A lithium-doped ternary positive electrode material precursor, a preparation method thereof, and a ternary positive electrode material

Abstract

The application discloses a lithium-doped ternary positive electrode material precursor, wherein the lithium inclusion amount of the ternary positive electrode material precursor is 20-100 ppm. The lithium-doped ternary positive electrode material precursor prepared by the application has a primary particle thickness of 200-300 nm, lithium is pre-included in the precursor particle, the lithium inclusion amount is 20-100 ppm, Li-induced channels are formed in the particle structure, the difficulty of lithium infiltration during sintering is reduced, the amount of lithium infiltration is increased, the capacity is effectively improved, the morphology structure does not change, and the cycle performance can still be maintained, so that the cycle performance of the battery is maintained and the capacity is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion battery ternary cathode material, and particularly to a lithium-doped ternary cathode material precursor and a preparation method thereof. BACKGROUND

[0002] At present, lithium ion batteries occupy a large market share in the field of portable electronic devices due to the advantages of high specific capacity, long cycle life, low self-discharge rate, no memory effect, environmental friendliness and the like, and are recognized as the most potential power battery for electric vehicles. Currently, the preparation of conventional ternary cathode materials is first prepared by co-precipitation to prepare a ternary cathode material precursor, and then prepared by high-temperature sintering to prepare a ternary cathode material. The morphology, particle size, particle size distribution, specific surface area, impurity content, tap density and other product indexes of the ternary cathode material precursor to a great extent determine the performance of the cathode material product. The production of the ternary cathode material precursor mainly adopts a hydroxide co-precipitation process, which is to dissolve raw materials in deionized water, prepare a salt solution according to a certain molar ratio, and then add NaOH as a precipitant and ammonia as a complexing agent to produce a high-density spherical hydroxide precursor. For example, a salt solution prepared by mixing nickel sulfate, cobalt sulfate and manganese sulfate / aluminum sulfate in a certain proportion is added into a reaction kettle together with lye and a complexing agent under suitable reaction conditions to co-precipitate, and then the desired product is obtained after washing, drying and sieving. Among them, the co-precipitation is the key stage of controlling the morphology of the precursor.

[0003] In the co-precipitation process of the ternary cathode material precursor, the metal salt solution is first co-precipitated to form ternary cathode material precursor primary particles, and the primary particles agglomerate to continue co-precipitation to form ternary cathode material precursor secondary particles. In view of the long cycle requirement of lithium ion batteries, the primary particles of the precursor material should be relatively thick, with a diameter of about 200-300 nm. However, thick and dense primary particles will lead to difficulties in lithium mixing and penetration, affecting the sintering of the positive electrode, and although the cycle performance of the material is improved, the capacity is low. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a lithium-doped ternary cathode material precursor and a preparation method thereof, which solves the problem of capacity reduction due to the over-thickness of the primary particles, although the cycle performance of the ternary cathode material is improved.

[0005] The technical solution adopted by the present application to solve the technical problem is: a lithium-doped ternary cathode material precursor, wherein the occluded amount of lithium in the ternary cathode material precursor is 20-100 ppm. The occluded amount of lithium refers to the amount of lithium wrapped in the ternary cathode material precursor. Less than 20 ppm cannot form an induced channel, which is not helpful for lithium penetration and cannot improve the capacity. More than 100 ppm will damage the original structure of the precursor, reducing its electrical performance.

[0006] Further, the ternary positive electrode material precursor has a chemical formula of Ni x Co y X z (OH)2, wherein X is Mn or Al, 0

[0007] Further, the primary particles of the ternary positive electrode material precursor are nanosheets, and the thickness of the nanosheets is 200-300 nm.

[0008] The preparation method of the lithium-doped ternary positive electrode material precursor includes the following steps:

[0009] S1: preparing a raw material metal salt solution, a lye, a complexing agent solution, and a lithium source solution, and adding the raw material metal salt solution, the lye, ammonia, and the lithium source solution into a reaction kettle for co-precipitation reaction, and continuously supplying inert protective gas to the reaction kettle during the reaction; the metal salt solution is an aqueous solution containing nickel salt, cobalt salt, manganese salt, or aluminum salt;

[0010] S2: stopping feeding when the particle size grows to a target particle size, obtaining a solution containing a precursor material, and then aging, washing, drying, screening, and removing iron to obtain the lithium-doped ternary positive electrode material precursor.

