A rate type low cobalt content ternary positive electrode material, a preparation method thereof and application thereof

Abstract

The application discloses a nickel-cobalt-manganese ternary positive electrode material, which is characterized by accurate regulation of internal hole volume ratio, material specific surface area, true density, median particle size D v50 , Young's modulus, average size of one particle in each direction, crystal structure parameters and other parameters, so that the ternary material has the best rate performance while the cobalt content is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the positive electrode material of lithium secondary battery, especially the positive electrode material preparation field of lithium ion battery, more particularly, a kind of particle high nickel positive electrode material, its preparation method and application. BACKGROUND

[0002] Since the advent of lithium ion secondary battery, with its high discharge specific capacity, good cycle stability, excellent high-low temperature performance and environmental friendly characteristics, it has been applied in all aspects of people's life. With the rapid development of new energy industry, power battery has put forward higher requirements on cost, energy density, safety and cycle life. With the continuous rise of raw material prices, conventional lithium ion battery also faces the challenge of high cost.

[0003] At present, the positive electrode material mainly includes LiCoO2, LiNiO2, LiMnO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 2O2, LiNi 0.5 Co 0.2 Mn 0.3 2O2, LiNi 0.8 Co 0.2 2O2, spinel structure LiMn2O4, LiNi 0.5 Mn 1.5 4, olivine structure LiFePO4 and the like. With the increasing demand of market for battery material cost reduction, it is urgent to develop lithium ion battery with high capacity, high rate and low cost. Lithium cobaltate positive electrode material is easy to synthesize, has excellent cycle performance and high compaction density, and is one of the materials used for commercialization earliest, but due to the price of lithium cobaltate and poor structure stability, the application of lithium cobaltate in new energy field is limited.

[0004] Ternary material LiNi x Co y Mn 1-x-y 2O2, especially the multi-element material (x≥0.6) with higher nickel content has the advantages of high capacity, excellent cycle performance and excellent kinetics performance, but due to the high price of cobalt, the raw material cost of nickel-cobalt-manganese ternary material is too high, so how to reduce the cobalt content while ensuring the kinetics performance of ternary material becomes a research hotspot. SUMMARY

[0005] Therefore, the present application discloses a spherical particle nickel-cobalt-manganese ternary positive electrode material and a preparation method thereof. The material is precisely controlled in terms of internal pore volume ratio of ternary positive electrode material, specific surface area of material, true density, median particle size D v50By adjusting parameters such as Young's modulus, average size of primary particles in all directions, and crystal structure parameters, the ternary material achieves optimal rate performance while reducing cobalt content.

[0006] To address the aforementioned problems, this invention provides a nickel-cobalt-manganese ternary cathode material, a method for preparing the material, comprising its use as a cathode in a lithium secondary battery, and a lithium secondary battery including the cathode.

[0007] In a first aspect, the present invention provides a nickel-cobalt-manganese ternary cathode material, which is represented by the following formula: Li a Ni x Co y Mn z M b N c O 2+d Where 0.9 < a ​​< 1.2, 0.6 ≤ x < 1, 0 < y < 0.2, 0 < z < 0.4, 0 ≤ b < 0.1, 0 ≤ c < 0.1, 0 ≤ d < 0.1; M is selected from one or more elements such as Mg, Ti, Zr, Sr, Y, Zn, etc., and N is selected from one or more elements such as Al, Ce, B, W, Si, etc.

[0008] The nickel-cobalt-manganese ternary cathode material is in the form of spherical particles, and the core of the spherical particle-shaped nickel-cobalt-manganese ternary cathode material has a hollow structure; the volume V of its hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 Between 0.005:1 and 0.025:1; its specific surface area S 50 The ratio of the specific surface area S of the spherical, particulate nickel-cobalt-manganese ternary cathode material, as measured by the BET method, is between 0.35 and 0.6; where S 50 S is calculated using the following formula: 50 =[4π(D v50 / 2) 2 ] / [ρ×4 / 3π(D v50 / 2) 3 ]; where ρ is the true density of the spherical particle-shaped nickel-cobalt-manganese ternary cathode material measured by a true density meter, and its value is between 4.4 and 4.7 g / cm³. 3 Between; the median particle size D of spherical nickel-cobalt-manganese ternary cathode material v50 Its surface area (μm) is between 4 and 7 μm, and its specific surface area S(m 2 / g) is between 0.4 and 0.7m 2 Between / g;

[0009] Preferably, the spherical particle-shaped nickel-cobalt-manganese ternary cathode material is composed of secondary particles formed by the stacking of primary particles, with a median particle size D. v50 The spherical secondary particles have a Young's modulus E of the primary particles on their surface. v50 The pressure is between 150 and 350 GPa, preferably between 220 and 300 GPa; where the diameter is D v10 The spherical secondary particles have a Young's modulus of E for the primary particles on their surface. v10 The diameter is D v90 The spherical secondary particles have a Young's modulus E of the primary particles on their surface. v90 And satisfy E v10 / E v90 Between 0.95 and 1.05;

[0010] Preferably, the particle-shaped nickel-cobalt-manganese ternary cathode material has a crystal structure space group of R_3_m hexagonal phase, and the (104) crystal plane size D104 in its XRD pattern is between 50 and 90 nm.

