A core-shell structured positive electrode precursor material, a preparation method therefor, and use thereof
By employing a core-shell structure and gradient doping in lithium-ion battery cathode materials, the problem of insufficient structural stability was solved, thereby improving the rate performance and cycle stability of the materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JINGMEN GEM NEW MATERIAL CO LTD
- Filing Date
- 2023-08-23
- Publication Date
- 2026-06-16
AI Technical Summary
The existing cathode materials for lithium-ion batteries have insufficient structural stability, resulting in low rate performance and easy shedding of the shell layer in the core-shell structure.
The cathode precursor material adopts a core-shell structure, with a high-nickel core and a high-manganese shell. Gradient doping is performed in the core structure near the shell. The gradient doping of doping elements optimizes capacity performance and enhances the core-shell bonding tightness.
It improves the structural stability and electrochemical performance of lithium-ion cathode materials, achieving a balance between cycle performance and capacity, and the shell layer is not easily detached.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of lithium-ion battery technology, and relates to a core-shell structured positive electrode precursor material, its preparation method, and its application. Background Technology
[0002] In recent years, the application areas of lithium-ion batteries have been continuously expanding, from traditional 3C products to current electric vehicles and smart grids. The new energy industry's demand for lithium-ion batteries, especially high-energy-density lithium batteries, is becoming increasingly urgent. To meet this demand, a large amount of research is dedicated to finding and developing electrode materials with high specific capacity.
[0003] Nickel-rich layered materials LiNi 1-x-y Mn x Co y O2(x+y≤0.4) (NCM) is considered the most promising cathode candidate material, boasting a capacity of 200 mAh / g and a high voltage of 3.8 V (vsLi+ / Li). However, Li... + / Ni 2+ Problems such as cation mixing, residual Li, poor thermal stability, and pulverization limit the cycle and rate performance of batteries. To date, scientists have attempted to improve structural stability through various strategies, including elemental doping, surface coating, and the formation of concentration gradients.
[0004] CN110880591A discloses a SiO2-coated lithium-ion battery cathode precursor material and its preparation method, comprising a core and a SiO2 coating layer at least partially covering the surface of the core, wherein the chemical structural formula of the core is Ni. x Co y M 1-x-y O, where M is selected from Mn or Al.
[0005] CN115092974A discloses a doped ternary precursor and its preparation method, a ternary cathode material, and a lithium-ion battery. In the precursor preparation, by adjusting the synthesis conditions, some of the doping element M (selected from Mg) is incorporated. 2+ Al 3+ Zr 4+ Ti 4+ Y 3 + 、Sr 2+ 、Nb 5+ W 6+ Mo 6+One or more) undergo heterogeneous co-precipitation, wherein the nano-sized M hydroxide particles precipitated alone or the M hydroxide particles are mixed with one or more of nickel hydroxide, cobalt hydroxide, and manganese hydroxide, and their main component is M or is entirely M. They have extremely high surface energy and will be adsorbed on the surface of larger crystalline ternary hydroxide precursor grains; thus obtaining a spherical secondary particle precursor composed of two distinctly different primary particles agglomerated.
[0006] Even after modification, the lithium-ion battery cathode materials described in the aforementioned literature still suffer from insufficient structural stability, inadequate rate performance, and easy shedding of the shell layer in the core-shell structure.
[0007] Therefore, how to improve the structural stability of lithium-ion cathode materials, thereby enhancing their electrochemical performance, is a technical problem that urgently needs to be solved. Summary of the Invention
[0008] To address the shortcomings of existing technologies, the present invention aims to provide a core-shell structured cathode precursor material, its preparation method, and its applications. The precursor material provided by this invention uses a high-nickel material as the core and a high-manganese material as the shell, along with gradient doping of synergistic doping elements. This optimizes capacity performance while ensuring material cycle performance, resulting in a tighter bond between the core and shell, improving the stability of the core-shell structured cathode material, and thus enhancing the performance of lithium-ion cathode materials.
[0009] To achieve this objective, the present invention adopts the following technical solution:
[0010] In a first aspect, the present invention provides a core-shell structured cathode precursor material, the core-shell structured cathode precursor material comprising a first nickel-cobalt-manganese precursor core and a second nickel-cobalt-manganese precursor shell layer located on the surface of the precursor core.
[0011] The core-shell structured cathode precursor material contains doping elements; the molar amount of nickel in the first nickel-cobalt-manganese precursor core accounts for ≥80% of the total molar amount of nickel-cobalt-manganese, for example, 80%, 83%, 85%, 88%, 90%, 93%, 95%, or 98%, etc., and the doping element gradually increases in the portion of the first nickel-cobalt-manganese precursor core near the shell layer; the molar amount of manganese in the second nickel-cobalt-manganese precursor core accounts for ≥45% of the total molar amount of nickel-cobalt-manganese, for example, 45%, 50%, 55%, 60%, or 65%, etc.
