Non-phase-inversion aluminum-doped cobalt carbonate and preparation method thereof, positive electrode material and battery

Abstract

The invention provides phase-inversion-free aluminum-doped cobalt carbonate and a preparation method thereof, a positive electrode material and a battery, the preparation method comprises the following steps: feeding an aluminum-containing first cobalt salt solution and a first precipitant solution into a reaction device, and carrying out a first precipitation reaction to obtain a first reacted material containing first solid-phase particles; introducing a second cobalt salt solution and a second precipitant solution into the first reaction post-material, and carrying out a second precipitation reaction to prepare aluminum-containing cobalt carbonate, so as to obtain a second reaction post-material containing second solid-phase particles; wherein the average particle size of the second solid-phase particles is 2-3 [mu] m larger than that of the first solid-phase particles. According to the method, the aluminum-containing first cobalt salt solution is firstly adopted for the first precipitation reaction, then the aluminum-free second cobalt salt solution is adopted for the second precipitation reaction, and the mass concentrations of cobalt in the two stages of reactions are controlled to be the same, so that the aluminum segregation phenomenon in the highly aluminum-doped precursor can be greatly reduced, and the material percent of pass is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and particularly to non-phase-transition aluminum-doped cobalt carbonate, a preparation method thereof, a cathode material and a battery. Background Art

[0002] Lithium-ion batteries, with their core advantages such as high energy density, high power density, and high safety performance, are widely used in fields such as consumer electronics, power tools, power energy storage, and aerospace. They are currently the fastest-developing and most promising new energy storage technologies.

[0003] With the progress of scientific and technological levels and the expansion of energy demand, it has become an urgent task to develop the next-generation lithium-ion batteries with higher energy density. Among them, the cathode material is the technical bottleneck determining the battery energy density and accounts for more than one-third of the total cost of lithium-ion batteries.

[0004] Therefore, researching and developing cathode materials with lower cost and higher capacity is one of the important development goals of current lithium-ion battery technology. Among the commercially available cathode materials, the layered lithium cobaltate material has the highest energy density and is also the most competitive and possible cathode material for realizing the next-generation lithium-ion batteries with higher energy density.

[0005] For lithium cobaltate materials, as the earliest commercially available cathode materials, the current large-scale commercialization level still remains within 4.6V. There is still a certain gap between the actual discharge capacity and the theoretical capacity. Further increasing the working cut-off voltage can improve the lithium-ion utilization rate and then increase the discharge capacity and energy density. Therefore, the development of modification technologies for high-voltage lithium cobaltate is a hot topic of common concern in the academic and industrial circles.

[0006] From the perspective of the bulk phase, at high voltages, especially above 4.55V, the bulk phase will undergo an irreversible H3-M2 phase transition, resulting in drastic changes in the unit cell parameters and lattice distortion, which easily cause problems such as cracks and particle fragmentation. On the other hand, the surface stability of lithium cobaltate will also be severely affected by multiple factors at high voltages, thus affecting the electrical properties of lithium cobaltate materials.

[0007] Currently, the developed lithium cobaltate materials will cause the attenuation of the electrical properties of battery materials at 4.55V. Therefore, different methods are used to increase the voltage platform of the materials to improve their capacity. Using Al doping is a special improvement method. However, with the increase of the Al doping content, the internal distribution is often not easy to be uniform, and there will be Al segregation on the surface of cobalt carbonate during the process of processing the slurry into dry materials, so as to avoid Al segregation after calcination, ultimately affecting the battery performance of the materials.

[0008] Therefore, it is necessary to develop lithium cobaltate materials that can improve the electrical properties at high voltages. Summary of the Invention

[0009] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide non-phase-transition aluminum-doped cobalt carbonate, its preparation method, cathode material and battery. By means of a co-precipitation preparation method, a non-phase-transition cobalt carbonate precursor material with uniform aluminum doping is obtained, and the surface aluminum does not segregate during subsequent processing, thereby reducing the problem of the decline in electrical performance caused by segregation.

[0010] To achieve this purpose, the present invention adopts the following technical solutions:

[0011] In the first aspect, the present invention provides a preparation method of non-phase-transition aluminum-doped cobalt carbonate, and the preparation method includes the following steps:

[0012] A first cobalt salt solution containing aluminum and a first precipitant solution are fed into a reaction device to carry out a first precipitation reaction to obtain a first post-reaction material containing first solid-phase particles.

[0013] Then, a second cobalt salt solution and a second precipitant solution are introduced into the first post-reaction material to carry out a second precipitation reaction to prepare aluminum-doped cobalt carbonate, and a second post-reaction material containing second solid-phase particles is obtained.

[0014] Among them, the average particle size of the second solid-phase particles is 2-3 μm larger than that of the first solid-phase particles.

[0015] In order to improve the performance of lithium cobaltate materials at high voltages, aluminum needs to be doped. However, the doping of a high amount of aluminum easily leads to the segregation of aluminum on the surface of the cathode material, thereby causing a decline in the electrical performance of the cathode material. The preparation method of non-phase-transition aluminum-doped cobalt carbonate provided by the present invention has the following two key points: A. Adopt a two-stage precipitation process. Among them, a first cobalt salt solution containing aluminum is introduced in the first precipitation reaction to achieve aluminum doping; and a second cobalt salt solution without aluminum is used in the second precipitation reaction to avoid surface doping of aluminum, thereby preventing segregation during drying or the subsequent calcination process of preparing the cathode material; B. The present invention strictly controls the average particle size of the second solid-phase particles to be 2-3 μm larger than that of the first solid-phase particles, so as to ensure that the doping amount of aluminum is within the target range without segregation of aluminum.

