Single-crystal multi-element positive electrode material, its manufacturing method, and lithium-ion battery

Abstract

The present invention discloses a single crystal multi-element positive electrode material, a manufacturing method thereof, and a lithium ion battery. The ratio of the length of the longest diagonal line to the length of the shortest diagonal line measured by SEM for a single crystal particle of the single crystal multi-element positive electrode material is defined as the circularity R, and R is 1 or more. 10 , D 50 , and D 90 But, K 90 =(D 90 -D 10 ) / D 50 and K 90 and R is 1.20 to 1.40. The single crystal multi-element positive electrode material has a rounder and more regular morphology, and the single crystal particles thereof are characterized by uniform size, less aggregation, less adhesion, high compression density, good rate characteristics, and excellent cycle characteristics.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims the benefit of Chinese Patent Application No. 202211659558.1 filed on December 22, 2022, the content of which is incorporated herein by reference.

[0002] Technical Field The present invention relates to the field of manufacturing of cathode materials, and specifically to single - crystal type multi - element cathode materials, a manufacturing method thereof, and lithium - ion batteries.

Background Art

[0003] Lithium - ion batteries have excellent advantages such as high voltage, large energy density, good cycle characteristics, low self - discharge, and no memory effect. As an important component of lithium - ion batteries, the cathode material plays a decisive role in the capacity, characteristics, and cost of the battery. Nickel - cobalt - manganese composite materials are one of the most popular cathode materials for lithium - ion batteries and have a high capacity per gram and good cycle stability. Multi - element cathode materials can be divided into an aggregated type and a single - crystal type according to the state of particle existence. Aggregated multi - element cathode materials have a big problem in the processing process because spherical particles are easily cracked during roll pressing, and the electrolyte penetrates between the cracked particles, causing a series of side effects. Designing the cathode material into a more stable single - crystal structure can effectively avoid the above problems.

[0004] Conventional single-crystalline cathode materials are affected by the limitations of conditions during the manufacturing process, especially the influence of the sintering atmosphere. The corners of single-crystalline particles are obvious, the roundness and regularity are poor, or the adhesion between the crystal grains of the single crystal is serious, the independence of the crystal grains is poor, and the morphology of the precursor is even retained. This is because in the prior art, sintering is often carried out using a single atmosphere (air or oxygen gas). Sintering in pure air can reduce processing costs, but under air conditions, it is difficult for lithium salts to melt and penetrate into the particles, covering the particle surface and easily forming irregular primary particles during the heating and growth stage. In the heat preservation and fusion stage, lithium covering the particle surface fuses between the particles on the surface, rapidly growing the particles. The corners of the sintered single-crystalline particles are obvious, the roundness and regularity are poor, and irregular particles are more likely to crack during the roll pressing process of the electrode plate, or pierce through the separator during assembly, deteriorating the cycle characteristics of the battery and causing a sudden drop in capacity. On the other hand, adopting sintering in pure oxygen not only increases the processing cost, but also because lithium salts fuse inside the particles under an oxygen gas atmosphere, primary particles are formed relatively round and regularly during the heating stage, but during the heat preservation stage, it is difficult for the particles to fuse together, and it is difficult for the particles to grow into single crystals, or the adhesion between the formed crystal particles is serious, the independence of the crystal grains is poor, and the morphology of the precursor is even retained.

[0005] Therefore, it is important to provide a single-crystalline cathode material with a round shape, uniform size, less aggregation, and less adhesion, as well as a manufacturing method suitable for its industrial production.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The object of the present invention is to solve the problems existing in the prior art, namely, the non-uniform crystal grain size of the single-crystalline cathode material, the easy adhesion between particles, and the poor roundness and regularity of the single crystal.

Means for Solving the Problems

[0007] In order to achieve the above object, in a first aspect of the present invention, the ratio of the length of the longest diagonal line to the length of the shortest diagonal line measured by SEM for single crystal particles of a single crystal multi-component cathode material is defined as the circularity R, and R is 1 or more, D of the single crystal particles of the single crystal multi-component cathode material 10 , D 50 , and D 90 satisfy K 90 = (D 90 - D 10 ) / D 50 , and the product of K 90 and R is 1.20 to 1.40, and a single crystal multi-component cathode material is provided.

[0008] A second aspect of the present invention is Step (1) of subjecting a mixture containing a nickel-cobalt-manganese precursor and a lithium source to a first sintering, crushing the obtained product, and obtaining a single crystal cathode material intermediate; Step (2) of subjecting the single crystal cathode material intermediate to a second sintering to obtain a single crystal multi-component cathode material, The first sintering includes a temperature rising stage I and a heat preservation stage I that are sequentially performed. The temperature rising stage I is performed in an oxygen gas atmosphere, and the heat preservation stage I is performed in an air atmosphere. A method for manufacturing a single crystal multi-component cathode material is provided, wherein the temperature of the second sintering is lower than the temperature of the first sintering.

[0009] A third aspect of the present invention provides a single crystal type multi-component cathode material manufactured by the manufacturing method described in the second aspect.

[0010] A fourth aspect of the present invention provides a lithium ion battery containing the single crystal type multi-component cathode material described in the first aspect or the third aspect.

[0011] According to the above technical solution, the manufacturing method according to the present invention optimizes the sintering process. Therefore, in the first sintering process, in the heating stage, an oxygen gas atmosphere is used, and in the heat preservation stage, an air atmosphere is used to optimize the single crystal form. In addition, the single crystal type multi-component cathode material obtained in combination with the second sintering has specific roundness and uniformity. Its single crystal particles have a more rounded and regular shape, uniform size, less aggregation, and less adhesion. When using this to manufacture an electrode, the compression density is higher, and it is less likely to crack or fall off during processing or battery cycling. As a result, the energy density, rate performance, and cycle stability of the battery are improved.