[0012] The doping elements in this invention are conventional doping processes. All types of elements that can be used for precursor doping are applicable to this invention. The elements can be selected according to actual needs, including but not limited to metallic elements (tungsten, aluminum, magnesium, zirconium, calcium, etc.) or non-metallic elements (nitrogen or boron, etc.). Any combination and selection can be made according to actual needs.
[0013] The precursor material provided by this invention uses a nickel-rich material with high energy density as the core and a high-manganese material with high stability as the shell. Gradient doping of synergistic doping elements is carried out in the core structure near the shell (the doping amount in other parts of the core and the shell is not gradient-doped). This can refine the size of the primary grains, allowing the manganese-rich precursor to grow better on the core surface. While ensuring the material's cycle performance, the capacity performance is optimized. Furthermore, gradient doping makes the bonding between the core and shell tighter, making the shell less prone to detachment, thus improving the stability of the core-shell structure cathode material and thereby enhancing the performance of the lithium-ion cathode material.
[0014] In this invention, gradient doping is only performed on the part of the core near the shell. If the entire core-shell structure is gradient doped or the doping elements are uniformly distributed throughout the core-shell structure, a tight bond between the shell and the core cannot be achieved, making the shell easy to detach.
[0015] Preferably, the total doping amount of the doping element is 1000 to 5000 ppm, such as 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm or 5000 ppm.
[0016] In a second aspect, the present invention provides a method for preparing a core-shell structured cathode precursor material as described in the first aspect, the method comprising the following steps:
[0017] The first nickel-cobalt-manganese mixed salt solution, the precipitant solution, the first complexing agent solution and the dopant solution were added to the bottom solution in a parallel flow to carry out the first stage coprecipitation reaction and the second stage coprecipitation reaction in sequence.
[0018] After the second stage coprecipitation reaction is completed, the first nickel-cobalt-manganese mixed salt solution is replaced with the second nickel-cobalt-manganese mixed salt solution to carry out the third stage coprecipitation reaction, and the core-shell structured cathode precursor material is obtained.
[0019] In the first nickel-cobalt-manganese mixed salt solution, the molar amount of nickel accounts for ≥80% of the total molar amount of nickel, cobalt, and manganese; during the second stage co-precipitation reaction, the feed flow rate of the dopant solution increases gradually; and in the second nickel-cobalt-manganese mixed salt solution, the molar amount of manganese accounts for ≥45% of the total molar amount of nickel, cobalt, and manganese.
[0020] In this invention, the flow rates of the co-precipitation reactions in the first and second stages are kept consistent.
[0021] This invention prepares a core-shell structured precursor material through a co-precipitation method in the precursor stage, while simultaneously achieving gradient doping of doping elements. This avoids the uneven doping of doping elements caused by solid-phase doping and yields a structurally stable material. The capacity performance is optimized while ensuring the cycling performance of the material, achieving a balance between cycling and capacity performance. Moreover, the preparation method is simple to operate and does not require additional complex preparation processes, making it suitable for large-scale production.
[0022] Preferably, the pH value of the base solution is 10 to 13, such as 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.8, 12, 12.3, 12.5, 12.8 or 13.
[0023] Preferably, the concentration of ammonia in the base solution is 5 to 20 g / L, such as 5 g / L, 10 g / L, 15 g / L, or 20 g / L.
[0024] Preferably, the temperature of the base liquid is 40-80°C, for example, 40°C, 50°C, 60°C, 70°C, or 80°C.
[0025] Preferably, the stirring rate of the base liquid is 200 to 500 rpm, such as 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm.
[0026] In this invention, the preparation parameters in the coprecipitation reaction process can be adaptively adjusted based on the base liquid, without any special limitations.
[0027] Preferably, the dopant solution further includes a second complexing agent.
[0028] In this invention, adding a second complexing agent solution to the dopant solution is beneficial for the uniform precipitation of the dopant element, so that the dopant element is evenly distributed in the precursor.
[0029] Preferably, the particle size of the reaction product of the first stage coprecipitation reaction is 45% to 55% of the final target particle size, such as 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, or 55%.
[0030] Preferably, the particle size of the reaction product of the second stage coprecipitation reaction is 85% to 95% of the final target particle size, such as 85%, 86%, 87%, 88%, 89%, 80%, 81%, 82%, 83%, 84%, or 85%.