[0011] The pH value of the reaction system is controlled to be 10.0-12.5, the ammonia value is controlled to be 2-20 g / L, the temperature is controlled to be 40-80℃, and the stirring speed is controlled to be 100-1000 rpm.

[0012] Further, when preparing the nickel-cobalt-manganese ternary precursor, the metal salt solution is an aqueous solution containing nickel salt, cobalt salt, and manganese salt, and the total concentration of metal ions in the metal salt solution is 1-2.5 mol / L; when preparing the nickel-cobalt-aluminum ternary precursor, the metal salt solution is a mixed salt solution prepared from nickel salt and cobalt salt and an aluminum salt solution, the total concentration of nickel ions and cobalt ions in the mixed salt solution is 1-2.5 mol / L, and the concentration of aluminum ions in the aluminum salt solution is 0.05-0.3 mol / L; the nickel salt, the cobalt salt, the manganese salt, and the aluminum salt are at least one of sulfate, nitrate, and halide; when preparing the nickel-cobalt-manganese ternary precursor, the molar ratio of nickel, cobalt, and manganese in the metal salt solution is 5-9:1-3:1-3, and when preparing the nickel-cobalt-aluminum ternary precursor, the molar ratio of nickel, cobalt, and aluminum in the metal salt solution is 5-9:1-3:1-3.

[0013] Further, the lithium source solution is a lithium hydroxide solution, and the concentration of the lithium source solution is 0.5-2 mol / L.

[0014] Furthermore, the molar ratio of lithium source solution to metal salt solution introduced into the reactor per unit time should be 0.1 to 2:1. That is, the molar ratio of lithium hydroxide introduced into the reactor per unit time to the total metal ions in the metal salt solution is 0.1 to 2:1.

[0015] Furthermore, the precipitant solution is a sodium hydroxide solution with a mass concentration of 20% to 40%, and the complexing agent solution is an ammonia solution with a mass concentration of 20% to 40%.

[0016] Furthermore, the particle size mentioned in step S2 is the particle size distribution D50 value, and the target particle size is 4 to 10 μm.

[0017] A ternary cathode material, wherein the ternary cathode material is prepared from the above-mentioned lithium-doped ternary cathode material precursor.

[0018] The beneficial effects of this invention are as follows: The thickness of the primary particles of the lithium-doped ternary cathode material precursor prepared by this invention is 200-300 nm, allowing lithium to be pre-encapsulated inside the precursor particles. The lithium encapsulation amount should be 20-100 ppm, which forms Li-induced channels in the particle structure, reduces the difficulty of lithium infiltration during sintering, increases the amount of lithium infiltration, effectively improves the capacity, and does not change the morphology and structure, so the cycle performance can still be maintained. Therefore, it not only maintains the battery cycle performance but also improves the capacity. Detailed Implementation

[0019] The present invention will be further described below with reference to embodiments.

[0020] Example 1:

[0021] A method for preparing a lithium-doped ternary cathode material precursor includes the following steps:

[0022] (1) Prepare materials: Mix nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of 6:1:3, add pure water and stir to dissolve, and prepare a metal salt solution with a total concentration of 2.2 mol / L. At the same time, prepare a sodium hydroxide solution with a mass concentration of 25%, an ammonia solution with a mass concentration of 20%, and a lithium hydroxide solution with a mass concentration of 1.0 mol / L.

[0023] (2) The above metal salt solution was added to the reactor at a flow rate of 1 L / h. Lithium hydroxide solution was introduced and the ratio of the molar ratio of lithium hydroxide to nickel cobalt manganese metal salt (the molar ratio here refers to the total molar value of nickel cobalt manganese ions in the metal salt solution) was set to 0.7 per unit time. Sodium hydroxide solution and ammonia were added at the same time to maintain the pH of the system at 12.5 and the ammonia concentration at 12 g / L. The reactor temperature was controlled at 60°C. The co-precipitation reaction was carried out under the protection of nitrogen gas with a stirring speed of 650 rpm. When the particle D50 value in the reactor grew to 6 μm, the feeding was stopped.