[0012] Furthermore, the single crystal cathode material is superior to the non-single crystal cathode material in terms of cycle life, rate performance, stability, safety, and processability.

Brief Description of the Drawings

[0013]

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Modes for Carrying Out the Invention

[0014] The endpoints and any values within the ranges disclosed in this specification are not limited to the exact ranges or values, but should be understood to include values close to these ranges or values. In the case of numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this specification.

[0015] In the present invention, unless otherwise explicitly stated, neither "first" nor "second" represents an order, nor restricts individual materials or operations, but only serves to distinguish individual materials or operations. For example, "first" and "second" in "first sintering" and "second sintering" only indicate that they are not the same sintering operation.

[0016] Unless otherwise specified, the room temperature in the present invention means 25 ± 2°C.

[0017] The first aspect of the present invention provides a single-crystalline multi-component cathode material. For the single-crystalline particles of the single-crystalline multi-component cathode material, the ratio of the length of the longest diagonal line to the length of the shortest diagonal line measured by SEM is defined as the circularity R, and R is 1 or more. The D 10 , D 50 , and D 90 satisfy K 90 = (D 90 - D 10 ) / D 50 , and the product of K 90 and R is 1.20 to 1.40.

[0018] In a single-crystalline cathode material, the superiority or inferiority of its single-crystalline structure directly affects the electrochemical properties of the cathode material. As a result of research, the inventor found that in a single-crystalline multi-component cathode material that satisfies the above specific parameters, its morphology is more round and regular, the particle size is uniform, there is less aggregation and adhesion, the compression density when manufacturing an electrode using the cathode material is higher, cracks and detachment are less likely to occur during processing and battery cycling, which is advantageous for improving the energy density and cycle stability of the battery.

[0019] According to some embodiments of the present invention, for the single crystal particles of the single crystal type multi-component cathode material, the ratio of the length of the longest diagonal line to the length of the shortest diagonal line measured by SEM is defined as the roundness R, and R is 1 or more. The closer the R value is to 1, the closer the lengths of the longest diagonal line and the shortest diagonal line of the single crystal particles are, indicating that the morphology of the material is more round and regular. More round and regular single crystal particles are advantageous for preventing cracking of the cathode material during roll pressing of the electrode plate and for preventing the irregular corners of the cathode material from piercing the separator when assembling the battery, which is advantageous for improving the safety and cycle characteristics of the battery. In the present invention, R is a statistical result obtained by randomly selecting 300 single crystal particles from the SEM image as samples.

[0020] According to some embodiments of the present invention, preferably, R is 1 to 1.2. The single crystal particles of the single crystal type multi-component cathode material according to the above preferred embodiment have a more round and regular morphology, which is advantageous for further improving the safety and cycle characteristics of the battery.

[0021] According to some embodiments of the present invention, for the single crystal particles of the single crystal type multi-component cathode material, the particle size corresponding to 10% of the volume distribution obtained by performing a particle size test is D 10 , the particle size corresponding to 50% of the volume distribution is D 50 , and the particle size corresponding to 90% of the volume distribution is D 90 . Defined as such, when the uniformity of the single crystal type multi-component cathode material is defined as K 90 , then K 90 = (D 90 - D 10 ) / D 50 , and the product of K 90 and R is 1.20 to 1.40.

[0022] According to some embodiments of the present invention, preferably, the product of K 90 and R is 1.25 to 1.35. The single crystal type multi-component cathode material according to the above preferred embodiment has a high capacity and cycle retention rate, and is also advantageous for further improving the compression density of the cathode material.

[0023] According to some embodiments of the present invention, preferably, the particle size D of the single crystal type multi-component cathode material 10 is 1.5 to 2.5 μm.

[0024] According to some embodiments of the present invention, preferably, the particle size D of the single crystal type multi-component cathode material 50 is 3 to 5 μm.

[0025] According to some embodiments of the present invention, preferably, the particle size D of the single crystal type multi-component cathode material 90 is 6 to 8 μm.

[0026] In the present invention, the particle size test is performed using a laser particle size analyzer of the Hydro 2000mu model number of Malvern.

[0027] According to some embodiments of the present invention, the smaller the value of K 90 , the better the uniformity of the single crystal particles. The larger the value of K 90 , the worse the uniformity of the single crystal particles. Preferably, K 90 is 1.18 to 1.25, preferably 1.20 to 1.22. The single crystal type multi-component cathode material according to the above preferred embodiments has better uniformity of single crystal particles, increases the gradation, and is advantageous for increasing the compression density of the material.

[0028] According to some embodiments of the present invention, preferably, the single crystal type multi-component cathode material has a structure represented by Formula I. Li 1+a (Ni x Co y Mn z G b )M c O 2-d Formula I (where -0.05 ≦ a ≦ 0.3, 0 ≦ b ≦ 0.05, 0 ≦ c ≦ 0.05, 0.5 ≦ x < 1, 0 < y < 0.5, 0 < z < 0.5, the value of d ensures an equal number of positive and negative charges, G is one or more of Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, B, Mg, Co, F, and Y, M is one or more of Sr, F, B, Al, Nb, Co, Mn, Mo, W, Si, Mg, Ti, and Zr, More preferably, in the formula, 0 ≦ a ≦ 0.2, 0.0001 ≦ b ≦ 0.005, 0.0001 ≦ c ≦ 0.005, 0.5 ≦ x ≦ 0.95, 0.01 ≦ y ≦ 0.4, 0.01 ≦ z ≦ 0.4. More preferably, in the formula, G is one or more of Ti, W, Zr, Sr, Si, Al, B, and F, and / or M is one or more of Sr, F, B, Al, W, Si, and Ti.)

