Monocrystal ternary positive electrode material, preparation method thereof and positive electrode slurry

Abstract

The invention relates to the technical field of lithium battery positive electrode materials, in particular to a single-crystal ternary positive electrode material, a preparation method thereof and positive electrode slurry. The single crystal ternary positive electrode material meets the following requirements: (1) X = Dv1 / Dv50; wherein X represents particle consistency, and X is not less than 0.2; (2) Y = (Dv1 '-Dv1) / Dv1'; wherein Y represents the agglomeration ratio of the micro powder and is not greater than 0.25. Wherein the Dv1, the Dv50 and the Dv1'are obtained by testing according to a GB / T 19077-2016 particle size distribution laser diffraction method; ultrasonic dispersion is not adopted during Dv1'testing; and ultrasonic dispersion is adopted when the Dv1 and the Dv50 are tested. The single-crystal ternary positive electrode material is low in micro powder content and easy to disperse, and the amount of bubbles in positive electrode slurry can be greatly reduced on the basis of not adopting a defoaming agent.

Description

Technical Field

[0001] This invention relates to the field of lithium battery cathode material technology, and more specifically, to a single-crystal ternary cathode material, its preparation method, and cathode slurry. Background Technology

[0002] Since their commercial production began in the 1990s, lithium-ion batteries have been the ideal power source for portable electronic products such as mobile phones, laptops, and cameras due to their advantages including high specific energy, no pollution, no memory effect, and long cycle life. Cathode materials, as one of the four core materials of a battery, significantly influence its overall performance. Layered nickel-manganese-cobalt ternary cathode materials have become the most commercially promising cathode material due to their relatively high specific energy and operating voltage.

[0003] As a modified material of secondary spherical ternary cathode material, single-crystal ternary cathode material makes up for the shortcomings of secondary particulate ternary cathode material and will play an important role in future lithium-ion battery materials. Compared with secondary spherical particulate ternary cathode material, single-crystal ternary cathode material has the following advantages: (1) There is no intercrystalline interface inside the single crystal particles, and no intercrystalline breakage occurs after multiple charge-discharge cycles; (2) The single crystal particles have a small specific surface area, a small contact area with the electrolyte, and small side reactions; (3) Single-crystal ternary material has high mechanical strength, is not easy to break during compaction, and has a high compaction density. However, single-crystal ternary cathode material products often contain too many microparticles (or "micropowder"), and the presence of micropowder seriously restricts the overall performance of the battery.

[0004] Currently, the control of micronized powder is a material that battery manufacturers must strictly control during the battery manufacturing process, as the content of micronized powder directly determines the battery's storage life. Specifically, micronized powder increases the risk of side reactions and micro-short circuits inside the battery, and the impact becomes more severe with the increase of micronized powder. On the other hand, the presence of micronized powder will deteriorate the battery's high-temperature storage performance, causing the battery to experience capacity decay, increased internal resistance, and phenomena such as gas expansion during storage.

[0005] Meanwhile, due to the presence of micronized powder, particle agglomeration is severe, and air is stored within the agglomerates. Therefore, when preparing the coating slurry, air bubbles are released from the slurry. During the coating process, these air bubbles adhere to the electrode sheet. After drying, the air bubbles on the electrode sheet will burst, leaving pits or forming cavitation nuclei, resulting in uneven electrode sheet thickness. This further leads to numerous fine cracks, peeling, and powder shedding on the electrode sheet, affecting the electrode sheet yield and ultimately causing a deterioration in battery capacity, internal resistance, cycle life, and safety.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a single-crystal ternary cathode material, its preparation method, and cathode slurry. The single-crystal ternary cathode material provided by this invention has a low powder content, is easy to disperse, and can significantly reduce the amount of air bubbles in the cathode slurry without the use of defoamers, thereby significantly improving the cycle life and other performance characteristics of lithium-ion batteries.

[0008] This invention is implemented as follows: In a first aspect, the present invention provides a single-crystal ternary cathode material, wherein the single-crystal ternary cathode material meets the following requirements: (1) X = Dv1 / Dv50; where X represents particle uniformity and X is not less than 0.2; the units of Dv1 and Dv50 are both micrometers; Both Dv1 and Dv50 were obtained according to "GB / T 19077-2016 Particle size distribution by laser diffraction method", and ultrasonic dispersion was used during the test. (2) Y = (Dv1′ - Dv1) / Dv1′; where Y represents the agglomeration ratio of micro powder, and Y is not greater than 0.25; the unit of Dv1′ is micrometers; Dv1′ was obtained according to the test method of "GB / T 19077-2016 Particle size distribution by laser diffraction", without ultrasonic dispersion.

[0009] In an optional embodiment, the single-crystal ternary cathode material further satisfies at least one of the following requirements: (1) Z = (Dv1′ - Dv1) * (Dv50′ - Dv50); where Dv50′ is in micrometers; Z represents the overall agglomeration of the single-crystal ternary cathode material, and Z is not greater than 0.1 μm. 2 ; Dv50′ was obtained according to GB / T 19077-2016 Particle size distribution by laser diffraction method, without ultrasonic dispersion during the test; (2) P=Y*V, where P represents the microbubble production capacity, and P is no greater than 1.10 mm. 3 / g; V represents the pore volume, V is not greater than 4.5 mm. 3 / g; V was obtained according to GB / T 19587-2017 Determination of specific surface area of ​​solid materials by gas adsorption BET method.

[0010] In an optional embodiment, the single-crystal ternary cathode material further satisfies at least one of the following requirements: (1) X is 0.2-0.45; (2) Y is 0.05-0.25; (3) Z is 0.01-0.1μm 2 ; (4) P is 0.04-1.10 mm 3 / g.