[0011] Preferably, the spherical particle-shaped nickel-cobalt-manganese ternary cathode material is a secondary particle formed by the stacking of primary particles, and the average length of the primary particles on the surface of the secondary particles is between 250 mm and 500 mm in any direction.

[0012] Preferably, in the particulate nickel-cobalt-manganese ternary cathode material, the source of element M is an oxide of element M, preferably one or more of MgO, TiO2, ZrO2, SrO, Y2O3, and ZnO, and the source of element N is one or more of oxides of element N such as Al2O3, CeO2, B2O3, WO3, and SiO2.

[0013] According to a second aspect of the present invention, a method for preparing the spherical particle-shaped nickel-cobalt-manganese ternary cathode material according to the present invention is provided, comprising the following steps:

[0014] (1) Mix 1-2 mol / L NiSO4, CoSO4, and MnSO4 aqueous solutions evenly according to their respective molar ratios. Add the mixture to a 0.1-1 mol / L NH3·H2O and a 5-12 mol / L NaOH aqueous solution at a feed rate of 450-550 L / h. By continuously adding NaOH solution, control the pH at 11.4-11.9 during the nucleation stage and the nucleation time at 20-60 min. During the crystal growth stage, control the pH at 11.0-11.5 and stir under N2 conditions to obtain a co-precipitation reaction of particulate metal hydroxide precursor.

[0015] (2) The metal oxide precursor mixture obtained in step (1) is mixed with LiOH·H2O and the oxide of element M at a molar ratio of (Ni+Co+Al) / Li / M of 1:0.95:0.001 to 1:1.15:0.01, heated to 600-1000℃, and calcined in an oxidizing atmosphere for 5-20 hours to obtain a calcined Li. a Ni x Co y Mn z M b O 2+d ;

[0016] (3) The water-washed material Li obtained in step (2) a Ni x Co y Mn z M b O 2+d The Ni+Co+Mn) / N oxide is mixed uniformly at a molar ratio of (Ni+Co+Mn) / N of 1:0.001 to 1:0.1, heated to 200-700℃, and calcined in an oxidizing atmosphere for 3-15 hours to obtain the secondary calcined material Li. a Ni x Co y Mn z M b N c O 2+d ;

[0017] The definitions of M, N, x, y, z, a, b, and d are the same as those in the previous text.

[0018] The nickel salt is selected from one or more of nickel sulfate, nickel nitrate, and nickel chloride; preferably, the concentration of the nickel salt is 1-2 mol / L.

[0019] The cobalt salt is selected from one or more of cobalt sulfate, cobalt nitrate, and cobalt chloride; preferably, the concentration of the cobalt salt is 1-2 mol / L.

[0020] The manganese salt is selected from one or more of manganese sulfate, manganese nitrate and manganese chloride; preferably, the concentration of the manganese salt is 1-2 mol / L.

[0021] The aqueous solution of the alkali is selected from NH3·H2O or a mixed aqueous solution of alkali metal hydroxide, preferably a mixed aqueous solution of NH3·H2O and alkali metal hydroxide, with a concentration of 0.1 to 5 mol / L, preferably 0.2 to 2 mol / L, and the alkali metal hydroxide is preferably NaOH or KOH.

[0022] The oxide material containing M is selected from one or more of MgO, TiO2, ZrO2, SrO, Y2O3, and ZnO, and the source of N element is one or more of N element oxides such as Al2O3, CeO2, B2O3, WO3, and SiO2.

[0023] The average particle size D of the particulate metal hydroxide precursor mixture v50 Its thickness is 3.5–7 μm, and its specific surface area is 3–10 m². 2 / g.

[0024] According to a third aspect of the present invention, a positive electrode for a lithium secondary battery is provided, comprising the spherical particle-shaped nickel-cobalt-manganese ternary positive electrode material described in the present invention.

[0025] According to a fourth aspect of the present invention, a lithium secondary battery is provided, comprising a positive electrode as described in the present invention. Attached Figure Description

[0026] Figure 1 To show a scanning electron microscope image of the surface of the spherical particle-shaped nickel-cobalt-manganese ternary cathode material prepared in Example 1 of the present invention.

[0027] Figure 2 To show cross-sectional scanning electron microscope (SEM) images of the spherical nickel-cobalt-manganese ternary cathode materials prepared in Comparative Example 4, Example 1, and Comparative Example 3 of the present invention. Detailed Implementation

[0028] The present invention will be further illustrated by the following embodiments, but the scope of protection of the present invention is not limited to the listed embodiments.

