μm / h. The reaction is carried out for 8 hours to obtain the slurry. S4. The slurry obtained in step S3 is subjected to solid-liquid separation, followed by pulping and washing, then dried in a drying oven at 80°C, and then calcined in a rotary kiln at 700°C for 1 hour to obtain cobalt oxide precursor, with a heating rate of 5°C / min.

[0049] S5. The oxide precursor obtained in step S4 is mixed with lithium hydroxide source at a molar ratio of 1:1.1, and then the temperature is increased at a rate of 2℃ / min. The mixture is then calcined at 700℃ for 8 hours to obtain modified lithium cobalt oxide material.

[0050] Figure 1 , Figure 2 and Figure 3 The image shows an SEM test image of the cobalt oxide precursor obtained in step S4 of the embodiment. As can be seen from the image, the cobalt oxide precursor is a spherical particle with high sphericity, uniform particle size, and loose surface. It also has a coating layer that is significantly different from the inner layer. Furthermore, due to the migration and diffusion of fast ion conductors into the inner layer during subsequent calcination, the shell-like structure in the cross-sectional image expands.

[0051] Example 2 The difference from Example 1 is that aluminum sulfate in step S1 is replaced with magnesium sulfate, and the fast ion conductor salt niobium oxalate is replaced with lithium zirconate. Apart from the above, the other conditions are exactly the same as in Example 1.

[0052] Example 3 The difference from Example 1 is that aluminum sulfate in step S1 is replaced with zirconium sulfate, and the fast ion conductor salt niobium oxalate is replaced with lithium phosphate. Apart from the above, the other conditions are exactly the same as in Example 1.

[0053] Example 4 The difference from Example 1 is that in step S2, the volumetric flow rate of solution A is adjusted so that the growth rate of the first reactant changes from 0.15 μm / h to 0.08 μm / h. Apart from the above, the other conditions are exactly the same as in Example 1.

[0054] Example 5 The difference from Example 1 is that in step S2, the volumetric flow rate of solution A is adjusted so that the growth rate of the first reactant changes from 0.15 μm / h to 0.3 μm / h. Apart from the above, the other conditions are exactly the same as in Example 1.

[0055] Example 6 The difference from Example 1 is that in step S3, the volumetric flow rate of solution C is adjusted from 1 / 8 to 1 / 4 of the volumetric flow rate of solution A in the first reaction, and the growth rate of the second reactant is controlled at 0.02 μm / h. Apart from the above, the other conditions are exactly the same as in Example 1.

[0056] Example 7 The difference from Example 1 is that in step S3, the volumetric flow rate of solution C is adjusted from 1 / 8 to 1 / 14 of the volumetric flow rate of solution A in the first reaction, and the growth rate of the second reactant is controlled at 0.005 μm / h. Apart from the above, the other conditions are exactly the same as in Example 1.

[0057] Example 8 The difference from Example 1 is that in step S3, the duration of the second reaction is reduced from 8 hours to 1 hour. Apart from the above, the other conditions are exactly the same as in Example 1.

[0058] Example 9 The difference from Example 1 is that in step S3, the duration of the second reaction is adjusted from 8 hours to 15 hours. Apart from the above, the other conditions are exactly the same as in Example 1.

[0059] Comparative Example 1 The difference from Example 1 is that aluminum sulfate is not used, that is, no doping is performed. Apart from the above, the other conditions are exactly the same as those in Example 1.

[0060] Comparative Example 2 The difference from Example 1 is that the fast ion conductor niobium oxalate is not used, i.e., no coating is performed. Apart from the above, the other conditions are exactly the same as those in Example 1.

[0061] Characterization and testing: 1) Doping amount test: The elemental doping amount is measured by using ICP-AES (inductively coupled plasma atomic emission spectrometry) on the prepared material.

[0062] 2) Tap density test: Tap density (TD) was measured according to GB / T 21354-2008. 3) Specific surface area BET test: BET is measured by a specific surface area analyzer according to GB / T 13390-2008.

[0063] 4) Electrochemical performance testing: The lithium cobalt oxide material obtained in the examples and comparative examples was used as the positive electrode material. Conductive carbon black SP and polyvinylidene fluoride PVDF (HSV900) were added and mixed at a mass ratio of 90:5:5. N-methylpyrrolidone was used as the solvent. The mixture was stirred to form a slurry. The slurry was then uniformly coated onto aluminum foil using a doctor blade with a coating gap of 100 μm. After coating, the foil was first dried by blowing air, then rolled and cut into circular electrode sheets. After vacuum drying at 120°C, the electrode sheets were weighed to obtain the positive electrode sheet of the button half-cell. The negative electrode was a lithium metal sheet, the separator was a PP microporous membrane, and the electrolyte was a basic lithium battery electrolyte. The positive electrode sheet, lithium metal sheet, separator, and electrolyte were assembled to obtain a button cell. Then, the positive electrode sheet, lithium metal sheet, separator, and electrolyte were assembled to form a CR2032 button cell, and the following tests were performed: The electrochemical performance of the CR2032 coin cell was tested under the following conditions: using a battery testing system, the lithium-ion battery was charged and discharged at 0.5C (1C=200mAh / g) at 25°C within a voltage range of 2V to 4.65V. The initial capacity at 0.5C and the capacity retention rate after 100 cycles were obtained.

[0064] The test results are shown in Tables 1 and 2.

[0065] Table 1 As can be seen from Table 1: The modified lithium cobalt oxide material provided by this invention possesses high tap density, which is beneficial for significantly improving volumetric energy density. It also exhibits good processing performance, low internal resistance, and good cycle stability. Furthermore, it has a high specific surface area, which is beneficial for significantly improving fast-charging performance, low-temperature performance, and electrolyte wettability. Simultaneously, doping the core with aluminum and other materials can improve structural stability, cycle life, thermal stability and safety, suppress cobalt dissolution, and reduce costs. The outer coating of fast-ion conductors can suppress side reactions between the lithium cobalt oxide surface and the electrolyte, improve battery charge transfer kinetics, and significantly reduce Li-O2 levels. + The migration energy barrier promotes Li + Rapid migration improves the electrochemical kinetics performance of the battery.

