A positive electrode material, a preparation method and application thereof

Abstract

The application provides a positive electrode material and a preparation method and application thereof. The first aspect of the application provides a positive electrode material, the chemical formula of the positive electrode material is Li x Ni y Co z A 1‑y‑z O2, 0.9≤x≤1.1, 0.6≤y≤1, 0≤z≤0.4, A is selected from one or more of Mn, Al, W, B, F, P, Ti, V, Al, Ce, Zr, Mg, Y, Sr, Nb, Mo, Sb, Ta, Ge; the LiCO3 content of the surface of the positive electrode material is 400-1200 ppm, the LiOH content is 3000-4500 ppm, the unit cell parameter c of the positive electrode material is 4.20-4.30 A, and the lithium ion diffusion coefficient D of the positive electrode material is greater than 2.5*10 ‑13 cm 2 / s at 20% SOC. The positive electrode material provided by the application is helpful to improve the capacity and cycle performance of the battery and avoid the problem of deteriorated gas production performance.

Description

Technical Field

[0001] This invention relates to a cathode material, its preparation method, and its application, and relates to the field of battery technology. Background Technology

[0002] With the rapid development of the new energy industry, new energy storage batteries occupy an important position in the entire new energy industry. Ternary cathode materials have attracted much attention due to their outstanding advantages such as high power density and energy density, and excellent cycle performance, making them one of the most widely used secondary battery cathode materials in industry.

[0003] As the nickel content in ternary materials increases, the specific capacity of the cathode material also increases. However, with the increase in nickel content, phase transitions become more severe, internal stress within the particles increases, and the risk of particle cracking increases. Simultaneously, ternary materials with higher nickel content are more prone to reacting with CO2 and H2O in the air to generate Li2CO3 and LiOH, resulting in excessively high residual alkali content on the material surface, affecting the battery's cycle performance. Currently, the alkali content on the surface of ternary materials can be controlled through a water washing process. However, if the washing intensity is too strong, while removing residual alkali from the material surface, it can also damage the crystal structure of the material, causing internal lithium deposition, leading to phenomena such as low capacity and deteriorated gas production performance during battery discharge. Summary of the Invention

[0004] This invention provides a cathode material and its preparation method, which helps to improve the capacity and cycle performance of batteries and avoid the problem of deterioration in gas production performance.

[0005] The present invention also provides a battery comprising the above-mentioned positive electrode material, which has good capacity and cycle performance.

[0006] The first aspect of this invention provides a cathode material, the cathode material having the chemical formula Li. x Ni y Co z A 1-y-z O2, 0.9≤x≤1.1, 0.6≤y≤1, 0≤z≤0.4, A is selected from one or more of Mn, Al, W, B, F, P, Ti, V, Al, Ce, Zr, Mg, Y, Sr, Nb, Mo, Sb, Ta, and Ge;

[0007] The LiCO3 content on the surface of the cathode material is 400-1200 ppm, and the LiOH content is 3000-4500 ppm;

[0008] The cell parameter c of the cathode material is:

[0009] In a battery including the aforementioned cathode material at 20% SOC, the lithium-ion diffusion coefficient D of the cathode material is greater than 2.5 × 10⁻⁶. -13 cm 2 / S.

[0010] As in the above-mentioned cathode material, the crack length of the secondary particles of the cathode material is no greater than 4 μm;

[0011] The cathode material was subjected to EDS testing at multiples of 2K. According to the EDS test results, within any 2μm*2μm range, the mass of doping element A was no greater than 30wt% of the total element mass.

[0012] As described above, the positive electrode material includes matrix particles and a coating layer covering the surface of the matrix particles.

[0013] The cathode material described above is prepared by the following method:

[0014] Lithium hydroxide and a first additive are mixed to obtain a first mixture.

[0015] The first mixture is mixed with the precursor to obtain a second mixture;

[0016] The second mixture is subjected to a first sintering treatment, and the sintered product is subjected to annealing, crushing, washing and drying treatments in sequence to obtain matrix particles;

[0017] The first sintering treatment is performed at a temperature of 700–800°C for 8–16 hours, and the annealing treatment is performed at a temperature of 500–800°C for 0.5–3.5 hours.

[0018] The matrix particles are mixed with the second additive and subjected to a second sintering process to obtain the cathode material.

[0019] A second aspect of the present invention provides a method for preparing any of the above-described cathode materials, comprising the following steps:

[0020] Lithium hydroxide and a first additive are mixed to obtain a first mixture.

[0021] The first mixture is mixed with the precursor to obtain a second mixture;

[0022] The second mixture is subjected to a first sintering treatment, and the sintered product is subjected to annealing, crushing, washing and drying treatments in sequence to obtain matrix particles;

[0023] The first sintering treatment is performed at a temperature of 700–800°C for 8–16 hours, and the annealing treatment is performed at a temperature of 500–800°C for 0.5–3.5 hours.

[0024] The matrix particles are mixed with the second additive and subjected to a second sintering process to obtain the cathode material.

[0025] As described above, the lithium hydroxide has a D10 of 20–149 μm, a D50 of 150–500 μm, and a D99 of 501–1000 μm.

