A ternary positive electrode material precursor, a ternary positive electrode material, a preparation method thereof and a lithium ion battery

Abstract

This invention belongs to the field of lithium-ion batteries and discloses a ternary cathode material precursor, comprising multiple secondary particles composed of primary particles. Each secondary particle is divided into three layers from the inside out: an inner layer, a middle layer, and an outer layer. The nickel content of the middle layer is higher than that of the inner and outer layers; the manganese content of the middle layer is lower than that of the inner and outer layers. This invention also discloses a method for preparing the ternary cathode material precursor, as well as the ternary cathode material and a lithium-ion battery. In the ternary precursor and cathode material provided by this invention, the nickel content within the particles exhibits a trend of first increasing and then decreasing from the center to the surface, while the manganese content exhibits a trend of first decreasing and then increasing from the center to the surface. This effectively improves the structural and thermal stability of the cathode material during cycling, thereby improving the capacity, lifespan, and safety performance of the lithium-ion battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery cathode materials, and particularly relates to a ternary cathode material, a precursor, a preparation method thereof, and a lithium-ion battery. Background Technology

[0002] High-nickel ternary cathode materials have become one of the most promising cathode materials for lithium-ion batteries due to their high specific energy and high operating voltage. However, problems such as surface phase transitions and side reactions with the electrolyte during cycling seriously affect electrochemical and safety performance, especially as the nickel content increases. To improve these issues, the structural stability of high-nickel ternary materials can be enhanced through structural design of the high-nickel ternary precursor, thereby improving their cycle stability and thermal stability.

[0003] Chinese patent application CN111018006A discloses a method for preparing a core-shell structured ternary cathode material. This method employs a continuous co-precipitation process. First, nickel-rich precursor particles are prepared in reactor 1. Then, these particles are injected into reactor 2 via a metering pump to continue crystallizing. Manganese-rich particles grow on the surface of the nickel-rich particles, forming core-shell structured precursor particles. These precursor particles are then mixed with lithium source material and calcined at high temperature to prepare the core-shell structured ternary cathode material (LiNi). x Co y Mn 1-x-yAlthough this method can prepare ternary cathode materials with high nickel content at the center and high manganese content on the surface, thereby improving the surface stability of the ternary material, the differences in composition and structure between the nickel-rich particles and the manganese-rich particles will cause the core and shell to shrink to varying degrees and gradually separate during cycling, thereby inhibiting the diffusion-migration process of ions / electrons between the core and shell, resulting in a sharp decline in the long-cycle performance of the material. Chinese Patent CN107579236A discloses a method for preparing a fully gradient high-nickel ternary precursor and a fully gradient high-nickel ternary cathode material. The method includes the following steps: preparing mixed solutions A, B, and C; pumping mixed solution A, an alkaline solution, and a complexing agent concurrently into a reactor; after a reaction time T1, continuously pumping mixed solution B into mixed solution A at a rate V1; and after a reaction time T2, continuously pumping mixed solution C into mixed solution B at a rate V2. This achieves continuous variation in the feed and composition of nickel, cobalt, and manganese salts, resulting in a fully gradient high-nickel ternary precursor. The lithium source compound and the fully gradient high-nickel ternary precursor are mixed in a molar ratio, and the resulting mixture is sintered in an oxygen atmosphere. Post-processing is then performed to obtain the fully gradient high-nickel ternary cathode material. While this method effectively solves the core-shell separation problem caused by the core-shell structure, it requires strict control of reaction time and feed rate, making the process complex and unsuitable for industrial production. In addition, the nickel ions in this full-gradient high-nickel ternary cathode material are mainly distributed in the center of the spherical particles, which greatly increases the lithium ion transport path and has a certain impact on the rate performance of the material. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a cathode material and its precursor with large discharge capacity, good structural stability and excellent electrochemical performance.

[0005] The further technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a ternary cathode material precursor, a ternary cathode material and its preparation method and a lithium-ion battery.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] A ternary cathode material precursor, wherein the ternary cathode material precursor is a nickel-cobalt-manganese hydroxide or oxide, and the ternary cathode material precursor includes a plurality of secondary particles composed of primary particles. In the secondary particles, the secondary particles are divided into three layers from the inside out, namely an inner layer, an intermediate layer, and an outer layer. The nickel content of the intermediate layer is higher than that of the inner and outer layers, and the manganese content of the intermediate layer is lower than that of the inner and outer layers.

[0008] The nickel and manganese contents in the ternary cathode material prepared from this precursor also show corresponding distribution trends. The nickel content increases and the manganese content decreases from the inner layer to the middle layer, which is conducive to storing nickel to improve the capacity of the cathode material. The nickel content decreases from the middle layer to the outer layer, and is closer to the surface, which is conducive to stabilizing the material structure. The increase in manganese content can reduce the surface activity of the material, reduce the redox reaction with the electrolyte, and avoid the generation of harmful interface products (such as abnormal thickening of the SEI film). In addition, manganese helps to stabilize the layered structure, which can reduce the volume expansion and structural collapse of the outer layer caused by lithium deintercalation during cycling. At the same time, it can further inhibit the dissolution of transition metal ions (such as nickel and cobalt), reduce material failure, and extend cycle life, thus obtaining a cathode material with better comprehensive performance.