[0011] In a second aspect, the present invention provides a method for preparing a single-crystal ternary cathode material according to any of the foregoing embodiments, comprising: vacuuming a single-crystal cathode material; Then it is mixed with a mixed salt solution containing nickel, manganese, cobalt, and lithium and subjected to heat preservation and pressure treatment; Next, the temperature and pressure are lowered and increased to room temperature and pressure; then the salt is washed away. Then, the washed material is sintered a second time.

[0012] In an optional embodiment, the preparation step of the mixed salt solution includes: mixing lithium nitrate, nickel nitrate, manganese nitrate, cobalt nitrate and water at 70-90°C; The molar amount of lithium nitrate is 1.1-1.5 times the sum of the molar amounts of nickel nitrate, manganese nitrate, and cobalt nitrate. The molar amount of water is 1.1 to 1.5 times the sum of the molar amounts of lithium nitrate, nickel nitrate, manganese nitrate, and cobalt nitrate.

[0013] In an optional embodiment, the preparation steps of the sintered single-crystal cathode material include: mixing a nickel-cobalt-manganese precursor and a lithium source for a single sintering, cooling, pulverizing, and sieving.

[0014] In an optional embodiment, the conditions for preparing the sintered single-crystal cathode material meet the following requirements: (1) The nickel-cobalt-manganese precursor is selected from any one of the compounds shown in the following structural formulas: Ni x Mn y Co 1 -x-y O or Ni x Mn y Co 1-x-y (OH)2, where x and y are 0-1 and x+y≤1, respectively; (2) The ratio of the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese precursor to the molar amount of lithium in the lithium source is 1: (1.02-1.10). (3) The oxygen volume content during the first sintering process is ≥20%; the gas flow rate during the first sintering process is 0.15-10.0 L / min; (4) The sintering process includes: pre-sintering at 450-550℃ for 2-5 hours, then heating up to 850-950℃ at a heating rate of 2-5℃ / min for 3-5 hours, and cooling down to 700-880℃ for 6-30 hours within 30-80 minutes.

[0015] In an optional embodiment, the Dv50 of the single-crystal cathode material is 2.0-5.0 μm, wherein the Dv50 is obtained according to the test of "GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method", and ultrasonic dispersion is used during the test.

[0016] In an optional embodiment, the conditions for preparing the single-crystal ternary cathode material meet the following requirements: (1) Evacuate to a pressure of 30-70 kPa; (2) The conditions for heat preservation and pressure preservation include: pressure of 30-70 kPa, temperature of 70-90℃, and time of 10-20 min; (3) The cooling and pressurization method is natural cooling and pressurization; (4) The conditions for secondary sintering include: oxygen volume content ≥20%; gas flow rate during secondary sintering is 0.15-10.0 L / min; (5) The secondary sintering process includes heating to 850-950℃ at a heating rate of 2-5℃ / min and sintering for 8-16 hours.

[0017] Thirdly, the present invention provides a cathode slurry comprising the single-crystal ternary cathode material described in any of the foregoing embodiments.

[0018] The present invention has the following beneficial effects: (1) The single crystal ternary cathode material provided by the present invention has a low content of micro powder and is easy to disperse. It can significantly reduce the amount of air bubbles in the cathode slurry without the use of defoamer, thereby significantly improving the cycle life and other performance of lithium-ion batteries.

[0019] (2) The preparation method provided by the present invention can effectively remove the gas inside the particles and agglomerates by evacuating a single crystal cathode material, thereby reducing the generation of bubbles in the cathode slurry.

[0020] (3) The preparation method provided by the present invention adds a mixed salt solution and cools and pressurizes the mixture so that the salt enters the pores on the surface of the particles and the pores inside the aggregates and crystallizes and fixes itself, thereby further reducing the generation of bubbles.

[0021] (4) The preparation method provided by the present invention removes excess salt by washing and retains salt in the pores. At the same time, it further removes residual alkali on the surface of the first-burned single crystal cathode material, avoids particle fusion during secondary sintering, eliminates the need for further crushing, and further reduces the content of micro powder.

[0022] (5) The preparation method provided by the present invention utilizes secondary sintering energy to sinter the salt in the pores of particles and agglomerates into lithium nickel cobalt manganese oxide; at the same time, the agglomerated micro powder particles undergo grain boundary fusion at high temperature to form larger particles. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The particle size curve of the single-crystal ternary cathode material provided in Example 1 of the present invention was obtained by ultrasonic dispersion test according to "GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method"; Figure 2 The particle size curve of the single-crystal ternary cathode material provided in Embodiment 1 of the present invention is obtained by means of laser diffraction test for particle size distribution without ultrasonic dispersion according to GB / T 19077-2016. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0026] In a first aspect, the present invention provides a single-crystal ternary cathode material, wherein the single-crystal ternary cathode material meets the following requirements: (1) X = Dv1 / Dv50; where Dv1 and Dv50 are both in micrometers; X represents particle uniformity, and the larger X is, the less micropowder is present. In the embodiments of the present invention, X is not less than 0.2; preferably 0.2-0.45, for example, any value between 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 and 0.2-0.45. Among them, micropowder refers to the fine particles formed in the preparation of single-crystal ternary cathode material products. In the industry, relative ratio parameters are often used to express it, such as particle size ratio: the smaller Dv1 / Dv50 is, the higher the micropowder content. Among them, Dv1 and Dv50 are both obtained by testing according to "GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method", and ultrasonic dispersion is used during the test.

[0027] (2) Y = (Dv1′ - Dv1) / Dv1′; where Dv1′ is in micrometers; Y represents the agglomeration ratio of the micropowder. The larger Y is, the more severe the agglomeration of the micropowder, the more difficult it is to disperse during subsequent slurry preparation, and the more microbubbles are introduced into the final positive electrode slurry. In the embodiments of the present invention, Y is not greater than 0.25; preferably 0.05-0.25, for example, preferably any value between 0.05, 0.1, 0.15, 0.2, 0.25 and 0.05-0.25.