[0029] Analytical methods and evaluation methods

[0030] (1) Morphology, median particle size, true density, specific surface area and crystal structure were analyzed and tested using a scanning electron microscope (SEM) (S-4800, Hitachi), a Malvern 3000 laser particle size analyzer, an Ultrapyc 5000 true density analyzer, a Best 3H-2000BET-A nitrogen adsorption specific surface area analyzer and a Malvern Panaco Aeris X-ray diffractometer.

[0031] (2) Initial discharge specific capacity:

[0032] The initial discharge specific capacity was set as follows: After the 2032 coin-shaped battery was made (see Example 1 for the manufacturing process), it was placed for about 24 hours. After the open circuit voltage (OCV) stabilized, the test temperature was adjusted to 25°C, the rate current for the positive electrode was set to 0.2C, and it was charged until the stop voltage was 4.25V. After resting for 1 hour, it was discharged until the capacity was reached when the stop voltage was 2.5V.

[0033] (3) Capacity retention rate after 30 laps:

[0034] The method for calculating the capacity retention rate after 30 laps is as follows:

[0035] Discharge specific capacity of the 30th cycle ÷ Discharge specific capacity of the 1st cycle × 100%

[0036] (4) 2C / 0.2C rate performance (%):

[0037] The calculation method for 2C / 0.2C rate performance is as follows:

[0038] 2C discharge specific capacity ÷ 0.2C discharge specific capacity × 100%.

[0039] (4) 2C / 0.2C rate performance (%)

[0040] Example 1:

[0041] (1) A 2 mol / L aqueous solution of NiSO4, CoSO4, and MnSO4 was mixed uniformly at a molar ratio of Ni:Co:Mn = 60:10:30. This mixture was then added to a 0.3 mol / L aqueous solution of NH3·H2O and 10 mol / L NaOH at a feed rate of 500 L / h. By continuously adding NaOH solution, the pH was controlled at 11.6 during the nucleation stage, and the nucleation time was controlled at 30 min. During the crystal growth stage, the pH was controlled at 11.1–11.2, and the mixture was stirred under N2 conditions for 80 hours of co-precipitation, yielding an average particle size D50 of 5.0 μm and a specific surface area of ​​7.0 m². 2 / g of particulate metal hydroxide precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)2;

[0042] (2) Take the Ni obtained in step (1) 0.6 Co 0.1 Mn 0.3 (OH)2 and Li2CO3 are mixed evenly at a molar ratio of (Ni+Co+Mn):Li of 1:1;

[0043] (3) Weigh 4 kg of the uniformly mixed raw material mixture obtained in step (2) and fill it into each mullite-cordierite sagger (sagger size 330mm*330mm*100mm). Then place the saggers in a roller kiln in a 4-row, 2-layer arrangement and calcine them under an oxidizing atmosphere. The temperature is raised directly from room temperature to 850℃ at a heating rate of 4℃ / min and held for 8 hours. After cooling, the product Li is obtained by crushing and sieving. 1.0 Ni 0.6 Co 0.1 Mn 0.3 O2. The average particle size D of the above finished materials v50 Its diameter is 5.7 μm and its specific surface area is 0.55 m². 2 / g, true density is 4.65g / cm³ 3 The ratio of the median particle size sphere specific surface area to the finished product specific surface area, S 50 For a spherical particle with S = 0.39 and a diameter equal to the median particle size, the volume V of the hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 =0.009;

[0044] (4) Assemble the finished product obtained in step (3) into a battery and conduct charge-discharge tests at 25°C. The battery assembly method is as follows: Mix 52.5 mg of the obtained spherical granular nickel-cobalt-manganese ternary material, 15 mg of acetylene black and 7.5 mg of polyvinylidene fluoride (PVDF), and press it into a diameter of 11 mm and a thickness of 100 μm at a pressure of 100 MPa to make a positive electrode sheet. Dry the prepared positive electrode sheet in a vacuum dryer at 120°C for 12 hours, and then use the positive electrode sheet to make a 2032 type coin battery in an Ar atmosphere glove box with a dew point of -80°C. The negative electrode uses lithium metal with a diameter of 17 mm and a thickness of 1 mm. The electrolyte uses an equal mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) with 1 M LiPF6 as the supporting electrolyte. The separator uses a polyethylene porous membrane with a membrane thickness of 25 μm. In addition, the 2032 battery has a gasket and a wave-shaped gasket. It is assembled into a coin-shaped battery by a positive electrode shell and a negative electrode shell, and its electrochemical performance is tested.