[0026] As described above, the precursor has the chemical formula Ni. a Co b B 1-a-b (OH)2, 0.6≤a≤1, 0≤b≤0.4, B is selected from one or both of Mn and Al;

[0027] The precursor has a bulk density of 1.4–1.8 g / cc, a moisture content of <2%, and a BET of 4–12 m. 2 / g.

[0028] As described above, the mixing speed of the lithium hydroxide and the first additive during the mixing process is 600-1000 rpm / min, and the time is 10-30 min.

[0029] As described above, the rotation speed during the mixing process of the first mixture with the precursor is 200–600 rpm / min, and the time is 10–30 min.

[0030] A third aspect of the present invention provides a battery comprising any of the positive electrode materials described above.

[0031] The cathode material provided by this invention helps to improve the capacity and cycle performance of the battery, and effectively avoids the problem of deterioration in the gas production performance of the battery. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 This is a SEM (2K magnification) image of the cathode material provided in Embodiment 1 of the present invention;

[0034] Figure 2 This is a SEM (2K magnification) image of the cathode material provided in Embodiment 2 of the present invention;

[0035] Figure 3This is a SEM (magnification 2K) image of the cathode material provided in Comparative Example 1 of the present invention;

[0036] Figure 4 This is a SEM (magnification 2K) image of the cathode material provided in Comparative Example 2 of the present invention;

[0037] Figure 5 This is a SEM (magnification 2K) image of the cathode material provided in Comparative Example 3 of the present invention;

[0038] Figure 6 This is a SEM (magnification 2K) image of the cathode material provided in Comparative Example 4 of the present invention;

[0039] Figure 7 This is a SEM (magnification 2K) image of the cathode material provided in Comparative Example 5 of the present invention;

[0040] Figure 8 This is a SEM (magnification 2K) image of the cathode material provided in Comparative Example 6 of the present invention;

[0041] Figure 9 This is a SEM (magnification 2K) image of the cathode material provided in Comparative Example 7 of the present invention;

[0042] Figure 10 This is a SEM (magnification 2K) image of the cathode material provided in Comparative Example 8 of the present invention;

[0043] Figure 11 The EDS diagram of the cathode material provided in Embodiment 1 of the present invention;

[0044] Figure 12 This is the EDS diagram of the cathode material provided in Comparative Example 4 of the present invention. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0046] The first aspect of this invention provides a cathode material, the cathode material having the chemical formula Li. x Ni y Co z A 1-y-zO2, 0.9≤x≤1.1, 0.6≤y≤1, 0≤z≤0.4, A is selected from one or more of Mn, Al, W, B, F, P, Ti, V, Al, Ce, Zr, Mg, Y, Sr, Nb, Mo, Sb, Ta, and Ge;

[0047] The LiCO3 content on the surface of the cathode material is 400-1200 ppm, and the LiOH content is 3000-4500 ppm;

[0048] The cell parameter c of the cathode material is:

[0049] In a battery including the aforementioned cathode material at 20% SOC, the lithium-ion diffusion coefficient D of the cathode material is greater than 2.5 × 10⁻⁶. -13 cm 2 / S.

[0050] The cathode material provided by this invention is a high-nickel ternary material, comprising lithium, nickel, cobalt, and other doping elements. In the chemical formula, x, y, and z refer to the molar fraction of each element in the cathode material. For example, x is the ratio of the molar amount of lithium to the molar amount of the cathode material, specifically selected from 0.900, 0.911, 0.915, 0.925, 0.930, 0.935, 0.950, 0.980, 0.995, 1.000, 1.050, 1.085, 1... The range is 0.100 or any two of these values, further wherein x is 0.98-1.08; y is the ratio of the molar amount of nickel to the molar amount of the cathode material, for example selected from 0.600, 0.605, 0.612, 0.625, 0.650, 0.685, 0.690, 0.700, 0.705, 0.720, 0.755, 0.800, 0.850, 0.900, 0.905, 0.950, 1.000 or any of these values. The range formed by both, where z is the ratio of the molar amount of cobalt to the molar amount of the cathode material, can be selected from, for example, 0, 0.01, 0.050, 0.080, 0.1, 0.110, 0.150, 0.185, 0.200, 0.201, 0.220, 0.250, 0.285, 0.3, 0.310, 0.320, 0.350, 0.380, 0.4, or any combination thereof; the dopant element A is selected from Mn, Al, W, and B. One or more of the following elements: F, P, Ti, V, Al, Ce, Zr, Mg, Y, Sr, Nb, Mo, Sb, Ta, and Ge; adding doping elements helps improve the performance of cathode materials. For example, Sr has a large ionic radius and can play a supporting role in the structure; Ta and Zr have high valence states, which help reduce the average valence of Ni, increase the capacity of cathode materials, and improve stability; V has a small ionic radius and can act as interstitial atoms to strengthen the structure of cathode materials.

[0051] Furthermore, the dopant element A is selected from one or more of Mn, Sr, Zr, and B.