[0028] Dv1′ was obtained according to the test method of "GB / T 19077-2016 Particle size distribution by laser diffraction", without ultrasonic dispersion.

[0029] (3) Z = (Dv1′ - Dv1) * (Dv50′ - Dv50); where Dv50′ is in micrometers; Z represents the overall agglomeration of the single-crystal ternary cathode material. A larger value for (Dv50′-Dv50) indicates more severe agglomeration of non-micron particles, and a larger value for (Dv1′-Dv1) indicates more severe agglomeration of micron particles. Therefore, a larger Z value indicates more severe overall agglomeration, which leads to uneven dispersion during cathode slurry preparation and a higher likelihood of bubble formation. In the embodiments of this invention, Z is no greater than 0.1 μm. 2 Preferably 0.01-0.1μm 2 For example, 0.01μm 2 0.05μm 2 0.1μm 2 or 0.01-0.1μm 2 Any value between.

[0030] Dv50′ was obtained according to the test method of "GB / T 19077-2016 Particle size distribution by laser diffraction", without ultrasonic dispersion.

[0031] (4) P=Y*V, where V represents the pore volume, obtained according to GB / T 19587-2017 Determination of Specific Surface Area of ​​Solid Substances by Gas Adsorption BET Method; V is not greater than 4.5 mm. 3 / g; preferably 0.50-4.50 mm 3 / g, for example, 0.50 mm 3 / g, 1.0mm 3 / g, 1.5 mm 3 / g, 2 mm 3 / g, 2.5 mm 3 / g, 3. mm 3 / g, 3.5 mm 3 / g, 4.0 mm 3 / g, 4.5 mm3 / g or 0.5-4.5 mm 3 Any value between / g.

[0032] P represents the microbubble generation capability; the larger the P value, the easier it is to generate microbubbles during subsequent slurry preparation. Both a larger pore volume V and a higher microparticle agglomeration ratio Y will lead to easier microbubble generation during subsequent slurry preparation. Microbubbles refer to bubbles with a diameter ≥ 5 μm formed during the subsequent preparation of cathode slurry using this single-crystal ternary cathode material.

[0033] In this embodiment of the invention, P is no greater than 1.10 mm. 3 / g; preferably 0.04-1.10 mm 3 / g, for example, 0.04 mm 3 / g, 0.05 mm 3 / g, 0.06 mm 3 / g, 0.07 mm 3 / g, 0.08 mm 3 / g, 0.09 mm 3 / g, 0.1 mm 3 / g, 1.10 mm 3 / g or 0.04-1.10 mm 3 Any value between / g.

[0034] In this embodiment of the invention, when testing particle size according to GB / T 19077-2016 Particle Size Distribution by Laser Diffraction, a Malvern 3000 laser particle size analyzer was used. When ultrasonic dispersion was used, the dispersant was a saturated dispersant: saturated sodium pyrophosphate; the ultrasonic power was 40W, and the time was 100s. When ultrasonic dispersion was not used, the dispersant used was also a saturated dispersant: saturated sodium pyrophosphate.

[0035] In summary, the single-crystal ternary cathode material that meets the above requirements has a low content of micronized powder, is easy to disperse, and can significantly reduce the amount of air bubbles in the cathode slurry without the use of defoamers, thereby significantly improving the cycle life and other performance characteristics of lithium-ion batteries.

[0036] Secondly, the present invention provides a method for preparing the single-crystal ternary cathode material according to any one of the foregoing embodiments, comprising: Step 1: Select any one of the compounds shown in the following structural formulas as a nickel-cobalt-manganese precursor: Ni x Mn y Co 1 -x-y O or Ni x Mn y Co 1-x-y(OH)2, where x and y are 0-1 and x+y≤1 respectively, that is, the nickel cobalt manganese precursor can be nickel cobalt manganese oxide or nickel cobalt manganese hydroxide.

[0037] Step 2: The nickel-cobalt-manganese precursor and lithium source are uniformly mixed and sintered in a single sintering atmosphere with an oxygen volume content ≥20%. The molar ratio of the total nickel, cobalt, and manganese content in the nickel-cobalt-manganese precursor to the molar lithium content in the lithium source is 1:(1.02-1.10). The lithium source includes, but is not limited to, lithium hydroxide or lithium carbonate. The gas flow rate during the single sintering process is 0.15-10.0 L / min. The single sintering process includes: pre-sintering at 450-550℃ for 2-5 h, then heating to 850-950℃ at a rate of 2-5℃ / min for 3-5 h, and finally cooling to 700-880℃ over 30-80 min for 6-30 h. Sintering under these conditions is beneficial for the formation of a single-crystal cathode material.

[0038] Step 3: Cool the product obtained from the first sintering in Step 2 to room temperature (e.g., 20-30℃), pulverize and sieve to prepare a single-crystal cathode material with a Dv50 of 2.0-5.0 μm. V 50 was obtained according to "GB / T 19077-2016 Particle size distribution by laser diffraction method", and ultrasonic dispersion was used during the test.

[0039] Step 4: Mix lithium nitrate, nickel nitrate, manganese nitrate, and cobalt nitrate to form a mixed nitrate salt. Specifically, take nickel, cobalt, and manganese hexahydrate nitrates in a molar ratio of x:y:1-xy. Simultaneously, weigh lithium nitrate at 1.1-1.5 times the sum of the molar amounts of nickel, cobalt, and manganese, and mix them to obtain the mixed nitrate salt.

[0040] Step 5: Mix the mixed nitrates and water and heat to 70-90°C to dissolve the mixed nitrates to obtain a mixed salt solution; wherein the molar amount of water is 1.1-1.5 times the total molar amount of the lithium nitrate, nickel nitrate, manganese nitrate and cobalt nitrate.

