CN114477312B - Method for preparing ternary positive electrode material precursor by layered doping - Google Patents

Abstract

The invention discloses a method for preparing a precursor of a ternary positive electrode material by layered doping. A metal salt solution, a precipitating agent solution, a complexing agent solution and a rubidium salt solution are added to the bottom liquid of a reaction kettle to carry out a co-precipitation reaction. When the particle size in the reactor grows to less than the target particle size of 0.5 ~ 3 μm, stop feeding, add deionized water, concentrate and replace the feed liquid containing rubidium ions in the reactor; then continue the co-precipitation reaction, and add molybdenum salt solution at the same time Carry out co-precipitation reaction until the average particle size grows to the target particle size, stop feeding, and obtain a solution containing precursor materials; stir the obtained solution containing precursor materials for aging, washing, drying, screening, and iron removal , to obtain the core-shell structure ternary cathode material precursor. The invention can prevent the generation of cracks in the nucleation process of the precursor of the ternary positive electrode material, improve the high-temperature cycle performance and rate performance of the ternary positive electrode material, and at the same time improve the conductivity and capacity retention rate of the lithium ion battery.

Description

A method for preparing a precursor of a ternary positive electrode material by layered doping

technical field

The invention relates to a ternary positive electrode material precursor, in particular to a method for preparing the ternary positive electrode material precursor by layered doping.

Background technique

The precursor of nickel-cobalt-manganese ternary cathode material is the most important raw material for the preparation of lithium-ion battery cathode materials. The main preparation method of the ternary precursor is to add nickel-cobalt-manganese metal salt solution, liquid caustic soda, and ammonia water into the reactor at the same time for co-precipitation reaction , due to the limitations of equipment and process conditions, microcracks are usually generated during the nucleation process of the co-precipitation reaction. In order to give full play to the excellent performance of the ternary cathode material, the preparation of its precursor is crucial to the production of the ternary cathode material, because the quality of the precursor (morphology, particle size, particle size distribution, specific surface area, impurity content, Tap density, etc.) directly determine the physical and chemical indicators of the final sintered product, resulting in the general electrical properties of the sintered ternary cathode material, poor cycle performance and specific capacity, in order to solve these defects, currently in the preparation process of the ternary precursor Most of them use the method of doping other metal elements or coating on the surface of the ternary precursor. Although doping or coating can improve the high-temperature cycle performance and rate performance of the ternary cathode material, the electrical conductivity of the lithium-ion battery prepared by it The rate and capacity retention rate are poor, which cannot meet the demand.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for preparing the precursor of the ternary positive electrode material by layered doping, to prevent cracks from being generated during the nucleation process of the precursor of the ternary positive electrode material, and to improve the high temperature cycle performance and rate of the ternary positive electrode material At the same time, it improves the conductivity and capacity retention of lithium-ion batteries.

The technical solution adopted by the present invention to solve the technical problem is: a method for preparing a ternary cathode material precursor by layered doping, comprising the following steps:

(1) Prepare metal salt solution, precipitant solution, complexing agent solution, rubidium salt solution and molybdenum salt solution;

(2) Add water, complexing agent solution, precipitating agent solution in reaction kettle, stir, constant temperature, prepare reaction kettle bottom liquid;

(3) Add metal salt solution, precipitant solution, complexing agent solution and rubidium salt solution to the reaction kettle bottom liquid, carry out co-precipitation reaction, when the particle size in the reaction kettle grows to be less than the target particle size of 0.5 ~ 3 μm, Suspend feeding, add deionized water, concentrate and replace the feed liquid containing rubidium ions in the reactor;

(4) Then continue to add metal salt solution, precipitant solution, complexing agent solution in reactor, add molybdenum salt solution simultaneously and carry out co-precipitation reaction, grow to target particle diameter to particle average particle diameter, stop feeding, must contain a solution of a precursor material;

(5) Stir the solution containing the precursor material obtained in step (4) to age, wash, dry, sieve, and remove iron to obtain a core-shell structure ternary cathode material precursor.

Further, the metal salt solution is an aqueous solution containing nickel salt, cobalt salt, and manganese salt, and the molar ratio of the nickel, cobalt, and manganese salts is 60-90:5-20:10-30, and the metal salt solution The total concentration of metal ions in the medium is 1-2 mol/L, and the nickel salt, cobalt salt, and manganese salt are at least one of sulfate, nitrate, and halogen salt.