[0029] According to the above preferred embodiments, it is advantageous for further improving the energy density, rate characteristics, and cycle stability of the battery.

[0030] According to some embodiments of the present invention, in Formula I, if both G and M are cations, then d = 0; if both G and M are anions, then d = b + c; if G is an anion and M is a cation, then d = b; if M is an anion and G is a cation, then d = c.

[0031] According to some embodiments of the present invention, preferably, for the agglomeration rate of the single-crystalline multi-component cathode material, when defined as B, where n is the number of single-crystalline particles having an agglomerated form among any 300 single-crystalline particles of the single-crystalline multi-component cathode material measured by SEM, B = n / 300 * 100%, and B is 0 to 3.0%, preferably 0.8 to 2.4%. The larger the agglomeration rate B, the lower the level of single-crystallinity of the cathode material, and conversely, the higher the level of single-crystallinity. In the case of a high voltage or a long cycle of the battery, the adhered cathode material particles are likely to drop off or crack, resulting in a failure of the battery pack. Generally, the smaller the value of the agglomeration rate B, the better the cycle characteristics. The single-crystalline multi-component cathode material according to the above preferred embodiment has a small agglomeration rate of single-crystalline particles, a high level of single-crystallinity, little adhesion, and is less likely to drop off or crack in the case of high voltage or a long cycle, which is advantageous for further improving the energy density, rate performance, and cycle stability of the battery.

[0032] According to some embodiments of the present invention, preferably, for the single-crystalline multi-component cathode material, the average value of the longest diagonal length and the shortest diagonal length of any 300 single-crystalline particles measured by SEM is defined as the crystal grain size P 50 When defined as such, P 50 is 1.5 to 3.0 μm, preferably 2.0 to 2.4 μm. If the value of P 50 is too large, the migration distance of lithium ions inside the cathode material increases, affecting the capacity performance. The smaller the value of P 50 , the more the material agglomerates, and in some cases, a single-crystalline material cannot be formed, affecting the cycle characteristics of the material. Using the single-crystalline multi-component cathode material of the above preferred embodiment is advantageous for further improving the capacity and cycle characteristics of the single-crystalline multi-component cathode material.

[0033] In the present invention, a two-step sintering process is used in the production of the single-crystalline multi-component cathode material. In the first sintering, in the heating stage, an oxygen gas atmosphere is used, and in the heat preservation stage, an air atmosphere is used. As a result, the single-crystalline particles have a more rounded and regular morphology, more uniform size, less aggregation and adhesion, higher compression density, which is advantageous for improving the battery energy density, rate performance, and cycle stability.

[0034] A second aspect of the present invention provides a method for producing a single-crystalline multi-component cathode material, the production method comprising: Step (1) of subjecting a mixture containing a nickel-cobalt-manganese precursor and a lithium source to a first sintering, and crushing the obtained product to obtain a single-crystalline cathode material intermediate; Step (2) of subjecting the single-crystalline cathode material intermediate to a second sintering to obtain a single-crystalline multi-component cathode material. The first sintering includes a heating stage I and a heat preservation stage I that are sequentially performed. The heating stage I is performed under an oxygen gas atmosphere, and the heat preservation stage I is performed under an air atmosphere. The temperature of the second sintering is lower than the temperature of the first sintering.

[0035] Most of the conventional methods for manufacturing single-crystal cathode materials perform sintering using a single atmosphere (air or oxygen gas). Therefore, the single-crystal particles have distinct corners, poor roundness and regularity, or severe adhesion between the single-crystal particles, poor independence, and still maintain a form like that of the precursor. On the other hand, as a result of research, the present inventor has found that the solid-phase reaction of the mixture of nickel-cobalt-manganese precursor and lithium source can be divided into two stages: the growth stage and the fusion stage. The growth stage is a stage of slow temperature rise, that is, the lithium source melts and penetrates into the interior of the precursor particles, and the initial reaction occurs, growing the fibers constituting the precursor into fine primary particles. The fusion stage is a stage of maintaining a high temperature, that is, a process in which the lithium source further reacts with the fine primary particles and fuses the fine primary particles into large particles. By using an oxygen gas atmosphere in the temperature-rising nucleation stage (temperature-rising stage I of the first sintering) of the reaction between the nickel-cobalt-manganese precursor and the lithium source, the primary particles formed by the fibers become rounder and fuller. By using an air atmosphere in the heat-preserving sintering growth stage (heat-preserving stage I of the first sintering), it is easier for the single-crystal particles to fuse into large single-crystal particles. By secondary sintering (the second sintering), the finished product of the cathode material particles becomes rounder and more regular, the form of the obtained single-crystal type multi-component cathode material becomes rounder and more regular, the particle size is uniform, there is less aggregation, less adhesion, a high compression density, good rate characteristics, and excellent cycle characteristics.

[0036] According to some embodiments of the present invention, in step (1), the nickel-cobalt-manganese precursor may be a nickel-cobalt-manganese precursor suitable for the manufacture of cathode materials known in the art, and there is no particular limitation thereto, and any of them can achieve the invention object of the present invention to a certain extent. Preferably, the nickel-cobalt-manganese precursor is selected from oxides and / or hydroxides containing nickel, cobalt, and manganese.

[0037] According to some embodiments of the present invention, in step (1), the lithium source may be a lithium source suitable for the production of cathode materials known in the art, and there is no particular limitation thereon, and any of them can achieve the object of the present invention to a certain extent. Preferably, the lithium source is selected from lithium carbonate and / or lithium hydroxide.