[0009] Preferably, the ternary cathode material precursor is a nickel-cobalt-manganese hydroxide with the chemical formula Ni. x Co y Mn (1-x-y) (OH)₂, where 0.6 ≤ x < 1, 0 < y < 0.2, 0 < 1 - xy < 0.2. This invention is more suitable for ternary cathode material precursors with medium to high nickel content, simultaneously achieving capacity enhancement and structural stability.

[0010] In some embodiments, the average particle size D50 of the secondary particles is 4–15 μm. Secondary particles that are too large or too small are detrimental to the electrochemical performance.

[0011] In some embodiments, in the secondary particles, the nickel content gradually increases and the manganese content gradually decreases from the inner layer to the middle layer; from the middle layer to the outer layer, the nickel content gradually decreases and the manganese content gradually increases. The gradual change in nickel content makes the material composition difference between adjacent spaces inside the secondary particles smaller, making the secondary particle structure stable and less prone to cracking.

[0012] As part of the same inventive concept, this application also provides a method for preparing a ternary cathode material precursor, comprising the following steps:

[0013] Step 1: Prepare two nickel-containing solutions with different nickel contents, namely a high-nickel solution and a low-nickel solution, and divide each into two portions;

[0014] Step 2: One portion of the high-nickel solution is continuously added to one portion of the low-nickel solution, and at the same time, the resulting low-nickel solution containing the mixed solution is added to a continuously stirred reactor to undergo the first coprecipitation reaction;

[0015] Step 3: After the addition of liquid in Step 2 is completed, another portion of low-nickel solution is continuously pumped into another portion of high-nickel solution. At the same time, the high-nickel solution containing the mixed solution is added to the continuously stirred reactor in Step 2 to undergo the second coprecipitation reaction.

[0016] Step 4: The solution containing the precursor material obtained in Step 3 is aged, filtered, washed, and dried to obtain the ternary cathode material precursor.

[0017] In the above preparation method, preferably, the total molar concentration of metal ions in both the high-nickel solution and the low-nickel solution is 0.1–3.0 mol / L; more preferably, it is 1.5–2.5 mol / L. If the concentration of metal ions is too low, it will be detrimental to the subsequent precipitation process and the precipitation time will be longer, which will not be conducive to improving production efficiency; if the concentration of metal ions is too high, it will be detrimental to the complete dissolution of the metal salt.

[0018] In the high-nickel solution, the molar amount of nickel ions accounts for more than 80% of the total molar amount of all metals;

[0019] In the low-nickel solution, the molar amount of nickel ions accounts for 55% to 80% of the total molar amount of all metals.

[0020] In the above preparation method, preferably, in step two, the rate at which the high-nickel solution is continuously added to the low-nickel solution is half the rate at which the low-nickel solution containing the mixed solution is added to the continuously stirred reactor (80-120 mL / h).

[0021] In step three, the rate at which the low-nickel solution is continuously added to the high-nickel solution is half the rate at which the high-nickel solution containing the mixed solution is added to the continuously stirred reactor (80-120 mL / h).

[0022] In the above-described preparation method, preferably, during the first and second coprecipitation reactions, the ammonia concentration in the reaction system is adjusted to 0.1–5.0 mol / L using ammonia water; the pH value of the reaction system is adjusted to 10–12 using hydroxide solution; the stirring speed is controlled at 800–1200 r / min, the temperature at 40–60℃ (more preferably 40–50℃), and the reaction time at 12–50 h (more preferably 30–40 h); the reaction is carried out under a protective atmosphere; if the stirring speed is too slow, the primary particles are prone to agglomeration; if the stirring speed is too fast, the grown crystals are prone to breakage; the temperature range is more conducive to crystal growth; the reaction time is determined by the raw material content and the feeding rate.

[0023] In the above preparation method, preferably, the aging temperature is 40-60℃ and the time is 8-24h. The aging process can displace anions such as sulfate from the material and is beneficial to the uniformity of the particle surface. If the aging time is too short, it is difficult to ensure the ion exchange of anions, which will also affect the subsequent washing process. If the aging time is too long, it is not conducive to production application and the uniformity of the material surface. The aging temperature is consistent with the co-precipitation reaction temperature, which is conducive to the uniform dispersion of the material without agglomeration and ensures that the primary particles grow into secondary particles uniformly. The washing involves washing the filter material with deionized water and ethanol alternately ≥6 times. The drying temperature is 100℃ and the time is 12-24h. If the temperature is too low or the time is too short, the material is difficult to dry. If the temperature is too high or the time is too long, other side reactions will occur on the material surface, affecting the material performance. Furthermore, an excessively long cycle is not conducive to industrial production.

[0024] In the above preparation method, preferably, the feeding rate is controlled at 80-120 mL / h (more preferably 90-110 mL / h) when the solution is added to the reaction vessel. If the feeding rate is too fast, the pH range will be large, making it difficult for the precipitant to effectively precipitate metal ions, which is not conducive to controlling the formation and growth of crystal nuclei in the reaction process. If the feeding rate is too slow, the particles are prone to agglomeration, which is also not conducive to improving production efficiency.

[0025] More preferably, the protective atmosphere is a nitrogen atmosphere and / or an argon atmosphere.