Further, the precipitant solution is a sodium hydroxide solution with a concentration of 5-12mol/L, the complexing agent solution is an ammonia solution with a mass concentration of 12%-24%, and the rubidium salt solution in the rubidium salt solution is The ion concentration is 0.1-1mol/L, and the molybdenum ion concentration in the molybdenum salt solution is 0.1-1mol/L.

Further, in the step (3) and step (4), the reaction temperature is controlled to be 40-70° C., the pH value is 11.5-13, the ammonia concentration is 2-16 g/L, and the stirring speed is 300-600 rpm.

Further, the feed rate of the metal salt solution is 20 to 500 L/h, the feed rate ratio of the rubidium salt solution to the metal salt solution is 1:200 to 10000, and the feed rate ratio of the molybdenum salt solution to the metal salt solution It is 1:200～10000.

Further, the average particle size of the particles described in step (3) is the D50 value of the particle size distribution, and the target particle size is 3-13 μm.

Further, the molecular formula of the prepared ternary cathode material precursor is: Ni _x Co _y Mn _1-xy (OH) ₂ [Rb] _m [Mo] _n , m and n are doping amounts, where, 0.50≤x ≤0.90, 0.05≤y≤0.30, 0.05≤1-xy≤0.30, 0.0001≤m≤0.005, 0.0001≤n≤0.005.

Further, in step (3), the feed liquid containing rubidium ions in the reactor is replaced by concentration.

A ternary positive electrode material prepared by the above-mentioned method for preparing a precursor of a ternary positive electrode material by layered doping.

A lithium ion battery, comprising the above-mentioned ternary positive electrode material.

The beneficial effects of the present invention are: a method for preparing the precursor of the ternary positive electrode material by layered doping in the present invention, which prevents the generation of cracks during the nucleation process of the precursor of the ternary positive electrode material, and improves the high-temperature cycle performance and rate of the ternary positive electrode material At the same time, the conductivity and capacity retention of lithium-ion batteries are improved. The highest capacity of 100 cycles at 1C rate is 192.5mah/g, the highest conductivity is 9.7×10 ^-3 , and the highest capacity retention rate is 92.68% after 100 cycles.

Detailed ways

Below in conjunction with embodiment the present invention is further described.

Example 1:

Add pure water into the reaction kettle and heat it to 60°C, then adjust the pH of the prepared liquid alkali solution to 12.0, then add ammonia solution to adjust the bottom liquid to 4.5g/L, and the stirring blade inside the reaction kettle is set at 260r/min Run at a high speed to prepare the bottom solution for the co-precipitation reaction. Then add 1.98mol/L nickel-cobalt-manganese solution (the molar ratio of nickel-cobalt-manganese is 67:13:20) at a flow rate of 300L/h, add 32% liquid alkali solution at a flow rate of 185L/h, and add a flow rate of 30L/h Add 21% ammonia solution, and use a peristaltic pump to add 0.5mol/L rubidium salt solution at a flow rate of 100ml/min. During the reaction, the pH is reduced to 11.60 at a rate of 0.05/h and then maintained. The flow rate is 3000L/h for 7 hours before the reaction Nitrogen gas with a purity of 99.99% was fed in, and compressed air was fed in at a flow rate of 500 L/h after 8 hours. After 30 hours of co-precipitation reaction in the reactor, the particle size D50 grows to 3 μm, the feeding is suspended, deionized water is added, and the remaining rubidium ions are replaced by concentrating and clearing, and the feeding is continued after waiting for 2 hours. Change to molybdenum salt solution, the flow rate remains unchanged, stop feeding when the particle D50 value grows to 4μm, and the total reaction time is 75h. Washing impurities, filtering, dehydrating and drying the ternary positive electrode material precursor liquid to obtain a layered doped ternary positive electrode material precursor.