[0031] In this invention, the core is prepared in two stages. In the first stage, if the core particle size is too large (exceeding 55%), it will lead to an overall high nickel content and Li content. + / Ni2+ The severe mixing of cations leads to poor cycling stability. Furthermore, the core obtained in the second stage has a particle size that is too small, less than 85%, meaning that the thickness of the gradient doped core layer is too thin. This results in a low overall nickel content and an inability to achieve a high initial capacity. On the other hand, if the core obtained in the second stage has a particle size that is too large, it will result in an excessively thin shell layer, which will affect the tightness of the core-shell contact and make the shell layer prone to detachment.
[0032] Preferably, during the second stage co-precipitation reaction, the feed flow rate of the dopant solution is increased in a gradient of 0.1 to 2 L / h, for example, 0.1 L / h, 0.3 L / h, 0.5 L / h, 0.8 L / h, 1 L / h, 1.3 L / h, 1.5 L / h, 1.8 L / h, or 2 L / h.
[0033] In this invention, during the second stage of the co-precipitation reaction, if the feed flow rate of the dopant solution increases too quickly, exceeding 2 L / h, the dopant element may not precipitate well, affecting uniformity. If it increases too slowly, below 0.1 L / h, the amount of dopant will be affected.
[0034] As a preferred technical solution, the preparation method includes the following steps:
[0035] A first nickel-cobalt-manganese mixed salt solution, a precipitant solution, a first complexing agent solution, and a dopant solution containing a second complexing agent are added concurrently to the base solution to carry out a first-stage co-precipitation reaction. After the particle size of the reaction product of the first-stage co-precipitation reaction reaches 45-55% of the final target particle size, a second-stage co-precipitation reaction is carried out. During the second-stage co-precipitation reaction, the feed flow rate of the dopant solution is gradually increased at a rate of 0.1-2 L / h until the particle size of the reaction product of the second-stage co-precipitation reaction reaches 85-95% of the final target particle size, at which point the reaction ends.
[0036] After the second stage coprecipitation reaction is completed, the first nickel-cobalt-manganese mixed salt solution is replaced with the second nickel-cobalt-manganese mixed salt solution to carry out the third stage coprecipitation reaction, and the core-shell structured cathode precursor material is obtained.
[0037] In the first nickel-cobalt-manganese mixed salt solution, the molar amount of nickel accounts for ≥80% of the total molar amount of nickel, cobalt, and manganese; during the second stage co-precipitation reaction, the feed flow rate of the dopant solution increases gradually; and in the second nickel-cobalt-manganese mixed salt solution, the molar amount of manganese accounts for ≥45% of the total molar amount of nickel, cobalt, and manganese.
[0038] Thirdly, the present invention provides a lithium-ion cathode material, which is obtained by mixing and sintering a core-shell structured cathode precursor material as described in the first aspect with a lithium source.
[0039] In this invention, lithium-ion materials are prepared from precursor materials, which improves the structural stability of lithium-ion cathode materials, thereby achieving a balance between cycle performance and capacity.
[0040] Furthermore, the precursor material of the present invention can also be used in sodium batteries.
[0041] Preferably, the sintering is carried out in an oxygen-containing atmosphere.
[0042] In this invention, the preparation process of lithium-ion cathode materials is a conventional technical process, and those skilled in the art can make adaptive selections of sintering temperature, number of sintering cycles and sintering time according to actual needs.
[0043] Fourthly, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising the lithium-ion positive electrode material as described in the third aspect.
[0044] Compared with the prior art, the present invention has the following beneficial effects:
[0045] The precursor material provided by this invention uses a nickel-rich material with high energy density as the core and a high-manganese material with high stability as the shell. Gradient doping of synergistic doping elements is carried out in the core structure near the shell (the doping amount in other parts of the core and the shell is not gradient-doped). While ensuring the cycling performance of the material, the capacity performance is optimized. Furthermore, gradient doping makes the bonding between the core and shell tighter, and the shell is less likely to fall off, which improves the stability of the core-shell structure cathode material and thus enhances the performance of the lithium-ion cathode material. Detailed Implementation
[0046] 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 are merely illustrative of the present invention and should not be construed as limiting the invention.
[0047] Example 1
[0048] This embodiment provides a cathode precursor material, wherein the precursor has a core-shell structure, and the core comprises Ni. 0.9 Co 0.05 Mn 0.05 The first nickel-cobalt-manganese precursor material of (OH)2, wherein the shell comprises Ni 0.45 Co 0.05 Mn 0.5 The second nickel-cobalt-manganese precursor material of (OH)2, wherein the precursor material is doped with Al element from the core to the surface; the Al element is doped in a gradient increasing manner in the core near the shell.