[0041] Step 6: Vacuum treatment of the monocrystalline cathode material obtained in Step 3. Specifically, the monocrystalline cathode material obtained in Step 3 is placed in a sealed container and vacuumed until the internal pressure is 30-70 kPa.

[0042] In this embodiment of the invention, a single-crystal cathode material is obtained by sintering in one step, and then the gas inside the particles and agglomerates is removed by vacuum treatment to reduce the generation of bubbles during coating and slurry preparation.

[0043] Step 7: Mix with a mixed salt solution containing nickel, manganese, cobalt, and lithium, and then perform a heat and pressure holding treatment. Specifically, add the mixed salt solution to a sealed container and hold it at a pressure of 30-70 kPa and a temperature of 70-90°C for 10-20 minutes. The monocrystalline cathode material and the mixed salt solution are mixed at a solid-liquid ratio of 1-2.0 g / ml.

[0044] Step 8: Cool down and pressurize to room temperature and pressure; then wash to remove salt. Specifically, shut down the equipment, and allow the temperature and pressure to naturally cool down and pressurize to room temperature (20-30℃) and room pressure (about 1 standard atmosphere) with the furnace, and use pure water to wash away excess nitrates.

[0045] In this embodiment of the invention, a mixed salt solution is used, and the mixed nitrates are introduced into the pores on the particle surface and the internal pores of the agglomerates through pressurization and cooling, where they crystallize and solidify. Simultaneously, washing with pure water removes excess nitrates while retaining those within the pores. This also further removes residual alkali from the surface of the first-burned single-crystal cathode material, preventing particle fusion during the second burn and eliminating the need for further crushing, thus further reducing the micron powder content.

[0046] Step 9: Dry the washed material at 80-120℃ for 2-5 hours.

[0047] Step 10: Perform secondary sintering on the dried material. Specifically, perform secondary sintering on the dried material in an atmosphere with an oxygen volume content of ≥20%; during the sintering process, control the gas flow rate to 0.15-10.0 L / min, and raise the temperature to 850-950℃ at a heating rate of 2-5℃ / min for 8-16 hours.

[0048] In this embodiment of the invention, a secondary sintering process is carried out at a high temperature for a long time. On the one hand, the nitrates in the pores of the particles and agglomerates are sintered into lithium nickel cobalt manganese oxide. On the other hand, the agglomerated micro powder particles undergo grain boundary fusion at high temperature to form larger particles, thereby further reducing the amount of micro powder.

[0049] Step 11: Cool the product obtained from the second sintering in step 10 to room temperature to obtain the single-crystal ternary cathode material.

[0050] Thirdly, the present invention provides a cathode slurry comprising the single-crystal ternary cathode material described in any of the foregoing embodiments.

[0051] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0052] Example 1 This embodiment provides a method for preparing a single-crystal ternary cathode material, including: Step 1, select the chemical formula Ni 0.6 Mn 0.2Co 0.2 Nickel cobalt manganese hydroxide (OH)2 is used as a nickel cobalt manganese precursor.

[0053] Step 2: Following a total molar ratio of nickel, cobalt, and manganese to lithium of 1:1.02, the nickel-cobalt-manganese precursor was uniformly mixed with lithium carbonate and sintered in air. During sintering, the air flow rate was controlled at 0.15 L / min. Pre-sintering was performed at 450℃ for 5 hours, followed by a heating rate of 2℃ / min to 850℃ for 5 hours, and then a cooling rate of 780℃ over 30 minutes for 6 hours.

[0054] Step 3: Cool the product obtained from sintering in Step 2 to room temperature, crush it, and sieve it to obtain a single crystal cathode material with a Dv50 of 4.23 μm. The Dv50 was obtained according to the test of "GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method" and ultrasonic dispersion was used during the test.

[0055] Step 4: Take nickel, cobalt and manganese hexahydrate nitrates in a molar ratio of nickel, manganese and cobalt of 0.6:0.2:0.2, and take lithium nitrate at 1.1 times the sum of the molar amounts of nickel, cobalt and manganese. Mix them to obtain mixed nitrates.

[0056] Step 5: Take 1.5 times the sum of the molar amounts of nickel, cobalt, manganese, and lithium, mix it with the mixed nitrates, and heat it to 90°C to dissolve the mixed nitrates to obtain a mixed salt solution.

[0057] Step 6: Place the single-crystal cathode material obtained in Step 3 into a sealed container and evacuate it to an internal pressure of 70 kPa.

[0058] Step 7: The solid-liquid ratio of the single crystal cathode material and the mixed salt solution is 2.0 g / mL. Add the mixed salt solution to a sealed container and maintain the pressure and temperature at 70 kPa and 90 °C for 10 min.

[0059] Step 8: Naturally pressurize and cool to normal pressure and temperature, and wash with pure water to remove excess nitrates.

[0060] Step 9: Dry the washed material at 120°C for 2 hours.

[0061] Step 10: The dried material is sintered a second time in an air atmosphere; during the sintering process, the gas flow rate is controlled at 0.15L / min, and the temperature is increased to 850℃ at a heating rate of 2℃ / min for 8 hours.

[0062] Step 11: Cool the product obtained from sintering in step 10 to room temperature to obtain a single-crystal ternary cathode material.

[0063] Example 2 This embodiment provides a method for preparing a single-crystal ternary cathode material, including: Step 1, select the chemical formula Ni 0.8 Mn 0.1 Co 0.1 Nickel cobalt manganese hydroxide (OH)2 is used as a nickel cobalt manganese precursor; Step 2: Following a total molar ratio of nickel, cobalt, and manganese to lithium of 1:1.05, the nickel-cobalt-manganese precursor was uniformly mixed with lithium hydroxide and sintered under a pure oxygen atmosphere. During sintering, the oxygen flow rate was controlled at 2.0 L / min. Pre-sintering was performed at 480℃ for 3 hours, followed by a heating rate of 3℃ / min to 900℃ for 4 hours, and then a cooling time of 60 minutes to 800℃ for 18 hours.