[0045] Example 2:

[0046] (1) A 2 mol / L aqueous solution of NiSO4, CoSO4, and MnSO4 was mixed uniformly at a molar ratio of Ni:Co:Mn = 65:5:30. The mixture was then added to a 0.35 mol / L aqueous solution of NH3·H2O and 10 mol / L NaOH at a feed rate of 500 L / h. The pH was controlled at 11.7 during the nucleation stage by continuously adding NaOH solution, and the nucleation time was controlled at 40 min. During the crystal growth stage, the pH was controlled at 11.1–11.2, and the mixture was stirred under N2 conditions for 80 hours of co-precipitation reaction, yielding an average particle size D50 of 5.0 μm and a specific surface area of ​​6.5 m². 2 / g of particulate metal hydroxide precursor Ni 0.65 Co 0.05 Mn 0.3 (OH)2;

[0047] (2) Take the Ni obtained in step (1) 0.65 Co 0.05 Mn 0.30 (OH)2 and Li2CO3 are mixed evenly at a molar ratio of (Ni+Co+Mn):Li of 1:1;

[0048] (3) Weigh 4 kg of the uniformly mixed raw material mixture obtained in step (2) and fill it into each mullite-cordierite sagger (sagger size 330mm*330mm*100mm). Then place the saggers in a roller kiln in a 4-row, 2-layer arrangement and calcine them under an oxidizing atmosphere. The temperature is raised directly from room temperature to 840℃ at a heating rate of 4℃ / min and held for 10 hours. After cooling, the product Li is obtained by crushing and sieving. 1.0 Ni 0.65 Co 0.05 Mn 0.30 O2. The average particle size D of the above finished materials v50 Its thickness is 5.5 μm, and its specific surface area is 0.58 m². 2 / g; true density is 4.64g / cm³ 3 The ratio of the median particle size sphere specific surface area to the finished product specific surface area, S 50 For a spherical particle with S = 0.41 and a diameter equal to the median particle size, the volume V of the hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 =0.010;

[0049] The other steps are the same as in Example 1;

[0050] Example 3:

[0051] (1) A 2 mol / L aqueous solution of NiSO4, CoSO4, and MnSO4 was mixed uniformly at a molar ratio of Ni:Co:Mn = 60:10:30. This mixture was then added to a 0.3 mol / L aqueous solution of NH3·H2O and 10 mol / L NaOH at a feed rate of 500 L / h. By continuously adding NaOH solution, the pH was controlled at 11.6 during the nucleation stage, and the nucleation time was controlled at 30 min. During the crystal growth stage, the pH was controlled at 11.1–11.2, and the mixture was stirred under N2 conditions for 80 hours of co-precipitation, yielding an average particle size D50 of 5.0 μm and a specific surface area of ​​7.0 m². 2 / g of particulate metal hydroxide precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)2;

[0052] (2) Take the Ni obtained in step (1) 0.6 Co 0.1 Mn 0.3 (OH)2, Li2CO3, and ZrO2 are mixed evenly according to the molar ratio of (Ni+Co+Mn):Li:Zr of 1:1:0.002;

[0053] (3) Weigh 4 kg of the uniformly mixed raw material mixture obtained in step (2) and fill it into each mullite-cordierite sagger (sagger size 330mm*330mm*100mm). Then place the saggers in a roller kiln in a 4-row, 2-layer arrangement and calcine them under an oxidizing atmosphere. The temperature is raised directly from room temperature to 850℃ at a heating rate of 4℃ / min and held for 8 hours. After cooling, the product Li is obtained by crushing and sieving. 1.0 Ni 0.6 Co 0.1 Mn 0.3 Zr 0.002 O 2.004 The average particle size D of the above finished materials v50 Its diameter is 5.7 μm and its specific surface area is 0.55 m². 2 / g; true density is 4.65g / cm³ 3 The ratio of the median particle size sphere specific surface area to the finished product specific surface area, S 50 For a spherical particle with S = 0.41 and a diameter equal to the median particle size, the volume V of the hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 =0.009;

[0054] The other steps are the same as in Example 1;

[0055] Example 4:

[0056] (1) A 2 mol / L aqueous solution of NiSO4, CoSO4, and MnSO4 was mixed uniformly at a molar ratio of Ni:Co:Mn = 60:10:30. This mixture was then added to a 0.3 mol / L aqueous solution of NH3·H2O and 10 mol / L NaOH at a feed rate of 500 L / h. By continuously adding NaOH solution, the pH was controlled at 11.6 during the nucleation stage, and the nucleation time was controlled at 30 min. During the crystal growth stage, the pH was controlled at 11.1–11.2, and the mixture was stirred under N2 conditions for 80 hours of co-precipitation, yielding an average particle size D50 of 5.0 μm and a specific surface area of ​​7.0 m². 2 / g of particulate metal hydroxide precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)2;

[0057] (2) Take the Ni obtained in step (1) 0.6 Co 0.1 Mn 0.3 (OH)2, Li2CO3, and TiO2 are mixed evenly according to the molar ratio of (Ni+Co+Mn):Li:Ti of 1:1:0.002;