[0026] This application also provides a ternary cathode material, wherein the ternary cathode material is lithium nickel cobalt manganese oxide, and the ternary cathode material includes a plurality of secondary particles composed of primary particles. In the secondary particles, the secondary particles are divided into three layers from the inside out, namely an inner layer, a middle layer and an outer layer. The nickel content of the middle layer is higher than that of the inner and outer layers; the manganese content of the middle layer is lower than that of the inner and outer layers.

[0027] Preferably, the ternary cathode material described above satisfies one or more of the following conditions:

[0028] (1) The chemical formula of the ternary cathode material is LiNi x Co y Mn (1-x-y) O2, where 0.6≤x<1, 0<y<0.2, 0<1-xy<0.2;

[0029] (2) The average particle size D50 of the secondary particles is 4 to 15 μm;

[0030] (3) In the secondary particles, the nickel content gradually increases and the manganese content gradually decreases from the inner layer to the middle layer; from the middle layer to the outer layer, the nickel content gradually decreases and the manganese content gradually increases.

[0031] As part of the same inventive concept, this application also provides a method for preparing the above-mentioned cathode material, including the following steps:

[0032] (1) First, prepare a ternary cathode material precursor;

[0033] (2) The lithium source and the ternary cathode material precursor are mixed to obtain a mixture;

[0034] (3) The mixture obtained is sintered in two stages under an oxidizing atmosphere, and then sintered at a two-stage temperature rise. After cooling to room temperature, a ternary cathode material with a structural structure is obtained.

[0035] In the above preparation method, preferably, the total molar ratio of nickel, cobalt and manganese in the ternary precursor material to the molar ratio of lithium in the lithium source is 1:1.02 to 1.10.

[0036] In the above preparation method, preferably, the lithium source is lithium hydroxide monohydrate and / or lithium carbonate, etc.

[0037] In the above preparation method, preferably, the oxidizing atmosphere is an air atmosphere and / or an oxygen atmosphere, etc.

[0038] In the above-described preparation method, preferably, the two-stage sintering refers to: first, heating to 350–550 °C (more preferably 400–500 °C) at a rate of 1–10 °C / min (more preferably 3–7 °C / min), sintering for 2–8 h (more preferably 3–6 h), and then heating to 550–1000 °C (more preferably 600–900 °C) at a rate of 1–10 °C / min (more preferably 3–7 °C / min), sintering for 8–20 h (more preferably 10–16 h). During the two-stage heating and sintering process, the temperature of the second stage sintering is higher than that of the first stage sintering. During the first stage sintering process, the main reaction is the decomposition of the precursor and the lithium source; during the second stage sintering process, the main reaction is the combination reaction of the precursor and the oxides from the decomposition of the lithium source in an oxygen atmosphere. If the sintering temperature is too high or the sintering time is too long, the material is prone to agglomeration or even clumping, making it difficult to release capacity during the charge and discharge process. If the calcination temperature is too low or the calcination time is too short, it is difficult to form the desired morphology, affecting the electrochemical performance. If the heating rate is too fast, it is difficult to ensure that the material reaction is sufficient, especially affecting the diffusion of lithium ions into the material structure. If the heating rate is too slow, it is not conducive to industrial production.

[0039] As part of the same inventive concept, this application also provides a lithium-ion battery comprising the aforementioned ternary cathode material.

[0040] The technical principle of this invention is as follows: In the preparation of nickel-cobalt-manganese ternary cathode material precursors by co-precipitation, a high-nickel solution is first added dropwise to a low-nickel solution, while a low-nickel solution containing the high-nickel solution is simultaneously added to a reaction vessel. During this process, the resulting reaction particles have a low nickel content at the center and a high nickel content at the surface. Then, the high-nickel and low-nickel solutions are exchanged, with the low-nickel solution added to the high-nickel solution, and simultaneously, a high-nickel solution containing the low-nickel solution is added to the reaction vessel. This allows the particles to continue growing on the surface, gradually decreasing the nickel content and gradually increasing the manganese content. The nickel-cobalt-manganese ternary cathode material precursor prepared by this method is a near-spherical particle. The nickel content inside the spherical particle shows a trend of first increasing and then decreasing from the center to the surface, while the manganese content shows a trend of first decreasing and then increasing from the center to the surface. This effectively stabilizes the structural and thermal stability of the cathode material during cycling and also helps to shorten the lithium-ion transport path, improving the rate performance of the material.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] (1) The nickel content in the ternary precursor and its cathode material provided by the present invention shows a trend of first increasing and then decreasing from the center to the surface, while the manganese content shows a trend of first decreasing and then increasing from the center to the surface. This can effectively improve the structural stability and thermal stability of the cathode material during cycling, thereby improving the capacity, service life and safety performance of lithium-ion batteries.

[0043] (2) The nickel content at the center and surface of the ternary precursor and its cathode material provided by the present invention is lower than that in the middle of the particles, which helps to shorten the lithium ion transport path and effectively improve the rate performance of the material.

[0044] (3) The ternary precursor and its cathode material provided by the present invention have regular morphology and uniform particle size distribution. The content of nickel, cobalt and manganese in the spherical particles of the precursor changes continuously. There is no obvious interface inside the material, which can effectively avoid the problem of core-shell separation caused by excessive changes in composition in the core-shell structure. The structure is stable.