[0016] Preferably, the molar concentration of aluminum in the first cobalt salt solution containing aluminum is 83-115 mmol / L.

[0017] Preferably, the molar concentration of cobalt in the first cobalt salt solution containing aluminum is 1.8-2 mol / L.

[0018] Preferably, the concentration of the first precipitant solution is 2.0-3.0 mol / L.

[0019] Preferably, the temperatures of the first precipitation reaction and the second precipitation reaction are each independently 35-70 °C.

[0020] Preferably, the stirring rates of the first precipitation reaction and the second precipitation reaction are each independently 200 to 400 rpm.

[0021] Preferably, the pH values of the first precipitation reaction and the second precipitation reaction are each independently 6.5 to 8.5.

[0022] Preferably, the ratio of the flow rate of the first cobalt salt solution to the flow rate of the first precipitant solution is 0.4 to 0.6:1.

[0023] Preferably, the ratio of the flow rate of the second cobalt salt solution to the flow rate of the second precipitant solution is 0.4 to 0.6:1.

[0024] Preferably, the mass concentration of cobalt in the first cobalt salt solution is the same as the mass concentration of cobalt in the second cobalt salt solution.

[0025] The difference in the average particle size between the second solid-phase particles and the first solid-phase particles is the thickness of the lithium carbonate deposited by the second precipitation reaction. Since the outer-layer lithium carbonate can prevent aluminum from migrating to the surface layer and thus avoid segregation, the thickness of this outer-layer lithium carbonate is crucial. By controlling the thickness within this range in the present invention, it can not only ensure that aluminum does not segregate during subsequent washing, drying, and calcination processes, but also ensure the uniformity of the distribution of aluminum within the lithium carbonate, significantly improving the electrical properties of the cathode material.

[0026] Preferably, the preparation method further includes: washing and drying the solid phase obtained after the second precipitation reaction in sequence to obtain an aluminum-doped cobalt carbonate precursor.

[0027] Preferably, the washing is performed with hot water.

[0028] Preferably, the temperature of the hot water is 65 to 95 °C.

[0029] Preferably, the drying temperature is 100 to 150 °C.

[0030] In a second aspect, the present invention provides a non-phase-transition aluminum-doped cobalt carbonate, which is prepared by using the preparation method of the non-phase-transition aluminum-doped cobalt carbonate described in the first aspect.

[0031] Preferably, the cobalt content in the non-phase-transition aluminum-doped cobalt carbonate is 43 to 45 wt%, and the aluminum content is 0.59 to 0.88 wt%.

[0032] In a third aspect, the present invention provides a cathode material, which is prepared by using the non-phase-transition aluminum-doped cobalt carbonate described in the second aspect.

[0033] Fourthly, the present invention provides a lithium-ion battery, and the lithium-ion battery includes the cathode material described in the first aspect.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] (1) The preparation method of non-phase-transition aluminum-doped cobalt carbonate provided by the present invention can prepare large-particle precursors by a coprecipitation method, and has a high aluminum doping amount, with an aluminum content above 0.59 wt%. Aluminum segregation does not occur even under high aluminum doping conditions, and aluminum is evenly distributed in cobalt carbonate, significantly improving the performance of the precursor.

[0036] (2) The cathode material prepared from the non-phase-transition aluminum-doped cobalt carbonate provided by the present invention has excellent electrical properties and is not prone to attenuation under high-voltage conditions above 4.55 V, showing broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the SEM image of the solid phase after washing in the preparation method of non-phase-transition aluminum-doped cobalt carbonate provided in Example 1 of the present invention.

[0038] Figure 2 is the SEM image of the solid phase after calcination of the non-phase-transition aluminum-doped cobalt carbonate provided in Example 1 of the present invention.

[0039] Figure 3 is the SEM image of the solid phase after washing in the preparation method of non-phase-transition aluminum-doped cobalt carbonate provided in Comparative Example 4 of the present invention.

[0040] Figure 4 is the SEM image of the solid phase after calcination of the non-phase-transition aluminum-doped cobalt carbonate provided in Comparative Example 4 of the present invention.

[0041] Figure 5 is the XRD pattern of the solid phase after calcination of the non-phase-transition aluminum-doped cobalt carbonate provided in Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0042] For ease of understanding the present invention, the following examples are listed. Those skilled in the art should understand that the examples are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0043] It should be understood that in the description of the present invention, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, "a plurality of" means two or more.

[0044] At present, for lithium cobaltate materials, electrical performance attenuation continuously occurs under the condition of a high voltage of 4.55V. Using aluminum doping can better improve the attenuation problem of lithium cobaltate materials under high voltage. However, as the aluminum doping content increases, the internal distribution is often not easy to be uniform, and during the process of processing the slurry into dry materials (including washing and drying), there will be Al segregation on the surface of cobalt carbonate, and aluminum segregation is also likely to occur during the subsequent calcination process after mixing with the lithium source, ultimately affecting the high-voltage electrical performance of the cathode material.

[0045] To solve the above problems, the present invention adopts the following implementation manners and makes a detailed description.