Example 2:

Add pure water to the reaction kettle and heat it to 60°C, then adjust the pH of the prepared liquid alkali solution to 11.95, then add ammonia solution to adjust the bottom liquid to 5g/L, and the stirring blade inside the reaction kettle is at a speed of 260r/min Run, and prepare the bottom liquid of co-precipitation reaction. Then add 1.98mol/L nickel-cobalt-manganese solution at a flow rate of 300L/h, add 32% liquid alkali solution at a flow rate of 185L/h, add 21% ammonia solution at a flow rate of 30L/h, use a peristaltic pump to Add a 0.5mol/L rubidium salt solution at a flow rate of 0.5 mol/L. During the reaction, the ph decreases to 11.60 at a rate of 0.05/h and then maintains it. Nitrogen gas with a purity of 99.99% is introduced at a flow rate of 3000 L/h for 6 hours before the reaction. The flow rate of 500L/h is fed into the compressed air. After 27 hours of co-precipitation reaction in the reactor, the particle size D50 grows to 3 μm, the feeding is suspended, deionized water is added, and the remaining rubidium ions are replaced by concentration and clearing. After waiting for 2 hours, continue feeding, and continue after 3 hours. Feed, change the rubidium salt solution to molybdenum salt solution, the flow rate remains unchanged, stop when the particle size continues to grow to 3.6-3.7μm, and the total reaction time is 68h. The ternary precursor slurry is washed with impurities, filtered, dehydrated and dried to obtain a layered doped ternary precursor.

Example 3:

Add pure water into the reaction kettle and heat it to 60°C, adjust the pH of the prepared liquid alkali solution to 11.55, then add ammonia solution to adjust the bottom liquid to 6.5g/L, and the stirring blades inside the reaction kettle run at a speed of 260r/min , to prepare the bottom liquid of co-precipitation reaction. Then add 1.98mol/L (ratio: 83:7:10) nickel-cobalt-manganese solution at a flow rate of 360L/h, add 32% liquid alkali solution at a flow rate of 135L/h, and add 21% Ammonia solution, use a peristaltic pump to add 0.5mol/L rubidium salt solution at a flow rate of 150ml/min. When reacting for 2 hours, the ph is reduced to 11.40 at a rate of 0.05/h and then maintained. During the reaction, 3000L/h of purity 99.99% Nitrogen protection. After 60 hours of co-precipitation reaction in the reactor, when the D50 value of the particles grows to 8 μm, the feeding is suspended, deionized water is added, and the remaining rubidium ions are replaced by concentration and clearing. After waiting for 2 hours, continue to feed, and the rubidium The salt solution was changed to 0.5mol/L molybdenum salt solution, the flow rate remained unchanged, and the feeding was stopped when the D50 value of the particles in the reactor grew to 10 μm, and the total reaction time was 80h. The ternary precursor slurry is washed with impurities, filtered, dehydrated and dried to obtain a layered doped ternary precursor.

Comparative example 1: (no doping rubidium molybdenum, other with embodiment 1)

Add pure water into the reaction kettle and heat it to 60°C, then adjust the pH of the prepared liquid alkali solution to 12.0, then add ammonia solution to adjust the bottom liquid to 4.5g/L, and stir the blades inside the reaction kettle at a speed of 260r/min Run at a high speed to prepare the bottom solution for the co-precipitation reaction. Then add 1.98mol/L nickel-cobalt-manganese solution at a flow rate of 300L/h, add 32% liquid alkali solution at a flow rate of 185L/h, add 21% ammonia solution at a flow rate of 30L/h, and during the reaction, the pH is 0.05 After the /h rate was reduced to 11.60, the nitrogen gas with a purity of 99.99% was fed at a flow rate of 3000 L/h for 7 hours before the reaction, and compressed air was fed with a flow rate of 500 L/h after 8 hours. After 98 hours of co-precipitation reaction in the reactor, stop when the particle size grows to 3.6um. The ternary precursor slurry is washed with impurities, filtered, dehydrated and dried to obtain a ternary precursor.

Comparative example 2: (other is the same as embodiment 1, does not carry out concentrated replacement)

Add pure water into the reaction kettle and heat it to 60°C, then adjust the pH of the prepared liquid alkali solution to 12.0, then add ammonia solution to adjust the bottom liquid to 4.5g/L, and the stirring blade inside the reaction kettle is set at 260r/min Run at a high speed to prepare the bottom solution for the co-precipitation reaction. Then add 1.98mol/L nickel-cobalt-manganese solution at a flow rate of 300L/h, add 32% liquid alkali solution at a flow rate of 185L/h, add 21% ammonia solution at a flow rate of 30L/h, use a peristaltic pump to Add a 0.5mol/L rubidium salt solution at a flow rate of 0.5 mol/L. During the reaction, the ph decreases to 11.60 at a rate of 0.05/h and then maintains it. Nitrogen gas with a purity of 99.99% is introduced at a flow rate of 3000 L/h for 7 hours before the reaction. The flow rate of 500L/h is fed into the compressed air. After 30 hours of co-precipitation reaction in the reactor, the particle size D50 grows to 3 μm, the rubidium salt solution is suspended, and the molybdenum salt solution is passed into the molybdenum salt solution at the same flow rate, and the feeding is stopped when the particle D50 value grows to 4 μm. The total reaction The duration is 75h. Washing impurities, filtering, dehydrating and drying the ternary positive electrode material precursor liquid to obtain a layered doped ternary positive electrode material precursor.