[0045] (4) The process of the present invention is simple, the preparation process is easy to control, the raw material cost is low, and it is suitable for industrial production. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1This is a SEM image of the ternary precursor in Embodiment 1 of the present invention;

[0048] Figure 2 This is the XRD pattern of the ternary cathode material in Embodiment 1 of the present invention;

[0049] Figure 3 This is a SEM image of the ternary cathode material in Embodiment 1 of the present invention;

[0050] Figure 4 These are the charge-discharge cycle curves and charge-discharge coulomb curves of the battery assembled with the ternary cathode material in Embodiment 1 of the present invention.

[0051] Figure 5 This is a charge / discharge rate curve of the battery assembled with the ternary cathode material in Embodiment 1 of the present invention;

[0052] Figure 6 These are the charge-discharge cycle curves and charge-discharge coulomb curves of the battery assembled with the ternary cathode material in Embodiment 2 of the present invention. Detailed Implementation

[0053] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0054] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0055] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0056] In some embodiments, the ternary precursor is formed by the accumulation of primary particles, which then form secondary aggregates in a spherical shape with a particle size of approximately 4–15 μm; the chemical formula of the ternary precursor is Ni. x Co y Mn (1-x-y) (OH)2, where 0.6≤x<1, 0<y<0.2, 0<1-xy<0.2. In ternary precursors and cathode materials, the nickel content of the particles first increases and then decreases from the center to the surface. The increasing stage from the center is conducive to storing nickel to improve the capacity of the cathode material, while the decreasing stage is closer to the surface, which is conducive to stabilizing the material structure.

[0057] In some embodiments, the ternary precursor and cathode material precursor of the present invention have regular morphology and uniform particle size distribution. The content of nickel and manganese elements inside the spherical particles of the precursor varies continuously, and there is no obvious interface inside the material. This can effectively avoid the problem of core-shell separation caused by excessive changes in composition in the core-shell structure.

[0058] In some embodiments, the nickel content inside the ternary precursor and ternary cathode material particles exhibits a trend of first increasing and then decreasing from the center to the surface, while the manganese content exhibits a trend of first decreasing and then increasing from the center to the surface. This effectively improves the structural and thermal stability of the cathode material during cycling, thereby enhancing the lifespan and safety performance of the lithium-ion battery. Furthermore, unlike the fully gradient ternary precursor and cathode material where nickel is mainly distributed at the center of the spherical particles, the nickel content at the center and surface of the ternary precursor and cathode material of this invention is lower than that in the middle of the particles. This helps to shorten the lithium-ion transport path and effectively improves the rate performance of the material.

[0059] The preparation method of the precursor and ternary cathode material of this invention is beneficial to the capacity improvement of the cathode material during charge and discharge, the material structure is stable, and it exhibits excellent electrochemical performance.

[0060] Unless otherwise specified, the raw materials or chemical reagents used in the embodiments of this invention are obtained through conventional commercial channels.

[0061] Example 1:

[0062] This embodiment provides a Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor, LiNi 0.8 Co 0.1 Mn 0.1 O2 cathode materials and their preparation methods.

[0063] Ni in this embodiment 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor includes multiple secondary particles composed of primary particles. The secondary particles are divided into three layers from the inside out: an inner layer, a middle layer, and an outer layer. From the inner layer to the middle layer, the nickel content gradually increases and the manganese content gradually decreases. From the middle layer to the outer layer, the nickel content gradually decreases and the manganese content gradually increases.

[0064] The preparation method of the precursor in this embodiment includes the following steps:

[0065] (1) Weigh 3.6 mol nickel sulfate hexahydrate and 0.4 mol cobalt sulfate heptahydrate and dissolve them in deionized water to prepare 2 L of high nickel solution; weigh 2.8 mol nickel sulfate hexahydrate, 0.4 mol cobalt sulfate heptahydrate and 0.8 mol manganese sulfate pentahydrate and dissolve them in deionized water to prepare 2 L of low nickel solution, and divide each into two portions.

[0066] (2) The first high-nickel solution was pumped into the first low-nickel solution at a feeding rate of 40 mL / h. At the same time, the resulting low-nickel solution containing the mixed solution was pumped into a reactor containing 2 L of 2 mol / L ammonia solution at a feeding rate of 80 mL / h. After the first high-nickel solution and the first low-nickel solution containing the mixed solution were fed, the second low-nickel solution was pumped into the second high-nickel solution at a feeding rate of 40 mL / h. At the same time, the resulting high-nickel solution containing the mixed solution was pumped into the reactor at a feeding rate of 80 mL / h. During the entire reaction process, the ammonia concentration of the reaction system was adjusted to 2 mol / L with 25% ammonia solution. The pH value of the reaction system was adjusted to 11.45 with 5 mol / L sodium hydroxide precipitant solution. A high-purity nitrogen atmosphere was introduced, and the reaction was carried out at 1000 r / min and 50 °C with heating and stirring for 50 h. After the low-nickel solution and the high-nickel solution were fed, a solution containing the precursor material was obtained.

[0067] (3) The solution containing the precursor material obtained in step (2) is stirred and aged at 1000 r / min and 50℃ for 12 h, filtered, and the filter is washed with deionized water and ethanol respectively 6 times. It is then dried at 100℃ for 12 h to obtain the ternary precursor material.

[0068] like Figure 1 As shown, the ternary precursor Ni obtained in this embodiment 0.8 Co 0.1 Mn 0.1 (OH)2 is spherical, with uniform particle distribution, regular morphology, and a particle size of approximately 12 μm.