[0046] In some embodiments, the present invention provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate, and the preparation method includes the following steps: A first cobalt salt solution containing aluminum and a first precipitant solution are fed into a reaction device to carry out a first precipitation reaction to obtain a first post-reaction material containing first solid-phase particles. Then, a second cobalt salt solution and a second precipitant solution are introduced into the first post-reaction material to carry out a second precipitation reaction to prepare aluminum-doped cobalt carbonate, and a second post-reaction material containing second solid-phase particles is obtained. Among them, the average particle size of the second solid-phase particles is 2-3μm larger than that of the first solid-phase particles. For example, it can be 2μm, 2.2μm, 2.3μm, 2.4μm, 2.5μm, 2.6μm, 2.7μm, 2.8μm, 2.9μm or 3μm, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0047] The technical mechanism of the present invention is as follows: The aluminum doped in cobalt carbonate will migrate during washing, drying, and calcination in the process of preparing the cathode material, and surface aluminum will segregate and aggregate during the migration process, resulting in non-uniformity of aluminum in the cathode material; while the present invention only incorporates aluminum in the first precipitation reaction, and the outer layer is a cobalt carbonate layer without aluminum doping. Only by ensuring that the doping of aluminum is uniform during the first co-precipitation process, during the processes of washing, drying, and subsequent calcination, the internal aluminum will also migrate, but this migration is uniform, thereby achieving the effect of uniform distribution of aluminum inside cobalt carbonate, that is, the outer-layer cobalt carbonate can play a role in blocking the migration of aluminum to the surface during washing, drying, and subsequent calcination processes.

[0048] The difference between the average particle size of the second solid-phase particles and that of the first solid-phase particles in the present invention is the thickness of cobalt carbonate deposited by the second precipitation reaction. Since the outer-layer cobalt carbonate can prevent aluminum from migrating to the surface layer and thus avoid segregation, the thickness of this outer-layer cobalt carbonate is crucial. By controlling the thickness within this range, the present invention can not only ensure that aluminum does not segregate during subsequent washing, drying, and calcination processes but also ensure the uniformity of aluminum distribution within the cobalt carbonate, significantly improving the electrical performance of the cathode material. Moreover, here, the inventors found that when the average particle size of the second solid-phase particles is larger than that of the first solid-phase particles, it is difficult for aluminum to migrate and cover the outer-layer cobalt carbonate during subsequent washing, drying, and calcination processes, resulting in the collapse of the part without doped aluminum in the material during use, seriously affecting the electrochemical performance of the battery.

[0049] The present invention can be applied to high-aluminum-doped precursor materials, thus solving the problem of aluminum segregation in lithium cobaltate cathode materials.

[0050] In some embodiments, the molar concentration of aluminum in the first cobalt salt solution containing aluminum is 83 - 115 mmol / L. For example, it can be 83 mmol / L, 87 mmol / L, 91 mmol / L, 94 mmol / L, 98 mmol / L, 101 mmol / L, 105 mmol / L, 108 mmol / L, 112 mmol / L, or 115 mmol / L, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0051] The molar concentration of aluminum in the first cobalt salt solution containing aluminum in the present invention is crucial for the incorporation amount of aluminum and the uniformity of aluminum in the coprecipitation reaction. By controlling the molar concentration of aluminum in the first cobalt salt solution containing aluminum within the above range, the incorporation amount and incorporation uniformity of aluminum can be better improved.

[0052] In some embodiments, the molar concentration of cobalt in the first cobalt salt solution containing aluminum is 1.8 - 2 mol / L. For example, it can be 1.8 mol / L, 1.83 mol / L, 1.85 mol / L, 1.87 mol / L, 1.89 mol / L, 1.92 mol / L, 1.94 mol / L, 1.96 mol / L, 1.98 mol / L, or 2 mol / L, etc., but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0053] The present invention preferably controls the molar concentration of cobalt in the first cobalt salt solution within the above range, which can better ensure the uniformity of aluminum during the precipitation process, reduce wastewater generation, and be more economical.

[0054] In some embodiments, the anion in the first cobalt salt solution containing aluminum includes any one or a combination of at least two of sulfate, nitrate or chloride. Typical but non-limiting combinations are combinations of sulfate and nitrate, chloride and nitrate, and sulfate and chloride.

[0055] In some embodiments, the precipitant in the first precipitant solution includes any one or a combination of at least two of ammonium carbonate, ammonium bicarbonate, sodium bicarbonate or sodium carbonate. Typical but non-limiting combinations are combinations of ammonium carbonate and ammonium bicarbonate, sodium carbonate and ammonium bicarbonate, ammonium carbonate and sodium carbonate, sodium bicarbonate and sodium carbonate, and ammonium carbonate and sodium bicarbonate.

[0056] In some embodiments, the concentration of the first precipitant solution is 2.0 - 3.0 mol / L, for example, it can be 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L, 2.5 mol / L, 2.6 mol / L, 2.7 mol / L, 2.8 mol / L, 2.9 mol / L or 3.0 mol / L, etc.

[0057] In some embodiments, the temperatures of the first precipitation reaction and the second precipitation reaction are each independently 35 - 50 °C, for example, they can be 35 °C, 39 °C, 43 °C, 47 °C or 50 °C, preferably 30 - 40 °C, etc., but are not limited to the listed values, and other unlisted values within this range are equally applicable.

[0058] In a preferred manner, the temperature of the first precipitation reaction is the same as that of the second precipitation reaction.