[0058] (3) Weigh 4 kg of the uniformly mixed raw material mixture obtained in step (2) and fill it into each mullite-cordierite sagger (sagger size 330mm*330mm*100mm). Then place the saggers in a roller kiln in a 4-row, 2-layer arrangement and calcine them under an oxidizing atmosphere. The temperature is raised directly from room temperature to 850℃ at a heating rate of 4℃ / min and held for 8 hours. After cooling, the product Li is obtained by crushing and sieving. 1.0 Ni 0.6 Co 0.1 Mn 0.3 Ti 0.002 O 2.004 The average particle size D of the above finished materials v50 Its thickness is 5.7 μm, and its specific surface area is 0.54 m². 2 / g; true density is 4.65g / cm³ 3 The ratio of the median particle size sphere specific surface area to the finished product specific surface area, S. 50 For a spherical particle with S = 0.42 and a diameter equal to the median particle size, the volume V of the hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 =0.008;

[0059] The other steps are the same as in Example 1;

[0060] Example 5:

[0061] (1) A 2 mol / L aqueous solution of NiSO4, CoSO4, and MnSO4 was mixed uniformly at a molar ratio of Ni:Co:Mn = 60:10:30. The mixture was then added to a 0.25 mol / L aqueous solution of NH3·H2O and 10 mol / L NaOH at a feed rate of 500 L / h. The pH was controlled at 11.8 during the nucleation stage by continuously adding NaOH solution, and the nucleation time was controlled at 50 min. During the crystal growth stage, the pH was controlled at 11.3–11.4, and the mixture was stirred under N2 conditions for 70 hours of co-precipitation reaction, yielding an average particle size D50 of 3.5 μm and a specific surface area of ​​7.8 m². 2 / g of particulate metal hydroxide precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)2;

[0062] (2) Take the Ni obtained in step (1) 0.6 Co 0.1 Mn 0.3 (OH)2 and Li2CO3 are mixed evenly at a molar ratio of (Ni+Co+Mn):Li of 1:1;

[0063] (3) Weigh 4 kg of the uniformly mixed raw material mixture obtained in step (2) and fill it into each mullite-cordierite sagger (sagger size 330mm*330mm*100mm). Then place the saggers in a roller kiln in a 4-row, 2-layer arrangement and calcine them under an oxidizing atmosphere. The temperature is raised directly from room temperature to 850℃ at a heating rate of 4℃ / min and held for 8 hours. After cooling, the product Li is obtained by crushing and sieving. 1.0 Ni 0.6 Co 0.1 Mn 0.3 O2. The average particle size D of the above finished materials v50 Its thickness is 4.0 μm, and its specific surface area is 0.65 m². 2 / g; true density is 4.60 g / cm³ 3 The ratio of the median particle size sphere specific surface area to the finished product specific surface area, S 50 For a spherical particle with S = 0.50 and a diameter equal to the median particle size, the volume V of the hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 =0.0054;

[0064] The other steps are the same as in Example 1;

[0065] Example 6:

[0066] (1) A 2 mol / L aqueous solution of NiSO4, CoSO4, and MnSO4 was mixed uniformly at a molar ratio of Ni:Co:Mn = 60:10:30. The mixture was then added to a 0.2 mol / L aqueous solution of NH3·H2O and 10 mol / L NaOH at a feed rate of 500 L / h. During the nucleation stage, the pH was controlled at 11.5, and the nucleation time was controlled at 30 min by continuously adding NaOH solution. During the crystal growth stage, the pH was controlled at 11.1–11.2, and the mixture was stirred under N2 conditions for 95 hours to obtain a co-precipitation reaction with an average particle size D50 of 6.5 μm and a specific surface area of ​​6.4 m². 2 / g of particulate metal hydroxide precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)2;

[0067] (2) Take the Ni obtained in step (1) 0.6 Co 0.1 Mn 0.3 (OH)2 and Li2CO3 are mixed evenly at a molar ratio of (Ni+Co+Mn):Li of 1:1;

[0068] (3) Weigh 4 kg of the uniformly mixed raw material mixture obtained in step (2) and fill it into each mullite-cordierite sagger (sagger size 330mm*330mm*100mm). Then place the saggers in a roller kiln in a 4-row, 2-layer arrangement and calcine them under an oxidizing atmosphere. The temperature is raised directly from room temperature to 860℃ at a heating rate of 4℃ / min and held for 10 hours. After cooling, the product Li is obtained by crushing and sieving. 1.0 Ni 0.6 Co 0.1 Mn 0.3 O2. The average particle size D of the above finished materials v50 Its diameter is 7.0 μm and its specific surface area is 0.43 m². 2 / g; true density is 4.64g / cm³ 3 The ratio of the median particle size sphere specific surface area to the finished product specific surface area, S 50 For a spherical particle with S = 0.43 and a diameter equal to the median particle size, the volume V of the hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 =0.0233;

[0069] The other steps are the same as in Example 1;

[0070] Comparative Example 1:

[0071] (1) A 2 mol / L aqueous solution of NiSO4, CoSO4, and MnSO4 was mixed uniformly at a molar ratio of Ni:Co:Mn = 60:10:30. The mixture was then added to a 0.3 mol / L aqueous solution of NH3·H2O and 10 mol / L NaOH at a feed rate of 500 L / h. During the nucleation stage, the pH was controlled at 11.6, and the nucleation time was controlled at 30 min by continuously adding NaOH solution. During the crystal growth stage, the pH was controlled at 11.1–11.2, and the mixture was stirred under N2 conditions for 110 hours of co-precipitation reaction, yielding an average particle size D50 of 8.0 μm and a specific surface area of ​​4.5 m². 2 / g of particulate metal hydroxide precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)2;

[0072] (2) Take the Ni obtained in step (1) 0.6 Co 0.1 Mn 0.3 (OH)2 and Li2CO3 are mixed evenly at a molar ratio of (Ni+Co+Mn):Li of 1:1;

[0073] (3) Weigh 4 kg of the uniformly mixed raw material mixture obtained in step (2) and fill it into each mullite-cordierite sagger (sagger size 330mm*330mm*100mm). Then place the saggers in a roller kiln in a 4-row, 2-layer arrangement and calcine them under an oxidizing atmosphere. The temperature is raised directly from room temperature to 870℃ at a heating rate of 4℃ / min and held for 10 hours. After cooling, the product Li is obtained by crushing and sieving. 1.0 Ni 0.6 Co 0.1 Mn 0.3 O2. The average particle size D of the above finished materials v50 Its thickness is 8.7 μm, and its specific surface area is 0.50 m². 2 / g; true density is 4.68g / cm³ 3 The ratio of the median particle size sphere specific surface area to the finished product specific surface area, S 50 For a spherical particle with S = 0.29 and a diameter equal to the median particle size, the volume V of the hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 =0.003;

[0074] The other steps are the same as in Example 1;

[0075] Comparative Example 2:

[0076] (1) A 2 mol / L aqueous solution of NiSO4, CoSO4, and MnSO4 was mixed uniformly at a molar ratio of Ni:Co:Mn = 60:10:30. The mixture was then added to a 0.4 mol / L aqueous solution of NH3·H2O and 10 mol / L NaOH at a feed rate of 500 L / h. During the nucleation stage, the pH was controlled at 11.8 and the nucleation time was controlled at 30 min by continuously adding NaOH solution. During the crystal growth stage, the pH was controlled at 11.0–11.1, and the mixture was stirred under N2 conditions for 70 hours to produce a co-precipitation reaction with an average particle size D50 of 3.0 μm and a specific surface area of ​​10 m². 2 / g of particulate metal hydroxide precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)2;

[0077] (2) Take the Ni obtained in step (1) 0.6 Co 0.1 Mn 0.3 (OH)2 and Li2CO3 are mixed evenly at a molar ratio of (Ni+Co+Mn):Li of 1:1;

[0078] (3) Weigh 4 kg of the uniformly mixed raw material mixture obtained in step (2) and fill it into each mullite-cordierite sagger (sagger size 330mm*330mm*100mm). Then place the saggers in a roller kiln in a 4-row, 2-layer manner and calcine them under an oxidizing atmosphere. The temperature is raised directly from room temperature to 840℃ at a heating rate of 4℃ / min and held for 10 hours. After cooling, the product Li is obtained by crushing and sieving. 1.0 Ni 0.6 Co 0.1 Mn 0.3 O2. The average particle size D of the above finished materials v50 Its thickness is 3.5 μm, and its specific surface area is 1.2 m². 2 / g; true density is 4.30 g / cm³ 3 The ratio of the median particle size sphere specific surface area to the finished product specific surface area, S 50 For a spherical particle with S = 0.34 and a diameter equal to the median particle size, the volume V of the hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 =0.003;

[0079] The other steps are the same as in Example 1;

[0080] Comparative Example 3:

[0081] (1) A 2 mol / L aqueous solution of NiSO4, CoSO4, and MnSO4 was mixed uniformly at a molar ratio of Ni:Co:Mn = 60:10:30. The mixture was then added to a 0.1 mol / L aqueous solution of NH3·H2O and 10 mol / L NaOH at a feed rate of 500 L / h. During the nucleation stage, the pH was controlled at 11.8 and the nucleation time was controlled at 30 min by continuously adding NaOH solution. During the crystal growth stage, the pH was controlled at 10.7–10.8, and the mixture was stirred under N2 conditions for 80 hours of co-precipitation reaction, yielding an average particle size D50 of 5.0 μm and a specific surface area of ​​13 m². 2 / g of particulate metal hydroxide precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)2;

[0082] (2) Take the Ni obtained in step (1) 0.6 Co 0.1 Mn 0.3 (OH)2 and Li2CO3 are mixed evenly at a molar ratio of (Ni+Co+Mn):Li of 1:1;