[0069] The preparation method of the cathode material is as follows:

[0070] The 1.0 g ternary precursor Ni obtained in this embodiment 0.8 Co 0.1 Mn 0.1(OH)2 (containing 8.2122 mmol Ni, 1.04 mmol Co, and 0.8973 mmol Mn) was mixed and ground with 0.44707 g (10.6573 mmol) of lithium hydroxide monohydrate. The mixture was then subjected to a two-stage heating and sintering process under an oxygen atmosphere: first, the temperature was increased to 480℃ at a rate of 5℃ / min and sintered for 5 h; then, the temperature was increased to 775℃ at a rate of 5℃ / min and sintered for 12 h. After cooling to room temperature, the ternary cathode material LiNi was obtained. 0.8 Co 0.1 Mn 0.1 O2.

[0071] like Figure 2 As shown, the ternary cathode material LiNi in this embodiment 0.8 Co 0.1 Mn 0.1 The characteristic peaks of O2 and LiNiO2 match those of the PDF standard card (PDF#85-1966), indicating that they have the same phase structure and no impurity phases are generated.

[0072] like Figure 3 As shown, the ternary cathode material LiNi in this embodiment 0.8 Co 0.1 Mn 0.1 O2 has complete sphericity, inherits the spherical shape of the precursor well, has uniform primary particle distribution and regular morphology on the surface, and secondary particles with a particle size of about 10μm.

[0073] The battery is manufactured as follows:

[0074] Battery Assembly: Weigh 0.08 g of the ternary cathode material obtained in this embodiment, add 0.01 g of acetylene black as a conductive agent and 0.01 g of PVDF polyvinylidene fluoride as a binder, and mix and grind with N-methylpyrrolidone as a solvent to form a cathode material; coat the obtained cathode material onto the surface of aluminum foil to form an electrode sheet; in a sealed glove box filled with argon gas, use the electrode sheet as the cathode, a lithium metal sheet as the anode, a microporous polypropylene membrane as the separator, and 1 mol / L LiPF6 / EC:DMC:DEC (volume ratio 1:1:1) as the electrolyte to assemble a CR2025 coin cell, and conduct charge and discharge performance tests at a charge and discharge voltage of 2.7–4.3 V and a current density of 0.1 C (1C = 200 mA / g).

[0075] Electrochemical performance is shown in Figure 4 , Figure 5 And Table 1. (As shown in Table 1) Figure 4As shown, the cathode material assembled battery using the ternary precursor material obtained in this embodiment exhibits the following characteristics at a current density: 227.1 mAh / g for initial charge, 194.6 mAh / g for initial discharge, and an initial charge-discharge coulombic efficiency of 85.68%; at a current density of 1 C, the initial charge specific capacity is 194.4 mAh / g, the initial discharge specific capacity is 176 mAh / g, and the initial charge-discharge coulombic efficiency is 90.58%. After 100 cycles, the discharge specific capacity remains as high as 160 mAh / g, with a capacity retention rate of 90.91%. Figure 5 As shown, the discharge specific capacity at a 10 C current density can reach over 146.7 mAh / g, indicating that this structure can effectively improve charge / discharge capacity and cycle stability.

[0076] Example 2:

[0077] This embodiment provides a Ni 0.83 Co 0.05 Mn 0.12 O2 precursor, LiNi 0.83 Co 0.05 Mn 0.12 O2 cathode materials and their preparation methods.

[0078] Ni in this embodiment 0.83 Co 0.05 Mn 0.12 The O2 precursor includes multiple secondary particles composed of primary particles. The secondary particles are divided into three layers from the inside out: an inner layer, a middle layer, and an outer layer. From the inner layer to the middle layer, the nickel content gradually increases and the manganese content gradually decreases. From the middle layer to the outer layer, the nickel content gradually decreases and the manganese content gradually increases.

[0079] The steps for preparing the precursor in this embodiment are as follows:

[0080] (1) Weigh 3.6 mol nickel sulfate hexahydrate, 0.2 mol cobalt sulfate heptahydrate, and 0.2 mol manganese sulfate pentahydrate and dissolve them in deionized water to prepare 2 L of high-nickel solution; weigh 3.04 mol nickel sulfate hexahydrate, 0.2 mol cobalt sulfate heptahydrate, and 0.76 mol manganese sulfate pentahydrate and dissolve them in deionized water to prepare 2 L of low-nickel solution, and divide each into two portions.

[0081] (2) The first high-nickel solution was pumped into the first low-nickel solution at a feeding rate of 50 mL / h. At the same time, the resulting low-nickel solution containing the mixed solution was pumped into a reactor containing 2 L of 2 mol / L ammonia solution at a feeding rate of 100 mL / h. After the first high-nickel solution and the first low-nickel solution containing the mixed solution were fed, the second low-nickel solution was pumped into the second high-nickel solution at a feeding rate of 50 mL / h. At the same time, the resulting high-nickel solution containing the mixed solution was pumped into the reactor at a feeding rate of 100 mL / h. Throughout the reaction process, the ammonia concentration of the reaction system was adjusted to 2 mol / L with 25% ammonia solution. The pH of the reaction system was adjusted to 11.4 with 5 mol / L sodium hydroxide precipitant solution. Under a high-purity nitrogen atmosphere, the system was heated and stirred at 1000 r / min and 50 °C for 40 h for co-precipitation. After the low-nickel solution and the high-nickel solution were fed, the precursor material solution was obtained.

