Single-crystal micro-lithium-rich ultra-high-nickel layered oxide positive electrode material, preparation method and application thereof

Abstract

The invention discloses a single crystal type ultra-high nickel layered oxide positive electrode material, a preparation method and application of the positive electrode material in a high-performance lithium ion battery, and the preparation method of the positive electrode material comprises the following steps: mixing a lithium source, nickel cobalt manganese hydroxide and a trace fluorinated additive according to the ratio of (1.02-1.15): 1: (0.005-0.03), ball-milling into uniformly mixed powder, and drying the powder to obtain the single crystal type ultra-high nickel layered oxide positive electrode material. The preparation method comprises the following steps: carrying out first-stage calcination at 780-850 DEG C for 0.5-2 hours in an oxidizing atmosphere, carrying out second-stage calcination at 680-750 DEG C for 6-20 hours, and cooling to room temperature to obtain the product. By finely controlling synthesis conditions, the microstructure, chemical composition and chemical uniformity of the material are optimized. According to the single crystal type micro lithium-rich ultra-high nickel layered oxide positive electrode material prepared by the method, high single crystallization of the ultra-high nickel positive electrode material is realized, the structural stability and the electrochemical performance of the material are remarkably improved, and the material also has good repeatability and large-scale production potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and in particular relates to a single-crystal ultra-high nickel layered oxide positive electrode material and a preparation method thereof. Background Art

[0002] As the global demand for renewable energy and efficient energy storage systems continues to increase, lithium-ion batteries have become the first choice for electric vehicles, mobile electronic devices and energy storage solutions due to their high energy density, long life and relatively low environmental impact. Although the cathode materials currently on the market, such as lithium nickel cobalt manganese oxide (NCM) and lithium nickel cobalt aluminum oxide (NCA), have made certain progress in energy density and cycle performance, they still have problems such as structural instability caused by increased nickel content and cost and resource limitations. In addition, with the growing demand for electric vehicles and sustainable energy solutions, the pursuit of higher performance and more economical battery materials is also intensifying. In this context, the development of a new type of cathode material that aims to overcome the limitations of existing materials by increasing the nickel content without sacrificing the structural stability and cycle life of the battery has become an important goal in research and industry.

[0003] (Li Linsen, Wang Han, Wang Yong, etc., Chinese patent CN 115101745 A) The emergence of slightly lithium-rich lithium nickelate layered oxide cathode materials, with its unique chemical composition (Li 1+x TM 1-x O2, TM refers to Ni, Co, Mn) and structural characteristics effectively solve the key problems faced by traditional lithium nickelate layered positive electrode materials during use, especially the irreversible phase change and oxygen evolution problems on the surface. However, this type of material generally has a polycrystalline secondary spherical morphology. During the battery cycle, the anisotropic expansion and contraction of the primary particles induce intercrystalline stress, resulting in particle fragmentation and accelerated performance degradation. (Cheng Fangyi, Ding Guoyu, Liu Kuiming, etc., Chinese patent CN116282226A) Since there are no grain boundaries inside the single crystal type micro-lithium-rich lithium nickelate material, the structure is more stable in the crystal form, and it is not easy for particles to break during electrode pressing and electrochemical cycling. However, at present, this type of material is designed with a micro-lithium-rich structure by adopting a molten salt-assisted synthesis process, which requires water washing to remove excess lithium salts and secondary sintering to repair the surface structure of the material. Not only does it increase the process cost, but the highly oxidizing Ni 3+ Due to its high sensitivity to water, it is easy to form an inactive disordered rock salt phase on the material surface during the water washing process, which reduces the material's specific energy and stability. To address this problem, the present invention adopts a one-step water-free temperature-variable sintering synthesis process. Through the auxiliary design of a method using a slight excess lithium salt and a trace amount of fluorinated compound additives, it has developed a single-crystal ultra-high nickel cathode material with a specific energy of up to 880Wh / kg, providing a more economical and efficient solution for the preparation of high-energy-density lithium-ion battery cathode materials. Summary of the Invention

[0004] The present invention aims to address the deficiencies of the prior art and to provide a method for preparing a single-crystal, slightly lithium-rich, ultra-high nickel layered oxide, thereby resolving the problems of the prior art in terms of complex synthesis process and high process cost.