[0038] According to some embodiments of the present invention, preferably, in step (1), according to the stoichiometric ratio, the usage amount of the lithium source satisfies 1.02 ≦ [n(Li)] / [n(Ni)+n(Co)+n(Mn)] ≦ 1.06.

[0039] According to some embodiments of the present invention, preferably, in step (1), the mixed raw materials further contain an additive, and the additive is selected from compounds containing G, preferably at least one of an oxide, hydroxide, carbonate, and fluoride containing G, more preferably at least one of zirconia, strontium carbonate, strontium hydroxide, silica, alumina, aluminum hydroxide, tungsten trioxide, titanium oxide, aluminum fluoride, and boron oxide. G can be selected as described above and will not be described in detail here. In the present invention, the additive is advantageous for single crystal formation of the material, reduction of internal resistance, and improvement of cycle stability of the material.

[0040] According to some embodiments of the present invention, preferably, in step (1), according to the stoichiometric ratio, the usage amount of the additive in terms of G element satisfies 0.0001 ≦ [n(G)] / [n(Ni)+n(Co)+n(Mn)] ≦ 0.005.

[0041] According to some embodiments of the present invention, in step (1), the temperature-raising stage I is carried out in an oxygen gas atmosphere. By using an oxygen gas atmosphere in the temperature-raising nucleation stage of the reaction between the nickel-cobalt-manganese precursor and the lithium source (i.e., the temperature-raising stage I of the first sintering), the primary particles formed by fibers become rounder and fuller.

[0042] According to some embodiments of the present invention, preferably, in step (1), the conditions of the first heating stage further include that the heating time is 2 to 10 h, preferably 6 to 8 h. In the first heating stage, the temperature is raised to the heat preservation temperature of the first heat preservation stage over the above-mentioned heating time.

[0043] According to some embodiments of the present invention, in step (1), the first heat preservation stage is carried out in an air atmosphere. By using an air atmosphere in the heat preservation and sintering growth stage (the first heat preservation stage of the first sintering), it is easier for single crystal particles to fuse with each other to form larger single crystal particles.

[0044] According to some embodiments of the present invention, preferably, in step (1), the conditions of the first heat preservation stage further include that the heat preservation temperature is 600 to 1100 °C, preferably 900 to 1000 °C, and the heat preservation time is 6 to 12 h, preferably 8 to 10 h.

[0045] According to some embodiments of the present invention, preferably, in step (1), the median particle size D 50 of the nickel-cobalt-manganese precursor is 3 to 5 μm.

[0046] According to some embodiments of the present invention, preferably, in step (1), the median particle size D' 50 of the single crystal cathode material intermediate is 3 to 5 μm.

[0047] According to some embodiments of the present invention, preferably, in step (1), the median particle size D 50 of the nickel-cobalt-manganese precursor and the median particle size D' 50 of the single crystal cathode material intermediate satisfy the following formula II. |(D 50 - D' 50 ) / D 50 | < 5% Formula II

[0048] According to the above preferred embodiments, the particle size D 10 of the single crystal particles, D 50 of the single crystal particles, D 90, and uniformity K 90 A single-crystalline multi-component cathode material that satisfies the above requirements can be easily obtained.

[0049] According to some embodiments of the present invention, in step (1), by combining the first sintering and the crushing, the central particle size D' of the obtained single-crystalline cathode material intermediate 50 satisfies the above requirements. There are no particular limitations on the device used for the crushing, and as long as a single-crystalline cathode material intermediate in which the central particle size D' 50 satisfies the above requirements can be obtained. Preferably, the device used for the crushing is at least one selected from a soy milk maker, a jaw crusher, a double roller, a colloid mill, a mechanical mill, and a jet mill.

[0050] According to some embodiments of the present invention, preferably, in step (2), first, the single-crystalline cathode material intermediate and a coating agent are mixed, and then the obtained mixture is subjected to the second sintering. The coating agent is selected from compounds containing M. Preferably, it is at least one of an oxide, a hydroxide, a carbonate, and a fluoride containing M. More preferably, it is at least one of strontium carbonate, strontium hydroxide, silica, alumina, aluminum hydroxide, tungsten trioxide, titanium oxide, aluminum fluoride, and boron oxide. M may be selected as described above and will not be described in detail here. In the present invention, the coating agent is advantageous for reducing free lithium and improving the cycle stability of the material in a high-temperature and high-voltage environment.

[0051] According to some embodiments of the present invention, preferably, in step (2), according to the stoichiometric ratio, the usage amount of the coating agent in terms of M element satisfies 0.0001 ≦ [n(M)] / [n(Ni) + n(Co) + n(Mn)] ≦ 0.005.

[0052] According to some embodiments of the present invention, the usage amounts of the nickel-cobalt-manganese precursor, the lithium source, the additive, and the coating agent are such that in the obtained single-crystalline multi-component cathode material, n(Li):n(Ni):n(Co):n(Mn):n(G):n(M) = (1 + a):x:y:z:b:c, where the values of a, b, c, x, y, and z may be defined and selected as described above and will not be elaborated here.

[0053] According to some embodiments of the present invention, preferably, in step (2), the second sintering is carried out in an air atmosphere.

[0054] According to some embodiments of the present invention, preferably, in step (2), the second sintering includes a temperature-rising stage II and a heat-preserving stage II that are carried out sequentially.

[0055] According to some embodiments of the present invention, preferably, in step (2), the conditions of the temperature-rising stage II further include that the temperature-rising time is 2 to 10 h, preferably 4 to 7 h.