[0082] (3) The solution containing the precursor material obtained in step (2) is stirred and aged at 1000 r / min and 50℃ for 12 h, filtered, and the filter is washed with deionized water and ethanol respectively 6 times. It is then dried at 100℃ for 12 h to obtain the ternary precursor material.

[0083] Upon testing, the ternary precursor Ni obtained in this embodiment... 0.83 Co 0.05 Mn 0.12 (OH)2 is spherical, with uniform particle distribution, regular morphology, and a particle size of approximately 10 μm.

[0084] The preparation method of this cathode material is as follows:

[0085] The 1.0g ternary precursor Ni obtained in this embodiment 0.83 Co 0.05 Mn 0.12 (OH)2 (containing 8.8767 mmol Ni, 0.5498 mmol Co, and 1.24504 mmol Mn) was mixed with 0.470053 g (11.2051 mmol) of lithium hydroxide monohydrate and ground. Then, under an oxygen atmosphere, a two-stage heating sintering process was performed (first, the temperature was increased to 450℃ at a rate of 5℃ / min and sintered for 4 h, then increased to 750℃ at a rate of 5℃ / min and sintered for 12 h). After cooling to room temperature, the ternary cathode material LiNi was obtained. 0.83 Co 0.05 Mn 0.12 O2.

[0086] Testing revealed that the ternary cathode material LiNi in this embodiment... 0.83 Co 0.05 Mn0.12 O2 has complete sphericity, inherits the spheroidal shape of the precursor well, and has a uniform distribution of primary particles on the surface with a regular morphology.

[0087] The battery is manufactured as follows:

[0088] Battery assembly: Same as Example 1. Electrochemical performance is shown below. Figure 6 See Table 1.

[0089] Example 3:

[0090] This embodiment provides a Ni 0.88 Co 0.05 Mn 0.07 O2 precursor, LiNi 0.88 Co 0.05 Mn 0.07 O2 cathode materials and their preparation methods.

[0091] Ni in this embodiment 0.88 Co 0.05 Mn 0.07 The O2 precursor includes multiple secondary particles composed of primary particles. The secondary particles are divided into three layers from the inside out: an inner layer, a middle layer, and an outer layer. From the inner layer to the middle layer, the nickel content gradually increases and the manganese content gradually decreases. From the middle layer to the outer layer, the nickel content gradually decreases and the manganese content gradually increases.

[0092] The steps for preparing the precursor in this embodiment are as follows:

[0093] (1) Weigh 3.6 mol nickel sulfate hexahydrate, 0.2 mol cobalt sulfate heptahydrate, and 0.2 mol manganese sulfate pentahydrate and dissolve them in deionized water to prepare 2 L of high-nickel solution; weigh 3.44 mol nickel sulfate hexahydrate, 0.2 mol cobalt sulfate heptahydrate, and 0.36 mol manganese sulfate pentahydrate and dissolve them in deionized water to prepare 2 L of low-nickel solution, and divide each into two portions.

[0094] (2) The first high-nickel solution was pumped into the first low-nickel solution at a feeding rate of 40 mL / h, and the low-nickel solution containing the mixed solution was pumped into the reactor containing 2L of 2mol / L ammonia solution at a feeding rate of 80 mL / h. After the first high-nickel solution and the first low-nickel solution containing the mixed solution were fed, the second low-nickel solution was pumped into the second high-nickel solution at a feeding rate of 40 mL / h, and the high-nickel solution containing the mixed solution was pumped into the reactor at a feeding rate of 80 mL / h. During the entire reaction process, the ammonia concentration of the reaction system was adjusted to 2 mol / L with 25% ammonia solution, and the pH value of the reaction system was adjusted to 11.40 with 5 mol / L sodium hydroxide precipitant solution. Under a high-purity nitrogen atmosphere, the system was heated and stirred at 1000 r / min and 50℃ for 40 h for co-precipitation. After the low-nickel solution and the high-nickel solution were fed, the precursor material solution was obtained.

[0095] (3) The solution containing the precursor material obtained in step (2) is stirred and aged at 1100 r / min and 50℃ for 12 h, filtered, and washed with deionized water and ethanol respectively 6 times. The solution is then dried at 80℃ for 12 h to obtain the ternary precursor material.

[0096] The ternary precursor Ni obtained in this embodiment 0.88 Co 0.05 Mn 0.07 (OH)2 is spherical, with uniform particle distribution, regular morphology, and a particle size of approximately 10 μm.

[0097] The preparation method of the cathode material is as follows:

[0098] The 1.0g ternary precursor Ni obtained in this embodiment 0.88 Co 0.05 Mn 0.07 (OH)2 (containing 9.3367 mmol Ni, 0.5362 mmol Co, and 0.749936 mmol Mn) was mixed with 0.46791 g (11.154 mmol) of lithium hydroxide monohydrate and ground. Then, under an oxygen atmosphere, a two-stage heating sintering process was performed (first, the temperature was increased to 450 °C at a rate of 5 °C / min and sintered for 4 h; then, the temperature was increased to 725 °C at a rate of 5 °C / min and sintered for 12 h). After cooling to room temperature, the ternary cathode material LiNi was obtained. 0.88 Co 0.05 Mn 0.07 O2.