[0064] Step 3: Cool the product obtained from sintering in Step 2 to room temperature, crush it, and sieve it to obtain a single crystal cathode material with a Dv50 of 3.56 μm. The Dv50 was obtained according to the test of "GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method" and ultrasonic dispersion was used during the test.

[0065] Step 4: Take nickel, cobalt and manganese hexahydrate nitrates in a molar ratio of nickel, manganese and cobalt of 0.8:0.1:0.1, and take lithium nitrate at 1.2 times the sum of the molar amounts of nickel, cobalt and manganese. Mix them to obtain mixed nitrates.

[0066] Step 5: Take 1.2 times the sum of the molar amounts of nickel, cobalt, manganese, and lithium, mix it with the mixed nitrates, and heat it to 80°C to dissolve the mixed nitrates to obtain a mixed salt solution.

[0067] Step 6: Place the single-crystal cathode material obtained in Step 3 into a sealed container and evacuate it to an internal pressure of 60 kPa.

[0068] Step 7: The solid-liquid ratio of the single crystal cathode material and the mixed salt solution is 1.5 g / mL. Add the mixed salt solution to a sealed container and maintain the pressure and temperature at 60 kPa and 80 °C for 15 min.

[0069] Step 8: Naturally pressurize and cool to normal pressure and temperature, and wash with pure water to remove excess nitrates.

[0070] Step 9: Dry the washed material at 100℃ for 3 hours.

[0071] Step 10: The dried material is sintered a second time in a pure oxygen atmosphere; during the sintering process, the gas flow rate is controlled at 2.0 L / min, and the temperature is increased to 900℃ at a heating rate of 3℃ / min for sintering for 12 hours.

[0072] Step 11: Cool the product obtained from sintering in step 10 to room temperature to obtain a single-crystal ternary cathode material.

[0073] Example 3 This embodiment provides a method for preparing a single-crystal ternary cathode material, including: Step 1, select the chemical formula Ni 0.5 Mn 0.3 Co 0.2 Nickel cobalt manganese hydroxide (OH)2 is used as a nickel cobalt manganese precursor.

[0074] Step 2: The nickel-cobalt-manganese precursor and lithium carbonate are uniformly mixed according to the molar ratio of total nickel, cobalt, and manganese to lithium of 1:1.1 and then sintered in air atmosphere. During the sintering process, the gas flow rate is controlled at 10.0 L / min. The pre-sintering is carried out at 550℃ for 2 hours, and then the temperature is increased to 950℃ at a heating rate of 5℃ / min for 3 hours. The temperature is then decreased to 700℃ within 80 minutes for 30 hours.

[0075] Step 3: Cool the product obtained from sintering in Step 2 to room temperature, crush it, and sieve it to obtain a single crystal cathode material for later use. Its Dv50 is 3.18 μm. The Dv50 is obtained according to "GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method" and ultrasonic dispersion is used during the test.

[0076] Step 4: Take nickel, cobalt and manganese hexahydrate nitrates in a molar ratio of nickel, manganese and cobalt of 0.5:0.3:0.2, and take lithium nitrate at 1.5 times the sum of the molar amounts of nickel, cobalt and manganese. Mix them to obtain mixed nitrates.

[0077] Step 5: Take pure water and mix it with the mixed nitrate at a ratio of 1.1 times the sum of the molar amounts of nickel, cobalt, manganese, and lithium, and heat it to 70°C to dissolve the mixed nitrate to obtain a mixed salt solution.

[0078] Step 6: Place the single-crystal cathode material obtained in Step 3 into a sealed container and evacuate it to an internal pressure of 30 kPa.

[0079] Step 7: The solid-liquid ratio of the single crystal cathode material and the mixed salt solution is 1 g / mL. Add the mixed salt solution to a sealed container and maintain the pressure and temperature at 30 kPa and 70 °C for 20 min.

[0080] Step 8: Naturally pressurize and cool to normal pressure and temperature, and wash with pure water to remove excess nitrates.

[0081] Step 9: Dry the washed material at 80℃ for 5 hours.

[0082] Step 10: The dried material is sintered a second time in an air atmosphere; during the sintering process, the gas flow rate is controlled at 10.0 L / min, and the temperature is increased to 950℃ at a heating rate of 5℃ / min for sintering for 16 hours.

[0083] Step 11: Cool the product obtained from sintering in step 10 to room temperature to obtain a single-crystal ternary cathode material.

[0084] Example 4 This embodiment provides a method for preparing a single-crystal ternary cathode material, including: Step 1, select the chemical formula Ni 0.6 Mn 0.2 Co 0.2 Nickel cobalt manganese hydroxide (OH)2 is used as a nickel cobalt manganese precursor.

[0085] Step 2: Following a total molar ratio of nickel, cobalt, and manganese to lithium of 1:1.05, the nickel-cobalt-manganese precursor was uniformly mixed with lithium carbonate and sintered in air. During sintering, the gas flow rate was controlled at 10.0 L / min. Pre-sintering was performed at 550℃ for 2 hours, followed by a heating rate of 5℃ / min to 950℃ for 3 hours, and then a cooling time of 80 minutes to 700℃ for 30 hours.

[0086] Step 3: Cool the product obtained from sintering in Step 2 to room temperature, crush it, and sieve it to obtain a single crystal cathode material with a Dv50 of 3.82 μm. The Dv50 was obtained according to the test of "GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method" and ultrasonic dispersion was used during the test.