[0059] In some embodiments, the stirring rates of the first precipitation reaction and the second precipitation reaction are each independently 200 - 400 rpm, for example, they can be 200 rpm, 223 rpm, 245 rpm, 267 rpm, 289 rpm, 312 rpm, 334 rpm, 356 rpm, 378 rpm or 400 rpm, etc., but are not limited to the listed values, and other unlisted values within this range are equally applicable.

[0060] In a preferred manner, the stirring rate of the first precipitation reaction is greater than that of the second precipitation reaction, which can make the doping of aluminum in the first precipitation reaction more uniform.

[0061] In some embodiments, the pH of the first precipitation reaction and the second precipitation reaction are each independently 6.5 to 8.5. For example, it can be 6.5, 6.8, 7, 7.2, 7.4, 7.7, 7.9, 8.1, 8.3, or 8.5, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0062] The pH of the first precipitation reaction is greater than or equal to the pH of the second precipitation reaction. For example, the pH of the first precipitation reaction is 7.3 to 7.5, such as 7.3, 7.4, or 7.5, etc. The pH of the second precipitation reaction is 7.2 to 7.4, such as 7.2, 7.3, or 7.4, etc.

[0063] In some embodiments, the flow rate of the first cobalt salt solution is 20 to 40 mL / h. For example, it can be 20 mL / h, 23 mL / h, 25 mL / h, 27 mL / h, 29 mL / h, 32 mL / h, 34 mL / h, 36 mL / h, 38 mL / h, or 40 mL / h, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0064] In some embodiments, the flow rate of the first precipitant solution is 50 to 70 mL / h. For example, it can be 50 mL / h, 53 mL / h, 55 mL / h, 57 mL / h, 59 mL / h, 62 mL / h, 64 mL / h, 66 mL / h, 68 mL / h, or 70 mL / h, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0065] In some embodiments, the ratio of the flow rate of the first cobalt salt solution to the flow rate of the first precipitant solution is 0.4 to 0.6:1. For example, it can be 0.4:1, 0.43:1, 0.45:1, 0.47:1, 0.49:1, 0.52:1, 0.54:1, 0.56:1, 0.58:1, or 0.6:1, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0066] In some embodiments, the ratio of the flow rate of the second cobalt salt solution to the flow rate of the second precipitant solution is 0.4 to 0.6:1. For example, it can be 0.4:1, 0.43:1, 0.45:1, 0.47:1, 0.49:1, 0.52:1, 0.54:1, 0.56:1, 0.58:1, or 0.6:1, etc., but not limited to the listed values. Other unlisted values within this range are equally applicable.

[0067] In some embodiments, the flow rate of the second cobalt salt solution is 5 to 15 mL / h. For example, it can be 5 mL / h, 7 mL / h, 8 mL / h, 9 mL / h, 10 mL / h, 11 mL / h, 12 mL / h, 13 mL / h, 14 mL / h, or 15 mL / h, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0068] In some embodiments, the flow rate of the second cobalt salt solution is 10 to 25 mL / h. For example, it can be 10 mL / h, 12 mL / h, 14 mL / h, 15 mL / h, 17 mL / h, 19 mL / h, 20 mL / h, 22 mL / h, 24 mL / h, or 25 mL / h, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0069] Preferably, in some embodiments, the mass concentration of cobalt in the first cobalt salt solution is the same as the mass concentration of cobalt in the second cobalt salt solution.

[0070] The present invention ensures that the concentrations of cobalt in the first cobalt salt solution and the second cobalt salt solution are consistent, and cobalt carbonate precipitates with a similar structure can be obtained, thereby ensuring the structural uniformity of the inner-layer cobalt carbonate and the outer-layer cobalt carbonate. On the one hand, it guarantees the electrical properties of the cathode material, and on the other hand, it ensures the uniformity of subsequent aluminum migration inside.

[0071] In some embodiments, the average particle size of the first solid-phase particles is 15 to 20 μm. For example, it can be 15 μm, 15.6 μm, 16.2 μm, 16.7 μm, 17.3 μm, 17.8 μm, 18.4 μm, 18.9 μm, 19.5 μm, or 20 μm, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0072] In some embodiments, the average particle size of the second solid-phase particles is 17 to 23 μm. For example, it can be 17 μm, 17.7 μm, 18.4 μm, 19 μm, 19.7 μm, 20.4 μm, 21 μm, 21.7 μm, 22.4 μm, or 23 μm, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0073] In some embodiments, the preparation method further includes: washing and drying the solid phase obtained after the second precipitation reaction in sequence to obtain an aluminum-doped cobalt carbonate precursor.

[0074] In some embodiments, the washing is performed with hot water.

[0075] The present invention uses hot water for washing, which can better wash away the residual solution on the surface of the second solid-phase particles.

[0076] The washing method described in the present invention is not particularly limited, and can be carried out by a washing method well known to those skilled in the art, for example, centrifugal washing can be used, that is, the second reaction material is first centrifuged and the solid phase is taken and then mixed with hot water, and then centrifuged. There is no particular limitation on the specific number of washing times, for example, it can be 1 time, 2 times, 3 times, 4 times or 5 times, etc.