[0024] (3) The material is aged for 10 hours. After aging, it is filtered, washed, dried, sieved and demagnetized to obtain lithium-doped ternary cathode material precursor.

[0025] The lithium content of the obtained lithium-doped ternary cathode material precursor was determined by ICP analysis to be 35 ppm, and the particle diameter was measured to be 240 nm by scanning electron microscopy.

[0026] Example 2:

[0027] A method for preparing a lithium-doped ternary cathode material precursor includes the following steps:

[0028] (1) Prepare materials: Mix nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of 6:1:3, add pure water and stir to dissolve, and prepare a metal salt solution with a total concentration of 2.2 mol / L. At the same time, prepare a sodium hydroxide solution with a mass concentration of 25%, an ammonia solution with a mass concentration of 20%, and a lithium hydroxide solution with a mass concentration of 1.0 mol / L.

[0029] (2) The above metal salt solution was added to the reactor at a flow rate of 1 L / h. Lithium hydroxide solution was introduced and the ratio of lithium hydroxide to nickel cobalt manganese metal salt molars (where molars are the total molar values ​​of nickel cobalt manganese ions in the metal salt solution) was set to 1.8 per unit time. Sodium hydroxide solution and ammonia were added at the same time to maintain the pH of the system at 12.5 and the ammonia concentration at 12 g / L. The reactor temperature was controlled at 60°C. Co-precipitation reaction was carried out under the protection of nitrogen gas with a stirring speed of 650 rpm. When the particle D50 value in the reactor grew to 6 μm, the feeding was stopped.

[0030] (3) The material is aged for 10 hours. After aging, it is filtered, washed, dried, sieved and demagnetized to obtain lithium-doped ternary cathode material precursor.

[0031] The lithium content of the obtained lithium-doped ternary cathode material precursor was determined by ICP analysis to be 95 ppm, and the particle diameter was measured to be 255 nm by scanning electron microscopy.

[0032] Example 3:

[0033] A method for preparing a lithium-doped ternary cathode material precursor includes the following steps:

[0034] (1) Prepare materials: Mix nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of 6:1:3, add pure water and stir to dissolve, and prepare a metal salt solution with a total concentration of 2.2 mol / L. At the same time, prepare a sodium hydroxide solution with a mass concentration of 25%, an ammonia solution with a mass concentration of 20%, and a lithium hydroxide solution with a mass concentration of 1.0 mol / L.

[0035] (2) The above metal salt solution was added to the reactor at a flow rate of 1 L / h. Lithium hydroxide solution was introduced and the ratio of lithium hydroxide to nickel cobalt manganese metal salt molars (where molars are the total molar values ​​of nickel cobalt manganese ions in the metal salt solution) was set to 1.2 per unit time. Sodium hydroxide solution and ammonia were added at the same time to maintain the pH of the system at 12.5 and the ammonia concentration at 12 g / L. The reactor temperature was controlled at 60°C. Co-precipitation reaction was carried out under the protection of nitrogen gas with a stirring speed of 650 rpm. When the particle D50 value in the reactor grew to 6 μm, the feeding was stopped.

[0036] (3) The material is aged for 10 hours. After aging, it is filtered, washed, dried, sieved and demagnetized to obtain lithium-doped ternary cathode material precursor.

[0037] The lithium content of the obtained lithium-doped ternary cathode material precursor was determined by ICP analysis to be 60 ppm, and the particle diameter was measured to be 267 nm by scanning electron microscopy.

[0038] Comparative Example 1:

[0039] A method for preparing a lithium-doped ternary cathode material precursor includes the following steps:

[0040] (1) Prepare materials: Mix nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of 6:1:3, add pure water and stir to dissolve, and prepare a metal salt solution with a total concentration of 2.2 mol / L. At the same time, prepare a sodium hydroxide solution with a mass concentration of 25% and an ammonia solution with a mass concentration of 20%.