[0083] (3) Weigh 4 kg of the uniformly mixed raw material mixture obtained in step (2) and fill it into each mullite-cordierite sagger (sagger size 330mm*330mm*100mm). Then place the saggers in a roller kiln in a 4-row, 2-layer arrangement and calcine them under an oxidizing atmosphere. The temperature is raised directly from room temperature to 850℃ at a heating rate of 4℃ / min and held for 10 hours. After cooling, the product Li is obtained by crushing and sieving. 1.0 Ni 0.6 Co 0.1 Mn 0.3 O2. The average particle size D of the above finished materials v50 Its diameter is 5.7 μm and its specific surface area is 0.82 m². 2 / g; true density is 4.35g / cm³ 3 The ratio of the median particle size sphere specific surface area to the finished product specific surface area, S 50 For a spherical particle with S = 0.29 and a diameter equal to the median particle size, the volume V of the hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 =0.043;

[0084] The other steps are the same as in Example 1;

[0085] Comparative Example 4:

[0086] (1) A 2 mol / L aqueous solution of NiSO4, CoSO4, and MnSO4 was mixed uniformly at a molar ratio of Ni:Co:Mn = 60:10:30. The mixture was then added to a 0.4 mol / L aqueous solution of NH3·H2O and 10 mol / L NaOH at a feed rate of 500 L / h. During the nucleation stage, the pH was controlled at 11.6, and the nucleation time was controlled at 30 min by continuously adding NaOH solution. During the crystal growth stage, the pH was controlled at 11.3–11.4, and the mixture was stirred under N2 conditions for 90 hours to produce a co-precipitation reaction with an average particle size D50 of 5.0 μm and a specific surface area of ​​3.2 m². 2 / g of particulate metal hydroxide precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)2;

[0087] (2) Take the Ni obtained in step (1) 0.6 Co 0.1 Mn 0.3 (OH)2 and Li2CO3 are mixed evenly at a molar ratio of (Ni+Co+Mn):Li of 1:1;

[0088] (3) Weigh 4 kg of the uniformly mixed raw material mixture obtained in step (2) and fill it into each mullite-cordierite sagger (sagger size 330mm*330mm*100mm). Then place the saggers in a roller kiln in a 4-row, 2-layer arrangement and calcine them under an oxidizing atmosphere. The temperature is raised directly from room temperature to 850℃ at a heating rate of 4℃ / min and held for 10 hours. After cooling, the product Li is obtained by crushing and sieving. 1.0 Ni 0.6 Co 0.1 Mn 0.3 O2. The average particle size D of the above finished materials v50 Its diameter is 5.7 μm and its specific surface area is 0.35 m². 2 / g; true density is 4.70 g / cm³ 3 The ratio of the median particle size sphere specific surface area to the finished product specific surface area, S 50 For a spherical particle with S = 0.64 and a diameter equal to the median particle size, the volume V of the hollow core is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 =0.001;

[0089] The other steps are the same as in Example 1;

[0090] This invention discloses a spherical, particle-shaped nickel-cobalt-manganese ternary cathode material and its preparation method. This material is prepared by precisely controlling the internal pore volume ratio, specific surface area, true density, and median particle size D of the ternary cathode material. v50 By adjusting parameters such as Young's modulus, average size of primary particles in all directions, and crystal structure parameters, the ternary material achieves optimal rate performance while reducing cobalt content.

[0091] like Figure 1 As shown in (a) and (b), the material prepared in Example 1, by controlling the precursor size and sintering process, yielded D. v50 It has a diameter of 5.7 μm and a specific surface area of ​​0.55 m². 2 / g; true density is 4.65g / cm³ 3 The ratio of the specific surface area of ​​the median particle to the specific surface area of ​​the finished product, S, is a spherical, particulate nickel-cobalt-manganese ternary cathode material. 50 S = 0.39, the size of its primary particles is between 300 and 350 nm, and the size of the (104) crystal plane D104 in its XRD pattern is between 60 and 80 nm. Figure 2 (a), (b), and (c) show the materials prepared in Comparative Example 4, Example 1, and Comparative Example 3, respectively. The diameter of the spheres is 5.7 μm, and their cross-sectional views show a hollow structure inside the spheres. The diameters of the hollow portions in the cross-sections are 0.5 μm, 1.0 μm, and 2.0 μm, respectively. Therefore, the volume V of the hollow portion in the core of the three materials in Comparative Example 4, Example 1, and Comparative Example 3 is... 中空 Its spherical volume V 球体 Ratio V 中空 V 球体 The values ​​are approximately 0.001, 0.009, and 0.043, respectively. Table 1 lists the Young's modulus E of the materials in Examples 1-6 and Comparative Examples 1-4. v50 E v10 / E v90 The 0.2C initial discharge specific capacity and 2C / 0.2C rate performance were also assessed. Materials in Examples 1-6 all exhibited high Young's modulus (greater than 200 GPa) and a diameter of D. v10 The particles and diameter D v90 The ratio of the Young's modulus of the primary particles on the particle surface to E v10 / E v90A value between 0.95 and 1.05 indicates that the material has relatively uniform structural strength. Table 1 shows that the materials in Examples 1-6 have good discharge specific capacity and rate performance. It can be seen from Comparative Example 1 that, due to its larger particle size, the material's capacity and rate performance are relatively low. Comparative Example 2, due to its smaller particle size, also lacks advantages in discharge capacity and rate performance, mainly because the smaller particle size leads to more surface side reactions. Comparative Examples 3 and 4, although having particle sizes comparable to Example 1, have significantly larger or smaller specific surface areas, and their internal hollow regions account for an excessively large or small proportion of volume, resulting in a significant reduction in rate performance. In summary, the materials listed in the examples exhibit the following characteristics: internal pore volume ratio, specific surface area, true density, Young's modulus, and median particle size D. v50 The average size of the particles in all directions, crystal structure parameters and other parameters meet the invention requirements, and their capacity, cycle life and rate performance are balanced.