[0052] The LiCO3 and LiOH content and cell parameter c on the surface of the cathode material provided by this invention are within the preferred range. Specifically, when the LiCO3 and LiOH content is too high, the conductivity of the cathode material is poor; when the LiCO3 and LiOH content is too low, the active lithium inside is easily deposited, resulting in a low active lithium content and affecting the capacity of the lithium-ion battery. Therefore, the LiCO3 content on the surface of the cathode material provided by this invention is 400-1200 ppm, and the LiOH content is 3000-4500 ppm. The LiCO3 and LiOH content can be determined using an 888 automatic potentiometric titrator. The specific steps include: weighing 30g of the cathode material to be tested, adding 100ml of pure water, stirring for 30min, filtering with double-layer medium-speed filter paper, transferring 10ml of liquid, using 0.05mol / L HCl as the standard solution, determining the endpoint according to the potentiometric titration method, and determining the LiCO3 and LiOH content.

[0053] The cell parameter c of the cathode material provided by this invention is The unit cell parameter *c* refers to the length of a unit translation vector along the crystal axis *c* in the unit cell. A larger *c*-axis indicates a larger sintered cell in the cathode material, resulting in fewer lithium ions per unit volume and lower capacity. Conversely, a smaller *c*-axis indicates a smaller sintered cell in the cathode material, resulting in more lithium ions per unit volume, but poor crystallinity and difficulty in lithium ion insertion / extraction, also leading to lower capacity. The unit cell parameter *c* can be obtained through XRD detection and software calculation. XRD equipment can be purchased from Bruker, and data processing uses the corresponding software TOPAS. The processing includes: importing a matching CIF file into TOPAS, modifying and confirming the atomic occupancy, element types, and temperature factors of the imported structure file, and selecting and fitting the unit cell parameters *a* and *c*.

[0054] The cathode material provided by this invention also has a high lithium-ion diffusion coefficient, specifically, the lithium-ion diffusion coefficient D > 2.5 * 10⁻⁶. -13 cm 2 The lithium-ion diffusion coefficient ( / s) is calculated by testing a battery containing this cathode material when it is discharged to 20% charge. A higher lithium-ion diffusion coefficient indicates easier lithium-ion diffusion and better cycle performance of the battery containing this cathode material. The lithium-ion diffusion rate can be calculated using Equation 1:

[0055]

[0056] In Equation 1, π is the mathematical constant pi; τ is the pulse current input time, in seconds (s); m B V represents the mass of the active material in the cathode material, expressed in g. M The molar volume of the active substance is expressed in cm. 3 / mol; S is the active contact surface area between the positive electrode material and the electrolyte, cm². 2 MB The molar mass of the active substance is given in g / mol, and ΔEs is the voltage change caused by the pulse. T Voltage change during constant current charging (discharging).

[0057] To further improve the performance of the cathode material, the crack length of the secondary particles of the cathode material is no greater than 4 μm, and the crack length can be obtained by scanning electron microscopy.

[0058] The cathode material was subjected to EDS testing at a magnification of 2K. According to the EDS test results, within any 2μm*2μm range, the mass of dopant element A was no greater than 30wt% of the total element mass. It can be understood that EDS, as an elemental analysis instrument, performs elemental analysis on the cathode material at a magnification of 2K. Within the field of view at this magnification, samples of 2μm*2μm size are taken. Within the sampling area, dopant element A does not aggregate, and its mass is no greater than 30wt% of the total element mass. This indicates that the distribution of dopant element A is relatively uniform, which helps to improve the performance of the cathode material.

[0059] The positive electrode material provided by this invention includes matrix particles and a coating layer covering the surface of the matrix particles. The coating layer can protect the surface of the positive electrode material and isolate it from electrolyte corrosion, and can also improve the conductivity of the positive electrode material. The dopant element A can be distributed inside the matrix particles or in the coating layer.

[0060] The cathode material provided by this invention is prepared by the following method:

[0061] Lithium hydroxide and a first additive are mixed to obtain a first mixture.

[0062] The first mixture is mixed with the precursor to obtain a second mixture;

[0063] The second mixture is subjected to a first sintering treatment, and the sintered product is subjected to annealing, crushing, washing and drying treatments in sequence to obtain matrix particles;

[0064] The first sintering treatment is performed at a temperature of 700–800°C for 8–16 hours, and the annealing treatment is performed at a temperature of 500–800°C for 0.5–3.5 hours.

[0065] The matrix particles are mixed with the second additive and subjected to a second sintering process to obtain the cathode material.

[0066] The cathode material provided by this invention is synthesized by high-temperature solid-state synthesis and annealing is introduced after the first sintering treatment. This helps to eliminate residual stress inside the sintered product, optimize lithium intercalation, reduce surface residual alkali content, improve lithium ion diffusion coefficient, and improve the mechanical and process properties of the finished cathode material.

[0067] A second aspect of the present invention provides a method for preparing any of the above-described cathode materials, comprising the following steps:

[0068] Step 1: Mix lithium hydroxide and the first additive to obtain a first mixture;

[0069] First, the types of lithium hydroxide and the first additive are selected. Specifically, in order to reduce the preparation cost of ternary materials, the lithium hydroxide used in this invention is coarse-particle lithium hydroxide with a D10 of 20-149 μm, a D50 of 150-500 μm, and a D99 of 501-1000 μm. The first additive is a compound containing dopant element A, such as an oxide containing dopant element, specifically such as ZrO2, SrO, MgO2, Al2O3, etc.

[0070] Lithium hydroxide and the first additive are mixed in the required mass ratio. The mixing process can be carried out in a high-speed mixer, and the coarse lithium hydroxide particles are crushed at the same time to improve the uniformity of sintering. Furthermore, the mixing speed is controlled at 600-1000 rpm / min and the time is 10-30 min to obtain the first mixture.