[0077] In some embodiments, the temperature of the hot water is 65-95°C, for example, it can be 65°C, 70°C, 75°C, 80°C, 85°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C or 95°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0078] In some embodiments, the drying temperature is 100-150°C, for example, it can be 100°C, 106°C, 112°C, 117°C, 123°C, 128°C, 134°C, 139°C, 145°C or 150°C, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0079] The present invention has no special limitation on the drying time, as long as the solid phase can be dried. The drying time known to those skilled in the art can be used. For example, in some embodiments, the drying time is 6 h to 10 h, such as 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h or 10 h, etc., but is not limited to the listed values, and other values ​​not listed within the range are also applicable.

[0080] In a second aspect, the present invention provides a non-phase-inverting aluminum-doped cobalt carbonate, wherein the non-phase-inverting aluminum-doped cobalt carbonate is prepared by the preparation method of the non-phase-inverting aluminum-doped cobalt carbonate described in the first aspect.

[0081] The non-phase transition referred to in the present invention means that under high voltage, especially 4.55V voltage conditions, the lithium cobalt oxide formed by subsequent calcination will not undergo H3-M2 phase transition, and there will be no drastic changes in unit cell parameters, lattice distortion, cracks and particle breakage.

[0082] In some embodiments, the cobalt content in the non-phase-transition aluminum-doped cobalt carbonate is 43-45 wt%, for example, it can be 43 wt%, 43.3 wt%, 43.5 wt%, 43.7 wt%, 43.9 wt%, 44.2 wt%, 44.4 wt%, 44.6 wt%, 44.8 wt% or 45 wt%, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable. The aluminum content is 0.59-0.88 wt%, for example, it can be 0.59 wt%, 0.63 wt%, 0.66 wt%, 0.69 wt%, 0.72 wt%, 0.76 wt%, 0.79 wt%, 0.82 wt%, 0.85 wt% or 0.88 wt%, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0083] Generally, the aluminum content doped in cobalt carbonate is only 0.12 wt% - 0.36 wt%. However, in order to further improve the performance of lithium cobaltate at high voltages, it is necessary to further increase the doped aluminum content. It is precisely when the aluminum content is increased to 0.59 wt% - 0.88 wt% that although the high-voltage performance is improved, the problem of aluminum segregation is more likely to occur. The preparation method provided by the present invention can solve the problem of aluminum segregation.

[0084] In a third aspect, the present invention provides a cathode material, which is prepared by using the non-phase-transition aluminum-doped cobalt carbonate described in the second aspect.

[0085] In some embodiments, the preparation method of the cathode material includes: first, calcine the non-phase-transition aluminum-doped cobalt carbonate to obtain a calcined solid phase, and then mix the calcined solid phase with a lithium source and obtain the cathode material through a post-process.

[0086] In some embodiments, the temperature of the calcination is 300-1100 °C, for example, it can be 300 °C, 389 °C, 478 °C, 567 °C, 656 °C, 745 °C, 834 °C, 923 °C, 1012 °C or 1100 °C, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0087] In some embodiments, the time of the calcination is 0.5-5 h, for example, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h or 5 h, etc., but not limited to the listed values, and other unlisted values within this range are equally applicable.

[0088] In some embodiments, the lithium source includes lithium carbonate and / or lithium hydroxide.

[0089] The present invention has no special restrictions on the post-process, and it can be carried out using the post-process technology well-known to those skilled in the art, or adjusted according to the actual situation.

[0090] In a fourth aspect, the present invention provides a lithium-ion battery, which includes the positive electrode material described in the third aspect.

[0091] The present invention has no special restrictions on the negative electrode material, electrolyte, etc. in the lithium-ion battery, and common materials for lithium-ion batteries such as negative electrode materials and electrolytes well-known to those skilled in the art can be used.

[0092] For example, in some embodiments, the negative electrode material of the lithium-ion battery includes any one or a combination of at least two of graphite, silicon-based materials, lithium titanate, alloys, or metal oxides, etc.

[0093] In some embodiments, the electrolyte of the lithium-ion battery includes lithium salts, organic solvents, additives, etc. Among them, the lithium salts include any one or a combination of at least two of LiPF6, LiBF4, LiClO4, or LiTFSI, etc. Generally, LiPF6 is preferably used, which has good electrochemical stability and ionic conductivity. The organic solvents include, but are not limited to, any one or a combination of at least two of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, diethyl carbonate, or dimethyl ether. The additives include film-forming additives, conductive additives, stabilizers, or ionic liquids, etc. Among them, the film-forming additives include vinylene carbonate and / or fluoroethylene carbonate; the conductive additives include lithium bis(oxalato)borate and / or lithium difluoro(oxalato)borate; the stabilizers include 1,3-propane sultone and / or ethylene sulfate; the ionic liquids include imidazole-based ionic liquids, pyrrolidine-based ionic liquids, quaternary ammonium salt-based ionic liquids, or phosphate-based ionic liquids, etc.

[0094] In some embodiments, the lithium-ion battery is a solid electrolyte battery, and the electrolyte used therein is a solid electrolyte, such as an oxide, a sulfide, or a polymer electrolyte, etc.

[0095] Example 1

[0096] This example provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate, and the preparation method includes the following steps:

[0097] (1) A first cobalt salt solution containing aluminum (aluminum: 83 mmol / L, cobalt: 1.866 mol / L) and a first precipitant solution (a 2.78 mol / L ammonium bicarbonate solution) are respectively fed into a reaction kettle at 30 mL / h and 57 mL / h, and a first precipitation reaction is carried out at 36 °C, 380 rpm, and a condition of 7.3 - 7.5 until the average particle size of the solid particles therein is 18.5 μm, obtaining a first reaction product containing the first solid-phase particles.