[0066] Comparing Examples 1 and 4, the reduced growth rate in step S2 resulted in higher internal crystallinity and smaller primary grains, leading to a lower shrinkage rate and lower TD during subsequent calcination. In contrast, Example 5 had a higher growth rate in step S2, resulting in higher primary particle disorder and coarser grains. After calcination, the primary particles adhered together, resulting in a lower BET, reduced Li transport channels, and decreased capacity.

[0067] Comparing Example 1 and Example 6, in Example 6, increasing the flow rate of solution C in step S3 leads to excessively rapid shell growth and low density, and the shell thickness results in a higher BET and lower capacity after calcination; while in Example 7, the flow rate of solution C in step S3 is too low, resulting in a dense shell and poor circulation performance.

[0068] Comparing Examples 1 and 8, in Example 8, the second reaction time is shortened in step S3, resulting in a thinner shell that provides insufficient protection for the material under high voltage and poor cycle performance. In Example 9, the second reaction time is too long, the shell is too thick, reducing the material capacity and affecting rate performance.

[0069] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0070] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0071] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A modified lithium cobalt oxide material, characterized in that, The modified lithium cobalt oxide material comprises a doped lithium cobalt oxide core, wherein the doping element in the doped lithium cobalt oxide core includes at least one of aluminum, magnesium, or zirconium; and an amorphous fast ion conductor coating layer covering the doped lithium cobalt oxide core; the tap density of the modified lithium cobalt oxide material is greater than or equal to 2.9 g / cm³. 3 The specific surface area (BET) is 3.2 m². 2 / g~3.8m 2 / g.

2. The modified lithium cobalt oxide material according to claim 1, characterized in that, The secondary particles of the modified lithium cobalt oxide material are spherical; Preferably, the doping amount of the doping element in the doped lithium cobalt oxide core is 1000ppm to 10000ppm; Preferably, the amorphous fast ion conductor includes a layer comprising at least one of lithium phosphate, lithium zirconate, or niobium oxalate.

3. A method for preparing the modified lithium cobalt oxide material according to claim 1 or 2, characterized in that, The preparation method includes: Solution A was prepared by mixing cobalt salt with doped element salt; solution B was prepared by mixing precipitant; and solution C was prepared by mixing fast ion conductor salt. Solution A and solution B are mixed in parallel flow to carry out a first reaction and generate a first reactant. Stop feeding solution A, and simultaneously mix solution B and solution C in parallel flow to carry out a second reaction, generating a second reactant and obtaining a slurry; The slurry was subjected to solid-liquid separation, pulping and washing, and drying in sequence, followed by a first calcination to obtain the precursor. The precursor is mixed with a lithium source and subjected to a second calcination to obtain a modified lithium cobalt oxide material.

4. The method for preparing lithium cobalt oxide material according to claim 3, characterized in that, In solution A, the concentration of cobalt is 100 g / L to 150 g / L; the concentration of dopant is 1 g / L to 2 g / L. Preferably, the dopant salt includes at least one of the chloride, sulfate, or nitrate salts of the dopant element; the dopant element includes at least one of aluminum, magnesium, or zirconium. Preferably, the concentration of the precipitant in solution B is 200 g / L to 300 g / L; Preferably, the precipitant comprises ammonium bicarbonate; Preferably, in solution C, the concentration of the fast ion conductor salt is 0.1 mol / L to 2 mol / L; Preferably, the fast ion conductor salt includes at least one of lithium phosphate, lithium zirconate, or lithium niobate.

5. The method for preparing the modified lithium cobalt oxide material according to claim 3 or 4, characterized in that, The preparation method includes: preparing the precipitant into a base solution, wherein the concentration of the precipitant in the base solution is 10 g / L to 30 g / L; and mixing the solution A and the solution B in the base solution in a parallel flow. Preferably, the volumetric flow rate of solution A is 70 L / h to 100 L / h; the growth rate of the first reactant is 0.15 μm / h to 0.20 μm / h. Preferably, the volumetric flow rate ratio of solution A to solution B is 1:(1~4); Preferably, the pH value of the first reaction is 7.0~8.0, and the temperature is 25℃~35℃.

6. The method for preparing the modified lithium cobalt oxide material according to any one of claims 3-5, characterized in that, The preparation method further includes: after the average particle size of the first reactant is reduced to 10μm~19μm, the temperature is increased to the temperature required for the second reaction, and then the solution C is mixed in parallel flow. Preferably, the temperature of the second reaction is 45°C to 60°C; Preferably, the volumetric flow rate of solution C is 1 / 6 to 1 / 10 of the volumetric flow rate of solution A in the first reaction, and the growth rate of the second reactant is 0.01 μm / h to 0.03 μm / h; Preferably, the second reaction takes 4 to 10 hours.

7. The method for preparing the modified lithium cobalt oxide material according to any one of claims 3-6, characterized in that, The first calcination temperature is 650℃~700℃.

8. The method for preparing the modified lithium cobalt oxide material according to any one of claims 3-7, characterized in that, The second calcination temperature is 700℃~900℃, and the time is 8h~14h.

9. A positive electrode sheet, characterized in that, The material contains the modified lithium cobalt oxide material according to claim 1 or 2, or the modified lithium cobalt oxide material obtained by the preparation method according to any one of claims 3-8.

10. A battery, characterized in that, It contains the positive electrode sheet as described in claim 9.

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