[0071] Step 2: Mix the first mixture with the precursor to obtain the second mixture;

[0072] The first mixture obtained in step 1 is mixed with the precursor, specifically, the precursor has the chemical formula Ni. a Co b B 1-a-b (OH)₂, 0.6≤a≤1, 0≤b≤0.4, B is selected from one or two of Mn and Al; the loose bulk density of the precursor is 1.4~1.8g / cc, moisture content <2%, BET is 4~12m 2 / g.

[0073] The mixing process can also be carried out in a mixer. It should be noted that the rotation speed when mixing the first mixture with the precursor should be lower than the rotation speed when mixing lithium hydroxide and the first additive. Specifically, the rotation speed when mixing the first mixture with the precursor should be 200-600 rpm / min, and the time should be 10-30 min. Otherwise, if the rotation speed is too high, cracks may appear in the precursor. Cracks can lead to short circuits in electrons. In addition, the appearance of cracks will cause more negative reactions with the electrolyte on these fresh surfaces, affecting the cycle performance and safety of the entire battery.

[0074] Step 3: Perform a first sintering treatment on the second mixture, and then perform annealing, crushing, washing and drying treatments on the sintered product in sequence to obtain matrix particles;

[0075] Next, the second mixture undergoes a first sintering treatment. During the sintering process, the second mixture is typically placed in a sagger. Specifically, the amount of the second mixture in the sagger is 6–11 kg / sagger, more specifically 8 kg / sagger, with a loading height of 6–11 cm, more specifically 7–10 cm, and even more specifically 7.5–8.5 cm. Simultaneously, the sintering process is carried out in a roller kiln. Specifically, the length of the roller kiln is 6–20 m, the sintering atmosphere is a pure oxygen atmosphere, and the oxygen flow rate is 400–1200 L / min. The temperature of the first sintering treatment is 700–800 °C, and the time is 8–16 h. More specifically, the temperature of the first sintering treatment is 750 °C, and the time is 12 h.

[0076] After the first sintering treatment, an annealing treatment is performed. Specifically, the annealing temperature is reduced to 500-800℃ for 0.5-3.5 hours. By passing through the annealing stage and controlling the annealing temperature to be no lower than 500℃, the chemical composition inside the cathode material is homogenized, the mechanical and processing properties are improved, the internal residual stress is reduced, the cathode material cell shrinks appropriately, the strength of the ternary material particles and the lithium-ion diffusion coefficient are improved, the lithium intercalation balance is improved, and thus the processing performance is improved.

[0077] Subsequently, the annealed product was subjected to crushing, washing and drying processes in sequence. Specifically, the D50 of the crushed particles was controlled at 10.0±1.0μm.

[0078] The water-to-material ratio during the washing process is 0.8–1.2:1, further 0.9–1.1:1, and even further 1:1; the washing time is 0–5 min, further 1–4 min, and even further 2–3 min; the washing temperature is 0–10°C; and stirring is performed simultaneously during the washing process at a speed of 15–60 rpm, further 20–50 rpm, and even further 30–40 rpm.

[0079] The material is washed and then subjected to pressure filtration and drying. The drying temperature is 120–190°C, further 130–180°C, even further 140–170°C, and even further 150–160°C; the drying time is 3–7 hours, further 4–6 hours, and even further 5 hours. The moisture content of the dried material is controlled below 0.5 wt%.

[0080] Step 4: Mix the matrix particles with the second additive and perform a second sintering treatment to obtain the positive electrode material.

[0081] Finally, the dried matrix particles are mixed with a second additive, which is selected from substances containing elements such as W, B, F, P, and Ti, and more specifically H3BO3. During the mixing process, the stirring speed is controlled at 150–250 rpm, more specifically 180–220 rpm, and even more specifically 200 rpm; the stirring time is 100–140 min, more specifically 110–130 min, and even more specifically 120 min. The second sintering treatment is carried out in a roller kiln at a sintering temperature of 260–360℃, more specifically 280–340℃, and even more specifically 300–320℃; the sintering time is 8–14 h; and the sagger loading in the second sintering treatment is 4–7 kg / sagger, more specifically 5–6 kg / sagger.

[0082] The sintered products obtained after the second sintering process are sequentially screened, iron removed, and packaged to obtain the finished high-nickel ternary material.

[0083] A third aspect of the present invention provides a battery comprising any of the positive electrode materials described above.

[0084] Based on the characteristics of the cathode material in the first aspect, the battery made of the cathode material has good capacity and cycle performance, avoiding the problem of deterioration in gas production performance.

[0085] In one specific embodiment, the battery provided by the present invention includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the positive electrode sheet includes a positive current collector and a positive active layer disposed on the surface of the positive current collector, the positive active layer including the aforementioned positive electrode material.

[0086] In addition to the cathode material, the cathode active layer also includes a conductive agent and a binder. There are no special requirements for the selection of the conductive agent and binder; they can be conventional choices in the field. For example, the conductive agent is selected from at least one of conductive carbon black, acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, single-walled carbon nanotubes, multi-arm carbon nanotubes, and carbon fibers; the binder is selected from at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and lithium polyacrylate (PAALi).