[0005] Preparation method

[0006] A nickel-cobalt-manganese ternary precursor is ball-milled with a lithium salt and a trace amount of a fluorine-containing compound. The molar ratio of the lithium salt to the ternary precursor is in the range of 1.0-1.15, and the molar ratio of the fluorine-containing compound to the nickel-cobalt-manganese ternary precursor is in the range of 0.5-5%. The ball mill rotates at a speed of 400-450 rpm for 6-10 hours. The ball-milled powder is then added to a corundum porcelain boat, which is covered and placed in a tubular furnace. Pure oxygen is introduced at a constant flow rate. The temperature is raised at a constant rate to a certain temperature. After maintaining the same temperature for a certain period of time, the temperature is lowered to room temperature at a constant rate.

[0007] The cooled powder is taken out, ground and crushed, and then sieved to obtain black powder, which is then vacuum-sealed in a plastic bag for storage.

[0008] The ternary precursor is Ni 95 Co4Mn1(OH)2; the lithium salts used are LiOH, LiOH·H2O, Li2CO3; the fluorine-containing compounds are KF, LiF, MgF2, AlF3, NH4F, ZrF4.

[0009] The calcination temperature is divided into two stages. The first stage temperature range is 750-850 degrees, the heating time is 0.5-2 hours, and the second stage is stable in the range of 680-740 degrees, the heating time is 6-20 hours, the heating / cooling rate is 2-10 degrees / minute, and the oxygen flow rate is 0.1-0.6L / min.

[0010] The temperature unit in the above steps is Celsius.

[0011] Compared to existing technologies, the single-crystal, slightly lithium-rich, ultra-high nickel layered oxide cathode material produced by this invention possesses a thermodynamically stable layered phase structure with an R-3m space group, effectively addressing the cycling stability deficiencies of conventional ultra-high nickel cathode materials. The material is characterized by low cost and high energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Synchrotron radiation XRD refinement results of Example 1;

[0013] Figure 2 Scanning electron microscope photographs of Example 1 and Comparative Example 1;

[0014] Figure 3 First-week charge and discharge curves of Example 1 and Comparative Example 1;

[0015] Figure 4 .Electrochemical charge and discharge test results of Example 1 and Comparative Example 1. DETAILED DESCRIPTION

[0016] Example 1

[0017] Ni 95 The molar ratio of Co4Mn1(OH)2 to LiOH and KF is 1:1.12:0.015. The mixture is weighed and placed in a ball mill. Ball mill beads 2-3 times the mass of the raw materials are added. The mixture is milled at 400 rpm for 30 minutes, left for 5 minutes, and repeated 15 times. The milled powder is added to a corundum boat, which is covered and placed in a tube furnace. Pure oxygen is introduced at a flow rate of 0.5 liters / minute. The temperature is raised to 800 degrees Celsius at a rate of 5 degrees / minute. After maintaining the temperature at 800 degrees Celsius for 0.5 hours, the temperature is lowered to 700 degrees Celsius at a rate of 5 degrees / minute. After maintaining the temperature at 700 degrees Celsius for 10 hours, the temperature is lowered to room temperature at a rate of 2 degrees / minute.

[0018] The cooled powder was taken out, ground and crushed, and passed through a 400-mesh sieve to obtain Product 1, which was vacuum-sealed in a plastic bag and stored for testing.

[0019] The precise elemental composition of Product 1 was determined by quantitative analysis using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). As shown in Table 1, the ratio of Li to transition metals was 1.06, indicating that the material was slightly lithium-rich. The crystal structure of Product 1 was analyzed using synchrotron X-ray diffraction ( Figure 1 ), confirmed that it has a layered structure,

[0020] The space group is R-3m. GSAS II was used to refine the XRD diffraction pattern. The calculated results are shown in Table 2. The Ni atoms occupy 7.42% of the Li sites, and the Li atoms occupy 3.78% of the Ni sites, indicating that the material is in a state of Li abundance.