[0056] According to some embodiments of the present invention, preferably, in step (2), the conditions of the heat-preserving stage II further include that the heat-preserving temperature is 500 to 900 °C, preferably 600 to 800 °C, and the heat-preserving time is 6 to 12 h, preferably 8 to 10 h.

[0057] According to some embodiments of the present invention, preferably, when the change value of the crystal grain size of the single-crystalline multi-component cathode material is defined as △P (unit: μm), the change value of the temperature in the same sintering step is defined as △T (unit: °C), and the change value of the time in the same sintering step is defined as △t (unit: h), these three satisfy △P = ω△T + γ△t (ω = 0.02 μm / °C, γ = 0.1 μm / h). For example, when the heat-preserving temperature in the heat-preserving stage I of the first sintering is T1 (°C) and the heat-preserving time is t1 (h), the crystal grain size P 50 of the obtained single-crystalline multi-component cathode material is P1 (μm), and when the heat-preserving temperature in the heat-preserving stage I of the first sintering is T2 (°C) and the heat-preserving time is t2 (h), the crystal grain size P50 is P2 (μm), that is, ΔT is the absolute value of the difference between T1 and T2 (i.e., |T1 - T2| °C), Δt is the absolute value of the difference between t1 and t2 (i.e., |t1 - t2| h), ΔP is the absolute value of the difference between P1 and P2 (i.e., |P1 - P2| μm), and ΔP = ωΔT + γΔt.

[0058] The third aspect of the present invention provides a single-crystalline multi-component cathode material manufactured by the manufacturing method described in the second aspect.

[0059] According to some embodiments of the present invention, since the single-crystalline multi-component cathode material is the same as or similar to the single-crystalline multi-component cathode material described in the first aspect of the present invention, it will not be described in detail here.

[0060] The fourth aspect of the present invention provides a lithium-ion battery containing the single-crystalline multi-component cathode material described in the first aspect or the third aspect.

Examples

[0061] Hereinafter, the present invention will be described in detail by way of examples.

[0062] In the following examples and comparative examples, unless otherwise specified, all raw materials used are commercially available products.

[0063] In the following examples and comparative examples, the relevant parameters are measured by the following methods.

[0064] (1) Measurement of morphology: Measured using a scanning electron microscope of model S-4800 manufactured by Hitachi, Japan, and the circularity R, aggregation rate B, and crystal grain size P 50 are all measured from the SEM images.

[0065] (2) Particle size D 10 , D 50 , D 90 : Measured using a laser particle size analyzer of model Hydro 2000mu manufactured by Marvern.

[0066] (3) Compression density: Measured by a tap density tester of model BT-30 manufactured by Baxter.

[0067] (4) Measurement of electrochemical properties In the following examples and comparative examples, the electrochemical properties of the single-crystalline multi-component cathode material are measured using a CR2032 button-type battery. The manufacturing process of the CR2032 button-type battery is specifically as follows. Manufacture of the electrode plate: A single-crystalline multi-component cathode material, conductive carbon black, and polyvinylidene fluoride (PVDF) are thoroughly mixed in a mass ratio of 95:2:3 with an appropriate amount of N-methylpyrrolidone (NMP) to form a uniform slurry. This slurry is coated on an aluminum foil, dried at 120 °C for 12 h, and then press-molded using a pressure of 100 MPa to obtain a positive electrode plate with a diameter of 15.8 mm and a thickness of 3.2 mm. The loading amount of the single-crystalline multi-component cathode material is 15.5 mg / cm 2 is. Assembly of the battery: Inside a gas glove box filled with argon gas, where both the water content and the oxygen content are less than 5 ppm, the positive electrode plate, separator, negative electrode plate, and electrolyte are assembled into a CR2032 button-type battery and then left standing for 6 h. The negative electrode plate uses a metal lithium sheet with a diameter of 15.8 mm and a thickness of 1 mm. The separator uses a polypropylene microporous membrane (Celgard 2325) with a thickness of 25 μm, and the electrolyte uses a liquid in which 1 mol / L of LiPF6, vinyl carbonate (EC), and diethyl carbonate (DEC) are mixed in equal amounts. Measurement of electrochemical properties In the following examples and comparative examples, the electrochemical properties of the CR2032 button-type battery are measured using a battery measurement system manufactured by Shenzhen Neware Co., Ltd., and the charge-discharge current density at 0.1C is set to 100 mA / g. The voltage range of charge and discharge is controlled to 3.0 - 4.4 V, and at room temperature, the button-type battery is subjected to charge and discharge measurements at 0.1C and 0.3C respectively to evaluate the charge-discharge specific capacity of the single-crystalline multi-component cathode material. Measurement of high-temperature cycle characteristics: While maintaining the temperature at 60 °C, the voltage range of charge and discharge is controlled to 3.0 - 4.4 V, and the button-type battery is charged and discharged at 0.1C for 2 cycles and then at 1C for 80 cycles to evaluate the high-temperature cycle capacity retention rate of the single-crystalline multi-component cathode material. Measurement of rate characteristics: While controlling the voltage range of charge and discharge to 3.0 - 4.4 V at room temperature, the button-type battery is charged and discharged at 0.1C for 2 cycles, then at 0.3C for 1 cycle, and the rate characteristics of the multi-component cathode material are evaluated by the ratio of the initial discharge specific capacity at 0.1C to the discharge specific capacity at 0.3C.