[0087] There are no special requirements for the selection of the negative electrode, separator, and electrolyte; all are conventional choices in this field.

[0088] The positive electrode active material of the present invention will be described below through specific embodiments.

[0089] Example 1

[0090] The cathode material provided in this embodiment includes the following steps:

[0091] Step 1: Add 9.45 kg of crude lithium hydroxide powder, 10 g of ZrO2 and 5 g of SrO to an 80 L high-speed mixer and stir at 800 rpm / min for 20 min to obtain the first mixture.

[0092] Step 2: Add 20 kg of precursor Ni to the first mixture. 0.85 Co 0.06 Mn 0.09 (OH)₂, the precursor has a bulk density of 1.60 g / cc, a moisture content of 0.15%, and a BET of 6.2 m. 2 / g, mix at 400 rpm / min for 20 min to obtain the second mixture;

[0093] Step 3: Load the second mixture into a sagger with a sagger weight of 8 kg / sagger and a loading height of 8 cm. Then, perform the first sintering treatment in a 10-meter atmosphere roller kiln. Control the temperature of the first sintering treatment at 750℃ for 12 hours, and then cool it down to 650℃ and hold it for 2 hours. The sintering atmosphere is a pure oxygen atmosphere with an oxygen flow rate of 800 L / min to obtain the first sintered product.

[0094] Step 4: Crush the first sintered product, control the D50 to 10.0±1.0μm, and then wash it with water at a 1:1 ratio for 2 minutes. The stirring rod speed is 40 rpm and the water temperature is 5℃. Then filter and dry it to control the moisture content to below 0.5%.

[0095] Step 5: Mix the dried matrix particles and 10g H3BO3 at 200rpm for 120min. After the materials are evenly mixed, place them in a roller kiln for secondary sintering. The sagger filling amount is 5.5kg / sagger, the sintering temperature is 300℃, and the sintering time is 8h. After screening, iron removal, and packaging, the finished high-nickel ternary material is obtained.

[0096] Example 2

[0097] The preparation method of the positive electrode material provided in this embodiment can be referred to in Embodiment 1. The difference is that in the first sintering process, the amount of material in the sagger is 6 kg / sagger and the material loading height is 6 cm.

[0098] Comparative Example 1

[0099] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0100] Step 1: Take 20 kg of precursor Ni 0.85 Co 0.06 Mn 0.09(OH)2, 9.45 kg of fine lithium hydroxide powder, 10 g of ZrO2 and 5 g of SrO were added to an 80 L high-speed mixer and stirred at 800 rpm / min for 20 min to obtain a mixture.

[0101] Step 2: Load the mixture into a sagger with a loading capacity of 5 kg / sagger and a loading height of 8 cm. Then, carry out the first sintering treatment in a 10-meter atmosphere roller kiln. Control the temperature of the first sintering treatment at 750℃, the holding time at 12 h, the sintering atmosphere at pure oxygen atmosphere, and the oxygen flow rate at 800 L / min to obtain the first sintered product.

[0102] Step 3: Crush the first sintered product, control the D50 to 10.0±1.0μm, and then wash it with water at a 1:1 ratio for 2 minutes. The stirring rod speed is 40 rpm and the water temperature is 5℃. Then filter and dry it to control the moisture content to below 0.5%.

[0103] Step 4: Mix the dried matrix particles and 10g H3BO3 at 200rpm for 120min. After the materials are evenly mixed, place them in a roller kiln for secondary sintering. The sagger filling amount is 5.5kg / sagger, the sintering temperature is 300℃, and the sintering time is 8h. After screening, iron removal, and packaging, the finished high-nickel ternary material is obtained.

[0104] Comparative Example 2

[0105] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0106] Step 1: Take 20 kg of precursor Ni 0.85 Co 0.06 Mn 0.09 (OH)2, 9.45 kg of crude lithium hydroxide powder, 10 g of ZrO2 and 5 g of SrO were added to an 80 L high-speed mixer and stirred at 800 rpm / min for 20 min to obtain a mixture.

[0107] Step 2: Load the mixture into saggers, with a sagger weight of 8 kg / sagger and a loading height of 8 cm. Then, place the saggers into a rotary kiln for pre-oxidation to dehydrate the precursor and lithium hydroxide. Sintering is then performed at 500℃ for 6 hours in a pure oxygen atmosphere at a flow rate of 500 L / min to obtain the pre-oxidized material. The pre-sintered material is then sintered in a 10-meter atmosphere roller kiln, with a sagger weight of 10 kg / sagger and a loading height of approximately 8 cm. The sintering temperature is 750℃, and the holding time is 12 hours in a pure oxygen atmosphere at a flow rate of 800 L / min to obtain the primary sintered material.

[0108] Step 3: Crush the primary sintered material, controlling the D50 to 10.0±1.0μm, and then wash it with water at a 1:1 ratio for 2 minutes, with the stirring rod speed at 40 rpm and the water temperature at 5℃. Then filter and dry it to control the moisture content to below 0.5%.

[0109] Step 4: Mix the dried matrix particles and 10g H3BO3 at 200rpm for 120min. After the materials are evenly mixed, place them in a roller kiln for secondary sintering. The sagger filling amount is 5.5kg / sagger, the sintering temperature is 300℃, and the sintering time is 8h. After screening, iron removal, and packaging, the finished high-nickel ternary material is obtained.