[0021] The obtained product 1 was assembled into a button cell in an argon-protected glove box with lithium sheets, a separator, and an electrolyte (1M lithium hexafluorophosphate dissolved in a 3:1 volume ratio of ethyl methyl carbonate and fluoroethylene carbonate, with 0.05M lithium difluorooxalatoborate added as an additive). The battery was charged for two cycles at a rate of 0.1C / 0.1C within the voltage range of 4.3-2.8V and then subjected to a long-term cycle test at a rate of 1C / 1C. The charge and discharge curves of product 1 for the first week are shown in the figure. Figure 3 The discharge energy density is ∼880Wh / kg. The electrochemical cycling stability results are shown in Figure 4 .

[0022] Example 2

[0023] Ni 95 The molar ratio of Co4Mn1(OH)2 to LiOH and KF is 1:1.02:0.015. Weigh them and place them in a ball mill. Add ball mill beads 2-3 times the mass of the raw materials and mill them at 400 rpm for 30 minutes. Let them rest for 5 minutes and repeat 15 times. Add the milled powder to a corundum boat, cover it, and place it in a tube furnace. Add pure oxygen at a flow rate of 0.5 liters / minute. Raise the temperature to 800 degrees at a rate of 5 degrees / minute. After keeping it at 800 degrees for 0.5 hours, cool it down to 700 degrees at a rate of 5 degrees / minute. After keeping it at 700 degrees for 10 hours, cool it down to room temperature at a rate of 2 degrees / minute.

[0024] The cooled powder was then removed, ground, and passed through a 400-mesh sieve to obtain Product 2, which was then vacuum-sealed in a plastic bag and stored for testing. The precise elemental composition of Product 2 was quantitatively determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) (see Table 1).

[0025] Example 3

[0026] Ni 95 The molar ratio of Co4Mn1(OH)2 to LiOH and KF is 1:1.05:0.015. The mixture is weighed and placed in a ball mill. Ball mill beads 2-3 times the mass of the raw materials are added. The mixture is milled at 400 rpm for 30 minutes, left for 5 minutes, and repeated 15 times. The milled powder is added to a corundum boat, covered with a lid, and placed in a tube furnace. Pure oxygen is introduced at a flow rate of 0.5 liters / minute. The temperature is raised to 800 degrees Celsius at a rate of 5 degrees / minute. After being kept at 800 degrees Celsius for 0.5 hours, the temperature is lowered to 700 degrees Celsius at a rate of 5 degrees / minute. After being kept at 700 degrees Celsius for 10 hours, the temperature is lowered to room temperature at a rate of 2 degrees / minute.

[0027] The cooled powder was then removed, ground, and passed through a 400-mesh sieve to obtain Product 3, which was then vacuum-sealed in a plastic bag and stored for testing. The precise elemental composition of Product 3 was quantitatively determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) (see Table 1).

[0028] Example 4

[0029] Ni 95The molar ratio of Co4Mn1(OH)2 to LiOH and KF is 1:1.08:0.015. Weigh them and place them in a ball mill. Add ball mill beads 2-3 times the mass of the raw materials and mill them at 400 rpm for 30 minutes. Let them rest for 5 minutes and repeat 15 times. Add the milled powder to a corundum boat, cover it, and place it in a tube furnace. Add pure oxygen at a flow rate of 0.5 liters / minute. Raise the temperature to 800 degrees at a rate of 5 degrees / minute. After keeping it at 800 degrees for 0.5 hours, cool it down to 700 degrees at a rate of 5 degrees / minute. After keeping it at 700 degrees for 10 hours, cool it down to room temperature at a rate of 2 degrees / minute.

[0030] The cooled powder was then removed, ground, and passed through a 400-mesh sieve to obtain Product 4, which was then vacuum-sealed in a plastic bag and stored for testing. The precise elemental composition of Product 4 was quantitatively determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) (see Table 1).