[0087] Step 4: Take nickel, cobalt and manganese hexahydrate nitrates in a molar ratio of 0.6:0.2:0.2, and take lithium nitrate at 1.3 times the sum of the molar amounts of nickel, cobalt and manganese. Mix them to obtain mixed nitrates.

[0088] Step 5: Take pure water and mix it with the mixed nitrate at a ratio of 1.3 times the sum of the molar amounts of nickel, cobalt, manganese, and lithium, and heat it to 80°C to dissolve the mixed nitrate to obtain a mixed salt solution.

[0089] Step 6: Place the single-crystal cathode material obtained in Step 3 into a sealed container and evacuate it to an internal pressure of 60 kPa.

[0090] Step 7: The solid-liquid ratio of the single crystal cathode material and the mixed salt solution is 1 g / mL. Add the mixed salt solution to a sealed container and maintain the pressure and temperature at 60 kPa and 80 °C for 16 min.

[0091] Step 8: Naturally pressurize and cool to normal pressure and temperature, and wash with pure water to remove excess nitrates.

[0092] Step 9: Dry the washed material at 120°C for 2 hours.

[0093] Step 10: The dried material is sintered a second time in an air atmosphere; during the sintering process, the gas flow rate is controlled at 5.0 L / min, and the temperature is increased to 880℃ at a heating rate of 4℃ / min for sintering for 12 hours.

[0094] Step 11: Cool the product obtained from sintering in step 10 to room temperature to obtain a single-crystal ternary cathode material.

[0095] Example 5 This embodiment provides a method for preparing a single-crystal ternary cathode material, including: Step 1, select the chemical formula Ni 0.5 Mn 0.3 Co 0.2 Nickel cobalt manganese hydroxide (OH)2 is used as a nickel cobalt manganese precursor.

[0096] Step 2: The nickel-cobalt-manganese precursor and lithium carbonate are uniformly mixed according to the molar ratio of total nickel, cobalt, and manganese to lithium of 1:1.1 and then sintered in air atmosphere. During the sintering process, the gas flow rate is controlled at 5.0 L / min. The pre-sintering is carried out at 500℃ for 3 hours, then the temperature is increased to 900℃ at a heating rate of 3℃ / min for 4 hours, and then the temperature is decreased to 800℃ for 18 hours within 60 minutes.

[0097] Step 3: Cool the product obtained from sintering in Step 2 to room temperature, crush it, and sieve it to obtain a single crystal cathode material with a Dv50 of 3.74 μm. The Dv50 was obtained according to the test of "GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method" and ultrasonic dispersion was used during the test.

[0098] Step 4: Take nickel, cobalt and manganese hexahydrate nitrates in a molar ratio of nickel, manganese and cobalt of 0.5:0.3:0.2, and take lithium nitrate at 1.4 times the sum of the molar amounts of nickel, cobalt and manganese. Mix them to obtain mixed nitrates.

[0099] Step 5: Take pure water and mix it with the mixed nitrate at a ratio of 1.1 times the sum of the molar amounts of nickel, cobalt, manganese, and lithium, and heat it to 75°C to dissolve the mixed nitrate to obtain a mixed salt solution.

[0100] Step 6: Place the single-crystal cathode material obtained in Step 3 into a sealed container and evacuate it to an internal pressure of 48 kPa.

[0101] Step 7: The solid-liquid ratio of the single crystal cathode material and the mixed salt solution is 1.0 g / mL. Add the mixed salt solution to a sealed container and maintain the pressure and temperature at 48 kPa and 75 °C for 18 min.

[0102] Step 8: Naturally pressurize and cool to normal pressure and temperature, and wash with pure water to remove excess nitrates.

[0103] Step 9: Dry the washed material at 100℃ for 3 hours.

[0104] Step 10: The dried material is sintered a second time in an air atmosphere; during the sintering process, the gas flow rate is controlled at 5.0 L / min, and the temperature is increased to 950℃ at a heating rate of 3℃ / min for 8 hours.

[0105] Step 11: Cool the product obtained from sintering in step 10 to room temperature to obtain a single-crystal ternary cathode material.

[0106] Example 6 This embodiment provides a method for preparing a single-crystal ternary cathode material, including: Step 1, select the chemical formula Ni 0.6 Mn 0.2 Co 0.2 O-cobalt-manganese oxides are used as nickel-cobalt-manganese precursors.

[0107] Step 2: According to the molar ratio of total nickel, cobalt, and manganese to lithium of 1:1.08, the nickel, cobalt, and manganese precursor is uniformly mixed with lithium hydroxide and sintered in an atmosphere with an oxygen volume content ≥90%. During the sintering process, the gas flow rate is controlled at 8.0 L / min, and the pre-sintering is carried out at 480℃ for 2.5 h. Then, the temperature is increased to 880℃ at a heating rate of 2.5℃ / min and sintered for 3.5 h. Finally, the temperature is decreased to 780℃ and sintered for 20 h within 60 min.

[0108] Step 3: Cool the product obtained from sintering in Step 2 to room temperature, crush it, and sieve it to obtain a single crystal cathode material with a Dv50 of 3.73 μm. The Dv50 was obtained according to the test of "GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method" and ultrasonic dispersion was used during the test.

[0109] Step 4: Take nickel, cobalt and manganese hexahydrate nitrates in a molar ratio of nickel, manganese and cobalt of 0.6:0.2:0.2, and take lithium nitrate at 1.45 times the sum of the molar amounts of nickel, cobalt and manganese. Mix them to obtain mixed nitrates.

[0110] Step 5: Take 1.5 times the sum of the molar amounts of nickel, cobalt, manganese, and lithium, mix it with the mixed nitrates, and heat it to 78°C to dissolve the mixed nitrates to obtain a mixed salt solution.