[0098] (2) The second cobalt salt solution (cobalt: 1.866 mol / L) and the second precipitant solution (ammonium bicarbonate solution with a concentration of 2.78 mol / L) are respectively introduced into the first post-reaction material at a rate of 10 mL / h and 17.5 mL / h, and the second precipitation reaction is carried out at 36 °C, 230 rpm and a pH of 7.2 - 7.4 to prepare cobalt aluminum carbonate, until the average particle size of the second solid-phase particles is 2.5 μm larger than that of the first solid-phase particles, that is, when the average particle size of the second solid-phase particles reaches 21 μm, the feeding is stopped, and the second post-reaction material containing the second solid-phase particles is obtained;

[0099] (3) The second post-reaction material is fed into a centrifuge and washed with hot water at a temperature of 70 °C as the washing medium, and the washed material is dried in an oven at 110 °C for 8 h to obtain non-phase-transition aluminum-doped cobalt carbonate.

[0100] Example 2

[0101] This example provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate, and the preparation method includes the following steps:

[0102] (1) The first cobalt salt solution containing aluminum (aluminum: 115 mmol / L, cobalt: 1.8 mol / L) and the first precipitant solution (ammonium bicarbonate solution with a concentration of 2.0 mol / L) are respectively fed into the reaction kettle at a rate of 20 mL / h and 40 mL / h, and the first precipitation reaction is carried out at 35 °C, 200 rpm and a pH of 6.8 - 7.1 until the average particle size of the solid particles therein reaches 15.6 μm, and the first post-reaction material containing the first solid-phase particles is obtained.

[0103] (2) The cobalt salt solution (cobalt: 1.8 mol / L) and the second precipitant solution (ammonium bicarbonate solution with a concentration of 2.0 mol / L) are respectively introduced into the first post-reaction material at a rate of 5 mL / h and 10 mL / h, and the second precipitation reaction is carried out at 35 °C, 200 rpm and a pH of 6.8 - 7.1 to prepare cobalt aluminum carbonate, until the average particle size of the second solid-phase particles is 3 μm larger than that of the first solid-phase particles, that is, when the average particle size of the second solid-phase particles reaches 18.6 μm, the feeding is stopped, and the second post-reaction material containing the second solid-phase particles is obtained;

[0104] (3) The second post-reaction material is fed into a centrifuge and washed with hot water at a temperature of 95 °C as the washing medium, and the washed material is dried in an oven at 130 °C for 6 h to obtain non-phase-transition aluminum-doped cobalt carbonate.

[0105] Example 3

[0106] This example provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate, and the preparation method includes the following steps:

[0107] (1) The first cobalt salt solution containing aluminum (aluminum: 100 mmol / L, cobalt: 2.0 mol / L) and the first precipitant solution (3.0 mol / L ammonium bicarbonate solution) are fed into the reaction kettle at 40 mL / h and 64 mL / h respectively, and the first precipitation reaction is carried out at 40 °C, 400 rpm and a pH of 7.0 - 7.3 until the average particle size of the solid particles therein is 19.7 μm, obtaining the first post-reaction material containing the first solid phase particles.

[0108] (2) A cobalt salt solution (cobalt: 2.0 mol / L) and a second precipitant solution (3.0 mol / L ammonium bicarbonate solution) are respectively fed into the first post-reaction material at a rate of 15 mL / h and 24 mL / h, and the second precipitation reaction is carried out at 40 °C, 300 rpm and a pH of 7 - 7.3 to prepare cobalt aluminum carbonate until the average particle size of the second solid phase particles is 2 μm larger than that of the first solid phase particles, that is, when the average particle size of the second solid phase particles reaches 21.7 μm, the feeding is stopped, obtaining the second post-reaction material containing the second solid phase particles;

[0109] (3) The second post-reaction material is fed into a centrifuge and washed with hot water at 65 °C as the washing medium, and the washed material is dried in an oven at 100 °C for 10 h to obtain non-phase-transition aluminum-doped cobalt carbonate.

[0110] Example 4

[0111] This example provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate. Except that the cobalt contents in the first cobalt salt solution and the second cobalt salt solution are both 1.7 mol / L respectively, the rest are the same as in Example 1 and will not be elaborated here.

[0112] Example 5

[0113] This example provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate. Except that the cobalt contents in the first cobalt salt solution and the second cobalt salt solution are both 2.2 mol / L respectively, the rest are the same as in Example 1 and will not be elaborated here.

[0114] Example 6

[0115] This example provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate. Except that the aluminum content in the first cobalt salt solution containing aluminum is 80 mmol / L, the rest are the same as in Example 1 and will not be elaborated here.

[0116] Example 7

[0117] This example provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate. Except that the aluminum content in the first cobalt salt solution containing aluminum is 120 mmol / L, the rest are the same as in Example 1 and will not be elaborated here.

[0118] Example 8

[0119] This example provides a method for preparing aluminum-doped cobalt carbonate. Except that the cobalt concentration in the second cobalt salt solution in step (2) is 1.8 mol / L, that is, the cobalt concentration in the second cobalt salt solution is lower than that in the first cobalt salt solution, the rest are the same as in Example 1 and will not be elaborated here.