[0031] Example 5

[0032] Ni 95 The molar ratio of Co4Mn1(OH)2 to LiOH and KF is 1:1.10:0.015. Weigh them and place them in a ball mill. Add ball mill beads 2-3 times the mass of the raw materials and mill them at 400 rpm for 30 minutes. Let them rest for 5 minutes and repeat 15 times. Add the milled powder to a corundum boat, cover it, and place it in a tube furnace. Add pure oxygen at a flow rate of 0.5 liters / minute. Raise the temperature to 800 degrees at a rate of 5 degrees / minute. After keeping it at 800 degrees for 0.5 hours, cool it down to 700 degrees at a rate of 5 degrees / minute. After keeping it at 700 degrees for 10 hours, cool it down to room temperature at a rate of 2 degrees / minute.

[0033] The cooled powder was then removed, ground, and passed through a 400-mesh sieve to obtain Product 5, which was then vacuum-sealed in a plastic bag and stored for testing. The precise elemental composition of Product 5 was quantitatively determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) (see Table 1).

[0034] Example 6

[0035] Ni 95The molar ratio of Co4Mn1(OH)2 to LiOH and KF is 1:1.12:0.01. Weigh them and place them in a ball mill. Add ball mill beads 2-3 times the mass of the raw materials and mill them at 400 rpm for 30 minutes. Let them rest for 5 minutes and repeat 15 times. Add the milled powder to a corundum boat, cover it, and place it in a tube furnace. Add pure oxygen at a flow rate of 0.5 liters / minute. Raise the temperature to 800 degrees at a rate of 5 degrees / minute. After keeping it at 800 degrees for 0.5 hours, cool it down to 700 degrees at a rate of 5 degrees / minute. After keeping it at 700 degrees for 10 hours, cool it down to room temperature at a rate of 2 degrees / minute.

[0036] The cooled powder was taken out, ground and crushed, and passed through a 400-mesh sieve to obtain Product 6, which was vacuum-sealed in a plastic bag and stored for testing.

[0037] Example 7

[0038] Ni 95 The molar ratio of Co4Mn1(OH)2 to LiOH and KF is 1:1.12:0.03. The mixture is weighed and placed in a ball mill. Ball mill beads 2-3 times the mass of the raw materials are added. The mixture is milled at 400 rpm for 30 minutes, left for 5 minutes, and repeated 15 times. The milled powder is added to a corundum boat, which is covered and placed in a tube furnace. Pure oxygen is introduced at a flow rate of 0.5 liters / minute. The temperature is raised to 800 degrees Celsius at a rate of 5 degrees / minute. After maintaining the temperature at 800 degrees Celsius for 0.5 hours, the temperature is lowered to 700 degrees Celsius at a rate of 5 degrees / minute. After maintaining the temperature at 700 degrees Celsius for 10 hours, the temperature is lowered to room temperature at a rate of 2 degrees / minute.

[0039] The cooled powder was taken out, ground and crushed, and passed through a 400-mesh sieve to obtain Product 7, which was vacuum-sealed in a plastic bag and stored for testing.

[0040] Example 8

[0041] Ni 95 The ratio of the amount of substance between Co4Mn1(OH)2, LiOH and KF is 1:1.12:0.015. The fully ground and mixed powder is added into the corundum porcelain boat, covered with the lid, and placed in a tube furnace. Pure oxygen is introduced at a flow rate of 0.5 liters / minute, and the temperature is raised to 800 degrees at a rate of 5 degrees / minute. After keeping at 800 degrees for 1 hour, the temperature is lowered to 750 degrees at a rate of 5 degrees / minute. After keeping at 750 degrees for 10 hours, the temperature is lowered to room temperature at a rate of 2 degrees / minute.

[0042] The cooled powder was taken out, ground and crushed, and passed through a 400-mesh sieve to obtain Product 8, which was vacuum-sealed in a plastic bag and stored for testing.

[0043] Example 9

[0044] Ni 95 The molar ratio of Co₄Mn₁₁(OH)₂ to LiOH and KF was 1:1.12:0.015. The thoroughly ground and mixed powder was added to a corundum boat, which was then covered and placed in a tube furnace. Pure oxygen was introduced at a rate of 0.5 L / min. The temperature was raised to 850°C at a rate of 5°C / min. After holding at 850°C for 1 hour, the temperature was lowered to 750°C at a rate of 5°C / min. After holding at 750°C for 10 hours, the temperature was lowered to room temperature at a rate of 2°C / min. The cooled powder was removed, ground, and passed through a 400-mesh sieve to obtain Product 9. The product was then vacuum-sealed in a plastic bag and stored for testing.