[0049] The preparation method of the positive electrode precursor material is as follows:
[0050] (1) Prepare a 2 mol / L aqueous solution A1 by mixing nickel salt, cobalt salt and manganese salt in a metal molar ratio of 90:5:5, and prepare a 2 mol / L aqueous solution A2 by mixing nickel salt, cobalt salt and manganese salt in a metal molar ratio of 45:5:50. Use 32% industrial liquid alkali as precipitant B and 15% ammonia water as complexing agent C.
[0051] Al2(SO4)3 and FeSO4 were mixed in a metal molar ratio of 1:1 to prepare a 0.1 mol / L aqueous solution. EDTA with a concentration of 0.1 mol / L was used as complexing agent D. The mixture was stirred evenly to prepare a metal ion complexing solution E.
[0052] Prepare the base solution and introduce N2 as a protective gas. Adjust the pH of the base solution to the range of 11.5-11.8, adjust the ammonia concentration to 6.0-6.5 g / L, control the temperature at 44℃, and adjust the stirring speed to 380 rpm.
[0053] (2) Solution A1, solution B, solution C and solution E are simultaneously pumped into the reactor at rates of 40 L / h, 13.8 L / h, 2 L / h and 8.1 L / h respectively. During the reaction stabilization period, the pH is controlled within 10.5, the ammonia concentration is controlled within the range of 5.0-6.5 g / L, the total alkali concentration is controlled within the range of 14 g / L, and the stirring speed is 380 rpm to carry out the co-precipitation reaction.
[0054] When the inner nickel-cobalt-manganese ternary precursor grows to a particle size of 4 μm (first stage co-precipitation reaction), the initial feed flow rates of the original nickel-cobalt-manganese solution, ammonia solution, liquid alkali solution, and doping solution remain unchanged, but the feed flow rate of the doping solution gradually increases at an increasing rate of 2 L / h until it stops when the ternary precursor grows to 7 μm (second stage co-precipitation reaction).
[0055] Solutions A2, B, C, and E were simultaneously pumped into the above mixture at rates of 40 L / h, 13.8 L / h, 2 L / h, and 8.1 L / h, respectively. Parameters such as pH, ammonia concentration in the supernatant, temperature, and stirring speed were kept stable. Feeding was stopped when the target particle size D50 reached 8 μm (third-stage co-precipitation reaction). The mixture was then centrifuged, washed, dried, sieved, iron removed, and packaged to obtain the core-shell structured gradient-doped cathode precursor material.
[0056] Example 2
[0057] This embodiment provides a cathode precursor material, wherein the precursor has a core-shell structure, and the core comprises Ni. 0.8 Co 0.1 Mn 0.1 The first nickel-cobalt-manganese precursor material of (OH)2, wherein the shell comprises Ni0.45 Co 0.1 Mn 0.45 The second nickel-cobalt-manganese precursor material of (OH)2 is doped with Zr element from the core to the surface; the Zr element is doped in a gradient increasing manner in the core near the shell.
[0058] The preparation method of the positive electrode precursor material is as follows:
[0059] (1) Prepare a 2 mol / L aqueous solution A1 by mixing nickel salt, cobalt salt and manganese salt in a metal molar ratio of 90:5:5, and prepare a 2 mol / L aqueous solution A2 by mixing nickel salt, cobalt salt and manganese salt in a metal molar ratio of 45:5:50. Use 32% industrial liquid alkali as precipitant B and 15% ammonia water as complexing agent C.
[0060] Al2(SO4)3 and FeSO4 were mixed in a metal molar ratio of 1:1 to prepare a 0.1 mol / L aqueous solution. EDTA with a concentration of 0.1 mol / L was used as complexing agent D. The mixture was stirred evenly to prepare a metal ion complexing solution E.
[0061] Prepare the base solution and introduce N2 as a protective gas. Adjust the pH of the base solution to the range of 11.5-11.8, adjust the ammonia concentration to 6.0-6.5 g / L, control the temperature at 44℃, and adjust the stirring speed to 380 rpm.
[0062] (2) Solution A1, solution B, solution C and solution E are simultaneously pumped into the reactor at rates of 40 L / h, 13.8 L / h, 2 L / h and 8.1 L / h respectively. During the reaction stabilization period, the pH is controlled within 10.5, the ammonia concentration is controlled within the range of 5.0-6.5 g / L, the total alkali concentration is controlled within the range of 14 g / L, and the stirring speed is 380 rpm to carry out the co-precipitation reaction.
[0063] When the inner nickel-cobalt-manganese ternary precursor grows to a particle size of 4 μm (first stage co-precipitation reaction), the initial feed flow rates of the original nickel-cobalt-manganese solution, ammonia solution, liquid alkali solution, and doping solution remain unchanged, but the feed flow rate of the doping solution gradually increases at an increasing rate of 0.2 L / h until it stops when the ternary precursor grows to 7 μm (second stage co-precipitation reaction).