[0110] Comparative Example 3

[0111] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0112] Step 1: Take 20 kg of precursor Ni 0.85 Co 0.06 Mn 0.09 (OH)2, 9.45 kg of crude lithium hydroxide powder, 10 g of ZrO2 and 5 g of SrO were added to an 80 L high-speed mixer and stirred at 800 rpm / min for 20 min to obtain a mixture.

[0113] Step 2: Load the mixture into saggers with a sagger weight of 8 kg / sagger and a loading height of 8 cm. Then, sinter the mixture in a 10-meter atmosphere roller kiln at a sintering temperature of 750℃ for 12 hours. Then, cool the mixture down to 650℃ and hold it for 2 hours. The sintering atmosphere is pure oxygen with an oxygen flow rate of 800 L / min to obtain the primary sintered material.

[0114] Step 3: Crush the primary sintered material, controlling the D50 to 10.0±1.0μm, and then wash it with water at a 1:1 ratio for 2 minutes, with the stirring rod speed at 40 rpm and the water temperature at 5℃. Then filter and dry it to control the moisture content to below 0.5%.

[0115] Step 4: Mix the dried matrix particles and 10g H3BO3 at 200rpm for 120min. After the materials are evenly mixed, place them in a roller kiln for secondary sintering. The sagger filling amount is 5.5kg / sagger, the sintering temperature is 300℃, and the sintering time is 8h. After screening, iron removal, and packaging, the finished high-nickel ternary material is obtained.

[0116] Comparative Example 4

[0117] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0118] Step 1: Take 20 kg of precursor Ni 0.85 Co 0.06 Mn 0.09 (OH)2, 9.45 kg of crude lithium hydroxide powder, 10 g of ZrO2 and 5 g of SrO were added to an 80 L high-speed mixer and stirred at 400 rpm / min for 20 min to obtain a mixture.

[0119] Step 2: Load the mixture into saggers with a sagger weight of 8 kg / sagger and a loading height of 8 cm. Then, sinter the mixture in a 10-meter atmosphere roller kiln at a sintering temperature of 750℃ for 12 hours. Then, cool the mixture down to 650℃ and hold it for 2 hours. The sintering atmosphere is pure oxygen with an oxygen flow rate of 800 L / min to obtain the primary sintered material.

[0120] Step 3: Crush the primary sintered material, controlling the D50 to 10.0±1.0μm, and then wash it with water at a 1:1 ratio for 2 minutes, with the stirring rod speed at 40 rpm and the water temperature at 5℃. Then filter and dry it to control the moisture content to below 0.5%.

[0121] Step 4: Mix the dried matrix particles and 10g H3BO3 at 200rpm for 120min. After the materials are evenly mixed, place them in a roller kiln for secondary sintering. The sagger filling amount is 5.5kg / sagger, the sintering temperature is 300℃, and the sintering time is 8h. After screening, iron removal, and packaging, the finished high-nickel ternary material is obtained.

[0122] Comparative Example 5

[0123] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0124] Step 1: Add 9.45 kg of crude lithium hydroxide powder, 10 g of ZrO2 and 5 g of SrO to an 80 L high-speed mixer and stir at 800 rpm / min for 20 min to obtain the first mixture.

[0125] Step 2: Add 20 kg of precursor Ni to the first mixture. 0.85 Co 0.06 Mn 0.09 (OH)2 was stirred at 400 rpm / min for 20 min to obtain a second mixture.

[0126] Step 3: Load the second mixture into a sagger, with a sagger weight of 8 kg / sagger and a loading height of about 8 cm. Then, carry out the first sintering treatment in a 10-meter atmosphere roller kiln. Control the temperature of the first sintering treatment to 750℃, the holding time to 12 h, and the sintering atmosphere to be pure oxygen atmosphere with an oxygen flow rate of 800 L / min to obtain the primary sintered material.

[0127] The sintered material was crushed, with D50 controlled at 10.0±1.0μm. Then it was washed with water at a ratio of 1:1 for 2 minutes, with the stirring rod speed at 40 rpm and the water temperature at 5℃. After that, it was filtered and dried to control the moisture content to below 0.5%.

[0128] Step 4: Mix the dried matrix particles and 10g H3BO3 at 200rpm for 120min. After the materials are evenly mixed, place them in a roller kiln for secondary sintering. The sagger filling amount is 5.5kg / sagger, the sintering temperature is 300℃, and the sintering time is 8h. After screening, iron removal, and packaging, the finished high-nickel ternary material is obtained.

[0129] Comparative Example 6

[0130] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0131] Step 1: Add 9.45 kg of crude lithium hydroxide powder, 10 g of ZrO2 and 5 g of SrO to an 80 L high-speed mixer and stir at 800 rpm / min for 20 min to obtain the first mixture.

[0132] Step 2: Add 20 kg of precursor Ni to the first mixture. 0.85 Co 0.06 Mn 0.09 (OH)2 was stirred at 400 rpm / min for 20 min to obtain a second mixture.