[0111] Step 6: Place the single-crystal cathode material obtained in Step 3 into a sealed container and evacuate it to an internal pressure of 40 kPa.

[0112] Step 7: The solid-liquid ratio of the single crystal cathode material and the mixed salt solution is 1.2 g / mL. Add the mixed salt solution to a sealed container and maintain the pressure and temperature at 40 kPa and 78 °C for 12 min.

[0113] Step 8: Naturally pressurize and cool to normal pressure and temperature, and wash with pure water to remove excess nitrates.

[0114] Step 9: Dry the washed material at 110℃ for 2.5 hours.

[0115] Step 10: The dried material is subjected to secondary sintering in an atmosphere with an oxygen volume content of ≥90%; during the sintering process, the gas flow rate is controlled at 2.0L / min, and the temperature is increased to 880℃ at a heating rate of 2.5℃ / min for sintering for 13h.

[0116] Step 11: Cool the product obtained from sintering in step 10 to room temperature to obtain a single-crystal ternary cathode material.

[0117] Example 7 Example 7 refers to the preparation method of single-crystal ternary cathode material provided in Example 2. The only difference between this preparation method and Example 2 is that the secondary sintering time in step 10 is 24 hours.

[0118] Comparative Example 1 This comparative example provides a method for preparing a single-crystal ternary cathode material. The difference between this method and Example 2 is that steps 4-11 are omitted. Specifically, it includes: Step 1, select the chemical formula Ni 0.8 Mn 0.1 Co 0.1 Nickel cobalt manganese hydroxide (OH)2 is used as a nickel cobalt manganese precursor.

[0119] Step 2: The nickel-cobalt-manganese precursor and lithium hydroxide are uniformly mixed according to the molar ratio of total nickel, cobalt, and manganese to lithium of 1:1.05 and then sintered in a pure oxygen atmosphere. During the sintering process, the gas flow rate is controlled at 2.0 L / min. The pre-sintering is carried out at 480℃ for 3 hours, and then the temperature is increased to 900℃ at a heating rate of 3℃ / min for 4 hours. The temperature is then decreased to 800℃ within 60 minutes for 18 hours of sintering.

[0120] Step 3: Cool the product obtained from sintering in Step 2 to room temperature, crush it, and sieve it to obtain a single-crystal ternary cathode material.

[0121] Comparative Examples 2-4 Comparative Examples 2-4 each provide a method for preparing a single-crystal ternary cathode material. Compared with Example 2, these methods differ only in some operating conditions; the remaining operations and conditions are identical to those in Example 2. Details are as follows: The only difference between Comparative Example 2 and Example 2 is that the lithium nitrate used in step 4 is only 0.8 times the sum of the molar amounts of nickel, cobalt, and manganese.

[0122] The only difference between Comparative Example 3 and Example 2 is that the pure water used in step 5 is 3 times the sum of the molar amounts of nickel, cobalt, manganese, and lithium.

[0123] The only difference between Comparative Example 4 and Example 2 is that the second sintering time in step 10 is only 3 hours.

[0124] test The single-crystal ternary cathode materials prepared in Examples 1-7 and Comparative Examples 1-4 were tested using the following methods: (1) Dv1 and Dv50 were measured by ultrasonic dispersion in accordance with GB / T 19077-2016 Particle size distribution by laser diffraction. The dispersant was saturated sodium pyrophosphate (i.e., the dispersant concentration was saturated); a Malvern 3000 laser particle size analyzer was used; the ultrasonic power was 40W and the time was 100s.

[0125] (2) When testing according to GB / T 19077-2016 Particle size distribution by laser diffraction, ultrasonic dispersion was not used, and Dv1′ and Dv50′ were measured. The dispersant was a saturated dispersant: saturated sodium pyrophosphate (i.e., the dispersant concentration was saturated); a Malvern 3000 laser particle size analyzer was used.

[0126] (3) The pore volume V of the particles was tested using a BSD-660S according to GB / T 19587-2017 Determination of specific surface area of ​​solid substances by gas adsorption BET method.

[0127] See test results Figure 1 and Figure 2 And the following table:

[0128] according to Figure 1 , Figure 2 As can be seen from the table above, (1) the difference between Comparative Example 2 and Example 2 is that the lithium nitrate used in step 4 is only 0.8 times the sum of the molar amounts of nickel, cobalt and manganese. Therefore, the lithium source is insufficient during the secondary sintering, the grain boundaries are difficult to fuse, the micro powder content is still high, the micro powder agglomeration is still serious, and it is easier to generate micro bubbles.

[0129] (2) The only difference between Comparative Example 3 and Example 2 is that the pure water used in step 5 is 3 times the sum of the molar amounts of nickel, cobalt and manganese. The concentration of nickel, cobalt, manganese and lithium is low, which makes it difficult for the agglomerates to undergo grain boundary fusion during secondary sintering. The Y value is high, and it cannot effectively fill the pore volume, and it is also more likely to generate micro bubbles.

[0130] (3) The only difference between Comparative Example 4 and Example 2 is that the second sintering time in step 10 is only 3 hours. The time is too short, and the micro powder agglomerates of small particles cannot be fused together, resulting in a high micro powder content.

[0131] Test case The single-crystal ternary cathode materials of Examples 1-7 and Comparative Examples 1-4 were processed as follows: (1) Dissolve 30g PVDF in 270g NMP solvent and disperse it by double planetary stirring at 1000r / min for 100min to prepare a viscose solution; (2) 950g of single-crystal ternary cathode material and 245g of NMP solvent were added to the above adhesive solution and dispersed by double planetary high-speed stirring at 1200r / min for 150min to obtain slurry; (3) The slurry was coated onto a 16μm aluminum foil using a coating machine, and dried under vacuum at 120℃ for 2 hours. The electrode was then rolled and cut to obtain a 595mm (length) × 56mm (width) × 145μm (thickness) sheet.