[0068] Example 1 (1) A mixture containing a nickel-cobalt-manganese precursor, a lithium source, and an additive was subjected to a first sintering, and the obtained product was crushed to obtain a single-crystalline cathode material intermediate. The nickel-cobalt-manganese precursor is a hydroxide containing nickel, cobalt, and manganese, whose chemical formula is shown in Table 2. The types of the lithium source and the additive and the usage amounts of each raw material are shown in Table 1. The device used for crushing is a soy milk maker. The first sintering is a temperature-rising stage I and a heat-preservation stage I that are carried out sequentially, and the specific conditions are shown in Table 1. The median particle size D of the nickel-cobalt-manganese precursor 50 and the median particle size D' of the single-crystalline cathode material intermediate 50 are shown in Table 1. (2) This single-crystalline cathode material intermediate was subjected to a second sintering to obtain a single-crystalline multi-component cathode material. The second sintering is carried out in an air atmosphere and is a temperature-rising stage II and a heat-preservation stage II that are carried out sequentially. The specific conditions are shown in Table 1, and the chemical formulas of each product during the reaction are shown in Table 2.

[0069] Example 2 In step (1), except that the heat-preservation temperature in the heat-preservation stage I of the first sintering and the median particle size D' of the single-crystalline cathode material intermediate 50 are specifically as shown in Table 1, the rest was carried out in the same manner as in the method of Example 1 to obtain a single-crystalline multi-component cathode material.

[0070] Example 3 In step (1), except that the heat preservation temperature in the heat preservation stage I of the first sintering and the central particle size D' of the single-crystal cathode material intermediate are as specifically shown in Table 1, the rest is the same as the method of Example 1 to obtain a single-crystal type multi-component cathode material. 50 In the remaining examples, except for the points shown in Table 1, the single-crystal type multi-component cathode materials were obtained in the same manner as the method of Example 1. In the remaining examples, except for the points shown in Table 1, the single-crystal type multi-component cathode materials were obtained in the same manner as the method of Example 1.

[0071] Comparative Example 1 In step (1), except that the first sintering is carried out in an air atmosphere, the rest is the same as the method of Example 1 to obtain a single-crystal type multi-component cathode material.

[0072] Comparative Example 2 In step (1), except that the first sintering is carried out in an oxygen gas atmosphere, the rest is the same as the method of Example 1 to obtain a single-crystal type multi-component cathode material.

[0073] Comparative Example 3 In step (1), except that the first sintering is carried out in an air atmosphere, the rest is the same as the method of Example 2 to obtain a single-crystal type multi-component cathode material.

[0074] Comparative Example 4 In step (1), except that the first sintering is carried out in an oxygen gas atmosphere, the rest is the same as the method of Example 3 to obtain a single-crystal type multi-component cathode material.

[0075] Comparative Example 5 In step (1), D' of the obtained single-crystal cathode material intermediate 50 is 3.64 μm, and except that |(D 50 - D' 50 ) / D 50 | = 13.3%, the rest is the same as the method of Example 3 to obtain a single-crystal type multi-component cathode material. The uniformity K of the single-crystal type multi-component cathode material 90 is shown in Table 3.

[0076] Comparative Example 6 In step (1), D' of the obtained single-crystal cathode material intermediate 50 is 4.49 μm, and |(D50 -D' 50 ) / D 50 Except that it was 6.9%, the rest was obtained in the same manner as in Example 3 to obtain a single crystal type multi-component cathode material. The uniformity K of the single crystal type multi-component cathode material 90 is shown in Table 3.

[0077]

Table 1-1

Table 1-2

[0078]

Table 2

[0079] Measurement Example 1 For each of the single crystal type multi-component cathode materials obtained in the examples and comparative examples, the aggregation rate B, particle size D 10 , particle size D 50 , particle size D 90 , uniformity K 90 , and roundness R were measured, and the results are shown in Table 3.

[0080]

Table 3

[0081] Measurement Example 2 For the single crystal type multi-component cathode materials obtained in the examples and comparative examples, the crystal grain size P 50 and the compression density, and the electrochemical properties were measured, and the results are shown in Table 4.

[0082]

Table 4

[0083] The present invention exemplarily shows scanning electron microscope (SEM) images of single-crystalline multi-component cathode materials obtained in Examples 1 to 3 and Comparative Examples 1 to 4, which are shown in FIGS. 1 to 7 respectively. As can be seen from the figures, compared with the single-crystalline multi-component cathode materials obtained in Examples 2 to 3 (FIGS. 2 and 3) and the single-crystalline multi-component cathode materials obtained in Comparative Examples 1 to 2 (FIGS. 4 to 5), the single-crystalline multi-component cathode material obtained in Example 1 of the present invention (FIG. 1) had more rounded and regular single-crystalline particles and better morphology.

[0084] In the single-crystalline multi-component cathode material obtained in Example 2 (FIG. 2) and the single-crystalline multi-component cathode material obtained in Comparative Example 2 (FIG. 5), the crystal grain size P of the single-crystalline particles 50 was 1.8 μm. It was obvious from the electron microscope image that a part of the particles maintained the precursor form, and there was adhesion between the particles. On the other hand, compared with the single-crystalline multi-component cathode material obtained in Comparative Example 2, in Example 2 of the present invention, in the primary sintering, the single-crystalline multi-component cathode material obtained by the sintering process combining oxygen gas and air had better particle independence and regularity. In the single-crystalline multi-component cathode material obtained in Example 3 (FIG. 3) and the single-crystalline multi-component cathode material obtained in Comparative Example 1 (FIG. 4), the crystal grain size P of the single-crystalline particles 50 was 2.6 μm. The crystal particles were large and had good independence, but the regularity was poor. However, compared with the single-crystalline multi-component cathode material obtained in Comparative Example 1, the single-crystalline particles of the single-crystalline multi-component cathode material obtained in Example 3 of the present invention were more rounded.