[0133] Step 3: Load the second mixture into a sagger with a sagger weight of 8 kg / sagger and a loading height of 8 cm. Then, perform the first sintering treatment in a 10-meter atmosphere roller kiln at a sintering temperature of 695℃ for 12 hours. Then, cool down to 650℃ and hold for 2 hours. The sintering atmosphere is a pure oxygen atmosphere with an oxygen flow rate of 800 L / min to obtain the primary sintered material.

[0134] The sintered material was crushed, with D50 controlled at 10.0±1.0μm. Then it was washed with water at a ratio of 1:1 for 2 minutes, with the stirring rod speed at 40 rpm and the water temperature at 5℃. After that, it was filtered and dried to control the moisture content to below 0.5%.

[0135] Step 4: Mix the dried matrix particles and 10g H3BO3 at 200rpm for 120min. After the materials are evenly mixed, place them in a roller kiln for secondary sintering. The sagger filling amount is 5.5kg / sagger, the sintering temperature is 300℃, and the sintering time is 8h. After screening, iron removal, and packaging, the finished high-nickel ternary material is obtained.

[0136] Comparative Example 7

[0137] The method for preparing the cathode material provided in this comparative example includes the following steps:

[0138] Step 1: Add 9.45 kg of crude lithium hydroxide powder, 10 g of ZrO2 and 5 g of SrO to an 80 L high-speed mixer and stir at 800 rpm / min for 20 min to obtain the first mixture.

[0139] Step 2: Add 20 kg of precursor Ni to the first mixture. 0.85 Co 0.06 Mn 0.09 (OH)2 was stirred at 400 rpm / min for 20 min to obtain a second mixture.

[0140] Step 3: Load the second mixture into a sagger with a sagger weight of 8 kg / sagger and a loading height of 8 cm. Then, sinter it once in a 10-meter atmosphere roller kiln at a sintering temperature of 805℃ for 12 hours. Then, cool it down to 650℃ and hold it for 2 hours. The sintering atmosphere is pure oxygen with an oxygen flow rate of 800 L / min to obtain the first sintered material.

[0141] The sintered material was crushed, with D50 controlled at 10.0±1.0μm. Then it was washed with water at a ratio of 1:1 for 2 minutes, with the stirring rod speed at 40 rpm and the water temperature at 5℃. After that, it was filtered and dried to control the moisture content to below 0.5%.

[0142] Step 4: Mix the dried matrix particles and 10g H3BO3 at 200rpm for 120min. After the materials are evenly mixed, place them in a roller kiln for secondary sintering. The sagger filling amount is 5.5kg / sagger, the sintering temperature is 300℃, and the sintering time is 8h. After screening, iron removal, and packaging, the finished high-nickel ternary material is obtained.

[0143] Comparative Example 8

[0144] The preparation method of the cathode material provided in this comparative example can be referred to in Example 1, except that the annealing temperature is 400°C and the time is 2 hours.

[0145] The contents of Li₂CO₃ and LiOH in the sintered products after the first sintering treatment in Examples 1-2 and Comparative Examples 1-8 were detected, and the Free Li was calculated according to Equation 2. + The content was calculated, and the capacity of the roller kiln was statistically analyzed. The results are shown in Table 1.

[0146] Formula 2: Free Li + =6.941*2*Li2CO3 / 73.89+6.941*LiOH / 23.94

[0147] SEM observation was performed on the finished cathode materials provided in Examples 1-2 and Comparative Examples 1-8, and the results are as follows: Figures 1-10 As shown, it can be seen that the secondary particles of the cathode material provided in Comparative Example 3 show obvious cracks.

[0148] The cathode materials provided in Example 1 and Comparative Example 4 were subjected to EDS analysis at 2K magnification. The results are as follows: Figures 11-12 As shown, Figures 11-12 In the image, the left side shows the electronic image of the cathode material, the middle side shows the distribution of Zr elements, and the right side shows the distribution of Sr elements. It can be seen that the cathode material provided in Example 1 has a relatively uniform distribution of doped elements, while the cathode material provided in Comparative Example 4 shows the aggregation of doped element Zr.

[0149] The Li2CO3 and LiOH contents on the surface of the finished cathode materials provided in Examples 1-2 and Comparative Examples 1-8 were detected, and Free Li+ was calculated according to Equation 2. The results are shown in Table 2.

[0150] The finished positive electrode materials provided in Examples 1-2 and Comparative Examples 1-8 were assembled into coin cells. Specifically, the positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) were weighed at a mass ratio of 94:3:3, mixed evenly, and NMP was added and stirred for 2 hours to form a viscous slurry. This slurry was then evenly coated onto aluminum foil, vacuum baked at 80°C, pressed into sheets, and cut into positive electrode sheets with a diameter of 14 mm. A 16 mm diameter pure lithium sheet was used as the negative electrode, a 1 mol / L LiPF6 + DEC / EC (volume ratio 1:1) mixed solution was used as the electrolyte, and a polyCelgard propylene microporous membrane was used as the separator. The coin cells were assembled in an argon-filled glove box. The lithium-ion diffusion coefficient of the positive electrode material, as well as the capacity, gas generation performance, and cycle capacity retention of the coin cells, were analyzed. The analytical conditions and results are shown in Table 2.