[0132] The slurries and electrodes prepared in the above embodiments and comparative examples were subjected to the following performance tests, and the test results are shown in the table below.

[0133] ① Bubble density: Take a 1cm sample of slurry from step (2) 3 The number of bubbles with a diameter ≥5μm was counted using an optical microscope (Olympus BX53). ②Pinhole defect rate: Take the electrode sheet from step (3) and scan it with a high-resolution optical inspection instrument (Keyence VR-3200) to count the number of pinholes.

[0134]

[0135] Based on the above results, it can be seen that for single-crystal ternary cathode materials that do not meet the requirements of this invention, the greater the bubble density and pinhole defects in the prepared slurry and electrode sheet, for example, the greater the P, the more bubbles and pinholes are generated.

[0136] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A single-crystalline ternary cathode material, characterized in that, The single-crystal ternary positive electrode material meets the following requirements: (1) X=Dv1 / Dv50; wherein X represents particle consistency, and X is not less than 0.2; the units of Dv1 and Dv50 are microns; Dv1 and Dv50 are obtained by testing according to “GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method”, and ultrasonic dispersion is used during testing; (2) Y=(Dv1'-Dv1) / Dv1'; wherein Y represents a fine powder agglomeration ratio, and Y is not greater than 0.25; the unit of Dv1' is micron; Dv1' is obtained by testing according to “GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method”, and ultrasonic dispersion is not used during testing.

2. The single-crystalline ternary cathode material of claim 1, wherein, The single-crystal ternary positive electrode material also meets at least one of the following requirements: (1) Z = (Dv1'-Dv1)*(Dv50'-Dv50); wherein, Dv50' is in units of microns; Z represents the overall agglomeration of the single-crystal ternary positive electrode material, Z is not greater than 0.1 μm 2 ; Dv50' is obtained by testing according to “GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method”, and ultrasonic dispersion is not used during testing. (2) P = Y*V, P represents the microbubble production capacity, P is not greater than 1.10 mm 3 / g; V represents the pore volume, V is not greater than 4.5 mm 3 / g; V is obtained by testing according to “GB / T 19587-2017 Gas Adsorption BET Method for Determining Specific Surface Area of Solid Substances”.

3. The single-crystalline ternary cathode material of claim 2, wherein, The single-crystal ternary positive electrode material also meets at least one of the following requirements: (1) X is 0.2-0.45; (2) Y is 0.05-0.25; (3) Z is 0.01-0.1 μm 2 ; (4) P is 0.04 to 1.10 mm 3 / g.

4. A method for producing the single-crystal ternary cathode material according to any one of claims 1 to 3, characterized in that, The preparation steps of the single-crystal positive electrode material include: vacuumizing the single-crystal positive electrode material; then mixing with a mixed salt solution containing nickel, manganese, cobalt and lithium for heat preservation and pressure preservation; then, the temperature and pressure are increased to normal temperature and normal pressure; and then the salt is removed by washing; then, the washed material is subjected to secondary sintering.

5. The production method according to claim 4, characterized by, The preparation steps of the mixed salt solution include: mixing lithium nitrate, nickel nitrate, manganese nitrate, cobalt nitrate and water at 70-90°C; wherein the molar amount of lithium nitrate is 1.1-1.5 times the total molar amount of nickel nitrate, manganese nitrate and cobalt nitrate; 6. The preparation method according to claim 4, characterized in that, the molar amount of water is 1.1-1.5 times the total molar amount of lithium nitrate, nickel nitrate, manganese nitrate and cobalt nitrate.

7. The production method according to claim 6, wherein The preparation steps of the single-crystal positive electrode material include: mixing nickel-cobalt-manganese precursor and lithium source for primary sintering, cooling, crushing and screening. Ni x Mn y Co 1 -x-y O or Ni x Mn y Co 1-x-y (OH)2, wherein x and y are each 0-1, x+y≤1; The conditions for preparing the single-crystal positive electrode material meet the following requirements: (1) the nickel-cobalt-manganese precursor is selected from any one of the compounds represented by the following structural formula: (2) the ratio of the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese precursor to the molar amount of lithium in the lithium source is 1:(1.02-1.10); 8. The preparation method according to claim 6, characterized in that, (3) the oxygen volume content during primary sintering is greater than or equal to 20%; the gas flow during primary sintering is 0.15-10.0 L / min; (4) the process of primary sintering includes: pre-sintering at 450-550°C for 2-5h, then sintering at 850-950°C for 3-5h at a temperature increasing rate of 2-5°C / min, and then sintering at 700-880°C for 6-30h by cooling to 700-880°C within 30-80min. The Dv50 of the single-crystal positive electrode material is 2.0-5.0μm, wherein the Dv50 is obtained by testing according to “GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method”, and ultrasonic dispersion is used during testing.

9. The method of any one of claims 4-8, wherein, The conditions for preparing the single-crystal ternary cathode material meet the following requirements: (1) vacuum extraction to a pressure of 30-70 Kpa; (2) the conditions for heat preservation and pressure preservation include: a pressure of 30-70 Kpa, a temperature of 70-90 ℃, and a time of 10-20 min; (3) the mode for temperature reduction and pressure increase is natural temperature reduction and pressure increase; (4) the conditions for secondary sintering include: an oxygen volume content of ≥20%, and a gas flow of 0.15-10.0 L / min during the secondary sintering process; (5) the secondary sintering process includes: sintering at a temperature of 850-950 ℃ for 8-16 h at a temperature increase rate of 2-5 ℃ / min.

10. A positive electrode slurry, characterized by, The single-crystal ternary cathode material according to any one of claims 1-3.

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