[0092] Table 1 Comparison of various properties of different materials

[0093]

[0094] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A nickel-cobalt-manganese ternary cathode material, which is in the form of spherical particles and is represented by the following formula: Li a Ni x Co y Mn z M b N c O 2+d Where 0.9 < a ​​< 1.2, 0.6 ≤ x < 1, 0 < y < 0.2, 0 < z < 0.4, 0 ≤ b < 0.1, 0 ≤ c < 0.1, 0 ≤ d < 0.1; M is selected from one or more elements Mg, Ti, Zr, Sr, Y, Zn, and N is selected from one or more elements Al, Ce, B, W, Si; The spherical, particle-shaped nickel-cobalt-manganese ternary cathode material has a hollow core structure; and its diameter is the median particle size D. v50 A spherical particle with a hollow core, the volume of which is V. 中空 Its sphere volume V 球体 Ratio V 中空 V 球体 The ratio is between 0.005:1 and 0.025:1; and the diameter is the median particle size D. v50 spherical particles with a specific surface area S 50 The ratio of the specific surface area S of the spherical nickel-cobalt-manganese ternary cathode material measured by the BET method is between 0.35 and 0.

6. The above S 50 S is calculated using the following formula: 50 =[4π(D v50 / 2) 2 ] / [ρ×4 / 3π(D v50 / 2) 3 ]; Where ρ is the true density of the spherical nickel-cobalt-manganese ternary cathode material measured by a true density meter, and its value is between 4.4 and 4.7 g / cm³. 3 Between; the median particle size D of the aforementioned spherical nickel-cobalt-manganese ternary cathode material v50 Its thickness is between 4 and 7 μm, and its specific surface area S is between 0.4 and 0.7 m². 2 Between / g; the spherical particle-shaped nickel-cobalt-manganese ternary cathode material is a secondary particle formed by the stacking of primary particles, wherein the diameter is D v50 The spherical secondary particles have a Young's modulus E of the primary particles on their surface. v50 Between 150 and 350 GPa; where the diameter is D v10 The spherical secondary particles have a Young's modulus of E for the primary particles on their surface. v10 The diameter is D v90 The spherical secondary particles have a Young's modulus E of the primary particles on their surface. v90 And satisfy E v10 / E v90 It ranges from 0.95 to 1.

05.

2. The nickel-cobalt-manganese ternary cathode material according to claim 1, characterized in that... The spherical, particle-shaped nickel-cobalt-manganese ternary cathode material is a secondary particle formed by the stacking of primary particles, wherein the diameter is D. v50 The spherical secondary particles have a Young's modulus E of the primary particles on their surface. v50 Between 220 and 300 GPa.

3. The nickel-cobalt-manganese ternary cathode material according to claim 1, characterized in that, Its crystal space group is R The m-hexagonal phase has a (104) crystal plane size D104 in its XRD pattern that is between 50 and 90 nm.

4. The nickel-cobalt-manganese ternary cathode material according to any one of claims 1 to 3, characterized in that, It is a secondary particle formed by the accumulation of primary particles, and the average length of the primary particles on the surface of the secondary particle is between 250mm and 500mm in any direction.

5. The nickel-cobalt-manganese ternary cathode material according to any one of claims 1 to 4, characterized in that, The source of element M is one or more of the oxides of element M, namely MgO, TiO2, ZrO2, SrO, Y2O3, and ZnO, and the source of element N is one or more of the oxides of element N, namely Al2O3, CeO2, B2O3, WO3, and SiO2.

6. A cathode for a lithium secondary battery, comprising a nickel-cobalt-manganese ternary cathode material according to any one of claims 1 to 5.

7. A lithium secondary battery comprising a positive electrode according to claim 6.

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