[0064] Solutions A2, B, C, and E were simultaneously pumped into the above mixture at rates of 40 L / h, 13.8 L / h, 2 L / h, and 8.1 L / h, respectively. Parameters such as pH, ammonia concentration in the supernatant, temperature, and stirring speed were kept stable. Feeding was stopped when the target particle size D50 reached 8 μm (third-stage co-precipitation reaction). The mixture was then centrifuged, washed, dried, sieved, iron removed, and packaged to obtain the core-shell structured gradient-doped cathode precursor material.
[0065] Example 3
[0066] The difference between this embodiment and Embodiment 1 is that the doping elements in this embodiment include Al, Cu and Fe;
[0067] In the preparation method, in step (1): Al2(SO4)3, CuSO4 and FeSO4 are prepared into a 0.1 mol / L aqueous solution according to the metal molar ratio of 1:1:1, and EDTA with a concentration of 0.1 mol / L is used as complexing agent D. The mixture is stirred evenly to prepare a metal ion complexing solution E.
[0068] The remaining preparation methods and parameters are consistent with those in Example 1.
[0069] Example 4
[0070] This embodiment provides a cathode precursor material, wherein the precursor has a core-shell structure, and the core comprises Ni. 0.9 Co 0.05 Mn 0.05 The first nickel-cobalt-manganese precursor material of (OH)2, wherein the shell comprises Ni 0.45 Co 0.05 Mn 0.5 The second nickel-cobalt-manganese precursor material of (OH)2, wherein the precursor material is doped with Al element from the core to the surface; the Al element is doped in a gradient increasing manner in the core near the shell.
[0071] The preparation method of the positive electrode precursor material is as follows:
[0072] (1) Prepare a 2 mol / L aqueous solution A1 by mixing nickel salt, cobalt salt and manganese salt in a metal molar ratio of 90:5:5, and prepare a 2 mol / L aqueous solution A2 by mixing nickel salt, cobalt salt and manganese salt in a metal molar ratio of 45:5:50. Use 32% industrial liquid alkali as precipitant B and 15% ammonia water as complexing agent C.
[0073] Al2(SO4)3 and FeSO4 were mixed in a metal molar ratio of 1:1 to prepare a 0.1 mol / L aqueous solution. EDTA with a concentration of 0.1 mol / L was used as complexing agent D. The mixture was stirred evenly to prepare a metal ion complexing solution E.
[0074] Prepare the base solution and introduce N2 as a protective gas. Adjust the pH of the base solution to the range of 11.5-11.8, adjust the ammonia concentration to 6.0-6.5 g / L, control the temperature at 44℃, and adjust the stirring speed to 380 rpm.
[0075] (2) Solution A1, solution B, solution C and solution E are simultaneously pumped into the reactor at rates of 40 L / h, 13.8 L / h, 2 L / h and 8.1 L / h respectively. During the reaction stabilization period, the pH is controlled within 10.5, the ammonia concentration is controlled within the range of 5.0-6.5 g / L, the total alkali concentration is controlled within the range of 14 g / L, and the stirring speed is 380 rpm to carry out the co-precipitation reaction.
[0076] When the inner nickel-cobalt-manganese ternary precursor grows to a particle size of 4.4 μm (first stage co-precipitation reaction), the initial feed flow rates of the original nickel-cobalt-manganese solution, ammonia solution, liquid alkali solution, and doping solution remain unchanged, but the feed flow rate of the doping solution gradually increases at an increasing rate of 0.2 L / h until it stops when the ternary precursor grows to 7.6 μm (second stage co-precipitation reaction).
[0077] Solutions A2, B, C, and E were simultaneously pumped into the above mixture at rates of 40 L / h, 13.8 L / h, 2 L / h, and 8.1 L / h, respectively. Parameters such as pH, ammonia concentration in the supernatant, temperature, and stirring speed were kept stable. Feeding was stopped when the target particle size D50 reached 8 μm (third-stage co-precipitation reaction). The mixture was then centrifuged, washed, dried, sieved, iron removed, and packaged to obtain the core-shell structured gradient-doped cathode precursor material.
[0078] Example 5
[0079] This embodiment provides a cathode precursor material, wherein the precursor has a core-shell structure, and the core comprises Ni. 0.9 Co 0.05 Mn 0.05 The first nickel-cobalt-manganese precursor material of (OH)2, wherein the shell comprises Ni 0.45 Co 0.05 Mn 0.5 The second nickel-cobalt-manganese precursor material of (OH)2, wherein the precursor material is doped with Al element from the core to the surface; the Al element is doped in a gradient increasing manner in the core near the shell.