[0041] (2) The above metal salt solution was added to the reactor at a flow rate of 1L / h. Sodium hydroxide solution and ammonia were added at the same time to maintain the pH of the system at 12.5 and the ammonia concentration at 12g / L. The reactor temperature was controlled at 60℃. The co-precipitation reaction was carried out under the protection of nitrogen gas with a stirring speed of 650rpm. When the D50 value of the particles in the reactor grew to 6μm, the feeding was stopped.

[0042] (3) The material is aged for 10 hours. After aging, it is filtered, washed, dried, sieved and demagnetized to obtain lithium-doped ternary cathode material precursor.

[0043] The lithium content of the obtained lithium-doped ternary cathode material precursor was 0 by ICP detection, and the particle diameter was 232 nm by scanning electron microscopy.

[0044] Comparative Example 2:

[0045] A method for preparing a lithium-doped ternary cathode material precursor includes the following steps:

[0046] (1) Prepare materials: Mix nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of 6:1:3, add pure water and stir to dissolve, and prepare a metal salt solution with a total concentration of 2.2 mol / L. At the same time, prepare a sodium hydroxide solution with a mass concentration of 25%, an ammonia solution with a mass concentration of 20%, and a lithium hydroxide solution with a mass concentration of 1.0 mol / L.

[0047] (2) The above metal salt solution was added to the reactor at a flow rate of 1 L / h. Lithium hydroxide solution was introduced and the ratio of the molar ratio of lithium hydroxide to nickel cobalt manganese metal salt (the molar ratio here refers to the total molar value of nickel cobalt manganese ions in the metal salt solution) was set to 0.05 per unit time. Sodium hydroxide solution and ammonia were added at the same time to maintain the pH of the system at 12.5 and the ammonia concentration at 12 g / L. The reactor temperature was controlled at 60°C. The co-precipitation reaction was carried out under the protection of nitrogen gas with a stirring speed of 650 rpm. When the particle D50 value in the reactor grew to 6 μm, the feeding was stopped.

[0048] (3) The material is aged for 10 hours. After aging, it is filtered, washed, dried, sieved and demagnetized to obtain lithium-doped ternary cathode material precursor.

[0049] The lithium content of the obtained lithium-doped ternary cathode material precursor was determined by ICP analysis to be 7 ppm, and the particle diameter was measured to be 259 nm by scanning electron microscopy.

[0050] Comparative Example 3:

[0051] A method for preparing a lithium-doped ternary cathode material precursor includes the following steps:

[0052] (1) Prepare materials: Mix nickel sulfate, cobalt sulfate and manganese sulfate in a molar ratio of 6:1:3, add pure water and stir to dissolve, and prepare a metal salt solution with a total concentration of 2.2 mol / L. At the same time, prepare a sodium hydroxide solution with a mass concentration of 25%, an ammonia solution with a mass concentration of 20%, and a lithium hydroxide solution with a mass concentration of 1.0 mol / L.

[0053] (2) Add the above metal salt solution to the reactor at a flow rate of 1L / h, and introduce lithium hydroxide solution. Set the ratio of lithium hydroxide to nickel cobalt manganese metal salt molars (where molars are the total molar values ​​of nickel cobalt manganese ions in the metal salt solution) to 2.5 per unit time. At the same time, add sodium hydroxide solution and ammonia water to maintain the pH of the system at 12.5 and the ammonia concentration at 12g / L. Control the reactor temperature at 60℃ and carry out the co-precipitation reaction under the protection of nitrogen gas with a stirring speed of 650rpm. Stop feeding when the particle D50 value in the reactor grows to 6μm.

[0054] (3) The material is aged for 10 hours. After aging, it is filtered, washed, dried, sieved and demagnetized to obtain lithium-doped ternary cathode material precursor.

[0055] The lithium content of the obtained lithium-doped ternary cathode material precursor was determined by ICP analysis to be 120 ppm, and the particle diameter was measured to be 249 nm by scanning electron microscopy.