[0045] Example 10

[0046] Ni 95 The ratio of the amount of substance between Co4Mn1(OH)2, LiOH and KF is 1:1.12:0.015. The fully ground and mixed powder is added into the corundum porcelain boat, covered with the lid, and placed in a tube furnace. Pure oxygen is introduced at a flow rate of 0.5 liters / minute, and the temperature is raised to 850 degrees at a rate of 5 degrees / minute. After keeping at 850 degrees for 1.5 hours, the temperature is lowered to 700 degrees at a rate of 5 degrees / minute. After keeping at 700 degrees for 10 hours, the temperature is lowered to room temperature at a rate of 2 degrees / minute.

[0047] The cooled powder was taken out, ground and crushed, and passed through a 400-mesh sieve to obtain product 10, which was vacuum-sealed in a plastic bag and stored for testing.

[0048] Example 11

[0049] Ni 95 The molar ratio of Co4Mn1(OH)2 to LiOH and MgF2 is 1:1.12:0.01. Weigh them and place them in a ball mill. Add ball mill beads 2-3 times the mass of the raw materials and mill them at 400 rpm for 30 minutes. Let them rest for 5 minutes and repeat 15 times. Add the milled powder to a corundum boat, cover it, and place it in a tube furnace. Raise the temperature to 800°C at a rate of 5°C / min. After keeping it at 800°C for 0.5 hours, cool it down to 700°C at a rate of 5°C / min. After keeping it at 700°C for 10 hours, cool it down to room temperature at a rate of 2°C / min.

[0050] The cooled powder was taken out, ground and crushed, and passed through a 400-mesh sieve to obtain product 11, which was vacuum-sealed in a plastic bag and stored for testing.

[0051] Example 12

[0052] Ni 95The molar ratio of Co4Mn1(OH)2 to LiOH and NH4F is 1:1.12:0.01. Weigh them and place them in a ball mill. Add ball mill beads 2-3 times the mass of the raw materials and mill them at 400 rpm for 30 minutes. Let them rest for 5 minutes and repeat 15 times. Add the milled powder to a corundum boat, cover it, and place it in a tube furnace. Heat it to 800°C at a rate of 5°C / min. After keeping it at 800°C for 1 hour, cool it down to 700°C at a rate of 5°C / min. After keeping it at 700°C for 10 hours, cool it down to room temperature at a rate of 2°C / min.

[0053] The cooled powder was taken out, ground and crushed, and passed through a 400-mesh sieve to obtain product 12, which was vacuum-sealed in a plastic bag and stored for testing.

[0054] Comparative Example 1

[0055] Ni 95 The ratio of the amount of substance between Co4Mn1(OH)2 and LiOH is 1:1.02. Weigh the powder that is fully ground and mixed, add it into the corundum porcelain boat, cover it with the lid, and put it into the tubular furnace. Pass pure oxygen at a flow rate of 0.5 liters / minute, and heat it to 800 degrees at a rate of 5 degrees / minute. After keeping it at 800 degrees for 0.5 hours, cool it down to 700 degrees at a rate of 5 degrees / minute. After keeping it at 700 degrees for 10 hours, cool it to room temperature at a rate of 2 degrees / minute.

[0056] The cooled powder was then removed, ground, and passed through a 400-mesh sieve to obtain Comparative Product 1. This was then vacuum-sealed in a plastic bag and stored for testing. The precise elemental composition of Comparative Product 1 was quantitatively determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) (see Table 1).

[0057] Product 1 was assembled into a button cell with a lithium sheet, a separator, and an electrolyte (1M lithium hexafluorophosphate dissolved in a 3:1 volume ratio of ethyl methyl carbonate and fluoroethylene carbonate, with 0.05M lithium difluorooxalatoborate added as an additive) in an argon atmosphere glove box. The battery was charged and discharged at 0.1C / 0.1C in the voltage range of 4.3-2.8V. The initial charge and discharge curve is as follows: Figure 3 As shown (named as comparative example 1). The long cycle performance evaluation test was carried out at a charge and discharge rate of 1C / 1C, and the test results are shown as follows Figure 4 shown.