[0080] The preparation method of the positive electrode precursor material is as follows:
[0081] (1) Prepare a 2 mol / L aqueous solution A1 by mixing nickel salt, cobalt salt and manganese salt in a metal molar ratio of 90:5:5, and prepare a 2 mol / L aqueous solution A2 by mixing nickel salt, cobalt salt and manganese salt in a metal molar ratio of 45:5:50. Use 32% industrial liquid alkali as precipitant B and 15% ammonia water as complexing agent C.
[0082] Al2(SO4)3 and FeSO4 were mixed in a metal molar ratio of 1:1 to prepare a 0.1 mol / L aqueous solution. EDTA with a concentration of 0.1 mol / L was used as complexing agent D. The mixture was stirred evenly to prepare a metal ion complexing solution E.
[0083] Prepare the base solution and introduce N2 as a protective gas. Adjust the pH of the base solution to the range of 11.5-11.8, adjust the ammonia concentration to 6.0-6.5 g / L, control the temperature at 44℃, and adjust the stirring speed to 380 rpm.
[0084] (2) Solution A1, solution B, solution C and solution E are simultaneously pumped into the reactor at rates of 40 L / h, 13.8 L / h, 2 L / h and 8.1 L / h respectively. During the reaction stabilization period, the pH is controlled within 10.5, the ammonia concentration is controlled within the range of 5.0-6.5 g / L, the total alkali concentration is controlled within the range of 14 g / L, and the stirring speed is 380 rpm to carry out the co-precipitation reaction.
[0085] When the inner nickel-cobalt-manganese ternary precursor grows to a particle size of 4 μm (first stage co-precipitation reaction), the initial feed flow rates of the original nickel-cobalt-manganese solution, ammonia solution, liquid alkali solution, and doping solution remain unchanged, but the feed flow rate of the doping solution gradually increases at an increasing rate of 2 L / h until it stops when the ternary precursor grows to 6.8 μm (second stage co-precipitation reaction).
[0086] Solutions A2, B, C, and E were simultaneously pumped into the above mixture at rates of 40 L / h, 13.8 L / h, 2 L / h, and 8.1 L / h, respectively. Parameters such as pH, ammonia concentration in the supernatant, temperature, and stirring speed were kept stable. Feeding was stopped when the target particle size D50 reached 8 μm (third-stage co-precipitation reaction). The mixture was then centrifuged, washed, dried, sieved, iron removed, and packaged to obtain the core-shell structured gradient-doped cathode precursor material.
[0087] Example 6
[0088] The difference between this embodiment and embodiment 1 is that the particle size obtained by the first stage coprecipitation reaction in step (2) of this embodiment is 4.8 μm (60% of the final target particle size).
[0089] The remaining preparation methods and parameters are consistent with those in Example 1.
[0090] Example 7
[0091] The difference between this embodiment and embodiment 1 is that the particle size obtained by the second stage coprecipitation reaction in step (2) of this embodiment is 6.4 μm (80% of the final target particle size).
[0092] The remaining preparation methods and parameters are consistent with those in Example 1.
[0093] Example 8
[0094] The difference between this embodiment 1 and embodiment 1 is that in the second stage coprecipitation reaction process in step (2) of this embodiment, the feed flow rate of the doped solution E gradually increases at an increasing rate of 2.5 L / h.
[0095] The remaining preparation methods and parameters are consistent with those in Example 1.
[0096] Comparative Example 1
[0097] This comparative example provides a cathode precursor material that is not doped and has a non-core-shell structure, i.e., a pure core.
[0098] The preparation method includes the following steps:
[0099] (1) Prepare a 2 mol / L aqueous solution A1 by mixing nickel salt, cobalt salt, manganese salt and other metal salts in a metal molar ratio of 90:5:5, and use 32% industrial liquid alkali as precipitant B and 15% ammonia water as complexing agent C.
[0100] Prepare the base solution and introduce N2 as a protective gas. Adjust the pH of the base solution to 11.2-11.6, the ammonia concentration to 6-6.5 g / L, control the temperature at 42℃, and adjust the stirring speed to 380 rpm.
[0101] (2) Solution A, solution B and solution C are simultaneously pumped into the reactor at rates of 40 L / h, 13.8 L / h and 2 L / h respectively. During the reaction stabilization period, the pH is controlled within the range of 10.2-10.5, the ammonia concentration is controlled within the range of 6.5 g / L, the total alkali concentration is controlled within the range of 14 g / L, and the stirring speed is controlled within the range of 380 rpm to carry out the coprecipitation reaction. The entire reaction time is 90 h.