[0120] Example 9

[0121] This example provides a method for preparing aluminum-doped cobalt carbonate. Except that the cobalt concentration in the second cobalt salt solution in step (2) is 2.0 mol / L, that is, the cobalt concentration in the second cobalt salt solution is higher than that in the first cobalt salt solution, the rest are the same as in Example 1 and will not be elaborated here.

[0122] Comparative Example 1

[0123] This comparative example provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate. Except that the average particle size of the second solid-phase particles is 1.5 μm larger than that of the first solid-phase particles, that is, the feeding is stopped when the average particle size of the second solid-phase particles is 20 μm, the rest are the same as in Example 1 and will not be elaborated here.

[0124] Comparative Example 2

[0125] This comparative example provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate. Except that the average particle size of the second solid-phase particles is 4 μm larger than that of the first solid-phase particles, that is, the feeding is stopped when the average particle size of the second solid-phase particles is 22.5 μm, the rest are the same as in Example 1 and will not be elaborated here.

[0126] Comparative Example 3

[0127] This comparative example provides a method for preparing non-phase-transition aluminum-doped cobalt carbonate. Except that the average particle size of the solid particles after the first precipitation reaction in step (1) is 23 μm and the second precipitation reaction is not carried out, the rest are the same as in Example 1 and will not be elaborated here.

[0128] Comparative Example 4

[0129] This comparative example provides a method for preparing aluminum-doped cobalt carbonate. Except that the second cobalt salt solution in step (2) is replaced with an aluminum-containing first cobalt salt solution, the rest are the same as in Example 1 and will not be elaborated here.

[0130] Comparative Example 5

[0131] This comparative example provides a method for preparing aluminum-doped cobalt carbonate. Except that the doping amount of aluminum is only 0.35 wt%, the rest are the same as in Comparative Example 4 and will not be elaborated here.

[0132] The solid-phase products obtained in the above-mentioned examples and comparative examples were calcined at 700 °C for 1 h to obtain aluminum-doped cobalt oxide products.

[0133] Taking Example 1 as an example, the washed solid-phase particles and the calcined solid-phase particles in Example 1 were scanned using a scanning electron microscope, and the results are shown respectively as Figure 1 and Figure 2 shown;

[0134] Similarly, taking Comparative Example 4 as an example, the washed solid-phase particles and the calcined solid-phase particles in Example 1 were scanned using a scanning electron microscope, and the results are shown respectively as Figure 3 and Figure 4 shown.

[0135] It can be seen from Figures 1 to 4 that the surface of the aluminum-containing cobalt carbonate prepared in Example 1 was smooth after washing, and no aluminum precipitation phenomenon occurred on the surface after calcination. However, aluminum precipitation occurred on the surface of the aluminum-containing cobalt carbonate prepared in Comparative Example 4 after washing, and the aluminum precipitation phenomenon on the surface was more serious and the surface was uneven after calcination.

[0136] The dried solid-phase particles in Example 1 were subjected to XRD detection, and the detection diagram is as Figure 5 shown. It can be seen from Figure 5 that only cobalt carbonate was contained on the surface of Example 1, and no peak of aluminum was detected, indicating that there was no segregation of aluminum on the surface of the dried solid-phase particles in Example 1.

[0137] Test method: The cobalt content and aluminum content in the non-phase-transition aluminum-doped cobalt carbonate were measured by ICP, the particle size D50 of the solid-phase particles at different stages was measured by SEM, and whether there was segregation of aluminum in the non-phase-transition aluminum-doped cobalt carbonate was measured by XRD and SEM.

[0138] The test results of the above examples and comparative examples are shown in Table 1.

[0139] Table 1

[0140]

[0141]

[0142] It can be seen from Table 1 as follows:

[0143] (1) From Examples 1 to 3, it can be seen that the preparation method of the non-phase-transition aluminum-doped cobalt carbonate provided by the present invention can obtain non-phase-transition aluminum-doped cobalt carbonate without segregation under the condition of high aluminum doping. When the aluminum content in cobalt carbonate is above 0.6 wt%, the uniformity of the aluminum distribution in the doped cobalt carbonate can be achieved, and segregation of aluminum in cobalt oxide can be avoided after calcination.

[0144] (2) From a comprehensive comparison of Example 1 and Examples 4 to 5, it can be seen that in Example 1, the cobalt content in both the first cobalt salt solution and the second cobalt salt solution was 1.866 mol / L. Compared with Examples 4 to 5 where 1.7 mol / L and 2.2 mol / L were used respectively, aluminum-doped cobalt carbonate with uniform aluminum distribution could be obtained in Examples 1, 4 to 5, and there was no segregation after calcination. However, in Example 4, the cobalt concentration was relatively low, and the Al content in the first-step precipitated cobalt carbonate increased accordingly, which was likely to cause uneven internal Al precipitation, and the solution volume required for growth would increase, resulting in more wastewater, which was not conducive to cost control. In Example 5, the Al content in cobalt carbonate was too low to reach the target doping range. Thus, it is shown that by preferably using an appropriate cobalt concentration, the present invention can ensure the uniform distribution of aluminum precipitation while obtaining cobalt carbonate with a reasonable aluminum doping amount.

[0145] Similarly, from a reference to Examples 6 to 7, it can be seen that by preferably using an appropriate aluminum concentration, the present invention can ensure the uniform distribution of aluminum precipitation while obtaining cobalt carbonate with a reasonable aluminum doping amount.