[0099] Testing revealed that the ternary cathode material LiNi in this embodiment... 0.88 Co 0.05 Mn 0.07The characteristic peaks of O2 and LiNiO2 match those of the PDF standard card (PDF#85-1966), indicating that they have the same phase structure and no impurity phases are generated.

[0100] Testing revealed that the ternary cathode material LiNi in this embodiment... 0.88 Co 0.05 Mn 0.07 O2 has complete sphericity, inherits the spherical shape of the precursor well, has uniform primary particle distribution and regular morphology on the surface, and secondary particles with a particle size of about 10μm.

[0101] The battery is manufactured as follows:

[0102] Battery assembly: Same as in Example 1, electrochemical performance is shown in Table 1.

[0103] Comparative Example 1:

[0104] This comparative example provides a LiNi 0.8 Co 0.1 Mn 0.1 O2 precursor, cathode material and its preparation method.

[0105] The preparation method of this precursor is as follows:

[0106] (1) Weigh 6.4 mol nickel sulfate hexahydrate, 0.8 mol cobalt sulfate heptahydrate and 0.8 mol manganese sulfate pentahydrate and dissolve them in deionized water to prepare a 4 L mixed solution.

[0107] (2) The above solution was pumped into a reactor containing 2 L of 2 mol / L ammonia solution at a feeding rate of 80 mL / h. During the entire reaction process, the ammonia concentration of the reaction system was adjusted to 2 mol / L with 25% ammonia solution. The pH of the reaction system was adjusted to 11.45 with 4 L of 5 mol / L sodium hydroxide precipitant solution. High-purity nitrogen gas was introduced, and the mixture was heated and stirred at 1000 r / min and 50 °C for 50 h for co-precipitation. After the feeding was completed, a solution containing the precursor material was obtained.

[0108] (3) The solution containing the precursor material obtained in step (2) is stirred and aged at 1000 r / min and 50℃ for 12 h, filtered, and the filter is washed with deionized water and ethanol respectively 6 times. It is then dried at 100℃ for 12 h to obtain the ternary precursor material.

[0109] The 1.0 g ternary precursor Ni obtained in this comparative example 0.8 Co 0.1 Mn 0.1(OH)₂ was mixed and ground with 0.4633 g (11.0457 mmol) of lithium hydroxide monohydrate, and then subjected to a two-stage heating and sintering process under an oxygen atmosphere: first, the temperature was increased to 480 °C at a rate of 5 °C / min and sintered for 5 h; then, the temperature was increased to 775 °C at a rate of 5 °C / min and sintered for 12 h. After cooling to room temperature, the ternary cathode material LiNi was obtained. 0.8 Co 0.1 Mn 0.1 O2.

[0110] The battery is manufactured as follows:

[0111] Battery assembly: Same as in Example 1, electrochemical performance is shown in Table 1.

[0112] Comparative Example 2:

[0113] This comparative example provides a LiNi 0.8 Co 0.1 Mn 0.1 O2 precursor, cathode material and its preparation method.

[0114] The preparation method of this precursor is as follows:

[0115] (1) Weigh 3.6 mol nickel sulfate hexahydrate and 0.4 mol cobalt sulfate heptahydrate and dissolve them in deionized water to prepare 2 L of high nickel solution; weigh 2.8 mol nickel sulfate hexahydrate, 0.4 mol cobalt sulfate heptahydrate and 0.8 mol manganese sulfate pentahydrate and dissolve them in deionized water to prepare 2 L of low nickel solution.

[0116] (2) The high-nickel solution was pumped into the low-nickel solution at a feeding rate of 40 mL / h. At the same time, the resulting low-nickel solution containing the mixed solution was pumped into a reactor containing 2 L of 2 mol / L ammonia solution at a feeding rate of 80 mL / h. Throughout the reaction process, the ammonia concentration of the reaction system was adjusted to 2 mol / L with 25% ammonia solution. The pH of the reaction system was adjusted to 11.45 with 5 mol / L sodium hydroxide precipitant solution. Under a high-purity nitrogen atmosphere, the mixture was heated and stirred at 1000 r / min and 50 °C for 50 h for co-precipitation. After the low-nickel and high-nickel solutions were fed, a solution containing the precursor material was obtained.

[0117] (3) The solution containing the precursor material obtained in step (2) is stirred and aged at 1000 r / min and 50℃ for 12 h, filtered, and the filter is washed with deionized water and ethanol respectively 6 times. It is then dried at 100℃ for 12 h to obtain the ternary precursor material.

[0118] The 1.0 g ternary precursor Ni obtained in this comparative example 0.8 Co0.1 Mn 0.1 (OH)₂ was mixed and ground with 0.4546 g (10.836 mmol) of lithium hydroxide monohydrate, and then subjected to a two-stage heating and sintering process under an oxygen atmosphere: first, the temperature was increased to 480℃ at a rate of 5℃ / min and sintered for 5 h; then, the temperature was increased to 775℃ at a rate of 5℃ / min and sintered for 12 h. After cooling to room temperature, the ternary cathode material LiNi was obtained. 0.8 Co 0.1 Mn 0.1 O2.