[0058] Table 1. Quantitative analysis results of elemental composition of Examples and Comparative Examples

[0059] Sample name Li (atomic %) Ni (atomic %) Co(atomic%) Mn (atomic %) Example 1 1.060 0.890 0.040 0.010 Example 2 0.985 0.965 0.040 0.010 Example 3 1.020 0.920 0.040 0.010 Example 4 1.040 0.910 0.040 0.010 Comparative Example 1 0.980 0.970 0.040 0.010

[0060] Table 2. Quantitative analysis results of elemental composition of comparative examples

[0061] atom Placeholder Refined atomic ratio Li1 3a 0.9622 Ni2 3a 0.0378 Ni1 3b 0.9258 Co1 3b 0.0400 Mn1 3b 0.0100 Li2 3b 0.07420 O2 6c 2.0000

Claims

1. A single crystal slightly lithium-rich ultra-high nickel layered oxide positive electrode material, characterized in that: The method for preparing the positive electrode material comprises the following steps: (1) Weighing a lithium source, nickel-cobalt-manganese hydroxide, and a fluorine-containing compound in proportion, wherein the molar ratio of the lithium source to the nickel-cobalt-manganese hydroxide is 1.02-1.15, and the molar ratio of the fluorine-containing compound to the nickel-cobalt-manganese hydroxide is 0.005-0.03; (2) ball-milling the raw materials weighed in proportion in (1) for 6-15 hours to form a uniform powder; (3) The powder obtained by ball milling in step (2) is placed in a tubular furnace and calcined in an oxidizing atmosphere; the calcination temperature is divided into two stages, the first stage temperature range is 780-850 degrees, the heating time is 0.5-2 hours, the second stage temperature range is 680-750 degrees, the heating time is 6-20 hours, and the temperature is cooled to room temperature to obtain the product. The calcination heating / cooling rate is 2-10 degrees / minute, and the oxygen flow rate is 0.1-0.6 L / min to obtain the product.

2. The method for preparing the single crystal slightly lithium-rich ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: The molar ratio of the lithium source to the nickel-cobalt-manganese hydroxide is 1.02-1.12, and the molar ratio of the fluorine-containing compound to the nickel-cobalt-manganese hydroxide is 0.01-0.

03.

3. The method for preparing the single crystal slightly lithium-rich ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: During ball milling, add ball milling beads 2-3 times the mass of the raw materials into the ball mill jar, rotate at 400-450 rpm, mill for 30 minutes each time, let it rest for 5 minutes, and repeat several times.

4. The method for preparing the single crystal slightly lithium-rich ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: In step (3), the first calcination temperature is 800 degrees, the heating time is 0.5 hours, the second stabilization range is 700 degrees, the heating time is 10 hours, the calcination heating / cooling rate is 5 degrees / minute, and the oxygen flow rate is 0.5 L / min.

5. The method for preparing the single crystal slightly lithium-rich ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: The lithium source is one or more of LiOH, LiOH·H2O, and Li2CO3.

6. The method for preparing the single crystal slightly lithium-rich ultra-high nickel layered oxide positive electrode material according to claim 1, characterized in that: The fluorine-containing compound is one or more of KF, LiF, MgF2, AlF3, NH4F, and ZrF4.

7. The single-crystal slightly lithium-rich ultra-high nickel layered oxide positive electrode material prepared according to the method for preparing a single-crystal slightly lithium-rich ultra-high nickel layered oxide positive electrode material according to any one of claims 1 to 6, characterized in that: The chemical formula of the positive electrode material is Li 1+x Ni 0.95-x Co 0.04 Mn 0.01 O2, wherein 0.01≤ x≤0.10, the space group of the positive electrode material is R- m, highly single crystal.

8. Use of the single-crystalline slightly lithium-rich ultra-high nickel layered oxide positive electrode material prepared according to the method for preparing the single-crystalline slightly lithium-rich ultra-high nickel layered oxide positive electrode material according to any one of claims 1 to 6 in a lithium battery.

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