Comparative example 3: (other is the same as embodiment 1, doping rubidium, not doping molybdenum)

Add pure water into the reaction kettle and heat it to 60°C, then adjust the pH of the prepared liquid alkali solution to 12.0, then add ammonia solution to adjust the bottom liquid to 4.5g/L, and the stirring blade inside the reaction kettle is set at 260r/min Run at a high speed to prepare the bottom solution for the co-precipitation reaction. Then add 1.98mol/L nickel-cobalt-manganese solution at a flow rate of 300L/h, add 32% liquid alkali solution at a flow rate of 185L/h, add 21% ammonia solution at a flow rate of 30L/h, use a peristaltic pump to Add a 0.5mol/L rubidium salt solution at a flow rate of 0.5 mol/L. During the reaction, the ph decreases to 11.60 at a rate of 0.05/h and then maintains it. Nitrogen gas with a purity of 99.99% is introduced at a flow rate of 3000 L/h for 7 hours before the reaction. The flow rate of 500L/h is fed into the compressed air. Stop feeding when the particle D50 value grows to 4 μm, and the total reaction time is 75 hours. Washing impurities, filtering, dehydrating and drying the ternary positive electrode material precursor liquid to obtain a layered doped ternary positive electrode material precursor.

Comparative example 4: other is the same as embodiment 1, doping molybdenum, not doping rubidium)

Add pure water into the reaction kettle and heat it to 60°C, then adjust the pH of the prepared liquid alkali solution to 12.0, then add ammonia solution to adjust the bottom liquid to 4.5g/L, and the stirring blade inside the reaction kettle is set at 260r/min Run at a high speed to prepare the bottom solution for the co-precipitation reaction. Then add 1.98mol/L nickel-cobalt-manganese solution at a flow rate of 300L/h, add 32% liquid alkali solution at a flow rate of 185L/h, add 21% ammonia solution at a flow rate of 30L/h, use a peristaltic pump to Add 0.5 mol/L molybdenum salt solution at a flow rate of 0.5 mol/L. During the reaction, the ph is reduced to 11.60 at a rate of 0.05/h and then maintained. In the first 7 hours of the reaction, nitrogen gas with a purity of 99.99% is introduced at a flow rate of 3000 L/h. The flow rate of 500L/h is fed into the compressed air. Stop feeding when the particle D50 value grows to 4 μm, and the total reaction time is 75 hours. Washing impurities, filtering, dehydrating and drying the ternary positive electrode material precursor liquid to obtain a layered doped ternary positive electrode material precursor.

Electrochemical performance testing method:

1. After mixing the precursors and lithium hydroxide prepared in the examples and comparative examples uniformly according to the molar ratio M(Ni+Co+Mn):M(Li)=1:1.03, pre-calcine at 450°C for 4h , after being taken out and ground, calcined at 750°C for 20h, taken out and pulverized to finally obtain positive electrode materials, which are respectively denoted as A1, A2, A3, D1, D2, D3, and D4;

2. The obtained positive electrode material is made into a slurry according to the positive electrode material: conductive carbon: polyvinylidene fluoride (PVDF) = 90:5:5, and made into a positive electrode sheet (the compacted density of the electrode sheet is 3.3g/cm2) , choose metal lithium sheet as the negative electrode material, and assemble it into a 2025 button battery;

3. Using 1M LiPF6 EC:DEC:DMC=1:1:1 (V%) as the electrolyte, after 3 cycles of activation at 0.2C rate, cycle 100 times at 0.2C rate, and measure the Discharge capacity and discharge capacity at the 100th cycle, calculate the capacity retention rate of 100 cycles;

4. Use conductive silver glue to fix the four wires on the glass slide in turn, and evenly coat the positive electrode material of the lithium-ion battery in the form of slurry on the glass slide, and then vacuum-dry to obtain a film layer on the glass slide. The current I is measured by the ammeter, the voltage U is measured by the voltmeter, and then the conductivity σ of the positive electrode material of the lithium-ion battery is calculated according to the formula σ=IL/US.