[0102] (3) After the D50 reaches 8μm, the feeding is stopped, and the product is centrifuged, washed, dried, sieved, iron removed, and packaged to obtain a high-nickel ternary precursor.
[0103] Comparative Example 2
[0104] The difference between this comparative example and Example 1 is that the dopant element Al in the cathode precursor material provided in this comparative example was not subjected to gradient doping, and the feed flow rate of the dopant solution remained constant throughout the entire preparation process.
[0105] The remaining preparation methods and parameters are consistent with those in Example 1.
[0106] Comparative Example 3
[0107] The difference between this comparative example and Example 1 is that the cathode precursor material in this comparative example is a non-core-shell structure, that is, the chemical formula of the core is maintained and the same Al gradient doping is performed as in Example 1.
[0108] In the preparation method, solution A2 is not prepared, and A1 is used as the main element solution throughout the entire preparation process.
[0109] The remaining preparation methods and parameters are consistent with those in Example 1.
[0110] The cathode precursor materials provided in Examples 1-8 and Comparative Examples 1-3 were mixed with lithium hydroxide in a mortar at a ratio of 1:1.05 and calcined at 850°C for 20 hours to obtain the cathode material.
[0111] Using the lithium-ion cathode materials provided in Examples 1-8 and Comparative Examples 1-3 as cathode active materials and lithium sheets as counter electrodes, coin cells were prepared.
[0112] The lithium-ion batteries provided in Examples 1-8 and Comparative Examples 1-3 were subjected to performance tests under the following conditions:
[0113] The initial discharge capacity and 100-cycle capacity retention rate were tested using a battery performance testing system (model: BTS05 / 10C8D-HP) from Shenghong Electric Co., Ltd. at a charge and discharge current of 0.5C.
[0114] The test results are shown in Table 1. Table 1 also shows the doping amount of the doping elements provided in Examples 1-8 and Comparative Examples 1-3.
[0115] Table 1
[0116]
[0117] The data from Examples 1 and 6 show that the particle size of the coprecipitation reaction in the first stage is too large, exceeding 55% of the target particle size, which is detrimental to the cyclic stability of the material.
[0118] The data from Examples 1 and 7 show that if the particle size of the coprecipitation reaction in the second stage is too small, less than 85% of the target particle size, it will affect the cycling performance of the material.
[0119] The data from Examples 1 and 8 show that if the rate of increase in the second-stage co-precipitation reaction is too fast, it will lead to uneven distribution of dopant elements and poor capacity and cycle performance.
[0120] As can be seen from the data results of Example 1 and Comparative Example 1, the precursor material provided by the present invention has a stable structure and achieves a balance between cycle performance and capacity.
[0121] The data results from Example 1 and Comparative Examples 2 and 3 show that neither pure core-shell structure nor pure gradient doping can achieve the requirements of high capacity and high cycling performance. In other words, the cathode precursor material provided by this invention achieves a synergistic effect.
[0122] In summary, the precursor material provided by this invention uses a nickel-rich material with high energy density as the core and a high-manganese material with high stability as the shell. At the same time, gradient doping of synergistic doping elements is carried out in the core structure near the shell (the doping amount in other positions of the core and the shell is not gradient-doped). While ensuring the cycling performance of the material, the capacity performance is optimized. In addition, gradient doping also makes the bonding between the core and the shell tighter, and the shell is not easy to fall off, which improves the stability of the core-shell structure cathode material, thereby improving the performance of lithium-ion cathode materials.
[0123] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.
Claims
1. A core-shell structured cathode precursor material, characterized in that, The core-shell structured cathode precursor material includes a first nickel-cobalt-manganese precursor core and a second nickel-cobalt-manganese precursor shell layer located on the surface of the precursor core. The core-shell structured cathode precursor material contains doping elements; the molar amount of nickel in the first nickel-cobalt-manganese precursor core accounts for ≥80% of the total molar amount of nickel-cobalt-manganese, and the doping element increases in a gradient near the shell layer of the first nickel-cobalt-manganese precursor core; the molar amount of manganese in the second nickel-cobalt-manganese precursor core accounts for ≥45% of the total molar amount of nickel-cobalt-manganese. The preparation method of the core-shell structured cathode precursor material includes the following steps: The first nickel-cobalt-manganese mixed salt solution, the precipitant solution, the first complexing agent solution and the dopant solution were added to the bottom solution in a parallel flow to carry out the first stage coprecipitation reaction and the second stage coprecipitation reaction in sequence. The dopant solution also includes a second complexing agent; After the second stage coprecipitation reaction is completed, the first nickel-cobalt-manganese mixed salt solution is replaced with the second nickel-cobalt-manganese mixed salt solution to carry out the third stage coprecipitation reaction, and the core-shell structured cathode precursor material is obtained. In the first nickel-cobalt-manganese mixed salt solution, the molar amount of nickel accounts for ≥80% of the total molar amount of nickel, cobalt, and manganese; the particle size of the reaction product of the first stage co-precipitation reaction is 45-55% of the final target particle size; during the second stage co-precipitation reaction, the feed flow rate of the dopant solution is gradually increased; the particle size of the reaction product of the second stage co-precipitation reaction is 85-95% of the final target particle size; and the molar amount of manganese in the second nickel-cobalt-manganese mixed salt solution accounts for ≥45% of the total molar amount of nickel, cobalt, and manganese.