[0146] (3) From a comprehensive comparison of Example 1 and Examples 8 to 9, it can be seen that in Example 1, the cobalt content in both the first cobalt salt solution and the second cobalt salt solution was 1.866 mol / L. Compared with Example 8 where the cobalt concentration in the second cobalt salt solution was 1.8 mol / L, that is, the cobalt concentration in the second cobalt salt solution was lower than that in the first cobalt salt solution, and Example 9 where the cobalt concentration in the second cobalt salt solution was 2.0 mol / L, that is, the cobalt concentration in the second cobalt salt solution was higher than that in the first cobalt salt solution, the solid-phase particle size obtained in Example 1 was relatively uniform, and the amount of wastewater generated was small. In Example 8, the growth time in the second stage would be prolonged, the amount of wastewater generated would increase relatively, and the corresponding ammonium bicarbonate consumption would increase, resulting in an increase in the system pH and larger particle sizes in the later stage, and small particles were likely to be generated; in Example 9, it was likely to cause a decrease in the system pH, resulting in a change in the later morphology of the solid-phase particles. Thus, it is shown that by preferably making the cobalt content in the solutions in the two stages the same, the present invention can better reduce the amount of wastewater and obtain a solid-phase product with uniform particle size and good morphology.

[0147] (4) It can be seen from Comprehensive Example 1 and Comparative Examples 1 to 4 that in Comparative Example 1, the average particle size of the second solid-phase particles is 1.5 μm larger than that of the first solid-phase particles, resulting in a relatively thin cobalt carbonate layer. There is a phenomenon of surface Al segregation during the subsequent treatment process, and the overall Al content is higher than the target value. In Comparative Example 2, the cobalt carbonate layer is too thick, the doped Al content fails to reach the target value, and the part without doped Al on the surface is prone to collapse during cycling after being made into lithium cobaltate. In Comparative Examples 3 to 4, Al segregation occurs during the subsequent treatment without coating a pure cobalt carbonate layer. In Comparative Example 5, although a solution containing aluminum has been used for precipitation all the time, due to the low doping amount of aluminum, only 0.35 wt%, the final product is evenly distributed without segregation phenomenon, indicating that the segregation phenomenon of aluminum during washing, drying and calcination only occurs under high aluminum doping conditions.

[0148] The present invention illustrates the detailed features of the present invention through the above-mentioned embodiments. However, the present invention is not limited to the above-mentioned detailed features, that is, it does not mean that the present invention must rely on the above-mentioned detailed features to be implemented. Those skilled in the art should understand that any improvement of the present invention, the equivalent replacement of the technical features selected by the present invention, the addition of auxiliary technical features, and the selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A preparation method of non-phase-transition aluminum-doped cobalt carbonate, characterized in that, The preparation method includes the following steps: A first cobalt salt solution containing aluminum and a first precipitant solution are fed into a reaction device to carry out a first precipitation reaction, obtaining a first post-reaction material containing first solid-phase particles; Then, a second cobalt salt solution and a second precipitant solution are introduced into the first post-reaction material to carry out a second precipitation reaction to prepare cobalt aluminum carbonate, obtaining a second post-reaction material containing second solid-phase particles; Wherein, the average particle size of the second solid-phase particles is 2-3 μm larger than that of the first solid-phase particles.

2. The preparation method according to claim 1, characterized in that, The molar concentration of aluminum in the first cobalt salt solution containing aluminum is 83-115 mmol / L; And / or, the molar concentration of cobalt in the first cobalt salt solution containing aluminum is 1.8-2 mol / L.

3. The preparation method according to claim 1 or 2, characterized in that, The temperatures of the first precipitation reaction and the second precipitation reaction are each independently 35-70 °C; And / or, the stirring rates of the first precipitation reaction and the second precipitation reaction are each independently 200-400 rpm; And / or, the pH values of the first precipitation reaction and the second precipitation reaction are each independently 6.5-8.

5.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The flow rate ratio of the first cobalt salt solution to the first precipitant solution is 0.4-0.6:1; And / or, the flow rate ratio of the second cobalt salt solution to the second precipitant solution is 0.4-0.6:

1.

5. The preparation method according to any one of claims 1 to 4, characterized in that, The mass concentration of cobalt in the first cobalt salt solution is the same as the mass concentration of cobalt in the second cobalt salt solution.

6. The preparation method according to any one of claims 1 to 5, characterized in that, The preparation method further includes: washing and drying the solid phase obtained after the second precipitation reaction in sequence to obtain a cobalt aluminum carbonate precursor; Wherein, the washing is carried out with hot water, the temperature of the hot water is 65-95 °C, and / or, the drying temperature is 100-150 °C.

7. A non-phase-transition aluminum-doped cobalt carbonate, characterized in that, The non-phase-transition cobalt aluminum doped carbonate is prepared by the preparation method of the non-phase-transition cobalt aluminum doped carbonate according to any one of claims 1-6.

8. The non-phase-transition aluminum-doped cobalt carbonate according to claim 7, wherein, The cobalt content in the non-phase-transition cobalt aluminum doped carbonate is 43-45 wt%, and the aluminum content is 0.59-0.88 wt%.

9. A cathode material, characterized in that, The positive electrode material is prepared by using the non-phase-transition cobalt aluminum doped carbonate according to claim 7 or 8.

10. A lithium-ion battery, characterized in that, The lithium ion battery includes the positive electrode material according to claim 9.

Images