[0085] In the single-crystalline multi-component cathode material obtained in Example 1 and the single-crystalline multi-component cathode materials obtained in Comparative Examples 3 and 4, the crystal grain size P of the single-crystalline particles 50 was all 2.2 μm. However, compared with the single-crystalline multi-component cathode materials obtained in Comparative Examples 3 and 4, the single-crystalline particles of the single-crystalline multi-component cathode material obtained in Example 1 of the present invention had better roundness and degree of independence. Obviously from the above results, the single-crystalline multi-component cathode material according to the present invention has the characteristics that its morphology is rounder and more regular, the size of single-crystalline particles is uniform, there is little aggregation and adhesion, the compression density is high, the rate performance is good, and the cycle performance is excellent.

[0086] As can be seen from the comparison between Examples 1 to 3 and Comparative Examples 1 and 2, when the crystal grain size P of the single-crystalline particles 50 is 2.0 to 2.4 μm, the comprehensive properties are the most excellent, the compression density is the highest, the rate performance and the high-temperature cycle retention rate are the best, and the capacity is maintained at a high level. P 50 When it is <2.0 μm, although the compression density decreases and the rate performance and retention rate deteriorate, the crystal particles become smaller and the migration path of lithium ions inside the particles becomes shorter, so the capacity improves slightly. P 50 When it is >2.4 μm, the compression density also decreases, but the degree of decrease 50 is smaller than that when it is <2.0 μm.

[0087] From the comparison between Example 2 and Comparative Example 2, and Example 3 and Comparative Example 1, under the condition that an air atmosphere is used throughout the primary sintering, after the lithium source melts, crystals begin to grow from the outside on the surface of the particles, so growth is possible even at low temperatures. On the other hand, under the condition that an oxygen gas atmosphere is used throughout the primary sintering, there are many crystals and growth begins from the inside of the particles, so the temperature required for growth is high. As can be seen from the comparison of the compression density and electrochemical properties of the single-crystalline multi-component cathode material, in the single-crystalline multi-component cathode material obtained by the method combining sintering with oxygen gas in the heating stage of the primary sintering and sintering with air in the heat preservation stage according to the present invention, the single-crystalline particles have better compression density and better electrochemical properties.

[0088] As can be seen from the comparison between Example 1 and Comparative Examples 3 and 4, among single-crystalline layered cathode materials manufactured by various processes, even if the crystal grain sizes are the same, these properties are different. For primary sintering, in the case of single-crystalline layered cathode materials manufactured by a method combining sintering with oxygen gas in the heating stage and sintering with air in the heat preservation stage, the compression density and electrochemical properties were clearly superior to those of layered cathode materials manufactured using a single atmosphere.

[0089] Furthermore, the aggregation rate also affects the cycle characteristics of the material. As can be seen from the above table, the crystal grain size is directly related to the aggregation rate. The larger the crystal grain size, the smaller the aggregation rate, and the better the cycle characteristics. Also, the sintering atmosphere also has a certain influence on the aggregation rate and cycle characteristics. When the crystal grain sizes are the same, according to the sintering method combining oxygen gas and air in the primary sintering of the present invention, the manufactured single-crystalline particles have a significantly lower aggregation rate than particles manufactured by performing primary sintering in an oxygen gas or air atmosphere alone (the aggregation rate in the case of an oxygen gas atmosphere is lower than that in the case of an air atmosphere), and the cycle characteristics of the corresponding layered cathode material are as follows: combination of oxygen gas and air > oxygen gas > air. Also, from the roundness index, it was found that in the single-crystalline layered cathode material obtained by the method according to the present invention, the single-crystalline particles are rounder and more regular, and at the same crystal grain size, the roundness in the case of an oxygen gas atmosphere alone is superior to that in the case of an air atmosphere alone.

[0090] As can be seen from the comparison between Example 4 and Example 5, the method according to the present invention can also be applied to high-nickel products. As the nickel content increases and the cobalt content decreases, the roundness and compression density of the layered cathode material are maintained at a high level, and with regard to the electrochemical properties, the capacity is clearly improved, but the rate characteristics and cycle characteristics are correspondingly deteriorated. As can be seen from Example 1 and Comparative Examples 5 and 6, among layered cathode materials with different particle size distributions manufactured by the same sintering method, when the roundness satisfies the conditions within the range according to the present invention, K 90 is too large or too small, and K 90When the product of [a certain factor] and R is outside the scope of the present invention, although to a different degree, the compression density, capacity, and cycle life decreased.

[0091] The above has described in detail the preferred embodiments of the present invention, but the present invention is not limited thereto. Without departing from the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, including appropriately combining each technical feature. Such simple modifications and combinations should also be regarded as the content disclosed in the present invention and should all be included in the patent scope of the present invention.

Claims

1. A single-crystalline layered cathode material, wherein for the single-crystalline particles of the single-crystalline layered cathode material, the ratio of the length of the longest diagonal line to the length of the shortest diagonal line measured by SEM is defined as the roundness R, and R is 1 to 1.2, The D of the single crystal particles of the single crystal type multi-component positive electrode material １０ , D ５０ , and D ９０ satisfy K ９０ =(D ９０ -D １０ ) / D ５０ , and the product of K ９０ and R is 1.20 to 1.

40. A single crystal type multi-component positive electrode material characterized by this.

2. K ９０ The product of K and R is from 1.25 to 1.35, and / or K ９０ The single-crystalline multi-component cathode material according to claim 1, wherein K is 1.18 to 1.

25.

3. K ９０ The single-crystalline multi-component cathode material according to claim 2, wherein K is 1.20 to 1.

22.