2. The core-shell structured cathode precursor material according to claim 1, characterized in that, The total doping amount of the doping elements is 1000~5000ppm.
3. A method for preparing a core-shell structured cathode precursor material as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: The first nickel-cobalt-manganese mixed salt solution, the precipitant solution, the first complexing agent solution and the dopant solution were added to the bottom solution in a parallel flow to carry out the first stage coprecipitation reaction and the second stage coprecipitation reaction in sequence. The dopant solution also includes a second complexing agent; After the second stage coprecipitation reaction is completed, the first nickel-cobalt-manganese mixed salt solution is replaced with the second nickel-cobalt-manganese mixed salt solution to carry out the third stage coprecipitation reaction, and the core-shell structured cathode precursor material is obtained. In the first nickel-cobalt-manganese mixed salt solution, the molar amount of nickel accounts for ≥80% of the total molar amount of nickel, cobalt, and manganese; the particle size of the reaction product of the first stage co-precipitation reaction is 45-55% of the final target particle size; during the second stage co-precipitation reaction, the feed flow rate of the dopant solution is gradually increased; the particle size of the reaction product of the second stage co-precipitation reaction is 85-95% of the final target particle size; and the molar amount of manganese in the second nickel-cobalt-manganese mixed salt solution accounts for ≥45% of the total molar amount of nickel, cobalt, and manganese.
4. The method for preparing the core-shell structured cathode precursor material according to claim 3, characterized in that, The pH value of the base solution is 10-13.
5. The method for preparing the core-shell structured cathode precursor material according to claim 3, characterized in that, The concentration of ammonia in the base solution is 5~20g / L.
6. The method for preparing the core-shell structured cathode precursor material according to claim 3, characterized in that, The temperature of the base liquid is 40~80℃.
7. The method for preparing the core-shell structured cathode precursor material according to claim 3, characterized in that, The stirring rate of the base liquid is 200~500 rpm.
8. The method for preparing the core-shell structured cathode precursor material according to claim 3, characterized in that, During the second stage of the coprecipitation reaction, the feed flow rate of the dopant solution is increased in a gradient of 0.1~2 L / h.
9. The method for preparing the core-shell structured cathode precursor material according to claim 3, characterized in that, The preparation method includes the following steps: A first nickel-cobalt-manganese mixed salt solution, a precipitant solution, a first complexing agent solution, and a dopant solution containing a second complexing agent are added concurrently to the base solution to carry out a first-stage co-precipitation reaction. After the particle size of the reaction product of the first-stage co-precipitation reaction reaches 45-55% of the final target particle size, a second-stage co-precipitation reaction is carried out. During the second-stage co-precipitation reaction, the feed flow rate of the dopant solution is gradually increased at a rate of 0.1-2 L / h until the particle size of the reaction product of the second-stage co-precipitation reaction reaches 85-95% of the final target particle size, at which point the reaction ends. After the second stage coprecipitation reaction is completed, the first nickel-cobalt-manganese mixed salt solution is replaced with the second nickel-cobalt-manganese mixed salt solution to carry out the third stage coprecipitation reaction, and the core-shell structured cathode precursor material is obtained. In the first nickel-cobalt-manganese mixed salt solution, the molar amount of nickel accounts for ≥80% of the total molar amount of nickel, cobalt, and manganese; during the second stage co-precipitation reaction, the feed flow rate of the dopant solution increases gradually; and in the second nickel-cobalt-manganese mixed salt solution, the molar amount of manganese accounts for ≥45% of the total molar amount of nickel, cobalt, and manganese.
10. A lithium-ion cathode material, characterized in that, The lithium-ion cathode material is obtained by mixing and sintering a core-shell structured cathode precursor material as described in any one of claims 1 or 2 with a lithium source.
11. The lithium-ion cathode material according to claim 10, characterized in that, The sintering is carried out in an oxygen-containing atmosphere.
12. A lithium-ion battery, characterized in that, The lithium-ion battery includes the lithium-ion cathode material as described in claim 10 or 11.