[0119] The battery is manufactured as follows:

[0120] Battery assembly: Same as in Example 1, electrochemical performance is shown in Table 1.

[0121] Table 1: Electrochemical performance of each example and comparative example

[0122]

[0123] This invention proposes a nickel content distribution that initially increases and then decreases. This is beneficial for ensuring that active nickel participates in the reaction to provide capacity, while maintaining the structural stability of the material and improving capacity retention. By comparing the electrochemical performance data of nickel content distribution that initially increases and then decreases (Example 1), remains unchanged (Comparative Example 1), and continuously decreases (Comparative Example 2) under the same nickel content conditions, the examples of this application show advantages in initial charge-discharge specific capacity under both 0.1C and 1C conditions. This is because, under the conditions of the comparative example, the nickel content on the outer side of the particles is higher than that of the samples prepared under the conditions of this invention. However, the samples of this invention show a significant advantage during cycling, especially after 100 cycles, the discharge capacity is significantly improved compared to the comparative example. Therefore, this invention can effectively improve the structural stability of high-nickel materials, and the prepared cathode material has a high capacity retention rate.

Claims

1. A ternary cathode material precursor, characterized in that, The ternary cathode material precursor is a nickel-cobalt-manganese hydroxide or oxide. The ternary cathode material precursor includes multiple secondary particles composed of primary particles. The secondary particles include three layers from the inside out: an inner layer, a middle layer, and an outer layer. The nickel content of the middle layer is higher than that of the inner and outer layers. The manganese content of the middle layer is lower than that of the inner and outer layers. The ternary cathode material precursor is a nickel-cobalt-manganese hydroxide with the chemical formula Ni. x Co y Mn (1-x-y) (OH)₂, wherein 0.6 ≤ x < 1, 0 < y < 0.2, 0 < 1 - xy < 0.2; its preparation method includes the following steps: Step 1: Prepare two nickel-containing solutions with different nickel contents, namely a high-nickel solution and a low-nickel solution, and divide each into two portions; the total molar concentration of metal ions in both the high-nickel and low-nickel solutions is 0.1–3.0 mol / L; in the high-nickel solution, the molar amount of nickel ions accounts for more than 80% of the total molar amount of all metals; in the low-nickel solution, the molar amount of nickel ions accounts for 55%–80% of the total molar amount of all metals. Step 2: One portion of the high-nickel solution is continuously added to one portion of the low-nickel solution, and at the same time, the resulting low-nickel solution containing the mixed solution is added to a continuously stirred reactor to undergo the first coprecipitation reaction; Step 3: After the addition of liquid in Step 2 is completed, another portion of low-nickel solution is continuously pumped into another portion of high-nickel solution. At the same time, the high-nickel solution containing the mixed solution is added to the continuously stirred reactor in Step 2 to undergo the second coprecipitation reaction. Step 4: The solution containing the precursor material obtained in Step 3 is aged, filtered, washed, and dried to obtain the ternary cathode material precursor.

2. The ternary cathode material precursor according to claim 1, characterized in that, The average particle size D50 of the secondary particles is 4–15 μm.

3. The ternary cathode material precursor according to claim 1, characterized in that, In step two, the rate at which the high-nickel solution is continuously added to the low-nickel solution is half the rate at which the low-nickel solution containing the mixed solution is added to the continuously stirred reactor. In step three, the rate at which the low-nickel solution is continuously added to the high-nickel solution is half the rate at which the high-nickel solution containing the mixed solution is added to the continuously stirred reactor.

4. The ternary cathode material precursor according to claim 1, characterized in that, During the first and second coprecipitation reactions, the ammonia concentration in the reaction system is adjusted to 0.1-5.0 mol / L using ammonia water; the pH value of the reaction system is adjusted to 10-12 using hydroxide solution; the stirring speed is controlled at 800-1200 r / min, the temperature at 40-60℃, and the reaction time at 12-50 h; the reaction is carried out under a protective atmosphere. The aging temperature is 40-60℃ and the time is 8-24h; the washing is to wash the filter material with deionized water and ethanol respectively; the drying temperature is 100℃ and the time is 12-24h.

5. A ternary cathode material, characterized in that, The ternary cathode material is prepared by mixing the ternary cathode material precursor as described in claim 1 or 2 with a lithium source and then sintering it in two stages at elevated temperatures. The ternary cathode material is lithium nickel cobalt manganese oxide. The ternary cathode material includes multiple secondary particles composed of primary particles. In the secondary particles, the secondary particles are divided into three layers from the inside out: an inner layer, a middle layer, and an outer layer. The nickel content of the middle layer is higher than that of the inner and outer layers. The manganese content of the middle layer is lower than that of the inner and outer layers.

6. The ternary cathode material according to claim 5, characterized in that, The ternary cathode material satisfies one or more of the following conditions: (1) The chemical formula of the ternary cathode material is LiNi x Co y Mn (1-x-y) O2, where 0.6≤x<1, 0<y<0.2, 0<1-xy<0.2; (2) The average particle size D50 of the secondary particles is 4 to 15 μm; (3) In the secondary particles, the nickel content gradually increases and the manganese content gradually decreases from the inner layer to the middle layer; from the middle layer to the outer layer, the nickel content gradually decreases and the manganese content gradually increases.

7. A lithium-ion battery, characterized in that, Includes the ternary cathode material as described in claim 5 or 6.

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