4. The single-crystalline layered cathode material according to Claim 1, having a structure represented by Formula I. Li １＋ａ (Ni ｘ Co ｙ Mn ｚ G ｂ )M ｃ O ２－ｄ Formula I (In the formula, -0.05 ≤ a ≤ 0.3, 0 ≤ b ≤ 0.05, 0 ≤ c ≤ 0.05, 0.5 ≤ x < 1, 0 < y < 0.5, 0 < z < 0.5, d is a value that makes the number of positive charges and negative charges equal, G is one or more of Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, B, Mg, Co, F, and Y, and M is one or more of Sr, F, B, Al, Nb, Co, Mn, Mo, W, Si, Mg, Ti, and Zr.)

5. In the above formula, 0 ≤ a ≤ 0.2, 0.0001 ≤ b ≤ 0.005, 0.0001 ≤ c ≤ 0.005, 0.5 ≤ x ≤ 0.95, 0.01 ≤ y ≤ 0.4, 0.01 ≤ z ≤ 0.4, and / or, G is one or more of Ti, W, Zr, Sr, Si, Al, B, and F, and / or, M is one or more of Sr, F, B, Al, W, Si, and Ti, the single-crystalline layered cathode material according to Claim 4.

6. Taking the aggregation rate as B, B is 0 to 3.0%, the single-crystalline layered cathode material according to Claim 1.

7. B is 0.8 to 2.4%, the single-crystalline layered cathode material according to Claim 6.

8. The average value of the length of the longest diagonal line and the length of the shortest diagonal line of the single crystal particles of the single crystal type multi-component positive electrode material is the crystal grain size P ５０ where P ５０ is 1.5 to 3.0 μm. The single crystal type multi-component positive electrode material according to claim 1

9. P ５０ The single-crystalline multi-component cathode material according to claim 8, wherein P is 2.0 to 2.4 μm.

10. A method for manufacturing a single-crystalline layered cathode material, comprising: Step (1) of subjecting a mixture containing a nickel-cobalt-manganese precursor and a lithium source to a first sintering, and crushing the obtained product to obtain a single-crystalline cathode material intermediate; Step (2) of subjecting the single-crystalline cathode material intermediate to a second sintering to obtain a single-crystalline layered cathode material, wherein the first sintering includes a temperature-rising stage I and a heat-preserving stage I that are sequentially performed, the temperature-rising stage I is performed in an oxygen gas atmosphere, and the heat-preserving stage I is performed in an air atmosphere, wherein the temperature of the second sintering is lower than the temperature of the first sintering, the method for manufacturing a single-crystalline layered cathode material according to any one of Claims 1 to 9.

11. In step (1), the nickel-cobalt-manganese precursor is selected from oxides and / or hydroxides containing nickel, cobalt, and manganese, and / or, the lithium source is selected from lithium carbonate and / or lithium hydroxide, and / or, the mixed raw materials further contain an additive, and the additive is selected from compounds containing G, wherein G is one or more of Ti, W, V, Ta, Zr, La, Ce, Er, Sr, Si, Al, B, Mg, Co, F, and Y. The manufacturing method according to claim 10.

12. The additive is at least one of an oxide, hydroxide, carbonate, and fluoride containing G. The manufacturing method according to claim 11.

13. The additive is at least one of zirconia, strontium carbonate, strontium hydroxide, silica, alumina, aluminum hydroxide, tungsten trioxide, titanium oxide, aluminum fluoride, and boron oxide. The manufacturing method according to claim 12.

14. In step (1), the conditions of the temperature-rising stage I further include that the temperature-rising time is 2 to 10 h, and / or, the conditions of the heat-insulating stage I further include that the heat-insulating temperature is 600 to 1100 °C and the heat-insulating time is 6 to 12 h, and / or, The median particle size D of the nickel-cobalt-manganese precursor ５０ and the median particle size D' of the single-crystalline cathode material intermediate ５０ satisfy formula II, and the manufacturing method according to claim 10 | (D ５０ - D' ５０ ) / D ５０ | < 5% Formula II

15. In step (2), first, the single-crystal cathode material intermediate and the coating agent are mixed, and then the obtained mixture is subjected to the second sintering, the coating agent is selected from compounds containing M, wherein M is one or more of Sr, F, B, Al, Nb, Co, Mn, Mo, W, Si, Mg, Ti, and Zr. The manufacturing method according to claim 10.

16. The coating agent is at least one of an oxide, hydroxide, carbonate, and fluoride containing M. The manufacturing method according to claim 15.

17. The coating agent is at least one of strontium carbonate, strontium hydroxide, silica, alumina, aluminum hydroxide, tungsten trioxide, titanium oxide, aluminum fluoride, and boron oxide. The manufacturing method according to claim 16.

18. In step (2), the second sintering is carried out in an air atmosphere, and / or, the second sintering includes a temperature-rising stage II and a heat-insulating stage II that are sequentially carried out, and / or, the conditions of the temperature-rising stage II further include that the temperature-rising time is 2 to 10 h, and / or, The manufacturing method according to claim 10, wherein the conditions of the heat preservation stage II further include that the heat preservation temperature is 500 to 900 °C and the heat preservation time is 6 to 12 h.

19. When the change value of the crystal grain size of the single-crystalline multi-component cathode material is defined as ΔP (unit: μm), the change value of the temperature of the same sintering step is defined as ΔT (unit: °C), and the change value of the time of the same sintering step is defined as Δt (unit: h), these three satisfy ΔP = ωΔT + γΔt (where ω = 0.02 μm / °C, γ = 0.1 μm / h). The manufacturing method according to claim 10.

20. A lithium-ion battery comprising the single-crystalline multi-component cathode material according to any one of claims 1 to 9.

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