[0151]

[0152]

[0153] According to the data provided in Comparative Example 1 in Table 1, conventional cathode material preparation methods have limited feed rates, resulting in limited production capacity. Furthermore, the use of fine-particle lithium hydroxide leads to higher preparation costs. According to the data provided in Comparative Example 2 in Table 1, adding a dehydration process before sintering reduces the particle size of coarse lithium hydroxide, which helps increase the feed rate and production capacity. However, the dehydration process requires modification of existing equipment, resulting in significant modification costs. In Example 1 of this invention, similar production capacity to Comparative Example 2 can be achieved without dehydration. Additionally, the preparation processes provided in Comparative Examples 1 and 2 do not include annealing, resulting in cathode materials with higher residual alkali content, slightly higher cell parameter c, and lower lithium-ion diffusion coefficient D. According to the data provided in Comparative Examples 3 and 4 in Tables 1 and 2, cathode materials prepared by either high-speed direct mixing or low-speed direct mixing exhibit certain problems. High-speed mixing of coarse lithium hydroxide... Impact on the precursor causes cracks, leading to a deterioration in the particle strength of the cathode material and affecting the battery's cycle capacity retention. Low-speed mixing causes uneven distribution of doping elements, resulting in a deterioration in particle strength and cycle performance. According to the data provided in Comparative Examples 5-7 in Tables 1-2, excessively high or low first sintering temperatures, as well as whether or not annealing is performed, affect the residual alkali content, cell parameter c, and lithium-ion diffusion coefficient of the sintered product, thus affecting the battery's capacity and cycle performance. According to the data provided in Comparative Example 8 in Tables 1-2, when the annealing temperature is too low, the lithium-ion diffusion coefficient of the finished cathode material is easily lower, affecting the battery's cycle performance. Therefore, the preparation process provided by this invention can control the Li2CO3 and LiOH content, cell parameter c, and lithium-ion diffusion coefficient D on the cathode material surface within the preferred range, and avoids the problems of cracks and uneven distribution of doping elements, which helps to improve the overall performance of the battery.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode material, characterized in that, The chemical formula of the positive electrode material is Li x Ni y Co z A 1-y-z O2, 0.9≤x≤1.1, 0.6≤y≤1, 0≤z≤0.4, A is selected from one or more of Mn, Al, W, B, F, P, Ti, V, Al, Ce, Zr, Mg, Y, Sr, Nb, Mo, Sb, Ta, and Ge; The LiCO3 content on the surface of the positive electrode material is 400-1200 ppm, and the LiOH content is 3000-4500 ppm; The cell parameter c of the cathode material is 14.18 Å to 14.25 Å; In a battery including the aforementioned cathode material, at 20% SOC, the lithium-ion diffusion coefficient D of the cathode material is greater than 2.

5. 10 - 13 cm 2 / S; The crack length of the secondary particles of the cathode material is no greater than 4 μm; The cathode material was subjected to EDS testing at a multiple of 2K. Based on the EDS test results, at any 2μm... Within the 2μm range, the mass of dopant element A is no greater than 30wt% of the total element mass.

2. The cathode material according to claim 1, characterized in that, The positive electrode material includes matrix particles and a coating layer covering the surface of the matrix particles.

3. The cathode material according to claim 1 or 2, characterized in that, The cathode material is prepared by the following method: Lithium hydroxide and a first additive are mixed to obtain a first mixture. The first mixture is mixed with the precursor to obtain a second mixture; The second mixture is subjected to a first sintering treatment, and the sintered product is subjected to annealing, crushing, washing and drying treatments in sequence to obtain matrix particles; The first sintering treatment is performed at a temperature of 700–800°C for 8–16 hours, and the annealing treatment is performed at a temperature of 500–800°C for 0.5–3.5 hours. The matrix particles are mixed with the second additive and subjected to a second sintering process to obtain the cathode material.

4. The method for preparing the cathode material according to any one of claims 1 to 3, characterized in that, Includes the following steps: Lithium hydroxide and a first additive are mixed to obtain a first mixture. The first mixture is mixed with the precursor to obtain a second mixture; The second mixture is subjected to a first sintering treatment, and the sintered product is subjected to annealing, crushing, washing and drying treatments in sequence to obtain matrix particles; The first sintering treatment is performed at a temperature of 700–800°C for 8–16 hours, and the annealing treatment is performed at a temperature of 500–800°C for 0.5–3.5 hours. The matrix particles are mixed with the second additive and subjected to a second sintering process to obtain the cathode material.

5. The preparation method according to claim 4, characterized in that, The lithium hydroxide has a D10 of 20–149 μm, a D50 of 150–500 μm, and a D99 of 501–1000 μm.

6. The preparation method according to claim 4, characterized in that, The precursor has the chemical formula Ni a Co b B 1-a-b (OH)2, 0.6≤a≤1, 0≤b≤0.4, B is selected from one or both of Mn and Al; The precursor has a bulk density of 1.4–1.8 g / cc, a moisture content of <2%, and a BET of 4–12 m. 2 / g.

7. The preparation method according to claim 4, characterized in that, The mixing speed of the lithium hydroxide and the first additive is 600-1000 rpm / min, and the time is 10-30 min.

8. The preparation method according to claim 4, characterized in that, The rotational speed during the mixing process of the first mixture with the precursor is 200-600 rpm / min, and the time is 10-30 min.

9. A battery, characterized in that, The battery comprises the positive electrode material as described in any one of claims 1 to 3.

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