[0056] Six ternary cathode material precursors from Examples 1-3 and Comparative Examples 1-3 were mixed with lithium and sintered at 800°C. After crushing, the cathode materials were obtained. A slurry was prepared by mixing cathode material, conductive carbon, and polyvinylidene fluoride (PVDF) in a ratio of 90:5:5, and the slurry was made into cathode sheets (the compaction density of the sheets was 3.3 g / cm2). Lithium metal sheets were selected as the anode material, and 2025 coin cells were assembled. The specific capacity and cycle retention of the materials were tested using 1M LiPF6 EC:DEC:DMC = 1:1:1 (V%) as the electrolyte. Table 1 shows the electrochemical performance test results of the six cathode materials.

[0057] Table 1. Electrochemical performance of cathode materials prepared in the examples and comparative examples.

[0058] Li content (ppm) 0.1C discharge capacity (mAh / g) 50 cycle retention rate Example 1 35 193.8 96.3％ Example 2 95 192.3 95.8 Example 3 60 192.9 97.1 Comparative Example 1 0 190.2 95.7％ Comparative Example 2 7 191.0 96.8％ Comparative Example 3 120 186.8 94.2％

Claims

1. A method for preparing a lithium-doped ternary cathode material precursor, characterized in that, Includes the following steps: S1: Prepare a raw material metal salt solution, an alkaline solution, a complexing agent solution, and a lithium source solution. The alkaline solution is a sodium hydroxide solution with a mass concentration of 20%–40%, and the complexing agent solution is an ammonia solution with a mass concentration of 20%–40%. Add the raw material metal salt solution, alkaline solution, ammonia solution, and lithium source solution to a reaction vessel for co-precipitation reaction. During the reaction, an inert protective gas is continuously introduced into the reaction vessel. The metal salt solution is an aqueous solution containing nickel salt, cobalt salt, manganese salt, or aluminum salt. The lithium source solution is a lithium hydroxide solution with a concentration of 0.5–2 mol / L. The molar ratio of lithium source solution to metal salt solution introduced into the reaction vessel per unit time is 0.1–2:

1. S2: When the particle size grows to the target particle size, stop feeding to obtain a solution containing precursor material. Then, age, wash, dry, sieve, and remove iron to obtain lithium-doped ternary cathode material precursor. The pH of the reaction system was controlled at 10.0–12.5, the ammonia value at 2–20 g / L, the temperature at 40–80℃, and the stirring speed at 100–1000 rpm. The chemical formula of the ternary cathode material precursor is Ni. x Co y X z (OH)2, wherein X is Mn or Al, 0 < x < 1, 0 < y < 1, x + y + z = 1; the lithium content in the ternary cathode material precursor is 20 to 100 ppm; the primary particles of the ternary cathode material precursor are nanosheets, and the thickness of the nanosheets is 200 to 300 nm.

2. The method for preparing a lithium-doped ternary cathode material precursor according to claim 1, characterized in that: When preparing the nickel-cobalt-manganese ternary precursor, the metal salt solution is an aqueous solution containing nickel, cobalt, and manganese salts, and the total concentration of metal ions in the metal salt solution is 1–2.5 mol / L; when preparing the nickel-cobalt-aluminum ternary precursor, the metal salt solution is a mixed salt solution prepared from nickel and cobalt salts and an aluminum salt solution, the total concentration of nickel and cobalt ions in the mixed salt solution is 1–2.5 mol / L, and the concentration of aluminum ions in the aluminum salt solution is 0.05–0.3 mol / L; the nickel, cobalt, manganese, and aluminum salts are at least one of sulfate, nitrate, and halide salts.

3. The method for preparing a lithium-doped ternary cathode material precursor according to claim 1, characterized in that: The particle size mentioned in step S2 is the particle size distribution D50 value, and the target particle size is 4 to 10 μm.

4. A ternary cathode material, characterized in that: The ternary cathode material is prepared from the ternary cathode material precursor prepared by the method for preparing a lithium-doped ternary cathode material precursor as described in claim 1.