The electrochemical properties of the positive electrode material obtained in table 1 embodiment and comparative examples

Claims (8)

1. The method for preparing the ternary cathode material precursor by layered doping is characterized by comprising the following steps of:

(1) Preparing a metal salt solution, a precipitator solution, a complexing agent solution, a rubidium salt solution and a molybdenum salt solution;

(2) Adding water, complexing agent solution and precipitant solution into a reaction kettle, stirring and keeping the temperature constant to prepare reaction kettle bottom solution;

(3) Adding a metal salt solution, a precipitator solution, a complexing agent solution and a rubidium salt solution into the bottom solution of the reaction kettle, performing coprecipitation reaction, suspending feeding when the particle size in the reaction kettle grows to be smaller than the target particle size of 0.5-3 mu m, adding deionized water, and concentrating and displacing feed liquid containing rubidium ions in the reaction kettle;

(4) Then continuously adding a metal salt solution, a precipitator solution and a complexing agent solution into the reaction kettle, simultaneously adding a molybdenum salt solution for coprecipitation reaction until the average particle size of particles grows to the target particle size, and stopping feeding to obtain a solution containing a precursor material;

(5) And (3) stirring the solution containing the precursor material obtained in the step (4) for ageing, washing, drying, screening and removing iron to obtain the ternary positive electrode material precursor with the core-shell structure.

2. The method for preparing a ternary cathode material precursor by layered doping according to claim 1, wherein the method comprises the following steps: the metal salt solution is an aqueous solution containing nickel salt, cobalt salt and manganese salt, the molar ratio of the nickel salt to the cobalt salt to the manganese salt is 60-90:5-20:10-30, the total concentration of metal ions in the metal salt solution is 1-2 mol/L, and the nickel salt, the cobalt salt and the manganese salt are at least one of sulfate, nitrate and halogen salt.

3. The method for preparing a ternary cathode material precursor by layered doping according to claim 1, wherein the method comprises the following steps: the precipitant solution is sodium hydroxide solution with the concentration of 5-12 mol/L, the complexing agent solution is ammonia water solution with the mass concentration of 12% -24%, the concentration of rubidium ions in the rubidium salt solution is 0.1-1 mol/L, and the concentration of molybdenum ions in the molybdenum salt solution is 0.1-1 mol/L.

4. The method for preparing a ternary cathode material precursor by layered doping according to claim 1, wherein the method comprises the following steps: in the step (3) and the step (4), the reaction temperature is controlled to be 40-70 ℃, the pH value is controlled to be 11.5-13, the ammonia concentration is controlled to be 2-16 g/L, and the stirring rotating speed is controlled to be 300-600 rpm.

5. The method for preparing a ternary cathode material precursor by layered doping according to claim 1, wherein the method comprises the following steps: the feeding amount of the metal salt solution is 20-500L/h, the feeding amount ratio of the rubidium salt solution to the metal salt solution is 1:200-10000, and the feeding amount ratio of the molybdenum salt solution to the metal salt solution is 1:200-10000.

6. The method for preparing a ternary cathode material precursor by layered doping according to claim 1, wherein the method comprises the following steps: the average particle diameter of the particles in the step (3) is the D50 value of the particle size distribution, and the target particle diameter is 3-13 mu m.

7. The method for preparing a ternary cathode material precursor by layered doping according to claim 1, wherein the method comprises the following steps: the molecular formula of the prepared ternary positive electrode material precursor is as follows: ni (Ni) _x Co _y Mn _1-x-y (OH) ₂ [Rb] _m [Mo] _n M and n are doping amounts, wherein x is more than or equal to 0.50 and less than or equal to 0.90, y is more than or equal to 0.05 and less than or equal to 0.30, 1-x-y is more than or equal to 0.05 and less than or equal to 0.30, m is more than or equal to 0.0001 and less than or equal to 0.005, and n is more than or equal to 0.0001 and less than or equal to 0.005.

8. The method for preparing a ternary cathode material precursor by layered doping according to claim 1, wherein the method comprises the following steps: in the step (3), the feed liquid containing rubidium ions in the reaction kettle is replaced by concentration.